19 research outputs found
Imaging Spin Reorientation Transitions in Consecutive Atomic Co layers
By means of spin-polarized low-energy electron microscopy (SPLEEM) we show
that the magnetic easy-axis of one to three atomic-layer thick cobalt films on
ruthenium crystals changes its orientation twice during deposition:
one-monolayer and three-monolayer thick films are magnetized in-plane, while
two-monolayer films are magnetized out-of-plane, with a Curie temperature well
above room temperature. Fully-relativistic calculations based on the Screened
Korringa-Kohn-Rostoker (SKKR) method demonstrate that only for two-monolayer
cobalt films the interplay between strain, surface and interface effects leads
to perpendicular magnetization.Comment: 5 pages, 4 figures. Presented at the 2005 ECOSS conference in Berlin,
and at the 2005 Fall meeting of the MRS. Accepted for publication at Phys.
Rev. Lett., after minor change
Hydrogen-induced reversible spin-reorientation transition and magnetic stripe domain phase in bilayer Co on Ru(0001)
Imaging the change in the magnetization vector in real time by spin-polarized
low-energy electron microscopy, we observed a hydrogen-induced, reversible
spin-reorientation transition in a cobalt bilayer on Ru(0001). Initially,
hydrogen sorption reduces the size of out-of-plane magnetic domains and leads
to the formation of a magnetic stripe domain pattern, which can be understood
as a consequence of reducing the out-of-plane magnetic anisotropy. Further
hydrogen sorption induces a transition to an in-plane easy-axis. Desorbing the
hydrogen by heating the film to 400 K recovers the original out-of-plane
magnetization. By means of ab-initio calculations we determine that the origin
of the transition is the local effect of the hybridization of the hydrogen
orbital and the orbitals of the Co atoms bonded to the absorbed hydrogen.Comment: 5 figure
Probing proton halo effects in the 8B+64Zn collision around the Coulomb barrier
Proton halo effects in the 8B+64Zn reaction at an energy around 1.5 times the Coulomb barrier have been studied at HIE-ISOLDE CERN using, for the first time, the only existing postaccelerated 8B beam. This, together with the use of a high granularity and large solid angle detection system, allowed for a careful mapping of the elastic angular distribution, especially in the Coulomb-nuclear interference region. Contrary to what is observed for the one-neutron halo nucleus 11Be on the same target in a similar energy range, the analysis of the elastic scattering angular distribution shows only a modest suppression of the Coulomb-nuclear interference peak, with no remarkable enhancement of the total reaction cross-section. Inclusive angular and energy distributions of 7Be produced in direct reaction processes have also been measured. The comparison of these data with the results of theoretical calculations for the elastic and non-elastic breakup contributions indicate that both processes are important. Overall, the experimental data suggest a 8B collision dynamics at the barrier very different from the one of neutron halo nuclei, showing only modest effects of coupling to continuum. This behaviour can be interpreted as due to the presence of the additional Coulomb interactions halo-core and halo-target together with the presence of the centrifugal barrier felt by the valence proton of 8B.UE ENSAR2 Subvención nº 654002Istituto Nazionale di Fisica Nucleare (INFN) Italia, Science and Technology Facilities Council (STFC) Reino Unido y la Agencia Española de Financiación “ELEGANT” PGC2018-095640-B-100, FIS2017-88410-P, PDI2019- 104390GB-100, FPA2016-77689-C2-1-R, PGC2018-096994-B-C21, PGC2018-096994-B-C22 y RTI2018-098868-B-I0
Strontium hexaferrite platelets: a comprehensive soft X-ray absorption and Mössbauer spectroscopy study
IBERMÖSS-2019, Bilbao, 30-31 may 2019. --https://www.ehu.eus/es/web/ibermossmeetingStrontium ferrite (SFO, SrFe12O19) is a ferrite
employed for permanent magnets due to its high
magnetocrystalline anisotropy. Since its discovery
in the mid-20th century, this hexagonal ferrite has
become an increasingly important material both
commercially and technologically, finding a variety
of uses and applications. Its structure can be
considered a sequence of alternating spinel (S) and
rocksalt (R) blocks. All the iron cations are in the
Fe3+ oxidation state and it has a ferrimagnetic
configuration with five different cationic
environments for the iron (three octahedral sites, a
tetraedrical site and a bipiramidal site)[1,2].
