4,788 research outputs found
Nuclear Kinematics of Narrow-line Seyfert 1 Galaxies
Here I present the main results of a kinematical study of narrow line Seyfert 1 galaxies through long slit spectroscopy.Fil: Schmidt, Eduardo Osvaldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; Argentin
All-fibre wavelength versatile short pulsed laser sources
Pulsed lasers operating in the picosecond or femtosecond regimes find a wide range of applications in optical sciences, such as spectroscopy, laser surgery, material processing and optical communications. Among the existing sources of short-pulses, mode-locked fibre lasers play an important role mainly due to their robust and compact nature, and also due to their ability to generate outputs over a wide range of repetition-rates, pulse durations, pulse shapes, peak powers and optical wavelengths.
Considering the case of wavelength versatility, Raman amplification can be used to fill the spectral gaps that are not covered by the emission band of traditional rare-earth doped elements such as ytterbium and erbium, allowing the generation of light at unconventional wavelengths. Additionally, another contribution has come from the recent development of new nanomaterials such as graphene and carbon nanotubes that can be used as saturable absorbers over a broadband wavelength range.
The experimental work reported in this thesis is mainly focused in combining the wavelength versatility allowed by Raman gain and carbon nanotubes and graphene to generate short-pulsed fibre lasers at different wavelengths. High power ytterbium and erbium lasers and also a high power Raman laser operating at 1450 nm are used as pump sources to seed the Raman gain and carbon nanotubes and graphene are the saturable absorbers used as mode-lockers. All the fibres utilized in the oscillators are highly non-linear single mode silica fibres doped with GeO2.
The lasers operate in the dissipative soliton regime, generating chirped pulses with durations on the order of hundred of picosecond that are suitable for external compression. We demonstrate for example an erbium-pumped Raman oscillator generating 500 ps pulses that are linearly compressed to 2 ps. The results presented in this document are a contribution towards making fibre based lasers more universal devices in terms of wavelength operation.Open Acces
La factura electrónica en los sistemas de información
La presente investigación, se centra en cómo la factura electrónica, está afectando las actividades y tareas que desarrollan las empresas, específicamente en el área administrativa financiera contable, desde un enfoque de sistemas socio-técnico, estudiando la herramienta en sus aspectos
organizacionales, administrativos y tecnológicos; y tendiendo a cumplir con los siguientes
objetivos:
General:
- Conocer cómo han actuado las organizaciones frente a la factura electrónica, para luego proponer una forma “ideal" de integración de la factura electrónica a los sistemas de información de una empresa que les permita aprovechar todos sus beneficios.
Específicos:
- Relevar todos aquellos factores que motivaron a las empresas a la aplicación y uso de
la facturación electrónica y las intenciones futuras de continuar operando con este sistema.
- Identificar los beneficios que trae aparejado el uso de la factura electrónica dentro de las empresas, en especial los relacionados con su integración a los sistemas de información.
- Conocer cuál ha sido el grado de intervención de los profesionales contadores en la
decisión y dentro del proceso de implementación de esta herramienta.
- Identificar problemas surgidos a profesionales en la implementación de factura electrónica y relevar las soluciones existentes a las problemáticas identificadas;
- Analizar el circuito de la factura electrónica en las distintas áreas de una empresa y
compararlo con el de la factura tradicional.
- Proporcionar mejoras a la actual forma de utilización de factura electrónica.Fil: Artola, Matías Eduardo. Universidad Nacional de Cuyo. Facultad de Ciencias Económicas.Fil: Schmidt, María Victoria. Universidad Nacional de Cuyo. Facultad de Ciencias Económicas
Stacked Weak Lensing Mass Calibration: Estimators, Systematics, and Impact on Cosmological Parameter Constraints
When extracting the weak lensing shear signal, one may employ either locally
normalized or globally normalized shear estimators. The former is the standard
approach when estimating cluster masses, while the latter is the more common
method among peak finding efforts. While both approaches have identical
signal-to-noise in the weak lensing limit, it is possible that higher order
corrections or systematics considerations make one estimator preferable over
the other. In this paper, we consider the efficacy of both estimators within
the context of stacked weak lensing mass estimation in the Dark Energy Survey
(DES). We find the two estimators have nearly identical statistical precision,
even after including higher order corrections, but that these corrections must
be incorporated into the analysis to avoid observationally relevant biases in
the recovered masses. We also demonstrate that finite bin-width effects may be
significant if not properly accounted for, and that the two estimators exhibit
different systematics, particularly with respect to contamination of the source
catalog by foreground galaxies. Thus, the two estimators may be employed as a
systematics cross-check of each other. Stacked weak lensing in the DES should
allow for the mean mass of galaxy clusters to be calibrated to about 2%
precision (statistical only), which can improve the figure of merit of the DES
cluster abundance experiment by a factor of ~3 relative to the self-calibration
expectation. A companion paper (Schmidt & Rozo, 2010) investigates how the two
