3,355 research outputs found
Mosaicking with cosmic microwave background interferometers
Measurements of cosmic microwave background (CMB) anisotropies by
interferometers offer several advantages over single-dish observations. The
formalism for analyzing interferometer CMB data is well developed in the
flat-sky approximation, valid for small fields of view. As the area of sky is
increased to obtain finer spectral resolution, this approximation needs to be
relaxed. We extend the formalism for CMB interferometry, including both
temperature and polarization, to mosaics of observations covering arbitrarily
large areas of the sky, with each individual pointing lying within the flat-sky
approximation. We present a method for computing the correlation between
visibilities with arbitrary pointing centers and baselines and illustrate the
effects of sky curvature on the l-space resolution that can be obtained from a
mosaic.Comment: 9 pages; submitted to Ap
Glucose Gel as a Potential Alternative Treatment to Infant Formula for Neonatal Hypoglycaemia in Australia
Infant formula is often used as a treatment for neonatal hypoglycaemia in Australia; however, there are concerns that this may jeopardise mother-baby bonding and breastfeeding. Successful use of glucose gel as an alternative treatment for hypoglycaemia has been reported. We wanted to investigate in a pilot study whether the use of glucose gel has the potential to quickly and safely restore normoglycaemia in the infants of diabetic mothers in an Australian setting. Infants with asymptomatic hypoglycaemia were treated with glucose gel (n = 36) and compared to a historical group of infants which had been treated with infant formula (n = 24). Within 15 min of the first treatment, the gel group had a mean blood glucose level (BGL) of 2.6 mmol/L, and 2.7 mmol/L 30 min after the second treatment. This was lower than the BGL after the first treatment for the formula group, which rose to a mean of 2.8 then to 3.2 mmol/L after the second treatment (p = 0.003). In successfully treated infants, administration of the gel resulted in normoglycaemia within 30 min. The likelihood of special care nursery admission was not significantly different between the groups, although we had a small sample size, and our findings should be interpreted with caution. These pilot results provide support for further investigations into the use of glucose gel as an alternative treatment to infant formula
Fermi-LAT and Suzaku Observations of the Radio Galaxy Centaurus B
Centaurus B is a nearby radio galaxy positioned in the Southern hemisphere
close to the Galactic plane. Here we present a detailed analysis of about 43
months of accumulated Fermi-LAT data of the gamma-ray counterpart of the source
initially reported in the 2nd Fermi-LAT catalog, and of newly acquired Suzaku
X-ray data. We confirm its detection at GeV photon energies, and analyze the
extension and variability of the gamma-ray source in the LAT dataset, in which
it appears as a steady gamma-ray emitter. The X-ray core of Centaurus B is
detected as a bright source of a continuum radiation. We do not detect however
any diffuse X-ray emission from the known radio lobes, with the provided upper
limit only marginally consistent with the previously claimed ASCA flux. Two
scenarios that connect the X-ray and gamma-ray properties are considered. In
the first one, we assume that the diffuse non-thermal X-ray emission component
is not significantly below the derived Suzaku upper limit. In this case,
modeling the inverse-Compton emission shows that the observed gamma-ray flux of
the source may in principle be produced within the lobes. This association
would imply that efficient in-situ acceleration of the radiating electrons is
occurring and that the lobes are dominated by the pressure from the
relativistic particles. In the second scenario, with the diffuse X-ray emission
well below the Suzaku upper limits, the lobes in the system are instead
dominated by the magnetic pressure. In this case, the observed gamma-ray flux
is not likely to be produced within the lobes, but instead within the nuclear
parts of the jet. By means of synchrotron self-Compton modeling we show that
this possibility could be consistent with the broad-band data collected for the
unresolved core of Centaurus B, including the newly derived Suzaku spectrum.Comment: Accepted for publication in A&A. 11 page
Ion energy distribution measurements in rf and pulsed dc plasma discharges
A commercial retarding field analyzer is used to measure the time-averaged ion energy distributions of impacting ions at the powered electrode in a 13.56 MHz driven, capacitively coupled, parallel plate discharge operated at low pressure. The study is carried out in argon discharges at 10 mTorr where the sheaths are assumed to be collisionless. The analyzer is mounted flush with the powered electrode surface where the impacting ion and electron energy distributions are measured for a range of discharge powers. A circuit model of the discharge, in combination with analytical solutions for the ion energy distribution in radio-frequency sheaths, is used to calculate other important plasma parameters from the measured energy distributions. Radio-frequency compensated Langmuir probe measurements provide a comparison with the retarding field analyzer data. The time-resolved capability of the retarding field analyzer is also demonstrated in a separate pulsed dc magnetron reactor. The analyzer is mounted on the floating substrate holder and ion energy distributions of the impinging ions on a growing film, with 100 ns time resolution, are measured through a pulse period of applied magnetron power, which are crucial for the control of the microstructure and properties of the deposited films
Unsettling sustainability: the poetics of discomfort
