5,122 research outputs found
PopStar Evolutionary Synthesis Models II: Optical emission-line spectra from Giant H{\sc ii} regions
This is the second paper of a series reporting the results from the PopStar
evolutionary synthesis models. Here we present synthetic emission line spectra
of H{\sc ii} regions photoionized by young star clusters, for seven values of
cluster masses and for ages between 0.1 and 5.2 Myr. The ionizing Spectral
Energy Distributions (SEDs) are those obtained by the PopStar code
\citep*{mgb09} for six different metallicities, with a very low metallicity
set, Z=0.0001, not included in previous similar works. We assume that the
radius of the H{\sc ii} region is the distance at which the ionized gas is
deposited by the action of the mechanical energy of the winds and supernovae
from the central ionizing young cluster. In this way the ionization parameter
is eliminated as free argument, since now its value is obtained from the
cluster physical properties (mass, age and metallicity) and from the gaseous
medium characteristics (density and abundances). We discuss our results and
compare them with those from previous models and also with a large and data set
of giant H{\sc ii} regions for which abundances have been derived in a
homogeneous manner. The values of the [OIII] lines (at 4363,
4959, 5007\AA) in the lowest metallicity nebulae are found to be very weak and
similar to those coming from very high metallicity regions (solar or
over-solar). Thus, the sole use of the oxygen lines is not enough to
distinguish between very low and very high metallicity regions. In these cases
we emphasize the need of the additional support of alternative metallicity
tracers, like the [SIII] lines in the near-\textit{IR}.Comment: 20 pages, 26 figures, accepted for publication in MNRAS Main Journa
AgrupaciĂłn robusta de Bancos en Argentina
The purpose of this paper is to classify and characterize 64 banks, active as of 2010 in Argentina, by means of robust techniques used on information gathered during the period 2001-2010. Based on the strategy criteria established in (Wang 2007) and (Werbin 2010), seven variables were selected. In agreement with bank theory, four “natural” clusters were obtained, named “Personal”, “Commercial”, “Typical” and “Other banks”. In order to understand this grouping, projection pursuit based robust principal component analysis was conducted on the whole set showing that essentially three variables can be attributed the formation of different clusters. In order to reveal each group inner structure, we used R package mclust to fit a finite Gaussian mixture to the data. This revealed approximately a similar component structure, granting a common principal components analysis as in (Boente and Rodrigues, 2002). This allowed us to identify three variables which suffice for grouping and characterizing each cluster. Boente’s influence measures were used to detect extreme cases in the common principal components analysis.El propĂłsito de este documento es clasificar y caracterizar 64 bancos, activos en 2010 en la Argentina, mediante tĂ©cnicas robustas utilizadas con informaciĂłn para el perĂodo 2001-2010. En base a los criterios de estrategia establecidos en (Wang 2007) y (Werbin 2010), se seleccionaron siete variables. De acuerdo con la teorĂa bancaria, se obtuvieron cuatro conglomerados "naturales", denominados "Personal", "Comercial", "TĂpico" y "Otros bancos". Para comprender este agrupamiento, se utilizĂł el todo el conjunto de banco y se realizĂł un análisis de los componentes principales basado en la proyecciĂłn, que mostrĂł que esencialmente tres variables pueden atribuirse a la formaciĂłn de diferentes agrupaciones. A fin de revelar la estructura interna de cada grupo, utilizamos el paquete R mclust para ajustar una mezcla gaussiana finita a los datos. Esto revelĂł aproximadamente una estructura de componentes similar, lo que garantiza un análisis de componentes principales comunes como en (Boente y Rodrigues, 2002). Esto nos permitiĂł identificar tres variables que son suficientes para agrupar y caracterizar cada cluster. Las medidas de influencia de Boente se utilizaron para detectar casos extremos en el análisis de componentes principales comunes
A jade pished hand-axe from Tubino's Cection (Valencina de la ConcepciĂłn Local Museum, Sevilla, Spain)
A pished axe donated to the Valencina de la ConcepciĂłn Museum (Seville, Spain) in November 2010, and that had belonged to Francisco MarĂa Tubino y Oliva's (1833-1888) personal clection, is studied. Although the exact provenance of this object is unknown, there are reasons to think that it might have been found on some archaáş˝ogical site of the Seville province. Through the application of two different analytical techniques (XRD, DCÎĽRS), this axe is identified as a jade-jadeite of purity above 95 ml%, which necessarily implies it came from the Alps. In the conclusions a discussion of this artifact is made in terms of long distance contact in Iberian Late Prehistory.Peer Reviewe
The massive stellar content in NGC604 and its evolutionary state
The ultraviolet resonance wind stellar lines, the nebular optical emission
lines and the higher order terms of the Balmer series and HeI absorption lines
detected in the spectra of NGC 604 are interpreted using evolutionary models
optimized for young star forming regions. The evolutionary state and the
massive stellar content of the region is derived in a self-consistent way.
