642 research outputs found
Haro15: Is it actually a low metallicity galaxy?
We present a detailed study of the physical properties of the nebular
material in multiple knots of the blue compact dwarf galaxy Haro 15. Using long
slit and echelle spectroscopy, obtained at Las Campanas Observatory, we study
the physical conditions (electron density and temperature), ionic and total
chemical abundances of several atoms, reddening and ionization structure. The
latter was derived by comparing the oxygen and sulphur ionic ratios to their
corresponding observed emission line ratios (the eta and eta' plots) in
different regions of the galaxy. Applying direct and empirical methods for
abundance determination, we perform a comparative analysis between these
regions.Comment: (Poster paper) 2 pages, 2 figure
Internal kinematic and physical properties in a BCD galaxy: Haro 15 in detail
We present a detailed study of the kinematic and physical properties of the
ionized gas in multiple knots of the blue compact dwarf galaxy Haro 15. Using
echelle and long slit spectroscopy data, obtained with different instruments at
Las Campanas Observatory, we study the internal kinematic and physical
conditions (electron density and temperature), ionic and total chemical
abundances of several atoms, reddening and ionization structure. Applying
direct and empirical methods for abundance determination, we perform a
comparative analysis between these regions and in their different components.
On the other hand, our echelle spectra show complex kinematics in several
conspicuous knots within the galaxy. To perform an in-depth 2D spectroscopic
study we complete this work with high spatial and spectral resolution
spectroscopy using the Integral Field Unit mode on the Gemini Multi-Object
Spectrograph instrument at the Gemini South telescope. With these data we are
able to resolve the complex kinematical structure within star forming knots in
Haro 15 galaxy.Comment: 6 pages, 2 figures, IX Scientific Meeting of the Spanish Astronomical
Society held on September 13-17, 2010, in Madrid, Spai
Equilibrium statistical mechanics for single waves and wave spectra in Langmuir wave-particle interaction
Under the conditions of weak Langmuir turbulence, a self-consistent
wave-particle Hamiltonian models the effective nonlinear interaction of a
spectrum of M waves with N resonant out-of-equilibrium tail electrons. In order
to address its intrinsically nonlinear time-asymptotic behavior, a Monte Carlo
code was built to estimate its equilibrium statistical mechanics in both the
canonical and microcanonical ensembles. First the single wave model is
considered in the cold beam/plasma instability and in the O'Neil setting for
nonlinear Landau damping. O'Neil's threshold, that separates nonzero
time-asymptotic wave amplitude states from zero ones, is associated to a second
order phase transition. These two studies provide both a testbed for the Monte
Carlo canonical and microcanonical codes, with the comparison with exact
canonical results, and an opportunity to propose quantitative results to
longstanding issues in basic nonlinear plasma physics. Then the properly
speaking weak turbulence framework is considered through the case of a large
spectrum of waves. Focusing on the small coupling limit, as a benchmark for the
statistical mechanics of weak Langmuir turbulence, it is shown that Monte Carlo
microcanonical results fully agree with an exact microcanonical derivation. The
wave spectrum is predicted to collapse towards small wavelengths together with
the escape of initially resonant particles towards low bulk plasma thermal
speeds. This study reveals the fundamental discrepancy between the long-time
dynamics of single waves, that can support finite amplitude steady states, and
of wave spectra, that cannot.Comment: 15 pages, 7 figures, to appear in Physics of Plasma
High velocity blue-shifted FeII absorption in the dwarf star-forming galaxy PHL293B: Evidence for a wind driven supershell?
X-shooter and ISIS WHT spectra of the starforming galaxy PHL 293B also known
as A2228-00 and SDSS J223036.79-000636.9 are presented in this paper.
We find broad (FWHM = 1000km/s) and very broad (FWZI = 4000km/s) components
in the Balmer lines, narrow absorption components in the Balmer series
blueshifted by 800km/s, previously undetected FeII multiplet (42) absorptions
also blueshifted by 800km/s, IR CaII triplet stellar absorptions consistent
with [Fe/H] < -2.0 and no broad components or blushifted absorptions in the HeI
lines. Based on historical records, we found no optical variability at the 5
sigma level of 0.02 mag between 2005 and 2013 and no optical variability at the
level of 0.1mag for the past 24 years.
The lack of variability rules out transient phenomena like luminous blue
variables or SN IIn as the origin of the blue shifted absorptions of HI and
FeII. The evidence points to either a young and dense expanding supershell or a
stationary cooling wind, in both cases driven by the young cluster wind.Comment: Accepted for publication in MNRAS; 15 pages, 10 figure
11th European Headache Federation Congress jointly with 31st Congress of the Italian Society for the Study of Headaches : Rome, Italy. 01-03 December 2017
. Aims of the study were explore the relationship between peripheral chromatic and central visual dysfunction evaluating also the presence of functional receptor impairment in patients with migraine, with and without aura examined interictally
Decomposicao da evolucao da desigualdade de renda no Brasil em efeitos idade, periodo e coorte / Explaining income inequality in Brazil: age, period and cohort effects
A partir dos microdados da Pesquisa Nacional por Amostra de DomicĂlios (PNAD), este trabalho tem como objetivo contribuir para o entendimento da evolução da desigualdade de renda no Brasil, de 1981 a 2001, ao identificar, sob algumas hipĂłteses, os efeitos idade, perĂodo e coorte. O mĂ©todo de identificação utilizado, proposto por Deaton e Paxson (1994), permitiu estimar esses efeitos para indicadores de desigualdade Theil-T com base na renda familiar de todas as fontes e na renda familiar do trabalho principal para a amostra total dos chefes de famĂlia e por grupo de escolaridade.
