5,204 research outputs found
Biology and population dynamics of cowcod (Sebastes levis) in the southern California Bight
Cowcod (Sebastes levis) is a large (100-cm-FL), long-lived (maximum observed age 55 yr) demersal rockfish taken in multispecies commercial and recreational fisheries off
southern and central California. It lives at 20–500 m depth: adults (>44 cm TL) inhabit rocky areas at 90–300 m and juveniles inhabit fine sand and clay at 40–100 m. Both sexes have similar growth and maturity. Both sexes recruit to the fishery before reaching full maturity. Based on age and growth data, the natural mortality rate is about M =0.055/yr, but the estimate is uncertain. Biomass, recruitment, and mortality during 1951–98 were estimated in a delay-difference model with catch data and abundance indices. The same model gave less precise estimates for 1916–50 based on catch data and assumptions about virgin biomass and recruitment such as used in stock reduction analysis. Abundance indices, based on rare event data, included a habitat-area–weighted index of recreational
catch per unit of fishing effort (CPUE index values were 0.003–0.07 fish per angler hour), a standardized
index of proportion of positive tows in CalCOFI ichthyoplankton survey data (binomial errors, 0–13% positive
tows/yr), and proportion of positive tows for juveniles in bottom trawl surveys (binomial errors, 0–30% positive tows/yr). Cowcod are overfished in the southern California Bight; biomass during the 1998 season was about 7% of the virgin level and recent catches have been near 20 metric tons (t)/yr. Projections based on recent recruitment levels indicate that biomass will decline at catch levels > 5 t/yr. Trend data indicate that recruitment will be poor in
the near future. Recreational fishing effort in deep water has increased and has become more effective for catching
cowcod. Areas with relatively high catch rates for cowcod are fewer and are farther offshore. Cowcod die after capture
and cannot be released alive. Two areas recently closed to bottom fishing will help rebuild the cowcod stock
Interaction of CK1δ with γTuSC ensures proper microtubule assembly and spindle positioning.
Casein kinase 1δ (CK1δ) family members associate with microtubule-organizing centers (MTOCs) from yeast to humans, but their mitotic roles and targets have yet to be identified. We show here that budding yeast CK1δ, Hrr25, is a γ-tubulin small complex (γTuSC) binding factor. Moreover, Hrr25's association with γTuSC depends on its kinase activity and its noncatalytic central domain. Loss of Hrr25 kinase activity resulted in assembly of unusually long cytoplasmic microtubules and defects in spindle positioning, consistent with roles in regulation of γTuSC-mediated microtubule nucleation and the Kar9 spindle-positioning pathway, respectively. Hrr25 directly phosphorylated γTuSC proteins in vivo and in vitro, and this phosphorylation promoted γTuSC integrity and activity. Because CK1δ and γTuSC are highly conserved and present at MTOCs in diverse eukaryotes, similar regulatory mechanisms are expected to apply generally in eukaryotes
Photoproduction evidence for and against hidden-strangeness states near 2 GeV
Experimental evidence from coherent diffractive proton scattering has been
reported for two narrow baryonic resonances which decay predominantly to
strange particles. These states, with masses close to 2.0 GeV would, if
confirmed, be candidates for hidden strangeness states with unusual internal
structure. In this paper we examine the literature on strangeness
photoproduction, to seek additional evidence for or against these states. We
find that one state is not confirmed, while for the other state there is some
mild supporting evidence favoring its existence. New experiments are called
for, and the expected photoproduction lineshapes are calculated.Comment: 9 pages, RevTex, five postscript figures, submitted to PR
Effects of neighborhood disadvantage on problem gambling and alcohol abuse
Background and aims:
Based on social disorganization theory, the present study examined the effects of neighborhood disadvantage on gambling behaviors and problems as well as on alcohol use and abuse.
Methods:
Findings were based on a combined sample of two representative U.S. telephone surveys of gambling and substance use. One survey (n = 2,631) included adults 18 years and older and the second survey (2,274) included young people aged 14–21 years old.
Results:
Neighborhood disadvantage had a highly significant effect on problem gambling over and above the significant individual effects of gender, age, race/ethnicity and socioeconomic status. Alcohol abuse did not show the same relationship to neighborhood disadvantage as did problem gambling. Furthermore, when neighborhood disadvantage was high and individual socioeconomic status was low, the highest levels of problem gambling were observed.
