Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99


Any time

2020 ( 68 )

2019 ( 895 )

2018 ( 1054 )

2017 ( 984 )

Custom range...

Search Results: 1 - 10 of 656128 matches for " J. A. Fernandez-Ontiveros "
All listed articles are free for downloading (OA Articles)
Page 1 /656128
Display every page Item
The innermost globular clusters of M87
M. Montes,J. A. Acosta-Pulido,M. A. Prieto,J. A. Fernandez-Ontiveros
Physics , 2014, DOI: 10.1093/mnras/stu948
Abstract: We present a comprehensive multiwavelength photometric analysis of the innermost (3x3 square kpc) 110 globular clusters (GCs) of M87. Their spectral energy distributions (SEDs) were built taking advantage of new ground-based high resolution near-IR imaging aided by adaptive optics at the Very Large Telescope (VLT) combined with Hubble Space Telescope (HST) ultraviolet--optical archival data. These GC SEDs are among the best photometrically sampled extragalactic GC SEDs. To compare with our SEDs we constructed equally sampled SEDs of Milky Way GCs. Using both these Milky Way cluster templates and different stellar population models, ages of >10 Gyr and metallicities of [Fe/H] -0.6 dex are consistently inferred for the inner GCs of M87. In addition, the metallicity of these GCs is low (Dif([Fe/H]) 0.8 dex) compared to that of their host galaxy. These results agree with the idea that the GC formation in M87 ceased earlier than that of the bulk of the stars of the central part of the galaxy. The ages of the inner GCs of M87 support the idea that these central parts of the galaxy formed first. Our data do not support evidence of recent wet merging.
The central parsecs of M87: jet emission and an elusive accretion disc
M. A. Prieto,J. A. Fernandez-Ontiveros,S. Markoff,D. Espada,O. Gonzalez-Martin
Physics , 2015,
Abstract: We present the first time-simultaneous high angular resolution spectral energy distribution (SED) of the core of M87 at a scale of 0.4 arcsecs across the electromagnetic spectrum. Two activity periods of the core of M87 are sampled: a quiescent mode, representative of the most common state of M87, and an active one, represented by the outburst occurring in 2005. The main difference between both SEDs is a shift in flux in the active SED by a factor of about two, their shapes remaining similar across the entire spectrum. The shape of the compiled SEDs is remarkably different from those of active galactic nuclei (AGN). It lacks three major AGN features: the IR bump, the inflection point at about 1 micron and the blue bump. The SEDs also differ from the spectrum of a radiatively inefficient accretion flow. Down to the scales of ~12 pc from the centre, we find that the emission from a jet gives an excellent representation of the spectrum over ten orders of magnitude in frequency for both the active and the quiescent phases of M87. The inferred total jet power is one to two orders of magnitude lower than the jet mechanical energy inferred from various methods in the literature. This discrepancy cannot easily be ascribed to variability. Yet, our measurements regard the inner few parsecs which might provide a genuine account of the jet power at the base. We derive a strict upper limit to the accretion rate of 6 x 10E-5 Mo / yr, assuming 10% efficiency. The inferred accretion power can account for M87 radiative luminosity at the jet-frame assuming boosting factors larger than 10, it is however two orders of magnitude below that required to account for M87 jet kinetic power. We thus propose that energy tapped from the black hole spin may be a complementary source to power the jet of M87, a large supply of accreting gas becoming thus unnecessary.
The spectral energy distribution of the central parsecs of the nearest AGN
M. A. Prieto,J. Reunanen,K. R. W. Tristram,N. Neumayer,J. A. Fernandez-Ontiveros,M. Orienti,K. Meisenheimer
Physics , 2009, DOI: 10.1111/j.1365-2966.2009.15897.x