Os principais resultados encontrados mostram que: a) a desigualdade de renda aumenta para as gerações mais novas, sendo esse aumento mais acentuado para a medida de renda do trabalho principal; b) o efeito coorte nĂŁo Ă© significativo para famĂlias com chefes de mesma escolaridade, o que sugere que o crescimento da desigualdade de renda para as gerações mais novas possa refletir um aumento da escolaridade das gerações mais novas em relação Ă s antigas; c) a desigualdade de rendimentos do trabalho principal cresce acentuadamente com a idade, sobretudo para os grupos de maior escolaridade, o que Ă© compatĂvel com implicações da teoria do capital humano; d) a desigualdade de renda de todas as fontes tende a se reduzir apĂłs uma certa idade para os grupos de menor escolaridade; e e) há um efeito perĂodo significativo de aumento da desigualdade de renda observado em 1989 e 1993, perĂodos de aguda aceleração inflacionária. /
Using Brazilian household survey data, this paper aims to contribute for a better understanding of the income inequality evolution from 1981 to 2001. This is done by decomposing the time evolution of the income inequality among Brazilian households into age, time and cohort effects. Identification of these effects follows as an application of the method proposed by Deaton and Paxson (1994) to a series of Theil-T inequality indexes of overall family income and earnings for the whole sample of household heads, as well as for schooling groups.
The main results are: a) income and, more pronouncedly, earnings, are more unevenly distributed among families belonging to the youngest generations; b) the cohort effect is not important among families whose heads have similar levels of schooling, which suggests that the rise in inequality among younger cohorts is a result of the increase in schooling levels along the last decades; c) large positive age effects are present, especially for groups with higher schooling levels; d) income inequality tends to decrease after a certain age for groups with low education; and e) peaks in income inequality were observed in 1989 and 1993, probably due to sharp increases in inflation
SCINTILLA A European project for the development of scintillation detectors and new technologies for nuclear security
Europe monitors transits using radiation detectors to prevent illicit
trafficking of nuclear materials. The SCINTILLA project aims to develop a
toolbox of innovative technologies designed to address different usage cases.
This article will review the scope, approach, results of the first benchmark
campaign and future plans of the SCINTILLA project.Comment: To appear on the Proceedings of the 13th ICATPP Conference on
Astroparticle, Particle, Space Physics and Detectors for Physics
Applications, Villa Olmo (Como, Italy), 23--27 October, 2013, to be published
by World Scientific (Singapore
Early out-of-equilibrium beam-plasma evolution
We solve analytically the out-of-equilibrium initial stage that follows the
injection of a radially finite electron beam into a plasma at rest and test it
against particle-in-cell simulations. For initial large beam edge gradients and
not too large beam radius, compared to the electron skin depth, the electron
beam is shown to evolve into a ring structure. For low enough transverse
temperatures, the filamentation instability eventually proceeds and saturates
when transverse isotropy is reached. The analysis accounts for the variety of
very recent experimental beam transverse observations.Comment: to appear in Phys. Rev. Letter
Labor market experience and falling earnings inequality in Brazil: 1995–2012
The Gini coefficient of labor earnings in Brazil fell by nearly a fifth between 1995 and 2012, from 0.50 to 0.41. The decline in other measures of earnings inequality was even larger, with the 90-10 percentile ratio falling by almost 40 percent. Applying micro-econometric decomposition techniques, this study parses out the proximate determinants of this substantial reduction in earnings inequality. Although a falling education premium did play a role, in line with received wisdom, this study finds that a reduction in the returns to labor market experience was a much more important factor driving lower wage disparities. It accounted for 53 percent of the observed decline in the Gini index during the period. Reductions in horizontal inequalities – the gender, race, regional and urban-rural wage gaps, conditional on human capital and institutional variables – also contributed. Two main factors operated against the decline: a greater disparity in wage premia to different sectors of economic activity, and the “paradox of progress”: the mechanical inequality-increasing effect of a more educated labor force when returns to education are convex
Phase transition in the collisionless regime for wave-particle interaction
Gibbs statistical mechanics is derived for the Hamiltonian system coupling
self-consistently a wave to N particles. This identifies Landau damping with a
regime where a second order phase transition occurs. For nonequilibrium initial
data with warm particles, a critical initial wave intensity is found: above it,
thermodynamics predicts a finite wave amplitude in the limit of infinite N;
below it, the equilibrium amplitude vanishes. Simulations support these
predictions providing new insight on the long-time nonlinear fate of the wave
due to Landau damping in plasmas.Comment: 12 pages (RevTeX), 2 figures (PostScript
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