Debris Disks in the Scorpius-Centaurus OB Association Resolved by ALMA

We present a CO(2-1) and 1240 um continuum survey of 23 debris disks with spectral types B9-G1, observed at an angular resolution of 0.5-1 arcsec with the Atacama Large Millimeter/Submillimeter Array (ALMA). The sample was selected for large infrared excess and age ~10 Myr, to characterize the prevalence of molecular gas emission in young debris disks. We identify three CO-rich debris disks, plus two additional tentative (3-sigma) CO detections. Twenty disks were detected in the continuum at the >3-sigma level. For the 12 disks in the sample that are spatially resolved by our observations, we perform an independent analysis of the interferometric continuum visibilities to constrain the basic dust disk geometry, as well as a simultaneous analysis of the visibilities and broad-band spectral energy distribution to constrain the characteristic grain size and disk mass. The gas-rich debris disks exhibit preferentially larger outer radii in their dust disks, and a higher prevalence of characteristic grain sizes smaller than the blowout size. The gas-rich disks do not exhibit preferentially larger dust masses, contrary to expectations for a scenario in which a higher cometary destruction rate would be expected to result in a larger mass of both CO and dust. The three debris disks in our sample with strong CO detections are all around A stars: the conditions in disks around intermediate-mass stars appear to be the most conducive to the survival or formation of CO.Comment: 16 pages, 6 figures, accepted for publication in Ap

Health Management: Occupational Therapy’s Key Role in Educating Clients About Reliable Online Health Information

Background: Only 12% of Americans possess proficient health literacy skills. Among those with the lowest health literacy are individuals with chronic health conditions. Occupational therapists are well prepared to assist these clients with health literacy, given our roles in teaching new health management skills and health promotion. Methods: An educational course was designed and taught to over 100 individuals and caregivers with chronic health conditions to assist in finding and determining trustworthy health information online. An author designed pre postsurvey was used to evaluate effectiveness. Results: There was a significant pre-post change in four categories: finding quality health information online (M = 0.703), judging trustworthiness of online health information (M = 0.624), understanding health information (M = 0.489), and retrieving information using email alerts (M = 0.826). Conclusion: The ability to find and evaluate health information online empowers clients to fully participate in medical care. Evidence shows that this skill can be efficiently taught to clients or client groups for improved health management. Providing training in finding trustworthy health information online is a skill that occupational therapists can successfully teach in conjunction with overall health management skills for improved occupational participation

Nonlinear sub-cyclotron resonance as a formation mechanism for gaps in banded chorus

An interesting characteristic of magnetospheric chorus is the presence of a frequency gap at $\omega \simeq 0.5\Omega_e$, where $\Omega_e$ is the electron cyclotron angular frequency. Recent chorus observations sometimes show additional gaps near $0.3\Omega_e$ and $0.6\Omega_e$. Here we present a novel nonlinear mechanism for the formation of these gaps using Hamiltonian theory and test-particle simulations in a homogeneous, magnetized, collisionless plasma. We find that an oblique whistler wave with frequency at a fraction of the electron cyclotron frequency can resonate with electrons, leading to effective energy exchange between the wave and particles

Resolved Millimeter-wavelength Observations of Debris Disks around Solar-type Stars

The presence of debris disks around young main-sequence stars hints at the existence and structure of planetary systems. Millimeter-wavelength observations probe large grains that trace the location of planetesimal belts. The Formation and Evolution of Planetary Systems Spitzer Legacy survey of nearby young solar analogues yielded a sample of five debris disk-hosting stars with millimeter flux suitable for interferometric follow-up. We present observations with the Submillimeter Array (SMA) and the Combined Array for Research in Millimeter-wave Astronomy at ~2'' resolution that spatially resolve the debris disks around these nearby (d ~ 50 pc) stars. Two of the five disks (HD 377, HD 8907) are spatially resolved for the first time and one (HD 104860) is resolved at millimeter wavelengths for the first time. We combine our new observations with archival SMA and Atacama Large Millimeter/Submillimeter Array data to enable a uniform analysis of the full five-object sample. We simultaneously model the broadband photometric data and resolved millimeter visibilities to constrain the dust temperatures and disk morphologies, and perform a Markov Chain Monte Carlo analysis to fit for basic structural parameters. We find that the radii and widths of the cold outer belts exhibit properties consistent with scaled-up versions of the Solar System's Kuiper Belt. All the disks exhibit characteristic grain sizes comparable to the blowout size, and all the resolved observations of emission from large dust grains are consistent with an axisymmetric dust distribution to within the uncertainties. These results are consistent with comparable studies carried out at infrared wavelengths

The Disk Substructures at High Angular Resolution Project (DSHARP). III. Spiral Structures in the Millimeter Continuum of the Elias 27, IM Lup, and WaOph 6 Disks

We present an analysis of Atacama Large Millimeter/submillimeter Array 1.25 mm continuum observations of spiral structures in three protoplanetary disks from the Disk Substructures at High Angular Resolution Project. See full text for full abstract

The Disk Substructures at High Angular Resolution Project (DSHARP). II. Characteristics of Annular Substructures