Abstract: Spectral energy distributions (SEDs) of the central few tens of parsec region of some of the nearest, most well studied, active galactic nuclei (AGN) are presented. These genuine AGN-core SEDs, mostly from Seyfert galaxies, are characterised by two main features: an IR bump with the maximum in the 2-10 micron range, and an increasing X-ray spectrum in the 1 to ~200 keV region. These dominant features are common to Seyfert type 1 and 2 objects alike. Type 2 AGN exhibit a sharp drop shortward of 2 micron, with the optical to UV region being fully absorbed, while type 1s show instead a gentle 2 micron drop ensued by a secondary, partially-absorbed optical to UV emission bump. Assuming the bulk of optical to UV photons generated in these AGN are reprocessed by dust and re-emitted in the IR in an isotropic manner, the IR bump luminosity represents >70% of the total energy output in these objects while the high energies above 20 keV are the second energetically important contribution. Galaxies selected by their warm IR colours, i.e. presenting a relatively-flat flux distribution in the 12 to 60 micron range have often being classified as AGN. The results from these high spatial resolution SEDs question this criterion as a general rule. It is found that the intrinsic shape of the IR SED of an AGN and inferred bolometric luminosity largely depart from those derived from large aperture data. AGN luminosities can be overestimated by up to two orders of magnitude if relying on IR satellite data. We find these differences to be critical for AGN luminosities below or about 10^{44} erg/s. Above this limit, AGNs tend to dominate the light of their host galaxy regardless of the aperture size used. We tentatively mark this luminosity as a threshold to identify galaxy-light- vs AGN- dominated objects.
Polyamide Fibers Covered with Chlorhexidine: Thermodynamic Aspects  [PDF]
E. Giménez-Martín, M. López-Andrade, J. A. Moleón-Baca, M. A. López, A. Ontiveros-Ortega
Journal of Surface Engineered Materials and Advanced Technology (JSEMAT) , 2015, DOI: 10.4236/jsemat.2015.54021
Abstract: Results of dynamic and equilibrium of sorption of a reactive dye Remazol Brilliant Blue, and a bactericidal agent, Digluconate of Chlorhexidine over Polyamide fibers are presented with the aim of supplying the fiber with bactericidal properties. However, adsorption of Chlorhexidine onto Polyamide is scarce due to the lack of interactions between the reactive groups of the fiber and the antiseptic molecule. Therefore, in order to provide the fiber surface with anionic groups, fiber has been previously dyed with Remazol Brilliant Blue which increases the negative charge of the fiber surface due to the presence of its sulfonate end groups. Thermodynamic parameters of equilibrium sorption in the two situations, fiber/dye and fiber-dye/Chlorhexidine, have been analyzed, as function of the temperature, pH and concentration of the dye in the pretreatment. Results show that when sorption of Remazol Brilliant Blue reaches the value of about 50 mmol/ kg at the higher temperature and concentration tested, the amount of Chlorhexidine adsorbed exhibits its maximum value which is 6 mmol/kg. Both processes, adsorption of Remazol Brilliant Blue and adsorption of Chlorhexidine, fit well to Langmuir adsorption model, suggesting the existence of some kinds of specific interactions between adsorbent and adsorbate. Thermodynamic functions show that the interaction is endothermic and spontaneous in all the rage of temperature tested. The kinetic studies show that sorption of Remazol Brilliant Blue is better described by pseudo-first order model, while sorption of Chlorhexidine fits better to pseudo-second order model, and seems to be quicker process. According to the obtained results, chemical interaction between the vinyl-sulfone group of Remazol Brilliant Blue and the amine groups of Polyamide fiber, followed by electrostatic interactions between the guanine group of the Chlorhexidine and the sulfonate group of the dye must be considered in order to explain the adsorption process.
Status of neonatal intensive care units in India.
Fernandez A,Mondkar J
Journal of Postgraduate Medicine , 1993,
Abstract: Neonatal mortality in India accounts for 50% of infant mortality, which has declined to 84/1000 live births. There is no prenatal care for over 50% of pregnant women, and over 80% deliver at home in unsafe and unsanitary conditions. Those women who do deliver in health facilities are unable to receive intensive neonatal care when necessary. Level I and Level II neonatal care is unavailable in most health facilities in India, and in most developing countries. There is a need in India for Level III care units also. The establishment of neonatal intensive care units (NICUs) in India and developing countries would require space and location, finances, equipment, staff, protocols of care, and infection control measures. Neonatal mortality could be reduced by initially adding NICUs at a few key hospitals. The recommendation is for 30 NICU beds per million population. Each bed would require 