Spin-filtering effect in the transport through a single-molecule magnet Mn12_{12} bridged between metallic electrodes

Electronic transport through a single-molecule magnet Mn$_{12}$ in a two-terminal set up is calculated using the non-equilibrium Green's function method in conjunction with density-functional theory. A single-molecule magnet Mn$_{12}$ is bridged between Au(111) electrodes via thiol group and alkane chains such that its magnetic easy axis is normal to the transport direction. A computed spin-polarized transmission coefficient in zero-bias reveals that resonant tunneling near the Fermi level occurs through some molecular orbitals of majority spin only. Thus, for low bias voltages, a spin-filtering effect such as only one spin component contributing to the conductance, is expected. This effect would persist even with inclusion of additional electron correlations.Comment: Accepted for publication at J. Appl. Phy

Nonadiabatic Quantum Dynamics Predissociation of H2O+(B 2B2)

This document is the unedited author's version of a Submitted Work that was subsequently accepted for publication in The Journal of of Physical Chemistry Letters, copyright © American Chemical Society after peer review. To access the final edited and published work, see DOI: http://dx.doi.org/10.1021/jz5022894A quantum-mechanical study of the predissociation of H2O+(B˜ 2B2) is carried out by using wave packet propagations on ab initio potential energy surfaces connected by nonadiabatic couplings. The simulations show that within the first 30 fs, 80% of the initial wave packet is transferred from the B 2B2 to the A˜ 2A1 electronic state through a conical intersection. A much slower transfer (in the ps timescale) from the A˜ 2A1 to the X˜2B1 state due to a Renner-Teller coupling determines the fragmentation branching ratios, which are in accordance with the experimental measurementsThis work has been partially supported by projects ENE2007-62934 and ENE2011-28200 (Secretaría de Estado de I+D+i, Spain) and the European COST actions CM1204 (XLIC) and MP1002 (Nano-IBCT). The calculations have been performed at the Centro de Computación Científica of the UAM

Stress relaxation losses of prestressing steel wires

Prestressed structures are susceptible to relaxation losses which are of significant importance in structural design. After being manufactured, prestressing wires are coiled to make their storage and transportation easier. The possible deleterious effects of this operation on the stress relaxation behavior of prestressing steel wires are usually neglected, though it has been noticed by manufacturers and contractors that when relaxation tests are carried out after a long-time storage, on occasions relaxation losses are higher than those measured a short time after manufacturing. The influence of coiling on the relaxation losses is checked by means of experimental work and confirmed with a simple analytical model. The results show that some factors like initial residual stresses, excessively long-time storage or storage at high temperatures, can trigger or accentuate this damage. However, it is also shown that if the requirements of standards are fulfilled (minimum coiling diameters) these effects can be neglected

Ab initio description of the fragmentation of H2O+(B2B2)

A quantum-dynamical study of the fragmentation of H2O+(B2B2) is carried out by using wave packet propagations on ab initio potential energy surfaces connected by nonadiabatic couplings assuming a Franck- Condon initial wave packet from the ground state of the water molecule. The simulations indicate that a conical intersection between the B2B2 and à 2A1 states of H2O+ allows the transfer of 80% of the initial wave packet within 30 fs, while the Renner-Teller coupling between the à 2A1 and B1 states determines the fragmentation branching rations in the ps timescal

Nonadiabatic fragmentation of H2O+ and isotopomers. Wave packet propagation using ab initio wavefunctions

The fragmentation of the water cation from its B 2B2 electronic state, allowing the participation of the X 2B1, Ã 2A1 and C 2B1 states in the process, is simulated using the extended capabilities of the collocation GridTDSE code to account for the nonadiabatic propagation of wave packets in several potential energy surfaces connected by nonadiabatic couplings. Molecular data are calculated ab initio. Two initial wave packets are considered to reproduce two different experiments. The isotopic effect in the fragmentation of D2O+ and HDO+ is also studied and the results show very good agreement with the experimental cleavage preference in the fragmentation of HDO+This work has been partially supported by Ministerio de Economía and Competitividad (Spain), project ENE2014-52432-

