195 research outputs found
Cerebrospinal fluid leak during stapes surgery: Gushing leaks and oozing leaks, two different phenomena.
Cerebrospinal fluid (CSF) leak is an uncommon event that can occur during stapes surgery. Such leaks can be classified as gushing leaks (stapes gushers) and oozing leaks. A stapes gusher is a massive flow of CSF through the perforated footplate that fills the middle ear suddenly, while an oozing leak is a slower and less profuse flow. We conducted a retrospective, observational, multicenter study of 38 patients—23 men and 15 women, aged 23 to 71 years (mean: 47)—who had experienced a CSF leak during stapes surgery. Patients were divided into various groups according to the type of surgical procedure performed and the type of postoperative complications they experienced. Audiometric and clinical evaluations were carried out pre- and postoperatively. Correlations among surgical variations (total or partial stapedectomy, placement of a prosthesis), hearing outcomes, and the incidence of postoperative complications (postoperative CSF leak and vertigo) were studied. Our statistical analysis revealed that gushing leaks and oozing leaks result in different degrees of hearing impairment and different rates of complications. We recommend that an individual approach be used to manage these complications
Automatic Positional Accuracy Assessment of Imagery Segmentation Processes: A Case Study
There are many studies related to Imagery Segmentation (IS) in the field of Geographic Information (GI). However, none of them address the assessment of IS results from a positional perspective. In a field in which the positional aspect is critical, it seems reasonable to think that the quality associated with this aspect must be controlled. This paper presents an automatic positional accuracy assessment (PAA) method for assessing this quality component of the regions obtained by means of the application of a textural segmentation algorithm to a Very High Resolution (VHR) aerial image. This method is based on the comparison between the ideal segmentation and the computed segmentation by counting their differences. Therefore, it has the same conceptual principles as the automatic procedures used in the evaluation of the GI's positional accuracy. As in any PAA method, there are two key aspects related to the sample that were addressed: (i) its size-specifically, its influence on the uncertainty of the estimated accuracy values-and (ii) its categorization. Although the results obtained must be taken with caution, they made it clear that automatic PAA procedures, which are mainly applied to carry out the positional quality assessment of cartography, are valid for assessing the positional accuracy reached using other types of processes. Such is the case of the IS process presented in this study
Fate assessment of commercial 2D MoS2 aqueous dispersions at physicochemical and toxicological level
The physicochemical properties and the toxicological potential of commercially available MoS2 nanoparticles with different lateral size and degradation stage were studied in the present research work. To achieve this, the structure and stoichiometry of fresh and old aqueous suspensions of micro-MoS2 and nano-MoS2 was analyzed by Raman, while x-ray photoelectron spectroscopy allowed to identify more quantitatively the nature of the formed oxidized species. A, the toxicological impact of the nanomaterials under analysis was studied using adenocarcinomic human alveolar basal epithelial cells (A549 cells) and the unicellular fungus S. cerevisiae as biological models. Cell viability assays and reactive oxygen species (ROS) determinations demonstrated different toxicity levels depending on the cellular model used and in function of the degradation state of the selected commercial nanoproducts. Both MoS2 nanoparticle types induced sublethal damage on the A549 cells though the increase of intracellular ROS levels, while comparable concentrations reduced the viability of yeast cells. In addition, the old MoS2 nanoparticles suspensions exhibited a higher toxicity for both human and yeast cells than the fresh ones. Our findings demonstrate that the fate assessment of nanomaterials is a critical aspect to increase the understanding on their characteristics and on their potential impact on biological systems along their life cycle
Magnetic domains on magnetite islands: from XMCD-PEEM to micromagnetism