50 square feet per cradle and proper climate control. Funds would have to be diverted from adult care. The largest expenses would be in equipment purchase, maintenance, and repair. Trained technicians would be required to operate and monitor the sophisticated ventilators and incubators. The nurse-patient ratio should be 1:1 and 1:2 for other infants. Training mothers to work in the NICUs would help ease the problems of trained nursing staff shortages. Protocols need not be highly technical; they could include the substitution of radiant warmers and room heaters for expensive incubators, the provision of breast milk, and the reduction of invasive procedures such as venipuncture and intubation. Nocosomial infections should be reduced by vacuum cleaning and wet mopping with a disinfectant twice a day, changing disinfectants periodically, maintaining mops to avoid infection, decontamination of linen, daily changing of tubing, and cleaning and sterilizing oxygen hoods and resuscitation equipment, and maintaining an iatrogenic infection record book, which could be used to study the infection patterns and to apply the appropriate antibiotics.
The SED of Low-Luminosity AGNs at high-spatial resolution
J. A. Fernández-Ontiveros,M. A. Prieto,J. A. Acosta-Pulido,M. Montes
Physics , 2012, DOI: 10.1088/1742-6596/372/1/012006
Abstract: The inner structure of AGNs is expected to change below a certain luminosity limit. The big blue bump, footprint of the accretion disk, is absent for the majority of low-luminosity AGNs (LLAGNs). Moreover, recent simulations suggest that the torus, a keystone in the Unified Model, vanishes for nuclei with L_bol < 10^42 erg/s. However, the study of LLAGN is a complex task due to the contribution of the host galaxy, which light swamps these faint nuclei. This is specially critical in the IR range, at the maximum of the torus emission, due to the contribution of the old stellar population and/or dust in the nuclear region. Adaptive optics imaging in the NIR (VLT/NaCo) together with diffraction limited imaging in the mid-IR (VLT/VISIR) permit us to isolate the nuclear emission for some of the nearest LLAGNs in the Southern Hemisphere. These data were extended to the optical/UV range (HST), radio (VLA, VLBI) and X-rays (Chandra, XMM-Newton, Integral), in order to build a genuine spectral energy distribution (SED) for each AGN with a consistent spatial resolution (< 0.5") across the whole spectral range. From the individual SEDs, we construct an average SED for LLAGNs sampled in all the wavebands mentioned before. Compared with previous multiwavelength studies of LLAGNs, this work covers the mid-IR and NIR ranges with high-spatial resolution data. The LLAGNs in the sample present a large diversity in terms of SED shapes. Some of them are very well described by a self-absorbed synchrotron (e.g. NGC 1052), while some other present a thermal-like bump at ~1 micron (NGC 4594). All of them are significantly different when compared with bright Seyferts and quasars, suggesting that the inner structure of AGNs (i.e. the torus and the accretion disk) suffers intrinsic changes at low luminosities.
The central parsecs of active galactic nuclei: challenges to the torus
M. A. Prieto,M. Mezcua,J. A. Fernández-Ontiveros,M. Schartmann
Physics , 2014, DOI: 10.1093/mnras/stu1006
Abstract: Type 2 AGN are by definition nuclei in which the broad-line region and continuum light are hidden at optical/UV wavelengths by dust. Via accurate registration of infrared (IR) Very Large Telescope adaptive optics images with optical \textit{Hubble Space Telescope} images we unambiguously identify the precise location of the nucleus of a sample of nearby, type 2 AGN. Dust extinction maps of the central few kpc of these galaxies are constructed from optical-IR colour images, which allow tracing the dust morphology at scales of few pc. In almost all cases, the IR nucleus is shifted by several tens of pc from the optical peak and its location is behind a dust filament, prompting to this being a major, if not the only, cause of the nucleus obscuration. These nuclear dust lanes have extinctions $A_V \geq 3-6$ mag, sufficient to at least hide the low-luminosity AGN class, and in some cases are observed to connect with kpc-scale dust structures, suggesting that these are the nuclear fueling channels. A precise location of the ionised gas H$\alpha$ and [\textsc{Si\,vii}] 2.48 $\mu$m coronal emission lines relative to those of the IR nucleus and dust is determined. The