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Hereditariness, strongness and relationship between Brown-McCoy and Behrens radicals
In this paper we explore the properties of being hereditary and being strong among the radicals of associative rings, and prove certain results such as a relationship between Brown-McCoy and Behrens radicals
BeppoSAX-WFC monitoring of the Galactic Center region
We review the results obtained with the Galactic center campaigns of the
BeppoSAX Wide Field X-ray Cameras (WFCs). This pertains to the study of
luminous low-mass X-ray binaries (LMXBs). When pointed at the Galactic center,
the WFC field of view contains more than half of the Galactic LMXB population.
The results exemplify the excellent WFC capability to detect brief X-ray
transients. Firstly, the WFCs expanded the known population of Galactic
thermonuclear X-ray bursters by 50%. At least half of all LMXBs are now
established to burst and, thus, to contain a neutron star as compact accretor
rather than a black hole candidate. We provide a complete list of all 76
currently known bursters, including the new case 1RXS J170854.4-321857.
Secondly, the WFCs have uncovered a population of weak transients with peak
luminosities up to ~10^37 erg/s and durations from days to weeks. One is the
first accretion-powered millisecond pulsar SAX J1808.4-3658. Thirdly, the WFCs
contributed considerably towards establishing that nearly all (12 out of 13)
luminous low-mass X-ray binaries in Galactic globular clusters contain neutron
stars rather than black holes. Thus, the neutron star to black hole ratio in
clusters differs from that in the Galactic disk at a marginal confidence level
of 97%.Comment: 10 pages 6 figures, to appear in Proc. "The Restless High-Energy
Universe" (2nd BeppoSAX Symposium), eds. E.P.J. van den Heuvel, J.J.M. in 't
Zand & R.A.M.J. Wijers, Nucl. Instrum. Meth. B Suppl. Se
Discretization effects of digital control of thermally tunable 2x2 MZI couplers
We describe how digital voltage driving of tunable 2×2 Mach-Zehnder couplers with thermo-optic phase shifters introduces discretization errors which significantly affect programmable photonic circuits. Performing quantitative analysis, we show that proper biasing of couplers and simultaneous driving of arms can improve discretization errors
PRODUCERS PRICES FOR OLIVES AND OLIVE OIL IN TUNISIA
Demand and Price Analysis,
THE ECONOMICS OF OLIVE OIL AND OILSEEDS IN THE MEDITERRANEAN REGION
Crop Production/Industries,
Relativistic outflow from two thermonuclear shell flashes on neutron stars
We study the exceptionally short (32-41 ms) precursors of two
intermediate-duration thermonuclear X-ray bursts observed with RXTE from the
neutron stars in 4U 0614+09 and 2S 0918-549. They exhibit photon fluxes that
surpass those at the Eddington limit later in the burst by factors of 2.6 to
3.1. We are able to explain both the short duration and the super-Eddington
flux by mildly relativistic outflow velocities of 0.1 to 0.3 subsequent
to the thermonuclear shell flashes on the neutron stars. These are the highest
velocities ever measured from any thermonuclear flash. The precursor rise times
are also exceptionally short: about 1 ms. This is inconsistent with predictions
for nuclear flames spreading laterally as deflagrations and suggests
detonations instead. This is the first time that a detonation is suggested for
such a shallow ignition column depth ( = 10 g cm).
The detonation would possibly require a faster nuclear reaction chain, such as
bypassing the alpha-capture on C with the much faster
C(p,)N(,p)O process previously proposed.
We confirm the possibility of a detonation, albeit only in the radial
direction, through the simulation of the nuclear burning with a large nuclear
network and at the appropriate ignition depth, although it remains to be seen
whether the Zel'dovich criterion is met. A detonation would also provide the
fast flame spreading over the surface of the neutron star to allow for the
short rise times. (...) As an alternative to the detonation scenario, we
speculate on the possibility that the whole neutron star surface burns almost
instantly in the auto-ignition regime. This is motivated by the presence of 150
ms precursors with 30 ms rise times in some superexpansion bursts from 4U
1820-30 at low ignition column depths of ~10 g cm.Comment: 11 pages, 6 figures, accepted by Astronomy and Astrophysic
On the relevance of q-distribution functions: The return time distribution of restricted random walker
There exist a large literature on the application of -statistics to the
out-of-equilibrium non-ergodic systems in which some degree of strong
correlations exists. Here we study the distribution of first return times to
zero, , of a random walk on the set of integers
with a position dependent transition probability given by . We find
that for all values of can be fitted by
-exponentials, but only for is given exactly by a
-exponential in the limit . This is a remarkable result
since the exact analytical solution of the corresponding continuum model
represents as a sum of Bessel functions with a smooth dependence on
from which we are unable to identify as of special significance.
However, from the high precision numerical iteration of the discrete Master
Equation, we do verify that only for is exactly a
-exponential and that a tiny departure from this parameter value makes the
distribution deviate from -exponential. Further research is certainly
required to identify the reason for this result and also the applicability of
-statistics and its domain.Comment: 14 pages, 3 figures. The replacement correct that two papers in the
reference list were not mentioned in the tex
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