Influence of atomic polarization and horizontal illumination on the Stokes profiles of the He I 10830 multiplet

The polarization observed in the spectral lines of the He I 10830 multiplet carries valuable information on the dynamical and magnetic properties of plasma structures in the solar chromosphere and corona, such as spicules, prominences, filaments, emerging magnetic flux regions, etc. Here we investigate the influence of atomic level polarization on the emergent Stokes profiles for a broad range of magnetic field strengths, in both 90 degree and forward scattering geometry. We show that, contrary to a widespread belief, the selective emission and absorption processes caused by the presence of atomic level polarization may have an important influence on the emergent linear polarization, even for magnetic field strengths as large as 1000 G. Consequently, the modeling of the Stokes Q and U profiles should not be done by taking only into account the contribution of the transverse Zeeman effect within the framework of the Paschen-Back effect theory, unless the magnetic field intensity of the observed plasma structure is sensibly larger than 1000 G. We point out also that in low-lying optically thick plasma structures, such as those of active region filaments, the (horizontal) radiation field generated by the structure itself may substantially reduce the positive contribution to the anisotropy factor caused by the (vertical) radiation field coming from the underlying solar photosphere, so that the amount of atomic level polarization may turn out to be negligible. Only under such circumstances may the emergent linear polarization of the He I 10830 multiplet in such regions of the solar atmosphere be dominated by the contribution caused by the transverse Zeeman effect.Comment: Accepted for publication in The Astrophysical Journal (It is tentatively scheduled for the ApJ January 20, 2007 issue

Robust H8 design for resonant control in a CVCF inverter application over load uncertainties

CVCF (constant voltage, constant frequency) inverters are electronic devices used to supply AC loads from DC storage elements such as batteries or photovoltaic cells. These devices are used to feed different kinds of loads; this uncertainty requires that the controller fulfills robust stability conditions while keeping required performance. To address this, a robust H8 design is proposed based on resonant control to track a pure sinusoidal voltage signal and to reject the most common harmonic signals in a wide range of loads. The design is based on the definition of performance bounds in error signal and weighting functions for covering most uncertainty ranges in loads. Experimentally, the H8 controller achieves high-quality output voltage signal with a total harmonic distortion less than 2%Peer ReviewedPostprint (published version

Diagnosing the ISM of galaxies and energetic processes in a cosmological context

The evolution and formation of galaxies is one of the most interesting topics of research in astronomy. In this thesis, I focus on the interstellar medium (ISM) of galaxies and its energetic processes in a cosmological context. First, I dig into the ISM and its phases, which are the main point of interaction between the different gas components within a galaxy. Second, I look at the effects of intense star formation activity and the active galactic nuclei (AGN), which are crucial in the evolution of galaxies. I diagnose the ISM of galaxies using far-infrared (FIR) emission lines, which trace the cooling and heating of gas, to disentangle the ISM phases and analyse their dependence on other properties of the galaxies. Using cosmological simulations I reproduce the expected emissions from FIR lines at different cosmic times and estimate how the ISM phases change during the formation and evolution of galaxies. In addition, I examine the relationship between star-formation rates (SFR) and fractional AGN contributions in galaxies with different activity types to understand their importance in other observed physical parameters. Both SFR and AGN fractional contributions cause large differences in the ISM within a galaxy which are important for the accretion of mass into its supermassive black hole. The results of this thesis show that it is possible to use computational tools to understand the evolution of gas processes at different cosmic times and to estimate physical parameters that help to classify galaxies due to their energetic activity

A New Exact Method for Line Radiative Transfer

We present a new method, the Coupled Escape Probability (CEP), for exact calculation of line emission from multi-level systems, solving only algebraic equations for the level populations. The CEP formulation of the classical two-level problem is a set of {\em linear equations}, and we uncover an exact analytic expression for the emission from two-level optically thick sources that holds as long as they are in the "effectively thin" regime. In comparative study of a number of standard problems, the CEP method outperformed the leading line transfer methods by substantial margins. The algebraic equations employed by our new method are already incorporated in numerous codes based on the escape probability approximation. All that is required for an exact solution with these existing codes is to augment the expression for the escape probability with simple zone-coupling terms. As an application, we find that standard escape probability calculations generally produce the correct cooling emission by the CII 158 mic line but not by the $^3$P lines of OI.Comment: To be published in MNRAS, 13 pages, 10 figure

Servicios basados en conocimiento y desarrollo en América Latina

El buen desempeño macroeconómico de América Latina entre 2004 y 2011 (solo interrumpido en 2009 por los efectos de la crisis sistémica global) generó expectativas sobre el inicio de un posible sendero de crecimiento sostenido. Sin embargo, debido a una combinación de circunstancias externas e internas, en años recientes la situación se deterioró severamente (especialmente en Sudamérica), alejando de nuevo la esperanza de salvar las trampas del ingreso medio o bajo en el que se encuentran sumidos los países de la región.Fil: Lopez, Andres Flavio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto Interdisciplinario de Economía Politica de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Económicas. Instituto Interdisciplinario de Economía Politica de Buenos Aires; ArgentinaFil: Ramos, Daniela. Centro de Invest.para la Transformacion; Argentin

Can knowledge intensive services be a new growth engine for Latin America?

