Crossed-ratchet effects and domain wall geometrical pinning

The motion of a domain wall in a two dimensional medium is studied taking into account the internal elastic degrees of freedom of the wall and geometrical pinning produced both by holes and sample boundaries. This study is used to analyze the geometrical conditions needed for optimizing crossed ratchet effects in periodic rectangular arrays of asymmetric holes, recently observed experimentally in patterned ferromagnetic films. Geometrical calculations and numerical simulations have been used to obtain the anisotropic critical fields for depinning flat and kinked walls in rectangular arrays of triangles. The aim is to show with a generic elastic model for interfaces how to build a rectifier able to display crossed ratchet effects or effective potential landscapes for controlling the motion of interfaces or invasion fronts.Comment: 13 pages, 18 figure

Spanish Research Report for 1991

10 páginas, 14 tablasPeer reviewe

Magnetic order of Cr thin films in Nb/Cr/Fe-nanoisland hybrid: a comparative study between magnetic and superconducting properties

Shifted hysteresis loops characteristic of the exchange bias effect between a ferromagnet and an antiferromagnet are demonstrated in structures formed by a 2.5 nm Cr layer deposited on top of an array of Fe nanoislands (Cr/Fe-nanoislands). This effect evidences the persistence of antiferromagnetic (AF) order for Cr layers much thinner than the thickness reported in the literature. The field shift measured is found to increase for the smallest island sizes, which can be related with the enhancement of the Fe-nanoisland surface to volume ratio. The comparative study between superconducting proximity effects in Nb/Cr/Fe-nanoislands and Nb/normal metal/Fe-nanoisland hybrids (where the normal metals used are Al and Pt) confirms the presence of AF order in the 2.5 nm Cr spacer layer. A much shorter penetration depth of the Cooper pairs into the AF Cr layers than in the normal metal Pt and Al spacer layers is deduced

A gemini cationic lipid with histidine residues as a novel lipid-based gene nanocarrier: a biophysical and biochemical study

This work reports the synthesis of a novel gemini cationic lipid that incorporates two histidine-type head groups (C3(C16His)2). Mixed with a helper lipid 1,2-dioleoyl-sn-glycero3-phosphatidyl ethanol amine (DOPE), it was used to transfect three different types of plasmid DNA: one encoding the green fluorescence protein (pEGFP-C3), one encoding a luciferase (pCMV-Luc), and a therapeutic anti-tumoral agent encoding interleukin-12 (pCMV-IL12). Complementary biophysical experiments (zeta potential, gel electrophoresis, small-angle X-ray scattering (SAXS), and fluorescence anisotropy) and biological studies (FACS, luminometry, and cytotoxicity) of these C3(C16His)2/DOPE-pDNA lipoplexes provided vast insight into their outcomes as gene carriers. They were found to efficiently compact and protect pDNA against DNase I degradation by forming nanoaggregates of 120–290 nm in size, which were further characterized as very fluidic lamellar structures based in a sandwich-type phase, with alternating layers of mixed lipids and an aqueous monolayer where the pDNA and counterions are located. The optimum formulations of these nanoaggregates were able to transfect the pDNAs into COS-7 and HeLa cells with high cell viability, comparable or superior to that of the standard Lipo2000*. The vast amount of information collected from the in vitro studies points to this histidine-based lipid nanocarrier as a potentially interesting candidate for future in vivo studies investigating specific gene therapies

Osteonecrosis de los maxilares: Documento de consenso

Nuestro objetivo ha sido elaborar un documento de posición sobre el riesgo de desarrollar una osteonecrosis de maxilares (ONM) en los pacientes que reciben bifosfonatos para el tratamiento de la osteoporosis, identificando y valorando el grado de evidencia que apoyan las recomendaciones. Para ello se revisaron los estudios publicados sobre la definición, epidemiología, fisiopatología, clínica, diagnóstico y tratamiento de la ONM, elaborándose tras su análisis las presentes recomendaciones. Éstas se efectuaron tras un proceso pre-especificado y reproducible, que incluyó un modelo aceptado para la evaluación y la cita de la evidencia que las apoyaban. El documento, una vez elaborado por los coordinadores, fue revisado y discutido por todos los miembros del panel, elaborándose las recomendaciones provisionales que finalmente fueron estudiadas y aprobadas por los expertos de las sociedades médicas relacionadas con el metabolismo mineral óseo, que se muestran en el Anexo 2

Depth resolved lattice-charge coupling in epitaxial BiFeO3 thin film

For epitaxial films, a critical thickness (t(c)) can create a phenomenological interface between a strained bottom layer and a relaxed top layer. Here, we present an experimental report of how the t(c) in BiFeO3 thin films acts as a boundary to determine the crystalline phase, ferroelectricity, and piezoelectricity in 60 nm thick BiFeO3/SrRuO3/SrTiO3 substrate. We found larger Fe cation displacement of the relaxed layer than that of strained layer. In the time-resolved X-ray microdiffraction analyses, the piezoelectric response of the BiFeO3 film was resolved into a strained layer with an extremely low piezoelectric coefficient of 2.4 pm/V and a relaxed layer with a piezoelectric coefficient of 32 pm/V. The difference in the Fe displacements between the strained and relaxed layers is in good agreement with the differences in the piezoelectric coefficient due to the electromechanical couplingope

Performance of local orbital basis sets in the self-consistent Sternheimer method for dielectric matrices of extended systems

We present a systematic study of the performance of numerical pseudo-atomic orbital basis sets in the calculation of dielectric matrices of extended systems using the self-consistent Sternheimer approach of [F. Giustino et al., Phys. Rev. B 81 (11), 115105 (2010)]. In order to cover a range of systems, from more insulating to more metallic character, we discuss results for the three semiconductors diamond, silicon, and germanium. Dielectric matrices calculated using our method fall within 1-3% of reference planewaves calculations, demonstrating that this method is promising. We find that polarization orbitals are critical for achieving good agreement with planewaves calculations, and that only a few additional \zeta 's are required for obtaining converged results, provided the split norm is properly optimized. Our present work establishes the validity of local orbital basis sets and the self-consistent Sternheimer approach for the calculation of dielectric matrices in extended systems, and prepares the ground for future studies of electronic excitations using these methods.Comment: 10 pages, 8 figure