Star Forming Objects in the Tidal Tails of Compact Groups

A search for star forming objects belonging to tidal tails has been carried out in a sample of deep Halpha images of 16 compact groups of galaxies. A total of 36 objects with Halpha luminosity larger than 10^38 erg s-1 have been detected in five groups. The fraction of the total Halpha luminosity of their respective parent galaxies shown by the tidal objects is always below 5% except for the tidal features of HCG95, whose Halpha luminosity amounts to 65% of the total luminosity. Out of this 36 objects, 9 star forming tidal dwarf galaxy candidates have been finally identified on the basis of their projected distances to the nuclei of the parent galaxies and their total Halpha luminosities. Overall, the observed properties of the candidates resemble those previously reported for the so-called tidal dwarf galaxies.Comment: 5 gif figures. Accepted for publication in Astrophysical Journa

Directrices para evaluar la puesta en valor de un residuo en la fabricación de un material base cemento: producción de hormigón autocompactante a partir de sedimentos dragados

This article presents some guidelines in order to analyse the feasibility of including a waste material in the production of a structural cementitious material. First of all, the compatibility of the waste with a cementitious material has to be assured; then, if necessary, a decontamination step will be carried out; after, decision on the type of material has to be taken based on different aspects, with special emphasis on the granulometry. As a last step, mechanical, environmental and durability properties have to be evaluated. Then the procedure is illustrated with a full example, obtaining a self compacting concrete (SCC) including dredged sediment taken from a Spanish harbour.Este artículo presenta algunas directrices con el fin de analizar la posibilidad de incluir un material de desecho en la producción de un material base cemento estructural. En primer lugar, debe asegurarse la compatibilidad de los residuos con el material base cemento. Tras ello, si es necesario, se llevará a cabo la etapa de descontaminación del residuo. Después debe tomarse la decisión sobre el tipo de material a utilizar en base a diferentes aspectos, haciendo especial énfasis en la granulometría. Como último paso, deben evaluarse las propiedades mecánicas, ambientales y de durabilidad del producto final. El procedimiento a seguir se ilustra con un ejemplo concreto basado en la obtención de un hormigón autocompactante (SCC) incluyendo en su fabricación sedimentos dragados tomados de un puerto español

Sistemas materiales: propuesta de trabajo práctico con modelos moleculares y sistemas reales

El tema de sistemas materiales se imparte desde el 1er año ESB. Sin embargo, una evaluación diagnóstica realizada con alumnos de 3er año ESB al inicio del cuatrimestre del año lectivo 2008, reflejó que un 59 % esencialmente no pudo diferenciar o representar en forma gráfica sistemas homogéneos ni heterogéneos, comparado con un 59 % de alumnos aprobados en la evaluación (calificación 7-10). En base a los resultados obtenidos en dicha evaluación se diseñó una experiencia áulica llevada a cabo con dos grupos de 20-25 alumnos organizados en equipos de 4-5 integrantes cada uno, complementada con un trabajo de laboratorio en la casa. Para el trabajo en el aula se emplearon elementos lúdicos con el fin de simular situaciones reales que se presentan normalmente en trabajos prácticos de laboratorio, a la vez que se reforzaron normas de seguridad (no llevar a la boca, no oler, no derramar, manipular solo sustancias seguras, etc.). La duración del trabajo práctico estuvo prevista para un módulo de 80 minutos (2 horas cátedra). En ambos grupos se obtuvo una participación en clase sorprendente. Con respecto a la tarea en el hogar se diseñó una práctica de laboratorio con sustancias cotidianas (sal, azúcar, agua, etc.). La participación fue del 80-85%. Una evaluación luego de realizadas las prácticas mostró que un 95 % había dominado los conceptos básicos involucrados. En trabajos posteriores los conocimientos adquiridos resultaron ser de utilidad.Trabajos del área Ciencias NaturalesDepartamento de Ciencias Exactas y Naturale

On the origin of the neutral hydrogen supershells: the ionized progenitors and the limitations of the multiple supernovae hypothesis

Here we address the question whether the ionized shells associated with giant HII regions can be progenitors of the larger HI shell-like objects found in the Milky Way and other spiral and dwarf irregular galaxies. We use for our analysis a sample of 12 HII shells presented recently by Rela\~no et al. (2005, 2007). We calculate the evolutionary tracks that these shells would have if their expansion is driven by multiple supernovae explosions from the parental stellar clusters. We find, contrary to Rela\~no et al. (2007), that the evolutionary tracks of their sample HII shells are inconsistent with the observed parameters of the largest and most massive neutral hydrogen supershells. We conclude that HII shells found inside giant HII regions may represent the progenitors of small or intermediate HI shells, however they cannot evolve into the largest HI objects unless, aside from the multiple supernovae explosions, an additional energy source contributes to their expansion.Comment: Accepted for publication in ApJ, tentatively scheduled for the ApJ July 1, 2008, v681n1 issue. 19 pages, 4 figure

Interacting non-minimally coupled canonical, phantom and quintom models of holographic dark energy in non-flat universe

Motivated by our recent work \cite{set1}, we generalize this work to the interacting non-flat case. Therefore in this paper we deal with canonical, phantom and quintom models, with the various fields being non-minimally coupled to gravity, within the framework of interacting holographic dark energy. We employ the holographic model of interacting dark energy to obtain the equation of state for the holographic energy density in non-flat (closed) universe enclosed by the event horizon measured from the sphere of horizon named $L$.Comment: 18 pages, 3 figures. Accepted for publication in IJMPD (2010

Addition of aromatic nucleophiles to a C=N double bond of 1,2,5-thiadiazole 1,1-dioxide