En las últimas décadas el sector servicios no sólo ha seguido ganando peso en la estructura económica global, sino que ha sufrido transformaciones cualitativas profundas, entre las cuáles se destacan la emergencia y el crecimiento de un conjunto de actividades que se caracterizan por su alto nivel de innovación y su contribución al aumento de la productividad. Se trata de los llamados “servicios intensivos en conocimiento”, que agrupan a segmentos tan diversos como servicios contables y legales, arquitectura, audiovisuales, ingeniería, software, publicidad, investigación y desarrollo (I+D), o servicios de salud y educación, pero que comparten la característica de emplear intensivamente capital humano de alto nivel de calificación y de ser usuarias y productoras de información y conocimiento para prestar servicios a sus clientes. Alrededor de estos servicios, que son altamente transables, se han formado cadenas globales de valor, hecho que ha llevado a una activa competencia entre firmas y países para ingresar y escalar dentro de las mismas. Este artículo recoge evidencia respecto de la creciente relevancia de estos servicios en la economía mundial, analiza los determinantes de la competitividad en dichos sectores, y discute el actual rol y las potencialidades de América Latina en estos mercados, con el objetivo de derivar algunas lecciones de política para la región.In the last decades, the service sector has not only increased their presence in the global economic scenario, but it also has suffered deep qualitative transformations, including the emergence and the rapid growth of a number of activities that are characterized by high innovative standards and their contribution to a considerable growth in productivity. We refer to the so called “knowledge intensive services”, which include activities as diverse as accounting and legal services, architecture, audiovisuals, engineering, software, advertising, research and development (R&D), health and education. All these activities share two main features: a) they require an intensive use of high skilled human resources; b) they use and produce information and knowledge to deliver services to their customers. Global value chains have been created in recent years around these activities, which are highly tradable, something that has led to an intense competition between firms and countries to participate and upgrade within those chains. This paper gathers evidence regarding the growing relevance of these services in the global economy. It also analyzes the determinants of competitiveness in those industries, discusses the role and perspectives of Latin America and finally suggests some policy lessons for our region.Fil: Lopez, Andres Flavio. Universidad Nacional de Tres de Febrero; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ramos, Daniela. Universidad Nacional de Tres de Febrero; Argentin

Expansion of the geographic range of Cyatta abscondita Sosa-Calvo et al., 2013 (Hymenoptera: Formicidae)

The presence of the recently described fungus-farming ant genus and species Cyatta abscondita is reported in the northwestern region of Misiones Province in Argentina. A single worker of C. abscondita was collected in a pitfall trap in a mature plantation of Pinus taeda in the Atlantic Forest biome. This finding expands the distribution of the genus and species, extending it farther south in the Neotropics.Fil: Ramos, Carolina Samanta. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Santoandre, Santiago. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Sanchez, Federico Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Zurita, Gustavo Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Universidad Nacional de Misiones. Instituto de Biología Subtropical; ArgentinaFil: Filloy, Julieta. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentin

Collision of the mocha fracture zone and a <4 Ma old wave of orogenic uplift in the Andes (36°-38°S)

The southern Central and northern Patagonian Andes (34°-45°S) are characterized by low to no crustal seismicity at the retroarc fold and thrust belt, in contrast to the Pampean flat subduction zone located immediately to the north (27°-33°30'S). Detailed examination of this area shows no indication of contractional neotectonics with the exception of the segment located between 36° and 38°S. There, out-of-sequence transpressional deformation, initially developed in the 1.7-1.4 Ma interval, affects the western retroarc between 36° and 38°S next to the arc zone. It is between these latitudes that contractional deformation <3.6 Ma old developed in the forearc region. Oblique collision of the Mocha fracture zone and its associated rise explains the distribution, extent, and timing of <3.6 Ma contractional deformations from the forearc to the foreland, as well as incipient shallowing of the Nazca plate beneath the South American plate, which has been inferred from seismic, gravimetric, and arc dynamics studies.Fil: Folguera Telichevsky, Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Ramos, Victor Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentin