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]

Oral Anticoagulation and Risk of Symptomatic Hemorrhagic Transformation in Stroke Patients Treated With Mechanical Thrombectomy: Data From the Nordictus Registry

Introduction: We aimed to evaluate if prior oral anticoagulation (OAC) and its type determines a greater risk of symptomatic hemorrhagic transformation in patients with acute ischemic stroke (AIS) subjected to mechanical thrombectomy. Materials and Methods: Consecutive patients with AIS included in the prospective reperfusion registry NORDICTUS, a network of tertiary stroke centers in Northern Spain, from January 2017 to December 2019 were included. Prior use of oral anticoagulants, baseline variables, and international normalized ratio (INR) on admission were recorded. Symptomatic intracranial hemorrhage (sICH) was the primary outcome measure. Secondary outcome was the relation between INR and sICH, and we evaluated mortality and functional outcome at 3 months by modified Rankin scale. We compared patients with and without previous OAC and also considered the type of oral anticoagulants. Results: About 1.455 AIS patients were included, of whom 274 (19%) were on OAC, 193 (70%) on vitamin K antagonists (VKA), and 81 (30%) on direct oral anticoagulants (DOACs). Anticoagulated patients were older and had more comorbidities. Eighty-one (5.6%) developed sICH, which was more frequent in the VKA group, but not in DOAC group. OAC with VKA emerged as a predictor of sICH in a multivariate regression model (OR, 1.89 [95% CI, 1.01–3.51], p = 0.04) and was not related to INR level on admission. Prior VKA use was not associated with worse outcome in the multivariate regression model nor with mortality at 3 months. Conclusions: OAC with VKA, but not with DOACs, was an independent predictor of sICH after mechanical thrombectomy. This excess risk was associated neither with INR value by the time thrombectomy was performed, nor with a worse functional outcome or mortality at 3 months

Dyslipidemias and stroke prevention: recommendations of the Study Group of Cerebrovascular Diseases of the Spanish Society of Neurology

Objetivo: Actualizar las recomendaciones de la Sociedad Española de Neurología para la prevención del ictus, tanto primaria como secundaria, en pacientes con dislipidemia. Desarrollo: Se ha realizado una revisión sistemática en Pubmed evaluando los principales aspectos relacionados con el manejo de las dislipidemias en la prevención primaria y secundaria del ictus, elaborándose una serie de recomendaciones relacionadas con los mismos. Conclusiones: En prevención primaria se recomienda determinar el riesgo vascular del paciente con el fin de definir los objetivos de LDLc. En prevención secundaria tras un ictus de origen aterotrombótico se recomienda un objetivo de LDLc < 55 mg/dl, mientras que en ictus isquémicos de origen no aterotrombótico, dado que su relación con dislipidemias es incierta, se establecerán los objetivos en función del grupo de riesgo vascular de cada paciente. Tanto en prevención primaria como secundaria las estatinas son los fármacos de primera elección, pudiendo asociarse ezetimiba y/o inhibidores de PCSK9 en aquellos casos que no alcancen los objetivos terapéuticosObjective We present an update of the Spanish Society of Neurology's recommendations for prevention of both primary and secondary stroke in patients with dyslipidaemia. Development We performed a systematic review to evaluate the main aspects of the management of dyslipidaemias in primary and secondary stroke prevention and establish a series of recommendations. Conclusions In primary prevention, the patient's vascular risk should be determined in order to define target values for low-density lipoprotein cholesterol. In secondary prevention after an atherothrombotic stroke, a target value < 55 mg/dL is recommended; in non-atherothombotic ischaemic strokes, given the unclear relationship with dyslipidaemia, target value should be established according to the vascular risk group of each patient. In both primary and secondary prevention, statins are the drugs of first choice, and ezetimibe and/or PCSK9 inhibitors may be added in patients not achieving the target valu

Nanosecond infrared pulsed laser deposition of cobalt ferrite thin films on Si (100) substrates.

