Morphologies and ages of star cluster pairs and multiplets in the Small Magellanic Cloud

An isophotal atlas of 75 star cluster pairs and multiplets in the Small Magellanic Cloud is presented, comprising 176 objects. They are concentrated in the SMC main body. The isophotal contours were made from Digitized Sky Survey images and showed relevant structural features possibly related to interactions in about 25% of the sample. Previous N-body simulations indicate that such shapes could be due to tidal tails, bridges or common envelopes. The diameter ratio between the members of a pair is preferentially in the range 1 - 2, with a peak at 1. The projected separation is in the range ~ 3 - 22 pc with a pronounced peak at ~ 13 pc. For 91 objects it was possible to derive ages from Colour-Magnitude Diagrams using the OGLE-II photometric survey. The cluster multiplets in general occur in OB stellar associations and/or HII region complexes. This indicates a common origin and suggests that multiplets coalesce into pairs or single clusters in a short time scale. Pairs in the SMC appear to be mostly coeval and consequently captures are a rare phenomenon. We find evidence that star cluster pairs and multiplets may have had an important role in the dynamical history of clusters presently seen as large single objects

Capture of field stars by globular clusters in dense bulge regions

The recent detection of a double Red Giant Branch in the optical color-magnitude diagram (CMD) of the bulge globular cluster HP1 (Ortolani et al. 1997), a more populated metal-poor steep one corresponding to the cluster itself, and another metal-rich curved, led us to explore in the present Letter the possibility of capture of field stars by a globular cluster orbiting in dense bulge regions over several gigayears. Analytical arguments, as well as N-body calculations for a cluster model of 10^5 solar masses in a bulge-like environment, suggest that a significant fraction of cluster stars may consist of captures. Metal-poor globular clusters in the inner bulge, like HP1, contrasting at least in Delta [Fe/H] = 1.0 dex with respect to the surrounding metal-rich stars, are ideal probes to further test the capture scenario. In turn, if this scenario is confirmed, the double RGB of HP1 could provide direct estimates of blanketing amounts, which is fundamental for the photometric calibration of metal-rich stellar populations.Comment: 6 pages, 2 included figures, aas2pp4,sty Latex style. To be published in Astrophysical Journal Letter

Ages and Metallicities of Star Clusters and Surrounding Fields in the Outer Disk of the Large Magellanic Cloud

We present Washington system C,T_1 CMDs of 13 star clusters and their surrounding fields which lie in the outer parts of the LMC disk. Ages are determined by means of the magnitude difference between the giant branch clump and the turnoff, while metallicities are derived from the location of the giant and subgiant branches as compared to fiducial star clusters. We find that in most cases the stellar population of each star cluster is quite similar to that of the field where it is embedded. Three particular fields present remarkable properties: (i) The so far unique cluster ESO121-SC03 at ~9 Gyr has a surrounding field which shares the same properties. (ii) The field surrounding the far eastern intermediate age cluster OHSC37 is noteworthy in the sense that we do not detect any evidence of LMC stars. (iii) The fields of SL388 and SL509 present CMDs with a secondary clump ~0.45 mag fainter than the dominant intermediate age clump, suggesting a stellar population component located behind the LMC disk at a distance comparable to that of the SMC. The mean metallicity derived for the intermediate age outer disk clusters is =-0.7 and for their surrounding fields =-0.6. These values are significantly lower than found by Olszewski et al. (1991, AJ, 101, 515) for a sample of clusters of similar age, but are in good agreement with several recent studies. A few clusters stand out in the age--metallicity relation in the sense that they are intermediate age clusters at relatively low metallicity ([Fe/H]~-1).Comment: LaTeX, to be published in July, 1998 Astronomical Journa

Dissolving star cluster candidates

We present a list of 34 neglected entries from star cluster catalogues located at relatively high galactic latitudes ($|b| >$ 15$^{\circ}$) which appear to be candidate late stages of star cluster dynamical evolution. Although underpopulated with respect to usual open clusters, they still present a high number density contrast as compared to the galactic field. This was verified by means of (i) predicted model counts from different galactic subsystems in the same direction, and (ii) Guide Star Catalog equal solid angle counts for the object and surrounding fields. This suggests that the objects are physical systems, possibly star clusters in the process of disruption or their fossil remains. The sample will be useful for followup studies in view of verifying their physi cal nature.Comment: manuscript in LATEX with 7 pages, 7 figures .ps Accepted for Astronomy and Astrophysics main journa

