236 research outputs found
Topology of Pulsar Profiles (ToPP). I. Graph theory method and classification of the EPN
Some of the most important information on a radio pulsar is derived from its
average pulse profile. Many early pulsar studies were necessarily based on only
few such profiles. There, discrete profile components were linked to emission
mechanism models for individual stars through human interpretation. For the
population as a whole, profiles morphology must reflect the geometry and
overall evolution of the radio emitting regions. The problem, however, is that
this population is becoming too large for intensive studies of all sources
individually. Moreover, connecting profiles from a large collection of pulsars
rapidly becomes cumbersome. In this article, we present ToPP, the first-ever
unsupervised method to sort pulsars by profile-shape similarity, using graph
topology. We apply ToPP to the publicly available European Pulsar Network
profile database, providing the first organised visual overview of
multi-frequency profiles representing 90 individual pulsars. We find discrete
evolutionary tracks, varying from simple, single component profiles at all
frequencies, towards diverse mixtures of more complex profiles with frequency
evolution. The profile evolution is continuous, extending out to millisecond
pulsars, and does not fall in sharp classes. We interpret the profiles as a
mixture of pulsar core/cone emission type, spin-down energetics, and the
line-of-sight impact angle towards the magnetic axis. We show how ToPP can
systematically classify sources into the Rankin empirical profile scheme. ToPP
forms one of the key unsupervised methods that will be essential to explore
upcoming pulsar census data such as expected by the Square Kilometer Array.Comment: Submitte
Survey-scale discovery-based research processes: Evaluating a bespoke visualisation environment for astronomical survey data
Next generation astronomical surveys naturally pose challenges for
human-centred visualisation and analysis workflows that currently rely on the
use of standard desktop display environments. While a significant fraction of
the data preparation and analysis will be taken care of by automated pipelines,
crucial steps of knowledge discovery can still only be achieved through various
level of human interpretation. As the number of sources in a survey grows,
there is need to both modify and simplify repetitive visualisation processes
that need to be completed for each source. As tasks such as per-source quality
control, candidate rejection, and morphological classification all share a
single instruction, multiple data (SIMD) work pattern, they are amenable to a
parallel solution. Selecting extragalactic neutral hydrogen (HI) surveys as a
representative example, we use system performance benchmarking and the visual
data and reasoning (VDAR) methodology from the field of information
visualisation to evaluate a bespoke comparative visualisation environment: the
encube visual analytics framework deployed on the 83 Megapixel Swinburne
Discovery Wall. Through benchmarking using spectral cube data from existing HI
surveys, we are able to perform interactive comparative visualisation via
texture-based volume rendering of 180 three-dimensional (3D) data cubes at a
time. The time to load a configuration of spectral cubes scale linearly with
the number of voxels, with independent samples of 180 cubes (8.4 Gigavoxels or
34 Gigabytes) each loading in under 5 minutes. We show that parallel
comparative inspection is a productive and time-saving technique which can
reduce the time taken to complete SIMD-style visual tasks currently performed
at the desktop by at least two orders of magnitude, potentially rendering some
labour-intensive desktop-based workflows obsolete.Comment: 21 pages, 10 figures, Accepted for publication in the Publications of
the Astronomical Society of Australi
Genome-wide linkage scan reveals multiple susceptibility loci influencing lipid and lipoprotein levels in the Québec Family Study
A genome-wide linkage study was performed to identify chromosomal regions harboring genes influencing lipid and lipoprotein levels. Linkage analyses were conducted for four quantitative lipoprotein/lipid traits, i.e., total cholesterol, triglyceride, HDL-cholesterol (HDL-C), and LDL-C concentrations, in 930 subjects enrolled in the Québec Family Study. A maximum of 534 pairs of siblings from 292 nuclear families were available. Linkage was tested using both allele-sharing and variance-component linkage methods. The strongest evidence of linkage was found on chromosome 12q14.1 at marker D12S334 for HDL-C, with a logarithm of the odds (LOD) score of 4.06. Chromosomal regions harboring quantitative trait loci (QTLs) for LDL-C included 1q43 (LOD = 2.50), 11q23.2 (LOD = 3.22), 15q26.1 (LOD = 3.11), and 19q13.32 (LOD = 3.59). In the case of triglycerides, three markers located on 2p14, 11p13, and 11q24.1 provided suggestive evidence of linkage (LOD > 1.75). Tests for total cholesterol levels yielded significant evidence of linkage at 15q26.1 and 18q22.3 with the allele-sharing linkage method, but the results were nonsignificant with the variance-component method. In conclusion, this genome scan provides evidence for several QTLs influencing lipid and lipoprotein levels. Promising candidate genes were located in the vicinity of the genomic regions showing evidence of linkage
