A triple-star system with a misaligned and warped circumstellar disk shaped by disk tearing

Young stars are surrounded by a circumstellar disk of gas and dust, within which planet formation can occur. Gravitational forces in multiple star systems can disrupt the disk. Theoretical models predict that if the disk is misaligned with the orbital plane of the stars, the disk should warp and break into precessing rings, a phenomenon known as disk tearing. We present observations of the triple-star system GW Orionis, finding evidence for disk tearing. Our images show an eccentric ring that is misaligned with the orbital planes and the outer disk. The ring casts shadows on a strongly warped intermediate region of the disk. If planets can form within the warped disk, disk tearing could provide a mechanism for forming wide-separation planets on oblique orbits.

Role of multifocal electroretinogram in assessment of early retinal dysfunction in hypertensive patients

Purpose: To investigate localized retinal dysfunction in hypertensive patients using multifocal electroretinogram (mfERG) and to assess its sensitivity as an early predictor for the development of retinopathy in hypertensive patients. Methods: Ninety-eight eyes were included in this case-control study. Twenty-eight eyes of healthy subjects served as a control group (group I). Seventy eyes belonged to patients with systemic hypertension assigned into two groups; group II including 39 eyes of hypertensive patients with normal fundus and group III including 31 eyes of patients with signs of hypertensive retinopathy. All participants were subjected to complete ophthalmic and electrophysiological examination using mfERG. N1 and P1 wave amplitudes and implicit times from the central hexagon and four concentric rings across the visual field were analyzed. Results: mfERG amplitudes were significantly reduced in hypertensive group with retinopathy than in controls. N1 amplitude was significantly reduced in the most eccentric ring in eyes of hypertensive patients with normal fundus. Conclusion: mfERG is a sensitive objective tool for assessment of retinal dysfunction in hypertensive patients. mfERG amplitude is a promising predictor for early development of retinopathy in systemic hypertension.

Effects of Rubber Size on the Cracking Resistance of Rubberized Mortars

This study investigated the cracking resistance of rubberized cement-based mortars. Three rubber particle sizes were used: Rubber A (major particle size 2–4 mm), Rubber B (major particle size 1–3 mm), and Rubber C (major particle size 0–2 mm). Traditional restrained ring shrinkage test (RRST), new restrained squared eccentric ring shrinkage test (RSERST), mechanical test, and scanning electron microscopy test were conducted. Results showed that the cracking inhibitory effect of Rubber B was the highest among the three rubber particle sizes. SEM results revealed that the particle size of the rubber does not have much effect on the ITZ (interfacial transition zone) position of rubber and cement paste. For the strength differences of the three types of rubberized mortar, it is mainly because the specific surface area increased as the rubber size decreased, which lead to more ITZ positions and pore structures. Our study verified that RSERST can predict the cracking position and shorten the test period. Compared with RRST, RSERST can also increase the restriction degree. K R is defined as the intensification factor of RSERST restriction degree. The average intensification factor is K R ¯ = 1.17 .

First resolved observations of a highly asymmetric debris disc around HD 160305 with VLT/SPHERE

Context. Direct imaging of debris discs gives important information about their nature, their global morphology, and allows us to identify specific structures possibly in connection with the presence of gravitational perturbers. It is the most straightforward technique to observe planetary systems as a whole. Aims. We present the first resolved images of the debris disc around the young F-type star HD 160305, detected in scattered light using the VLT/SPHERE instrument in the near infrared. Methods. We used a post-processing method based on angular differential imaging and synthetic images of debris discs produced with a disc modelling code (GRaTer) to constrain the main characteristics of the disc around HD 160305. All of the point sources in the field of the IRDIS camera were analysed with an astrometric tool to determine whether they are bound objects or background stars. Results. We detect a very inclined (~82°) ring-like debris disc located at a stellocentric distance of about 86 au (deprojected width ~27 au). The disc displays a brightness asymmetry between the two sides of the major axis, as can be expected from scattering properties of dust grains. We derive an anisotropic scattering factor g > 0.5. A second right-left asymmetry is also observed with respect to the minor axis. We measure a surface brightness ratio of 0.73 ± 0.18 between the bright and the faint sides. Because of the low signal-to-noise ratio (S/N) of the images we cannot easily discriminate between several possible explanations for this left-right asymmetry, such as perturbations by an unseen planet, the aftermath of the breakup of a massive planetesimal, or the pericenter glow effect due to an eccentric ring. Two epochs of observations allow us to reject the companionship hypothesis for the 15 point sources present in the field.