11,561 research outputs found
ChPT parameters from tau-decay data
Using the updated ALEPH V-A spectral function from tau decays, we determine
the lowest spectral moments of the left-right correlator and extract dynamical
information on order parameters of the QCD chiral symmetry breaking.
Uncertainties associated with violations of quark-hadron duality are estimated
from the data, imposing all known short-distance constraints on a
resonance-based parametrization. Employing proper pinched weight functions, we
obtain an accurate determination of the effective chiral couplings L10 and C87
and the dimension-six and -eight contributions in the Operator Product
Expansion.Comment: 5 pages, 3 figures, QCD2015 Montpellie
Effect of agro-climatic conditions on near infrared spectra of extra virgin olive oils
Authentication of extra virgin olive oil requires fast and cost-effective analytical procedures, such as near infrared spectroscopy. Multivariate analysis and chemometrics have been successfully applied in several papers to gather qualitative and quantitative information of extra virgin olive oils from near infrared spectra. Moreover, there are many examples in the literature analysing the effect of agro-climatic conditions on food content, in general, and in olive oil components, in particular. But the majority of these studies considered a factor, a non-numerical variable, containing this meteorological information. The present work uses all the agro-climatic data with the aim of highlighting the linear relationships between them and the near infrared spectra. The study begins with a graphical motivation, continues with a bivariate analysis and, finally, applies redundancy analysis to extend and confirm the previous conclusions.Peer Reviewe
Seasonal dynamic factor analysis and bootstrap inference : application to electricity market forecasting
Year-ahead forecasting of electricity prices is an important issue in the current context of
electricity markets. Nevertheless, only one-day-ahead forecasting is commonly tackled up in
previous published works. Moreover, methodology developed for the short-term does not work
properly for long-term forecasting.
In this paper we provide a seasonal extension of the Non-Stationary Dynamic Factor Analysis,
to deal with the interesting problem (both from the economic and engineering point of view) of
long term forecasting of electricity prices. Seasonal Dynamic Factor Analysis (SeaDFA) allows
to deal with dimensionality reduction in vectors of time series, in such a way that extracts
common and specific components. Furthermore, common factors are able to capture not only
regular dynamics (stationary or not) but also seasonal one, by means of common factors
following a multiplicative seasonal VARIMA(p,d,q)Ă—(P,D,Q)s model.
Besides, a bootstrap procedure is proposed to be able to make inference on all the parameters
involved in the model. A bootstrap scheme developed for forecasting includes uncertainty due
to parameter estimation, allowing to enhance the coverage of forecast confidence intervals.
Concerning the innovative and challenging application provided, bootstrap procedure developed
allows to calculate not only point forecasts but also forecasting intervals for electricity prices
Errores en la sustracciĂłn cometidos por estudiantes universitarios
El manejo adecuado de las operaciones elementales es uno de los objetivos de la enseñanza obligatoria de gran parte de los paĂses del mundo. Referido a ello, la investigaciĂłn muestra que un alto porcentaje de niños de primaria (6-12 años) cometen errores cuando realizan sustracciones (LĂłpez y Sánchez, 2007; Young y O’Shea, 1981). Sin embargo apenas se sabe si esos errores se mantienen en personas adultas. En este trabajo se pretende analizar los tipos de errores que estudiantes universitarios cometen al realizar la sustracciĂłn
Inner and outer star forming regions over the disks of spiral galaxies. I. Sample characterization
Context. The knowledge of abundance distributions is central to understanding
the formation and evolution of galaxies. Most of the relations employed for the
derivation of gas abundances have so far been derived from observations of
outer disk HII regions, despite the known differences between inner and outer
regions. Aims. Using integral field spectroscopy (IFS) observations we aim to
perform a systematic study and comparison of two inner and outer HII regions
samples. The spatial resolution of the IFS, the number of objects and the
homogeneity and coherence of the observations allow a complete characterization
of the main observational properties and differences of the regions. Methods.
We analyzed a sample of 725 inner HII regions and a sample of 671 outer HII
regions, all of them detected and extracted from the observations of a sample
of 263 nearby, isolated, spiral galaxies observed by the CALIFA survey.
Results. We find that inner HII regions show smaller equivalent widths, greater
extinction and luminosities, along with greater values of
[NII]{\lambda}6583/H{\alpha} and [OII]{\lambda}3727/[OIII]{\lambda}5007
emission-line ratios, indicating higher metallicites and lower ionization
parameters. Inner regions have also redder colors and higher photometric and
ionizing masses, although Mion/Mphot is slighty higher for the outer regions.
Conclusions. This work shows important observational differences between inner
and outer HII regions in star forming galaxies not previously studied in
detail. These differences indicate that inner regions have more evolved stellar
populations and are in a later evolution state with respect to outer regions,
which goes in line with the inside-out galaxy formation paradigm.Comment: 16 page
Organic cheese market (RĂo Cuarto, Argentina). Consumer attitudes
The consumer attitudes and buying behaviour to ecological cheese, in RĂo Cuarto city were studied. This research was carried out as a semi -structured survey, based on personal interviews and taste panels. Forty-four percent of the consumers showed willingness to pay up to a 25 to 35 percent premium price for organic foods. Flavour and ecological nature of the product were the chief motivations for buying behaviour.Se estudiĂł mediante encuestas semiestructuradas, la actitud de los consumidores respecto a un queso ecolĂłgico y su valoraciĂłn, en la ciudad de RĂo Cuarto. El 44 p.100 de los consumidores manifestĂł intenciĂłn de pagar desde un 25 a 35 p.100 de sobreprecio por el producto ecolĂłgico. Entre las principales motivaciones para la compra están el sabor (91 p.100) y la naturaleza ecolĂłgica del producto (81 p.100)
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