2,376 research outputs found
Evaluation of earlier versus later dietary management in long-chain 3-hydroxyacyl-CoA dehydrogenase or mitochondrial trifunctional protein deficiency::a systematic review
Test generation from P systems using model checking
This paper presents some testing approaches based on model checking and using different testing criteria. First, test sets are built from different Kripke structure representations. Second, various rule coverage criteria for transitional, non-deterministic, cell-like P systems, are considered in order to generate adequate test sets. Rule based coverage criteria (simple rule coverage, context-dependent rule coverage and variants) are defined and, for each criterion, a set of LTL (Linear Temporal Logic) formulas is provided. A codification of a P system as a Kripke structure and the sets of LTL properties are used in test generation: for each criterion, test cases are obtained from the counterexamples of the associated LTL formulas, which are automatically generated from the Kripke structure codification of the P system. The method is illustrated with an implementation using a specific model checker, NuSMV. (C) 2010 Elsevier Inc. All rights reserved
ELT HARMONI: Image Slicer Preliminary Design
Harmoni is the ELT's first light visible and near-infrared integral field
spectrograph. It will provide four different spatial scales, ranging from
coarse spaxels of 60 x 30 mas best suited for seeing limited observations, to 4
mas spaxels that Nyquist sample the diffraction limited point spread function
of the ELT at near-infrared wavelengths. Each spaxel scale may be combined with
eleven spectral settings, that provide a range of spectral resolving powers
from R 3500 to R 20000 and instantaneous wavelength coverage spanning the 0.47
- 2.45 {\mu}m wavelength range of the instrument. The consortium consists of
several institutes in Europe under leadership of Oxford University. Harmoni is
starting its Final Design Phase after a Preliminary Design Phase in November,
2017. The CRAL has the responsibility of the Integral Field Unit design linking
the Preoptics to the 4 Spectrographs. It is composed of a field splitter
associated with a relay system and an image slicer that create from a
rectangular Field of View a very long (540mm) output slit for each
spectrograph. In this paper, the preliminary design and performances of Harmoni
Image Slicer will be presented including image quality, pupil distortion and
slit geometry. It has been designed by CRAL for Harmoni PDR in November, 2017.
Special emphases will be put on straylight analysis and slice diffraction. The
optimisation of the manufacturing and slit geometry will also be reported.Comment: 13 pages, 19 figures, 4 tables, Submitted to SPIE Astronomical
Telescopes and Instrumentatio
Sensing and control of segmented mirrors with a pyramid wavefront sensor in the presence of spiders
The segmentation of the telescope pupil (by spiders & the segmented M4)
create areas of phase isolated by the width of the spiders on the wavefront
sensor (WFS), breaking the spatial continuity of the wavefront. The poor
sensitivity of the Pyramid WFS (PWFS) to differential piston leads to badly
seen and therefore uncontrollable differential pistons. In close loop
operation, differential pistons between segments will settle around integer
values of the average sensing wavelength. The differential pistons typically
range from one to ten times the sensing wavelength and vary rapidly over time,
leading to extremely poor performance. In addition, aberrations created by
atmospheric turbulence will contain large amounts of differential piston
between the segments. Removing piston contribution over each of the DM segments
leads to poor performance. In an attempt to reduce the impact of unwanted
differential pistons that are injected by the AO correction, we compare three
different approaches. We first limit ourselves to only use the information
measured by the PWFS, in particular by reducing the modulation. We show that
using this information sensibly is important but will not be sufficient. We
discuss possible ways of improvement by using prior information. A second
approach is based on phase closure of the DM commands and assumes the
continuity of the correction wavefront over the entire unsegmented pupil. The
last approach is based on the pair-wise slaving of edge actuators and shows the
best results. We compare the performance of these methods using realistic
end-to-end simulations. We find that pair-wise slaving leads to a small
increase of the total wavefront error, only adding between 20-45 nm RMS in
quadrature for seeing conditions between 0.45-0.85 arcsec. Finally, we discuss