A new synthesis of 3,4-diphenyl-4-aryl-1,2,5-thiadiazolines 1,1-dioxide through the addition of aromatic derivatives to 1,2,5-thiadiazole 1,1-dioxide is presented. Anhydrous AlCl3 is used as catalyst.Facultad de Ciencias Exacta

Feedback in the Antennae Galaxies (NGC 4038/9): I. High-Resolution Infrared Spectroscopy of Winds from Super Star Clusters

We present high-resolution (R ~ 24,600) near-IR spectroscopy of the youngest super star clusters (SSCs) in the prototypical starburst merger, the Antennae Galaxies. These SSCs are young (3-7 Myr old) and massive (10^5 - 10^7 M_sun for a Kroupa IMF) and their spectra are characterized by broad, extended Br-gamma emission, so we refer to them as emission-line clusters (ELCs) to distinguish them from older SSCs. The Brgamma lines of most ELCs have supersonic widths (60-110 km/s FWHM) and non-Gaussian wings whose velocities exceed the clusters' escape velocities. This high-velocity unbound gas is flowing out in winds that are powered by the clusters' massive O and W-R stars over the course of at least several crossing times. The large sizes of some ELCs relative to those of older SSCs may be due to expansion caused by these outflows; many of the ELCs may not survive as bound stellar systems, but rather dissipate rapidly into the field population. The observed tendency of older ELCs to be more compact than young ones is consistent with the preferential survival of the most concentrated clusters at a given age.Comment: Accepted to Ap

New bis(2-aminoimidazoline) and bisguanidine DNA minor groove binders with potent in vivo antitrypanosomal and antiplasmodial activity

A series of 75 guanidine and 2-aminoimidazoline analogue molecules were assayed in vitro against Trypanosoma brucei rhodesiense STIB900 and Plasmodium falciparum K1. The dicationic diphenyl compounds exhibited the best activities with IC50 values against T. b. rhodesiense and P. falciparum in the nanomolar range. Five compounds (7b, 9a, 9b, 10b, and 14b) cured 100% of treated mice upon ip administration at 20 mg/kg in the difficult to cure T. b. rhodesiense STIB900 mouse model. Overall, the compounds that bear the 2-aminoimidazoline cations benefit from better safety profiles than the guanidine counterparts. The observation of a correlation between DNA binding affinity at AT sites and trypanocidal activity for three series of compounds supported the view of a mechanism of antitrypanosomal action due in part to the formation of a DNA complex. No correlation between antiplasmodial activity and in vitro inhibition of ferriprotoporphyrin IX biomineralisation was observed, suggesting that additional mechanism of action is likely to be involved. © 2008 American Chemical Society.Peer Reviewe

A multi-transition HCN and HCO+ study of 12 nearby active galaxies: AGN versus SB environments

Recent studies have indicated that the HCN-to-CO(J=1-0) and HCO+-to-HCN(J=1-0) ratios are significantly different between galaxies with AGN (active galactic nucleus) and SB (starburst) signatures. In order to study the molecular gas properties in active galaxies and search for differences between AGN and SB environments, we observed the HCN(J=1-0), (J=2-1), (J=3-2), HCO+(J=1-0) and HCO+(J=3-2), emission with the IRAM 30m in the centre of 12 nearby active galaxies which either exhibit nuclear SB and/or AGN signatures. Consistent with previous results, we find a significant difference of the HCN(J=2-1)-to-HCN(J=1-0), HCN(J=3-2)-to-HCN(J=1-0), HCO+(J=3-2)-to-HCO+(J=3-2), and HCO+-to-HCN intensity ratios between the sources dominated by an AGN and those with an additional or pure central SB: the HCN, HCO+ and HCO+-to-HCN intensity ratios tend to be higher in the galaxies of our sample with a central SB as opposed to the pure AGN cases which show rather low intensity ratios. Based on an LVG analysis of these data, i.e., assuming purely collisional excitation, the (average) molecular gas densities in the SB dominated sources of our sample seem to be systematically higher than in the AGN sources. The LVG analysis seems to further support systematically higher HCN and/or lower HCO+ abundances as well as similar or higher gas temperatures in AGN compared to the SB sources of our sample. Also, we find that the HCN-to-CO ratios decrease with increasing rotational number J for the AGN while they stay mostly constant for the SB sources.Comment: accepted for publication in ApJ; 20 pages, 7 figures; in emulateApJ forma

Dense Molecular Gas Associated with the Circumnuclear Star Forming Ring in the Barred Spiral Galaxy NGC 6951

We present high resolution (3" - 5") observations of CO(1-0) and HCN(1-0) emission from the circumnuclear star forming ring in the barred spiral galaxy NGC 6951, a host of a type-2 Seyfert, using the Nobeyama Millimeter Array and 45 m telescope. We find that most of the HCN emission is associated with the circumnuclear ring, where vigorous star formation occurs. The HCN to CO integrated intensity ratio is also enhanced in the star forming ring; the peak value of HCN/CO ratio is 0.18, which is comparable to the ratio in the starbursts NGC 253 and M82. The formation mechanism of dense molecular gas has been investigated. We find that the shocks along the orbit crowding do not promote the formation of the dense molecular gas effectively but enhance the presence of low density GMCs. Instead, gravitational instabilities of the gas can account for the dense molecular gas formation. The HCN/CO ratio toward the Seyfert nucleus of NGC 6951 is a rather normal value (0.086), in contrast with other Seyferts NGC 1068 and M51 where extremely high HCN/CO value of ~ 0.5 have been reported.Comment: 33 pages, 17 figures, to appear in the Astrophysical Journa