An integrated response of Trichodesmium erythraeum IMS101 growth and photo-physiology to Iron, CO₂, and light intensity

We have assessed how varying CO 2 (180, 380, and 720 μatm) and growth light intensity (40 and 400 μmol photons m -2 s -1 ) affected Trichodesmium erythraeum IMS101 growth and photophysiology over free iron (Fe') concentrations between 20 and 9,600 pM. We found significant iron dependencies of growth rate and the initial slope and maximal relative PSII electron transport rates (rP m ). Under iron-limiting concentrations, high-light increased growth rates and rPm; possibly indicating a lower allocation of resources to iron-containing photosynthetic proteins. Higher CO 2 increased growth rates across all iron concentrations, enabled growth to occur at lower Fe' concentrations, increased rPm and lowered the iron half saturation constants for growth (K m ). We attribute these CO 2 responses to the operation of the CCM and the ATP spent/saved for CO 2 uptake and transport at low and high CO 2 , respectively. It seems reasonable to conclude that T. erythraeum IMS101 can exhibit a high degree of phenotypic plasticity in response to CO 2 , light intensity and iron-limitation. These results are important given predictions of increased dissolved CO 2 and water column stratification (i.e., higher light exposures) over the coming decades

Arcsecond-resolution 12CO mapping of the yellow hypergiants IRC +10420 and AFGL 2343

IRC +10420 and AFGL 2343 are the unique, known yellow hypergiants (YHGs) presenting a heavy circumstellar envelope (CSE). We aim to study the morphology, exceptional kinematics, and excitation conditions of their CSEs, and the implications for mass-loss processes. We have mapped the 12CO J=2-1 and 1-0 emission in these YHGs with the IRAM Plateau de Bure interferometer and the 30m telescope. We developed LVG models in order to analyze their circumstellar characteristics. The maps show that the overall shape of both CSEs is approximately spherical, although they also reveal several aspherical features. The CSE around IRC +10420 shows a rounded extended halo surrounding a bright inner region, with both components presenting aspherical characteristics. It presents a brightness minimum at the center. The envelope around AFGL 2343 is a detached shell, showing spherical symmetry and clumpiness at a level of about 15% of the maximum brightness. The envelopes expand isotropically at about 35 km/s, about two or three times faster than typical CSEs around AGB stars. High temperatures (~ 200 K) are derived for the innermost regions in IRC +10420, while denser and cooler (~ 30 K) gas is found in AFGL 2343. The mass-loss processes in these YHGs have been found to be similar. The deduced mass-loss rates (~ 10E-4 - 10E-3 Msun/yr) are much higher than those obtained in AGB stars, and they present significant variations on time scales of ~ 1000 yr

Epidemiology and incidence of injury in elite netball players: An audit of the 2016 Netball Superleague season

Background: With England netball announcing that for the first time in its history it will be offering full time, professional contracts there is an increased need to be able to understand why players are getting injured in top level competition. Objective: To undertake a prospective epidemiological study of injuries sustained in elite netball Design: A cohort design was used to collect descriptive injury data using superleague netball players Setting: 2016 British Netball Superleague season Patients (or Participants): 103 players across 8 superleague netball teams were used in the study Main Outcome Measurements: Date of injury, age of player, playing position, activity at time of injury, mechanism of injury, classification of injury at two levels (body location and injury type), predicted time loss and identification of injury being acute, gradual on set or recurrent was recorded. Injuries were recorded by physiotherapists at each netball franchise using a specific injury audit questionnaire designed to suit the characteristics of netball Results: 59 injuries we recorded during one season with an injury incidence rate of 9.08 injuries per 1000 hours exposure. Injuries were more common in competitive match play (71.2%) than in training (28.8%). The ankle was injured most frequently (35.6%). Data revealed a significant association between match quarter and occurrence of injuries χ2 (3) = 9.91, p = 0.019. A tendency for injuries to increase throughout the time in match and a peak reached at the third quarter was observed. No significant association was observed between playing position and injury incidence χ2 (2) = 0.917, p = 0.632. Overall injury frequency was highest in the first half of the regular 14 week season with 57.6% of all injuries occurring in this time frame Conclusions: Pre-season preparation, half time match strategies and overall physiological conditioning should be considered when addressing injury prevention within elite netball

The Signature of Primordial Grain Growth in the Polarized Light of the AU Mic Debris Disk