types of estimators considered here impact weak lensing peak finding efforts.Comment: 14 pages, 9 figures; comments welcom
Weak Lensing Peak Finding: Estimators, Filters, and Biases
Large catalogs of shear-selected peaks have recently become a reality. In
order to properly interpret the abundance and properties of these peaks, it is
necessary to take into account the effects of the clustering of source
galaxies, among themselves and with the lens. In addition, the preferred
selection of lensed galaxies in a flux- and size-limited sample leads to
fluctuations in the apparent source density which correlate with the lensing
field (lensing bias). In this paper, we investigate these issues for two
different choices of shear estimators which are commonly in use today:
globally-normalized and locally-normalized estimators. While in principle
equivalent, in practice these estimators respond differently to systematic
effects such as lensing bias and cluster member dilution. Furthermore, we find
that which estimator is statistically superior depends on the specific shape of
the filter employed for peak finding; suboptimal choices of the
estimator+filter combination can result in a suppression of the number of high
peaks by orders of magnitude. Lensing bias generally acts to increase the
signal-to-noise \nu of shear peaks; for high peaks the boost can be as large as
\Delta \nu ~ 1-2. Due to the steepness of the peak abundance function, these
boosts can result in a significant increase in the abundance of shear peaks. A
companion paper (Rozo et al., 2010) investigates these same issues within the
context of stacked weak lensing mass estimates.Comment: 11 pages, 8 figures; comments welcom
Astrophysical properties of binary star clusters in the Small Magellanic Cloud
To study the evolution of binary star clusters we have imaged 7 systems in
the Small Magellanic Cloud with SOAR 4-m telescope using B and V filters. The
sample contains pairs with well-separated components (d < 30 pc) as well as
systems that apparently merged, as evidenced by their unusual structures. By
employing isochrone fittings to their CMDs we have determined reddening, age
and metallicity and by fitting King models to their radial stellar density
profile we have estimated core radius. Disturbances of the density profile are
interpreted as an evidence of interaction. Circunstances as distances between
components and their age difference are addressed in terms of the timescales
involved to access the physical connection of the system. In two cases the age
difference is above 50 Myr, which suggests chance alignment, capture or
sequential star formation.Comment: 4 pages, 1 figure. To appear in online version of Proc. IAU Symp. 266
(Star clusters), eds. R. de Grijs and J. Lepin
Karyological analysis of Proechimys cuvieri and Proechimys guyannensis (Rodentia, Echimyidae) from central Amazon
The aim was to characterize the karyotype of rodents of the genus Proechimys from three localities in the central Brazilian Amazon, in the search for new markers that might shed light on our understanding of the taxonomy and evolutionary history of this taxon. Two karyotypes were found, viz., 2n = 28, FN = 46 in individuals from the NRSP (Cuieiras River) and REMAN (Manaus), and 2n = 46, FN = 50 in individuals from the Balbina Hydroelectric Plant. While individuals with the karyotype with 2n = 28 chromosomes were morphologically associated with Proechimys cuvieri, their karyotype shared similarities with those of the same diploid number in two other regions. Although three karyotypes are described for Proechimys cuvieri, no geographic distribution pattern that defined a cline could be identified. Based on the morphological examination of voucher specimens and additional results from molecular analysis, the karyotype with 2n = 46 and FN = 50 could be associated with P. guyannensis
Rotation curves and dynamical masses of MaNGA barred galaxies
In this paper we analyse a sample of 46 barred galaxies of MaNGA. Our goal is to investigate the stellar kinematics of these galaxies and obtain their rotation curves. Additionally, we aim to derive the total stellar and dynamical masses, as well as the maximum rotation velocity, in order to examine their distributions and scaling relations. Using the Pipe3D dataproducts publicly available we obtained the rotation curves, which were fitted considering two components of an axisymmetric Miyamoto–Nagai gravitational potential. We found a wide range of the maximum rotation velocities (117–340 km s−1), with a mean value of 200 km s−1. In addition we found that the total stellar and dynamical masses are in the range of log(Mstar/M☉) = 10.1−11.5, with a mean value of log(Mstar/M☉) = 10.8, and log(Mdyn/M☉) = 10.4−12.0, with a mean value of log(Mdyn/M☉) = 11.1, respectively. We found a strong correlation between dynamical mass and maximum velocity, between maximum velocity and magnitude, and between stellar mass and maximum velocity. According to these results, barred galaxies exhibit similar behaviour to that of normal spiral galaxies with respect to these relations, as well as in terms of the distribution of their dynamical mass and maximum rotation velocity. However, we found that the distribution of stellar masses of barred galaxies is statistically different from other samples including non-barred galaxies. Finally, analysing the galaxies that show nuclear activity, we find no difference with the rotation curves of normal galaxies.Fil: Schmidt, Eduardo Osvaldo. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Mast, Damian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; ArgentinaFil: Gaspar, Gaia. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Weidmann, Walter Alfredo. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentin
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