1,659 research outputs found
Hawaii's Marine Fisheries: Some History, Long-term Trends, and Recent Developments
This paper provides an overview of Hawaii's marine fisheries from 1948 to the present. After three decades of decline following a brief period of growth at the conclusion to World War lI, Hawaii's commercial fisheries began a decade of sustained development in the 1980's. At the same time, fisheries management issues became more significant as different segments of the fishery came into more direct competition. This paper provides new estimates of commercial landings for the 1977-90 period, and summarizes limited information on recreational and subsistence fisheries in the 1980's. It also provides some historical context which may be useful in evaluating fishery development and management options
Economics and Hawaii's Marine Fisheries
This paper reviews economic research conducted on Hawaii's marine fisheries over the past ten years. The fisheries development and fisheries management context for this research is also considered. The paper finds that new approaches are required for marine fisheries research in Hawaii: A wider scope to include other marine resource and coastal zone issues, and increased and closer collaboration between researchers and the fishing community
GRS 1915+105 : Flares, QPOs and other events at 15 GHz
Monitoring with the Ryle Telescope at 15 GHz of the Galactic X-ray transient
source GRS 1915+105 has revealed a remarkable range of rapid and extended
flares which appear to be related to the X-ray emission as recorded by the RXTE
all-sky monitor. Quasi-periodic oscillations in the range 20 - 40 min have been
found and are probably related to oscillations in the soft X-ray flux.Comment: 2 pages. To be published in Proc. IAU164 : Radio emission from
Galactic and Extragalactic Compact Sources (Socorro, 1997
The orbital modulation in the radio emission of Cygnus X-1
We present model lightcurves which have been created in order to explain the
orbital modulation observed in the radio emission of Cyg X-1. We invoke
variable absorption by the stellar wind as the black hole jet orbits around the
OB companion star and find that a very simple model is able to reproduce the
amplitudes and frequency dependence of the observed lightcurves.Comment: Accepted for publication in MNRA
Orbital modulation and longer-term variability in the radio emission from Cygnus X-1
20 months of observations of the radio emission at 15 GHz from Cygnus X-1,
starting in 1996 October, show variations at the binary period of 5.6 days, but
with a phase offset from those at X-ray wavelengths. There are also longer-term
variations on a time-scale of 150 days which are only loosely related to the
soft X-ray flux. The source was in the hard/low X-ray state throughout this
period. The mean 15-GHz flux density is 13 mJy, the radio spectrum is flat, and
the semi-amplitude of the orbital modulation about 2 mJy. We discuss the
possible origins of the modulation and the relationship to the soft X-ray
emission.Comment: Accepted for publication in MNRA
On the correlation between radio and X-ray flux in Low/Hard state Black Holes
Radio emission from X-ray binary systems (XRBs) has developed in recent years
from being peculiar phenomenon to being recognised as an ubiquitous property of
several classes of XRBs. In this scenario the synchrotron emission is
interpreted as the radiative signature of jet-like outflows, some or all of
which may possess relativistic bulk motion. We have analysed a collection of
quasi-simultaneous radio/X-ray observations of Black Holes in the Low/Hard
X-ray state, finding evidence of a clear correlation between their fluxes over
many orders of magnitude in luminosity. Given that the correlation extends down
to GX 339-4 and V404 Cyg in quiescence, we can confidently assert that even at
accretion rates as low as ~ 10^{-5} dot{m}_{Edd} a powerful jet is being
formed. The normalisation of the correlation is very similar across a sample of
nine sources, implying that it is nearly independent of jet inclination angle.
Remarkably, V 404 Cyg is the second source (after GX 339-4) to show the
correlation S_{radio} proportional to S_{X}^{+0.7} from quiescent level up to
close to the High/Soft state transition. Moreover, assuming the same physics
and accretion:outflow coupling for all of these systems, the simplest
interpretation for the observed scenario is that outflows in Low/Hard state do
not have large bulk Lorentz factors.Comment: 4 pages, 3 figures, Proceedings of the 4th Microquasar Workshop, eds.
Ph Durouchoux, Y. Fuchs and J. Rodriguez, published by the Center for Space
Physics: Kolkat
Infrared spectroscopic variability of Cygnus X-3 in outburst and quiescence
We present four epochs of high-resolution infrared spectroscopy of the
peculiar X-ray binary Cygnus X-3. The observations cover quiescent, small
flaring and outburst states of the system as defined by radio and X-ray
monitoring. The underlying infrared spectrum of the source, as observed during
radio and X-ray quiescence and small flaring states, is one of broad, weak HeII
and NV emission. Spectral variability in this state is dominated by modulation
at the 4.8 hr orbital period of the system. H-band spectra confirm the
significant hydrogen depletion of the mass donor. The closest spectral match to
the quiescent infrared spectrum of Cyg X-3 is an early-type WN Wolf-Rayet star.