2018 E-MRS Spring Meeting. June 19 – 21, 0f 2018, at the Convention Centre of Strasbourg (France). .-https://www.european-mrs.com/meetings/2018-spring/exhibitionCobalt ferrite has attracted interest in various fields such as high-temperature superconductivity, spintronics, microelectronics and magnetic applications. Cobalt ferrite is a mixed iron (III) and cobalt (II) oxide with a spinel-related structure. Our work is focused on understanding the growth of cobalt ferrite thin films on Si (100) by pulsed laser deposition (PLD). The study is aimed at investigating the influence that deposition parameters such as substrate temperature, target-substrate distance or oxygen partial pressure have on the physicochemical properties of the obtained films and, in particular, in cation oxidation states, cation distribution and crystal quality

Mössbauer studies on nanosecond infrared pulsed laser deposition of cobalt ferrite thin films on Si(100) substrates

MECAME 2018.The Conference will take place from 27 to 31 May, 2018 at Kolovare Hotel, Zadar, Croatia.in honour of Professor Frank Berry (University of Birmingham, UK). .-https://mecame2018.irb.hr

Synthesis of smooth amorphous thin films of silicon carbide with controlled properties through pulsed laser deposition

10 pags., 5 figs., 1 tab.Thin films of silicon carbide (SiC) on Si (100) and SrTiO (100) substrates have been grown by nanosecond pulsed laser deposition (PLD) with a Q-switched Nd:YAG laser operating at the wavelengths of 1064, 532 and 266 nm. The deposits obtained consisted of smooth and uniform layers of amorphous SiC, free of holes and cracks, with thicknesses in the range of 30–100 nm and average roughness substantially lower than 1 nm. The role of laser wavelength and of substrate temperature (300 K vs. 1025 K) on morphology, crystallinity and composition of the deposits was assessed. The films were analyzed by X-ray diffraction, micro-Raman spectroscopy and X-ray photoelectron spectroscopy. In addition, optical emission spectroscopy was employed to evaluate the characteristics of the ablation plasma and its correlation with the film growth.This research was supported by the Spanish State Research Agency (AEI) and European Regional Development (FEDER) through Projects PID2019-106125GB-I00/AEI/0.13039/501100011033 and PID2019-104124RB-I00/AEI/0.13039/501100011033. Thanks are given to the Soft and Polymeric Matter group (IEM-CSIC) for the use of AFM. We are grateful to M. Furió from MNCN-CSIC and P. Gonzalez from ICTP-CSIC for Raman and X-ray difraction technical assistance, respectively. Funding Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature

LiM0.5Mn1.5O4-δ (M = Co or Fe) spinels with a high oxidation state obtained by ultrasound-assisted thermal decomposition of nitrates. Characterization and physicochemical properties

8 pags., 7 figs., 3 tabs.Manganese lithium oxides with spinel-related structure, LiCoMnO and LiFeMnO, have been synthesized for the first time using an ultrasound-assisted thermal decomposition of nitrates (UA-TDN) synthesis method. The materials were studied by X-ray powder diffraction, scanning and transmission electron microscopy, oxygen stoichiometry determinations, Raman and X-ray photoelectron spectroscopy. The Rietveld refinement of the X-ray diffraction data indicated that the samples crystallize in the Fd3‾m space group which is characteristic of the cubic spinel structure and have a cell parameter of 0.8117 ​nm (LiCoMnO) and 0.8254 ​nm (LiFeMnO). The Scherrer method and the Williamson-Hall (W–H) method were used to evaluate the crystallite sizes. Energy-dispersive X-ray spectroscopy analyses confirmed that the metals were present in the expected stoichiometry. Scanning and transmission electron microscopy images showed that the particles are of an irregular polyhedral shape, having average sizes of 600 and 750 ​nm for the Co- and Fe-containing materials, respectively. X-ray photoelectron spectroscopy measurements revealed the presence of metal cations in high oxidation states: Co, Fe, Mn and Mn. Considering the ensemble of the results obtained, it is possible to propose the following ionic distributions Li[Co Mn Mn ]O and Li[Fe Mn Mn ]O .This work was financially supported by CONICYT Chile (DA thanks FONDECYT grant 3180042). JE and JLG thanks DICYT (051831EM_DASproject). JFM thanks the support from the Spanish Ministerio de Ciencia,Innovacion y Universidades, under the Project RTI2018-095303-B-C51.AP acknowledge to FONDECYT grant 11171045. FCB acknowledge to FONDEQUIP EQM130170 from Instituto de Química, Campus Curauma,PUCV. LT acknowledge to FONDECYT grant 11170068. JE acknowledgeto Basal Project FB0807