4,916 research outputs found
Projection-based measurement and identification
A recently developed Projection-based Digital Image Correlation (P-DVC)
method is here extended to 4D (space and time) displacement field measurement
and mechanical identification based on a single radiograph per loading step
instead of volumes as in standard DVC methods. Two levels of data reductions
are exploited, namely, reduction of the data acquisition (and time) by a factor
of 1000 and reduction of the solution space by exploiting model reduction
techniques. The analysis of a complete tensile elastoplastic test composed of
127 loading steps performed in 6 minutes is presented. The 4D displacement
field as well as the elastoplastic constitutive law are identified. Keywords:
Image-based identification, Model reduction, Fast 4D identification, In-situ
tomography measurements. INTRODUCTION Identification and validation of
increasingly complex mechanical models is a major concern in experimental solid
mechanics. The recent developments of computed tomography coupled with in-situ
tests provide extremely rich and non-destructive analyses [1]. In the latter
cases, the sample was imaged inside a tomograph, either with interrupted
mechanical load or with a continuously evolving loading and on-the-fly
acquisitions (as ultra-fast X-ray synchrotron tomography, namely, 20 Hz full
scan acquisition for the study of crack propagation [2]). Visualization of fast
transformations, crack openings, or unsteady behavior become accessible.
Combined with full-field measurements, in-situ tests offer a quantitative basis
for identifying a broad range of mechanical behavior.Comment: SEM 2019, Jun 2019, Reno, United State
Factors associated with polypharmacy and excessive polypharmacy in older people with Intellectual Disability differ from the general population; a cross-sectional observational nationwide study
Objectives: (1) To evaluate the prevalence of polypharmacy (5–9 medicines) and excessive polypharmacy (10+ medicines) and (2) to determine associated demographic and clinical characteristics in an ageing population with intellectual disabilities (IDs).
Design: Observational cross-sectional study.
Setting: Wave One (2009/2010) of the Intellectual Disability Supplement to the Irish Longitudinal Study on Ageing (IDS-TILDA).
Participants: A nationally representative sample of 753 persons with ID, aged between 41 and 90 years. Participants/proxy reported medicines ( prescription and over the counter) taken on a regular basis; medication data was available for 736 participants (98%).
Main outcome measures/interventions: Participants were divided into those with no polypharmacy (0–4 medicines), polypharmacy (5–9 medicines) and excessive polypharmacy (10+ medicines). Medication use patterns were analysed according to demographic variables and reported chronic conditions. A multinomial logistic regression model identified factors associated with polypharmacy (5–9 medicines) and excessive polypharmacy (≥10 medicines).
Results: Overall, 90% of participants reported use of medicines. Polypharmacy was observed in 31.5% of participants and excessive polypharmacy in 20.1%. Living in a residential institution, and reporting a mental health or neurological condition were strongly associated with polypharmacy and excessive polypharmacy after adjusting for confounders, but age or gender had no significant effect.
Conclusions: Polypharmacy was commonplace for older adults with ID and may be partly explained by the high prevalence of multimorbidity reported. Review of appropriateness of medication use is essential, as polypharmacy places ageing people with ID at risk of adverse effects
Factors associated with polypharmacy and excessive polypharmacy in older people with Intellectual Disability differ from the general population; a cross-sectional observational nationwide study
Objectives: (1) To evaluate the prevalence of polypharmacy (5–9 medicines) and excessive polypharmacy (10+ medicines) and (2) to determine associated demographic and clinical characteristics in an ageing population with intellectual disabilities (IDs).
Design: Observational cross-sectional study.
Setting: Wave One (2009/2010) of the Intellectual Disability Supplement to the Irish Longitudinal Study on Ageing (IDS-TILDA).
Participants: A nationally representative sample of 753 persons with ID, aged between 41 and 90 years. Participants/proxy reported medicines ( prescription and over the counter) taken on a regular basis; medication data was available for 736 participants (98%).
Main outcome measures/interventions: Participants were divided into those with no polypharmacy (0–4 medicines), polypharmacy (5–9 medicines) and excessive polypharmacy (10+ medicines). Medication use patterns were analysed according to demographic variables and reported chronic conditions. A multinomial logistic regression model identified factors associated with polypharmacy (5–9 medicines) and excessive polypharmacy (≥10 medicines).
Results: Overall, 90% of participants reported use of medicines. Polypharmacy was observed in 31.5% of participants and excessive polypharmacy in 20.1%. Living in a residential institution, and reporting a mental health or neurological condition were strongly associated with polypharmacy and excessive polypharmacy after adjusting for confounders, but age or gender had no significant effect.