3D-Stereoscopic Immersive Analytics Projects at Monash University and University of Konstanz
Immersive Analytics investigates how novel interaction and display technologies may support analytical reasoning and decision making. The Immersive Analytics initiative of Monash University started early 2014. Over the last few years, a number of projects have been developed or extended in this context to meet the requirements of semi- or full-immersive stereoscopic environments. Different technologies are used for this purpose: CAVE2™ (a 330 degree large-scale visualization environment which can be used for educative and scientific group presentations, analyses and discussions), stereoscopic Powerwalls (miniCAVEs, representing a segment of the CAVE2 and used for development and communication), Fishtanks, and/or HMDs (such as Oculus, VIVE, and mobile HMD approaches). Apart from CAVE2™ all systems are or will be employed on both the Monash University and the University of Konstanz side, especially to investigate collaborative Immersive Analytics. In addition, sensiLab extends most of the previous approaches by involving all senses, 3D visualization is combined with multi-sensory feedback, 3D printing, robotics in a scientific-artistic-creative environment
The Apertif Surveys:The First Six Months
Apertif is a new phased-array feed for the Westerbork Synthesis Radio Telescope (WSRT), greatly increasing its field of view and turning it into a natural survey instrument. In July 2019, the Apertif legacy surveys commenced; these are a time-domain survey and a two-tiered imaging survey, with a shallow and medium-deep component. The time-domain survey searches for new (millisecond) pulsars and fast radio bursts (FRBs). The imaging surveys provide neutral hydrogen (HI), radio continuum and polarization data products. With a bandwidth of 300 MHz, Apertif can detect HI out to a redshift of 0.26. The key science goals to be accomplished by Apertif include localization of FRBs (including real-time public alerts), the role of environment and interaction on galaxy properties and gas removal, finding the smallest galaxies, connecting cold gas to AGN, understanding the faint radio population, and studying magnetic fields in galaxies. After a proprietary period, survey data products will be publicly available through the Apertif Long Term Archive (ALTA, https://alta.astron.nl). I will review the progress of the surveys and present the first results from the Apertif surveys, including highlighting the currently available public data
PPARα L162V underlies variation in serum triglycerides and subcutaneous fat volume in young males
<p>Abstract</p> <p>Background</p> <p>Of the five sub-phenotypes defining metabolic syndrome, all are known to have strong genetic components (typically 50–80% of population variation). Studies defining genetic predispositions have typically focused on older populations with metabolic syndrome and/or type 2 diabetes. We hypothesized that the study of younger populations would mitigate many confounding variables, and allow us to better define genetic predisposition loci for metabolic syndrome.</p> <p>Methods</p> <p>We studied 610 young adult volunteers (average age 24 yrs) for metabolic syndrome markers, and volumetric MRI of upper arm muscle, bone, and fat pre- and post-unilateral resistance training.</p> <p>Results</p> <p>We found the PPARα L162V polymorphism to be a strong determinant of serum triglyceride levels in young White males, where carriers of the V allele showed 78% increase in triglycerides relative to L homozygotes (LL = 116 ± 11 mg/dL, LV = 208 ± 30 mg/dL; p = 0.004). Men with the V allele showed lower HDL (LL = 42 ± 1 mg/dL, LV = 34 ± 2 mg/dL; p = 0.001), but women did not. Subcutaneous fat volume was higher in males carrying the V allele, however, exercise training increased fat volume of the untrained arm in V carriers, while LL genotypes significantly decreased in fat volume (LL = -1,707 ± 21 mm<sup>3</sup>, LV = 17,617 ± 58 mm<sup>3 </sup>; p = 0.002), indicating a systemic effect of the V allele on adiposity after unilateral training. Our study suggests that the primary effect of PPARα L162V is on serum triglycerides, with downstream effects on adiposity and response to training.</p> <p>Conclusion</p> <p>Our results on association of PPARα and triglycerides in males showed a much larger effect of the V allele than previously reported in older and less healthy populations. Specifically, we showed the V allele to increase triglycerides by 78% (p = 0.004), and this single polymorphism accounted for 3.8% of all variation in serum triglycerides in males (p = 0.0037).</p
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