431 research outputs found
Association between Anatomical Variations and maxillary canine impaction: A retrospective study in orthodontics
This study aims to evaluate whether or not there is a higher prevalence of skeletal abnormalities in subjects with maxillary canine impaction (MCI). This retrospective study was performed on 67 subjects with maxillary canine impaction (test group) and on 67 patients without dental displacement (control group). Sella turcica bridging (SB), ponticulus posticus (PP), atlas posterior arch deficiency (APAD) and the morphology of sella turcica and pterygopalatine fissure were evaluated on lateral cephalometric radiographs. Statistical analysis was performed using chi-square, Mann-Whitney test and multivariate logistic models; the level of significance was p < 0.05. Results showed that in the test and control groups 87% and 62.7% of patients had SB, respectively. PP was observed in 60% of patients in the test group and in 16.4% of patients in the control group. APAD was observed in 9% of test group and in 4.5% of the control group. Skeletal anomalies were significantly increased (p < 0.05) in subjects with MCI. A significant difference between the groups was observed in regards to the shape of the pterygopalatine fissure, found to be less wide and longer in the test group. SB, PP and APAD were higher in subjects with MCI; furthermore, an elongated pterygopalatine fissure was significantly associated with MCI
The near-infrared and ice-band variability of Haro 6-10
We have monitored the angularly resolved near infrared and 3.1 micron
ice-band flux of the components of the young binary Haro 6-10 on 23 occasions
during the years 1988 to 2000. Our observations reveal that both the visible
star Haro 6-10 (Haro 6-10S) and its infrared companion (Haro 6-10N) show
significant variation in flux on time scales as short as a month. The
substantial flux decrease of Haro 6-10S over the last four years carries the
reddening signature of increased extinction. However, a comparable K-band flux
increase observed in the IRC is associated with a dimming in the H-band and
cannot be explained by lower extinction. Absorption in the 3.1 micron water-ice
feature was always greater towards the IRC during our observations, indicating
a larger amount of obscuring material along its line of sight. We detect
variability in the ice-band absorption towards Haro 6-10S and Haro 6-10N,
significant at the 3.5 sigma and 2.0 sigma levels, respectively.Comment: 8 pages, 6 Figures, Accepted for Publication in Astronomy &
Astrophysic
Fringe Tracker for the VLTI Spectro-Imager
The implementation of the simultaneous combination of several telescopes
(from four to eight) available at Very Large Telescope Interferometer (VLTI)
will allow the new generation interferometric instrumentation to achieve
interferometric image synthesis with unprecedented resolution and efficiency.
The VLTI Spectro Imager (VSI) is the proposed second-generation near-infrared
multi-beam instrument for the Very Large Telescope Interferometer, featuring
three band operations (J, H and K), high angular resolutions (down to 1.1
milliarcsecond) and high spectral resolutions. VSI will be equipped with its
own internal Fringe Tracker (FT), which will measure and compensate the
atmospheric perturbations to the relative beam phase, and in turn will provide
stable and prolonged observing conditions down to the magnitude K=13 for the
scientific combiner. In its baseline configuration, VSI FT is designed to
implement, from the very start, the minimum redundancy combination in a nearest
neighbor scheme of six telescopes over six baselines, thus offering better
options for rejection of large intensity or phase fluctuations over each beam,
due to the symmetric set-up. The planar geometry solution of the FT beam
combiner is devised to be easily scalable either to four or eight telescopes,
in accordance to the three phase development considered for VSI. The proposed
design, based on minimum redundancy combination and bulk optics solution, is
described in terms of opto-mechanical concept, performance and key operational
aspects.Comment: 11 pages, to be published in Proc. SPIE conference 7013 "Optical and
Infrared Interferometry", Schoeller, Danchi, and Delplancke, F. (eds.
