Growing dust grains in protoplanetary discs - III. vertical settling

TM acknowledges the support of a Swinburne Special Studies Programme. GL is grateful to the Australian Research Council for funding via Discovery project grant DP1094585, and acknowledges funding from the European Research Council for the FP7 ERC advanced grant project ECOGAL. JFG's research was conducted within the Lyon Institute of Origins under grant ANR-10-LABX-66.We aim to derive a simple analytic model to understand the essential properties of vertically settling growing dust grains in laminar protoplanetary discs. Separating the vertical dynamics from the motion in the disc mid-plane, we integrate the equations of motion for both a linear and an exponential grain growth rate. Numerical integrations are performed for more complex growth models. We find that the settling efficiency depends on the value of the dimensionless parameter γ , which characterizes the relative efficiency of grain growth with respect to the gas drag. Since γ is expected to be of the same order as the initial dust-to-gas ratio in the disc (≃10−2), grain growth enhances the energy dissipation of the dust particles and improves the settling efficiency in protoplanetary discs. This behaviour is mostly independent of the growth model considered as well as of the radial drift of the particles.Publisher PDFPeer reviewe

The accumulation and trapping of grains at planet gaps: effects of grain growth and fragmentation

We model the dust evolution in protoplanetary disks with full 3D, Smoothed Particle Hydrodynamics (SPH), two-phase (gas+dust) hydrodynamical simulations. The gas+dust dynamics, where aerodynamic drag leads to the vertical settling and radial migration of grains, is consistently treated. In a previous work, we characterized the spatial distribution of non-growing dust grains of different sizes in a disk containing a gap-opening planet and investigated the gap's detectability with the Atacama Large Millimeter/submillimeter Array (ALMA). Here we take into account the effects of grain growth and fragmentation and study their impact on the distribution of solids in the disk. We show that rapid grain growth in the two accumulation zones around planet gaps is strongly affected by fragmentation. We discuss the consequences for ALMA observations.Comment: Accepted for publication in Planetary and Space Science. 13 pages, 4 figure

Does sleep education change sleep parameters? Comparing sleep education trials for middle school students in Australia and New Zealand

Background: Adolescents suffer daytime consequences from sleep loss. Sleep education programs have been developed in an attempt to increase sleep knowledge and/or duration. This paper presents data from three trials of the Aus-tralian Centre for Education in Sleep (ACES) program for adolescents.Methods: The ACES program was delivered to 69 Australian adolescents in a pre-post cross-sectional design (mean age 15.2) and 29 New Zealand adolescents in a randomised control trial (mean age 14.8 years). Assessments in sleep parame-ters were undertaken at baseline and post intervention.Results: Where sleep knowledge was evaluated (Australian trials), significant improvements were shown in all trials (All p <0.05). Where sleep duration was assessed (New Zealand trial) significant improvements were found in week and weekend sleep duration [F(1, 27)=4.26, p=0.04). Both, students and teachers found the program feasible, interesting, and educational.Conclusions: ACES sleep education programmes can improve both sleep knowledge and sleep duration in adolescents. Improving the programme so sleep knowledge attained equates to actual sleep behaviour change are areas for future direc-tion. Collectively these findings provide encouraging signs that adolescents can improve their sleep knowledge and behav-iour with sleep education which bodes well for sleep-related health and psycho-social issues

Ovine recombinant PrP as an inhibitor of ruminant prion propagation in vitro

Prion diseases are fatal and incurable neurodegenerative diseases of humans and animals. Despite years of research, no therapeutic agents have been developed that can effectively manage or reverse disease progression. Recently it has been identified that recombinant prion proteins (rPrP) expressed in bacteria can act as inhibitors of prion replication within the in vitro prion replication system Protein Misfolding Cyclic Amplification (PMCA). Here, within PMCA reactions amplifying a range of ruminant prions including distinct Prnp genotypes/host species and distinct prion strains, recombinant ovine VRQ PrP displayed consistent inhibition of prion replication and produced IC50 values of 122 and 171 nM for ovine scrapie and bovine BSE replication, respectively. These findings illustrate the therapeutic potential of rPrPs with distinct TSE diseases

The accumulation and trapping of grains at planet gaps: effects of grain growth and fragmentation

13 pages, 4 figures.International audienceWe model the dust evolution in protoplanetary disks with full 3D, Smoothed Particle Hydrodynamics (SPH), two-phase (gas+dust) hydrodynamical simulations. The gas+dust dynamics, where aerodynamic drag leads to the vertical settling and radial migration of grains, is consistently treated. In a previous work, we characterized the spatial distribution of non-growing dust grains of different sizes in a disk containing a gap-opening planet and investigated the gap's detectability with the Atacama Large Millimeter/submillimeter Array (ALMA). Here we take into account the effects of grain growth and fragmentation and study their impact on the distribution of solids in the disk. We show that rapid grain growth in the two accumulation zones around planet gaps is strongly affected by fragmentation. We discuss the consequences for ALMA observations

STEP WIDTH, GLUTEUS MEDIUS ACTIVATION AND POSTURAL SWAY RESPONSES TO A NOVEL GAIT TREATMENT: A PILOT STUDY

The current study explored the acute effect of a novel rehabilitative device (NewGait™) on several interrelated variables associated with gait. Participants completed an eight-minute walking treatment wearing the NewGait™. Postural sway (center of pressure velocity), step width, and gluteus medius (GM) muscle activity were measured before during and after the treatment. No significant changes were noted in step width or GM activity during the treatment. Step width narrowed significantly after the treatment (p=0.02) and postural sway improved in the eyes open condition (p=0.02). These results indicate gait changes in healthy participant’s following use of the NewGait™ device. However, due to the acute nature of this investigation, it is unclear if balance improvements noted are due to the walking activity alone or walking while wearing the NewGait™ device

Does an early home-based progressive resistance training program improve function following total hip replacement? Results of a randomized controlled study

CONSORT 2010 checklist. (DOC 219 kb

In vitro amplification of H-type atypical bovine spongiform encephalopathy by protein misfolding cyclic amplification

The in vitro amplification of prions by serial protein misfolding cyclic amplification has been shown to detect PrPSc to levels at least as sensitive as rodent bioassay but in a fraction of the time. Bovine spongiform encephalopathy is a zoonotic prion disease in cattle and has been shown to occur in three distinct forms, classical BSE (C-BSE) and two atypical BSE forms (L-BSE and H-BSE). Atypical forms are usually detectedin asymptomatic, older cattle and are suggested to be spontaneous forms of the disease. Here, we show the development of a serial protein misfolding cyclic amplification method for the detection of H-BSE. The assay could detect PrPSc from 3 distinct experimental isolates of H-BSE, could detect PrPSc in as little as 1 x 10-12 g of brain material and was highly specific. Additionally, the product of serial protein misfolding cyclic amplification at all dilutions of seed analysed could be readily distinguished from L-BSE, which did not amplify, and C-BSE, which had PrPSc with distinct protease K-resistance and protease K-resistant PrPSc molecular weights