372 research outputs found
CCD Washington photometry of four poorly studied open clusters in the two inner quadrants of the galactic plane
Complementing our Washington photometric studies on Galactic open clusters
(OCs), we now focus on four poorly studied OCs located in the first and fourth
Galactic quadrants, namely BH 84, NGC 5381, BH 211 and Czernik 37. We have
obtained CCD photometry in the Washington system and passbands down
to 18.5 magnitudes for these four clusters. Their positions and
sizes were determined using the stellar density radial profiles. We derived
reddening, distance, age and metallicity of the clusters from extracted
color-magnitude diagrams (CMDs), using theoretical isochrones
computed for the Washington system. There are no previous photometric data in
the optical band for BH 84, NGC 5381 and BH 211. The CMDs of the observed
clusters show relatively well defined main sequences, except for Czernik 37,
wherein significant differential reddening seems to be present. The red giant
clump is clearly seen only in BH 211. For this cluster, we estimated the age in
(1000) Myr, assuming a metallicity of = 0.019. BH 84 was
found to be much older than it was previously believed, while NGC 5381 happened
to be much younger than previously reported. The heliocentric distances to
these clusters are found to range between 1.4 and 3.4 kpc. BH 84 appears to be
located at the solar galactocentric distance, while NGC 5381, BH 211 and
Czernik 37 are situated inside the solar ring.Comment: 30 pages, 9 figures, 10 table
Gold coating of micromechanical DNA biosensors by pulsed laser deposition
In this work, we describe the gold-coating of silicon microcantilever sensors by pulsed laser deposition (PLD) and their performance as DNA biosensors. To test optimum deposition conditions for coating the sensors, silicon substrates were gold coated by PLD using the fifth harmonic of a Nd:YAG laser (213 nm, pulse duration 15 ns). The gold deposits were characterized by atomic force microscopy and x-ray diffraction. The adequate conditions were selected for coating the sensors with a 20 nm thick gold layer and subsequently functionalized with a self-assembled monolayer of thiolated DNA. To verify PLD as a tool for gold coating of biomechanical sensors, they were characterized by using a scanning laser analyzer platform. Characterization consisted in the measurement of the differential stress of the cantilevers upon hydration forces before and after functionalization with a double-stranded DNA monolayer. The measurements showed that the sensor surface stress induced by the adsorption of water molecules is approximately seven times higher than that of functionalized sensors gold coated by thermal evaporation. These results indicate that gold coating by PLD could be an advantageous method to enhance the response of biomechanical sensors based on gold-thiol chemistry.Peer Reviewe
Determinación de parámetros fundamentales de dos cúmulos abiertos del cuarto cuadrante galáctico en base a fotometría de Washington
We present preliminary results obtained from a photometric analysis in the Washington system C and T1 passbands of two poorly known open clusters (OCs) located in the fourth Galactic quadrant: BH 84 and BH 211. Based on the best fits of theoretical isochrones to the (T1, C −T1) colour- magnitude diagrams, we derive the fundamental cluster parameters. The present results are part of a major project which aims to characterize almost a hundred OCs observed and analyzed in a
homogeneous way.Presentamos resultados preliminares obtenidos a partir del análisis fotométrico en las bandas C y T1 del Sistema de Washington de 2 cúmulos abiertos (CAs) pobremente estudiados del cuarto cuadrante galáctico: BH 84 y BH 211. En base a los mejores ajustes de isócronas teóricas a los diagramas color-magnitud (T1, C −T1), derivamos los parámetros fundamentales de ambos objetos. Los presentes resultados constituyen parte de un proyecto mayor que prevé la caracterización de casi un centenar de CAs observados y analizados de manera homogénea.Fil: Marcionni, N.. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; ArgentinaFil: Parisi, M. C.. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; ArgentinaFil: Claria Olmedo, Juan Jose. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ahumada, Andrea Veronica. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Palma, Tali. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Piatti, Andres Eduardo. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentin
Costs and consequences of chronic pain due to musculoskeletal disorders from a health system perspective in Chile
Copyright © 2018 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of The International Association for the Study of Pain. Background: Chronic pain is a prevalent and distressing condition caused by an unceasing pain lasting more than 3 months or a pain that persists beyond the normal healing time. There is evidence of inadequate management partly explained by the unawareness regarding the magnitude of the problem. Objectives: To estimate the annual expected costs and consequences of chronic pain caused by musculoskeletal diseases from the health system perspective in Chile. Methods: A Markov cohort model was built to represent chronic pain and estimate expected costs and consequences over 1-year time horizon. Transition probabilities were obtained through expert elicitation. Consequences examined were: years lost to disability (YLD), depression, anxiety, and productivity losses. Direct health care costs were estimated using local sources. Probabilistic sensitivity analysis was performed to characterize second-order uncertainty. Results: The annual expected cost due to musculoskeletal chronic pain was estimated in USD 94 million (Bayesian credibility interval 95% 156.26). Productivity losses were also important cost, although early retirement and presenteeism were not measured. Chronic pain causes 137,037 YLDs. Conclusion: Chronic pain is not only an important cause of disability but also responsible for high social and financial burden in Chile. Public health programs focused on managing chronic pain may decrease burden of disease and possibly reduce costs.