the possibility of combining the different proposed solutions to increase
robustness.Comment: 12 pages, 15 figures, AO4ELT5 Proceedings, Adaptive Optics for
Extremely Large Telescopes 5, Conference Proceeding, Tenerife, Canary
Islands, Spain, June 25-30, 201
Hospital Episode Statistics and trends in ophthalmic surgery 1998 – 2004
BACKGROUND: Hospital episode statistics (HES) is a UK national database for the National Health Service (NHS), now available online. The purpose of this study was to observe trends in ophthalmic operations performed during the period from 1998 to 2004, using this data. METHODS: From the 'Main Operation' codes within the 'Free data' section of the HES website we analysed data in regard to 28 specific ophthalmic operations. These represented each sub speciality within ophthalmology. RESULTS: The figures show a change in the total number and proportions of operations performed for many of the procedures. For example, there was an increase in numbers of orbital decompressions, but a decrease in numbers of glaucoma filtering operations. Changing trends could be seen in different surgical areas such as the change in operations used for corneal grafting and in retinal surgery. CONCLUSION: The HES database represents an important, potentially useful source of information. There are imitations in interpretation of and validity of such data related to coding inconsistencies. We suggest the benefit of the data comes from observing trends rather than exact numbers. As other studies using this data have suggested, it is important that clinicians are involved in improving the quality of this data
Very high contrast IFU spectroscopy of AB Doradus C: 9 mag contrast at 0.2" without a coronagraph using spectral deconvolution
We present an extension of the spectral deconvolution method (Sparks & Ford
2002) to achieve very high contrast at small inner working radii. We apply the
method to the specific case of ground based adaptive optics fed integral field
spectroscopy (without a coronagraph). Utilising the wavelength dependence of
the Airy and speckle patterns, we make an accurate estimate of the PSF that can
be scaled and subtracted from the data cube. The residual noise in the
resulting spectra is very close to the photon noise from the starlight halo. We
utilise the technique to extract a very high SNR H & K band spectrum of AB Dor
C, the low mass companion to AB Dor A. By effectively eliminating all
contamination from AB Dor A, the extracted spectrum retains both continuum and
spectral features. The achieved 1 sigma contrast is 9 mag at 0.2", 11 mag at
0.5", in 20 mins exposure time, at an effective spectral bandwidth of 5.5 nm,
proving that the method is applicable even in low Strehl regimes.
The spectral deconvolution method clearly demonstrates the efficacy of image
slicer based IFUs in achieving very high contrast imaging spectroscopy at small
angular separations, validating their use as high contrast
spectrographs/imagers for extreme adaptive optics systems.Comment: 9 pages, 5 figures, accepted for publication in MNRAS. This is a
joint submission with astro-ph/0703564 by L. Close et a
Hyporheic invertebrates as bioindicators of ecological health in temporary rivers: a meta-analysis
Worldwide, many rivers cease flow and dry either naturally or owing to human activities such as water extraction. However, even when surface water is absent, diverse assemblages of aquatic invertebrates inhabit the saturated sediments below the river bed (hyporheic zone). In the absence of surface water or flow, biota of this zone may be sampled as an alternative to surface water-based ecological assessments. The potential of hyporheic invertebrates as ecological indicators of river health, however, is largely unexplored. We analysed hyporheic taxa lists from the international literature on temporary rivers to assess compositional similarity among broad-scale regions and sampling conditions, including the presence or absence of surface waters and flow, and the regional effect of hydrological phase (dry channel, non-flowing waters, surface flow) on richness. We hypothesised that if consistent patterns were found, then effects of human disturbances in temporary rivers may be assessable using hyporheic bioindicators. Assemblages differed geographically and by climate, but hydrological phase did not have a strong effect at the global scale. However, hyporheic assemblage composition within regions varied along a gradient of higher richness during wetter phases
Newborn Screening for Long-Chain 3-Hydroxyacyl-CoA Dehydrogenase and Mitochondrial Trifunctional Protein Deficiencies Using Acylcarnitines Measurement in Dried Blood Spots—A Systematic Review of Test Accuracy
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