Conclusions:
This study provides strong evidence for the effects of neighborhood ecology on the occurrence of problem gambling
The Properties of Poor Groups of Galaxies: III. The Galaxy Luminosity Function
We obtain R-band photometry for galaxies in six nearby poor groups for which
we have spectroscopic data, including 328 new galaxy velocities. For the five
groups with luminous X-ray halos, the composite group galaxy luminosity
function (GLF) is fit adequately by a Schechter function with Mstar = -21.6 +/-
0.4 + 5log h and alpha = -1.3 +/- 0.1. We also find that (1) the ratio of
dwarfs to giants is significantly larger for the five groups with luminous
X-ray halos than for the one marginally X-ray detected group, (2) the composite
GLF for the luminous X-ray groups is consistent in shape with that for rich
clusters, (3) the composite group GLF rises more steeply at the faint end than
that of the field, (4) the shape difference between the field and composite
group GLF's results mostly from the population of non-emission line galaxies,
whose dwarf-to-giant ratio is larger in the denser group environment than in
the field, and (5) the non-emission line dwarfs are more concentrated about the
group center than the non-emission line giants. This last result indicates that
the dwarfs and giants occupy different orbits (i.e., have not mixed completely)
and suggests that the populations formed at a different times. Our results show
that the shape of the GLF varies with environment and that this variation is
due primarily to an increase in the dwarf-to-giant ratio of quiescent galaxies
in higher density regions, at least up to the densities characteristic of X-ray
luminous poor groups. This behavior suggests that, in some environments, dwarfs
are more biased than giants with respect to dark matter. This trend conflicts
with the prediction of standard biased galaxy formation models. (Abridged)Comment: 36 pages, AASLaTeX with 8 figures. Table 1 also available at
http://atropos.as.arizona.edu/aiz/papers/all_grp_lf_ascii.dat.final . To
appear in Ap
Chandra Observations of the Interacting NGC 4410 Galaxy Group
We present high resolution X-ray imaging data from the ACIS-S instrument on
the Chandra telescope of the nearby interacting galaxy group NGC 4410. Four
galaxies in the inner portion of this group are clearly detected by Chandra,
including the peculiar low luminosity radio galaxy NGC 4410A. In addition to a
nuclear point source, NGC 4410A contains diffuse X-ray emission, including an
X-ray ridge extending out to about 12" (6 kpc) to the northwest of the nucleus.
This ridge is coincident with an arc of optical emission-line gas, which has
previously been shown to have optical line ratios consistent with shock
ionization. This structure may be due to an expanding superbubble of hot gas
caused by supernovae and stellar winds or by the active nucleus. The Chandra
observations also show four or five possible compact ultra-luminous X-ray (ULX)
sources (L(x) >= 10^39 erg/s) associated with NGC 4410A. At least one of these
candidate ULXs appears to have a radio counterpart, suggesting that it may be
due to an X-ray binary with a stellar-mass black hole, rather than an
intermediate mass black hole. In addition, a faint diffuse intragroup X-ray
component has been detected between the galaxies (L(x) ~ 10^41 erg/s). This
supports the hypothesis that the NGC 4410 group is in the process of evolving
via mergers from a spiral-dominated group (which typically have no
X-ray-emitting intragroup gas) to an elliptical-dominated group (which often
have a substantial intragroup medium).Comment: 27 pages, 14 figures; Accepted by Astronomical Journal; color images
at http://www.etsu.edu/physics/bsmith/research/n4410.htm
FUSE Observations of a Full Orbit of Hercules X-1: Signatures of Disk, Star, and Wind
We observed an entire 1.7 day orbit of the X-ray binary Hercules X-1 with the
Far Ultraviolet Spectroscopic Explorer (FUSE). Changes in the O VI 1032,1037
line profiles through eclipse ingress and egress indicate a Keplerian accretion
disk spinning prograde with the orbit. These observations may show the first
double-peaked accretion disk line profile to be seen in the Hercules X-1
system. Doppler tomograms of the emission lines show a bright spot offset from
the Roche lobe of the companion star HZ Her, but no obvious signs of the
accretion disk. Simulations show that the bright spot is too far offset from
the Roche lobe to result from uneven X-ray heating of its surface. The absence
of disk signatures in the tomogram can be reproduced in simulations which
include absorption from a stellar wind. We attempt to diagnose the state of the
emitting gas from the C III 977, C III 1175, and N III 991 emission lines. The
latter may be enhanced through Bowen fluorescence.Comment: Accepted for publication in The Astrophysical Journa
Galaxy Mergers with Adaptive Mesh Refinement: Star Formation and Hot Gas Outflow
In hierarchical structure formation, merging of galaxies is frequent and
known to dramatically affect their properties. To comprehend these interactions
high-resolution simulations are indispensable because of the nonlinear coupling
between pc and Mpc scales. To this end, we present the first adaptive mesh
refinement (AMR) simulation of two merging, low mass, initially gas-rich
galaxies (1.8e10 Ms each), including star formation and feedback. With galaxies
resolved by ~2e7 total computational elements, we achieve unprecedented
resolution of the multiphase interstellar medium, finding a widespread
starburst in the merging galaxies via shock-induced star formation. The high
dynamic range of AMR also allows us to follow the interplay between the
galaxies and their embedding medium depicting how galactic outflows and a hot
metal-rich halo form. These results demonstrate that AMR provides a powerful
tool in understanding interacting galaxies.Comment: 4 pages, 5 figures, Accepted for publication in the Astrophysical
Journal Letters, Image resolution greatly reduced, High-resolution version of
this article and movies are available at
http://www.jihoonkim.org/index/research.html#merge
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