VLT spectroscopy of globular clusters in the Sombrero galaxy

We have obtained intermediate-resolution VLT spectroscopy of 75 globular cluster candidates around the Sa galaxy M104 (NGC4594). Fifty-seven candidates out to ~ 40 kpc in the halo of the galaxy were confirmed to be bona-fide globular clusters, 27 of which are new. A first analysis of the velocities provides only marginal evidence for rotation of the cluster system. From Hbeta line strengths, almost all of the clusters in our sample have ages that are consistent, within the errors, with Milky Way globular clusters. Only a few clusters may be 1-2 Gyr old, and bulge and halo clusters appear coeval. The absorption line indices follow the correlations established for the Milky Way clusters. Metallicities are derived based upon new empirical calibrations with Galactic globular clusters taking into account the non-linear behavior of some indices (e.g., Mg2). Our sample of globular clusters in NGC4594 spans a metallicity range of -2.13 < [Fe/H] < +0.26 dex, and the median metallicity of the system is [Fe/H] = -0.85. Thus, our data provide evidence that some of the clusters have super-solar metallicity. Overall, the abundance distribution of the cluster system is consistent with a bimodal distribution with peaks at [Fe/H] ~- 1.7 and -0.7. However, the radial change in the metallicity distribution of clusters may not be straightforwardly explained by a varying mixture of two sub-populations of red and blue clusters.Comment: 6 pages (incl. 4 figures) to appear in the proceedings of the ESO workshop "Extragalactic Globular Cluster Systems", ESO Astrophysics Symp., Garching bei Muenchen (Germany), ed. Kissler-Patig M., Springer-Verlag: Heidelber

Design Oriented Aerodynamic Modelling of Wind Turbine Performance

The development of a wind turbine aerodynamics model using a Boundary Integral Equation model (BIEM) is presented. The methodology is valid to study inviscid unsteady &#64258;ows around three dimensional bodies of arbitrary shape and arbitrarily moving with respect to the incoming &#64258;ow. The extension of this methodology to study viscosity e&#64256;ects in turbine blade &#64258;ow at high angle of attack is addressed and an approach to determine aerodynamic loads over a wide range of turbine operating conditions is proposed. Numerical applications considering a selected test cases from the NREL experimental dataset are presented. Finally, the application of the proposed turbine aerodynamics model into a multi-disciplinary study including aeroelasticity of pylon-turbine assembly and aeroacoustics modelling of induced noise is brie&#64258;y described

Comparison between 1-D and grey-box models of a SOFC

Solid Oxide Fuel Cells (SOFCs) have shown unique performance in terms of greater electrical efficiency and thermochemical integrity with the power systems compared to gas turbines and internal combustion engines. Nonetheless, simple and reliable models still must be defined. In this paper, a comparison between a grey-box model and a 1-D model of a SOFC is performed to understand the impact of the heat transfer inside the cell on the internal temperature distribution of the solid electrolyte. Hence, a significant internal temperature peak of the solid electrolyte is observed for a known difference between anode and cathode inlet temperatures. Indeed, it highlights the difference between the 1-D model and the grey-box model regarding the thermal conditioning of the SOFC. Therefore, the results of this study can be used to investigate the reliability of the thermal results of box models in system-level simulations

Spectroscopy of very hot plasma in non-flaring parts of a solar limb active region: spatial and temporal properties

In this work we investigate the thermal structure of an off-limb active region in various non-flaring areas, as it provides key information on the way these structures are heated. In particular, we concentrate in the very hot component (>3 MK) as it is a crucial element to discriminate between different heating mechanisms. We present an analysis using Fe and Ca emission lines from both SOHO/SUMER and HINODE/EIS. A dataset covering all ionization stages from Fe X to Fe XIX has been used for the thermal analysis (both DEM and EM). Ca XIV is used for the SUMER-EIS radiometric cross-calibration. We show how the very hot plasma is present and persistent almost everywhere in the core of the limb AR. The off-limb AR is clearly structured in Fe XVIII. Almost everywhere, the EM analysis reveals plasma at 10 MK (visible in Fe XIX emission) which is down to 0.1% of EM of the main 3 MK plasma. We estimate the power law index of the hot tail of the EM to be between -8.5 and -4.4. However, we leave an open question on the possible existence of a small minor peak at around 10 MK. The absence in some part of the AR of Fe XIX and Fe XXIII lines (which fall into our spectral range) enables us to determine an upper limit on the EM at such temperatures. Our results include a new Ca XIV 943.59 \AA~ atomic model

Remote light source for silicon photonic transceivers in mobile fronthaul applications

The design and experimental characterisation of a depolarised light source for feeding a remote transceiver based on silicon photonics are presented. Since the transceiver only works in TE mode, the source is designed to deliver, over up to 10 km standard single-mode fibre links, a continuous-wave light with almost constant power along this polarisation direction, whatever be the random polarisation rotation because of the fibre link. The depolarised light source is realised by combining the output of two independent distributed feedback lasers, having orthogonal polarisation and controlled frequency difference. The transmission performance and stability of the remote light source are successfully tested

Musculoskeletal disorders among robotic surgeons: A questionnaire analysis

Objective: Robotic surgical systems offer better workplace in order to relieve surgeons from prolonged physical efforts and improve their surgical outcomes. However, robotic surgery could produce musculoskeletal disorders due to the prolonged sitting position of the operator, the fixed position of the console viewer and the movements of the limbs. Until today, no one study has been reported concerning the association between robotics and musculoskeletal pain. The aim of this work was verify the prevalence of musculoskeletal disorders among Italian robotic surgeons. Material and methods: Between July 2011 and April 2012 a modified Standardized Nordic Questionnaire was delivered to thirty-nine Italian robotic centres. Twentytwo surgeons (56%) returned the questionnaires but only seventeen questionnaires (43.5%) were evaluable. Results: Seven surgeons (41.2%) reported musculoskeletal disorders, by since their first use of the robot which significantly persisted during the daily surgical activity (P &lt; 0.001). Regarding the body parts affected, musculoskeletal disorders were mainly reported in the cervical spine (29.4%) and in the upper limbs (23.5%). Six surgeons (35.3%) defined the robotic console as less comfortable or neither comfortable/uncomfortable with a negative influence on their surgical procedures. Conclusions: In spite of some important limitations, our data showed musculoskeletal disorders due to posture discomfort with negative impact on daily surgical activity among robotic surgeons. These aspects could be due to the lack of ergonomic seat and to the fixed position of the console viewer which could have produced an inadequate spinal posture. The evaluation of these postural factors, in particular the development of an integrated and more ergonomic chair, could further improve the comfort feeling of the surgeon at the console and probably his surgical outcomes