21,828 research outputs found
Photometry and dynamics of the minor mergers AM\,1228-260 and AM\,2058-381
We investigate interaction effects on the dynamics and morphology of the
galaxy pairs AM\,2058-381 and AM\,1228-260. This work is based on images
and long-slit spectra obtained with the Gemini Multi-Object Spectrograph at the
Gemini South Telescope. The luminosity ratio between the main (AM\,2058A) and
secondary (AM\,2058B) components of the first pair is a factor of 5,
while for the other pair, the main (AM\,1228A) component is 20 times more
luminous than the secondary (AM\,1228B). The four galaxies have pseudo-bulges,
with a S\'ersic index . Their observed radial velocities profiles (RVPs)
present several irregularities. The receding side of the RVP of AM\,2058A is
displaced with respect to the velocity field model, while there is a strong
evidence that AM\,2058B is a tumbling body, rotating along its major axis. The
RVPs for AM\,1228A indicate a misalignment between the kinematic and
photometric major axes. The RVP for AM\,1228B is quite perturbed, very likely
due to the interaction with AM\,1228A. NFW halo parameters for AM\,2058A are
similar to those of the Milky Way and M\,31. The halo mass of AM\,1228A is
roughly 10\% that of AM\,2058A. The mass-to-light (M/L) of AM\,2058 agrees with
the mean value derived for late-type spirals, while the low M/L for AM\,1228A
may be due to the intense star formation ongoing in this galaxy.Comment: 20 pages, 10 figures, accepted for publication in MNRA
Propagation of generalized vector Helmholtz-Gauss beams through paraxial optical systems
We introduce the generalized vector Helmholtz-Gauss (gVHzG) beams that constitute a general family of localized beam solutions of the Maxwell equations in the paraxial domain. The propagation of the electromagnetic components through axisymmetric ABCD optical systems is expressed elegantly in a coordinate-free and closed-form expression that is fully characterized by the transformation of two independent complex beam parameters. The transverse mathematical structure of the gVHzG beams is form-invariant under paraxial transformations. Any paraxial beam with the same waist size and transverse spatial frequency can be expressed as a superposition of gVHzG beams with the appropriate weight factors. This formalism can be straightforwardly applied to propagate vector Bessel-Gauss, Mathieu-Gauss, and Parabolic-Gauss beams, among others
Factors associated with postharvest ripening heterogeneity of "Hass" avocados (Persea americana Mill)
Indexación: Web of ScienceIntroduction. 'Hass' is the main avocado cultivar commercialized worldwide. The extended flowering period, very low percentage of fruit set and inability to ripen on the tree renders the fruit heterogeneous and unpredictable during postharvest management. The "triggered" and "ready-to-eat" growing markets for 'Hass' avocados are affected by the variable postharvest ripening or ripening heterogeneity which creates severe logistical problems for marketers and inconsistent quality delivery to consumers. Synthesis. The dry matter content, the current avocado harvest index that correlates very well with oil content, has been extensively used to harvest 'Hass' avocados to comply with the minimum standards to guarantee consumer satisfaction. However, previous work and empirical experience demonstrate that dry matter does not correlate on a fruit-to-fruit basis with time to reach edible ripeness. Thus, avocados of very different ages are harvested from individual trees, resulting in heterogeneous postharvest ripening of fruit within a specific batch. Several preharvest factors related to environmental and growing conditions and crop management as well as postharvest technology strategies influence the observed variability of postharvest ripening. Conclusion. Modern approaches based on studying the composition of individual fruits displaying contrasting postharvest ripening behavior, combined with non-destructive phenotyping techniques, seem to offer practical solutions for the fresh supply chain of avocados to sort fruit based on their ripening capacity.http://www.pubhort.org/fruits/2016/5/fruits160045.ht
Localization of Two-dimensional Electron Gas in LaAlO3/SrTiO3 Heterostructures
We report strong localization of 2D electron gas in LaAlO3 / SrTiO3 epitaxial
thin-film heterostructures grown on (LaAlO3)0.3-(Sr2AlTaO3)0.7 substrates by
using pulsed laser deposition with in-situ reflection high-energy electron
diffraction. Using longitudinal and transverse magnetotransport measurements,
we have determined that disorder at the interface influences the conduction
behavior, and that increasing the carrier concentration by growing at lower
oxygen partial pressure changes the conduction from strongly localized at low
carrier concentration to metallic at higher carrier concentration, with
indications of weak localization. We interpret this behavior in terms of a
changing occupation of Ti 3d bands near the interface, each with a different
spatial extent and susceptibility to localization by disorder, and differences
in carrier confinement due to misfit strain and point defects.Comment: 12 pages, 4 figure
Gas Kinematics and Excitation in the Filamentary IRDC G035.39-00.33
Some theories of dense molecular cloud formation involve dynamical
environments driven by converging atomic flows or collisions between
preexisting molecular clouds. The determination of the dynamics and physical
conditions of the gas in clouds at the early stages of their evolution is
essential to establish the dynamical imprints of such collisions, and to infer
the processes involved in their formation. We present multi-transition 13CO and
C18O maps toward the IRDC G035.39-00.33, believed to be at the earliest stages
of evolution. The 13CO and C18O gas is distributed in three filaments
(Filaments 1, 2 and 3), where the most massive cores are preferentially found
at the intersecting regions between them. The filaments have a similar
kinematic structure with smooth velocity gradients of ~0.4-0.8 km s-1 pc-1.