Multiwavelength star formation indicators: Observations

We present a compilation of multiwavelength data on different star formation indicators for a sample of nearby star forming galaxies. Here we discuss the observations, reductions and measurements of ultraviolet images obtained with STIS, on board the Hubble Space Telescope, ground-based Halpha, and VLA 8.46 GHz radio images. These observations are complemented with infrared fluxes, as well as large aperture optical radio and ultraviolet data from the literature. This database will be used in a forthcoming paper to compare star formation rates at different wavebands. We also present spectral energy distributions (SEDs) for those galaxies with at least one far-infrared measurements from ISO, longward of 100 um. These SEDs are divided in two groups, those which are dominated by the far-infrared emission, and those where the contribution from the far-infrared and optical emission is comparable. These SEDs are useful tools to study the properties of high redshift galaxies.Comment: 39 pages, 17 jpeg figures, 1 eps figure, To appear in ApJS May 200

Impact of the COVID-19 epidemic in Friuli Venezia Giulia Region (Northern Italy): assessment of factors associated with the risk of death by competing risks analysis

OBJECTIVES: to investigate the role of gender, age, province of residence, and nursing home residency on the risk of death for residents in the Friuli Venezia Giulia (FVG) Region (Northern Italy) tested positive for Covid-19, considering recovery as a competing event. The secondary objective is to describe the impact of the Covid-19 epidemic in FVG and in the Regions of Northern and Central Italy in terms of incidence and mortality compared to the national data. DESIGN: retrospective cohort study. SETTING AND PARTICIPANTS: resident population in FVG in the period between 29 February and 25 June 2020. MAIN OUTCOME MEASURES: in order to describe the impact of the Covid-19 outbreak in FVG, in terms of incidence and mortality compared to the national data, the standardized incidence (SIR) and mortality (SMR) ratios and their respective 95% confidence intervals (95%CI) were calculated compared to the Italian population for the northern and central Regions of Italy and the autonomous Provinces (PA) of Trento and Bolzano. A retrospective cohort study was conducted on subjects residing in FVG to whom at least one naso-oropharyngeal swab (hereafter, named swab) resulted positive for Covid-19. For each subject included in the cohort, the observation period started with the first positive swab and ended with the first of the following events: death, recovery or censored, which means that at the end of the observation period the subject was still alive and positive. The cause of death was assigned to Covid-19 if a subject had not yet recovered at the time when the event occurred. Cohort members were considered recovered after two negative consecutive swabs. The sub-hazard ratio (SHR) was estimated by applying the regression model of competing risks by Fine and Gray, in which the event of interest was the death caused by Covid-19 and the competing event was recovery. The explanatory variables included in the multiple models are: gender, age at the beginning of the observation period, the Province of residence, and nursing home residency. The cause-specific hazard was estimated using Cox proportional hazard regression. RESULTS: during the observation period, 3,305 cases and 345 deaths were recorded in FVG; SIR and SMR resulted, respectively, equal to 0.64 (95%CI 0.61-0.68) and 0.43 (95%CI 0.37-0.50). The FVG was the Northern Region one with the lowest incidence and mortality. The cohort consisted of 3,121 residents in FVG with at least one swab with a positive Covid-19 result during the study period. The SHR of dying for Covid-19 is equal to 16.13 (95%CI 9.73-26.74) for people with age 70-79 years and 35.58 (95%CI 21.77-58.15) with age >=80 years respect those with age <70 years. It is higher in males (SHR 1.71; 95%CI 1.34-2.17). There is no evidence that being resident in a nursing home affects the SHR (SHR 0.91 and 95%CI 0.69-1.20). As regards the province as an explanatory variable, the sub-hazard of death in the province of Trieste appears to overlap to the sub-hazard of Pordenone used as a reference; for the provinces of Udine and Gorizia the sub-hazards seem lower than the reference. CONCLUSIONS: while other Northern Regions and autonomous Provinces show higher standardized incidence and mortality compared with Italy, FVG and Veneto do not. In FVG, male gender and age are important determinants of death while there is no evidence that the condition of guest in a nursing home increases the sub-hazard of death

