391 research outputs found
Source identities and kernel functions for deformed (quantum) Ruijsenaars models
We consider the relativistic generalization of the quantum
Calogero-Sutherland models due to Ruijsenaars, comprising the rational,
hyperbolic, trigonometric and elliptic cases. For each of these cases, we find
an exact common eigenfunction for a generalization of Ruijsenaars analytic
difference operators that gives, as special cases, many different kernel
functions; in particular, we find kernel functions for Chalykh-
Feigin-Veselov-Sergeev-type deformations of such difference operators which
generalize known kernel functions for the Ruijsenaars models. We also discuss
possible applications of our results.Comment: 24 page
The 4-beaches survey in Uganda: Nkombe Beach
This paper analyses the location, potentialities and set-backs of Nkombe Beach, the landing site chosen in Uganda for the 4-beaches survey
The Jinja Stakeholders' Workshop, February 21st -23rd, 2001
This book section is a review of a workshop, the one held at Jinja in Uganda, which aimed to assess the potential local stakeholders within the frame of the co-management of Lake Victoria's fisheries
A Rapid X-ray Flare from Markarian 501
We present X-ray observations of the BL Lacertae (BL Lac) object Markarian
501 (Mrk 501), taken with the Rossi X-ray Timing Explorer in 1998 May as part
of a multi-wavelength campaign. The X-ray light curve shows a very rapid flare
in which the 2-10 keV flux increased by ~60% in <200 seconds. This rapid rise
is followed by a drop-off in the 2-10 keV flux of ~40% in <600 seconds. The
10-15 keV variation in this flare is roughly a factor of two on similar
time-scales. During the rise of the flare, the 3-15 keV spectral index hardened
from 2.02 +/- 0.03 to 1.87 +/- 0.04, where it remained during the decay of the
flare. This is the fastest variation ever seen in X-rays from Mrk 501 and among
the fastest seen at any wavelength for this object. The shift in the energy at
which the spectral power peaks (from 30 keV during
the flare) is also among the most rapid shifts seen from this object. This
flare occurs during an emission state (2-10 keV flux approximately 1.2e-10 erg
cm^-2 s^-1) that is approximately 25% of the peak flux observed in 1997 April
from this object but which is still high compared to its historical average
X-ray flux. The variations in the hardness ratio are consistent with the low
energy variations leading those at high energies during the development and
decay of the flare. This pattern is rare among high frequency peaked BL Lac
objects like Mrk 501, but has been seen recently in two other TeV emitting BL
Lacs, Mrk 421 and PKS 2155-304. The hard lag is consistent with a flare
dominated by the acceleration time-scale for a simple relativistic shock model
of flaring.Comment: 11 pages, 3 figures, accepted for publication in Astrophys. J.
Letter
Stabilized Kuramoto-Sivashinsky system
A model consisting of a mixed Kuramoto - Sivashinsky - KdV equation, linearly
coupled to an extra linear dissipative equation, is proposed. The model applies
to the description of surface waves on multilayered liquid films. The extra
equation makes its possible to stabilize the zero solution in the model,
opening way to the existence of stable solitary pulses (SPs). Treating the
dissipation and instability-generating gain in the model as small
perturbations, we demonstrate that balance between them selects two
steady-state solitons from their continuous family existing in the absence of
the dissipation and gain. The may be stable, provided that the zero solution is
stable. The prediction is completely confirmed by direct simulations. If the
integration domain is not very large, some pulses are stable even when the zero
background is unstable. Stable bound states of two and three pulses are found
too. The work was supported, in a part, by a joint grant from the Israeli
Minsitry of Science and Technology and Japan Society for Promotion of Science.Comment: A text file in the latex format and 20 eps files with figures.
Physical Review E, in pres
Stability of three-dimensional self-trapped beams with a dark spot surrounded by bright rings of varying intensity
We analytically and numerically examine the stability of three-dimensional self-trapped beams with a dark spot surrounded by bright rings of varying intensity in a uniform saturable self-focusing medium. It is shown that the fundamental bound state of the family is stable to a symmetric perturbation but unstable to an asymmetric perturbation (that breaks the azimuthal symmetry of the beam, i.e., transverse instabilities). The higher-order states are also found to display transverse (modulation) instabilities. The development of the instabilities is shown to lead to the emission of filaments which spiral away from the center of the dark spot as stable entities. © 1994 The American Physical Society.Peer Reviewe
Discovery of new TeV supernova remnant shells in the Galactic plane with H.E.S.S
Supernova remnants (SNRs) are prime candidates for efficient particle
acceleration up to the knee in the cosmic ray particle spectrum. In this work
we present a new method for a systematic search for new TeV-emitting SNR shells
in 2864 hours of H.E.S.S. phase I data used for the H.E.S.S. Galactic Plane
Survey. This new method, which correctly identifies the known shell
morphologies of the TeV SNRs covered by the survey, HESS J1731-347, RX
1713.7-3946, RCW 86, and Vela Junior, reveals also the existence of three new
SNR candidates. All three candidates were extensively studied regarding their
morphological, spectral, and multi-wavelength (MWL) properties. HESS J1534-571
was associated with the radio SNR candidate G323.7-1.0, and thus is classified
as an SNR. HESS J1912+101 and HESS J1614-518, on the other hand, do not have
radio or X-ray counterparts that would permit to identify them firmly as SNRs,
and therefore they remain SNR candidates, discovered first at TeV energies as
such. Further MWL follow up observations are needed to confirm that these newly
discovered SNR candidates are indeed SNRs
Determination of Rheumatoid Factor in Suspected Rheumatoid Arthritis Patients Attending Selected Hospitals in Zaria, Nigeria
The study was carried out to provide information on RF among RA especially in the Northern part of Nigeria is relatively scarce. As such, rheumatoid factor levels in blood could serve as a predictive index for the onset of Rheumatoid arthritis. A total of 182 sera samples were analyse for the presence of IgM rheumatoid factor by ELISA. Seventeen (17) were found to be positive and 165 negative giving a prevalence of 9.3% and 90.7% respectively. The age range of 50 and above had the highest RF positive cases of 4.9%. This is followed by the eighteen (18) to thirty (30) age range. The association was not significant at p-value of 0.05. Similarly, the relationship between RF and gender showed that 5.5% (n=101) of females were positive while than 3.8% (n=81) of males were positive. The association was not significant. The highest participants had tertiary level of education which has a RF prevalence of 4.4%. Most of the participants that tested positive for RF were married (8.2%). There was no significant association between positivity for RF and level of education as well as marital status. There was however no statistical significant association between RF and the signs and symptoms (stiffness of joints, swelling around the joints, general fatigue, muscle pains, fever 13 and joint pains). Out of the 29 patients with history investigated for RA, 4 (2.2%) were positive for RF. Among the participants that smoke cigarette (n=4), none was RF positive. Both factors did not show significant association at a p-value of 0.05. The information in this study would serve as a predictive index for the onset of Rheumatoid arthritis. Keywords: Rheumatoid Arthritis, Rheumatoid Factor, Auto-immune disease, synovial inflammatio
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