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

La universidad, institución social

La universidad ha sido la institución social que se ha otorgado la función de escudriñar la realidad en sus diferentes ámbitos y manifestaciones, con la intención de develar sus misterios, descubrir su sentido y finalidad, de comprenderla, de apropiarse de su verdad. El carácter social e histórico de esta institución ha hecho que la idea de universidad tome múltiples matices con el transcurrir de los siglos; en nuestros días no es posible una definición universalmente válida de lo que es o debería ser la universidad. El artículo pretende mostrar una visión completa, profunda y sintética de los rasgos esenciales de la institución universitaria, mediante una aproximación teleológica y el recurso a la tradición histórica

Critical issues of double-metal layer coating on FBG for applications at high temperatures

Use of fiber Bragg gratings (FBGs) to monitor high temperature (HT) applications is of great interest to the research community. Standard commercial FBGs can operate up to 600 ∘ C. For applications beyond that value, specific processing of the FBGs must be adopted to allow the grating not to deteriorate. The most common technique used to process FBGs for HT applications is the regeneration procedure (RP), which typically extends their use up to 1000 ∘ C. RP involves a long-term annealing of the FBGs, to be done at a temperature ranging from 550 to 950 ∘ C. As at that temperature, the original coating of the FBGs would burn out, they shall stay uncoated, and their brittleness is a serious concern to deal with. Depositing a metal coating on the FBGs prior to process them for RP offers an effective solution to provide them with the necessary mechanical strengthening. In this paper, a procedure to provide the FBG with a bimetallic coating made by copper and nickel electrodeposition (ED) is proposed, discussing issues related to the coating morphology, adherence to the fiber, and effects on the grating spectral response. To define the processing parameters of the proposed procedure, production tests were performed on dummy samples which were used for destructive SEM-EDS analysis. As a critical step, the proposed procedure was shown to necessitate a heat treatment after the nickel ED, to remove the absorbed hydrogen. The spectral response of the FBG samples was monitored along the various steps of the proposed procedure and, as a final proof test for adherence stability of the bimetallic coating, along a heating/cooling cycle from room temperature to 1010 ∘ C. The results suggest that, given the emergence of Kirkendall voids at the copper-nickel interface, occurring at the highest temperatures (700-1010 ∘ C), the bimetallic layer could be employed as FBG coating up to 700 ∘ C

Unveiling the environment surrounding LMXB SAX J1808.4-3658

Low-mass X-ray binaries (LMXBs) are a natural workbench to study accretion disk phenomena and optimal background sources to measure elemental abundances in the Interstellar medium (ISM). In high-resolution XMM-Newton spectra, the LMXB SAX J1808.4-3658 showed in the past a neon column density significantly higher than expected given its small distance, presumably due to additional absorption from a neon-rich circumstellar medium (CSM). It is possible to detect intrinsic absorption from the CSM by evidence of Keplerian motions or outflows. For this purpose, we use a recent, deep (100 ks long), high-resolution Chandra/LETGS spectrum of SAX J1808.4-3658 in combination with archival data. We estimated the column densities of the different absorbers through the study of their absorption lines. We used both empirical and physical models involving photo- and collisional-ionization in order to determine the nature of the absorbers. The abundances of the cold interstellar gas match the solar values as expected given the proximity of the X-ray source. For the first time in this source, we detected neon and oxygen blueshifted absorption lines that can be well modeled with outflowing photoionized gas. The wind is neon rich (Ne/O>3) and may originate from processed, ionized gas near the accretion disk or its corona. The kinematics (v=500-1000 km/s) are indeed similar to those seen in other accretion disks. We also discovered a system of emission lines with very high Doppler velocities (v~24000 km/s) originating presumably closer to the compact object. Additional observations and UV coverage are needed to accurately determine the wind abundances and its ionization structure.Comment: 12 pages, 10 figures, accepted for publication on A&

Planning for strategic change in the project delivery strategy

For organizations such as state departments of transportation, other public agencies, or private companies, adopting a new approach to procure services for delivery of construction projects requires significant organizational changes; modifications to both their work processes and existing organizational structures may be needed. These adjustments, encompassing many different aspects of the organization's interests, must occur for the change initiative to be successfully put into practice. In this research, the adoption of integrated project delivery methods within the transportation project sector is investigated to better understand the dynamics of this change. In the context of this study, an Owner's project delivery strategy is defined as the set of project delivery methods that are adopted for delivering capital projects. This dissertation presents findings from a study of Public Owner organizations that have implemented the designbuild method for delivering highway projects. Using as a case study the new $1.3 billion SH-130 tolled expressway project in Central Texas, the author analyzed project documentation and conducted many interviews with individuals affiliated with owner, legal, engineering consultants, and contractors. Findings suggest that project representatives institutionalize practices and routines connected to the new approach by adapting to new challenges, rather than "overwriting" previously existing practices. Similarly, the institutionalization of innovative approaches to project delivery happens concurrently with a deinstitutionalization of the previous approaches. Building upon these findings, a conceptual framework is presented for helping Owner organizations implement change in their project delivery strategy. The proposed conceptual framework is based upon both existing published literature and interviews with managers involved in implementing a strategic change in project delivery strategy. This framework was further refined by making a comparative study of four transportation projects in the United States. In addition, a detailed implementation framework was validated and further developed through a Delphi study with representatives from several organizations whose major responsibilities and experiences include the management of change in procurement approach. Findings from these studies, including application to the construction industry and other industries are presented.Civil, Architectural, and Environmental Engineerin

EPOC en la mujer

The prevalence of chronic obstructive pulmonary disease (COPD) is increasing worldwide, mainly due to the increase in women. In developed countries, COPD in women is mainly a result of exposure to tobacco smoke and in developing countries to inhalation of biomass combustion products. Underdiagnosis of COPD is more common in women since this disease has classically been associated with men. Moreover, COPD in women shows certain differential features, such as a greater expression of aspects related to perception (dyspnea and health-related quality of life), a high prevalence of malnutrition, anxiety and depression, and a distinct distribution of emphysema from that in men. Better phenotypical characterization of COPD in women would allow its impact on the health system to be more accurately evaluated and more individualized therapeutic strategies to be designe

Cross-species tests of 45 microsatellite loci isolated from different species of ungulates in the Iberian red deer (Cervus elaphus hispanicus) to generate a multiplex panel

The Iberian red deer (Cervus elaphus hispanicus) is an emblematic game species in Spain. To generate a battery of polymorphic markers for multiplex polymerase chain reactions for the Spanish red deer, 45 loci isolated in different species of ungulates were tested. Of the primers tested, 27 amplified but only 21 were polymorphic. Eleven of these markers were subsequently optimized for multiplex in four polymerase chain reactions. This allows analysing several molecular markers jointly to substantially reduce costs. Finally, we report descriptive summary statistics such as number of alleles for the former and also test of disequilibria and heterozygosity for the latter. © 2008 The Authors.Peer Reviewe

Registro de tapir centroamericano (Tapirus bairdii) con cámaras-trampa en la sierra Madre de Oaxaca, México

ResumenEn este trabajo se presenta evidencia del tapir centroamericano (Tapirus bairdii) obtenida en la sierra Norte de Oaxaca por medio de cámaras-trampa durante marzo y abril de 2012, confirmando su presencia en esta región.AbstractThis paper presents evidence of the Baird's tapir (Tapirus bairdii) obtained in the Sierra Norte de Oaxaca by camera traps in March and April 2012, confirming its presence in this region