1,235 research outputs found
The calibration of WET-sensor for volumetric water content and pore water electrical conductivity in different horticultural substrates
Effectiveness and cost-effectiveness of a telehealth intervention to support the management of long-term conditions:study protocol for two linked randomized controlled trials
As the population ages, more people are suffering from long-term health conditions (LTCs). Health services around the world are exploring new ways of supporting people with LTCs and there is great interest in the use of telehealth: technologies such as the Internet, telephone and home self-monitoring
Explosion of a massive, He-rich star at z=0.16
We present spectroscopic and photometric data of the peculiar SN 2001gh,
discovered by the 'Southern inTermediate Redshift ESO Supernova Search'
(STRESS) at a redshift z=0.16. SN 2001gh has relatively high luminosity at
maximum (M_B = -18.55 mag), while the light curve shows a broad peak. An
early-time spectrum shows an almost featureless, blue continuum with a few weak
and shallow P-Cygni lines that we attribute to HeI. HeI lines remain the only
spectral features visible in a subsequent spectrum, obtained one month later. A
remarkable property of SN 2001gh is the lack of significant spectral evolution
over the temporal window of nearly one month separating the two spectra. In
order to explain the properties of SN 2001gh, three powering mechanism are
explored, including radioactive decays of a moderately large amount of 56Ni,
magnetar spin-down, and interaction of SN ejecta with circumstellar medium. We
favour the latter scenario, with a SN Ib wrapped in a dense, circumstellar
shell. The fact that no models provide an excellent fit with observations,
confirms the troublesome interpretation of the nature of SN 2001gh. A rate
estimate for SN 2001gh-like event is also provided, confirming the intrinsic
rarity of these objects.Comment: 11 pages, 8 figures, 3 tables. Accepted by MNRA
One thousand days of SN 2015bn: HST imaging shows a light curve flattening consistent with magnetar predictions
We present the first observations of a Type I superluminous supernova (SLSN)
at days after maximum light. We observed SN 2015bn using the
Hubble Space Telescope Advanced Camera for Surveys in the F475W, F625W and
F775W filters at 721 days and 1068 days. SN 2015bn is clearly detected and
resolved from its compact host, allowing reliable photometry. A galaxy template
constructed from these data further enables us to isolate the SLSN flux in deep
ground-based imaging. We measure a light curve decline rate at days of
mag (100 d), much shallower than the earlier evolution,
and slower than previous SLSNe (at any phase) or the decay rate of Co.
Neither additional radioactive isotopes nor a light echo can consistently
account for the slow decline. A spectrum at 1083 days shows the same [O I] and
[Ca II] lines as seen at days, with no new features to indicate
strong circumstellar interaction. Radio limits with the Very Large Array rule
out an extended wind for mass-loss rates M yr (where is the wind velocity in
units of 10 km s). The optical light curve is consistent with , which we show is expected for magnetar spin-down with inefficient
trapping; furthermore, the evolution matches predictions from earlier magnetar
model fits. The opacity to magnetar radiation is constrained at
cm g, consistent with photon-matter pair-production over a broad
GeV-TeV range. This suggests the magnetar spectral energy distribution,
and hence the 'missing energy' leaking from the ejecta, may peak in this range.Comment: Accepted for publication in ApJL, updated to match accepted versio
The Binary Neutron Star event LIGO/VIRGO GW170817 a hundred and sixty days after merger: synchrotron emission across the electromagnetic spectrum
We report deep Chandra, HST and VLA observations of the binary neutron star
event GW170817 at d after merger. These observations show that GW170817
has been steadily brightening with time and might have now reached its peak,
and constrain the emission process as non-thermal synchrotron emission where
the cooling frequency is above the X-ray band and the synchrotron
frequency is below the radio band. The very simple power-law spectrum
extending for eight orders of magnitude in frequency enables the most precise
measurement of the index of the distribution of non-thermal relativistic
electrons accelerated by a shock launched by a
NS-NS merger to date. We find , which indicates that radiation
from ejecta with dominates the observed emission. While
constraining the nature of the emission process, these observations do
\emph{not} constrain the nature of the relativistic ejecta. We employ
simulations of explosive outflows launched in NS ejecta clouds to show that the
spectral and temporal evolution of the non-thermal emission from GW170817 is
consistent with both emission from radially stratified quasi-spherical ejecta
traveling at mildly relativistic speeds, \emph{and} emission from off-axis
collimated ejecta characterized by a narrow cone of ultra-relativistic material
with slower wings extending to larger angles. In the latter scenario, GW170817
harbored a normal SGRB directed away from our line of sight. Observations at
days are unlikely to settle the debate as in both scenarios the
observed emission is effectively dominated by radiation from mildly
relativistic material.Comment: Updated with the latest VLA and Chandra dat
A Decline in the X-ray through Radio Emission from GW170817 Continues to Support an Off-Axis Structured Jet
We present new observations of the binary neutron star merger GW170817 at
days post-merger, at radio (Karl G. Jansky Very Large
Array; VLA), X-ray (Chandra X-ray Observatory) and optical (Hubble Space
Telescope; HST) wavelengths. These observations provide the first evidence for
a turnover in the X-ray light curve, mirroring a decline in the radio emission
at significance. The radio-to-X-ray spectral energy
distribution exhibits no evolution into the declining phase. Our full
multi-wavelength dataset is consistent with the predicted behavior of our
previously published models of a successful structured jet expanding into a
low-density circumbinary medium, but pure cocoon models with a choked jet
cannot be ruled out. If future observations continue to track our predictions,
we expect that the radio and X-ray emission will remain detectable until days post-merger.Comment: Accepted to ApJL. Updated version includes new VLA observations
extending through 2018 June
Historical geography II: traces remain
The second report in this series turns to focus on the trace in relation to life-writing and biography in historical geography and beyond. Through attention to tracing journeys, located moments and listening to the presence of ghosts (Ogborn, 2005), this report seeks to highlight the range of different ways in which historical geographers have explored lives, deaths, and their transient traces through varied biographical terrains. Continuing to draw attention in historical geography to the darkest of histories, this piece will pivot on moments of discovering the dead to showcase the nuanced ways in which historical geography is opening doors into uncharted lives and unspoken histories
Recommended from our members
An investigation of the shortcomings of the CONSORT 2010 statement for the reporting of group sequential randomised controlled trials: a methodological systematic review
Background
It can be argued that adaptive designs are underused in clinical research. We have explored concerns related to inadequate reporting of such trials, which may influence their uptake. Through a careful examination of the literature, we evaluated the standards of reporting of group sequential (GS) randomised controlled trials, one form of a confirmatory adaptive design.
