THE IMPRINT of RADIAL MIGRATION on the VERTICAL STRUCTURE of GALAXY DISKS

We use numerical simulations to examine the effects of radial migration on the vertical structure of galaxy disks. The simulations follow three exponential disks of different mass but similar circular velocity, radial scalelength, and (constant) scale height. The disks develop different non-axisymmetric patterns, ranging from feeble, long-lived multiple arms to strong, rapidly evolving few-armed spirals. These fluctuations induce radial migration through secular changes in the angular momentum of disk particles, mixing the disk radially and blurring pre-existing gradients. Migration primarily affects stars with small vertical excursions, regardless of spiral pattern. This "provenance bias" largely determines the vertical structure of migrating stars: inward migrators thin down as they move in, whereas outward migrators do not thicken up but rather preserve the disk scale height at their destination. Migrators of equal birth radius thus develop a strong scale-height gradient, not by flaring out as commonly assumed, but by thinning down as they spread inward. Similar gradients have been observed for low-[α/Fe] mono-abundance populations (MAPs) in the Galaxy, but our results argue against interpreting them as a consequence of radial migration. This is because outward migration does not lead to thickening, implying that the maximum scale height of any population should reflect its value at birth. In contrast, Galactic MAPs have scale heights that increase monotonically outward, reaching values that greatly exceed those at their presumed birth radii. Given the strong vertical bias affecting migration, a proper assessment of the importance of radial migration in the Galaxy should take carefully into account the strong radial dependence of the scale heights of the various stellar populations. © 2016. The American Astronomical Society. All rights reserved

EXCITATION of COUPLED STELLAR MOTIONS in the GALACTIC DISK by ORBITING SATELLITES

We use a set of high-resolution N-body simulations of the Galactic disk to study its interactions with the population of cosmologically predicted satellites. One simulation illustrates that multiple passages of massive satellites with different velocities through the disk generate a wobble, which has the appearance of rings in face-on projections of the stellar disk. They also produce flares in the outer disk parts and gradually heat the disk through bending waves. A different numerical experiment shows that an individual satellite as massive as the Sagittarius dwarf galaxy passing through the disk will drive coupled horizontal and vertical oscillations of stars in underdense regions with small associated heating. This experiment shows that vertical excursions of stars in these low-density regions can exceed 1 kpc in the Solar neighborhood, resembling the recently locally detected coherent vertical oscillations. They can also induce non-zero vertical streaming motions as large as 10-20 km s-1, which is consistent with recent observations in the Galactic disk. This phenomenon appears as a local ring with modest associated disk heating. © 2016. The American Astronomical Society. All rights reserved

Eldorado. A Four-Part Song

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Lead electrorefining process from exhausted lead acid batteries by using acidic and alkaline electrolytes

The recycling of lead acid batteries (LABs) comprises relevant concerns on the suitable methodologies to recover lead. In this investigation, two electrorefining processes, by using acidic and alkaline electrolytes, have been compared to determine the most significant results of both methodologies. Acidic electrolytes used 200 g/L HBF4, 1.2 g/L H3PO4, 10 g/L H3BO3, and 100 g/L PbO, while the alkaline ones employed 120 g/L NaOH, 75 g/L PbO, 50-92 g/L glycerol, and 2 g/L gelatin. All the solutions were studied by varying temperature and current density (CD) to determine remarkable changes on current efficiency (CE), cell voltage (CV), specific energy consumption (SEC), and on the deposit quality. The results highlighted that by using the acidic electrolyte containing dextrin it is possible to obtain a compact deposit even using high CDs. Acidic solution without dextrin addition allows to obtain good quality deposits by working at 40 degrees C and 100 A/m(2) CD. After testing the behavior of different alkaline electrolytes, it is possible to observe that the solution containing the highest glycerol concentration allows to obtain, for intermediate valued of CD, CE higher than 97% with a SEC of about 0.37 kWh/kg. By comparing the results it is evident that the acidic electrolyte is the one that allows to reach higher productivity with lower SEC. In the selected conditions, lead deposits appear pure and compact.[GRAPHICS]

A method for the optimal design of composite continuum structures

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76840/1/AIAA-1998-4984-312.pd

Adsorption and Vibrational Study of Folic Acid on Gold Nanopillar Structures Using Surface-enhanced Raman Scattering Spectroscopy

This paper presents a study of adsorption and vibrational features of folic acid, using surface-enhanced Raman scattering (SERS). A gold-capped silicon nanopillar (Au NP) with a height of 600 nm and a width of 120 nm was utilized to study the vibrational features of FA molecules adsorbed on the nanopillars within the high electromagnetic field areas. The adsorption behaviour of folic acid and the band assignment of the main vibrations together with the optimized geometry of folic acid and folic acid in the presence of a cluster of 10 gold atoms were assessed using the density functional theory (B3LYP(6-31G(d))) and the scalar relativistic effective core potential with a double-zeta basis set (LANL2DZ). The vibrations obtained from the solid-state folic acid and the folic acid on a gold cluster were in accordance with those observed experimentally. The analysis of the main vibrations indicated that the interaction of folic acid with the Au NP occurred primarily through the nitrogen atoms, from their pteridine ring. Finally, the obtained adsorption isotherm for folic acid was deduced from the analysis of the SERS spectra and it followed a negative cooperative binding model

Enseñanza de circuitos: ¿dependen los resultados de la experiencia del docente?

El objetivo de este trabajo es mostrar como depende la efectividad de la instrucción de la experiencia del docente. Para ello se comparan los resultados obtenidos por tres docentes de muy distinta experiencia, un profesor con más de 20 años de experiencia docente y dos alumnos de Profesorado en Física, que realizaron esta instrucción como parte de sus prácticas docentes. La estrategia utilizada en las tres clases experimentales fue Tutoriales para Física Introductoria, que fue implementada en similares condiciones en distintas clases de la escuela secundaria. En todos los casos el conocimiento conceptual fue determinada con el test DIRECT. Trabajos previos de nuestro grupo había mostrado que Tutoriales produce un aprendizaje conceptual más profundo y duradero que la instrucción tradicional, independientemente del género y condición socio-económica de los estudiantes. El presente trabajo muestra que los buenos resultados se mantienen independientemente de la experiencia del docente, siempre que el mismo haya tenido un adecuado entrenamiento en la utilización de metodologías de enseñanza para el aprendizaje activo.The aim of this work is to show how the efficiency of instruction depends on teacher's experience. The conceptual knowledge on electric circuits have been measured with the test DIRECT on four classes taught by three teachers of very different experience: one with more than 20 years of teaching experience, and other two that taught this subject as part of their pre-graduation training. Tutorials for Introductory Physics was the activelearning teaching strategy used in all cases, implemented under similar conditions. The present results indicate that the efficiency of instruction was the same for all teachers, provided they use the same teaching strategy and have been properly trained for it. It also confirmed, for these inexperienced teachers, that Tutorials is clearly more efficient than traditional instruction in fostering conceptual learning.Fil: Sirur Flores, J.. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Departamento de Física; ArgentinaFil: Lenhe, G.. Colegio San Luis Gonzaga; ArgentinaFil: Sánchez, E.. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Departamento de Física; ArgentinaFil: Benegas, Julio Ciro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi". Universidad Nacional de San Luis. Facultad de Ciencias Físico, Matemáticas y Naturales. Instituto de Matemática Aplicada de San Luis ; Argentina. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Departamento de Física; Argentin