Near-Infrared spectroscopy of the super star cluster in NGC1705

We study the near-infrared properties of the super star cluster NGC1750-1 in order to constrain its spatial extent, its stellar population and its age. We use adaptive optics assisted integral field spectroscopy with SINFONI on the VLT. We estimate the spatial extent of the cluster and extract its K-band spectrum from which we constrain the age of the dominant stellar population. Our observations have an angular resolution of about 0.11", providing an upper limit on the cluster radius of 2.85+/-0.50 pc depending on the assumed distance. The K-band spectrum is dominated by strong CO absorption bandheads typical of red supergiants. Its spectral type is equivalent to a K4-5I star. Using evolutionary tracks from the Geneva and Utrecht groups, we determine an age of 12+/-6 Myr. The large uncertainty is rooted in the large difference between the Geneva and Utrecht tracks in the red supergiants regime. The absence of ionized gas lines in the K-band spectrum is consistent with the absence of O and/or Wolf-Rayet stars in the cluster, as expected for the estimated age.Comment: 5 pages, 4 figures. Research Note accepted in Astronomy and Astrophysic

Measurement model equivalence in web- and paper-based surveys

The aim of this research is to investigate whether web-basedand paper-based organisational climate surveys can be regardedas equivalent techniques of data collection. Due to the complexgeographical placement of various units of the participatingorganisation and limited internet access, both paper-based andweb-based questionnaires were used. Overall, 1295 employeesparticipated in the survey; of these, 899 used paper questionnairesand 396 used the web-based questionnaire.9Confi rmatory factor analysis (CFA) in a Structural Equation Modelling(SEM) framework was used to test the tenability of a series ofincreasingly restrictive models, using goodness-of-fi t tests.10The SurveyTracker software survey package was used for the websurvey, and SPSS with LISREL was used for the statistical analysis.Several measurement models were tested; four models showed verygood fi ts for both the web-based and paper-based surveys for fi tmeasures such as RMSEA, NFI, NNFI, PNFI CFI, IFI, RFI and BIC. Thefour path diagrams also allowed the researcher to investigate the twogroups of participants’ responses and fi t measures across diff erentaspects of the organisation, such as strategic issues (4 dimensions),human resource issues (4 dimensions), operational issues and jobsatisfaction (5 dimensions), and leadership and transformationalissues (7 dimensions).11The results indicate that hypotheses H1 to H3 are all tenable. Itcan therefore be concluded that the web-based and paper-basedsurveys can be considered equal with respect to similar factor structure, with equal factor loadings and equal variances of thefactors and equal covariances between the factors. The results maytherefore be combined in a single analysis without compromisingmeasurement validity

Impact of aging on the auditory system and related cognitive functions: A narrative review

Age-related hearing loss (ARHL), presbycusis, is a chronic health condition that affects approximately one-third of the world’s population. The peripheral and central hearing alterations associated with age-related hearing loss have a profound impact on perception of verbal and non-verbal auditory stimuli. The high prevalence of hearing loss in the older adults corresponds to the increased frequency of dementia in this population. Therefore, researchers have focused their attention on age-related central effects that occur independent of the peripheral hearing loss as well as central effects of peripheral hearing loss and its association with cognitive decline and dementia. Here we review the current evidence for the age-related changes of the peripheral and central auditory system and the relationship between hearing loss and pathological cognitive decline and dementia. Furthermore, there is a paucity of evidence on the relationship between ARHL and established biomarkers of Alzheimer’s disease, as the most common cause of dementia. Such studies are critical to be able to consider any causal relationship between dementia and ARHL. While this narrative review will examine the pathophysiological alterations in both the peripheral and central auditory system and its clinical implications, the question remains unanswered whether hearing loss causes cognitive impairment or vice versa

Properties of massive stars in four clusters of the VVV survey

The evolution of massive stars is only partly understood. Observational constraints can be obtained from the study of massive stars located in young massive clusters. The ESO Public Survey VISTA Variables in the Via Lactea (VVV) discovered several new clusters hosting massive stars. We present an analysis of massive stars in four of these new clusters. Our aim is to provide constraints on stellar evolution and to better understand the relation between different types of massive stars. We use the radiative transfer code CMFGEN to analyse K-band spectra of twelve stars with spectral types ranging from O and B to WN and WC. We derive the stellar parameters of all targets as well as surface abundances for a subset of them. In the Hertzsprung-Russell diagram, the Wolf-Rayet stars are more luminous or hotter than the O stars. From the log(C/N) - log(C/He) diagram, we show quantitatively that WN stars are more chemically evolved than O stars, WC stars being more evolved than WN stars. Mass loss rates among Wolf-Rayet stars are a factor of 10 larger than for O stars, in agreement with previous findings.Comment: paper accepted in New Astronom