Several scenarios are proposed to explain these gradients, including cloud
rotation, gas accretion along the filaments, global gravitational collapse, and
unresolved sub-filament structures. These results are complemented by HCO+,
HNC, H13CO+ and HN13C single-pointing data to search for gas infall signatures.
The 13CO and C18O gas motions are supersonic across G035.39-00.33, with the
emission showing broader linewidths toward the edges of the IRDC. This could be
due to energy dissipation at the densest regions in the cloud. The average H2
densities are ~5000-7000 cm-3, with Filaments 2 and 3 being denser and more
massive than Filament 1. The C18O data unveils three regions with high CO
depletion factors (f_D~5-12), similar to those found in massive starless cores.Comment: 20 pages, 14 figures, 6 tables, accepted for publication in MNRA
An exploratory study: Corporate social responsibility perceptions in Guinea-Bissau and Ivory Coast
Corporate Social Responsibility (CSR) is now crucial to enhance long-term competitiveness. CSR is also linked with several strategic business dimensions such as innovation, performance, and competitive success. However, most of the available studies conducted at the moment use samples from developed countries in America and Europe, and insufficient attention has been given to less developed countries, particularly in Africa.
Taking into account that the current models to understand and measure the concept of CSR, and to determine how to obtain competitive advantage through responsible business behaviour, have not yet been applied to Africa, this article is a first step to fill the gap. Based on recently published models addressing the above-mentioned variables, this paper aims to study CRS through the application of a questionnaire to managers in two countries in West Africa: Guinea-Bissau and the Ivory Coast. The main goal of this exploratory study was the understanding of the current situation of CSR managers´ perceptions in both countries. For this purpose, the paper uses an overall scale to examine the different theoretical dimensions reflecting CSR: social, economic, and environmental dimensions. The results show that there is a generally positive perception of the CSR elements, although the emphasis is given to economic issues and the social issues related to human resources, training and empowerment of employees and leadership skills, among others. As conclusion the study points out the role of managers in promoting a culture of social innovation by focusing on the CSR philosophy.info:eu-repo/semantics/publishedVersio
An equatorial ultra iron-poor star identified in BOSS
We report the discovery of SDSS J131326.89-001941.4, an ultra iron-poor red
giant star ([Fe/H] ~ -4.3) with a very high carbon abundance ([C/Fe]~ +2.5).
This object is the fifth star in this rare class, and the combination of a
fairly low effective temperature (Teff ~ 5300 K), which enhances line
absorption, with its brightness (g=16.9), makes it possible to measure the
abundances of calcium, carbon and iron using a low-resolution spectrum from the
Sloan Digital Sky Survey. We examine the carbon and iron abundance ratios in
this star and other similar objects in the light of predicted yields from
metal-free massive stars, and conclude that they are consistent. By way of
comparison, stars with similarly low iron abundances but lower carbon-to-iron
ratios deviate from the theoretical predictions.Comment: 6 pages, 4 figures, accepted for publication in A&
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