We have used the Hubble Space Telescope/ACS coronagraph to make polarization maps of the AU Mic debris disk. The fractional linear polarization rises monotonically from about 0.05 to 0.4 between 20 and 80 AU. The polarization is perpendicular to the disk, indicating that the scattered light originates from micron sized grains in an optically thin disk. Disk models, which simultaneously fit the surface brightness and polarization, show that the inner disk (< 40-50 AU) is depleted of micron-sized dust by a factor of more than 300, which means that the disk is collision dominated. The grains have high maximum linear polarization and strong forward scattering. Spherical grains composed of conventional materials cannot reproduce these optical properties. A Mie/Maxwell-Garnett analysis implicates highly porous (91-94%) particles. In the inner Solar System, porous particles form in cometary dust, where the sublimation of ices leaves a "bird's nest" of refractory organic and silicate material. In AU Mic, the grain porosity may be primordial, because the dust "birth ring" lies beyond the ice sublimation point. The observed porosities span the range of values implied by laboratory studies of particle coagulation by ballistic cluster-cluster aggregation. To avoid compactification, the upper size limit for the parent bodies is in the decimeter range, in agreement with theoretical predictions based on collisional lifetime arguments. Consequently, AU Mic may exhibit the signature of the primordial agglomeration process whereby interstellar grains first assembled to form macroscopic objects.Comment: 12 pages, 8 figures, ApJ, in pres

The steady state load of five firefighting tasks

Purpose. Physiologic demands of five common tasks in firefighting have been examined. Methods. Eight male volunteers, being dressed up as smoke divers (+21 kg extra load), carried out the following tasks at constant pace for 5 min: Walking at 1.4 m·s–1, walking (all walks at the same speed) while carrying a 10 kg ladder, walking carrying two hose packs of 16 kg together, walking carrying a 32 kg spreader tool, finally climbing up and down a ladder at preset pace. A 5 min break separated each exercise. Heart rate, O2-uptake and ventilation were measured continuously, and blood lactate con-centration was recorded after each task. Results. The end-exercise heart rate rose from 108 to 180 bpm from first to last task, blood lactate concentration rose from 1 to 7 mmol·L–1, O2-uptake rose from 19 to 48 ml·kg–1·min–1, and ventilation rose from 38 to 124 L·min–1. Discussion. Walking was an easy task even when dressed up as a smoke diver. Adding loads increased demands; ladder climbing taxed >90% of the subjects’ aerobic power. Conclusions. The physiologic demands varied considera-bly between different tasks.acceptedVersio

ALMA Observations of the Water Fountain Pre-Planetary Nebula IRAS 16342-3814: High-velocity bipolar jets and an Expanding Torus

R. Sahai, W.H.T. Vlemmings, T. Gledhill, C. Sanchez Contreras, E. Lagadec, L-A Nyman, and G. Quintana-Lacaci, ‘ALMA Observations of the Water Fountain Pre-planetary Nebula IRAS 16342-3814: High-velocity Bipolar Jets and an Expanding Torus’, The Astrophysical Journal Letters, Vol 835: L13 (6 pp), published 20 January 2017. The version of record is available online via doi: 10.3847/2041-8213/835/1/L13 © 2017. The American Astronomical Society. All rights reserved.We have mapped 12CO J=3–2 and other molecular lines from the “water fountain” bipolar pre-planetary nebula (PPN) IRAS 16342-3814 with ∼0.35″ resolution using Atacama Large Millimeter/submillimeter Array. We find (i) two very high-speed knotty, jet-like molecular outflows; (ii) a central high-density (>few x106 cm−3), expanding torus of diameter 1300 au; and (iii) the circumstellar envelope of the progenitor AGB, generated by a sudden, very large increase in the mass-loss rate to >3.5 x10-4 Ms yr−1 in the past ∼455 years. Strong continuum emission at 0.89 mm from a central source (690 mJy), if due to thermally emitting dust, implies a substantial mass (0.017 Ms) of very large (∼millimeter-sized) grains. The measured expansion ages of the above structural components imply that the torus (age∼160 years) and the younger high-velocity outflow (age∼110 years) were formed soon after the sharp increase in the AGB mass-loss rate. Assuming a binary model for the jets in IRAS 16342, the high momentum rate for the dominant jet-outflow in IRAS 16342 implies a high minimum accretion rate, ruling out standard Bondi–Hoyle–Lyttleton wind accretion and wind Roche-lobe overflow (RLOF) models with white-dwarf or main-sequence companions. Most likely, enhanced RLOF from the primary or accretion modes operating within common-envelope evolution are needed.Peer reviewedFinal Published versio

