219 research outputs found
Finding strong lenses in CFHTLS using convolutional neural networks
We train and apply convolutional neural networks, a machine learning
technique developed to learn from and classify image data, to
Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) imaging for the
identification of potential strong lensing systems. An ensemble of four
convolutional neural networks was trained on images of simulated galaxy-galaxy
lenses. The training sets consisted of a total of 62,406 simulated lenses and
64,673 non-lens negative examples generated with two different methodologies.
The networks were able to learn the features of simulated lenses with accuracy
of up to 99.8% and a purity and completeness of 94-100% on a test set of 2000
simulations. An ensemble of trained networks was applied to all of the 171
square degrees of the CFHTLS wide field image data, identifying 18,861
candidates including 63 known and 139 other potential lens candidates. A second
search of 1.4 million early type galaxies selected from the survey catalog as
potential deflectors, identified 2,465 candidates including 117 previously
known lens candidates, 29 confirmed lenses/high-quality lens candidates, 266
novel probable or potential lenses and 2097 candidates we classify as false
positives. For the catalog-based search we estimate a completeness of 21-28%
with respect to detectable lenses and a purity of 15%, with a false-positive
rate of 1 in 671 images tested. We predict a human astronomer reviewing
candidates produced by the system would identify ~20 probable lenses and 100
possible lenses per hour in a sample selected by the robot. Convolutional
neural networks are therefore a promising tool for use in the search for lenses
in current and forthcoming surveys such as the Dark Energy Survey and the Large
Synoptic Survey Telescope.Comment: 16 pages, 8 figures. Accepted by MNRA
Developing a representative driving cycle for paratransit that reflects measured data transients: case study in Stellenbosch, South Africa
Paratransit plays a critical role in meeting transportation needs in many cities in sub-Saharan Africa (SSA). However, it faces deep issues related to pollution, congestion, and safety. Understanding the driving patterns of paratransit in SSA can provide valuable insights into the transportation needs in the region, which is particularly relevant nowadays given the increasing focus on sustainable transportation solutions in Africa.
Representative driving cycles, which provide a realistic simulation of the driving conditions a vehicle is likely to encounter, are key to framing policies for effective transportation management, vehicle design, and urban and regional planning. However, cycle development has been limited in SSA due to a lack of data and standardized testing procedures. This study develops a representative driving cycle using GPS data gathered on paratransit vehicles traveling around Stellenbosch, South Africa, providing a benchmark for evaluation and a platform for further research and testing in SSAâs dominant transport industry.
A novel time series shape-based clustering methodology is employed that combines dynamic time warping and mixed integer programming to cluster micro-trips of varying length based on their time series shapes. Representative micro-trips from each cluster are stitched together with a maximum likelihood approach to curate the final cycle. By including transients from the measured data in cycle development, this novel approach to cycle development is particularly suited for capturing the notoriously unconventional and aggressive driving style of paratransit.
The constructed cycle and several international cycles are assessed against the measured database on the basis of eight characteristic kinematic parameters. The constructed cycle emerges as the most fitting choice to represent paratransit operating conditions, with an average deviance of 3.65% across the parameters, compared to deviations of 23%â34% for the international cycles
High fidelity estimates of paratransit energy consumption from per-second GPS tracking data
Paratransit, in particular the minibus taxi, is the mainstay of public transport in sub-Saharan Africa. These vehicles are often second-hand, ageing, fuel inefficient, and expensive to operate - issues that electrification can ameliorate. However, modeling and planning large-scale transitions to electric paratransit require reliable estimates of vehicle energy consumption. This paper provides such estimates by applying a vehicle kinetic model to per-second GPS data gathered on minibus taxis. Data include 62 trips across three routes with different driving conditions near Stellenbosch, South Africa. We find a range of energy consumption from 0.29 to 0.51 kWh/km (mean = 0.39 kWh/km). Past estimates in literature relied on per-minute GPS data, which we show leads to inaccurate energy consumption estimates. We recommend new kWh/km values for modeling vehicle operations and grid impact, and discuss how future work can utilize our analysis to advance the transition to electric paratransit sub-Saharan Africa
H0LiCOW III. Quantifying the effect of mass along the line of sight to the gravitational lens HE 0435-1223 through weighted galaxy counts
Based on spectroscopy and multiband wide-field observations of the
gravitationally lensed quasar HE 0435-1223, we determine the probability
distribution function of the external convergence for
this system. We measure the under/overdensity of the line of sight towards the
lens system and compare it to the average line of sight throughout the
universe, determined by using the CFHTLenS as a control field. Aiming to
constrain as tightly as possible, we determine
under/overdensities using various combinations of relevant informative weighing
schemes for the galaxy counts, such as projected distance to the lens,
redshift, and stellar mass. We then convert the measured under/overdensities
into a distribution, using ray-tracing through the
Millennium Simulation. We explore several limiting magnitudes and apertures,
and account for systematic and statistical uncertainties relevant to the
quality of the observational data, which we further test through simulations.
