A Large-scale Test Facility for Heat Load Measurements down to 1.9 K

Laboratory-scale tests aimed at minimizing the thermal loads of the LHC magnet cryostat have gone along with the development of the various mechanical components. For final validation of the industrial design with respect to heat inleaks between large surfaces at different temperatures, a full-scale test cryostat has been constructed. The facility reproduces the same pattern of temperature levels as the LHC dipole cryostat, avoiding the heat inleaks from local components like supports and feedthroughs and carefully minimizing fringe effects due to the truncated geometry of the facility with respect to the LHC cryostats serial layout. Thermal loads to the actively cooled radiation screen, operated between 50 K and 65 K, are measured by enthalpy difference along its length. At 1.9 K, the loads are obtained from the temperature difference across a superfluid helium exchanger. On the beam screen, the electrical power needed to stabilize the temperature at 20 K yields a direct reading of the heat losses. Precise in-situ calibration is achieved by subcooling the thermal screen, thereby zeroing radiative heat loads. Minimizing fringe effects has been rewarded by a high precision measurement, yielding one of the more accurate quantifications to date of an industrial application of MLI. The influence of possible openings in the thermal screen is monitored both at the 1.9 K bath and with a radiation sensitive bolometer

Suppression of the near-infrared OH night sky lines with fibre Bragg gratings - first results

The background noise between 1 and 1.8 microns in ground-based instruments is dominated by atmospheric emission from hydroxyl molecules. We have built and commissioned a new instrument, GNOSIS, which suppresses 103 OH doublets between 1.47 - 1.7 microns by a factor of ~1000 with a resolving power of ~10,000. We present the first results from the commissioning of GNOSIS using the IRIS2 spectrograph at the AAT. The combined throughput of the GNOSIS fore-optics, grating unit and relay optics is ~36 per cent, but this could be improved to ~46 per cent with a more optimal design. We measure strong suppression of the OH lines, confirming that OH suppression with fibre Bragg gratings will be a powerful technology for low resolution spectroscopy. The integrated OH suppressed background between 1.5 and 1.7 microns is reduced by a factor of 9 compared to a control spectrum using the same system without suppression. The potential of low resolution OH suppressed spectroscopy is illustrated with example observations. The GNOSIS background is dominated by detector dark current below 1.67 microns and by thermal emission above 1.67 microns. After subtracting these we detect an unidentified residual interline component of ~ 860 +/ 210 ph/s/m^2/micron/arcsec^2. This component is equally bright in the suppressed and control spectra. We have investigated the possible source of the interline component, but were unable to discriminate between a possible instrumental artifact and intrinsic atmospheric emission. Resolving the source of this emission is crucial for the design of fully optimised OH suppression spectrographs. The next generation OH suppression spectrograph will be focussed on resolving the source of the interline component, taking advantage of better optimisation for a FBG feed. We quantify the necessary improvements for an optimal OH suppressing fibre spectrograph design.Comment: Accepted for publication in MNRAS. 15 pages, 18 figure

The case for OH suppression at near-infrared wavelengths

We calculate the advances in near-infrared astronomy made possible through the use of fibre Bragg gratings to selectively remove hydroxyl emission lines from the night sky spectrum. Fibre Bragg gratings should remove OH lines at high resolution (R=10,000), with high suppression (30dB) whilst maintaining high throughput (~90 per cent) between the lines. Devices currently under construction should remove 150 lines in each of the J and H bands, effectively making the night sky surface brightness ~4 magnitudes fainter. This background reduction is greater than the improvement adapative optics makes over natural seeing; photonic OH suppression is at least as important as adaptive optics for the future of cosmology. We present a model of the NIR sky spectrum, and show that the interline continuum is very faint (~80 ph/s/m^s/arcsec/micron on the ecliptic plane). We show that OH suppression by high dispersion, i.e. `resolving out' the skylines, cannot obtain the required level of sensitivity to reach the interline continuum due to scattering of light. The OH lines must be suppressed prior to dispersion. We have simulated observations employing fibre Bragg gratings of first light objects, high redshift galaxies and cool, low-mass stars. The simulations are of complete end-to-end systems from object to detector. The results demonstrate that fibre Bragg grating OH suppression will significantly advance our knowledge in many areas of astrophysics, and in particular will enable rest-frame ultra-violet observations of the Universe at the time of first light and reionisation.Comment: Accepted for publication in MNRA

