Spin relaxation times in disordered graphene

We consider two mechanisms of spin relaxation in disordered graphene. i) Spin relaxation due to curvature spin orbit coupling caused by ripples. ii) Spin relaxation due to the interaction of the electronic spin with localized magnetic moments at the edges. We obtain analytical expressions for the spin relaxation times, tau_SO and tau_J due to both mechanisms and estimate their values for realistic parameters of graphene samples. We obtain that spin relaxation originating from these mechanisms is very weak and spin coherence is expected in disordered graphene up to samples of length L ~ 1 micron.Comment: To appear in the Proceedings of the Graphene Conference, MPI PKS Dresden, September 2006. Corrected typo

Elementary Charge Transfer Processes in a Superconductor-Ferromagnet Entangler

We study the production of spatially separated entangled electrons in ferromagnetic leads from Cooper pairs in a superconducting lead. We give a complete description of the elementary charge transfer processes, i) transfer of Cooper pairs out of the superconductor by Andreev reflection and ii) distribution of the entangled quasiparticles among the ferromagnetic leads, in terms of their statistics. The probabilities that entangled electrons flow into spatially separated leads are completely determined by experimentally measurable conductances and polarizations. Finally, we investigate how currents, noise and cross correlations are affected by transport of entangled electrons.Comment: 5 pages. Rewritten manuscript with 2 new figures. Title changed from v

Spin transport in proximity induced ferromagnetic graphene

Magnetic gates in close proximity to graphene can induce ferromagnetic correlations. We study the effect of such induced magnetization dependent Zeeman splittings on the graphene transport properties. We estimate that induced spin splittings of the order of \Delta ~ 5 meV could be achieved with the use of magnetic insulator gates, e.g. EuO-gates, deposited on top of graphene. We demonstrate that such splittings in proximity induced ferromagnetic graphene could be determined directly from the tunneling resonances in the linear response conductance, as the top gate creates also a tunable barrier in the graphene layer. We show how such splittings could also be determined independently by magnetoresistance measurements in a spin-valve geometry. Because the spin polarization of the current near the Dirac point increases with the length of the barrier, long magnetic gates are desirable for determining \Delta experimentally.Comment: 9 pages, 11 figure

The role of road freight in Uberlândia (Brazil), logistics epicenter of wholesaler-distributor sector

In structured analysis from the theory of geographical space and the circuits of urban economy, this article aims to demonstrate the peculiarities and territorial dynamics that confirmed the insertion of the Uberlândia (MG) nodal point like one of centralities of road freight transport geographical network, whose territorial configuration consists of nodals and lines which together express the organization and structuring of this activity in the Brazilian social and spatial formation. Furthermore, it show a selective spatial process that privileged certain points and areas in detriment of others, marked by concentration and action of its agents. The research concludes that the inclusion of Uberlândia in the geographical proposed network occurs because of the close relationship between the agents of road freight and wholesaler-distributor sector.Em análise estruturada a partir da teoria do espaço geográfico e dos circuitos da economia urbana, este artigo pretende demonstrar as peculiaridades e dinâmicas territoriais que corroboram a inserção do ponto nodal de Uberlândia (MG) como uma das centralidades da rede geográfica do transporte rodoviário de carga, cuja configuração territorial é composta por linhas e nodais que em seu conjunto expressam a organização e estruturação desta atividade na formação socioespacial brasileira. Além disso, evidenciam um processo de seletividade espacial que privilegiou certos pontos e áreas em detrimento de outros, demarcado pela concentração e atuação de seus agentes. A pesquisa conclui que a inserção de Uberlândia na rede geográfica proposta se dá por causa da estreita relação entre os agentes do transporte rodoviário de carga e do setor atacadista-distribuidor.Universidade Federal de São Paulo (UNIFESP)UNIFESP, EPPEN, Osasco, BrazilSciEL

Universal angular magnetoresistance and spin torque in ferromagnetic/normal metal hybrids

The electrical resistance of ferromagnetic/normal-metal (F/N) heterostructures depends on the nature of the junctions which may be tunnel barriers, point contacts, or intermetallic interfaces. For all junction types, the resistance of disordered F/N/F perpendicular spin valves as a function of the angle between magnetization vectors is shown to obey a simple universal law. The spin-current induced magnetization torque can be measured by the angular magnetoresistance of these spin valves. The results are generalized to arbitrary magnetoelectronic circuits

From Digital to Analogue Magnetoelectronics: Theory of Transport in Non-Collinear Magnetic Nanostructures

Magnetoelectronics is mainly digital, i.e. governed by up and down magnetizations. In contrast, analogue magnetoelectronics makes use of phenomena occuring for non-collinear magnetization configurations. Here we review theories which have recently been applied to the transport in non-collinear magnetic nanostructures in two and multiterminal structures, viz. random matrix and circuit theory. Both are not valid for highly transparent systems in a resistive environment like perpendicular metallic spin valves. The solution to this problem is a renormalization of the conventional and spin-mixing conductance parameters.Comment: To be published in "Advance in Solid State Physics", edited by B. Kramer, Springer Verlag, Berlin, 200

Adaptive comfort control implemented model (ACCIM) for energy consumption predictions in dwellings under current and future climate conditions: A case study located in Spain

Currently, the knowledge of energy consumption in buildings of new and existing dwellings is essential to control and propose energy conservation measures. Most of the predictions of energy consumption in buildings are based on fixed values related to the internal thermal ambient and pre-established operation hypotheses, which do not reflect the dynamic use of buildings and users’ requirements. Spain is a clear example of such a situation. This study suggests the use of an adaptive thermal comfort model as a predictive method of energy consumption in the internal thermal ambient, as well as several operation hypotheses, and both conditions are combined in a simulation model: the Adaptive Comfort Control Implemented Model (ACCIM). The behavior of ACCIM is studied in a representative case of the residential building stock, which is located in three climate zones with different characteristics (warm, cold, and mild climates). The analyses were conducted both in current and future scenarios with the aim of knowing the advantages and limitations in each climate zone. The results show that the average consumption of the current, 2050, and 2080 scenarios decreased between 23% and 46% in warm climates, between 19% and 25% in mild climates, and between 10% and 29% in cold climates by using such a predictive method. It is also shown that this method is more resilient to climate change than the current standard. This research can be a starting point to understand users’ climate adaptation to predict energy consumption

Análisis comparativo de plataformas cloud con soporte orientado a servicios de internet de las cosas

Investigación TecnológicaSe realiza un estudio de la infraestructura requerida para implementar una solución IoT; en base a este estudio se realizan dos implementaciones probando la efectividad de dos de los proveedores cloud más usados para este tipo de desarrollos, evaluando métricas y la experiencia obtenida para poder dar una guía a personas que requieran implementar IoT.INTRODUCCIÓN 1. GENERALIDADES 2. ALICACION IOT 3. AMAZON VS AZURE 4. DISEÑO MANUALES DE LABORATORIO 5. CONCLUSIONES 6. RECOMENDACIONES BIBLIOGRAFÍAPregradoIngeniero de Sistema

Semiclassical Concepts in Magnetoelectronics

Semiclassical theories of electron and spin transport in metallic magnetic structures are reviewed with emphasis on the role of disorder and electronic band structures in the current perpendicular to the interface plane (CPP) transport configuration.Comment: Proceedings of the NEC Symposium on "Spin-related Quantum Transport in Mesoscopic Systems", to be published in the Journal of Materials Science and Engineering