307 research outputs found
FLORA LIQUÉNICA EPIFÍTICA DE CÁDIZ. l. LOS ALCORNOCALES DE LAS SIERRAS DE ALGECIRAS
This first contribution to the lichen epiphytic flora of the province of Cádiz includes ecological data and comments on literature records from this and nearby territories (portuguese Algarve and the spanish province of Huelva). The species distribution approximation is drawn based on bioclimate of several stations. The catalogue includes records of interest, either because they are new for the spanish lichen flora or because of their chorological relevance. among them: Buellia jorgei G. Samp., Caloplaca pollini (Massal.) Jatta, Fuscidea cyathoides (Ach.) V. Wirth & Vezda, Lecanactis patellarioides (Nyl.) Vainio, Lecanora balearicaRealizamos una primera aportaci6n al conocimiento de la flora epifítica de la provincia de Cádiz. Se incluyen datos ecológicos y se comentan las citas bibliográficas de éste y otros territorios próximos (Algarve portugués y provincia española de Huelva). Presentamos una aproximación a la distribución de las especies en función de las variables bioclimáticas de las distintas estaciones. Entre los táxones del catálogo se incluyen algunos interesantes por ser novedad para la flora española o por su significación corológica, entre ellos destacamos: Buellia jorgei G. Samp., Caloplaca pollinii (Massal.) Jatta, Fuscidea cyathoides (Ach.) V. Wirth & Vézda, Lecanactis patellarioides (Nyl.) Vainio, Lecanora balearica Crespo & Llimona, Maronea constans (Nyl.) Hepp., Parmotrema austrosinense (Zahlbr.) Hale, Parmotrema hypoleucinum (Steiner) Hale, Parmotrema stupeum (Taylor) Hale, Pertusaria caesioalba (Flotow) Nyl., Pertusaria dalmatita Erichsen, Pertusaria ficorum Zahlbr., Pertusaria lecanorodes Erichsen, Pertusaria maximiliana Klem., Pyrrhospora quernea (Dickson) Koerber, Rinodina pruinella Bagl. y Sorothelia confluens Koerber. De todos los táxones catalogados se menciona los pliegos MAF lich testigo
Risk Management at the Institute of Chemistry of the State University of Rio De Janeiro
The present work aims to evaluate the perception of students in relation to the risk of activities carried out in the laboratories (academic and research) of the Institute of Chemistry of the State University of Rio de Janeiro. In laboratories, equipment operating under pressure and hazardous chemical compounds can harm human health or result in accidents, some fatal. Risk assessments were carried out in the laboratories, using nationally accepted risk management standards, to identify the risks that the laboratories are exposed to in relation to fire and explosion safety, as well as to understand the history, causes and consequences of previous accidents. In a simplified way, it was concluded that the perception of risk by students and employees of the Institute of Chemistry is low. Thus, the need for improvements in laboratories was pointed out, to mitigate or eliminate existing risks, in addition to help foster a strong safety culture, through which laboratory risks can be identified and properly managed by all working in such environments. Consequently, the frequency and severity of laboratory accidents is expected to be reduced or even eliminated
Confinement and soliton solutions in the SL(3) Toda model coupled to matter fields
We consider an integrable conformally invariant two dimensional model
associated to the affine Kac-Moody algebra SL(3). It possesses four scalar
fields and six Dirac spinors. The theory does not possesses a local Lagrangian
since the spinor equations of motion present interaction terms which are
bilinear in the spinors. There exists a submodel presenting an equivalence
between a U(1) vector current and a topological current, which leads to a
confinement of the spinors inside the solitons. We calculate the one-soliton
and two-soliton solutions using a procedure which is a hybrid of the dressing
and Hirota methods. The soliton masses and time delays due to the soliton
interactions are also calculated. We give a computer program to calculate the
soliton solutions.Comment: plain LaTeX, 37 page
Affine Toda model coupled to matter and the string tension in QCD
The affine Toda model coupled to matter (ATM) is shown to describe
various features, such as the spectrum and string tension, of the low-energy
effective Lagrangian of QCD (one flavor and colors). The
corresponding string tension is computed when the dynamical quarks are in the
{\sl fundamental} representation of SU(N) and in the {\sl adjoint}
representation of SU(2).Comment: LaTex, 10 pages. Revised version to appear in Phys. Rev.