The Disk Substructures at High Angular Resolution Project (DSHARP) used ALMA to map the 1.25 mm continuum of protoplanetary disks at a spatial resolution of ~5 au. We present a systematic analysis of annular substructures in the 18 single-disk systems targeted in this survey. No dominant architecture emerges from this sample; instead, remarkably diverse morphologies are observed. Annular substructures can occur at virtually any radius where millimeter continuum emission is detected and range in widths from a few astronomical units to tens of astronomical units. Intensity ratios between gaps and adjacent rings range from near-unity to just a few percent. In a minority of cases, annular substructures coexist with other types of substructures, including spiral arms (3/18) and crescent-like azimuthal asymmetries (2/18). No clear trend is observed between the positions of the substructures and stellar host properties. In particular, the absence of an obvious association with stellar host luminosity (and hence the disk thermal structure) suggests that substructures do not occur preferentially near major molecular snowlines. Annular substructures like those observed in DSHARP have long been hypothesized to be due to planet–disk interactions. A few disks exhibit characteristics particularly suggestive of this scenario, including substructures in possible mean-motion resonance and double gap features reminiscent of hydrodynamical simulations of multiple gaps opened by a planet in a low-viscosity disk

Identifying the source region of plasmaspheric hiss

The presence of the plasmaspheric hiss emission around the Earth has been known for more than 50 years but its origin has remained unknown in terms of source location and mechanism. The hiss, made of whistler mode waves, exists for most of the time in the plasmasphere and is believed to control the radiation belt surrounding the Earth which makes its understanding very important. This paper presents direct observational evidence that the plasmaspheric hiss originates in the equatorial region of the plasmaspheric drainage plumes. It shows that the emissions propagate along the magnetic field lines and away from the equator in the plumes but towards the equator at lower L shells inside the plasmasphere. The observations also suggest that the hiss waves inside the plasmasphere are absorbed as they cross the equator

Inner edges of planetesimal belts: collisionally eroded or truncated?

The radial structure of debris discs can encode important information about their dynamical and collisional history. In this paper we present a 3-phase analytical model to analyse the collisional evolution of solids in debris discs, focusing on their joint radial and temporal dependence. Consistent with previous models, we find that as the largest planetesimals reach collisional equilibrium in the inner regions, the surface density of dust and solids becomes proportional to $\sim r^{2}$ within a certain critical radius. We present simple equations to estimate the critical radius and surface density of dust as a function of the maximum planetesimal size and initial surface density in solids (and vice versa). We apply this model to ALMA observations of 7 wide debris discs. We use both parametric and non-parametric modelling to test if their inner edges are shallow and consistent with collisional evolution. We find that 4 out of 7 have inner edges consistent with collisional evolution. Three of these would require small maximum planetesimal sizes below 10 km, with HR 8799's disc potentially lacking solids larger than a few centimeters. The remaining systems have inner edges that are much sharper, which requires maximum planetesimal sizes $\gtrsim10$ km. Their sharp inner edges suggest they could have been truncated by planets, which JWST could detect. In the context of our model, we find that the 7 discs require surface densities below a Minimum Mass Solar Nebula, avoiding the so-called disc mass problem. Finally, during the modelling of HD 107146 we discover that its wide gap is split into two narrower ones, which could be due to two low-mass planets formed within the disc.Comment: Accepted for publication in MNRAS, 21 pages, 11 figure

Access to routinely collected health data for clinical trials - review of successful data requests to UK registries.

BACKGROUND: Clinical trials generally each collect their own data despite routinely collected health data (RCHD) increasing in quality and breadth. Our aim is to quantify UK-based randomised controlled trials (RCTs) accessing RCHD for participant data, characterise how these data are used and thereby recommend how more trials could use RCHD. METHODS: We conducted a systematic review of RCTs accessing RCHD from at least one registry in the UK between 2013 and 2018 for the purposes of informing or supplementing participant data. A list of all registries holding RCHD in the UK was compiled. In cases where registries published release registers, these were searched for RCTs accessing RCHD. Where no release register was available, registries were contacted to request a list of RCTs. For each identified RCT, information was collected from all publicly available sources (release registers, websites, protocol etc.). The search and data extraction were undertaken between January and May 2019. RESULTS: We identified 160 RCTs accessing RCHD between 2013 and 2018 from a total of 22 registries; this corresponds to only a very small proportion of all UK RCTs (about 3%). RCTs accessing RCHD were generally large (median sample size 1590), commonly evaluating treatments for cancer or cardiovascular disease. Most of the included RCTs accessed RCHD from NHS Digital (68%), and the most frequently accessed datasets were mortality (76%) and hospital visits (55%). RCHD was used to inform the primary trial (82%) and long-term follow-up (57%). There was substantial variation in how RCTs used RCHD to inform participant outcome measures. A limitation was the lack of information and transparency from registries and RCTs with respect to which datasets have been accessed and for what purposes. CONCLUSIONS: In the last five years, only a small minority of UK-based RCTs have accessed RCHD to inform participant data. We ask for improved accessibility, confirmed data quality and joined-up thinking between the registries and the regulatory authorities. TRIAL REGISTRATION: PROSPERO CRD42019123088