Naturalization of current social representations of children and adolescents
Convergen en esta investigación el interés de docentes de la facultad en proporcionar, instrumentos a partir del conocimiento científico, a los espacios de intervención sobre violencia en la infancia y adolescencia. Ello se conjuga con la preocupación de profesionales que se desempeñan laboralmente en relación a esta problemática, quienes observan la inexistencia de transformaciones paradigmáticas y conceptuales en los escenarios donde se producen las situaciones planteadas. Por lo anteriormente descrito se hace imperioso, analizar científicamente el tema, para proporcionar nuevos conocimientos; a fin de dar posibles respuestas A la sociedad e instituciones
VSI: the VLTI spectro-imager
The VLTI Spectro Imager (VSI) was proposed as a second-generation instrument
of the Very Large Telescope Interferometer providing the ESO community with
spectrally-resolved, near-infrared images at angular resolutions down to 1.1
milliarcsecond and spectral resolutions up to R=12000. Targets as faint as K=13
will be imaged without requiring a brighter nearby reference object. The unique
combination of high-dynamic-range imaging at high angular resolution and high
spectral resolution enables a scientific program which serves a broad user
community and at the same time provides the opportunity for breakthroughs in
many areas of astrophysic including: probing the initial conditions for planet
formation in the AU-scale environments of young stars; imaging convective cells
and other phenomena on the surfaces of stars; mapping the chemical and physical
environments of evolved stars, stellar remnants, and stellar winds; and
disentangling the central regions of active galactic nuclei and supermassive
black holes. VSI will provide these new capabilities using technologies which
have been extensively tested in the past and VSI requires little in terms of
new infrastructure on the VLTI. At the same time, VSI will be able to make
maximum use of new infrastructure as it becomes available; for example, by
combining 4, 6 and eventually 8 telescopes, enabling rapid imaging through the
measurement of up to 28 visibilities in every wavelength channel within a few
minutes. The current studies are focused on a 4-telescope version with an
upgrade to a 6-telescope one. The instrument contains its own fringe tracker
and tip-tilt control in order to reduce the constraints on the VLTI
infrastructure and maximize the scientific return.Comment: 12 pages, to be published in Proc. SPIE conference 7013 "Optical and
Infrared Interferometry", Schoeller, Danchi, and Delplancke, F. (eds.). See
also http://vsi.obs.ujf-grenoble.f
Milli-arcsecond astrophysics with VSI, the VLTI spectro-imager in the ELT era
Nowadays, compact sources like surfaces of nearby stars, circumstellar
environments of stars from early stages to the most evolved ones and
surroundings of active galactic nuclei can be investigated at milli-arcsecond
scales only with the VLT in its interferometric mode. We propose a
spectro-imager, named VSI (VLTI spectro-imager), which is capable to probe
these sources both over spatial and spectral scales in the near-infrared
domain. This instrument will provide information complementary to what is
obtained at the same time with ALMA at different wavelengths and the extreme
large telescopes.Comment: 8 pages. To be published in the proceedings of the ESO workshop
"Science with the VLT in the ELT Era", held in Garching (Germany) on 8-12
October 2007, A. Moorwood edito
Euclid Collaboration IV: Impact of Undetected Galaxies on Weak-Lensing Shear Measurements
In modern weak-lensing surveys, the common approach to correct for residual
systematic biases in the shear is to calibrate shape measurement algorithms
using simulations. These simulations must fully capture the complexity of the
observations to avoid introducing any additional bias. In this paper we study
the importance of faint galaxies below the observational detection limit of a
survey. We simulate simplified Euclid VIS images including and excluding this
faint population, and measure the shift in the multiplicative shear bias
between the two sets of simulations. We measure the shear with three different
algorithms: a moment-based approach, model fitting, and machine learning. We
find that for all methods, a spatially uniform random distribution of faint
galaxies introduces a shear multiplicative bias of the order of a few times
. This value increases to the order of when including the
clustering of the faint galaxies, as measured in the Hubble Space Telescope
Ultra-Deep Field. The magnification of the faint background galaxies due to the
brighter galaxies along the line of sight is found to have a negligible impact
on the multiplicative bias. We conclude that the undetected galaxies must be
included in the calibration simulations with proper clustering properties down
to magnitude 28 in order to reach a residual uncertainty on the multiplicative
shear bias calibration of a few times , in line with the
total accuracy budget required by the scientific objectives of
the Euclid survey. We propose two complementary methods for including faint
galaxy clustering in the calibration simulations.Comment: Version published in A&
