10,095 research outputs found
Sedentary behaviour and diet across the lifespan: an updated systematic review.
Sedentary behaviour and its association with dietary intake in young people and adults are important topics and were systematically reviewed in 2011. There is a need to update this evidence given the changing nature of sedentary behaviour and continued interest in this field. This review aims to assist researchers in better interpreting the diversity of findings concerning sedentary behaviour and weight status
Optimizing Pulsar Timing Arrays to Maximize Gravitational Wave Single Source Detection: a First Cut
Pulsar Timing Arrays (PTAs) use high accuracy timing of a collection of low
timing noise pulsars to search for gravitational waves in the microhertz to
nanohertz frequency band. The sensitivity of such a PTA depends on (a) the
direction of the gravitational wave source, (b) the timing accuracy of the
pulsars in the array and (c) how the available observing time is allocated
among those pulsars. Here, we present a simple way to calculate the sensitivity
of the PTA as a function of direction of a single GW source, based only on the
location and root-mean-square residual of the pulsars in the array. We use this
calculation to suggest future strategies for the current North American
Nanohertz Observatory for Gravitational Waves (NANOGrav) PTA in its goal of
detecting single GW sources. We also investigate the affects of an additional
pulsar on the array sensitivity, with the goal of suggesting where PTA pulsar
searches might be best directed. We demonstrate that, in the case of single GW
sources, if we are interested in maximizing the volume of space to which PTAs
are sensitive, there exists a slight advantage to finding a new pulsar near
where the array is already most sensitive. Further, the study suggests that
more observing time should be dedicated to the already low noise pulsars in
order to have the greatest positive effect on the PTA sensitivity. We have made
a web-based sensitivity mapping tool available at http://gwastro.psu.edu/ptasm.Comment: 14 pages, 3 figures, accepted by Ap
Discovery of 28 pulsars using new techniques for sorting pulsar candidates
Modern pulsar surveys produce many millions of candidate pulsars, far more
than can be individually inspected. Traditional methods for filtering these
candidates, based upon the signal-to-noise ratio of the detection, cannot
easily distinguish between interference signals and pulsars. We have developed
a new method of scoring candidates using a series of heuristics which test for
pulsar-like properties of the signal. This significantly increases the
sensitivity to weak pulsars and pulsars with periods close to interference
signals. By applying this and other techniques for ranking candidates from a
previous processing of the Parkes Multi-beam Pulsar Survey, 28 previously
unknown pulsars have been discovered. These include an eccentric binary system
and a young pulsar which is spatially coincident with a known supernova
remnant.Comment: To be published in Monthly Notices of the Royal Astronomical Society.
11 pages, 9 figure
Pulsar timing analysis in the presence of correlated noise
Pulsar timing observations are usually analysed with least-square-fitting
procedures under the assumption that the timing residuals are uncorrelated
(statistically "white"). Pulsar observers are well aware that this assumption
often breaks down and causes severe errors in estimating the parameters of the
timing model and their uncertainties. Ad hoc methods for minimizing these
errors have been developed, but we show that they are far from optimal.
Compensation for temporal correlation can be done optimally if the covariance
matrix of the residuals is known using a linear transformation that whitens
both the residuals and the timing model. We adopt a transformation based on the
Cholesky decomposition of the covariance matrix, but the transformation is not
unique. We show how to estimate the covariance matrix with sufficient accuracy
to optimize the pulsar timing analysis. We also show how to apply this
procedure to estimate the spectrum of any time series with a steep red
power-law spectrum, including those with irregular sampling and variable error
bars, which are otherwise very difficult to analyse.Comment: Accepted by MNRA
A non-contact, thermal noise based method for the calibration of lateral deflection sensitivity in atomic force microscopy
Calibration of lateral forces and displacements has been a long standing problem in lateral force microscopies. Recently, it was shown by Wagner et al. that the thermal noise spectrum of the first torsional mode may be used to calibrate the deflection sensitivity of the detector. This method is quick, non-destructive and may be performed in situ in air or liquid. Here we make a full quantitative comparison of the lateral inverse optical lever sensitivity obtained by the lateral thermal noise method and the shape independent method developed by Anderson et al. We find that the thermal method provides accurate results for a wide variety of rectangular cantilevers, provided that the geometry of the cantilever is suitable for torsional stiffness calibration by the torsional Sader method, in-plane bending of the cantilever may be eliminated or accounted for and that any scaling of the lateral deflection signal between the measurement of the lateral thermal noise and the measurement of the lateral deflection is eliminated or corrected for. We also demonstrate that the thermal method may be used to characterize the linearity of the detector signal as a function of position, and find a deviation of less than 8% for the instrument used
Observations of Six Glitches in PSR B1737-30
Six glitches have been recently observed in the rotational frequency of the
young pulsar PSR B1737-30 (J1740-3015) using the 25-m Nanshan telescope of
Urumqi Observatory. With a total of 20 glitches in 20 years, it is one of the
most frequently glitching pulsars of the about 1750 known pulsars. Glitch
amplitudes are very variable with fractional increases in rotation rate ranging
from 10^{-9} to 10^{-6}. Inter-glitch intervals are also very variable, but no
relationship is observed between interval and the size of the preceding glitch.
There is a persistent increase in |\dot\nu|, opposite in sign to that expected
from slowdown with a positive braking index, which may result from changes in
the effective magnetic dipole moment of the star during the glitch.Comment: 7 pages, 10 figure
Natriuretic peptide receptors regulate cytoprotective effects in a human ex vivo 3D/bioreactor model
© 2013 Peake et al.; licensee BioMed Central Ltd. This is an open access article distributed under the terms of the Creative Commons
Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in
any medium, provided the original work is properly cited
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