1,154 research outputs found
Planetary Nebulae distances in GAIA DR2
Context: Planetary Nebula distance scales often suffer for model dependent
solutions. Model independent trigonometric parallaxes have been rare. Space
based trigonometric parallaxes are now available for a larger sample using the
second data release of GAIA. Aims: We aim to derive a high quality approach for
selection criteria of trigonometric parallaxes for planetary nebulae and
discuss possible caveats and restrictions in the use of this data release.
Methods: A few hundred sources from previous distance scale surveys were
manually cross identified with data from the second GAIA data release (DR2) as
coordinate based matching does not work reliable. The data are compared with
the results of previous distance scales and to the results of a recent similar
study, which was using the first data release GAIA DR1. Results: While the few
available previous ground based and HST trigonometric parallaxes match
perfectly to the new data sets, older statistical distance scales, reaching
larger distances, do show small systematic differences. Restricting to those
central stars, were photometric colors of GAIA show a negligible contamination
by the surrounding nebula, the difference is negligible for radio flux based
statistical distances, while those derived from H-alpha surface brightness
still show minor differences. The DR2 study significantly improves the previous
recalibration of the statistical distance scales using DR1/TGAS.Comment: 4 pages, 4 figures, accepted for publication in Astronomy &
Astrophysics (Letter
Determinants of Student Achievements in the Primary Education of Paraguay
The idea that schooling scores depend on a combination of family background characteristics, ability and school (institutional) variables is quite clear. Regarding the issue of intergenerational transmission of inequality in the educational system, the most important question would be if and to what extent could a better institutional performance of the school service compensate for problems related to family background. By means of the estimation of a reduced form equation for selected scores, we investigate the impact of institutional performance on scores after controlling for family background and individual characteristics. We do this by using a novel data set and an OLS and quantile regression approach to analyze how heterogeneous the process of score generation can be. By providing integral health solutions, minimizing under-nutrition and providing ideal conditions in the classroom, training teachers can impact positively on low and mean learning outcomes, thus contributing to an improved educational quality and breaking cycles of intergenerational transmission of inequality. Increasing learning outcomes for levels above the median, only strengthens the transmission of inequality. Consequently, the equality approach should focus on trying to improve the worst scores and our results show that this can be reached at a significant level closing teacher training gaps, improving classroom conditions and improving health and nutrition.
ITQ's in Chile: Measuring the Economic Benefits of Reform
In 2001 an individual (operationally transferable) quota system was introduced for all the most important industrial fisheries in Chile. This system was put in place after years of declining stocks and over investment. In this paper we describe this reform and estimate related allocative efficiency benefits for the most important industrial fishery in the country, the southern pelagic fishery. Benefits were estimated using a bioeconomic model and Monte Carlo techniques. This approach allows benefits to be estimated using more realistic counterfactual scenarios than just comparing the fishery before and after the reform. Estimated discounted net benefits reach US366 million in the period 2001 to 2020. Fleet size fell from 148 active boats in 2000 to 65 in 2002 as a direct consequence of the reform. Among the interesting features of the recent Chilean experience is the way the political economy of the reform was facilitated by the prior introduction of de facto individual quotas within the framework of fishery research activities. When the authorities closed the southern pelagic fishery because of biological problems between 1997 and 2000, they organized ‘experimental’ fishing expeditions in which participant boats were given the right to fish a certain amount of resources per expedition. This pseudo quota system allowed fishermen to experience directly the benefits of individual quotas and that was instrumental to the political agreement leading to the reform. This successful gradual approach may be of interest to other countries planning to introduce individual quotas. Finally, it is important to note that the Chilean southern industrial pelagic fishery has average catches of over 1.4 million tons a year, making it one of the largest fisheries in the world to be regulated by individual quotas.Bioeconomic model, pelagic fisheries, individual transferable quotas
Storage and Logistics Distribution of Vaccination in Panama
We understand distribution as the function that allows the transfer of products and services from their final state of production to that of acquisition and consumption encompassing the set of activities or flows necessary to place the goods and services produced at the disposal of the final buyer individuals or organizations in the conditions of place time form and adequate quantity It is the part of logistics the commercial one which refers to the external movement of finished products or semi-finished products in the case of industrial products from the seller origin to the client or buyer destination with the distribution channel being the that will allow such a connection Indeed physical distribution includes planning and controlling the physical movement of products from the factory to the final consumer That is why logistics includes the planning and control of the relationships between the management of raw materials and the distribution of the finished product Following this orientation it seems clear that the concept of logistics is broader than that of physical distribution and the latter would be an important part of logistics By virtue of this a distribution channel is the path followed by a product or service to go from the production phase to the acquisition and consumption phase The path of a channel is formed by a variable number of more or less autonomous organizations internal and or external to the company which maintain structures behaviors and social relations in general which result in the realization with greater or lesser success of the various distribution functions The organizations that make up the channel are called intermediaries being distribution companies located between the producer and the final consumer In this sense the methodology used in this article will be based on theoretical analysis of repositories and documentary information that refers to the subjec
