248 research outputs found

    Spin and orbital magnetic moment of reconstructed √2 × √2R45º magnetite(001)

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    © 2015 American Physical Society. The surface of a magnetite single crystal with (001) orientation has been prepared by sputtering/annealing cycles providing the √2×2√2R45º reconstruction. The distribution of magnetic domains on the surface has been imaged by x-ray magnetic dichroism in a photoemission microscope. The easy axes are along the surface in-plane 110 directions. The near-surface magnetic moment was determined by applying the sum rules to XMCD spectra obtained with different kinetic energies of the secondary electrons. A reduced total moment of 3.3 μB and a ratio of about 0.10 between orbital and spin moment was found, which we attribute to the surface reconstruction.Peer Reviewe

    The late-Variscan peraluminous Valdepeñas pluton (southern Central Iberian Zone)

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    The Valdepeñas pluton is the easternmost outcrop of the Cáceres-Valdepeñas magmatic alignment (southern Central Iberian Zone). This massif is constituted by a cordierite-bearing porphyritic monzogranite and may be grouped within the so-called “Serie Mixta” granitoids. The Valdepeñas monzogranite is of magnesian [FeOt/(FeOt+MgO)~0.76], alkali-calcic [(Na2O+K2O)–CaO=7.8–8.5] and peraluminous (A/CNK=1.14–1.20). Multielemental- and REE-normalized patterns are comparable to those of similar rocks in the Nisa- Alburquerque-Los Pedroches magmatic alignment, and slightly differ from those of the Montes de Toledo batholith, both in the southern Central Iberian Zone. The U-Pb zircon age of 303±3Ma is consistent with the late-orogenic character of the intrusion and is in accordance with most of the granitic peraluminous intrusions in the southern Central Iberian Zone.  86Sr/87Sr300Ma ratios (0.707424–0.711253), εNd300Mavalues (-5.53 to -6.68) and whole-rock major and trace element compositions of the studied rocks, suggest that the parental magma of the Valdepeñas monzogranite could derive from a crustal metaigneous source. The U-Pb ages (552–650Ma) of inherited zircon cores found in Valdepeñas monzogranite samples match those often found in Lower Paleozoic metavolcanics and granitic orthogneisses of Central Iberia and, furthermore, point to Upper Neoproterozoic metaigneous basement rocks as possible protoliths at the magma source. Based on the solubility of monazite in peraluminous melts, the estimated emplacement temperature of the studied monzogranite is 742–762ºC. The results obtained in this work would contribute to a better understanding of the origin of the “Serie Mixta” granitoids

    Los paisajes de la región de Milmarcos: sistemática y cartografía (Cordillera Ibérica, Provincias de Guadalajara, Soria y Zaragoza)

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    Landforms constitute the physical framework of the landscape, whether it is considered in a territorial or in a visual approach. The composition, tectonic structure and geologic history of a territory determine the topographic development of the landscape and its textures. Here, we summarize the study o f the landscape's structure of a region o f 600 km2 located in the centre of the Iberian Peninsula, characterised by an alternance o f rock strata with different consistency and erosionability. The Mesozoic materials are folded and faulted because o f the alpine movements, and flattened to Neogene planation surfaces. The Cenozoic materials are in a horizontal disposal. During the Quaternary, the river system of the Mesa River was incised and developed. As a consequence of these circumstances, a wide variety of landforms is displayed. A typological classification o f the structures o f the landscapes of this region and their mapping has been made

    Self-organized single crystal mixed magnetite/cobalt ferrite films grown by infrared pulsed-laser deposition

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    We have grown mixed magnetite/cobalt ferrite epitaxial films on SrTiO3 by infrared pulsed-laser deposition. Diffraction experiments indicate epitaxial growth with a relaxed lattice spacing. The films are flat with two distinct island types: nanometric rectangular mounds in two perpendicular orientations, and larger square islands, attributed to the two main components of the film as determined by Mössbauer spectroscopy. The origin of the segregation is suggested to be the oxygen-deficiency during growth.Peer Reviewe

    Early socialization and environmental enrichment of lactating piglets affects the caecal microbiota and metabolomic response after weaning

