205 research outputs found
Identifying galaxy candidates in WSRT HI imaging of ultra-compact high velocity clouds
Ultra-compact high velocity clouds (UCHVCs) were identified in the ALFALFA HI
survey as potential gas-bearing dark matter halos. Here we present higher
resolution neutral hydrogen (HI) observations of twelve UCHVCS with the
Westerbork Synthesis Radio Telescope (WSRT). The UCHVCs were selected based on
a combination of size, isolation, large recessional velocity and high column
density as the best candidate dark matter halos. The WSRT data were tapered to
image the UCHVCs at 210" (comparable to Arecibo) and 105" angular resolution.
In a comparison of the single-dish to interferometer data, we find that the
line flux recovered in the WSRT observations is comparable to that from the
single-dish ALFALFA data. In addition, any structure seen in the ALFALFA data
is reproduced in the WSRT maps at the same angular resolution. At 210'"
resolution all the sources are generally compact with a smooth HI morphology,
as expected from their identification as UCHVCs. At the higher angular
resolution, a majority of the sources break into small clumps contained in a
diffuse envelope. These UCHVCs also have no ordered velocity motion and are
most likely Galactic halo clouds. We identify two UCHVCs, AGC 198606 and AGC
249525, as excellent galaxy candidates based on maintaining a smooth HI
morphology at higher angular resolution and showing ordered velocity motion
consistent with rotation. A third source, AGC 249565, lies between these two
populations in properties and is a possible galaxy candidate. If interpreted as
gas-bearing dark matter halos, the three candidate galaxies have rotation
velocities of 8-15 km/s, HI masses of 0.6-50 x 10^5 Msun, HI radii of 0.3-2
kpc, and dynamical masses of 2-20 x 10^7 Msun for a range of plausible
distances. These are the UCHVCs with the highest column density values in the
ALFALFA HI data and we suggest this is the best way to identify further
candidates.Comment: Accepted for publication in A&A. 26 pages, 19 figures, 5 table
Learning to rank from medical imaging data
Medical images can be used to predict a clinical score coding for the
severity of a disease, a pain level or the complexity of a cognitive task. In
all these cases, the predicted variable has a natural order. While a standard
classifier discards this information, we would like to take it into account in
order to improve prediction performance. A standard linear regression does
model such information, however the linearity assumption is likely not be
satisfied when predicting from pixel intensities in an image. In this paper we
address these modeling challenges with a supervised learning procedure where
the model aims to order or rank images. We use a linear model for its
robustness in high dimension and its possible interpretation. We show on
simulations and two fMRI datasets that this approach is able to predict the
correct ordering on pairs of images, yielding higher prediction accuracy than
standard regression and multiclass classification techniques
PREDICTING THE OUTCOME OF RODENTICIDE TRIALS AGAINST NORWAY RATS LIVING ON FARMS
Difenacoum and bromadiolone treatments against Norway rats may fail because: 1) the animals eat little or no bait, 2) reinvasion rapidly offsets any success, or 3) the population contains resistant individuals. By monitoring bait takes and employing independent measures of rat activity such as tracking plates, it is possible to identify, often in the early stages of a treatment, patterns that indicate the contribution of each of these causes to the eventual outcome. If there is no bait take from the majority of bait points visited by rats in the first week then the treatment is unlikely to be successful, no matter how long it continues. Furthermore, treatments carried out on arable farms, where cereals are stored and the environment is relatively undisturbed, are likely to be less successful than those carried out on livestock farms, where alternative food may also be abundant but where the environment is less predictable. Bait takes that persist at the same bait points for longer than 16 days strongly suggest the presence of resistant rats, while immigration may be significantly affecting the treatment if takes recur at more than 30% of points after a period of seven days. Once a given problem has been identified remedial measures can be taken
Siderophore Biosynthesis But Not Reductive Iron Assimilation Is Essential for Aspergillus fumigatus Virulence
The ability to acquire iron in vivo is essential for most microbial pathogens. Here we show that Aspergillus fumigatus does not have specific mechanisms for the utilization of host iron sources. However, it does have functional siderophore-assisted iron mobilization and reductive iron assimilation systems, both of which are induced upon iron deprivation. Abrogation of reductive iron assimilation, by inactivation of the high affinity iron permease (FtrA), has no effect on virulence in a murine model of invasive aspergillosis. In striking contrast, A. fumigatus l-ornithine-N 5-monooxygenase (SidA), which catalyses the first committed step of hydroxamate-type siderophore biosynthesis, is absolutely essential for virulence. Thus, A. fumigatus SidA is an essential virulence attribute. Combined with the absence of a sidA ortholog—and the fungal siderophore system in general—in mammals, these data demonstrate that the siderophore biosynthetic pathway represents a promising new target for the development of antifungal therapies
How the World Changed Social Media
How the World Changed Social Media is the first book in Why We Post, a book series that investigates the findings of nine anthropologists who each spent 15 months living in communities across the world. This book offers a comparative analysis summarising the results of the research and exploring the impact of social media on politics and gender, education and commerce. What is the result of the increased emphasis on visual communication? Are we becoming more individual or more social? Why is public social media so conservative? Why does equality online fail to shift inequality offline? How did memes become the moral police of the internet? Supported by an introduction to the project’s academic framework and theoretical terms that help to account for the findings, the book argues that the only way to appreciate and understand something as intimate and ubiquitous as social media is to be immersed in the lives of the people who post. Only then can we discover how people all around the world have already transformed social media in such unexpected ways and assess the consequences.published_or_final_versio
Improving behavioral support for smoking cessation in pregnancy: what are the barriers to stopping and which behavior change techniques can influence these? Application of Theoretical Domains Framework.
Behavioral support interventions are used to help pregnant smokers stop; however, of those tested, few are proven effective. Systematic research developing effective pregnancy-specific behavior change techniques (BCTs) is ongoing. This paper reports contributory work identifying potentially-effective BCTs relative to known important barriers and facilitators (B&Fs) to smoking cessation in pregnancy; to detect priority areas for BCTs development. A Nominal Group Technique with cessation experts (n = 12) elicited an expert consensus on B&Fs most influencing women’s smoking cessation and those most modifiable through behavioral support. Effective cessation interventions in randomized trials from a recent Cochrane review were coded into component BCTs using existing taxonomies. B&Fs were categorized using Theoretical Domains Framework (TDF) domains. Matrices, mapping BCT taxonomies against TDF domains, were consulted to investigate the extent to which BCTs in existing interventions target key B&Fs. Experts ranked “smoking a social norm” and “quitting not a priority” as most important barriers and “desire to protect baby” an important facilitator to quitting. From 14 trials, 23 potentially-effective BCTs were identified (e.g., information about consequences). Most B&Fs fell into “Social Influences”, “Knowledge”, “Emotions” and “Intentions” TDF domains; few potentially-effective BCTs mapped onto every TDF domain. B&Fs identified by experts as important to cessation, are not sufficiently targeted by BCT’s currently within interventions for smoking cessation in pregnancy
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