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1.
J Synchrotron Radiat ; 19(Pt 6): 1001-5, 2012 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-23093761

RESUMEN

Eiger is the next-generation single-photon-counting pixel detector following the widely used Pilatus detector. Its smaller pixel size of 75 µm × 75 µm, higher frame rate of up to 22 kHz, and practically zero dead-time (~4 µs) between exposures will further various measurement methods at synchrotron sources. In this article Eiger's suitability for X-ray photon correlation spectroscopy (XPCS) is demonstrated. By exploiting its high frame rate, complementary small-angle X-ray scattering (SAXS) and XPCS data are collected in parallel to determine both the structure factor and collective diffusion coefficient of a nano-colloid suspension. For the first time, correlation times on the submillisecond time scale are accessible with a large-area pixel detector.

2.
Phys Rev Lett ; 108(19): 197201, 2012 May 11.
Artículo en Inglés | MEDLINE | ID: mdl-23003079

RESUMEN

Using neutron reflectometry and resonant x-ray techniques we studied the magnetic proximity effect (MPE) in superlattices composed of superconducting YBa2Cu3O7 and ferromagnetic-metallic La0.67Ca0.33MnO3 or ferromagnetic-insulating LaMnO(3+δ). We find that the MPE strongly depends on the electronic state of the manganite layers, being pronounced for the ferromagnetic-metallic La0.67Ca0.33MnO3 and almost absent for ferromagnetic-insulating LaMnO(3+δ). We also detail the change of the magnetic depth profile due to the MPE and provide evidence for its intrinsic nature.

3.
Opt Express ; 16(25): 20522-9, 2008 Dec 08.
Artículo en Inglés | MEDLINE | ID: mdl-19065191

RESUMEN

We develop a novel method for structure determination of confined fluids using diffraction-grating-based x-ray interferometry.Within this approach, diffraction from a microfluidic array, which acts both as confinement and transmission diffraction grating, provides the reference wave, whereas the density modulations of the confined fluid, acting as a weak phase object, generate the object wave. The ensemble-averaged density profile of the fluid perpendicular to the confining channel is then unambiguously obtained from the interference between the reference and object waves by direct Fourier inversion.


Asunto(s)
Mezclas Complejas/química , Diseño Asistido por Computadora , Interferometría/instrumentación , Microfluídica/instrumentación , Modelos Teóricos , Refractometría/instrumentación , Difracción de Rayos X/instrumentación , Simulación por Computador , Diseño de Equipo , Análisis de Falla de Equipo , Luz , Dispersión de Radiación
4.
Phys Rev Lett ; 101(13): 136103, 2008 Sep 26.
Artículo en Inglés | MEDLINE | ID: mdl-18851466

RESUMEN

Using x-ray diffraction from microfluidic channel arrays, we have determined concentration profiles of charge-stabilized silica colloids (radius 60+/-2 nm) confined between two like-charged dielectric walls at a few hundred nanometer distance. In solutions of very low ionic strength, strongly repulsive Coulomb interactions drive the colloids toward the central region between the walls. The addition of a small quantity of salt ions (0.2 mM) causes a dense colloidal monolayer to be trapped near the walls.

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