2,048 research outputs found
Reply to the comment by Carmelo Anile on the paper "Complexity analysis of the cerebrospinal fluid pulse waveform during infusion studies"
Veterinary technology is an emerging profession within the veterinary and allied animal health fields in Australia and affords graduates the opportunity to contribute to the small but growing body of literature within this discipline. This study describes the introduction of a contextualised assessment task to develop students’ research capability, competence and confidence in professional writing, and to engage them with the academic publishing process. Students worked in self-selected dyads to author a scientific case report, of publishable standard, based on authentic cases from their clinical practicum. Intrinsic to the task, students attended a series of workshops that explored topics such as critiquing the literature, professional writing styles and oral presentation skills. Assessment was multi-staged with progressive feedback, including peer review, and culminated with students presenting their abstracts at a mock conference. Students reported the task to be an enjoyable and valuable learning experience which improved their competence and confidence in scientific writing; supported by a comparison of previously submitted work. Linking scientific writing skills to clinical practice experiences enhanced learning outcomes and may foster the professionalisation of students within this emerging discipline
A Survey of the District of Columbia Law Revision Commission
This is part of the District of Columbia Surve
Don\u27t Tear it Down, Inc. v. Pennsylvania Avenue Development Corp.: A Statutory Interpretation Sanctions the Use of the Wrecking Ball
These notes are part of the District of Columbia Surve
Don\u27t Tear it Down, Inc. v. Pennsylvania Avenue Development Corp.: A Statutory Interpretation Sanctions the Use of the Wrecking Ball
These notes are part of the District of Columbia Surve
A Survey of the District of Columbia Law Revision Commission
This is part of the District of Columbia Surve
How materials inform metaphor in the works of Magdalena Abakanowicz
Art history research paper.1996 Spring.Includes bibliographic references (pages 16-18)
Collision velocity of dust grains in self-gravitating protoplanetary discs
We have conducted the first comprehensive numerical investigation of the relative velocity distribution of dust particles in self-gravitating protoplanetary discs with a view to assessing the viability of planetesimal formation via direct collapse in such environments. The viability depends crucially on the large sizes that are preferentially collected in pressure maxima produced by transient spiral features (Stokes numbers, St ∼ 1); growth to these size scales requires that collision velocities remain low enough that grain growth is not reversed by fragmentation. We show that, for a single-sized dust population, velocity driving by the disc's gravitational perturbations is only effective for St > 3, while coupling to the gas velocity dominates otherwise. We develop a criterion for understanding this result in terms of the stopping distance being of the order of the disc scaleheight. Nevertheless, the relative velocities induced by differential radial drift in multi-sized dust populations are too high to allow the growth of silicate dust particles beyond St ∼ 10− 2 or 10−1 (10 cm to m sizes at 30 au), such Stokes numbers being insufficient to allow concentration of solids in spiral features. However, for icy solids (which may survive collisions up to several 10 m s−1), growth to St ∼ 1 (10 m size) may be possible beyond 30 au from the star. Such objects would be concentrated in spiral features and could potentially produce larger icy planetesimals/comets by gravitational collapse. These planetesimals would acquire moderate eccentricities and remain unmodified over the remaining lifetime of the disc.This work has been supported by the DISCSIM project, grant agreement 341137 funded by the European Research Council under ERC-2013-ADG and has used the DIRAC Shared Memory Processing and DiRAC Data Analytic systems at the University of Cambridge. The DIRAC Shared Memory Processing system is operated by the COSMOS Project at the Department of Applied Mathematics and Theoretical Physics and was funded by BIS National E-infrastructure capital grant ST/J005673/1, STFC capital grant ST/H008586/1. The DiRAC Data Analytic system was funded by BIS National E-infrastructure capital grant ST/J005673/1 and STFC capital grant ST/H008586/1. Both systems are on behalf of the STFC DiRAC HPC Facility (www.dirac.ac.uk), funded by the STFC DiRAC Operations grant ST/K00333X/1.This is the final version of the article. It first appeared from Oxford University Press via http://dx.doi.org/10.1093/mnras/stw48
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Dust delivery and entrainment in photoevaporative winds
ABSTRACT
We model the gas and dust dynamics in a turbulent protoplanetary disc undergoing extreme-UV photoevaporation in order to better characterize the dust properties in thermal winds (e.g. size distribution, flux rate, trajectories). Our semi-analytic approach allows us to rapidly calculate these dust properties without resorting to expensive hydrodynamic simulations. We find that photoevaporation creates a vertical gas flow within the disc that assists turbulence in supplying dust to the ionization front. We examine both the delivery of dust to the ionization front and its subsequent entrainment in the overlying wind. We derive a simple analytic criterion for the maximum grain size that can be entrained and show that this is in good agreement with the results of previous simulations where photoevaporation is driven by a range of radiation types. We show that, in contrast to the case for magnetically driven winds, we do not expect large-scale dust transport within the disc to be effected by photoevaporation. We also show that the maximum size of grains that can be entrained in the wind (smax) is around an order of magnitude larger than the maximum size of grains that can be delivered to the front by advection alone ( for Herbig Ae/Be stars and for T Tauri stars). We further investigate how larger grains, up to a limiting size slimit, can be delivered to the front by turbulent diffusion alone. In all cases, we find smax ≳ slimit so that we expect that any dust that is delivered to the front can be entrained in the wind and that most entrained dust follows trajectories close to that of the gas.</jats:p
Motility is required for the competitive fitness of entomopathogenic Photorhabdus luminescens during insect infection
<p>Abstract</p> <p>Background</p> <p><it>Photorhabdus </it>are motile members of the family Enterobactericeae that are pathogenic to insect larvae whilst also maintaining a mutualistic interaction with entomophagous nematodes of the family Heterorhabditiae. The interactions between <it>Photorhabdus </it>and its hosts are thought to be an obligate part of the bacteria's life-cycle in the environment. Motility often plays a key role in mediating bacteria-host interactions and, in this study, we were interested in characterising the role of motility in the <it>Photorhabdus</it>-nematode-insect tripartite association.</p> <p>Results</p> <p>We constructed deletion mutants of <it>flgG </it>(blocking flagella production) and <it>motAB </it>(blocking flagella rotation) in <it>P. luminescens </it>TT01. Using these mutants we show that both the Δ<it>flgG </it>and Δ<it>motAB </it>mutants are equally as good as the wild-type (WT) bacteria in killing insects and supporting nematode growth and development suggesting that flagella production and motility are not required for pathogenicity or mutualism. However we show that the production of flagella is associated with a significant metabolic cost during growth on agar plates suggesting that, although not required for pathogenicity or mutualism, there must be a strong selective pressure to retain flagella production (and motility) during the interactions between <it>Photorhabdus </it>and its different hosts. To this end we show that both the Δ<it>flgG </it>and Δ<it>motAB </it>mutants are out-competed by WT <it>Photorhabdus </it>during prolonged incubation in the insect revealing that motile bacteria do have a fitness advantage during colonisation of the insect larva.</p> <p>Conclusion</p> <p>This is the first report of a role for motility in <it>Photorhabdus </it>and we show that, although not required for either pathogenicity or mutualism, motility does contribute to the competitive fitness of <it>Photorhabdus </it>during infection of the insect (and, to a lesser extent, the nematode). This adaptive function is similar to the role ascribed to motility in mammalian pathogens such as uropathogenic <it>Escherichia coli </it>(UPEC). Therefore, in addition to describing a role for motility in <it>Photorhabdus</it>, this study reinforces the relevance and utility of this bacterium as a model for studying bacteria-host interactions.</p
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