Análisis exploratorio de zonas con diferente probabilidad de ocurrencia del Groundnut ringspot virus en la provincia de Córdoba

La principal región manisera del país se encuentra en la provincia de Córdoba donde la superficie sembrada con este cultivo se localiza, en orden de importancia, en los departamentos Río Cuarto, Gral. Roca, Juárez Celman, Pte. R. Sáenz Peña, Tercero Arriba, Gral. San Martín y Río Segundo. Sin embargo, debido a la necesidad de suelos para los programas de rotación, la superficie sembrada con maní presenta un sostenido aumento en zonas no tradicionales ubicadas en los departamentos Río Primero, Calamuchita, Unión y Marcos Juárez, entre otros. En esta región, el cultivo es afectado por el Groundnut ringspot virus (GRSV), un virus perteneciente al género Orthotospovirus, el cual ha ocasionado epifitias provocando mermas en el rendimiento del cultivo en aquellos lotes afectados. En la naturaleza, este virus es transmitido desde una planta enferma a otra sana únicamente por especies de trips vectores que han adquirido el patógeno durante sus estadios juveniles de desarrollo. La presencia de estos insectos, su dinámica y características poblacionales, sumado a las condiciones climáticas de cada región, constituyen los factores más importantes que determinan el área donde la virosis constituye un riesgo para el cultivo. El objetivo de este trabajo fue comenzar a definir zonas con probabilidad diferencial de ocurrencia de la enfermedad a fin de generar conocimiento epidemiológico para el manejo regional de esta virosis.Instituto de Patología VegetalFil: Dottori, Carolina Andrea. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; ArgentinaFil: Giannini Kurina, F. Universidad Nacional de Córdoba. Facultad de Ciencias Agropecuarias. Cátedra de Estadística y Biometría; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Fitopatología y Modelización Agrícola (UFYMA); Argentina.Fil: Córdoba, M. Universidad Nacional de Córdoba. Facultad de Ciencias Agropecuarias. Cátedra de Estadística y Biometría; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Fitopatología y Modelización Agrícola (UFYMA); Argentina.Fil: Lenardon, Sergio Luis. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; Argentina. Universidad Nacional de Río Cuarto. Facultad de Agronomía y Veterinaria. Departamento Biología Agrícola; ArgentinaFil: De Breuil, Soledad. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Fitopatología y Modelización Agrícola (UFYMA); Argentin

Partial change in EphA4 knockout mouse phenotype: Loss of diminished GFAP upregulation following spinal cord injury

In a previous study we found that the EphA4 receptor inhibits regeneration following spinal cord injury by blocking regrowth of axons and regulation of astrocyte reactivity. In our original studies using EphA4 null mice [Goldshmit et al., J. Neurosci., 2004] we found attenuated astrocyte reactivity following spinal cord injury. Several other studies have now supported the role of EphA4 in regulating neural regeneration but a recent study [Herrmann et al., Exp. Neurol., 2010] did not find an effect of EphA4 on astrocyte reactivity. Re-examination of astrocytic gliosis following injury in our current cohort of EphA4 null mice revealed that they no longer showed attenuation of astrocyte reactivity, however other EphA4 null mouse phenotypes, such as decreased size of the dorsal funiculus were unaltered. We hypothesised that long-term breeding on the C57Bl/6 background may influence the EphA4-mediated astrocyte phenotype and compared astrocytic gliosis at 4 days following spinal cord injury in wildtype and EphA4 null mice on the C57Bl/6 background and backcrossed C57Bl/6×129Sv(F2) mice, as well as wildtype 129Sv mice. 129Sv mice had increased GFAP expression and increased numbers of reactive GFAP astrocytes compared to C57Bl/6 mice. There was no significant effect of EphA4 deletion on GFAP expression in C57Bl/6 mice or the F2 crosses other than a moderately decreased number of EphA4 null astrocytes in C57Bl/6 mice using one of two antibodies. Therefore, there has been an apparent change in EphA4-mediated astroglial phenotype associated with long term breeding of the EphA4 colony but it does not appear to be influenced by background mouse strain