H$\alpha$ peak emission is often shifted from the nucleus location and its sometimes conical morphology appears not to be caused by a nuclear --torus-- collimation but to be strictly defined by the morphology of the nuclear dust lanes. Conversely, [\textsc{Si\,vii}] 2.48 $\mu$m emission, less subjected to dust extinction, reflects the truly, rather isotropic, distribution of the ionised gas. All together, the precise location of the dust, ionised gas and nucleus is found compelling enough to cast doubts on the universality of the pc-scale torus and supports its vanishing in low-luminosity AGN. Finally, we provide the most accurate position of the NGC 1068 nucleus, located at the South vertex of cloud B.
The concentration-compactness principle for variable exponent spaces and applications
J. Fernandez Bonder,A. Silva
Mathematics , 2009,
Abstract: In this paper we extend the well-known concentration -- compactness principle of P.L. Lions to the variable exponent case. We also give some applications to the existence problem for the $p(x)-$Laplacian with critical growth.
The warm molecular gas and dust of Seyfert galaxies: two different phases of accretion?
M. Mezcua,M. A. Prieto,J. A. Fernández-Ontiveros,K. Tristram,N. Neumayer,J. K. Kotilainen
Physics , 2015, DOI: 10.1093/mnras/stv1408
Abstract: The distribution of warm molecular gas (1000--3000 K), traced by the near-IR H$_2$ 2.12 $\mu$m line, has been imaged with a resolution $<0.5$ arcsec in the central 1 kpc of seven nearby Seyfert galaxies. We find that this gas is highly concentrated towards the central 100 pc and that its morphology is often symmetrical. Lanes of warm H$_2$ gas are observed only in three cases (NGC\,1068, NGC\,1386 and Circinus) for which the morphology is much wider and extended than the dust filaments. We conclude that there is no one-to-one correlation between dust and warm gas. This indicates that, if the dust filaments and lanes of warm gas are radial streaming motions of fuelling material, they must represent \textit{two different phases of accretion}: the dust filaments represent a colder phase than the gas close to the nucleus (within $\sim$100 pc). We predict that the morphology of the nuclear dust at these scales should resemble that of the cold molecular gas (e.g. CO at 10--40 K), as we show for CenA and NGC\,1566 by Atacama Large Millimeter/submillimeter Array (ALMA) observations, whereas the inner H$_2$ gas traces a much warmer phase of material identified with warmer (40-500 K) molecular gas such as CO(6-5) or HCN (as shown by ALMA for NGC\,1068 and NGC\,1097). We also find that X-ray heating is the most likely dominant excitation mechanism of the H$_{2}$ gas for most sources.
Bugarín,J; Bojórquez,J. I; Lemus,C; Murray,R. M; Ontiveros,H; Aguirre,J; Hernández,A;
Cultivos Tropicales , 2010,
Abstract: a silvopastoral system was established on a haplic (eutric, cromic) cambisol in the northern coastal plain of nayarit. the application of silvopastoral system for ovine production was evaluated and its impact on soil properties. treatments were leucaena leucocephala+brachiaria brizantha (t1), l. glauca+b. brizantha (t2), l. leucocephala+clitoria ternatea+b. brizantha (t3), l. glauca+c. ternatea+b. brizantha (t4) and b. brizantha (t5), arranged in randomized blocks with four repetitions of 256 m2 each. the experiment was settled in october, 2007 with irrigation and without fertilizers, according to the season. the soil was characterized at the beginning and its physicochemical properties were determined. in the upper 20 cm, bulk density was 1.33 mg.m-3, moisture 12.83 %, ph 6.3 and low organic matter content (1.68 %). five evaluations were performed for bulk density, ph and organic matter content; samples were taken with vegetation cover and without it, regarding the treatments. the main results indicate a bulk density increment and no statistical differences among treatments when finishing the evaluation; ph increased towards more neutral values and also organic matter content, in which arboreous and herbaceous leguminous were mostly employed, as well as pasture (lgcb treatment); arboreous leguminous disappeared at the end of the experiment, so that it had a negative influence on the results. the use of silvopastoral systems is recommended as a mechanism to decrease soil degradation, considering the characteristics of the species to be established and the land
Page 1 /656128
Display every page Item

Copyright © 2008-2017 Open Access Library. All rights reserved.