The embedded cluster or association Trumpler 37 in IC1396: a search for evolutionary constraints

It is currently widely accepted that open star clusters and stellar associations result from the evolution of embedded star clusters. Parameters such star formation efficiency, time-scale of gas removal and velocity dispersion can be determinants of their future as bound or unbound systems. Finding objects at an intermediate evolution state can provide constraints to model the embedded cluster evolution. In the HII region IC1396, Trumpler 37 is an extended young cluster that presents characteristics of an association. We employed the Two Micron All Sky Survey (2MASS) photometry to analysing its structure and stellar content, and determining its astrophysical parameters. We also analysed 11 bright-rimmed clouds in IC1396 in order to search for young infrared star clusters, and the background open star cluster Teutsch 74, to verify whether it has any contribution to the observed stellar density profile of Trumpler 37. The derived parameters and comparison with template objects from other studies lead us to conclude that Trumpler 37, rather than as a star cluster, will probably emerge from its molecular cloud as an OB association.Comment: 13 pages, 10 figures, 6 table

Experiences with high definition interactive video conferencing

We review the design and implementation of UltraGrid, a new high definition video conferencing system, and present some experimental results. UltraGrid was the first system to support gigabit rate high definition interactive video conferencing on commodity systems and networks, and we present measurements to illustrate behavior of production networks subject to such real time traffic. We illustrate the benefits of hybrid IP/provisioned optical networks over best effort IP networks for this class of traffic, and motivate the development of congestion control algorithms for interactive conferencing on best effort IP networks

A taxonomy of interactions in socio-technical systems: A functional perspective

Although the modelling of interactions has long been at the core of socio-technical systems theory, and is a key for understanding resilience, there is a lack of a holistic taxonomy of interactions. This study introduces a taxonomy of interactions to be used in association with the Functional Resonance Analysis Method (FRAM). The taxonomy has nine criteria: nature of agents, output nature, levelling, waiting time, distance, degree of coupling, visibility, safety and/or security hazards, and parallel replications. For each criterion, two descriptors are proposed: what the interaction looks like; and - when applicable - the variability level of the interaction. The use of the taxonomy is presented for three systems with clearly distinct complexity characteristics: cash withdrawal from an ATM, teaching a university course, and manufacturing operations. These case studies indicate the usefulness of the taxonomy for the identification of leverage points in work system design. They also show the value of modelling the variability of the interactions in FRAM models, in addition to the traditional modelling of the variability of the outputs of functions. Implications of the taxonomy for resilience engineering are discussed

Monitor, anticipate, respond, and learn: developing and interpreting a multilayer social network of resilience abilities

Resilient performance is influenced by social interactions of several types, which may be analysed as layers of interwoven networks. The combination of these layers gives rise to a “network of networks”, also known as a multilayer network. This study presents an approach to develop and interpret multilayer networks in light of resilience engineering. Layers correspond to the four abilities of resilient systems: monitor, anticipate, respond, and learn. The proposal is applied in a 34-bed intensive care unit. To map relationships between actors in each layer, a questionnaire was devised and answered by 133 staff members, including doctors, nurses, nurse technicians, and allied health professionals. Two multilayer networks were developed: one considering that actors are 100% available and reliable (work-as-imagined) and another considering suboptimal availability and reliability (work-as-done). The multilayer networks were analysed through actor-centred (Katz centrality, degree deviation, and neighbourhood centrality) and layer-centred metrics (inter-layer correlation, and assortativity correlation). Strengths and weaknesses of social interactions at the ICU are discussed based on the adopted metrics

Star clusters in the Sh2-132 complex: clues about the connection between embedded and open clusters

Embedded clusters are formed in molecular clouds where massive stars can produce HII regions. The detailed embedded-open cluster evolutionary connection as well as the origin of associations are yet to be unveiled. There appears to be a high infant mortality rate among embedded clusters and the few survivors evolve to open clusters. We study the colour-magnitude diagrams and structure of the star clusters related to the Sh2-132 HII region using the 2MASS database. Cluster fundamental and structural parameters are determined via MS and PMS isochrones and stellar radial density profiles. We report the discovery of four clusters. One of them is projected a few diameters away from the optical cluster Teutsch\,127 and appears to be deeply embedded, seen only in the infrared. Evidence is found that we are witnessing the dynamical transition from an embedded to an open cluster. An additional cluster is also close to Teutsch\,127 and might be associated with a bow-shock. We also study the CMD and structure of the open cluster Berkeley\,94 in Sh2-132 and a new cluster which is projected in the outskirts of the complex. Finally, we searched for star clusters around the two known Wolf-Rayet stars in the complex. One of them appears to be related to a compact cluster. Finally, the present analyses suggest early dynamical evolution for young star clusters.Comment: 12 pages, 20 figures, 6 table

Structures in surface-brightness profiles of LMC and SMC star clusters: evidence of mergers?

The LMC and SMC are rich in binary star clusters, and some mergers are expected. It is important to characterize single clusters, binary clusters and candidates to mergers. We selected a sample of star clusters in each Cloud with this aim. Surface photometry of 25 SMC and 22 LMC star clusters was carried with the ESO Danish 1.54 m telescope. 23 clusters were observed for the first time for these purposes. We fitted Elson, Fall and Freeman (1987, EFF) profiles to the data, deriving structural parameters, luminosities and masses. We also use isophotal maps to constrain candidates to cluster interactions.} {The structural parameters, luminosities and masses presented good agreement with those in the literature. Three binary clusters in the sample have a double profile. Four clusters (NGC 376, K 50, K 54 and NGC 1810) do not have companions and present as well important deviations from EFF profiles. The present sample contains blue and red Magellanic clusters. Extended EFF profiles were detected in some blue clusters. We find evidence that important deviations from the body of EFF profiles might be used as a tool to detect cluster mergers.Comment: 16 pages and 8 figures. Accepted by A&