The fatty acid binding protein FABP7 is required for optimal oligodendrocyte differentiation during myelination but not during remyelination.

The major constituents of the myelin sheath are lipids, which are made up of fatty acids (FAs). The hydrophilic environment inside the cells requires FAs to be bound to proteins, preventing their aggregation. Fatty acid binding proteins (FABPs) are one class of proteins known to bind FAs in a cell. Given the crucial role of FAs for myelin sheath formation we investigated the role of FABP7, the major isoform expressed in oligodendrocyte progenitor cells (OPCs), in developmental myelination and remyelination. Here, we show that the knockdown of Fabp7 resulted in a reduction of OPC differentiation in vitro. Consistent with this result, a delay in developmental myelination was observed in Fabp7 knockout animals. This delay was transient with full myelination being established before adulthood. FABP7 was dispensable for remyelination, as the knockout of Fapb7 did not alter remyelination efficiency in a focal demyelination model. In summary, while FABP7 is important in OPC differentiation in vitro, its function is not crucial for myelination and remyelination in vivo.This work was supported by grants from the UK Multiple Sclerosis Society, the Adelson Medical Research Foundation, the Japan Society for the Promotion of Science (JSPS) KAKENHI Grant and a core support grant from the Wellcome Trust and MRC to the Wellcome Trust-Medical Research Council Cambridge Stem Cell Institute. AGF was also supported by an ECTRIMS postdoctoral fellowship from July 2018. SF and TB were also supported by a Wellcome-Trust PhD studentship

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

© 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

Observation of a topologically protected state in a magnetic domain wall stabilized by a ferromagnetic chemical barrier

The precise control and stabilization of magnetic domain walls is key for the development of the next generation magnetic nano-devices. Among the multitude of magnetic configurations of a magnetic domain wall, topologically protected states are of particular interest due to their intrinsic stability. In this work, using XMCD-PEEM, we have observed a topologically protected magnetic domain wall in a ferromagnetic cylindrical nanowire. Its structure is stabilized by periodic sharp alterations of the chemical composition in the nanowire. The large stability of this topologically protected domain wall contrasts with the mobility of other non-protected and non-chiral states also present in the same nanowire. The micromagnetic simulations show the structure and the conditions required to find the topologically protected state. These results are relevant for the design of future spintronic devices such as domain wall based RF oscillators or magnetic memories

Tuning the N\'eel temperature in an antiferromagnet: the case of NixCo1-xO microstructures

We show that it is possible to tune the N\'eel temperature of nickel(II)-cobalt(II) oxide films by changing the Ni to Co ratio. We grow single crystalline micrometric triangular islands with tens of nanometers thickness on a Ru(0001) substrate using high temperature oxygen-assisted molecular beam epitaxy. Composition is controlled by adjusting the deposition rates of Co and Ni. The morphology, shape, crystal structure and composition are determined by low-energy electron microscopy and diffraction, and synchrotron-based x-ray absorption spectromicroscopy. The antiferromagnetic order is observed by x-ray magnetic linear dichroism. Antiferromagnetic domains up to micrometer width are observed

The Quantum as an Emergent System

Double slit interference is explained with the aid of what we call "21stcentury classical physics". We model a particle as an oscillator ("bouncer") in a thermal context, which is given by some assumed "zero-point" field of the vacuum. In this way, the quantum is understood as an emergent system, i.e., a steady-state system maintained by a constant throughput of (vacuum) energy. To account for the particle's thermal environment, we introduce a "path excitation field", which derives from the thermodynamics of the zero-point vacuum and which represents all possible paths a particle can take via thermal path fluctuations. The intensity distribution on a screen behind a double slit is calculated, as well as the corresponding trajectories and the probability density current. Further, particular features of the relative phase are shown to be responsible for nonlocal effects not only in ordinary quantum theory, but also in our classical approach.Comment: 24 pages, 2 figures, based on a talk given at "Emergent Quantum Mechanics (Heinz von Foerster Conference 2011)", http://www.univie.ac.at/hvf11/congress/EmerQuM.htm

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

Report of first recurrent glioma patients examined with PET-MRI prior to re-irradiation

