9,566 research outputs found
Fisheries Management: The Kuwaiti Experience
Siddeek et al. (1991) discussed very briefly some recent developments in Kuwait's shrimp fishery, including an important increase in landings of the main commercial species, Penaeus semisulcatus. This increase coincided with a marked fall in landings of the other important species, Metapenaeus affinis. They thought that these changes were caused by a reduction in effort combined with a more or less simultaneous favorable environmental change for P. semisulcatus and an unfavorable environmental change for M. affinis, but did not give any unequivocal evidence to support this conclusion. The results they reported are, nevertheless, very important and may be relevant to scientists and managers in other parts of the world
Vector boson production in association with KK modes of the ADD model to NLO in QCD at LHC
Next-to-leading order QCD corrections to the associated production of vector
boson (Z/W) with the the Kaluza-Klein modes of the graviton in large extra
dimensional model at the LHC, are presented. We have obtained various kinematic
distributions using a Monte Carlo code which is based on the two cut off phase
space slicing method that handles soft and collinear singularities appearing at
NLO level. We estimate the impact of the QCD corrections on various observables
and find that they are significant. We also show the reduction in factorization
scale uncertainty when QCD corrections are included.Comment: 12 pages, 5 figure
Interference detection and correction applied to incoherent-scatter radar power spectrum measurement
A median filter based interference detection and correction technique is evaluated and the method applied to the Arecibo incoherent scatter radar D-region ionospheric power spectrum is discussed. The method can be extended to other kinds of data when the statistics involved in the process are still valid
870 micron Imaging of a Transitional Disk in Upper Scorpius: Holdover from the Era of Giant Planet Formation?
We present 880 micron images of the transition disk around the star [PZ99]
J160421.7-213028, a solar-mass star in the nearby Upper Scorpius association.
With a resolution down to 0.34 arcsec, we resolve the inner hole in this disk,
and via model fitting to the visibilities and spectral energy distribution we
determine both the structure of the outer region and the presence of sparse
dust within the cavity. The disk contains about 0.1 Jupiter masses of
mm-emitting grains, with an inner disk edge of about 70 AU. The inner cavity
contains a small amount of dust with a depleted surface density in a region
extending from about 20-70 AU. Taking into account prior observations
indicating little to no stellar accretion, the lack of a binary companion, and
the presence of dust near 0.1 AU, we determine that the most likely mechanism
for the formation of this inner hole is the presence of one or more giant
planets.Comment: 12 pages, 7 figures. To appear in the Astrophysical Journa
Usefulness of multifrequency MST radar measurements, part 2.6B
Scattering of radio waves from atmospheric refractive-index irregularities induced by turbulence was invoked almost four decades ago to explain the characteristics of signals received on VHF/UHF ionospheric and tropospheric forward-scatter links. Due to the bistatic geometry of these links a slender, horizontally extended, common volume or cell is formed in space. The principal contribution to scattering arises from refractive-index fluctuations in this volume at the Bragg wave number K approx. sub B = K approx. sub i -k approx. sub s vectors. It has been surmised that the use of more than one frequency in probing the middle-atmosphere regions should help resolve several issues pertaining to the scattering mechanism. These issues are briefly re-examined in this note. The implications of the radar equation are discussed. The problems arising due to layered structure of turbulence and the choice of frequencies most suitable for multifrequency measurements are considered
A Quantum Quasi-Harmonic Nonlinear Oscillator with an Isotonic Term
The properties of a nonlinear oscillator with an additional term ,
characterizing the isotonic oscillator, are studied. The nonlinearity affects
to both the kinetic term and the potential and combines two nonlinearities
associated to two parameters, and , in such a way that for
all the characteristics of of the standard isotonic system are
recovered. The first part is devoted to the classical system and the second
part to the quantum system. This is a problem of quantization of a system with
position-dependent mass of the form , with a
-dependent non-polynomial rational potential and with an additional
isotonic term. The Schr\"odinger equation is exactly solved and the
-dependent wave functions and bound state energies are explicitly
obtained for both .Comment: two figure
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