Oral presentation given at the 13th European Conference on Surface Crystallography and Dynamics, held in Donostia-San Sebastián, Spain, on June 19-21th, 2017.Magnetite nanostructures and thin films have been grown in spintronic devices such as spin valves in order to take advantage of the high Curie temperature, stability, and predicted half-metal character. However, thin films present magnetic properties which are rather different from the properties of bulk magnetite: high coercive fields, high saturation fields, out-of-plane magnetization, superparamagnetism in ultrathin films, or unexpected easy-axes. An explanation for these effects are growth defects, among which antiphase domain boundaries (APBs) are the best example. In the present work, we study the magnetic domains on flat single-crystal magnetite and other mixed spinels grown on Ru(0001) by molecular beam epitaxy [1,2]. As each island grows from a single nucleus, there are expected to be free of APBs. We have measured with nanometer-resolution the 3D magnetization of the islands by combining x-ray magnetic circular dichroism images acquired in a photoemission electron microscope at different azimuthal angles. The 3D magnetization maps have been used as the initial magnetization configuration for micromagnetic simulations of islands with the same lateral and vertical dimensions as the experimental ones. The Mumax3 software has been used to perform the micromagnetic simulations. By comparing the evolution of the micromagnetic simulations with the experimental behavior of the islands after annealing, we seek to validate the material parameters that define their magnetic behavior and to identify cases where defects or other effects play a role
Mössbauer and Magnetic Properties of Coherently Mixed Magnetite-Cobalt Ferrite Grown by Infrared Pulsed-Laser Deposition
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
Self-organized single crystal mixed magnetite/cobalt ferrite films grown by infrared pulsed-laser deposition
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
Real space observation of the magnetic coupling between a Co film and a barium hexaferrite film
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
Insights onto the magnetic coupling at hexaferrite-based hard/soft bilayer systems
IBERTRIVA 2019 X Iberian Conference on Tribology – IBERTRIB, XI Iberian Vacuum Conference - RIVA, Seville, Spain,June 26-28Magnets are used in a variety of applications, such as generators, magnetic recording media,
components in RF and microwave devices. However, many of these magnets contain s rare
earths, critical elements whose extraction is environmentally harmful and that present price
volatility risks. Their replacement by cheaper and more environmentally friendly materials is
therefore sought.
In our case, we have focused on magnetically hard strontium hexaferrite (SrFe 12O19, SFO) as
the base for alternative permanent magnets (Figure 1a). The atomic arrangement of this ferrite
results in a high magnetocrystalline anisotropy and a coercive field, however, its magnetization
is moderate (1). It is well known that the coupling between a magnetically hard and soft material
improved magnetization while avoiding a high cost in coercitivity loss (2). However, results have
been disappointing so far as structural and geometrical limitations make it extremely challenging
to fabricate. In this work, we aim at further understanding the magnetic coupling at hard -soft
interfaces involving ferrites, for which we have deposited soft iron and cobalt metals on top of
SrFe12O19 thin films with controlled easy-axis of magnetization.
SFO thin films have been obtained by RF magnetron sputtering at 260W followed by a
subsequent annealing in air of 850ºC. Their structure and composition was characterized by
Raman spectroscospy (Figure 1b), Mössbauer spectroscopy, X-ray photoemission
spectroscopy and low-energy electron microscopy (LEEM). We have grown the magnetically
soft layer by molecular-beam epitaxy and we have analyzed the resulting bilayer system
through photoemission electron microscopy, LEEM and vibrating-sample magnetometry.
References
[1] R.C. Pullar, Hexagonal ferrites: a review of the synthesis, properties and applications of hexaferrite ceramics, Progress in Materials Science 57 (2012), pp 1191¿1334.
[2] Eric E. Fullerton, J. S. Jiang, M. Grimsditch, C. H. Sowers, and S. D. Bader, Exchange-spring behavior in epitaxial hard/soft magnetic bilayers, Phys. Rev. B 58 (1998) 1219
Informe de la asistencia bucodental en el servicio de odontología de la villa paralímpica durante los IX Juegos Paralímpicos de Barcelona '92
Durante los Juegos Paralímpicos se dispuso de un servicio de Odontología para atender cualquier problema urgente bucodental que se les pudiera presentar a los integrantes de la 'familia paralímpica'. Se hace hincapié en los motivos por los que acudieron al servicio y se quiere llamar la atención sobre el mal estado bucodental de los deportistas
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]
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