Shocks económicos y cambios en los patrones de escolaridad y gasto educativo

Este documento investiga como los shocks económicos tienen un efecto sobre los patrones de inversión en capital humano de las familias, analizando cómo se modifica el avance de los niños de 6 a 14 años en el sistema educativo peruano. A diferencia de otros estudios que han analizado el impacto de shocks sobre la acumulación de capital humano basándose, principalmente, en el análisis de la asistencia a la escuela, aquí se plantea un análisis más comprehensivo de los distintos mecanismos a través de los cuales la inversión en educación se puede ver afectada por los shocks. Se encuentra que los mecanismos planteados son consistentes con la hipótesis de que los shocks también pueden tener impacto sobre la reducción en la calidad de la educación. Así, no se encuentra evidencia que shocks negativos tengan un impacto sobre el atraso educativo adicional, por lo que no habría tampoco un efecto sobre la deserción escolar. Sin embargo, aún cuando ante un shock negativo no haya un cambio en el tiempo dedicado a la educación, se encuentra que sí se reduce la acumulación efectiva de capital humano a través de una reducción en el gasto en educación, tanto en zonas urbanas como rurales. Se encuentra evidencia de este efecto tanto en el caso de reducciones en el ingreso, y condicional a cambios en el ingreso cuando algún miembro del hogar pierde su empleo

Shocks económicos y cambios en los patrones de escolaridad y gasto educativo

Este documento investiga como los shocks económicos tienen un efecto sobre los patrones de inversión en capital humano de las familias, analizando cómo se modifica el avance de los niños de 6 a 14 años en el sistema educativo peruano. A diferencia de otros estudios que han analizado el impacto de shocks sobre la acumulación de capital humano basándose, principalmente, en el análisis de la asistencia a la escuela, aquí se plantea un análisis más comprehensivo de los distintos mecanismos a través de los cuales la inversión en educación se puede ver afectada por los shocks. Se encuentra que los mecanismos planteados son consistentes con la hipótesis de que los shocks también pueden tener impacto sobre la reducción en la calidad de la educación. Así, no se encuentra evidencia que shocks negativos tengan un impacto sobre el atraso educativo adicional, por lo que no habría tampoco un efecto sobre la deserción escolar. Sin embargo, aún cuando ante un shock negativo no haya un cambio en el tiempo dedicado a la educación, se encuentra que sí se reduce la acumulación efectiva de capital humano a través de una reducción en el gasto en educación, tanto en zonas urbanas como rurales. Se encuentra evidencia de este efecto tanto en el caso de reducciones en el ingreso, y condicional a cambios en el ingreso cuando algún miembro del hogar pierde su empleo

Does illicit drug use affect labor market outcomes? Evidence from a developing country

Illicit drug use is often related to several problems for individuals who participate on the labor market due to decreasing productivity, absenteeism, increasing crime and health consequences -- This study analyzes the relationship between substance use and labor market outcomes using econometric methods to address the potential endogeneity problem -- We use a large data set for Medellin, Colombia, to find the causal effect of drug use on labor supply and labor force participation -- According to most existing research, we found that drug use affects negatively the probability of being employed and the probability of participate in the labor forc

Tuning the electrical conductivity of nanotube-encapsulated metallocene wires

We analyze a new family of carbon nanotube-based molecular wires, formed by encapsulating metallocene molecules inside the nanotubes. Our simulations, that are based on a combination of non-equilibrium Green function techniques and density functional theory, indicate that these wires can be engineered to exhibit desirable magnetotransport effects for use in spintronics devices. The proposed structures should also be resilient to room-temperature fluctuations, and are expected to have a high yield.Comment: 4 pages, 6 figures. Accepted in Physical Review Letter

Acoustical rehabilitation project of the Santa María de la Mota church, in Montoro (Córdoba)

The current importance of cultural heritage is traduced in recuperation programs of historic heritage. One of these working lines is the rehabilitation of churches for their conditioning for cultural uses. Intervention on ecclesiastic spaces should respond to acoustic conditioning. The aim of this work is to study the acoustic conditions of the Santa María de la Mota Church, in Montoro (Cordoba), starting from values measured in situ and by means of computer simulation. This church, from the XIIIth century, was restored and adapted for cultural uses, but presents acoustic disfunctions. Therefore, architectural solutions to obtain a correct acoustical rehabilitation have been proposed, both for theatral and musical uses. Ponencia presentada en European and Japanese Symposium on Acoustics: Forum Acusticu