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    The aim of this study was to determine the possible impact of early socialization and an enriched neonatal environment to improve adaptation of piglets to weaning. We hypothesized that changes in the microbiota colonization process and in their metabolic response and intestinal functionality could help the animals face weaning stress. A total of 48 sows and their litters were allotted into a control (CTR) or an enriched treatment (ENR), in which piglets from two adjacent pens were combined and enriched with toys. The pattern of caecal microbial colonization, the jejunal gene expression, the serum metabolome and the intestinal physiology of the piglets were assessed before (-2 d) and after weaning (+ 3d). A differential ordination of caecal microbiota was observed after weaning. Serum metabolome suggested a reduced energetic metabolism in ENR animals, as evidenced by shifts in triglycerides and fatty acids, VLDL/LDL and creatine regions. The TLR2 gene showed to be downregulated in the jejunum of ENR pigs after weaning. The integration of gene expression, metabolome and microbiota datasets confirmed that differences between barren and enriched neonatal environments were evident only after weaning. Our results suggest that improvements in adaptation to weaning could be mediated by a better response to the post-weaning stress.info:eu-repo/semantics/publishedVersio

    Mössbauer and Magnetic Properties of Coherently Mixed Magnetite-Cobalt Ferrite Grown by Infrared Pulsed-Laser Deposition

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    We have studied the magnetic properties and the composition of cobalt ferrite single crystal films on SrTiO3 : Nb grown by infrared pulsed-laser deposition. Mössbauer spectra have been recorded from both the target used to grow the films and the films themselves. The Mössbauer spectra of the target taken at low temperatures show a strong dependence of the recoil free fraction of the octahedral sites with temperature. The films composition, with a coexistence of Co-enriched cobalt ferrite and magnetite, has been estimated assuming a similar ratio of the recoil free fractions of the films. X-ray absorption and x-ray magnetic circular dichroism measurements confirm the valence composition of the film and show ferromagnetic Fe-Co coupling in the films with a coercive field around 0.5 T at room temperature. The combination of these characterization techniques allows establishing the coherent structural and magnetic properties of this biphase system.(MINECO) through Projects No. MAT2012 - 38045 - C04 - 01, CTQ2013 - 43086 - P, and MAT2013 - 48009 - C4 - 1 - P and by the EU - FP7 NANOPYME Project (No. 310516).Peer Reviewe

    Hemodynamic performance of different stent strategies for coronary bifurcations. Evaluation with a mathematical model

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    Purpose: Best percutaneous treatment strategy for lesions in coronary bifurcations is an ongoing subject of debate. There is limited data that analyses the effect of the different bifurcation strategies on coronary flow. Our aim is to evaluate the influence of different bifurcation stenting strategies on hemodynamic parameters, both in the main vessel (MV) and side branch (SB)

    Real space observation of the magnetic coupling between a Co film and a barium hexaferrite film

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    RIVA ONLINE 2021 – IBERIAN VACUUM ONLINE MEETING. The Iberian Vacuum Conference, (Reunión Ibérica de Vacío, RIVA) is a joint meeting of the Portuguese Vacuum Society (SOPORVAC) and the Spanish Vacuum Society (ASEVA), 2021 RIVA will take place ON-LINE from 4-6th October 2021. .-https://aseva.es/conferences/riva-online/Barium ferrite (BaFe12O19, BFO) is a hexagonal ferrite with applications as permanent magnet in many different devices due to its high magnetocrystalline anisotropy, high coercive field and low cost. However, the moderate saturation magnetization of BFO means that the energy product is orders of magnitude smaller than the one that rare-earth-based magnetic materials offer. To overcome this limitation, a commonly proposed strategy to enhance the energy product is exchange-coupling the magnetically hard component (BFO) with a soft phase in order to improve the combined remanent magnetization without a high loss in coercivity. Nonetheless, the results obtained in other hard/soft systems (SFO/Co bilayers) have pointed out the difficulty to take advantage of this rigid coupling magnetic regime1. In this research, we focus on two steps to investigate the Co/BFO coupling in a bilayer system: first, we sought to obtain BFO films with an in- plane magnetic easy axis to avoid shape anisotropy competition, and second, we deposit Co on top of such a BFO film while monitoring both the BFO and Co magnetic domains

    Obtaining cloud top height from WRF model vertical profiles: application to the EUSO program

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    The objective of the Extreme Universe Space Observatory (EUSO) program is detection and measurement of high-energy particles that reach earth?s atmosphere from space. Clouds at mid and upper levels of the troposphere can interfere with such detection. Therefore, determining cloud top height with high accuracy is crucial to estimating the effect of clouds on these measurements.With this aim, we developed a method to extract that height using cloud temperature via vertical profiles predicted by the WRF model
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