Background and purpose The advantage of combined PET-MRI over sequential PET and MRI is the high spatial conformity and the absence of time delay between the examinations. The benefit of this technique for planning of re-irradiation (re-RT) treatment is unkown yet. Imaging data from a phase 1 trial of re-RT for recurrent glioma was analysed to assess whether planning target volumes and treatment margins in glioma re-RT can be adjusted by PET-MRI with rater independent PET based biological tumour volumes (BTVs). Patients and methods Combined PET-MRI with the tracer O-(2-F-18-fluoroethyl)-1-tyrosine (F-18-FET) prior to re-RT was performed in recurrent glioma patients in a phase I trial. GTVs including all regions suspicious of tumour on contrast enhanced MRI were delineated by three experienced radiation oncologists and included into MRI based consensus GTVs (mRGTVs). BTVs were semiautomatically delineated with a fixed threshold of 1.6 x background activity. Corresponding BTVs and mRGTVs were fused into union volume RET-NARGIVs. The Sorensen Dice coefficient and the conformity index were used to assess the geometric overlap of the BTVs with the mRGTVs. A recurrence pattern analysis was performed based on the original planning target volumes (PTVs = GTV + 10 mm margin or 5 mm in one case) and the RET-NARGTVs with margins of 10, 8, 5 and 3 mm. Results Seven recurrent glioma patients, who received PET-MRI prior to re-RT, were included into the present planning study. At the time of re-RT, patients were in median 54 years old and had a median Karnofsky Performance Status (KPS) score of 80. Median post-recurrence survival after the beginning of re-RT was 13 months. Concomitant bevacizumab therapy was applied in six patients and one patient received chemoradiation with temozolomide. Median GTV volumes of the three radiation oncologists were 35.0, 37.5 and 40.5 cubic centimeters (cc) and median (MR)GTV volume 41.8 cc. Median BTV volume was 36.6 cc and median (PET-MR)GTV volume 59.3 cc. The median Sorensen-Dice coefficient for the comparison between (MR)GTV and BTV was 0.61 and the median conformity index 0.44. Recurrence pattern analysis revealed two central, two in-field and one distant recurrence within both, the original PTV, as well as the (PER-MR)GTV with a reduced margin of 3 mm. Conclusion PET-MRI provides radiation treatment planning imaging with high spatial and timely conformity for high-grade glioma patients treated with re-RT with potential advancements for target volume delineation. Prospective randomised trials are warranted to further investigate the treatment benefits of PET-MRI based re-RT planning

Magnetic domains in SrFe12O19/Co hard/soft bilayers

ESRF (The european Synchrotron) User Meeting 2022, 7 - 9 February, 2022 . -- online meeting . -- https://www.esrf.fr/fr/home/events/conferences/2022/user-meeting-2022.html .-- Youtube access: https://www.youtube.com/playlist?list=PLsWatK2_NAmyYnkC-bXhvT70wsYaTmojqThe nature of the magnetic coupling between a SrFe12O19 particle (hard phase) and a Co layer grown on top (soft phase) has been studied by means of photoemission electron microscopy (PEEM) and spatially-resolved x-ray absorption (XAS) and magnetic circular dichroism (XMCD) at CIRCE, ALBA synchrotron (Spain). Our study reveals the soft metallic overlayer presents an in-plane magnetization despite the strong out-of-plane magnetocrystalline anisotropy of the hard platelet. Thus, the two phases show completely uncorrelated magnetic domain patterns. Micromagnetic simulations seem to indicate the degree of exchange-coupling is low or null, although the conditions for rigid coupling are a priori well met

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

Tuning the Néel temperature in an antiferromagnet: the case of NixCo1−xO microstructures

We show that it is possible to tune the Néel temperature of nickel(II)-cobalt(II) oxide films by changing the Ni to Co ratio. We grow single crystalline micrometric triangular islands with tens of nanometers thickness on a Ru(0001) substrate using high temperature oxygen-assisted molecular beam epitaxy. Composition is controlled by adjusting the deposition rates of Co and Ni. The morphology, shape, crystal structure and composition are determined by low-energy electron microscopy and diffraction, and synchrotron-based x-ray absorption spectromicroscopy. The antiferromagnetic order is observed by x-ray magnetic linear dichroism. Antiferromagnetic domains up to micrometer width are observedThis work is supported by the Spanish Agencia Estatal de Investigación (MCIU/AEI/FEDER, EU)) through Projects Nos MAT2015-64110-C2-1-P, MAT2015-64110-C2-2-P, RTI2018-095303-B-C51, and RTI2018-095303-B-C53, by the European Commission through Project H2020 No. 720853 (Amphibian) and by the Comunidad de Madrid through Project. NANOMAGCOST-CM P2018/NMT-4321. These experiments were performed at the CIRCE beamline of the ALBA Synchrotron Light Facility. A.M. acknowledges funding via a CSIC-Alba agreemen