A Neural Network Gravitational Arc Finder based on the Mediatrix filamentation Method

Automated arc detection methods are needed to scan the ongoing and next-generation wide-field imaging surveys, which are expected to contain thousands of strong lensing systems. Arc finders are also required for a quantitative comparison between predictions and observations of arc abundance. Several algorithms have been proposed to this end, but machine learning methods have remained as a relatively unexplored step in the arc finding process. In this work we introduce a new arc finder based on pattern recognition, which uses a set of morphological measurements derived from the Mediatrix Filamentation Method as entries to an Artificial Neural Network (ANN). We show a full example of the application of the arc finder, first training and validating the ANN on simulated arcs and then applying the code on four Hubble Space Telescope (HST) images of strong lensing systems. The simulated arcs use simple prescriptions for the lens and the source, while mimicking HST observational conditions. We also consider a sample of objects from HST images with no arcs in the training of the ANN classification. We use the training and validation process to determine a suitable set of ANN configurations, including the combination of inputs from the Mediatrix method, so as to maximize the completeness while keeping the false positives low. In the simulations the method was able to achieve a completeness of about 90% with respect to the arcs that are input to the ANN after a preselection. However, this completeness drops to $\sim$ 70% on the HST images. The false detections are of the order of 3% of the objects detected in these images. The combination of Mediatrix measurements with an ANN is a promising tool for the pattern recognition phase of arc finding. More realistic simulations and a larger set of real systems are needed for a better training and assessment of the efficiency of the method.Comment: Updated to match published versio

A hybrid finite element approach to modeling sound radiation from circular and rectangular ducts

This is the post-print version of the Article - Copyright @ 2012 Acoustical Society of AmericaA numerical model based on a hybrid finite element method is developed that seeks to join sound pressure fields in interior and exterior regions. The hybrid method is applied to the analysis of sound radiation from open pipes, or ducts, and uses mode matching to couple a finite element discretization of the region surrounding the open end of the duct to wave based modal expansions for adjoining interior and exterior regions. The hybrid method facilitates the analysis of ducts of arbitrary but uniform cross section as well the study of conical flanges and here a modal expansion based on spherical harmonics is applied. Predictions are benchmarked against analytic solutions for the limiting cases of flanged and unflanged circular ducts and excellent agreement between the two methods is observed. Predictions are also presented for flanged and unflanged rectangular ducts, and because the hybrid method retains the sparse banded and symmetric matrices of the traditional finite element method, it is shown that predictions can be obtained within an acceptable time frame even for a three dimensional problem.This study is supported by the U.K. Engineering and Physical Sciences Research Council (EPSRC)

The worse eye revisited: Evaluating the impact of asymmetric peripheral vision loss on everyday function

In instances of asymmetric peripheral vision loss (e.g., glaucoma), binocular performance on simple psychophysical tasks (e.g., static threshold perimetry) is well-predicted by the better seeing eye alone. This suggests that peripheral vision is largely ‘better-eye limited’. In the present study, we examine whether this also holds true for real-world tasks, or whether even a degraded fellow eye contributes important information for tasks of daily living. Twelve normally-sighted adults performed an everyday visually-guided action (finding a mobile phone) in a virtual-reality domestic environment, while levels of peripheral vision loss were independently manipulated in each eye (gaze-contingent blur). The results showed that even when vision in the better eye was held constant, participants were significantly slower to locate the target, and made significantly more head- and eye-movements, as peripheral vision loss in the worse eye increased. A purely unilateral peripheral impairment increased response times by up to 25%, although the effect of bilateral vision loss was much greater (>200%). These findings indicate that even a degraded visual field still contributes important information for performing everyday visually-guided actions. This may have clinical implications for how patients with visual field loss are managed or prioritized, and for our understanding of how binocular information in the periphery is integrated

Penning trap mass measurements on (99-109)$Cd with ISOLTRAP and implications on the rp process

Penning trap mass measurements on neutron-deficient Cd isotopes (99-109)Cd have been performed with the ISOLTRAP mass spectrometer at ISOLDE/CERN, all with relative mass uncertainties below 3*10^8. A new mass evaluation has been performed. The mass of 99Cd has been determined for the first time which extends the region of accurately known mass values towards the doubly magic nucleus 100Sn. The implication of the results on the reaction path of the rp process in stellar X-ray bursts is discussed. In particular, the uncertainty of the abundance and the overproduction created by the rp-process for the mass A = 99 is demonstrated by reducing the uncertainty of the proton-separation energy of 100In Sp(100In) by a factor of 2.5.Comment: 14 pages, 9 figure

