Ghosts of Milky Way's past: the globular cluster ESO 37-1 (E 3)

Context. In the Milky Way, most globular clusters are highly conspicuous objects that were found centuries ago. However, a few dozen of them are faint, sparsely populated systems that were identified largely during the second half of the past century. One of the faintest is ESO 37-1 (E 3) and as such it remains poorly studied, with no spectroscopic observations published so far, although it was discovered in 1976. Aims. We investigate the globular cluster E 3 in an attempt to better constrain its fundamental parameters. Spectroscopy of stars in the field of E 3 is shown here for the first time. Methods. Deep, precise VI CCD photometry of E 3 down to V=26 mag is presented and analysed. Low-resolution, medium signal-to-noise ratio spectra of nine candidate members are studied to derive radial velocity and metallicity. Proper motions from the UCAC4 catalogue are used to explore the kinematics of the bright members of E 3. Results. Isochrone fitting indicates that E 3 is probably very old, with an age of about 13 Gyr; its distance from the Sun is nearly 10 kpc. It is also somewhat metal rich with [Fe/H]=-0.7. Regarding its kinematics, our tentative estimate for the proper motions is (-7.0+/-0.8, 3.5+/-0.3) mas/yr (or a tangential velocity of 382+/-79 km/s) and for the radial velocity is 45+/-5 km/s, in the solar rest frame. Conclusions. E 3 is one of the most intriguing globular clusters in the Galaxy. Having an old age and being metal rich is clearly a peculiar combination, only seen in a handful of objects like the far more conspicuous NGC 104 (47 Tucanae). In addition, its low luminosity and sparse population make it a unique template for the study of the final evolutionary phases in the life of a star cluster. Unfortunately, E 3 is among the most elusive and challenging known globular clusters because field contamination severely hampers spectroscopic studies.Comment: 7 pages, 6+1 figures, 2 tables. Accepted for publication in Astronomy and Astrophysics. Minor change

NGC 5385, NGC 2664 and Collinder 21: three candidate Open Cluster Remnants

We present CCD UBVI photometric and medium/high resolution spectroscopic observations obtained in the field of the previously unstudied dissolving open cluster candidates NGC 5385, NGC 2664 and Collinder~21. Our analysis stands on the discussion of star counts, photometry, radial velocity distribution, and proper motions available from the Tycho~2 catalogue. All the three aggregates clearly emerge from the mean Galactic field, but, regrettably, the close scrutiny of proper motions and radial velocities reveals that we are not facing any physical group. Instead, what we are looking at are just chance alignments of a few bright unrelated stars. Our analysis casts some doubt on the Bica et al. (2001) criterion to look for Possible Open Cluster Remnants. It seems mandatory to define a better criterion to adopt for further investigations.Comment: 12 pages, 12 eps figures (7, 9 and 11 degraded in resolution), accepted for publication in Astronomy & Astrophysic

Making shipping greener: A vessel’s waste heat recovery system comparative study between organic fluids and water

The largest source of energy loss in a ship is found in the propulsion system. This study focuses on the concept of managing waste heat energy from the exhaust gas. Using waste heat recovery systems to make shipping more efficient represents a good area of opportunity for achieving the shipping industry’s green objectives. Organic Rankine Cycles (ORC) have been applied in land based systems before, showing improvements in performance when compared with the traditional Rankine cycle (RC). ORC plants on board ships face different challenges such as variable operating conditions and limited space. As marine environmental rules require greener vessels and engine thermal efficiency continue to increase, ORC waste heat recovery systems become a more attractive option. The proposed waste heat recovery system (WHRS) was modelled using Matlab with a typical ship installation with a slow speed diesel engine and the WHRS installed after the turbo compressors in the exhaust gas system. The energy recovered from the exhaust gas flow is transformed via the thermodynamic cycle into electricity which will help to cover the ship’s demand. The Matlab code found the highest electric power output varying the WHRS high pressure, maximizing the fuel and CO2 emission reductions. Water and various organic fluids were considered as working fluids and their performance compared over a range of different engine operating scenarios in order to assess the differences between a marine ORC and RC. A representative ship operating profile and a typical marine generator were used to measure CO2 emission reductions and the implications of having flammable organic fluids on-board. This work demonstrates that a simple ORC can be more effective than water based RC for the same engine operating condition

Absolute reliability and concurrent validity of hand held dynamometry and isokinetic dynamometry in the hip, knee and ankle joint: Systematic review and meta-analysis

Indexación: Scopus.The purpose of the study is to establish absolute reliability and concurrent validity between hand-held dynamometers (HHDs) and isokinetic dynamometers (IDs) in lower extremity peak torque assessment. Medline, Embase, CINAHL databases were searched for studies related to psychometric properties in muscle dynamometry. Studies considering standard error of measurement SEM (%) or limit of agreement LOA (%) expressed as percentage of the mean, were considered to establish absolute reliability while studies using intra-class correlation coefficient (ICC) were considered to establish concurrent validity between dynamometers. In total, 17 studies were included in the meta-analysis. The COSMIN checklist classified them between fair and poor. Using HHDs, knee extension LOA (%) was 33.59%, 95% confidence interval (CI) 23.91 to 43.26 and ankle plantar flexion LOA (%) was 48.87%, CI 35.19 to 62.56. Using IDs, hip adduction and extension; knee flexion and extension; and ankle dorsiflexion showed LOA (%) under 15%. Lower hip, knee, and ankle LOA (%) were obtained using an ID compared to HHD. ICC between devices ranged between 0.62, CI (0.37 to 0.87) for ankle dorsiflexion to 0.94, IC (0.91to 0.98) for hip adduction. Very high correlation were found for hip adductors and hip flexors and moderate correlations for knee flexors/extensors and ankle plantar/dorsiflexors.https://www.degruyter.com/view/j/med.2017.12.issue-1/med-2017-0052/med-2017-0052.xm