Phase Transitions in Two-Dimensional Traffic Flow Models

We introduce two simple two-dimensional lattice models to study traffic flow in cities. We have found that a few basic elements give rise to the characteristic phase diagram of a first-order phase transition from a freely moving phase to a jammed state, with a critical point. The jammed phase presents new transitions corresponding to structural transformations of the jam. We discuss their relevance in the infinite size limit.Comment: RevTeX 3.0 file. Figures available upon request to e-address [email protected] (or 'dopico' or 'molera' or 'anxo', same node

Convectively driven sinks and magnetic fields in the quiet-Sun

©2017 The American Astronomical Society. All rights reserved. We study the relation between mesogranular flows, convectively driven sinks and magnetic fields using high spatial resolution spectropolarimetric data acquired with the Imaging Magnetograph eXperiment on board Sunrise. We obtain the horizontal velocity flow fields of two quiet-Sun regions (31.2 × 31.2 Mm2) via local correlation tracking. Mesogranular lanes and the central position of sinks are identified using Lagrange tracers. We find $6.7\times {10}^{-2}$ sinks per Mm2 in the two observed regions. The sinks are located at the mesogranular vertices and turn out to be associated with (1) horizontal velocity flows converging to a central point and (2) long-lived downdrafts. The spatial distribution of magnetic fields in the quiet-Sun is also examined. The strongest magnetic fields are preferentially located at sinks. We find that 40% of the pixels with longitudinal components of the magnetic field stronger than 500 G are located in the close neighborhood of sinks. In contrast, the small-scale magnetic loops detected by Martínez González et al. in the same two observed areas do not show any preferential distribution at mesogranular scales. The study of individual examples reveals that sinks can play an important role in the evolution of quiet-Sun magnetic features.The work by I.S.R. has been funded by the Basque Government under a grant from Programa Predoctoral de Formación de Personal Investigador del Departamento de Educación, Universidades e Investigación. This work has been partially funded by the Spanish Ministerio de Economía y Competitividad, through Projects No. ESP2013-47349-C6-1-R and ESP2014-56169-C6-1-R, including a percentage from European FEDER funds. The German contribution has been funded by the Bundesministerium für Wirtschaft und Technologie through Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR), grant number 50 OU 0401, and by the Innovationsfond of the President of the Max Planck Society (MPG). This work was partly supported by the BK21 plus program through the National Research Foundation (NRF) funded by the Ministry of Education of Korea.Peer reviewe

Validación de la escala latinoamericana y caribeña de seguridad alimentaria en gestantes adolescentes

Objetivo Realizar validación estadística de  la Escala Latinoamericana y Caribeña de Seguridad Alimentaria (ELCSA), que había sido adaptada lingüísticamente para Colombia en el año 2008 por la Escuela de Nutrición de la Universidad de Antioquia. Métodos Estudio descriptivo. Con un 95 % de nivel de confianza, se aplicó la escala ELCSA a una muestra representativa de 150 hogares de gestantes adolescentes, procedentes de población pobre y vulnerable, consultantes de la ESE Salud Pereira, entre abril y junio de 2009. Se capacitaron cuatro entrevistadores, profesionales de enfermería, sobre el objeto de cada una de las preguntas. Se encuestaron 32 hogares de sólo adultos y 118 hogares con adultos, jóvenes y niños. El análisis estadístico se realizó con SPSS. Se utilizó alfa de Cronbach,  análisis factorial y de componentes múltiples. Resultados La ELCSA mostró excelente confiabilidad aplicada tanto en hogares de sólo adultos (Cronbach=0,927), como en hogares con adultos, jóvenes y niños (Cronbach=0,953). El análisis factorial utilizando la medida de Kaiser-Meyer-Olkin, presentó alta correlación entre los ítems, tanto en hogares de solo adultos (p=0.889), como en hogares con adultos, jóvenes y niños (p=0,895). La capacidad predictiva de la escala fue de 75 % en los tres componentes identificados: calidad y cantidad de alimentos, acceso o disponibilidad de alimentos, y medios socialmente no aceptables de adquisición y distribución. Conclusiones Los resultados  validaron la escala ELCSA como un instrumento confiable para medir la seguridad alimentaria en los hogares colombianos

Rectification of electronic heat current by a hybrid thermal diode

We report the realization of an ultra-efficient low-temperature hybrid heat current rectifier, thermal counterpart of the well-known electric diode. Our design is based on a tunnel junction between two different elements: a normal metal and a superconducting island. Electronic heat current asymmetry in the structure arises from large mismatch between the thermal properties of these two. We demonstrate experimentally temperature differences exceeding $60$ mK between the forward and reverse thermal bias configurations. Our device offers a remarkably large heat rectification ratio up to $\sim 140$ and allows its prompt implementation in true solid-state thermal nanocircuits and general-purpose electronic applications requiring energy harvesting or thermal management and isolation at the nanoscale.Comment: 8 pages, 6 color figure