peerreview_statement: The publishing and review policy for this title is described in its Aims & Scope. aims_and_scope_url: http://www.tandfonline.com/action/journalInformation?show=aimsScope&journalCode=rgrl2
Thermal instability in ionized plasma
We study magnetothermal instability in the ionized plasmas including the
effects of Ohmic, ambipolar and Hall diffusion. Magnetic field in the single
fluid approximation does not allow transverse thermal condensations, however,
non-ideal effects highly diminish the stabilizing role of the magnetic field in
thermally unstable plasmas. Therefore, enhanced growth rate of thermal
condensation modes in the presence of the diffusion mechanisms speed up the
rate of structure formation.Comment: Accepted for publication in Astrophysics & Space Scienc
Creativity and Autonomy in Swarm Intelligence Systems
This work introduces two swarm intelligence algorithms -- one mimicking the behaviour of one species of ants (\emph{Leptothorax acervorum}) foraging (a `Stochastic Diffusion Search', SDS) and the other algorithm mimicking the behaviour of birds flocking (a `Particle Swarm Optimiser', PSO) -- and outlines a novel integration strategy exploiting the local search properties of the PSO with global SDS behaviour. The resulting hybrid algorithm is used to sketch novel drawings of an input image, exploliting an artistic tension between the local behaviour of the `birds flocking' - as they seek to follow the input sketch - and the global behaviour of the `ants foraging' - as they seek to encourage the flock to explore novel regions of the canvas. The paper concludes by exploring the putative `creativity' of this hybrid swarm system in the philosophical light of the `rhizome' and Deleuze's well known `Orchid and Wasp' metaphor
Quantitative analysis of powder mixtures by raman spectrometry : the influence of particle size and its correction
Particle size distribution and compactness have significant confounding effects on Raman signals of powder mixtures, which cannot be effectively modeled or corrected by traditional multivariate linear calibration methods such as partial least-squares (PLS), and therefore greatly deteriorate the predictive abilities of Raman calibration models for powder mixtures. The ability to obtain directly quantitative information from Raman signals of powder mixtures with varying particle size distribution and compactness is, therefore, of considerable interest In this study, an advanced quantitative Raman calibration model was developed to explicitly account for the confounding effects of particle size distribution and compactness on Raman signals of powder mixtures. Under the theoretical guidance of the proposed Raman calibration model, an advanced dual calibration strategy was adopted to separate the Raman contributions caused by the changes in mass fractions of the constituents in powder mixtures from those induced by the variations in the physical properties of samples, and hence achieve accurate quantitative determination for powder mixture samples. The proposed Raman calibration model was applied to the quantitative analysis of backscatter Raman measurements of a proof-of-concept model system of powder mixtures consisting of barium nitrate and potassium chromate. The average relative prediction error of prediction obtained by the proposed Raman calibration model was less than one-third of the corresponding value of the best performing PLS model for mass fractions of barium nitrate in powder mixtures with variations in particle size distribution, as well as compactness
The Kelvin-Helmholtz instability in weakly ionised plasmas: Ambipolar dominated and Hall dominated flows
The Kelvin-Helmholtz instability is well known to be capable of converting
well-ordered flows into more disordered, even turbulent, flows. As such it
could represent a path by which the energy in, for example, bowshocks from
stellar jets could be converted into turbulent energy thereby driving molecular
cloud turbulence. We present the results of a suite of fully multifluid
magnetohydrodynamic simulations of this instability using the HYDRA code. We
investigate the behaviour of the instability in a Hall dominated and an
ambipolar diffusion dominated plasma as might be expected in certain regions of
accretion disks and molecular clouds respectively.
We find that, while the linear growth rates of the instability are unaffected
by multifluid effects, the non-linear behaviour is remarkably different with
ambipolar diffusion removing large quantities of magnetic energy while the Hall
effect, if strong enough, introduces a dynamo effect which leads to continuing
strong growth of the magnetic field well into the non-linear regime and a lack
of true saturation of the instability.Comment: 12 pages, 20 figures. Accepted for publication in MNRA
The transformative potential of reflective diaries for elite English cricketers
The sport of cricket has a history of its players suffering from mental health issues. The psychological study of cricket and, in particular, the attendant demands of participating at an elite level has not previously received rigorous academic attention. This study explored ten elite male cricketers’ experiences of keeping a daily reflective diary for one month during the competitive season. The aim was to assess how valuable qualitative diaries are in this field. Participants were interviewed regarding their appraisal of the methodology as a self‐help tool that could assist coping with performance pressures and wider life challenges. Three outcomes were revealed: first, that diary keeping was an effective opportunity to reflect upon the past and enhance one’s self (both as an individual and a performer); second, that diary keeping acted as a form of release that allowed participants to progress; and third, that diary keeping allowed participants to discover personal patterns of success that increased the likeliness of optimum performance
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