| 1. |
- van Cappellen, W., et al.
(författare)
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Apertif: Phased array feeds for the Westerbork Synthesis Radio Telescope: System overview and performance characteristics
- 2022
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 658
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Tidskriftsartikel (refereegranskat)abstract
- We describe the APERture Tile In Focus (Apertif) system, a phased array feed (PAF) upgrade of the Westerbork Synthesis Radio Telescope that transforms this telescope into a high-sensitivity, wide-field-of-view L-band imaging and transient survey instrument. Using novel PAF technology, up to 40 partially overlapping beams are formed on the sky simultaneously, significantly increasing the survey speed of the telescope. With this upgraded instrument, an imaging survey covering an area of 2300 deg2 is being performed that will deliver both continuum and spectral line datasets, of which the first data have been publicly released. In addition, a time domain transient and pulsar survey covering 15 000 deg2 is in progress. An overview of the Apertif science drivers, hardware, and software of the upgraded telescope is presented, along with its key performance characteristics.
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| 2. |
- Adebahr, B., et al.
(författare)
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Apercal - The Apertif calibration pipeline
- 2022
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Ingår i: Astronomy and Computing. - : Elsevier BV. - 2213-1337. ; 38
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Tidskriftsartikel (refereegranskat)abstract
- Apertif (APERture Tile In Focus) is one of the Square Kilometre Array (SKA) pathfinder facilities. The Apertif project is an upgrade to the 50-year-old Westerbork Synthesis Radio Telescope (WSRT) using phased-array feed technology. The new receivers create 40 individual beams on the sky, achieving an instantaneous sky coverage of 6.5 square degrees. The primary goal of the Apertif Imaging Survey is to perform a wide survey of 3500 square degrees (AWES) and a medium deep survey of 350 square degrees (AMES) of neutral atomic hydrogen (up to a redshift of 0.26), radio continuum emission and polarisation. Each survey pointing yields 4.6 TB of correlated data. The goal of Apercal is to process this data and fully automatically generate science ready data products for the astronomical community while keeping up with the survey observations. We make use of common astronomical software packages in combination with Python based routines and parallelisation. We use an object oriented module-based approach to ensure easy adaptation of the pipeline. A Jupyter notebook based framework allows user interaction and execution of individual modules as well as a full automatic processing of a complete survey observation. If nothing interrupts processing, we are able to reduce a single pointing survey observation on our five node cluster with 24 physical cores and 256 GB of memory each within 24 h keeping up with the speed of the surveys. The quality of the generated images is sufficient for scientific usage for 44% of the recorded data products with single images reaching dynamic ranges of several thousands. Future improvements will increase this percentage to over 80%. Our design allowed development of the pipeline in parallel to the commissioning of the Apertif system.
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| 3. |
- Naldi, L., et al.
(författare)
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Comparators, study duration, outcome measures and sponsorship in therapeutic trials of psoriasis: update of the EDEN Psoriasis Survey 2001-2006
- 2010
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Ingår i: British Journal of Dermatology. - : Oxford University Press (OUP). - 1365-2133 .- 0007-0963. ; 162:2, s. 384-389
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Tidskriftsartikel (refereegranskat)abstract
- Background Several new therapeutic options for psoriasis have been tested in clinical trials in recent years. Choice of comparator, study duration and outcome measures are critical for interpreting application of trial results to clinical practice. Objectives We examined whether these trial aspects have changed substantially in recent years in comparison with the past. Methods A systematic search and evaluation of all randomized controlled trials (RCTs) for psoriasis published from January 2001 up to December 2006 in 14 leading medical and dermatological journals, compared with those published from 1977 to 2000. Results There were 140 RCTs of psoriasis in the period 2001-2006 and 249 in the period 1977-2000. The proportion of placebo-controlled studies increased from 44.6% to 69.3%. The median study duration increased from 7 weeks to 12 weeks. The proportion of studies adopting the Psoriasis Area and Severity Index score as an outcome increased from 30.6% to 57.7%, while the number of studies incorporating a quality of life measure increased from only one (0.4%) to 12 studies (7.7%). The proportion of studies sponsored by pharmaceutical companies increased from 61.0% to 73.7%. Conclusions Despite the increased number of new options, the number of head-to-head comparative trials has decreased and most trials focus on short-term effects, probably reflecting the increased influence of industrial sponsorship on the research agenda.
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