La sedimentación neógena en las béticas: análisis tectosedimentario

En esta Nota se presentan los primeros resultados obtenidos de un análisis tectosedimentario de la serie neógena bética. Como consecuencia de este estudio se han subdividido los materiales neógenos en siete Unidades Tectosedimentarias (UTS), delimitadas por discontinuidades sedimentarias de orden superior. El análisis de estas unidades ha permitido abordar, en el tiempo y en el espacio, problemas de gran importancia para el conocimiento de la evolución sedimentaria y tectónica del dominio bético durante el Neógeno.A preliminary description of the tectonic and sedimentary processes in the Betic Ranges along the Mio-Pliocene is presented. The Mio-Pliocene has been divide in seven «Tectosedimentary Units» (TSU) bounded at its top and base by unconformities or their correlative conformities. The regional evolutive framework is finally outlined through these practical methodology

Rasgos básicos del neógeno del Mediterráneo español

Mediante tecnologías de subsuelo propias de la industria petrolífera, se resumen los datos básicos tectosedimentarios de la cuenca neógena mediterránea española, su evolución y su conexión con los dispositivos conocidos en tierra.A short description of the tectonic and sedimentary processes affecting the Spanish Mediterranean Mio-Pliocene basin is presented, through the information obtained by subsurface oil industry methods

Asymptotics and zeros of Sobolev orthogonal polynomials on unbounded supports

In this paper we present a survey about analytic properties of polynomials orthogonal with respect to a weighted Sobolev inner product such that the vector of measures has an unbounded support. In particular, we are focused in the study of the asymptotic behaviour of such polynomials as well as in the distribution of their zeros. Some open problems as well as some new directions for a future research are formulated.Comment: Changed content; 34 pages, 41 reference

Planck intermediate results: III. The relation between galaxy cluster mass and Sunyaev-Zeldovich signal

We examine the relation between the galaxy cluster mass M and Sunyaev-Zeldovich (SZ) effect signal DA 2 Y500 for a sample of 19 objects for which weak lensing (WL) mass measurements obtained from Subaru Telescope data are available in the literature. Hydrostatic X-ray masses are derived from XMM-Newton archive data, and the SZ effect signal is measured from Planck all-sky survey data. We find an MWL-D A 2 Y500 relation that is consistent in slope and normalisation with previous determinations using weak lensing masses; however, there is a normalisation offset with respect to previous measures based on hydrostatic X-ray mass-proxy relations. We verify that our SZ effect measurements are in excellent agreement with previous determinations from Planck data. For the present sample, the hydrostatic X-ray masses at R500 are on average ~ 20 percent larger than the corresponding weak lensing masses, which is contrary to expectations. We show that the mass discrepancy is driven by a difference in mass concentration as measured by the two methods and, for the present sample, that the mass discrepancy and difference in mass concentration are especially large for disturbed systems. The mass discrepancy is also linked to the offset in centres used by the X-ray and weak lensing analyses, which again is most important in disturbed systems. We outline several approaches that are needed to help achieve convergence in cluster mass measurement with X-ray and weak lensing observations. © ESO, 2013.The Planck Collaboration acknowledges the support of: ESA; CNES and CNRS/INSU-IN2P3-INP (France); ASI, CNR, and INAF (Italy); NASA and DoE (USA); STFC and UKSA (UK); CSIC, MICINN and JA (Spain); Tekes, AoF and CSC (Finland); DLR and MPG (Germany); CSA (Canada); DTU Space (Denmark); SER/SSO (Switzerland); RCN (Norway); SFI (Ireland); FCT/MCTES (Portugal); and DEISA (EU).Peer Reviewe

Phase behaviour of additive binary mixtures in the limit of infinite asymmetry

We provide an exact mapping between the density functional of a binary mixture and that of the effective one-component fluid in the limit of infinite asymmetry. The fluid of parallel hard cubes is thus mapped onto that of parallel adhesive hard cubes. Its phase behaviour reveals that demixing of a very asymmetric mixture can only occur between a solvent-rich fluid and a permeated large particle solid or between two large particle solids with different packing fractions. Comparing with hard spheres mixtures we conclude that the phase behaviour of very asymmetric hard-particle mixtures can be determined from that of the large component interacting via an adhesive-like potential.Comment: Full rewriting of the paper (also new title). 4 pages, LaTeX, uses revtex, multicol, epsfig, and amstex style files, to appear in Phys. Rev. E (Rapid Comm.

In situ observation of stress relaxation in epitaxial graphene

Upon cooling, branched line defects develop in epitaxial graphene grown at high temperature on Pt(111) and Ir(111). Using atomically resolved scanning tunneling microscopy we demonstrate that these defects are wrinkles in the graphene layer, i.e. stripes of partially delaminated graphene. With low energy electron microscopy (LEEM) we investigate the wrinkling phenomenon in situ. Upon temperature cycling we observe hysteresis in the appearance and disappearance of the wrinkles. Simultaneously with wrinkle formation a change in bright field imaging intensity of adjacent areas and a shift in the moire spot positions for micro diffraction of such areas takes place. The stress relieved by wrinkle formation results from the mismatch in thermal expansion coefficients of graphene and the substrate. A simple one-dimensional model taking into account the energies related to strain, delamination and bending of graphene is in qualitative agreement with our observations.Comment: Supplementary information: S1: Photo electron emission microscopy and LEEM measurements of rotational domains, STM data of a delaminated bulge around a dislocation. S2: Movie with increasing brightness upon wrinkle formation as in figure 4. v2: Major revision including new experimental dat