1,495 research outputs found
Fitting isochrones to open cluster photometric data III. Estimating metallicities from UBV photometry
The metallicity is a critical parameter that affects the correct
determination fundamental characteristics stellar cluster and has important
implications in Galactic and Stellar evolution research. Fewer than 10 % of the
2174 currently catalog open clusters have their metallicity determined in the
literature. In this work we present a method for estimating the metallicity of
open clusters via non-subjective isochrone fitting using the cross-entropy
global optimization algorithm applied to UBV photometric data. The free
parameters distance, reddening, age, and metallicity simultaneously determined
by the fitting method. The fitting procedure uses weights for the observational
data based on the estimation of membership likelihood for each star, which
considers the observational magnitude limit, the density profile of stars as a
function of radius from the center of the cluster, and the density of stars in
multi-dimensional magnitude space. We present results of [Fe/H] for nine
well-studied open clusters based on 15 distinct UBV data sets. The [Fe/H]
values obtained in the ten cases for which spectroscopic determinations were
available in the literature agree, indicating that our method provides a good
alternative to determining [Fe/H] by using an objective isochrone fitting. Our
results show that the typical precision is about 0.1 dex
CaracterÃsticas das cultivares de trigo recomendadas para cultivo em áreas aptas ao arroz irrigado do Rio Grande do Sul.
bitstream/item/31633/1/comunicado99.pd
Rendimento das cultivares de trigo recomendadas para solos aptos ao cultivo de arroz irrigado em relação à s demais regiões tritÃcolas do Rio Grande do Sul.
M\"obius and twisted graphene nanoribbons: stability, geometry and electronic properties
Results of classical force field geometry optimizations for twisted graphene
nanoribbons with a number of twists varying from 0 to 7 (the case =1
corresponds to a half-twist M\"obius nanoribbon) are presented in this work.
Their structural stability was investigated using the Brenner reactive force
field. The best classical molecular geometries were used as input for
semiempirical calculations, from which the electronic properties (energy
levels, HOMO, LUMO orbitals) were computed for each structure. CI wavefunctions
were also calculated in the complete active space framework taking into account
eigenstates from HOMO-4 to LUMO+4, as well as the oscillator strengths
corresponding to the first optical transitions in the UV-VIS range. The lowest
energy molecules were found less symmetric than initial configurations, and the
HOMO-LUMO energy gaps are larger than the value found for the nanographene used
to build them due to electronic localization effects created by the twisting. A
high number of twists leads to a sharp increase of the HOMO LUMO
transition energy. We suggest that some twisted nanoribbons could form crystals
stabilized by dipolar interactions
Explaining ATLAS and CMS Results Within the Reduced Minimal 3-3-1 model
Recently the ATLAS and CMS collaborations announced the discovery of a higgs
particle with a mass of GeV. The results are mildly consistent with
the Standard Model Higgs boson. However, the combined data from these
collaborations seem to point to an excess in the
channel. In this work we analyze under which conditions this excess may be
plausibly explained within the reduced minimal 3-3-1 model, while being
consistent with bb, WW, ZZ and channels. Moreover, we derive the
properties of the heavy neutral and the doubly charged scalars predicted by the
model. We then conclude that at a scale of a few TeV, this model provides a
good fit to the ATLAS and CMS signal strength measurements, and therefore
stands as an appealing alternative to the standard model.Comment: 23 pages, 9 figures. References adde
Rendimento de grãos e algumas caracterÃsticas agronômicas de cultivares de trigo avaliadas na região de Pelotas-RS, em 2003.
bitstream/item/31641/1/comunicado107.pd
Combining type I and type II seesaw mechanisms in the minimal 3-3-1 model
The minimal 3-3-1 model is perturbative until energies around 4-5TeV, posing
a challenge to generate neutrino masses at eV scale, mainly if one aims to take
advantage of the seesaw mechanism. As a means to circumvent this problem we
propose a modification of the model such that it accommodates the type I and
type II seesaw mechanisms altogether. We show that the conjunction of both
mechanisms yield a neutrino mass expression suppressed by a high power of the
cutoff scale, , in its denominator. With such a suppression term we
naturally obtain neutrino masses at eV scale when is around few TeV. We
also investigate the size of lepton flavor violation through the process .Comment: about 15 pages, no figure
Clarifying the importance of trust in organizations as a component of effective work relationships
WOS:000315028100016 (Nº de Acesso Web of Science)Organizational trust is an important element of an organization's long-term success, as it is a central component of effective work relationships. This study examines the extent to which one's trust in the organization mediates the relationship between three drivers of social exchange relationships and three attitudinal outcomes. The results from a sample of 1,300 manufacturing employees revealed that trust in the organization partially mediated the relationship between perceived supervisor support and turnover intentions, affective organizational commitment and job satisfaction, and fully mediated the relationship between distributive justice and information receiving and these outcomes. This paper extends the empirical literature about the antecedents and consequences of trust in organization, giving special attention to the mediating role of trust in organizations
Comportamento de genótipos de trigo cultivados em dois ecossistemas de terras baixas na metade sul do Rio Grande do Sul.
bitstream/item/31635/1/comunicado100.pd
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