Our most robust estimate of has a median value
and a standard deviation of
. The measured corresponds to
uncertainty on the time delay distance, and hence the Hubble constant
inference from this system. The median value
is robust to (i.e. on ) regardless of the adopted
aperture radius, limiting magnitude and weighting scheme, as long as the latter
incorporates galaxy number counts, the projected distance to the main lens, and
a prior on the external shear obtained from mass modeling. The availability of
a well-constrained makes \hequad\ a valuable system for
measuring cosmological parameters using strong gravitational lens time delays.Comment: 24 pages, 17 figures, 6 tables. Submitted to MNRA
Endothelial colony-forming cells ameliorate endothelial dysfunction via secreted factors following ischemia-reperfusion injury
Damage to endothelial cells contributes to acute kidney injury (AKI) by leading to impaired perfusion. Endothelial colony-forming cells (ECFC) are endothelial precursor cells with high proliferative capacity, pro-angiogenic activity, and in vivo vessel forming potential. We hypothesized that ECFC may ameliorate the degree of AKI and/or promote repair of the renal vasculature following ischemia-reperfusion (I/R). Rat pulmonary microvascular endothelial cells (PMVEC) with high proliferative potential were compared with pulmonary artery endothelial cells (PAEC) with low proliferative potential in rats subjected to renal I/R. PMVEC administration reduced renal injury and hastened recovery as indicated by serum creatinine and tubular injury scores, while PAEC did not. Vehicle-treated control animals showed consistent reductions in renal medullary blood flow (MBF) within 2 h of reperfusion, while PMVEC protected against loss in MBF as measured by laser Doppler. Interestingly, PMVEC mediated protection occurred in the absence of homing to the kidney. Conditioned medium (CM) from human cultured cord blood ECFC also conveyed beneficial effects against I/R injury and loss of MBF. Moreover, ECFC-CM significantly reduced the expression of ICAM-1 and decreased the number of differentiated lymphocytes typically recruited into the kidney following renal ischemia. Taken together, these data suggest that ECFC secrete factors that preserve renal function post ischemia, in part, by preserving microvascular function
Kinetic and structureâactivity studies of the triazolium ion-catalysed benzoin condensation
Steady-state kinetic and structureâactivity studies of a series of six triazolium-ion pre-catalysts 2aâ2f were investigated for the benzoin condensation. These data provide quantitative insight into the role of triazolium N-aryl substitution under synthetically relevant catalytic conditions in a polar solvent environment. Kinetic behaviour was significantly different to that previously reported for a related thiazolium-ion pre-catalyst 1, with the observed levelling of initial rate constants to νmax at high aldehyde concentrations for all triazolium catalysts. Values for νmax for 2aâ2f increase with electron withdrawing N-aryl substituents, in agreement with reported optimal synthetic outcomes under catalytic conditions, and vary by 75-fold across the series. The levelling of rate constants supports a change in rate-limiting step and evidence supports the assignment of the Breslow-intermediate forming step to the plateau region. Correlation of νmax reaction data yielded a positive Hammett Ď-value (Ď = +1.66) supporting the build up of electron density adjacent to the triazolium N-Ar in the rate-limiting step favoured by electron withdrawing N-aryl substituents. At lower concentrations of aldehyde, both Breslow-intermediate and benzoin formation are partially rate-limiting
Parental perceptions and understanding of information provision, management options and factors influencing the decision-making process in the treatment of children with glue ear
Objectives
Otitis media with effusion (OME) is a common cause of hearing loss and possible developmental delay in children, and there are a range of âpreference sensitiveâ treatment options. We aimed to evaluate the attitudes and beliefs of parents of affected children to treatment options including watchful-waiting, hearing aids, grommets, and, oral steroids with the intention of developing our understanding of decision-making and the factors influencing it, sources of parental information, and satisfaction with information provision.
Design
We recruited a convenience sample of twelve parents of eleven children with OME at a single ENT department of a teaching hospital into a qualitative research study. The children of the parents interviewed had already been recruited into the Oral Steroids for the Resolution of Otitis Media with effusion In Children (OSTRICH) study. Semi structured interviews were audio recorded, transcribed and then coded using an inductive, thematic approach.
Results
Parents were satisfied with the verbal provision of information during the treatment consultation, although many were keen to receive supplementary printed information. Discussion with family and friends helped the decision-making process, whereas insufficient information and a paternalistic approach were viewed as obstacles. Parents were particularly influenced by the following: the immediacy of the treatment option effect, perceived efficacy, perceived risks and adverse effects, social implications (especially with hearing aids) and past personal and informant experience.
Conclusions
Parents appreciate clinicians tailoring information provision to parents' information needs and preferred format. Clinicians should also elicit parental attitudes towards the different management options for OME and the factors influencing their decisions, in order to optimise shared-decision making and ultimately provide a better standard of clinical care
The Power of 8: Encouraging Collaborative DIY Futures
"The Power of 8" was an experimental futures project, collaboratively driven by an ad hoc team of eight people from different walks of life. The aim was to explore new pathways for creating democratic futures by building a public discourse around the aspirations of ordinary people. The team of eight comprised a Designer/Speculator, an Educator, an Interaction Designer, a Permaculturist, a Policy Researcher, an Urbanist, a retired Civil Servant, and a Biomedical Scientist.
Through a series of three intensive workshops, and later a wider public engagement phase, we adopted a narrative approach to building a collective view, representing possible futures of Brentford in London, England. This paper describes the strategies we used â including maps, montage and storytelling â to develop concepts, visualise proposals and materialise âfuture artefactsâ during the project
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