Long term health related quality of life following colorectal cancer surgery: patient reported outcomes in a remote follow-up population
Background: Remote follow-up (RFU) after colorectal cancer (CRC) surgery allows delivery of surveillance tests without the need for regular outpatient clinical appointments. However, little is known about health related quality of life (HRQoL) in RFU patients.Methods: EQ-5D, QLQ-C30 and QLQ-C29 questionnaires were distributed to CRC patients enrolled in a RFU programme. The primary outcome of HRQoL scores was analysed by year of RFU, demographics, operation-type, stoma and adherence to RFU protocols. Results:428 respondents (59.3%), mean age of 71years(SD 10.1) and a median RFU time of 2.6years (IQR: 1.6-4.8 years) were included. 26.6% of patients reported ‘perfect health’. The median EQ-5D index score was 0.785 (IQR: 0.671-1) and QLQ-C30 Global HRQoL score was 75 (IQR: 58.3-83.3). Females had significantly lower EQ-5D median score of 0.767 (IQR: 0.666-0.879, p=0.0088). Lower QLQ-C30 HRQoL scores were seen in stoma patients, median 66.6 (IQR: 58.3-83.3, p=0.0029). Erectile dysfunction (p=0.0006) and poor body image (p=0.001) were also reported more frequently in stoma patients. Patients undergoing right-sided resection reported a lower median EQ-5D score of 0.765 (IQR: 0.666-0.879, p=0.028) and higher pain severity (p=0.0367) compared with left-sided resections. There were 128 (29.4%) patients that breached RFU protocol and were seen in adhoc colorectal clinics. However, there was no statistical difference in HRQoL between patients who adhered to or breached RFU protocols.Conclusions: Overall HRQoL in patients in RFU is good, with no difference in those strictly followed up remotely. However, females, right-sided resections and patients with stomas may require additional clinical reviews.
System overview of the VLTI Spectro-Imager
The VLTI Spectro Imager project aims to perform imaging with a temporal
resolution of 1 night and with a maximum angular resolution of 1
milliarcsecond, making best use of the Very Large Telescope Interferometer
capabilities. To fulfill the scientific goals (see Garcia et. al.), the system
requirements are: a) combining 4 to 6 beams; b) working in spectral bands J, H
and K; c) spectral resolution from R= 100 to 12000; and d) internal fringe
tracking on-axis, or off-axis when associated to the PRIMA dual-beam facility.
The concept of VSI consists on 6 sub-systems: a common path distributing the
light between the fringe tracker and the scientific instrument, the fringe
tracker ensuring the co-phasing of the array, the scientific instrument
delivering the interferometric observables and a calibration tool providing
sources for internal alignment and interferometric calibrations. The two
remaining sub-systems are the control system and the observation support
software dedicated to the reduction of the interferometric data. This paper
presents the global concept of VSI science path including the common path, the
scientific instrument and the calibration tool. The scientific combination
using a set of integrated optics multi-way beam combiners to provide
high-stability visibility and closure phase measurements are also described.
Finally we will address the performance budget of the global VSI instrument.
The fringe tracker and scientific spectrograph will be shortly described
Euclid: On the reduced shear approximation and magnification bias for Stage IV cosmic shear experiments
Stage IV weak lensing experiments will offer more than an order of magnitude leap in precision. We must therefore ensure that our analyses remain accurate in this new era. Accordingly, previously ignored systematic effects must be addressed. In this work, we evaluate the impact of the reduced shear approximation and magnification bias, on the information obtained from the angular power spectrum. To first-order, the statistics of reduced shear, a combination of shear and convergence, are taken to be equal to those of shear. However, this approximation can induce a bias in the cosmological parameters that can no longer be neglected. A separate bias arises from the statistics of shear being altered by the preferential selection of galaxies and the dilution of their surface densities, in high-magnification regions. The corrections for these systematic effects take similar forms, allowing them to be treated together. We calculate the impact of neglecting these effects on the cosmological parameters that would be determined from Euclid, using cosmic shear tomography. We also demonstrate how the reduced shear correction can be calculated using a lognormal field forward modelling approach. These effects cause significant biases in Omega_m, n_s, sigma_8, Omega_DE, w_0, and w_a of -0.51 sigma, -0.36 sigma, 0.37 sigma, 1.36 sigma, -0.66 sigma, and 1.21 sigma, respectively. We then show that these lensing biases interact with another systematic: the intrinsic alignment of galaxies. Accordingly, we develop the formalism for an intrinsic alignment-enhanced lensing bias correction. Applying this to Euclid, we find that the additional terms introduced by this correction are sub-dominant
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