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Oton J.,CSIC - National Center for Biotechnology | Sorzano C.O.S.,CSIC - National Center for Biotechnology | Marabini R.,Polytechnic University of Mozambique | Pereiro E.,ALBA Synchrotron Light Source | Carazo J.M.,CSIC - National Center for Biotechnology
Optics Express

Soft X-ray tomography (SXT) is becoming a powerful imaging technique to analyze eukaryotic whole cells close to their native state. Central to the analysis of the quality of SXT 3D reconstruction is the estimation of the spatial resolution and Depth of Field of the X-ray microscope. In turn, the characterization of the Modulation Transfer Function (MTF) of the optical system is key to calculate both parameters. Consequently, in this work we introduce a fully automated technique to accurately estimate the transfer function of such an optical system. Our proposal is based on the preprocessing of the experimental images to obtain an estimate of the input pattern, followed by the analysis in Fourier space of multiple orders of a Siemens Star test sample, extending in this way its measured frequency range. © 2015 Optical Society of America. Source

Ferrer S.,ALBA Synchrotron Light Source
Synchrotron Radiation News

ALBA is the Spanish synchrotron facility located in the area of Barcelona. It is a low-emittance, 3 GeV machine having, at present, seven state-of-the-art operating beamlines covering soft and hard X-rays. The hard X-ray beamlines comprise macromolecular crystallography, non-crystalline diffraction (SAXS and WAXS), high-resolution powder diffraction, and absorption spectroscopy. The soft X-ray beamlines include a photoemission beamline with two endstations—one devoted to photoelectron microscopy (PEEM) and the second to near ambient pressure photoemission (NAPP)—and another beamline devoted to XMCD and soft X-ray scattering. Both beamlines allow full control of the polarization of the beam, since they are equipped with helical undulators. An additional soft X-ray beamline, installed on a bending magnet port, is equipped with a full-field transmission X-ray microscope. Additional information may be found at http://www.albasynchrotron.es/en/beamlines. © , Copyright Taylor & Francis. Source

Stone K.H.,Lawrence Berkeley National Laboratory | Valvidares S.M.,ALBA Synchrotron Light Source | Kortright J.B.,Lawrence Berkeley National Laboratory
Physical Review B - Condensed Matter and Materials Physics

Resonant x-ray scattering is a powerful technique for the study of electronic structure at the nanoscale. In common practice, the optical properties of the constituent components of a material must be known prior to modeling of the scattered intensity. We present a means of refining electronic structure, in the form of optical properties, simultaneously with physical structure, in a Kramers-Kronig consistent manner. This approach constitutes a sensitive and powerful extension of resonant x-ray scattering to materials where the optical properties are not sufficiently well known. The application of this approach to specular reflectivity from a single crystal of SrTiO 3 is presented as an example case, wherein we find evidence for both a nonresonant surface contaminant layer and a modified SrTiO 3 surface region. Extrapolating from this study we comment on the potential utility of this approach to resonant scattering studies in general. © 2012 American Physical Society. Source

Eliseev A.A.,Moscow State University | Yashina L.V.,Moscow State University | Brzhezinskaya M.M.,ALBA Synchrotron Light Source | Brzhezinskaya M.M.,Saint Petersburg State University | And 10 more authors.

One-dimensional silver halide crystals were grown within single-walled nanotube (SWCNT) channels from the melt using a "molten media method". Atomic structures of the AgX@SWCNT hybrids were proposed based on high-resolution transmission electron microscopy images. It was found that AgCl intercalation results in amorphous filling of the SWCNT channels. 1D AgBr and AgI crystals intercalated into 1.34 nm SWCNTs possess the structure of a two-layer hcp of halogen atoms arranged laterally with respect to the SWCNT axis. Electronic properties and chemical bonding in AgX@SWNTs have been investigated by high-resolution X-ray photoelectron and near edge X-ray absorption fine structure spectroscopy (BESSY, Germany), optical absorption and Raman spectroscopy. Optical absorption spectroscopy indicates disappearance of E11 S transitions between van-Hove singularities, which is caused by an effective electron exchange between AgX and the SWCNT. C 1s X-ray absorption spectra indicate a new empty level (S1) induced by charge transfer. Multi-component structure of photoemission spectra can be explained both by the variation of the work function of AgX@SWCNT hybrids and local interactions between halogen ions and carbon atoms. Raman spectroscopy performed under electrochemical charging clearly and directly demonstrated the acceptor behavior of AgX with respect to SWCNTs. Based on a whole dataset, a self-consistent picture of the AgX-SWCNT interactions is derived. © 2010 Elsevier Ltd. All rights reserved. Source

Lopez-Periago A.,CSIC - Institute of Materials Science | Vallcorba O.,ALBA Synchrotron Light Source | Domingo C.,CSIC - Institute of Materials Science | Ayllon J.A.,Autonomous University of Barcelona
Crystal Growth and Design

An innovative crystallization process, based on the use of the ecofriendly supercritical carbon dioxide (scCO2) solvent, is presented for the production of coordination compound macrocrystals of general formula [Cu(hfacac)2(dPy)2], with intriguing prismatic hollow structures and single polymorphic forms. In contrast, conventional solvents yielded compact microstructures. The studied pyridine derivatives (dPy) were 4-phenylpyridine, PhPy; 4-benzylylpyridine, BzPy; and 4-acetylpyridine, AcPy. In the specific case of the [Cu(hfacac)2(AcPy)2] adduct, the use of scCO2 as a solvent allowed obtaining a pure polymorph, while the conventional solvent trials yielded a mixture of two polymorphs. Four new crystalline structures have been resolved from single crystal X-ray diffraction. All the structures consist of mononuclear complexes connected through intermolecular interactions, including H⋯;H, H⋯;O, F⋯;F, C-F⋯;Caromatic, and/or C-F⋯;π interactions, generating bi-dimensional networks that determine their crystallization mode in scCO2. © 2016 American Chemical Society. Source

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