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Gif-sur-Yvette, France

Tavares P.F.,MAX Laboratory | Nagaoka R.,SOLEIL | Gunzel T.F.,CELLS
IPAC 2011 - 2nd International Particle Accelerator Conference | Year: 2011

We present calculations of collective instability effects in the 3 GeV electron storage ring of the MAX IV facility currently under construction in Lund, Sweden. The storage ring is designed to deliver ultra-low emittance down to 0.24 nm rad so as to provide high brightness synchrotron radiation from undulators. This is achieved in a comparatively small machine (528 m circumference) through the use of a multi-bend achromat lattice and a compact magnet design with multi-purpose narrow gap magnet blocks. This design features small dispersion leading to low momentum compaction, which, together with the small circular (11 mm radius) chambers, poses a challenge to reach the design current (500 mA in 176 bunches) without exciting instabilities and degrading beam parameters due to the interaction with the machine impedance. Particularly important are multi-bunch resistive wall effects in the NEG coated copper chamber as well single-bunch instabilities driven by the broadband impedance. A low RF frequency (100 MHz) and harmonic cavities are foreseen to lengthen the bunches and increase instability thresholds. Copyright © 2011 by IPAC'11/EPS-AG. Source

Bahout M.,CNRS Chemistry Institute of Rennes | Tonus F.,CNRS Chemistry Institute of Rennes | Prestipino C.,CNRS Chemistry Institute of Rennes | Pelloquin D.,National Engineering School of Caen | And 3 more authors.
Journal of Materials Chemistry | Year: 2012

The structural and redox stability of the n = 1 Ruddlesden-Popper (RP) oxide Pr 0.5Sr 1.5Cr 0.5Mn 0.5O 4-δ, synthesized by the citrate-gel method, has been investigated over the temperature range 25-700 °C under reducing (5% H 2 flow) and oxidizing (O 2 or air flow) conditions by means of in situ neutron powder diffraction (NPD) and X-ray absorption near-edge structure spectroscopy (XANES). Sequential Rietveld refinement of the NPD patterns collected under hydrogen revealed de-intercalation of oxide ions from the equatorial anion positions with retention of I4/mmm symmetry. The reduction from Pr 0.5Sr 1.5Cr 0.5Mn 0.5O 4.00(2) to Pr 0.5Sr 1.5Cr 0.5Mn 0.5O 3.81(2) is accompanied by an expansion of both the a and c lattice parameters. When the reduced sample is heated in air, oxygen refills the equatorial sites and the unit cell contracts; the interlayer interstitial site remains unoccupied. XANES showed the oxidation states in the as-prepared composition to be Pr 3+, Cr 3+ and Mn 4+. When the material is heated under dilute hydrogen, the oxidation states Pr 3+ and Cr 3+ are retained whereas Mn 4+ is reduced to Mn 3+. These observations constitute the first direct evidence that the d-block element, and not praseodymium, is responsible for the electrocatalytic activity of Pr-containing RP oxides. When the reduced material is heated under oxygen, Mn 3+ is reoxidised to Mn 4+ and a low concentration of tetrahedrally-coordinated Cr(vi) forms, suggesting a possible poisoning mechanism in fuel-cell applications. © The Royal Society of Chemistry 2012. Source

Chwiej J.,AGH University of Science and Technology | Dulinska J.,AGH University of Science and Technology | Janeczko K.,Jagiellonian University | Dumas P.,SOLEIL | And 3 more authors.
Journal of Chemical Neuroanatomy | Year: 2010

In the present work, synchrotron radiation Fourier transform infrared (SRFTIR) micro-spectroscopy and imaging were used for topographic and semi-quantitative biochemical analysis of rat brain tissue in cases of pilocarpine-induced epilepsy. The tissue samples were analyzed with a beam defined by small apertures and spatial resolution steps of 10μm which allowed us to probe the selected cellular layers of hippocampal formation. Raster scanning of the samples has generated 2D chemical cartographies revealing the distribution of proteins, lipids and nucleic acids. Spectral analysis has shown changes in the saturation level of phospholipids and relative secondary structure of proteins. Special interest was put in the analysis of two areas of the hippocampal formation (sector 3 of the Ammon's horn, CA3 and dentate gyrus, DG) in which elemental abnormalities were observed during our previous studies. Statistically significant increase in the saturation level of phospholipids (increased ratio of the absorption intensities at around 2921 and 2958cm-1) as well as conformational changes of proteins (β-type structure discrepancies as shown by the increased ratio of the absorbance intensities at around 1631 and 1657cm-1 as well as the ratio of the absorbance at 1548 and 1657cm-1) were detected in pyramidal cells of CA3 area as well as in the multiform and molecular layers of DG. The findings presented here suggest that abnormalities in the protein secondary structure and increases in the level of phospholipid saturation could be involved in mechanisms of neurodegenerative changes following the oxidative stress evoked in brain areas affected by pilocarpine-induced seizures. © 2010 Elsevier B.V. Source

Martinez A.,Complutense University of Madrid | Romero J.J.,Institute Ceramica y Vidrio CSIC C Kelsen | Bartolome F.,University of Zaragoza | Garcia L.M.,University of Zaragoza | And 3 more authors.
Applied Physics Letters | Year: 2012

The room temperature changes of the magnetic behavior under pressure of an invar alloy of nominal composition (Fe 0.5Cu 0.5) 87Zr 13 (at. ) has been studied by K-edge x-ray magnetic circular dichroism (XMCD) and x-ray absorption near edge spectroscopy (XANES). The Curie temperature, as determined from low field magnetization measurements, is (255 ± 15)K. However XMCD shows a non negligible signal above this temperature. In addition, the XMCD signal decreases upon increasing pressure indicating a pressure-induced collapse of the magnetic moment. These results evidence the itinerant character of FeCuZr alloys as well as the occurrence of magnetovolume effects characterized by a strong dependence of the 3d band on the Fe-Fe nearest neighbor distances. © 2012 American Institute of Physics. Source

Rankovic M.L.,University of Belgrade | Giuliani A.,SOLEIL | Giuliani A.,French National Institute for Agricultural Research | Milosavljevic A.R.,University of Belgrade | Milosavljevic A.R.,University of Notre Dame
Applied Physics Letters | Year: 2016

We have performed inner-shell electron impact action spectroscopy of mass and charge selected macromolecular ions. For this purpose, we have coupled a focusing electron gun with a linear quadrupole ion trap mass spectrometer. This experiment represents a proof of principle that an energy-tunable electron beam can be used in combination with radio frequency traps as an activation method in tandem mass spectrometry (MS2) and allows performing action spectroscopy. Electron impact MS2 spectra of multiply protonated ubiquitin protein ion have been recorded at incident electron energies around the carbon 1 s excitation. Both MS2 and single ionization energy dependence spectra are compared with literature data obtained using the soft X-ray activation conditions. © 2016 AIP Publishing LLC. Source

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