Conclusions: Polypharmacy was commonplace for older adults with ID and may be partly explained by the high prevalence of multimorbidity reported. Review of appropriateness of medication use is essential, as polypharmacy places ageing people with ID at risk of adverse effects
Biologically effective dose correlates with linear tumor volume changes after upfront single-fraction stereotactic radiosurgery for vestibular schwannomas.
Vestibular schwannomas (VSs) are benign, slow-growing tumors. Management options include observation, surgery, and radiation. In this retrospective trial, we aimed at evaluating whether biologically effective dose (BED) plays a role in tumor volume changes after single-fraction first intention stereotactic radiosurgery (SRS) for VS. We compiled a single-institution experience (n = 159, Lausanne University Hospital, Switzerland). The indication for SRS was decided after multidisciplinary discussion. Only cases with minimum 3 years follow-up were included. The Koos grading, a reliable method for tumor classification was used. Radiosurgery was performed using Gamma Knife (GK) and a uniform marginal prescription dose of 12 Gy. Mean BED was 66.3 Gy (standard deviation 3.8, range 54.1-73.9). The mean follow-up period was 5.1 years (standard deviation 1.7, range 3-9.2). The primary outcome was changes in 3D volumes after SRS as function of BED and of integral dose received by the VS. Random-effect linear regression model showed that tumor volume significantly and linearly decreased over time with higher BED (p < 0.0001). Changes in tumor volume were also significantly associated with age, sex, number of isocenters, gradient index, and Koos grade. However, the effect of BED on tumor volume change was moderated by time after SRS and Koos grade. Lower integral doses received by the VSs were inversely correlated with BED in relationship with tumor volume changes (p < 0.0001). Six (3.4%) patients needed further intervention. For patients having uniformly received the same marginal dose prescription, higher BED linearly and significantly correlated with tumor volume changes after SRS for VSs. BED could represent a potential new treatment paradigm for patients with benign tumors, such as VSs, for attaining a desired radiobiological effect. This could further increase the efficacy and decrease the toxicity of SRS not only in benign tumors but also in other SRS indications
Search for cool extrasolar giant planets combining coronagraphy, spectral and angular differential imaging
Spectral differential imaging (SDI) is part of the observing strategy of
current and on-going high-contrast imaging instruments on ground-based
telescopes. Although it improves the star light rejection, SDI attenuates the
signature of off-axis companions to the star, just like angular differential
imaging (ADI). However, the attenuation due to SDI has the peculiarity of being
dependent on the spectral properties of the companions. To date, no study has
investigated these effects. Our team is addressing this problem based on data
from a direct imaging survey of 16 stars combining the phase-mask coronagraph,
the SDI and the ADI modes of VLT/NaCo. The objective of the survey is to search
for cool (Teff<1000-1300 K) giant planets at separations of 5-10 AU orbiting
young, nearby stars (<200 Myr, <25 pc). The data analysis did not yield any
detections. As for the estimation of the sensitivity limits of SDI-processed
images, we show that it requires a different analysis than that used in
ADI-based surveys. Based on a method using the flux predictions of evolutionary
models and avoiding the estimation of contrast, we determine directly the mass
sensitivity limits of the survey for the ADI processing alone and with the
combination of SDI and ADI. We show that SDI does not systematically improve
the sensitivity due to the spectral properties and self-subtraction of point
sources.Comment: 5 pages, 2 figure
Detection of Sharp Symmetric Features in the Circumbinary Disk Around AK Sco
The Search for Planets Orbiting Two Stars (SPOTS) survey aims to study the
formation and distribution of planets in binary systems by detecting and
characterizing circumbinary planets and their formation environments through
direct imaging. With the SPHERE Extreme Adaptive Optics instrument, a good
contrast can be achieved even at small (<300 mas) separations from bright
stars, which enables studies of planets and disks in a separation range that
was previously inaccessible. Here, we report the discovery of resolved
scattered light emission from the circumbinary disk around the well-studied
young double star AK Sco, at projected separations in the ~13--40 AU range. The
sharp morphology of the imaged feature is surprising, given the smooth
appearance of the disk in its spectral energy distribution. We show that the
observed morphology can be represented either as a highly eccentric ring around
AK Sco, or as two separate spiral arms in the disk, wound in opposite
directions. The relative merits of these interpretations are discussed, as well
as whether these features may have been caused by one or several circumbinary
planets interacting with the disk.Comment: 10 pages, 3 figures, accepted for publication in ApJ Letters. Minor
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