The evolutionary status of the semiregular variable QYSge

Repeated spectroscopic observations made with the 6m telescope of yielded new data on the radial-velocity variability of the anomalous yellow supergiant QYSge. The strongest and most peculiar feature in its spectrum is the complex profile of NaI D lines, which contains a narrow and a very wide emission components. The wide emission component can be seen to extend from -170 to +120 km/s, and at its central part it is cut by an absorption feature, which, in turn, is split into two subcomponents by a narrow (16km/s at r=2.5) emission peak. An analysis of all the Vr values leads us to adopt for the star a systemic velocity of Vr=-21.1 km/s, which corresponds to the position of the narrow emission component of NaI. The locations of emission-line features of NaI D lines are invariable, which point to their formation in regions that are external to the supergiant's photosphere. Differential line shifts of about 10km/s are revealed. The absorption lines in the spectrum of QYSge have a substantial width of FWHM~45 km/s. The method of model atmospheres is used to determine the following parameters: Teff=6250K, lg g=2.0, and microturbulence Vt=4.5km/s. The metallicity of the star is found to be somewhat higher than the solar one with an average overabundance of iron-peak elements of [Met/H]=+0.20. The star is found to be slightly overabundant in carbon and nitrogen, [C/Fe]=+0.25, [N/Fe]=+0.27. The alpha-process elements Mg, Si, and Ca are slightly overabundant [alpha/H]=+0.12. The strong sodium excess, [Na/Fe]=+0.75, is likely to be due to the dredge-up of the matter processed in the NeNa cycle. Heavy elements of the s-process are underabundant relative to the Sun. On the whole, the observed properties of QYSge do not give grounds for including this star into the group of RCrB or RVTau-type type objects.Comment: 29 pages, 8 figures, 4 tables; accepted by Astrophys. Bulleti

An equatorial wind from the massive young stellar object S140 IRS 1

The discovery of the second equatorial ionized stellar wind from a massive young stellar object is reported. High resolution radio continuum maps of S140 IRS 1 reveal a highly elongated source that is perpendicular to the larger scale bipolar molecular outflow. This picture is confirmed by location of a small scale monopolar near-IR reflection nebula at the base of the blueshifted lobe. A second epoch of observations over a five year baseline show little ordered outward proper motion of clumps as would have been expected for a jet. A third epoch, taken only 50 days after the second, did show significant changes in the radio morphology. These radio properties can all be understood in the context of an equatorial wind driven by radiation pressure from the central star and inner disc acting on the gas in the surface layers of the disc as proposed by Drew et al. (1998). This equatorial wind system is briefly compared with the one in S106IR, and contrasted with other massive young stellar objects that drive ionized jets.Comment: 19 pages, 5 figures, accepted by ApJ, minor changes in light of referees repor

Confidence intervals for posterior intercepts, with application to the PIAAC literacy survey.

For variance component models, it is often the posterior estimate of the random effect (‘posterior intercept’) rather than the estimate of the fixed effect parameters, which is of main interest. This is the case, for instance, when ranking region–wise mortality rates (where the crude, regional rates are unreliable due to small observed counts) or for the construction of educational league tables from complex sample surveys. However, in order to be able to decide whether two cluster–level units can actually be distinguished, it is clear that one needs a measure of variability of these posterior intercepts. We present an exploration of methods to address this issue which appears to be still undeveloped in the context of the model class considered

UV Circular Polarisation in Star Formation Regions : The Origin of Homochirality?

Ultraviolet circularly polarised light has been suggested as the initial cause of the homochirality of organic molecules in terrestrial organisms, via enantiomeric selection of prebiotic molecules by asymmetric photolysis. We present a theoretical investigation of mechanisms by which ultraviolet circular polarisation may be produced in star formation regions. In the scenarios considered here, light scattering produces only a small percentage of net circular polarisation at any point in space, due to the forward throwing nature of the phase function in the ultraviolet. By contrast, dichroic extinction can produce a fairly high percentage of net circular polarisation (∼10%) and may therefore play a key role in producing an enantiomeric excessPeer reviewe