2,767 research outputs found
Photon redshift and the appearance of a naked singularity
In this paper we analyze the redshift as observed by an external observer
receiving photons which terminate in the past at the naked singularity formed
in a Tolman-Bondi dust collapse. Within the context of models considered here
it is shown that photons emitted from a weak curvature naked singularity are
always finitely redshifted to an external observer. Certain cases of strong
curvature naked singularities, including the self-similar one, where the
photons are infinitely redshifted are also pointed out.Comment: Latex file, 14 pages, no figures, one change in the reference.
Accepted for publication in Phys. Rev.
Examining the socio-economic determinants of adoption of the 'Government Gateway' initiative in the UK
This paper empirically examines the impact of socio-economic determinants upon the adoption of a recent UK e-government initiative, the 'Government Gateway'. The data on five socio-economic characteristics was collected employing a postal survey. The findings of this research suggest that the three variables of age, gender and occupation significantly differentiated the adopters from the non-adopters of the Government Gateway, whilst education and income were found to be non-significant. The implications of the findings are discussed in the context of promoting the adoption of emerging Information and Communication Technologies (ICT) and reducing the digital divide against less privileged parts of the population
On Thermal-Pulse-Driven Plasma Flows in Coronal Funnels as Observed by Hinode/EUV Imaging Spectrometer (EIS)
Using one-arcsecond-slit scan observations from the Hinode/EUV Imaging
Spectrometer (EIS) on 05 February 2007, we find the plasma outflows in the open
and expanding coronal funnels at the eastern boundary of AR 10940. The Doppler
velocity map of Fe XII 195.120 A shows that the diffuse close-loop system to be
mostly red-shifted. The open arches (funnels) at the eastern boundary of AR
exhibit blue-shifts with a maximum speed of about 10-15 km/s. This implies
outflowing plasma through these magnetic structures. In support of these
observations, we perform a 2D numerical simulation of the expanding coronal
funnels by solving the set of ideal MHD equations in appropriate VAL-III C
initial temperature conditions using the FLASH code. We implement a rarefied
and hotter region at the footpoint of the model funnel, which results in the
evolution of slow plasma perturbations propagating outward in the form of
plasma flows. We conclude that the heating, which may result from magnetic
reconnection, can trigger the observed plasma outflows in such coronal funnels.
This can transport mass into the higher corona, giving rise to the formation of
the nascent solar wind.Comment: 17 Pages; 7 Figure
Spectroscopic Observations and Modelling of Impulsive Alfv\'en Waves Along a Polar Coronal Jet
Using the Hinode/EIS 2 spectroscopic observations, we study the intensity,
velocity, and FWHM variations of the strongest Fe XII 195.12 \AA\ line along
the jet to find the signature of Alfv\'en waves. We simulate numerically the
impulsively generated Alfv\'en waves within the vertical Harris current-sheet,
forming the jet plasma flows, and mimicking their observational signatures.
Using the FLASH code and the atmospheric model with embedded weakly expanding
magnetic field configuration within a vertical Harris current-sheet, we solve
the two and half-dimensional (2.5-D) ideal magnetohydrodynamic (MHD) equations
to study the evolution of Alfv\'en waves and vertical flows forming the plasma
jet. At a height of from the base of the jet, the
red-shifted velocity component of Fe XII 195.12 \AA\ line attains its maximum
() which converts into a blue-shifted one between the
altitude of . The spectral intensity continously increases up
to , while FWHM still exhibits the low values with almost
constant trend. This indicates that the reconnection point within the jet's
magnetic field topology lies in the corona from its
footpoint anchored in the Sun's surface. Beyond this height, FWHM shows a
growing trend. This may be the signature of Alfv\'en waves that impulsively
evolve due to reconnection and propagate along the jet. From our numerical
data, we evaluate space- and time- averaged Alfv\'en waves velocity amplitudes
at different heights in the jet's current-sheet, which contribute to the
non-thermal motions and spectral line broadening. The synthetic width of Fe XII
line exhibits similar trend of increment as in the
observational data, possibly proving the existence of impulsively generated (by
reconnection) Alfv\'en waves which propagate along the jet
Oyster mushroom waste as manure in fish culture: a preliminary study
In an attempt to recycle the waste substrates of the oyster-mushroom crop, tanks were stocked with seed of Indian major carp Cirrhinus mrigala at the rate of 600,000/ha and waste substrate was applied at weekly interval at 0, 50, 100, 150, 200 and 250 g/tank. Oyster mushroom waste not only provided highly nutritive colonised detritus to the fish as direct feed, but also produced rich plankton in the tank. In waste treated tanks, production was better than in the control in 150, 200 and 250 g/tank treatment suggesting the possibility of fish-oyster mushroom integration
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