Modelling complex phenomena in optical fibres

We present a new model for predicting the performance of fibre systems in the multimode limit. This is based on ray-­‐tracing but includes a semi-­‐empirical description of Focal Ratio Degradation (FRD). We show how FRD is simulated by the model. With this ability, it can be used to investigate a wide variety of phenomena including scrambling and the loss of light close to the limiting numerical aperture. It can also be used to predict the performance of non-­‐round and asymmetric fibres

Proinflammatory mediator activity, endogenous antagonists and the systemic inflammatory response in intra-abdominal sepsis. Scottish Sepsis Intervention Group.

University Department of Surgery, Royal Infirmary, Edinburgh, UK. BACKGROUND: Severe intra-abdominal sepsis continues to carry a high mortality rate. The physiological response to sepsis in this condition and its relationship with proinflammatory mediators and their endogenous antagonists require further clarification. METHODS: Fifty-seven patients were stratified by Acute Physiology And Chronic Health Evaluation (APACHE) II score at the time of admission to an intensive care unit (group 1, score of less than 20; group 2, score of 20 or more). Serial measurements of clinical and immunological variables were made. RESULTS: Non-survivors from group 2 had a raised acute physiology score (P = 0.01), a higher peak serum interleukin (IL) 6 concentration (P = 0.03) and a depressed level of endogenous immunoglobulin (Ig) G class antiendotoxin core antibody (P = 0.005). In group 1, although organ failure score increased progressively in non-survivors, physiology score and peak IL-6 level were similar to those in survivors, and endogenous IgG class antiendotoxin core antibody titre rose (P = 0.02). In both groups IL-1 and tumour necrosis factor alpha were detected infrequently, but their natural antagonists were present in much higher concentrations in both survivors and non-survivors. Levels of C-reactive protein were raised in both but were not significantly different between survivors and non-survivors. CONCLUSION: During the development of organ failure and death, the pattern of proinflammatory mediators and their endogenous antagonists can vary markedly and may in part be determined by the extent of the initial physiological disturbance

MOONS: a multi-object optical and near-infrared spectrograph for the VLT

MOONS is a new conceptual design for a Multi-Object Optical and Near-infrared Spectrograph for the Very Large Telescope (VLT), selected by ESO for a Phase A study. The baseline design consists of ~1000 fibers deployable over a field of view of ~500 square arcmin, the largest patrol field offered by the Nasmyth focus at the VLT. The total wavelength coverage is 0.8μm-1.8μm and two resolution modes: medium resolution and high resolution. In the medium resolution mode (R~4,000-6,000) the entire wavelength range 0.8μm-1.8μm is observed simultaneously, while the high resolution mode covers simultaneously three selected spectral regions: one around the CaII triplet (at R~8,000) to measure radial velocities, and two regions at R~20,000 one in the J-band and one in the H-band, for detailed measurements of chemical abundances. The grasp of the 8.2m Very Large Telescope (VLT) combined with the large multiplex and wavelength coverage of MOONS - extending into the near-IR - will provide the observational power necessary to study galaxy formation and evolution over the entire history of the Universe, from our Milky Way, through the redshift desert and up to the epoch of re-ionization at z<8-9. At the same time, the high spectral resolution mode will allow astronomers to study chemical abundances of stars in our Galaxy, in particular in the highly obscured regions of the Bulge, and provide the necessary follow-up of the Gaia mission. Such characteristics and versatility make MOONS the long-awaited workhorse near-IR MOS for the VLT, which will perfectly complement optical spectroscopy performed by FLAMES and VIMOS

The ZIMPOL high contrast imaging polarimeter for SPHERE: system test results

SPHERE (Spectro-Polarimetric High-contrast Exoplanet Research) is a new instrument for the VLT aimed at the direct detection of exo-planets. It has received its first light in May 2014. ZIMPOL (Zurich Imaging Polarimeter) is the imaging polarimeter subsystem of the SPHERE instrument. It's capable of both high accuracy and high sensitivity polarimetry but can also be used as a classical imager. It is located behind an extreme AO system and a stellar coronagraph. ZIMPOL operates at visible wavelengths (600-900 nm) which is best suited to detect the very faint reflected and hence polarized visible light from extra solar planets. It has an instantaneous Field of View of 3 x 3 arcsec2 (extendable to 8 arcsec diameter) with an angular resolution of 14 mili-arcsec. We discuss the results that are obtained from the full SPHERE-ZIMPOL system testing. In particular the optical, polarimetric and high contrast performance. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

