213 research outputs found
Short range structure of mechanically alloyed amorphous Ni2Zr investigated by anomalous X-ray scattering
No full textThe differential anomalous scattering technique has been used to study the local order in an amorphous Ni2Zr sample, prepared by mechanical alloying. The resulting structural parameters are compared with previous data obtained for a sample prepared by rapid quenching
Partial structure factors of amorphous Ni2Zr by anomalous X-ray scattering
No full textThe anomalous X-ray scattering technique has been employed to extract the partial structure factors for an amorphous Ni2Zr sample prepared by mechanical alloying. Four independent measurements were used to build a suitable system of equatuions where the differential structure factors were also introduced in order to reduce the ill-conditioning. A comparison of the short range atomic distribution with a rapidly quenched sample of similar composition investigated by different techniques is also reported
X-ray resonant magnetic scattering: application to thin films and multilayers
No full textThis paper reports on the use of a new technique to investigate the magnetic properties of thin films, multilayers and artificial structures, the X-ray resonant magnetic scattering at small values of the scattering vector. It can be used either by registering the reflectivity pattern or in a diffraction mode. In comparison with magneto-optical Kerr effect or neutron scattering, it offers an atomic selectivity due to the resonant excitation of a core electron, and even an electronic shell one. Examples are presented mainly in the soft X-range allowing to probe the 3d band of transition metals. They demonstrate the promising possibilities of the method to measure the magnetic moments carried by each of the atomic components in complex systems, as well as their distribution through thin layers, with an atomic resolution
Diffusion tensor imaging in early Alzheimer's disease.
No full textOur aim was to investigate the extent of white matter tissue damage in patients with early Alzheimer disease (AD) using diffusion tensor magnetic resonance imaging (DTI). Although AD pathology mainly affects cortical grey matter, previous magnetic resonance imaging (MRI) studies showed that changes also exist in the white matter (WM). However, the nature of AD-associated WM damage is still unclear. Conventional and DTI examinations (b=1000 s/mm2, 25 directions) were obtained from 12 patients with early AD (Mini Mental State Examination [MMSE] score=27, Grober and Buschke test score=33.2, digit span score=5.6) and 12 sex- and age-matched volunteers. The right and left mean diffusivity (MD) and fractional anisotropy (FA) of several WM regions were pooled in each patient and control, and compared between the two groups. Volumes of the whole brain and degree of atrophy of the temporal lobe were compared between the two groups. In AD, MD was increased in the splenium of the corpus callosum and in the WM in the frontal and parietal lobes. FA was bilaterally decreased in the WM of the temporal lobe, the frontal lobe and the splenium compared with corresponding regions in controls. Values in other areas (occipital area, superior temporal area, cingulum, internal capsule, and genu of the corpus callosum) were not different between patients and controls. No correlations were found between the MMSE score and the anisotropy indices. Findings of DTI reveal abnormalities in the frontal and temporal WM in early AD patients. These changes are compatible with early temporal-to-frontal disconnections
Influence of the electrode nano/microstructure on the electrochemical properties of graphite in aluminum batteries
No full textHerein we report on a detailed investigation of the irreversible capacity in the first cycle of pyrolytic graphite electrodes in aluminum batteries employing 1-ethyl-3-methylimidazolium chloride:aluminum trichloride (EMIMCl:AlCl3) as electrolyte. The reaction mechanism, involving the intercalation of AlCl4- in graphite, has been fully characterized by correlating the micro/nanostructural modification to the electrochemical performance. To achieve this aim a combination of X-ray diffraction (XRD), small angle X-ray scattering (SAXS) and computed tomography (CT) has been used. The reported results evidence that the irreversibility is caused by a very large decrease in the porosity, which consequently leads to microstructural changes resulting in the trapping of ions in the graphite. A powerful characterization methodology is established, which can also be applied more generally to carbon-based energy-related materials
A Direct Real-Time Observation of Anion Intercalation in Graphite Process and Its Fully Reversibility by SAXS/WAXS Techniques
No full textThe process of anion intercalation in graphite and its reversibility plays a crucial role in the next generation energy-storage devices. Herein the reaction mechanism of the aluminum graphite dual ion cell by operando X-ray scattering from small angles to wide angles is investigated. The staging behavior of the graphite intercalation compound (GIC) formation, its phase transitions, and its reversible process are observed for the first time by directly measuring the repeated intercalation distance, along with the microporosity of the cathode graphite. The investigation demonstrates complete reversibility of the electrochemical intercalation process, alongside nano- and micro-structural reorganization of natural graphite induced by intercalation. This work represents a new insight into thermodynamic aspects taking place during intermediate phase transitions in the GIC formation
A Direct Real‐Time Observation of Anion Intercalation in Graphite Process and Its Fully Reversibility by SAXS/WAXS Techniques
No full textThe process of anion intercalation in graphite and its reversibility plays a crucial role in the next generation energy-storage devices. Herein the reaction mechanism of the aluminum graphite dual ion cell by operando X-ray scattering from small angles to wide angles is investigated. The staging behavior of the graphite intercalation compound (GIC) formation, its phase transitions, and its reversible process are observed for the first time by directly measuring the repeated intercalation distance, along with the microporosity of the cathode graphite. The investigation demonstrates complete reversibility of the electrochemical intercalation process, alongside nano- and micro-structural reorganization of natural graphite induced by intercalation. This work represents a new insight into thermodynamic aspects taking place during intermediate phase transitions in the GIC formation
Ce 5d and Fe 3d magnetic profiles in CeH2/Fe multilayers probed by XRMS.
No full textThe element and electronic shell specificities of X-ray resonant magnetic scattering have been used to investigate the magnetization of Ce 5d and Fe 3d states in [CeH2(19.6 Angstrom) /Fe (25.4 Angstrom)] 38 a multilayer. We show that the measurement of the magnetic contribution to the intensities reflected at low angles at the Ce L-2 and Fe L-2,(3) edges allows us to investigate the profile of the Ce 5d and Fe 3d magnetic polarization. The Fe 3d polarization is found to be uniform across the Fe layer and the Ce 5d polarization appears to be restricted close to the interface with Fe
Direct Observation of the Xenon Physisorption Process in Mesopores by Combining In Situ Anomalous Small Angle X ray Scattering and X ray Absorption Spectroscopy
No full textThe morphology and structural changes of confined matter are still far from being understood. This report deals with the development of a novel in situ method based on the combination of anomalous small angle X ray scattering ASAXS and X ray absorption near edge structure XANES spectroscopy to directly probe the evolution of the xenon adsorbate phase in mesoporous silicon during gas adsorption at 165 K. The interface area and size evolution of the confined xenon phase were determined via ASAXS demonstrating that filling and emptying the pores follow two distinct mechanisms. The mass density of the confined xenon was found to decrease prior to pore emptying. XANES analyses showed that Xe exists in two different states when confined in mesopores. This combination of methods provides a smart new tool for the study of nanoconfined matter for catalysis, gas, and energy storage application
The cor solo:History and characteristics
No full textThe cor solo, a French version of the German Inventionshorn, enjoyed a period of popularity at the end of the eighteenth and in the first half of the nineteenth century. In its most common form it was pitched in 11-ft G with alternative tuning-slide crooks for F, E, E-flat and D. Thirty extant examples (by the Raoux family, Courtois, Jahn and Sax) have been studied and measured along with examples of the Inventionshorn for comparison. This paper presents an analysis of contemporary references to, and illustrations of, the cor solo, a comparative account of models produced by the Raoux family as the instrument’s principal makers, detailed bore comparisons, and players’ observations on the relative merits of the orchestral horn of the period with terminal crooks
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