3,453 research outputs found
Recollimation Shocks in Magnetized Relativistic Jets
We have performed two-dimensional special-relativistic magnetohydrodynamic
simulations of non-equilibrium over-pressured relativistic jets in cylindrical
geometry. Multiple stationary recollimation shock and rarefaction structures
are produced along the jet by the nonlinear interaction of shocks and
rarefaction waves excited at the interface between the jet and the surrounding
ambient medium. Although initially the jet is kinematically dominated, we have
considered axial, toroidal and helical magnetic fields to investigate the
effects of different magnetic-field topologies and strengths on the
recollimation structures. We find that an axial field introduces a larger
effective gas-pressure and leads to stronger recollimation shocks and
rarefactions, resulting in larger flow variations. The jet boost grows
quadratically with the initial magnetic field. On the other hand, a toroidal
field leads to weaker recollimation shocks and rarefactions, modifying
significantly the jet structure after the first recollimation rarefaction and
shock. The jet boost decreases systematically. For a helical field, instead,
the behaviour depends on the magnetic pitch, with a phenomenology that ranges
between the one seen for axial and toroidal magnetic fields, respectively. In
general, however, a helical magnetic field yields a more complex shock and
rarefaction substructure close to the inlet that significantly modifies the jet
structure. The differences in shock structure resulting from different field
configurations and strengths may have observable consequences for disturbances
propagating through a stationary recollimation shock.Comment: 14 pages, 15 figures and 1 table, accepted for publication in Ap
MAPCAT: Monitoring AGN with Polarimetry at the Calar Alto Telescopes
We introduce MAPCAT, a long-term observing program for "Monitoring of AGN
with Polarimetry at the Calar Alto Telescopes". Multi-spectral-range studies
are critical to understand some of the most relevant current problems of high
energy astrophysics of blazars such as their high energy emission mechanisms
and the location of their gamma-ray emission region through event associations
across the spectrum. Adding multi-spectral-range polarimetry allows for even
more reliable identification of polarized flares across the spectrum in these
kind of objects, as well as for more accurate modeling of their magnetic field.
As part of a major international effort to study the long term multi-spectral
range polarimetric behavior of blazars, MAPCAT uses -since mid 2007- CAFOS on
the 2.2m Telescope at the Calar Alto Observatory (Almeria, Spain) to obtain
monthly optical (R-band) photo-polarimetric measurements of a sample of 34 of
the brightest gamma-ray, optical, and radio-millimeter blazars accessible from
the northern hemisphere.Comment: To be published in the proceedings of High Energy Phenomena in
Relativistic Outflows III (HEPRO III, IJMPCS). 4 page
Live lecture screencast recording: a proposal to simplify the tasks associated with content production for video-teaching
Se trata de un resumen (Abstract) de la contribución. El acuerdo de transferencia de copyright del trabajo completo es incompatible con el depósito del mismo en RIUMA.Se describe la implementación inicial de un método simplificado de grabación en directo de sesiones de clase en asignaturas de las Escuelas de Ingeniería de la Universidad de Málaga. La simplificación se logra al incorporar en la actividad diaria del aula ciertas características típicas de la grabación en diferido de mini videos docentes. En una configuración mínima se graba únicamente el audio y el video en pantalla de la clase, evitando los desafíos técnicos y las dificultades que implica la grabación de otros elementos como la pizarra. Esto implica el uso de anotaciones en pantalla en tiempo real para reemplazar completamente las anotaciones en la pizarra.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech.
I Plan Propio Integral de Docencia. Universidad de Málaga.
Universidad de Málaga. Vicerectorado de Personal Docente e Investigador, Proyectos de Innovación Educativa (PIE 17-018
Dynamic behaviour of multi-terminal VSC-based HVDC after a converter outage: DC control strategy
The aim of this paper is to evaluate the effect of DC-voltage control strategy on dynamic behaviour of multi-terminal Voltage-Source Converter (VSC)-Based HVDC after a converter outage. In this paper, two dc voltage control strategies are considered: (i) standard voltage margin method (SVMM) and (ii) standard voltage-droop method (SVDM). The impact is evaluated in this paper using time-domain simulations on simple test system using DIgSILENT PowerFactory considering a sudden disconnection of a converter-station. Simulation results demonstrate how important is the dc-voltage control strategy and the location/number of dc-buses involved in the dc-voltage on the dynamic response of the MTDC systems. The voltage margin control is capable to survive a converter outage just if this converter is operating on constant power mode
Characterization of Sex-Based Dna Methylation Signatures in the Airways During Early Life.
Human respiratory conditions are largely influenced by the individual\u27s sex resulting in overall higher risk for males. Sex-based respiratory differences are present at birth suggesting a strong genetic component. Our objective was to characterize early life sex-based genomic signatures determined by variable X-chromosome methylation in the airways. We compared male versus female genome-wide DNA methylation in nasal airway samples from newborns and infants aged 1-6 months (N = 12). We analyzed methylation signals across CpG sites mapped to each X-linked gene using an unsupervised classifier (principal components) followed by an internal evaluation and an exhaustive cross-validation. Results were validated in an independent population of children (N = 72) following the same algorithm. X-linked genes with significant sex-based differential methylation in the nasal airway of infants represented only about 50% of the unique protein coding transcripts. X-linked genes without significant sex-based differential methylation included genes with evidence of escaping X-inactivation and female-biased airway expression. These genes showed similar methylation patterns in males and females suggesting unbalanced X-chromosome dosage. In conclusion, we identified that the human airways have already sex-based DNA methylation signatures at birth. These early airway epigenomic marks may determine sex-based respiratory phenotypes and overall predisposition to develop respiratory disorders later in life
3 mm GMVA Observations of Total and Polarized Emission from Blazar and Radio Galaxy Core Regions
We present total and linearly polarized 3 mm Global mm-VLBI Array images of a
sample of blazars and radio galaxies from the VLBA-BU-BLAZAR 7 mm monitoring
program designed to probe the innermost regions of active galactic nuclei (AGN)
jets and locate the sites of gamma-ray emission observed by the Fermi-LAT. The
lower opacity at 3 mm and improved angular resolution, on the order of 50
microarcseconds, allow us to distinguish features in the jet not visible in the
7 mm VLBA data. We also compare two different methods used for the calibration
of instrumental polarisation and we analyze the resulting images for some of
the sources in the sample.Comment: Polarised Emission from Astrophysical Jets, June 12-16, 2017,
Ierapetra, Greec
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