Ferrodistortive instability at the (001) surface of half-metallic manganites

We present the structure of the fully relaxed (001) surface of the half-metallic manganite La0.7Sr0.3MnO3, calculated using density functional theory within the generalized gradient approximation (GGA). Two relevant ferroelastic order parameters are identified and characterized: The tilting of the oxygen octahedra, which is present in the bulk phase, oscillates and decreases towards the surface, and an additional ferrodistortive Mn off-centering, triggered by the surface, decays monotonically into the bulk. The narrow d-like energy band that is characteristic of unrelaxed manganite surfaces is shifted down in energy by these structural distortions, retaining its uppermost layer localization. The magnitude of the zero-temperature magnetization is unchanged from its bulk value, but the effective spin-spin interactions are reduced at the surface.Comment: 4 pages, 2 figure

Supervisión de la práctica psicoterapéutica. Una reflexión en torno al desempeño profesional

El presente documento tuvo por objetivo dar cuenta de cómo fue la práctica en un grupo de supervisión de la intervención terapéutica, mediante un grupo de acompañamiento entre pares desde el Enfoque Centrado en la Persona. Se le llamó grupo de supervisión a un espacio destinado al acompañamiento profesional de la reflexión respecto al estilo personal de acompañar al otro, bien sea desde el marco de la facilitación del potencial personal -propuestas del enfoque Humanista-, o bajo el marco de la psicoterapia que considera las aportaciones de este. Los integrantes del grupo de supervisión tuvimos en común la formación humanista-existencial, y algunos miembros, egresados de la Maestría en Desarrollo Humano del Instituto Tecnológico de Estudios Superiores de Occidente (ITESO). El presente Reporte de Experiencia Profesional da cuenta del desempeño en este grupo de supervisión, mismo que se vincula con las propuestas del enfoque humanista-existencial, y en particular, de la psicoterapia Centrada en la Persona de Carl, Rogers.ITESO, A. C

ZINC-FINGER interactions mediate transcriptional regulation of hypocotyl growth in Arabidopsis

Integration of environmental signals and interactions among photoreceptors and transcriptional regulators is key in shaping plant development. TANDEM ZINC-FINGER PLUS3 (TZP) is an integrator of light and photoperiodic signaling that promotes flowering in Arabidopsis thaliana. Here we elucidate the molecular role of TZP as a positive regulator of hypocotyl elongation. We identify an interacting partner for TZP, the transcription factor ZINC-FINGER HOMEODOMAIN 10 (ZFHD10), and characterize its function in coregulating the expression of blue-light–dependent transcriptional regulators and growth-promoting genes. By employing a genome-wide approach, we reveal that ZFHD10 and TZP coassociate with promoter targets enriched in light-regulated elements. Furthermore, using a targeted approach, we show that ZFHD10 recruits TZP to the promoters of key coregulated genes. Our findings not only unveil the mechanism of TZP action in promoting hypocotyl elongation at the transcriptional level but also assign a function to an uncharacterized member of the ZFHD transcription factor family in promoting plant growth

Ferrodistortive instability at the (001) surface of half-metallic manganites

We present the structure of the fully relaxed (001) surface of the half-metallic manganite La0.7Sr0.3MnO3, calculated using density functional theory. Two relevant ferroelastic order parameters are identified and characterized. The known tilting of the oxygen octahedra, which is present in the bulk phase, decreases towards the surface. A ferrodistortive Mn off-centering, triggered by the surface and not reported before, decays monotonically into the bulk. This distortion affects neither the half-metallicity nor the zero-temperature magnetization, but does change the effective spin-spin interactions, and thus the temperature dependence of the magnetic properties

Scattering of a proton with the Li4 cluster: non-adiabatic molecular dynamics description based on time-dependent density-functional theory

We have employed non-adiabatic molecular dynamics based on time-dependent density-functional theory to characterize the scattering behaviour of a proton with the Li$_4$ cluster. This technique assumes a classical approximation for the nuclei, effectively coupled to the quantum electronic system. This time-dependent theoretical framework accounts, by construction, for possible charge transfer and ionization processes, as well as electronic excitations, which may play a role in the non-adiabatic regime. We have varied the incidence angles in order to analyze the possible reaction patterns. The initial proton kinetic energy of 10 eV is sufficiently high to induce non-adiabatic effects. For all the incidence angles considered the proton is scattered away, except in one interesting case in which one of the Lithium atoms captures it, forming a LiH molecule. This theoretical formalism proves to be a powerful, effective and predictive tool for the analysis of non-adiabatic processes at the nanoscale.Comment: 18 pages, 4 figure

Síntesis de aplicaciones de ingeniería mecánica

1 archivo PDF (72 páginas)Se ilustran algunos de los trabajos de tecnología desarrollados a partir del planteamiento de necesidades a resolver en diferentes sectores, como son el industrial, el oficial e inclusive para la misma Universidad para la solución a diferentes problemas planteados con la aplicación de la ingeniería mecánica utilizando el diseño mecánico, la manufactura y la metrología. Los resultados obtenidos se han traducido en proyectos y prototipos, de los cuales se proporciona la ficha técnica correspondiente, el dibujo de conjunto y en su caso la fotografía correspondiente

Nanospintronics with carbon nanotubes

One of the actual challenges of spintronics is the realization of a spin-transistor allowing to control spin transport through an electrostatic gate. In this review, we report on different experiments which demonstrate a gate control of spin transport in a carbon nanotube connected to ferromagnetic leads. We also discuss some theoretical approaches which can be used to analyze spin transport in these systems. We emphasize the roles of the gate-tunable quasi-bound states inside the nanotube and the coherent spin-dependent scattering at the interfaces between the nanotube and its ferromagnetic contacts.Comment: 35 pages, 15 figures, some figures in gi

Electronic stopping power in LiF from first principles.

Using time-dependent density-functional theory we calculate from first principles the rate of energy transfer from a moving proton or antiproton to the electrons of an insulating material, LiF. The behavior of the electronic stopping power versus projectile velocity displays an effective threshold velocity of approximately 0.2 a.u. for the proton, consistent with recent experimental observations, and also for the antiproton. The calculated proton/antiproton stopping-power ratio is approximately 2.4 at velocities slightly above the threshold (v approximately 0.4 a.u.), as compared to the experimental value of 2.1. The projectile energy loss mechanism is observed to be extremely local