1,034 research outputs found
In Fact, It’s a Matter of Opinion: Determining a Distinction Between Fact and Opinion within the New Zealand Defence of Honest Opinion
This paper discusses the distinction between fact and opinion within the defence of honest opinion. It is argued that the classic legal tests for determining that distinction are largely unhelpful and produce unpredictable results, which trigger a chilling effect on speech. This paper advocates for an adaptation of the four-factor totality of circumstances test, established in Ollman v Evans 750 F 2d 970 (DC Cir 1984), to be inserted into the New Zealand Defamation Act 1992. This would provide more clarity, consistency and predictability for the defence of honest opinion in New Zealand, thereby better supporting freedom of expression under s14 of the New Zealand Bill of Rights Act 1990
Diffuse radio emission in MACS J0025.41222: the effect of a major merger on bulk separation of ICM components
Mergers of galaxy clusters are among the most energetic events in the
Universe. These events have significant impact on the intra-cluster medium,
depositing vast amounts of energy - often in the form of shocks - as well as
heavily influencing the properties of the constituent galaxy population. Many
clusters have been shown to host large-scale diffuse radio emission, known
variously as radio haloes and relics. These sources arise as a result of
electron (re-)acceleration in cluster-scale magnetic fields, although the
processes by which this occurs are still poorly understood. We present new,
deep radio observations of the high-redshift galaxy cluster MACS
J0025.41222, taken with the GMRT at 325 MHz, as well as new analysis of all
archival X-ray observations. We aim to investigate the potential of
diffuse radio emission and categorise the radio population of this cluster,
which has only been covered previously by shallow radio surveys. We produce
low-resolution maps of MACS J0025.41222 through a combination of uv-tapering
and subtracting the compact source population. Radial surface brightness and
mass profiles are derived from the data. We also derive a 2D map of
the ICM temperature. For the first time, two sources of diffuse radio emission
are detected in MACS J0025.41222, on linear scales of several hundred kpc.
Given the redshift of the cluster and the assumed cosmology, these sources
appear to be consistent with established trends in power scaling relations for
radio relics. The X-ray temperature map presents evidence of an asymmetric
temperature profile and tentative identification of a temperature jump
associated with one relic. We classify the pair of diffuse radio sources in
this cluster as a pair of radio relics, given their consistency with scaling
relations, location toward the cluster outskirts, and the available X-ray data.Comment: 20 pages, 15 figures, accepted for publication in A&
Early Science with the Karoo Array Telescope: a Mini-Halo Candidate in Galaxy Cluster Abell 3667
Abell 3667 is among the most well-studied galaxy clusters in the Southern
Hemisphere. It is known to host two giant radio relics and a head-tail radio
galaxy as the brightest cluster galaxy. Recent work has suggested the
additional presence of a bridge of diffuse synchrotron emission connecting the
North-Western radio relic with the cluster centre. In this work, we present
full-polarization observations of Abell 3667 conducted with the Karoo Array
Telescope at 1.33 and 1.82 GHz. Our results show both radio relics as well as
the brightest cluster galaxy. We use ancillary higher-resolution data to
subtract the emission from this galaxy, revealing a localised excess, which we
tentatively identify as a radio mini-halo. This mini-halo candidate has an
integrated flux density of mJy beam at 1.37 GHz,
corresponding to a radio power of P
W Hz, consistent with established trends in mini-halo power scaling.Comment: 17 pages, 10 figures, accepted MNRA
Optimal Bayesian Quickest Detection for Hidden Markov Models and Structured Generalisations
In this paper we consider the problem of quickly detecting changes in hidden
Markov models (HMMs) in a Bayesian setting, as well as several structured
generalisations including changes in statistically periodic processes, quickest
detection of a Markov process across a sensor array, quickest detection of a
moving target in a sensor network and quickest change detection (QCD) in
multistream data. Our main result establishes an optimal Bayesian HMM QCD rule
with a threshold structure. This framework and proof techniques allow us to to
elegantly establish optimal rules for several structured generalisations by
showing that these problems are special cases of the Bayesian HMM QCD problem.