Mergers of close primordial binaries
We study the production of main sequence mergers of tidally-synchronized
primordial short-period binaries. The principal ingredients of our calculation
are the angular momentum loss rates inferred from the spindown of open cluster
stars and the distribution of binary properties in young open clusters. We
compare our results with the expected number of systems that experience mass
transfer in post-main sequence phases of evolution and compute the
uncertainties in the theoretical predictions. We estimate that main-sequence
mergers can account for the observed number of single blue stragglers in M67.
Applied to the blue straggler population, this implies that such mergers are
responsible for about one quarter of the population of halo blue metal poor
stars, and at least one third of the blue stragglers in open clusters for
systems older than 1 Gyr. The observed trends as a function of age are
consistent with a saturated angular momentum loss rate for rapidly rotating
tidally synchronized systems. The predicted number of blue stragglers from main
sequence mergers alone is comparable to the number observed in globular
clusters, indicating that the net effect of dynamical interactions in dense
stellar environments is to reduce rather than increase the blue straggler
population. A population of subturnoff mergers of order 3-4% of the upper main
sequence population is also predicted for stars older than 4 Gyr, which is
roughly comparable to the small population of highly Li-depleted halo dwarfs.
Other observational tests are discussed.Comment: number of pages depends on font, margins, columns etc (58 with given
format), 14 figures, submitted to the Astrophysical Journa
Practicas pre profesionales en rumiantes menores en el marco del desarrollo sustentable y el método de aprendizaje servicio
Los alumnos de agronomía y veterinaria de la Universidad Católica de Córdoba provienen en su mayoría de ámbitos urbanos, sumado a la necesidad de tener experiencias académicas que los acerquen a la práctica profesional, por ello que desde el programa SUPPRAD (Sustentabilidad Productiva y Promoción de Áreas Desfavorecidas), entre sus objetivos busca articular acciones bajo la modalidad del aprendizaje servicio, que permitan a los alumnos incrementar su interacción con productores del área rural que cuentan con rumiantes menores dentro de sus ganados permitiendo comprender la problemática de dichas producciones y ser parte de un cambio de marco del desarrollo sustentable de las realidades encontradas. Las prácticas se realizaron a campo, donde se tomaron muestras y datos tanto de los animales como del sistema en general utilizándosela metodología de estructura poblacional, en laboratorio (tanto de fibras animales como de parasitología) y por último una instancia de gabinete donde se realizan debates de los casos encontrados, con el objetivo de poder confeccionar un trabajo final, que consta con una descripción de las tareas realizadas y una propuesta mejoradora para el sistema de producción visitado. Entre los años 2016 y 2018 se formaron 11 grupos relevándose 11 establecimientos, más de 300 animales, se realizaron 82 determinaciones de h.p.g. y 225 muestras de fibra. Hasta el momento se confeccionaron8 informes finales, los cuales fueron presentados a los productores involucrados. El trabajo realizado por medio del aprendizaje servicio apoyados en proyectos de extensión ayudó a los alumnos a un mayor entendimiento de la realidad de las producciones de rumiantes menores. Además del hecho de poder trabajar desde el desarrollo sustentable evitando la sobreexplotación de recursos que no hagan viable en el futuro la producciónademás de permitir su mejora, brindó la chance que puedan integrar conocimientos en prácticas reales, convirtiéndose en una herramienta eficiente en su formación como futuros profesionales
Time-Series Photometry of M67: W UMa Systems, Blue Stragglers, and Related Systems
We present an analysis of over 2200 V images taken on 14 nights at the Mt.
Laguna 1 m telescope of the open cluster M67. Our observations overlap but
extend beyond the field analyzed by Gilliland et al. (1991), and complement
data recently published by van den Berg et al. (2002) and Stassun et al.