A simple prescription for simulating and characterizing gravitational arcs

Simple models of gravitational arcs are crucial to simulate large samples of these objects with full control of the input parameters. These models also provide crude and automated estimates of the shape and structure of the arcs, which are necessary when trying to detect and characterize these objects on massive wide area imaging surveys. We here present and explore the ArcEllipse, a simple prescription to create objects with shape similar to gravitational arcs. We also present PaintArcs, which is a code that couples this geometrical form with a brightness distribution and adds the resulting object to images. Finally, we introduce ArcFitting, which is a tool that fits ArcEllipses to images of real gravitational arcs. We validate this fitting technique using simulated arcs and apply it to CFHTLS and HST images of tangential arcs around clusters of galaxies. Our simple ArcEllipse model for the arc, associated to a S\'ersic profile for the source, recovers the total signal in real images typically within 10%-30%. The ArcEllipse+S\'ersic models also automatically recover visual estimates of length-to-width ratios of real arcs. Residual maps between data and model images reveal the incidence of arc substructure. They may thus be used as a diagnostic for arcs formed by the merging of multiple images. The incidence of these substructures is the main factor preventing ArcEllipse models from accurately describing real lensed systems.Comment: 12 pages, 11 figures, accepted for publication in A&

Seeing other perspectives: Evaluating the use of virtual and augmented reality to simulate visual impairments (OpenVisSim)

Simulations of visual impairment are often used to educate and inform the public. However, evidence regarding their accuracy remains lacking. Here we evaluated the effectiveness of modern digital technologies to simulate the everyday difficulties caused by glaucoma. Twenty5 three normally-sighted adults performed two everyday tasks that glaucoma patients often report difficulties with: a visual search task in which they attempted to locate a mobile phone in virtual domestic environments (Virtual Reality; VR), and a visual mobility task in which impairments were overlaid onto a real-world environment using Augmented Reality (AR). On some trials, a gaze-contingent simulated scotoma --- generated using perimetric data from a patient with advanced glaucoma --- was presented in either the superior or inferior hemifield. The main outcome measure was task completion time. Eye and head movements were also tracked and used to assess individual differences in looking behaviors. The results showed that the simulated impairments substantial impaired performance in both the VR (visual search) and AR (visual mobility) tasks (both P < 0.001). Furthermore, and in line with previous patient data: impairments were greatest when the simulated VFL was inferior versus superior (P < 0.001), participants made more eye and head movements in the inferior VFL condition (P < 0.001), and participants rated the inferior VFL condition as more difficult (P < 0.001). Notably, the difference in performance between the inferior and superior conditions was almost as great as the difference between a superior VFL and no impairment at all (VR: 71%; AR: 70%). We conclude that modern digital simulators are able to replicate and objectively quantify some of the key everyday difficulties associated with visual impairments. Advantages, limitations and possible applications of current technologies are discussed. Instructions are also given for how to freely obtain the software described (OpenVisSim)

Prevalence and classification of rhinitis in the elderly: a nationwide survey in Portugal

BACKGROUND: Nationwide epidemiologic data on rhinitis in the elderly do not exist. This study aimed to estimate the prevalence of rhinitis in the population aged 65 years or above in mainland Portugal and to characterize and classify rhinitis in this age group. METHODS: Cross-sectional, nationwide, population-based survey of citizens aged 65 years or above, living in mainland Portugal. Current rhinitis (CR) was defined as the presence of at least two symptoms: 'repeated sneezing and itchy nose', 'blocked nose for more than one whole hour', or 'runny nose when not having a cold or flu', either usually or in the last 12 months. Rhinitis severity was assessed using a visual analogue scale; rhinitis was classified according to ARIA. RESULTS: Data were obtained from 3678 responders (92.5% response rate). The prevalence of CR was 29.8% (95% confidence interval (CI): 28.4%-31.3%): 49.1% had mild intermittent, 7.0% mild persistent, 27.5% moderate-severe intermittent, and 16.4% moderate-severe persistent rhinitis. Only 38.6% of patients with CR had been physician diagnosed and 38.7% were under treatment for this disease in the previous year. Allergic conjunctivitis symptoms were referred by 68.6% of subjects with CR (rhinoconjunctivitis population prevalence, 20.5% (95% CI: 19.2%-21.8%)). CONCLUSIONS: Rhinitis and rhinoconjunctivitis are common but underdiagnosed and undertreated diseases in the geriatric population. This was the first nationwide epidemiological survey classifying rhinitis according to ARIA guidelines in this age group. More than 40% of old-age patients presented moderate-severe disease

Temporal averaging for quantification of lumen dimensions in intravascular ultrasound images

Quantitative analysis of arterial dimensions from high frequency intravascular ultrasound images (30 MHz) may be hampered by strong blood scattering. Replacement of blood by saline is one method to provide a clear view of the arterial lumen; another method is that of temporal averaging of successive ultrasound images. The accuracy of this latter method was tested by comparing the lumen area measurements on the temporal-averaged image, with the data of the same cross-section obtained from the single-frame and saline-filled images. The mean lumen area measured on the temporal-averaged images was similar to that measured on the single-frame images (mean difference: −0.02 ± 1.16 mm2; p = ns). The mean lumen a

On application of Liouville type equations to constructing B\"acklund transformations

It is shown how pseudoconstants of the Liouville-type equations can be exploited as a tool for construction of the B\"acklund transformations. Several new examples of such transformations are found. In particular we obtained the B\"acklund transformations for a pair of three-component analogs of the dispersive water wave system, and auto-B\"acklund transformations for coupled three-component KdV-type systems.Comment: 11 pages, no figure