We develop bounds to characterise the performance of our optimal rule and
provide an efficient method for computing the test statistic. Finally, we
examine the performance of our rule in several simulation examples and propose
a technique for calculating the optimal threshold
An Engineered Community Approach for Industrial Cultivation of Microalgae.
Although no species lives in isolation in nature, efforts to grow organisms for use in biotechnology have generally focused on a single-species approach, particularly where a product is required at high purity. In such scenarios, preventing the establishment of contaminants requires considerable effort that is economically justified. However, for some applications in biotechnology where the focus is on lower-margin biofuel production, axenic culture is not necessary, provided yields of the desired strain are unaffected by contaminants. In this article, we review what is known about interspecific interactions of natural algal communities, the dynamics of which are likely to parallel contamination in industrial systems. Furthermore, we discuss the opportunities to improve both yields and the stability of cultures by growing algae in multi-species consortia.EK acknowledges funding from the FP7 DEMA project (Reference number 309086). ASR received funding from the People Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme FP7/2007-2013/ under REA grant agreement n° 317184.This is the accepted manuscript. This is a copy of an article published in Industrial Biotechnology © 2014 [copyright Mary Ann Liebert, Inc.]; Industrial Biotechnology is available online at: http://online.liebertpub.com
Polarized accretion shocks from the cosmic web
On the largest scales, galaxies are pulled together by gravity to form
clusters, which are connected by filaments making a web-like pattern. Radio
emission is predicted from this cosmic web, which should originate from the
strong accretion shocks around the cosmic structures. We present the first
observational evidence that Fermi-type acceleration from strong shocks
surrounding the filaments of the cosmic web, as well as in peripherals of
low-mass clusters, is at work in the Universe. Using all-sky radio maps and
stacking on clusters and filaments, we have detected the polarization signature
of the synchrotron emission with polarization fractions >= 20%, which is best
explained by the organization of local magnetic fields by strong shock waves
both at the cluster peripheries and between clusters. Our interpretation is
well supported by a detailed comparison with state-of-the-art cosmological
simulations.Comment: Published in Science Advances. Supplementary Materials available at
https://www.science.org/doi/10.1126/sciadv.ade723
On the absence of radio halos in clusters with double relics
Pairs of radio relics are believed to form during cluster mergers, and are
best observed when the merger occurs in the plane of the sky. Mergers can also
produce radio halos, through complex processes likely linked to turbulent
re-acceleration of cosmic-ray electrons. However, only some clusters with
double relics also show a radio halo. Here, we present a novel method to derive
upper limits on the radio halo emission, and analyse archival X-ray Chandra
data, as well as galaxy velocity dispersions and lensing data, in order to
understand the key parameter that switches on radio halo emission. We place
upper limits on the halo power below the
correlation for some clusters, confirming that clusters with double relics have
different radio properties. Computing X-ray morphological indicators, we find
that clusters with double relics are associated with the most disturbed
clusters. We also investigate the role of different mass-ratios and
time-since-merger. Data do not indicate that the merger mass ratio has an
impact on the presence or absence of radio halos (the null hypothesis that the
clusters belong to the same group cannot be rejected). However, the data
suggests that the absence of radio halos could be associated with early and
late mergers, but the sample is too small to perform a statistical test. Our
study is limited by the small number of clusters with double relics. Future
surveys with LOFAR, ASKAP, MeerKat and SKA will provide larger samples to
better address this issue.Comment: 12 pages, 7 figures, MNRAS accepte
Deep observations of the Super-CLASS super-cluster at 325 MHz with the GMRT: the low-frequency source catalogue
We present the results of 325 MHz GMRT observations of a super-cluster field,
known to contain five Abell clusters at redshift . We achieve a
nominal sensitivity of Jy beam toward the phase centre. We