Multiscale magnetic underdense regions on the solar surface: Granular and Mesogranular scales
The Sun is a non-equilibrium dissipative system subjected to an energy flow
which originates in its core. Convective overshooting motions create
temperature and velocity structures which show a temporal and spatial
evolution. As a result, photospheric structures are generally considered to be
the direct manifestation of convective plasma motions. The plasma flows on the
photosphere govern the motion of single magnetic elements. These elements are
arranged in typical patterns which are observed as a variety of multiscale
magnetic patterns. High resolution magnetograms of quiet solar surface revealed
the presence of magnetic underdense regions in the solar photosphere, commonly
called voids, which may be considered a signature of the underlying convective
structure. The analysis of such patterns paves the way for the investigation of
all turbulent convective scales from granular to global. In order to address
the question of magnetic structures driven by turbulent convection at granular
and mesogranular scales we used a "voids" detection method. The computed voids
distribution shows an exponential behavior at scales between 2 and 10 Mm and
the absence of features at 5-10 Mm mesogranular scales. The absence of
preferred scales of organization in the 2-10 Mm range supports the multiscale
nature of flows on the solar surface and the absence of a mesogranular
convective scale
Comparison of Recent SnIa datasets
We rank the six latest Type Ia supernova (SnIa) datasets (Constitution (C),
Union (U), ESSENCE (Davis) (E), Gold06 (G), SNLS 1yr (S) and SDSS-II (D)) in
the context of the Chevalier-Polarski-Linder (CPL) parametrization
, according to their Figure of Merit (FoM), their
consistency with the cosmological constant (CDM), their consistency
with standard rulers (Cosmic Microwave Background (CMB) and Baryon Acoustic
Oscillations (BAO)) and their mutual consistency. We find a significant
improvement of the FoM (defined as the inverse area of the 95.4% parameter
contour) with the number of SnIa of these datasets ((C) highest FoM, (U), (G),
(D), (E), (S) lowest FoM). Standard rulers (CMB+BAO) have a better FoM by about
a factor of 3, compared to the highest FoM SnIa dataset (C). We also find that
the ranking sequence based on consistency with CDM is identical with
the corresponding ranking based on consistency with standard rulers ((S) most
consistent, (D), (C), (E), (U), (G) least consistent). The ranking sequence of
the datasets however changes when we consider the consistency with an expansion
history corresponding to evolving dark energy crossing the
phantom divide line (it is practically reversed to (G), (U), (E), (S),
(D), (C)). The SALT2 and MLCS2k2 fitters are also compared and some peculiar
features of the SDSS-II dataset when standardized with the MLCS2k2 fitter are
pointed out. Finally, we construct a statistic to estimate the internal
consistency of a collection of SnIa datasets. We find that even though there is
good consistency among most samples taken from the above datasets, this
consistency decreases significantly when the Gold06 (G) dataset is included in
the sample.Comment: 13 pages, 9 figures. Included recently released SDSS-II dataset.
Improved presentation. Main results unchanged. The mathematica files and
datasets used for the production of the figures may be downloaded from
http://leandros.physics.uoi.gr/datacomp
Higher Grading Conformal Affine Toda Teory and (Generalized) Sine-Gordon/Massive Thirring Duality
Some properties of the higher grading integrable generalizations of the
conformal affine Toda systems are studied. The fields associated to the
non-zero grade generators are Dirac spinors. The effective action is written in
terms of the Wess-Zumino-Novikov-Witten (WZNW) action associated to an affine
Lie algebra, and an off-critical theory is obtained as the result of the
spontaneous breakdown of the conformal symmetry. Moreover, the off-critical
theory presents a remarkable equivalence between the Noether and topological
currents of the model. Related to the off-critical model we define a real and
local Lagrangian provided some reality conditions are imposed on the fields of
the model. This real action model is expected to describe the soliton sector of
the original model, and turns out to be the master action from which we uncover
the weak-strong phases described by (generalized) massive Thirring and
sine-Gordon type models, respectively. The case of any (untwisted) affine Lie
algebra furnished with the principal gradation is studied in some detail.
The example of is presented explicitly.Comment: 28 pages, JHEP styl
A parametrization of the growth index of matter perturbations in various Dark Energy models and observational prospects using a Euclid-like survey
We provide exact solutions to the cosmological matter perturbation equation
in a homogeneous FLRW universe with a vacuum energy that can be parametrized by
a constant equation of state parameter and a very accurate approximation
for the Ansatz . We compute the growth index \gamma=\log
f(a)/\log\Om_m(a), and its redshift dependence, using the exact and
approximate solutions in terms of Legendre polynomials and show that it can be
parametrized as in most cases. We then
compare four different types of dark energy (DE) models: CDM, DGP,
and a LTB-large-void model, which have very different behaviors at
z\gsim1. This allows us to study the possibility to differentiate between
different DE alternatives using wide and deep surveys like Euclid, which will
measure both photometric and spectroscopic redshifts for several hundreds of
millions of galaxies up to redshift . We do a Fisher matrix analysis
for the prospects of differentiating among the different DE models in terms of
the growth index, taken as a given function of redshift or with a principal
component analysis, with a value for each redshift bin for a Euclid-like
survey. We use as observables the complete and marginalized power spectrum of
galaxies and the Weak Lensing (WL) power spectrum. We find that, using
, one can reach (2%, 5%) errors in , and (4%, 12%) errors in
, while using WL we get errors at least twice as large.
These estimates allow us to differentiate easily between DGP, models and
CDM, while it would be more difficult to distinguish the latter from a
variable equation of state parameter or LTB models using only the growth
index.}Comment: 29 pages, 7 figures, 6 table
A new approach to cosmological perturbations in f(R) models
We propose an analytic procedure that allows to determine quantitatively the
deviation in the behavior of cosmological perturbations between a given f(R)
modified gravity model and a LCDM reference model. Our method allows to study
structure formation in these models from the largest scales, of the order of
the Hubble horizon, down to scales deeply inside the Hubble radius, without
employing the so-called "quasi-static" approximation. Although we restrict our
analysis here to linear perturbations, our technique is completely general and
can be extended to any perturbative order.Comment: 21 pages, 2 figures; Revised version according to reviewer's
suggestions; Typos corrected; Added Reference
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