The three techniques applied suggest that the central ionizing cluster in NGC
604 is very young, 3 Myr old, and that the stars in the cluster were formed in
an instantaneous burst following a Salpeter or flatter IMF, having stars more
massive that 80 Msol. The stellar cluster is able to provide most of the
ionizing photons needed to photoionize the whole nebula, and the wind power to
form the central shell structure where the cluster core is located. The stellar
cluster is affected by an extinction similar to the average extinction that
affects the ionized gas. The estimated number of massive stars in the cluster
is also in agreement with that derived from previous studies based on the
detection of individual stars. The results that we present here support the use
of these techniques for the interpretation of the integrated light of more
distant star forming regionsComment: To be published in MNRAS. 17 pages and 17 figure
Factorizing the time evolution operator
There is a widespread belief in the quantum physical community, and in
textbooks used to teach Quantum Mechanics, that it is a difficult task to apply
the time evolution operator Exp{-itH/h} on an initial wave function. That is to
say, because the hamiltonian operator generally is the sum of two operators,
then it is a difficult task to apply the time evolution operator on an initial
wave function f(x,0), for it implies to apply terms operators like (a+b)^n. A
possible solution of this problem is to factorize the time evolution operator
and then apply successively the individual exponential operator on the initial
wave function. However, the exponential operator does not directly factorize,
i. e. Exp{a+b} is not equal to Exp{a}Exp{b}. In this work we present a useful
procedure for factorizing the time evolution operator when the argument of the
exponential is a sum of two operators, which obey specific commutation
relations. Then, we apply the exponential operator as an evolution operator for
the case of elementary unidimensional potentials, like the particle subject to
a constant force and the harmonic oscillator. Also, we argue about an apparent
paradox concerning the time evolution operator and non-spreading wave packets
addressed previously in the literature.Comment: 24 pages; added references; one figure change
Filling in the gaps in biowaste biorefineries : The use of the solid residue after enzymatic hydrolysis for the production of biopesticides through solid-state fermentation
Altres ajuts: acords transformatius de la UABAlternative production processes using waste are necessary to preserve non-renewable resources and prevent scarcity of materials for future generations. Biowaste, the organic fraction of municipal solid waste, is abundant and easily available. It can be fractionated into building blocks for which fermentative processes can be designed. By using solid-state fermentation, this paper proposes a method of valorizing biowaste's residual solid fraction after enzymatic hydrolysis. In a 22 L bioreactor, two digestates from anaerobic digestion processes were evaluated as cosubstrates to modify the acidic pH of the solid residue after enzymatic hydrolysis and promote the growth of the bacterial biopesticide producer Bacillus thuringiensis. Regardless of the cosubstrate used, the final microbial populations were similar indicating microbial specialization. The final product contained 4 Ă— 10 spores per gram of dry matter and also crystal proteins of Bacillus thuringiensis var israelensis, which have insecticidal activity against pests. This method allows for the sustainable use of all materials liberated during the enzymatic hydrolysis of biowaste, including residual solids
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