compile a catalogue of 3257 sources with flux densities in the range
within the entire square degree
field of view. Subsequently, we use available survey data at other frequencies
to derive the spectral index distribution for a sub-sample of these sources,
recovering two distinct populations -- a dominant population which exhibit
spectral index trends typical of steep-spectrum synchrotron emission, and a
smaller population of sources with typically flat or rising spectra. We
identify a number of sources with ultra-steep spectra or rising spectra for
further analysis, finding two candidate high-redshift radio galaxies and three
gigahertz-peaked-spectrum radio sources. Finally, we derive the
Euclidean-normalised differential source counts using the catalogue compiled in
this work, for sources with flux densities in excess of Jy. Our
differential source counts are consistent with both previous observations at
this frequency and models of the low-frequency source population. These
represent the deepest source counts yet derived at 325 MHz. Our source counts
exhibit the well-known flattening at mJy flux densities, consistent with an
emerging population of star-forming galaxies; we also find marginal evidence of
a downturn at flux densities below Jy, a feature so far only seen
at 1.4 GHz.Comment: 25 pages, 18 figures, 10 tables. Accepted for publication in MNRA
An experimental evaluation of the effects of geolocator design and attachment method on between-year survival on Whinchats Saxicola rubetra
Data from location logging tags have revolutionised our understanding of migration ecology, but methods of tagging that do not compromise survival need to be identified. We compared resighting rates for 156 geolocator-tagged and 316 colour ringed-only whinchats on their African wintering grounds after migration to and from eastern Europe in two separate years. We experimentally varied both light stalk length (0, 5 and 10 mm) and harness material (elastic or non-elastic nylon braid tied on, leg-loop ‘Rappole’ harnesses) in the second year using a reasonably balanced design (all tags in the first year used an elastic harness and 10 mm light stalk). Tags weighed 0.63 g (0.01 SE), representing 4.1% of average body mass. There was no overall significant reduction in between-year resighting rate (our proxy for survival) comparing tagged and untagged birds in either year. When comparing within tagged birds, however, using a tied harness significantly reduced resighting rate by 53% on average compared to using an elastic harness (in all models), but stalk length effects were not statistically significant in any model considered. There was no strong evidence that the fit (relative tightness) or added tag mass affected survival, although tied tags were fitted more tightly later in the study, and birds fitted with tied tags later may have had lower survival. Overall, on a precautionary principle, deploying tags with non-elastic tied harnesses should be avoided because the necessary fit, so as not to reduce survival, is time-consuming to achieve and does not necessarily improve with experience. Geolocator tags of the recommended percentage of body mass fitted with elastic leg-loop harnesses and with short light stalks can be used without survival effects in small long-distance migrant birds.PostprintPeer reviewe
Cold gas outflows from the Small Magellanic Cloud traced with ASKAP
Feedback from massive stars plays a critical role in the evolution of the
Universe by driving powerful outflows from galaxies that enrich the
intergalactic medium and regulate star formation. An important source of
outflows may be the most numerous galaxies in the Universe: dwarf galaxies.
With small gravitational potential wells, these galaxies easily lose their
star-forming material in the presence of intense stellar feedback. Here, we
show that the nearby dwarf galaxy, the Small Magellanic Cloud (SMC), has atomic
hydrogen outflows extending at least 2 kiloparsecs (kpc) from the star-forming
bar of the galaxy. The outflows are cold, , and may have formed
during a period of active star formation million years (Myr) ago. The
total mass of atomic gas in the outflow is solar masses, , or % of the total atomic gas of the galaxy. The inferred
mass flux in atomic gas alone, , is up to an order of magnitude greater than the star
formation rate. We suggest that most of the observed outflow will be stripped
from the SMC through its interaction with its companion, the Large Magellanic
Cloud (LMC), and the Milky Way, feeding the Magellanic Stream of hydrogen
encircling the Milky Way.Comment: Published in Nature Astronomy, 29 October 2018,
http://dx.doi.org/10.1038/s41550-018-0608-
- …