(2002). We show variability in the light curves of all 4 of the known W UMa
variables on timescales ranging from a day to decades (for AH Cnc). We have
modeled the light curve of AH Cnc, and the total eclipses allow us to determine
q = 0.16 +0.03/-0.02 and i = 86 +4/-8 degrees. The position of this system near
the turnoff of M67 makes it useful for constraining the turnoff mass for the
cluster. We have also detected two unusual features in the light curve of AH
Cnc that may be caused by prominences. We have also monitored cluster blue
stragglers for variability, and we present evidence hinting at low level
variations in the stragglers S752, S968, and S1263, and we place limits on the
variability of a number of other cluster blue stragglers. Finally, we provide
photometry of the sub-subgiant branch star S1063 showing variability on
timescales similar to the orbital period, while the ``red straggler'' S1040
shows evidence of an unexplained drop in brightness at phases corresponding to
the passage of the white dwarf in front of the giant.Comment: 44 pages, 16 figures, AASTeX, accepted for A
The Blue Stragglers of the Old Open Cluster NGC 188
The old (7 Gyr) open cluster NGC 188 has yielded a wealth of astrophysical
insight into its rich blue straggler population. Specifically, the NGC 188 blue
stragglers are characterized by: A binary frequency of 80% for orbital periods
less than days;Typical orbital periods around 1000 days;Typical
secondary star masses of 0.5 M; At least some white dwarf companion
stars; Modestly rapid rotation; A bimodal radial spatial distribution;
Dynamical masses greater than standard stellar evolution masses (based on
short-period binaries); Under-luminosity for dynamical masses (short-period
binaries). Extensive -body modeling of NGC 188 with empirical initial
conditions reproduces the properties of the cluster, and in particular the
main-sequence solar-type binary population. The current models also reproduce
well the binary orbital properties of the blue stragglers, but fall well short
of producing the observed number of blue stragglers. This deficit could be
resolved by reducing the frequency of common-envelope evolution during Roche
lobe overflow. Both the observations and the -body models strongly indicate
that the long-period blue-straggler binaries - which dominate the NGC 188 blue
straggler population - are formed by asymptotic-giant (primarily) and red-giant
mass transfer onto main sequence stars. The models suggest that the few
non-velocity-variable blue stragglers formed from mergers or collisions.
Several remarkable short-period double-lined binaries point to the importance
of subsequent dynamical exchange encounters, and provide at least one example
of a likely collisional origin for a blue straggler.Comment: Chapter 3, in Ecology of Blue Straggler Stars, H.M.J. Boffin, G.
Carraro & G. Beccari (Eds), Astrophysics and Space Science Library, Springe
Preliminary conceptual model of the Cerro Blanco caldera-hosted geothermal system (Southern Puna, Argentina): Inferences from geochemical investigations.
The Cerro Blanco Caldera (CBC) is the youngest collapse caldera system in the Southern Central Andes (Southern
Puna, Argentina). The CBC is subsiding with at an average velocity of 0.87 cm/year and hosts an active geothermal
system. A geochemical characterization of emitted fluids was carried out based on the chemical and
isotopic compositions of fumaroles, and thermal and cold springs discharged in this volcanic area with the aim of
constructing the first hydrogeochemical conceptual model and preliminary estimate the geothermal potential.
The main hydrothermal reservoir, likely hosted within the pre-caldera basement rocks, has a Na+-Clˉ(HCO3)ˉ
composition with estimated temperatures ≥135 °C. The unconsolidated, fine-grained Cerro Blanco ignimbrite
likely acts as the cap-rock of the hydrothermal system. The presence of phreatic eruption breccias in the surrounding
area of the geothermal fumaroles supports the effectiveness of the pyroclastic deposit as sealing rocks.
The isotopic data of water (δ18O and δD) indicate a meteoric recharge of the hydrothermal reservoir, suggesting
as recharge areas the sectors surrounding the CBC, mainly towards the W and NW where large outcrops of the
pre-caldera basement exist. A fault-controlled hydraulic connection between the hot springs and the hydrothermal
reservoir is proposed for the Los Hornitos area. The fumaroles show the typical compositional features of
hydrothermal fluids, being dominated by water vapor with significant concentrations of H2S, CH4 and H2.
Considering the high geothermal gradient of this area (∼104 °C/km) and the relatively high fraction of mantle
He (∼39%) calculated on the basis of the measured R/Ra values, the hydrothermal aquifer likely receives inputs
of magmatic fluids from the degassing magma chamber. The preliminary geothermal potential at CBC was
evaluated with the Volume Method, calculating up to E = 11.4*1018 J. Both the scarce presence of superficial
thermal manifestations and the occurrence of an efficient cap-rock likely contribute to minimize the loss of
thermal energy from the reservoir. The results here presented constitute the necessary base of knowledge for
further accurate assessment of the geothermal potential and ultimately the implementation of the geothermal
resource as a viable energy alternative for small localities or mining facilities isolated from the National
Interconnected System due to their remote localization.Published1022136A. Geochimica per l'ambiente e geologia medicaJCR Journa
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