MOONS: the Multi-Object Optical and Near-infrared Spectrograph for the VLT

MOONS is a new Multi-Object Optical and Near-infrared Spectrograph selected by ESO as a third generation instrument for the Very Large Telescope (VLT). The grasp of the large collecting area offered by the VLT (8.2m diameter), combined with the large multiplex and wavelength coverage (optical to near-IR: 0.8μm - 1.8μm) of MOONS will provide the European astronomical community with a powerful, unique instrument able to pioneer a wide range of Galactic, Extragalactic and Cosmological studies and provide crucial follow-up for major facilities such as Gaia, VISTA, Euclid and LSST. MOONS has the observational power needed to unveil galaxy formation and evolution over the entire history of the Universe, from stars in our Milky Way, through the redshift desert, and up to the epoch of very first galaxies and re-ionization of the Universe at redshift z>8-9, just few million years after the Big Bang. On a timescale of 5 years of observations, MOONS will provide high quality spectra for >3M stars in our Galaxy and the local group, and for 1-2M galaxies at z>1 (SDSS-like survey), promising to revolutionise our understanding of the Universe. The baseline design consists of ~1000 fibers deployable over a field of view of ~500 square arcmin, the largest patrol field offered by the Nasmyth focus at the VLT. The total wavelength coverage is 0.8μm-1.8μm and two resolution modes: medium resolution and high resolution. In the medium resolution mode (R~4,000-6,000) the entire wavelength range 0.8μm-1.8μm is observed simultaneously, while the high resolution mode covers simultaneously three selected spectral regions: one around the CaII triplet (at R~8,000) to measure radial velocities, and two regions at R~20,000 one in the J-band and one in the H-band, for detailed measurements of chemical abundances

Science case and requirements for the MOSAIC concept for a multi-object spectrograph for the European Extremely Large Telescope

Over the past 18 months we have revisited the science requirements for a multi-object spectrograph (MOS) for the European Extremely Large Telescope (E-ELT). These efforts span the full range of E-ELT science and include input from a broad cross-section of astronomers across the ESO partner countries. In this contribution we summarise the key cases relating to studies of high-redshift galaxies, galaxy evolution, and stellar populations, with a more expansive presentation of a new case relating to detection of exoplanets in stellar clusters. A general requirement is the need for two observational modes to best exploit the large (≥40 arcmin2) patrol field of the E-ELT. The first mode (‘high multiplex’) requires integrated-light (or coarsely resolved) optical/near-IR spectroscopy of >100 objects simultaneously. The second (‘high definition’), enabled by wide-field adaptive optics, requires spatially-resolved, near-IR of >10 objects/sub-fields. Within the context of the conceptual study for an ELT-MOS called MOSAIC, we summarise the toplevel requirements from each case and introduce the next steps in the design process

OPTIMOS-EVE design trade-off analysis

OPTIMOS-EVE (OPTical Infrared Multi Object Spectrograph - Extreme Visual Explorer) is the fiber fed multi object spectrograph proposed for the E-ELT. It is designed to provide a spectral resolution ranging from 5000 to 30.000, at wavelengths from 0.37 μm to 1.70 μm, combined with a high multiplex (&gt;200) and a large spectral coverage. The system consists of three main modules: a fiber positioning system, fibers and a spectrograph. The OPTIMOS-EVE Phase-A study, carried out within the framework of the ESO E-ELT instrumentation studies, has been performed by an international consortium consisting of institutes from France, Netherlands, United Kingdom, Italy and Denmark. This paper describes the design tradeoff study and the key issues determining the price and performance of the instrument. © 2010 Copyright SPIE - The International Society for Optical Engineering