1,734 research outputs found
Kinematic study of planetary nebulae in NGC 6822
By measuring precise radial velocities of planetary nebulae (which belong to
the intermediate age population), H II regions, and A-type supergiant stars
(which are members of the young population) in NGC 6822, we aim to determine if
both types of population share the kinematics of the disk of H I found in this
galaxy.
Spectroscopic data for four planetary nebulae were obtained with the high
spectral resolution spectrograph Magellan Inamori Kyocera Echelle (MIKE) on the
Magellan telescope at Las Campanas Observatory. Data for other three PNe and
one H II region were obtained from the SPM Catalog of Extragalactic Planetary
Nebulae which employed the Manchester Echelle Spectrometer attached to the 2.1m
telescope at the Observatorio Astron\'omico Nacional, M\'exico. In the
wavelength calibrated spectra, the heliocentric radial velocities were measured
with a precision better than 5-6 km s. Data for three additional H II
regions and a couple of A-type supergiant stars were collected from the
literature. The heliocentric radial velocities of the different objects were
compared to the velocities of the H i disk at the same position.
From the analysis of radial velocities it is found that H II regions and
A-type supergiants do share the kinematics of the H I disk at the same
position, as expected for these young objects. On the contrary, planetary
nebula velocities differ significantly from that of the H I at the same
position. The kinematics of planetary nebulae is independent from the young
population kinematics and it is closer to the behavior shown by carbon stars,
which are intermediate-age members of the stellar spheroid existing in this
galaxy. Our results are confirming that there are at least two very different
kinematical systems in NGC 6822
Hybrid algorithm with perturbations for total asymptotically non-expansive mappings in CAT(0) space
In this paper, we establish strong and Δ-convergence theorems of the modified hybrid-CR three steps iteration with perturbations for total asymptotically non-expansive mapping in CAT(0) spaces. Our results improve and extend the corresponding results from the current literature. We also provide three examples to illustrate the convergence behaviour of the proposed algorithm and numerically compare the convergence of the proposed iteration scheme with the existing schemes
Improving randomness characterization through Bayesian model selection
Nowadays random number generation plays an essential role in technology with
important applications in areas ranging from cryptography, which lies at the
core of current communication protocols, to Monte Carlo methods, and other
probabilistic algorithms. In this context, a crucial scientific endeavour is to
develop effective methods that allow the characterization of random number
generators. However, commonly employed methods either lack formality (e.g. the
NIST test suite), or are inapplicable in principle (e.g. the characterization
derived from the Algorithmic Theory of Information (ATI)). In this letter we
present a novel method based on Bayesian model selection, which is both
rigorous and effective, for characterizing randomness in a bit sequence. We
derive analytic expressions for a model's likelihood which is then used to
compute its posterior probability distribution. Our method proves to be more
rigorous than NIST's suite and the Borel-Normality criterion and its
implementation is straightforward. We have applied our method to an
experimental device based on the process of spontaneous parametric
downconversion, implemented in our laboratory, to confirm that it behaves as a
genuine quantum random number generator (QRNG). As our approach relies on
Bayesian inference, which entails model generalizability, our scheme transcends
individual sequence analysis, leading to a characterization of the source of
the random sequences itself.Comment: 25 page
Preyssler Heteropolyacids in the Self-Etherification of 5-Hydroxymethylfurfural to 5,5′-[Oxybis(methylene)]bis-2-furfural Under Mild Reaction Conditions
The synthesis of 5,5′-[oxybis(methylene)]bis-2-furfural (OBMF) from 5-hydroxymethylfurfural (5-HMF) was studied using bulk and alumina-supported Preyssler heteropolyacids (HPAs). The formation of OBMF was related to the amount of Brønsted acid sites, and the lowest yield of OBMF was obtained with supported HPAs. However, the Lewis acidity of the HPA supported on Al2O3 favored the formation of 2,5-dimethylfurane. The effects of solvent, catalyst loading, temperature, and reaction time on the selectivity to OBMF from 5-HMF were studied to optimize OBMF production using bulk Preyssler HPAs; a yield of 84 % to OBMF was obtained at 5 h and 343 K. These results demonstrate that bulk Preyssler HPA is a good candidate for OBMF synthesis under mild reaction conditions.Fil: Páez, Alexander. Universidad Pedagógica y Tecnológica de Colombia; ColombiaFil: Rojas, Hugo A.. Universidad Pedagógica y Tecnológica de Colombia;Fil: Portilla Zúñiga, Omar Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas ; ArgentinaFil: Sathicq, Angel Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas ; ArgentinaFil: Afonso, Carlos A. M.. Universidade de Lisboa; PortugalFil: Romanelli, Gustavo Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas ; ArgentinaFil: Martínez, José J.. Universidad Pedagógica y Tecnológica de Colombia; Colombi
Exploring the intricate evolutionary history of the diploid-polyploid complexVeronica subsection Pentasepalae(Plantaginaceae)
[EN]Veronica subsection Pentasepalae is a diploid–polyploid complex of c. 20 species distributed in Eurasia and North Africa, in which species boundaries are difficult to determine. Here, we present the first comprehensive phylogenetic analysis of V. subsection Pentasepalae based on nucleotide sequences [internal transcribed spacer (ITS) and the plastid trnH-psbA and ycf6-psbM spacers] combined with ploidy estimations. Our results support the monophyly of the subsection. Five well-supported clades are recovered in the ITS sequence analyses, corresponding to broad geographical areas. The causes of the extensive incongruence found between the ITS and plastid DNA datasets, namely incomplete lineage sorting and/or hybridization and polyploidization, are discussed. Most of the diploids traditionally recognized based on morphological characters and one tetraploid are each recovered as monophyletic by the ITS sequence analyses. The Balkan species V. kindlii is resurrected. DNA ploidy level for V. teucrioides is reported here for the first time (2x). Diploid populations have been found for V. orbiculata, which was previously thought to be only tetraploid. Past contact in the amphi-Adriatic area between V. orsiniana and V. orbiculata is suggested. Finally, molecular analyses show that diploid V. jacquinii and diploid V. orbiculata are unrelated. This study contributes to our understanding of the evolutionary history of polyploid complexes, especially those in southern Europe, and highlights the importance of using multiple lines of evidence to investigate species boundaries in such actively diversifying groups