We have studied the properties of SrFe 12O19 in the
shape of platelets, up to several micrometers in
width, and tens of nanometers thick, synthesized by
a hydrothermal method. We have characterized the
structural and magnetic properties of these platelets
by Mössbauer spectroscopy, x-ray transmission
microscopy (TMX), transmission electron
microscopy (TEM), x-ray diffraction (XRD),
vibrating-sample magnetometry (VSM), x-ray
absorption spectroscopy (XAS), x-ray circular
magnetic dichroism (XMCD) and photoemission
electron microscopy (PEEM). To the best of our
knowledge this is the first time that the x-ray
absorption spectra at the Fe L 2,3 edges of this
material in its pure form have been reported. The
Mössbauer results recorded from these platelets
both in the electron detection and transmission
modes have helped to understand the iron magnetic
moments determined by XMCD (Fig.1). The
experimental results have been complemented with
multiplet calculations aimed at reproducing the
observed XAS and XMCD spectra at the Fe L 2,3
absorption edge, and by density functional theory
(DFT) calculations to reproduce the oxygen K-
absorption edge. Finally the domain pattern
measured in remanence is in good agreement with
micromagnetic simulations [3]
Coinage-metal capping effects on the spin-reorientations of Co/Ru(0001)
Thin films of Co/Ru(0001) are known to exhibit an unusual spin reorientation
transition (SRT) coupled to the completion of Co atomic layers for Co
thicknesses under 4 layers. By means of spin-polarized low-energy electron
microscopy, we follow in real space the magnetization orientation during the
growth of atomically thick capping layers on Co/Ru(0001). Capping with
coinage-metal (Cu, Ag, Au) elements modifies the SRT depending on the Co and
overlayer thickness and on the overlayer material, resulting in an expanded
range of structures with high perpendicular magnetic anisotropy. The origin of
the SRT can be explained in terms of ab-initio calculations of the
layer-resolved contributions to the magnetic anisotropy energy. Besides the
changes in the SRT introduced by the capping, a quantitative enhancement of the
magnetic anisotropy is identified. A detailed analysis of the interplay between
strain and purely electronic effects allows us to identify the conditions that
lead to a high perpendicular magnetic anisotropy in thin hcp Co films.Comment: 25 pages, 10 figures. Corrected several typos, added a reference. The
experimental and theory discussion has been rewritten in places for improved
readability. The experimental observations are summarized in a table instead
of a figur
Visualization and analysis of cellular & Twitter data using qgis
The study is to understand individual presence and movement in Friuli Venezia Giulia region. It is important for tourism planning, hazard management, business marketing, implementing government lifetime policies and benefit. The aim of this study is achieved by advanced web 2.0 applications. We need real time and geo-located data to monitor the inflow of tourist and to come up with effective promoting and benefiting plans for tourism, the evacuation and mitigation strategies during hazards to protect social life and environment with less infrastructure damage, marketing plans for advertising or selling of products. Despite wide spread success in predicting specific aspects of human behavior by social media information, a little attention is given to twitter and cell phone data. Accessibility to detailed human movements with fine spatial and temporal granularity is challenging due to confidentiality and safety reasons. With rapid development of web2.0 applications people can post about events, share opinion and emotions online. Using twitter data, how short term travelers, such as tourists, can be recognized and how their travel pattern can be analyzed. Study of finding tourist dynamics such as arriving and outgoing of tourist, sum of trips, sum of days and night spent, number of unique visitors, country of residence, main destination, secondary destination, transits pass through, repeat visits are achieved using CDR (call detail records) and DDR (data detail records)
IL-6 serum levels predict severity and response to tocilizumab in COVID-19: An observational study