Methods
We undertook a systematic review, by searching Ovid MEDLINE from the 1st January 2001 to 23rd September 2014, supplemented with trials from an audit study. We included parallel group, confirmatory, GS trials that were prospectively designed using a Frequentist approach. Eligible trials were examined for compliance in their reporting against the CONSORT 2010 checklist. In addition, as part of our evaluation, we developed a supplementary checklist to explicitly capture group sequential specific reporting aspects, and investigated how these are currently being reported.
Results
Of the 284 screened trials, 68(24%) were eligible. Most trials were published in “high impact” peer-reviewed journals. Examination of trials established that 46(68%) were stopped early, predominantly either for futility or efficacy. Suboptimal reporting compliance was found in general items relating to: access to full trials protocols; methods to generate randomisation list(s); details of randomisation concealment, and its implementation. Benchmarking against the supplementary checklist, GS aspects were largely inadequately reported. Only 3(7%) trials which stopped early reported use of statistical bias correction. Moreover, 52(76%) trials failed to disclose methods used to minimise the risk of operational bias, due to the knowledge or leakage of interim results. Occurrence of changes to trial methods and outcomes could not be determined in most trials, due to inaccessible protocols and amendments.
Discussion and Conclusions
There are issues with the reporting of GS trials, particularly those specific to the conduct of interim analyses. Suboptimal reporting of bias correction methods could potentially imply most GS trials stopping early are giving biased results of treatment effects. As a result, research consumers may question credibility of findings to change practice when trials are stopped early. These issues could be alleviated through a CONSORT extension. Assurance of scientific rigour through transparent adequate reporting is paramount to the credibility of findings from adaptive trials. Our systematic literature search was restricted to one database due to resource constraints
Spitzer Space Telescope Infrared Observations of the Binary Neutron Star Merger GW170817
We present Spitzer Space Telescope 3.6 and 4.5 micron observations of the
binary neutron star merger GW170817 at 43, 74, and 264 days post-merger. Using
the final observation as a template, we uncover a source at the position of
GW170817 at 4.5 micron with a brightness of 22.9+/-0.3 AB mag at 43 days and
23.8+/-0.3 AB mag at 74 days (the uncertainty is dominated by systematics from
the image subtraction); no obvious source is detected at 3.6 micron to a
3-sigma limit of >23.3 AB mag in both epochs. The measured brightness is dimmer
by a factor of about 2-3 times compared to our previously published kilonova
model, which is based on UV, optical, and near-IR data at <30 days. However,
the observed fading rate and color (m_{3.6}-m_{4.5}> 0 AB mag) are consistent
with our model. We suggest that the discrepancy is likely due to a transition
to the nebular phase, or a reduced thermalization efficiency at such late time.
Using the Spitzer data as a guide, we briefly discuss the prospects of
observing future binary neutron star mergers with Spitzer (in LIGO/Virgo
Observing Run 3) and the James Webb Space Telescope (in LIGO/Virgo Observing
Run 4 and beyond).Comment: 6 pages, 2 figures, submitted to ApJ
The supernova CSS121015:004244+132827: a clue for understanding super-luminous supernovae
We present optical photometry and spectra of the super luminous type II/IIn
supernova CSS121015:004244+132827 (z=0.2868) spanning epochs from -30 days
(rest frame) to more than 200 days after maximum. CSS121015 is one of the more
luminous supernova ever found and one of the best observed. The photometric
evolution is characterized by a relatively fast rise to maximum (~40 days in
the SN rest frame), and by a linear post-maximum decline. The light curve shows
no sign of a break to an exponential tail. A broad Halpha is first detected at
~ +40 days (rest-frame). Narrow, barely-resolved Balmer and [O III] 5007 A
lines, with decreasing strength, are visible along the entire spectral
evolution. The spectra are very similar to other super luminous supernovae
(SLSNe) with hydrogen in their spectrum, and also to SN 2005gj, sometimes
considered a type Ia interacting with H-rich CSM. The spectra are also similar
to a subsample of H-deficient SLSNe. We propose that the properties of
CSS121015 are consistent with the interaction of the ejecta with a massive,
extended, opaque shell, lost by the progenitor decades before the final
explosion, although a magnetar powered model cannot be excluded. Based on the
similarity of CSS121015 with other SLSNe (with and without H), we suggest that
the shocked-shell scenario should be seriously considered as a plausible model
for both types of SLSN.Comment: 17 pages, 10 figures and 5 tables. In press to MNRAS. This version
matches the accepted one. Main conclusions are unchange
- …
