25,378 research outputs found
Detection of the Horizontal Divergent Flow prior to the Solar Flux Emergence
It is widely accepted that solar active regions including sunspots are formed
by the emerging magnetic flux from the deep convection zone. In previous
numerical simulations, we found that the horizontal divergent flow (HDF) occurs
before the flux emergence at the photospheric height. This Paper reports the
HDF detection prior to the flux emergence of NOAA AR 11081, which is located
away from the disk center. We use SDO/HMI data to study the temporal changes of
the Doppler and magnetic patterns from those of the reference quiet Sun. As a
result, the HDF appearance is found to come before the flux emergence by about
100 minutes. Also, the horizontal speed of the HDF during this time gap is
estimated to be 0.6 to 1.5 km s^-1, up to 2.3 km s^-1. The HDF is caused by the
plasma escaping horizontally from the rising magnetic flux. And the interval
between the HDF and the flux emergence may reflect the latency during which the
magnetic flux beneath the solar surface is waiting for the instability onset to
the further emergence. Moreover, SMART Halpha images show that the
chromospheric plages appear about 14 min later, located co-spatial with the
photospheric pores. This indicates that the plages are caused by plasma flowing
down along the magnetic fields that connect the pores at their footpoints. One
importance of observing the HDF may be the possibility to predict the sunspot
appearances that occur in several hours.Comment: 32 pages, 8 figures, 3 tables, accepted for publication in Ap
Fast transform decoding of nonsystematic Reed-Solomon codes
A Reed-Solomon (RS) code is considered to be a special case of a redundant residue polynomial (RRP) code, and a fast transform decoding algorithm to correct both errors and erasures is presented. This decoding scheme is an improvement of the decoding algorithm for the RRP code suggested by Shiozaki and Nishida, and can be realized readily on very large scale integration chips
Long-term morbidity from severe pneumonia in early childhood in The Gambia, West Africa: a follow-up study
OBJECTIVE: To assess long-term outcomes in severe early childhood pneumonia in The Gambia. DESIGN: Observational cohort study of children hospitalised with severe pneumonia between 1992 and 1 04 compared to age, sex, and neigh bourhood-marched controls on measures of current general and pulmonary health. RESULTS: Of 83 children successfully traced, 68 of the 69 alive at follow-up agreed to participate. Thirteen per Cent of cases and 4% of controls had lung disease clinically or on spirometry. Another 16 (13%) participants had abnormal spirometry but did not meet the American Thoracic Society technical criteria (formally 'inconclusive'). Odds ratios of lung disease among childhood pneumonia cases were 2.93 (95 %CI 0.69-12.48, P = 0.1468) with incon-clusives omitted; 2.53 (95 %CI 0.61-10.59, P = 0.2033) with inconclusives included as normal; and 2.83 (95%CI 1.09-7.36, P = 0.0334) with inconclusives included as lung disease. Among deceased cases, most deaths were reported within weeks of discharge, suggesting a possible connection between admission and subsequent death. CONCLUSION: These African data, while not conclusive, add to previous data suggesting a link between severe early, childhood pneumonia and later chronic lung disease. While larger-scale research is needed, increased awareness of possible long-term morbidity in children with severe pneumonia is warranted to limit its impact and optimise long-term health
Moduli Stabilization with Long Winding Strings
Stabilizing all of the modulus fields coming from compactifications of string
theory on internal manifolds is one of the outstanding challenges for string
cosmology. Here, in a simple example of toroidal compactification, we study the
dynamics of the moduli fields corresponding to the size and shape of the torus
along with the ambient flux and long strings winding both internal directions.
It is known that a string gas containing states with non-vanishing winding and
momentum number in one internal direction can stabilize the radius of this
internal circle to be at self-dual radius. We show that a gas of long strings
winding all internal directions can stabilize all moduli, except the dilaton
which is stabilized by hand, in this simple example.Comment: title changed, improved presentation; reference added. 18 pages, JHEP
styl
Unparticle Physics in the Moller Scattering
We investigate the virtual effects of vector unparticles in the Moller
scattering. We derive the analytic expression for scattering amplitudes with
unpolarized beams. We obtain 95% confidence level limits on the unparticle
couplings and with integrated luminosity of
and and 500 GeV energies. We show
that limits on are more sensitive than .Comment: 10 pages, 5 figures, 4 table
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
The spectroscopic evolution of the -ray emitting classical nova Nova Mon 2012. I. Implications for the ONe subclass of classical novae
Nova Mon 2012 was the first classical nova to be detected as a high energy
-ray transient, by Fermi-LAT, before its optical discovery. We study a
time sequence of high resolution optical echelle spectra (Nordic Optical
Telescope) and contemporaneous NOT, STIS UV, and CHIRON echelle spectra (Nov
20/21/22). We use [O III] and H line fluxs to constrain the properties
of the ejecta. We derive the structure from the optical and UV line profiles
and compare our measured line fluxes for with predictions using Cloudy with
abundances from other ONe novae. Mon 2012 is confirmed as an ONe nova. We find
E(B-V)=0.850.05 and hydrogen column density
cm. The corrected continuum luminosity is nearly the same in the entire
observed energy range as V1974 Cyg, V382 Mon, and Nova LMC 2000 at the same
epoch after outburst. The distance, about 3.6 kpc, is quite similar to V1974
Cyg. The line profiles can be modeled using an axisymmetric bipolar geometry
for the ejecta with various inclinations of the axis to the line of sight, 60
\le i \le 80 degrees, an opening angle of \approx\Delta
R/R(t)\approx 0.4f\approx 0.1-0.3\leq 6\times
10^{-5}_\odot\gamma$-ray emission may be a generic phenomenon, common to all ONe novae,
possibly to all classical novae, and connected with acceleration and emission
processes within the ejecta (abstract severely truncated).Comment: Submitted to A&A 9/1/2013; Accepted 27/2/2013 (in press
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