In outburst, the infrared spectrum is dramatically different, with the
appearance of very strong twin-peaked HeI emission displaying both day-to-day
variability and V(iolet)/R(ed) variations with orbital phase. The most likely
explanation appears to be an enhanced stellar wind from the companion. Thus
X-ray and radio outbursts in this system are likely to originate in
mass-transfer, and not disc, instabilities, and the lengthening of the orbital
period will not be smooth but will be accelerated during these outbursts.
Furthermore, the appearance of these lines is suggestive of an asymmetric
emitting region. We propose that the wind in Cyg X-3 is significantly flattened
in the plane of the binary orbit. This may explain the observed twin-peaked HeI
features as well as reconciling a massive Wolf-Rayet secondary with the
relatively small optical depth to X-rays, if the disc wind is inclined at some
angle to the line of sight.Comment: 13 pages, 7 figures. Accepted for publication in MNRA
Maternal inbreeding reduces parental care in the zebra finch, <i>Taeniopygia guttata</i>
Increased embryo mortality is the most commonly cited cause of reduced fitness in inbred organisms. Reduced embryo survival may be the result of reduced parental expenditure by inbred individuals and here we tested the hypothesis that inbreeding results in impaired incubation behaviour in captive zebra finches. We compared incubation attentiveness of inbred female zebra finches (derived from full-sibling mating) with that of control females (derived from unrelated parents) and found a statistically significant inbreeding depression of 17% in incubation attentiveness. This shows that inbreeding can significantly influence parental behaviour. Despite a reduction in the amount of time inbred females spent incubating, their partners were able to compensate for the reduced incubation attentiveness. Incubation temperature also did not differ between inbred and control females. To test for the effect of incubation behaviour, we fostered eggs laid by control females to either inbred or control females at the end of laying. Eggs that were incubated by inbred females had an 8.5% lower hatching success than eggs incubated by control females and, although based on a relatively small sample and not statistically significant, the magnitude of the difference was consistent with differences in hatching success observed in the wild under relatively benign environmental conditions. Thus, under more challenging environmental conditions usually encountered in the wild, the reduced incubation attentiveness of inbred females could provide one proximate explanation for the consistent finding of decreased hatching success with increasing maternal inbreeding in birds
REGIONAL ECONOMIC IMPACTS OF REDUCTIONS IN FISHERIES PRODUCTION: A SUPPLY-DRIVEN APPROACH
Much debate and subsequent confusion have recently been generated regarding the economic importance of the longline fisheries for tuna and swordfish in Hawaii. Depending on the methodology employed, the measures of the economic importance of these fisheries to Hawaii can vary significantly. This paper attempts to provide an assessment of the alternative measures and their implications for fishery policy. In assessing the economic impact of the reduction in longline activities due to season and area closures as mandated by a recent court order, we suggest that the supply-driven approach is more appropriate. An empirical application using the supply-driven approach is used to estimate the economy-wide impacts of a 100% reduction in Hawaii-based longline activities. In addition, a set of supply-driven multipliers is derived for the other sectors of Hawaii's economy to allow comparison with the fishery sectors.Resource /Energy Economics and Policy,
The radio/X-ray correlation in Cyg X-3 and the nature of its hard spectral state
We study the radio/X-ray correlation in Cyg X-3. It has been known that the
soft and hard X-ray fluxes in the hard spectral state are correlated positively
and negatively, respectively, with the radio flux. We show that this implies
that the observed 1--100 keV flux (which is a fair approximation to the
bolometric flux) is completely uncorrelated with the radio flux. We can recover
a positive correlation (seen in other sources and expected theoretically) if
the soft X-rays are strongly absorbed by a local medium. Then, however, the
intrinsic X-ray spectrum of Cyg X-3 in its hard state becomes relatively soft,
similar to that of an intermediate spectral state of black-hole binaries, but
not to their true hard state. We also find the radio spectra in the hard state
of Cyg X-3 are hard on average, and the flux distributions of the radio
emission and soft X-rays can be described by sums of two log-normal functions.
We compare Cyg X-3 with other X-ray binaries using colour-colour,
colour-Eddington ratio and Eddington ratio-radio flux diagrams. We find Cyg X-3
to be spectrally most similar to GRS 1915+105, except that Cyg X-3 is
substantially more radio loud, which appears to be due to its jet emission
enhanced by interaction with the powerful stellar wind from the Wolf-Rayet
donor.Comment: An error in the BAT light curve shown in Fig. A2 corrected. Published
in MNRAS + erratu
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