Background: Patients with coronavirus disaese 2019 (COVID-19) can develop a cytokine release syndrome that eventually leads to acute respiratory distress syndrome requiring invasive mechanical ventilation (IMV). Because IL-6 is a relevant cytokine in acute respiratory distress syndrome, the blockade of its receptor with tocilizumab (TCZ) could reduce mortality and/or morbidity in severe COVID-19. Objective: We sought to determine whether baseline IL-6 serum levels can predict the need for IMV and the response to TCZ. Methods: A retrospective observational study was performed in hospitalized patients diagnosed with COVID-19. Clinical information and laboratory findings, including IL-6 levels, were collected approximately 3 and 9 days after admission to be matched with preadministration and postadministration of TCZ. Multivariable logistic and linear regressions and survival analysis were performed depending on outcomes: need for IMV, evolution of arterial oxygen tension/fraction of inspired oxygen ratio, or mortality. Results: One hundred forty-six patients were studied, predominantly males (66%); median age was 63 years. Forty-four patients (30%) required IMV, and 58 patients (40%) received treatment with TCZ. IL-6 levels greater than 30 pg/mL was the best predictor for IMV (odds ratio, 7.1; P < .001). Early administration of TCZ was associated with improvement in oxygenation (arterial oxygen tension/fraction of inspired oxygen ratio) in patients with high IL-6 (P = .048). Patients with high IL-6 not treated with TCZ showed high mortality (hazard ratio, 4.6; P = .003), as well as those with low IL-6 treated with TCZ (hazard ratio, 3.6; P = .016). No relevant serious adverse events were observed in TCZ-treated patients. Conclusions: Baseline IL-6 greater than 30 pg/mL predicts IMV requirement in patients with COVID-19 and contributes to establish an adequate indication for TCZ administrationThis study was funded by Spanish Ministry of Economy, Industry and Competitiveness (MINECO) and Instituto de Salud Carlos III (grant nos. RD16/0011/0012 and PI18/ 0371 to I.G.A., grant no. PI19/00549 to A.A., and grant no. SAF2017-82886-R to
F.S.-M.) and co-funded by the European Regional Development Fund. The study was also funded by ‘‘La Caixa Banking Foundation’’ (grant no. HR17-00016 to F.S.-M.) and ‘‘Fondos Supera COVID19’’ by Banco de Santander and CRUE. None
of these sponsors have had any role in study design; in the collection, analysis, and interpretation of data; in the writing of the report; and in the decision to submit the article for publicatio
Revista de educación inclusiva
Resumen basado en el de la publicaciónTítulo, resumen y palabras clave en español y en inglésSe recoge la experiencia docente con un grupo de
estudiantes de primero de grado de Educación Social de la Universidad
de Barcelona en el marco de la asignatura Identidad y Desarrollo
Profesional. Tanto el propio contenido de la asignatura, como la
heterogénea composición del grupo, propiciaron un recorrido particular
del que pueden extraerse algunos elementos medulares para la
construcción de un vínculo educativo que posibilite no sólo el aprendizaje,
sino también la construcción de una identidad propia.ES
Order-disorder phase transition on the (100) surface of magnetite
et al.Using low-energy electron diffraction, we show that the room-temperature (2×2)R45â̂̃ reconstruction of Fe3O4(100) reversibly disorders at ∼450â̂̃C. Short-range order persists above the transition, suggesting that the transition is second order and Ising-like. We interpret the transition in terms of a model in which subsurface Fe3+ is replaced by Fe2+ as the temperature is raised. This model reproduces the structure of antiphase boundaries previously observed with scanning tunneling microscopy, as well as the continuous nature of the transition. To account for the observed transition temperature, the energy cost of each charge rearrangement is 82 meV. © 2013 American Physical Society.This research was supported by the Office of Basic Energy Sciences, Division of Materials and Engineering Sciences, U. S. Department of Energy under Contract No. DE-AC04-94AL85000 and by the goverment of Spain through Project No. MAT2009-14578-C03-01/03 and MAT2012-38045-C04-01/04. LV and IB thanks the Spanish CSIC for support through a JAE-Doc contract.Peer Reviewe