A nomenclatural treatment for Veronica subsect. Pentasepalae (Plantaginaceae sensu APG III) and typification of several names
[EN] The large genus Veronica has a complex evolutionary history. Within it, Veronica subsect. Pentasepalae represents an ideal system to study important evolutionary processes, such as hybridization and polyploidization. Delimitation of species boundaries within the subsection is a difficult task and the highly complicated taxonomy of the group has led to an accumulation of approximately 230 names for 22 accepted taxa. Many names have been used in different taxonomic senses even in recent Floras, scientific works, catalogues, Red Lists and internet resources. The lack of an updated taxonomic and nomenclatural framework represents a significant problem to develop further studies in several fields such as ecology, conservation, plant and evolutionary biology. A complete nomenclatural treatment for the whole subsection is provided here, that relies on results derived from the first phylogenetic analysis of V. subsect. Pentasepalae based on DNA sequence data, morphology and ploidy‐ level information. Nomenclatural types for 22 validly published names are designated. In total 21 lectotypes, 2 epitypes and 1 neotype are chosen. A new combination, Veronica linearis, is proposed
Strategic planning for community sustainability in model forests: Case study of the Yoro model forest, Honduras
El estudio plantea una planificación estratégica de desarrollo en los Bosques Modelo a partir del estudio del caso del Bosque Modelo de Yoro, en Honduras, en donde el sector de la industria maderera y en concreto el subsector de carpintería y mueble, parece tener más ventajas competitivas para producir productos de exportación que generen riqueza en la zona, dada la escasa capacidad de compra de la región. A este subsector se le realiza un Análisis estratégico, una Elección estratégica y una Implementación estratégica determinando que el desarrollo del subsector podría pasar por crear una cooperativa capaz de suministrar partes de muebles a una empresa de carácter internacional que tenga como estrategia comercial la venta de muebles naturales, ecológicos y que esté comprometida socialment
AIRPA: An Architecture to Support the Execution and Maintenance of AI-Powered RPA Robots
Robotic Process Automation (RPA) has quickly evolved
from automating simple rule-based tasks. Nowadays, RPA is required
to mimic more sophisticated human tasks, thus implying its combina tion with Artificial Intelligence (AI) technology, i.e., the so-called intelli gent RPA. Putting together RPA with AI leads to a challenging scenario
since (1) it involves professionals from both fields who typically have
different skills and backgrounds, and (2) AI models tend to degrade
over time which affects the performance of the overall solution. This
paper describes the AIRPA project, which addresses these challenges by
proposing a software architecture that enables (1) the abstraction of the
robot development from the AI development and (2) the monitor, con trol, and maintain intelligent RPA developments to ensure its quality
and performance over time. The project has been conducted in the Serv inform context, a Spanish consultancy firm, and the proposed prototype
has been validated with reality settings. The initial experiences yield
promising results in reducing AHT (Average Handle Time) in processes
where AIRPA deployed cognitive robots, which encourages exploring the
support of intelligent RPA development.Ministerio de Ciencia, Innovación y Universidades PID2019-105455GB-C31Centro para el Desarrollo Tecnológico Industrial EXP00118029/IDI-20190524Centro para el Desarrollo Tecnológico Industrial P011-19/E0
Alternative symplectic structures for SO(3,1) and SO(4) four-dimensional BF theories
The most general action, quadratic in the B fields as well as in the
curvature F, having SO(3,1) or SO(4) as the internal gauge group for a
four-dimensional BF theory is presented and its symplectic geometry is
displayed. It is shown that the space of solutions to the equations of motion
for the BF theory can be endowed with symplectic structures alternative to the
usual one. The analysis also includes topological terms and cosmological
constant. The implications of this fact for gravity are briefly discussed.Comment: 13 pages, LaTeX file, no figure
Quark stars and quantum-magnetically induced collapse
Quark matter is expected to exist in the interior of compact stellar objects
as neutron stars or even the more exotic strange stars, based on the
Bodmer-Witten conjecture. Bare strange quark stars and (normal) strange
quark-matter stars, those possessing a baryon (electron-supported) crust, are
hypothesized as good candidates to explain the properties of a set of peculiar
stellar sources as the enigmatic X-ray source RX J1856.5-3754, some pulsars as
PSR B1828-11 and PSR B1642-03, and the anomalous X-ray pulsars and soft
gamma-ray repeaters. In the MIT bag model, quarks are treated as a degenerate
Fermi gas confined to a region of space having a vacuum energy density
(the Bag constant). In this note, we modif{}y the MIT Bag Model by
including the electromagnetic interaction. We also show that this version of
the MIT model implies the anisotropy of the Bag pressure due to the presence of
the magnetic field. The equations of state of degenerate quarks gases are
studied in the presence of ultra strong magnetic fields. The behavior of a
system made-up of quarks having (or not) anomalous magnetic moment is reviewed.
A structural instability is found, which is related to the anisotropic nature
of the pressures in this highly magnetized matter. The conditions for the
collapse of this system are obtained and compared to a previous model of
neutron stars build-up on a neutron gas having anomalous magnetic moment.Comment: 11 pages, 2 figure
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