Room temperature ferromagnetic-like behavior in Mn-implanted and post-annealed InAs layers deposited by Molecular Beam Epitaxy

We report on the magnetic and structural properties of Ar and Mn implanted InAs epitaxial films grown on GaAs (100) by Molecular Beam Epitaxy (MBE) and the effect of Rapid Thermal Annealing (RTA) for 30 seconds at 750C. Channeling Particle Induced X- ray Emission (PIXE) experiments reveal that after Mn implantation almost all Mn atoms are subsbtitutional in the In-site of the InAs lattice, like in a diluted magnetic semiconductor (DMS). All of these samples show diamagnetic behavior. But, after RTA treatment the Mn-InAs films exhibit room-temperature magnetism. According to PIXE measurements the Mn atoms are no longer substitutional. When the same set of experiments were performed with As as implantation ion all of the layers present diamagnetism without exception. This indicates that the appearance of room-temperature ferromagnetic-like behavior in the Mn-InAs-RTA layer is not related to lattice disorder produce during implantation, but to a Mn reaction produced after a short thermal treatment. X-ray diffraction patterns (XRD) and Rutherford Back Scattering (RBS) measurements evidence the segregation of an oxygen deficient-MnO2 phase (nominally MnO1.94) in the Mn-InAs-RTA epitaxial layers which might be on the origin of room temperature ferromagnetic-like response observed.Comment: 16 pages, 5 figures. Acepted in J. Appl. Phy

Hypoxic Cell Waves around Necrotic Cores in Glioblastoma: A Biomathematical Model and its Therapeutic Implications

Glioblastoma is a rapidly evolving high-grade astrocytoma that is distinguished pathologically from lower grade gliomas by the presence of necrosis and microvascular hiperplasia. Necrotic areas are typically surrounded by hypercellular regions known as "pseudopalisades" originated by local tumor vessel occlusions that induce collective cellular migration events. This leads to the formation of waves of tumor cells actively migrating away from central hypoxia. We present a mathematical model that incorporates the interplay among two tumor cell phenotypes, a necrotic core and the oxygen distribution. Our simulations reveal the formation of a traveling wave of tumor cells that reproduces the observed histologic patterns of pseudopalisades. Additional simulations of the model equations show that preventing the collapse of tumor microvessels leads to slower glioma invasion, a fact that might be exploited for therapeutic purposes.Comment: 29 pages, 9 figure

Preocupaciones y propuestas educativas del profesor Horacio Capel

El profesor Horacio Capel siempre ha tenido una especial sensibilidad hacia la enseñanza de la geografía en la educación básica. Las investigaciones de Capel y su equipo sobre la geografía como disciplina escolar han constituido una aportación relevante para la reforma del currículum y para la renovación de la didáctica. En ese sentido, son destacables los estudios históricos sobre la institucionalización de la geografía como saber académico, los análisis de los paradigmas geográficos y la revisión del estado de la enseñanza de la geografía en diversos países

Interaction Effects on the Magneto-optical Response of Magnetoplasmonic Dimers

The effect that dipole-dipole interactions have on the magneto-optical (MO) properties of magnetoplasmonic dimers is theoretically studied. The specific plasmonic versus magnetoplasmonic nature of the dimer's metallic components and their specific location within the dimer plays a crucial role on the determination of these properties. We find that it is possible to generate an induced MO activity in a purely plasmonic component, even larger than that of the MO one, therefore dominating the overall MO spectral dependence of the system. Adequate stacking of these components may allow obtaining, for specific spectral regions, larger MO activities in systems with reduced amount of MO metal and therefore with lower optical losses. Theoretical results are contrasted and confirmed with experiments for selected structures

Generation of rotationally dominated galaxies by mergers of pressure-supported progenitors

Through the analysis of a set of numerical simulations of major mergers between initially non-rotating, pressure supported progenitor galaxies with a range of central mass concentrations, we have shown that: (1) it is possible to generate elliptical-like galaxies, with v/sigma > 1 outside one effective radius, as a result of the conversion of orbital- into internal-angular momentum; (2) the outer regions acquire part of the angular momentum first; (3) both the baryonic and the dark matter components of the remnant galaxy acquire part of the angular momentum, the relative fractions depend on the initial concentration of the merging galaxies. For this conversion to occur the initial baryonic component must be sufficiently dense and/or the encounter should take place on a orbit with high angular momentum. Systems with these hybrid properties have been recently observed through a combination of stellar absorption lines and planetary nebulae for kinematic studies of early-type galaxies. Our results are in qualitative agreement with such observations and demonstrate that even mergers composed of non-rotating, pressure-supported progenitor galaxies can produce early-type galaxies with significant rotation at large radii.Comment: 5 pages, 6 figures, 2 tables. Accepted for publication in A&A Letter

Computational thinking and robotics in education

After the computational thinking sessions in the previous 2016-2018 editions of TEEM Conference, the fourth edition of this track has been organized in the current 2019 edition. Computational thinking is still a very significant topic, especially, but not only, in pre-university education. In this edition, the robotic has a special role in the track, with a strength relationship with the STEM and STEAM education of children at the pre-university levels, seeding the future of our society

Diversidades geográficas y construcción de un saber crítico para participar e red. La experiencia del Geoforo Iberoamericano. Balance inicial

La diversidad de pueblos, culturas y situaciones sociales en países de Iberoamérica no impide el diálogo crítico y honesto en torno a la investigació n que se realiza sobre el aprendizaje de los problemas del mundo. A este reto puede contribuir la Geografía como ciencia, pero necesita, entonces, abandonar los obstáculos intelectuales, corporativos y académicos que dificultan su estudio por parte de los alumnos. En este trabajo damos cuenta de las iniciativas llevadas a cabo por un grupo de profesores a través del Geoforo, que aprovecha las facilidades del ciberespacio, a partir del portal Geocrítica de la Universidad de Barcelona

New Higgs couplings at e^+ e^- and hadronic colliders

We examine the potentiality of both CERN LEP and Fermilab Tevatron colliders to establish bounds on new couplings involving the bosonic sector of the standard model. We pay particular attention to the anomalous Higgs interactions with $\gamma$, $W^{\pm}$ and $Z^0$. A combined exclusion plot for the coefficients of different anomalous operators is presented. The sensitivity that can be achieved at the Next Linear Collider and at the upgraded Tevatron is briefly discussed