Monitoring biosecurity in poultry production: an overview of databases reporting biosecurity compliance from seven European countries

Compliance with required on-farm biosecurity practices reduces the risk of contamination and spread of zoonotic and economically important diseases. With repeating avian influenza epidemics in the poultry industry, the need to monitor and improve the overall level of biosecurity is increasing. In practice, biosecurity compliance is assessed by various actors (e.g., academic, private and public institutions), and the results of such assessments may be recorded and gathered in databases which are seldom shared or thoroughly analyzed. This study aimed to provide an inventory of databases related to the assessment of biosecurity in poultry farms in seven major poultry-producing European countries to highlight challenges and opportunities associated with biosecurity data collection, sharing, and use. The institutions in charge of these databases were contacted and interviewed using a structured questionnaire to gather information on the main characteristics of the databases and the context of their implementation. A total of 20 databases were identified, covering the gamut of poultry species and production types. Most databases were linked to veterinary health authorities or academia, and to a lesser extent interbranch organizations. Depending on the institutions in charge, the databases serve various purposes, from providing advice to enforcing regulations. The quality of the biosecurity data collected is believed to be quite reliable, as biosecurity is mostly assessed by trained farm advisors or official veterinarians and during a farm visit. Some of the databases are difficult to analyze and/or do not offer information concerning which biosecurity measures are most or least respected. Moreover, some key biosecurity practices are sometimes absent from certain databases. Although the databases serve a variety of purposes and cover different production types, each with specific biosecurity features, their analysis should help to improve the surveillance of biosecurity in the poultry sector and provide evidence on the benefits of biosecurity

M31N 2008-12a - the remarkable recurrent nova in M31: Pan-chromatic observations of the 2015 eruption

The Andromeda Galaxy recurrent nova M31N 2008-12a had been observed in eruption ten times, including yearly eruptions from 2008-2014. With a measured recurrence period of $P_\mathrm{rec}=351\pm13$ days (we believe the true value to be half of this) and a white dwarf very close to the Chandrasekhar limit, M31N 2008-12a has become the leading pre-explosion supernova type Ia progenitor candidate. Following multi-wavelength follow-up observations of the 2013 and 2014 eruptions, we initiated a campaign to ensure early detection of the predicted 2015 eruption, which triggered ambitious ground and space-based follow-up programs. In this paper we present the 2015 detection; visible to near-infrared photometry and visible spectroscopy; and ultraviolet and X-ray observations from the Swift observatory. The LCOGT 2m (Hawaii) discovered the 2015 eruption, estimated to have commenced at Aug. $28.28\pm0.12$ UT. The 2013-2015 eruptions are remarkably similar at all wavelengths. New early spectroscopic observations reveal short-lived emission from material with velocities $\sim13000$ km s$^{-1}$, possibly collimated outflows. Photometric and spectroscopic observations of the eruption provide strong evidence supporting a red giant donor. An apparently stochastic variability during the early super-soft X-ray phase was comparable in amplitude and duration to past eruptions, but the 2013 and 2015 eruptions show evidence of a brief flux dip during this phase. The multi-eruption Swift/XRT spectra show tentative evidence of high-ionization emission lines above a high-temperature continuum. Following Henze et al. (2015a), the updated recurrence period based on all known eruptions is $P_\mathrm{rec}=174\pm10$ d, and we expect the next eruption of M31N 2008-12a to occur around mid-Sep. 2016

Sex Determination:Why So Many Ways of Doing It?

Sexual reproduction is an ancient feature of life on earth, and the familiar X and Y chromosomes in humans and other model species have led to the impression that sex determination mechanisms are old and conserved. In fact, males and females are determined by diverse mechanisms that evolve rapidly in many taxa. Yet this diversity in primary sex-determining signals is coupled with conserved molecular pathways that trigger male or female development. Conflicting selection on different parts of the genome and on the two sexes may drive many of these transitions, but few systems with rapid turnover of sex determination mechanisms have been rigorously studied. Here we survey our current understanding of how and why sex determination evolves in animals and plants and identify important gaps in our knowledge that present exciting research opportunities to characterize the evolutionary forces and molecular pathways underlying the evolution of sex determination

Revision du statut taxonomique de quelques Noctuidae palearctiques. (Seconde note preliminaire)

Volume: 8Start Page: 172End Page: 17