Creation of Logistics Clusters for the Revolution of the Mobility of Public Electric Transport to Promote a Greener Panama
Referring to the fact that a logistics cluster consists of a group of companies within the same sector with the main objective of improving their competitiveness due to the cooperation between those who form it Logistics is a very important section mainly in many companies dedicated to the transport of goods and that is why why many are opting for this option that allows them to reduce costs and therefore be more competitive In freight transport the logistics cluster is especially important mainly due to the saturation of infrastructures For this reason certain mechanisms are needed to support the organization of the means available to companies in the sector Thus a logistics cluster ensures that the supply chain is not broken at any time and delivery times are respected at all times In this sense the methodology used in this article was of a qualitative documentary and bibliographic type with the application of a brief interview where the analysis of selected ones with reference to the creation of logistics clusters for the revolution and mobility of electric public transport will be reflected The statistical data will be obtained from the repositories and selected articles to provide a better understanding of the results in turn it will have their respective conclusions and bibliographic reference
The planetary nebula IC 5148 and its ionized halo
Many round or nearly roundish Planetary Nebulae (PNe) show multiple shells
and halo structures during their evolutionary stage near the maximum
temperature of their central star. Controversial debate is currently ongoing if
these structures are recombination halos, as suggested by hydrodynamic
modelling efforts, or ionized material. Recently we discovered a halo with even
somewhat unusual structures around the sparsely studied PN IC~5148 and present
for the first time spectroscopy going out to the halo of such a PN.} resolution
spectroscopy is used to derive dust chemistry and mineralogy. We investigate
the spatial distribution of material and its ionization state from the center
of the nebula up to the very outskirts of the halo. We obtained long-slit low
resolution spectroscopy (FORS2@VLT) of the nebula in two position angles, which
we used to investigate the nebular structure and its halo in the optical range
from 450 to 880\,nm. In addition we used medium resolution spectra taken with
X-SHOOTER@VLT ranging from 320 nm to 2.4 mu to derive atmospheric parameters
for the central star. We obtained the distance and position in the Galaxy from
various methods combined with GAIA DR2 data. We also applied Cloudy models to
the nebula in order to derive physical parameters of the various regions. We
obtained spatially resolved structures and detailed descriptions of the
outrunning shock front and a set of unusual halo structures denoted to further
shock. The halo structures appears clearly as hot ionized material. Furthermore
we derived a reliable photometric value for the central star at a GAIA distance
of D=1.3kpc. Considering the large distance \,kpc from the galactic
plane together to its non-circular motion in the galaxy and, a metallicity only
slightly below that of typical disk PNe, most likely IC 5148 originates from a
thick disk population star.Comment: 12 pages, 17 figures, accepted for publication in Astronomy &
Astrophysic
Exploring the long-term variability and evolutionary stage of the interacting binary DQ Velorum
To progress in the comprehension of the double periodic variable (DPV)
phenomenon, we analyse a series of optical spectra of the DPV system DQ Velorum
during much of its long-term cycle. In addition, we investigate the
evolutionary history of DQ Vel using theoretical evolutionary models to obtain
the best representation for the current observed stellar and orbital parameters
of the binary. We investigate the evolution of DQ Vel through theoretical
evolutionary models to estimate the age and the mass transfer rate which are
compared with those of its twin V393 Scorpii. Donor subtracted spectra covering
around 60% of the long-term cycle, allow us to investigate time-modulated
spectral variations of the gainer star plus the disc. We compare the observed
stellar parameters of the system with a grid of theoretical evolutionary tracks
computed under a conservative and a non-conservative evolution regime. We have
found that the EW of Balmer and helium lines in the donor subtracted spectra
are modulated with the long-term cycle. We observe a strenghtening in the EWs
in all analysed spectral features at the minimum of the long-term cycle which
might be related to an extra line emission during the maximum of the long-term
variability. Difference spectra obtained at the secondary eclipse support this
scenario. We have found that a non-conservative evolutionary model is a better
representation for the current observed properties of the system. The best
evolutionary model suggests that DQ Vel has an age of 7.40 x 10^{7} yr and is
currently in a low mass transfer rate (-9.8x10^{-9} Msun/yr) stage, after a
mass transfer burst episode. Comparing the evolutionary stages of DQ Vel and
V393 Sco we observed that the former is an older system with a lower mass
transfer rate. This might explain the differences observed in the physical
parameters of their accretion discs.Comment: 10 pages, 13 figure
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