9,796 research outputs found
Fauna and flora of the Great Barrier Reef World Heritage Area : a compendium of information and basis for the species conservation program in the Great Barrier Reef Marine Park Authority: second edition
The way in which the Great Barrier Reef Marine Park Authority (GBRMPA) manages for the
conservation of species in the GBRMP is determined mainly by legislative instruments and
policy decisions, which are supported by education and enforcement. Given the migratory
nature of many species, the GBRMPA works closely with other Australian and Queensland
Government agencies to ensure complementary management approaches as far as possible.
This Report is a compendium of information on the fauna and flora of the GBRWHA and
explains the rationale behind the work priorities of the Species Conservation Program of the
GBRMPA, which focuses on the management of threatened species. The Report will be
reviewed and updated as additional information becomes available and in the light of
changes to conservation priorities
Infection levels and species diversity of ascaridoid nematodes in Atlantic cod, Gadus morhua, are correlated with geographic area and fish size
Atlantic cod (Gadus morhua) is among the most important commercial fish species on the world market. Its
infection by ascaridoid nematodes has long been known, Pseudoterranova even being named cod worm. In the
present study, 755 individuals were sampled in the Barents, Baltic and North Seas during 2012–2014.
Prevalences for Anisakis in whole fish and in fillets in the different fishing areas varied from 16 to 100% and
from 12 to 90% respectively. Abundance was also greatly influenced by the sampling area. Generalized additive
model results indicate higher numbers of Anisakis in the North Sea, even after the larger body size was accounted
for. Numbers and prevalence of Anisakis were positively related to fish length or weight. The prevalence of
parasites in whole fish and in fillets was also influenced by the season, with the spring displaying a peak for the
prevalence in whole fish and, at the same time, a drop for the prevalence in fillets. Whereas 46% of cod had
Anisakis larvae in their fillets, the majority (39%) had parasites mainly in the ventral part of the fillet and only
12% had parasites in their dorsal part. This observation is of importance for the processing of the fish. Indeed,
the trimming of the ventral part of the cod fillet would allow the almost total elimination of ascaridoids except
for cod from the Baltic Sea where there was no difference between the dorsal and the ventral part.
The presence of other ascaridoid genera was also noticeable in some areas. For Pseudoterranova, the highest
prevalence (45%) in whole fish was observed in the Northern North Sea, whereas the other areas had prevalences between 3 and 16%. Contracaecum was present in every commercial size cod sampled in the Baltic Sea
with an intensity of up to 96 worms but no Contracaecum was isolated from the Central North Sea. Non-zoonotic
Hysterothylacium was absent from the Baltic Sea but with a prevalence of 83% in the Barents and the Northern
North Sea.
A subsample of worms was identified with genetic-molecular tools and assigned to the species A. simplex (s.s.),
A. pegreffii, P. decipiens (s.s.), P. krabbei, C. osculatum and H. aduncum. In addition to high prevalence and
abundance values, the cod sampled in this study presented a diversity of ascaridoid nematodes with a majority of
fish displaying a co-infection. Out of 295 whole infected fish, 269 were co-infected by at least 2 genera
Implications of Constraints on Mass Parameters in the Higgs Sector of the Nonlinear Supersymmetric SU(5) Model
The Higgs sector of the minimal nonlinear supersymmetric SU(5) model contains
three mass parameters. Although these mass parameters are essentially free at
the electroweak scale, they might have particular values if they evolve from a
particular constraints at the GUT scale through the RG equations. By assuming a
number of simple constraints on these mass parameters at the GUT scale, we
obtain their values at the electroweak scale through the RG equations in order
to investigate the phenomenological implications. Some of them are found to be
consistent with the present experimental data.Comment: 23 pages, 10 figure
Is There a Peccei-Quinn Phase Transition?
The nature of axion cosmology is usually said to depend on whether the
Peccei-Quinn (PQ) symmetry breaks before or after inflation. The PQ symmetry
itself is believed to be an accident, so there is not necessarily a symmetry
during inflation at all. We explore these issues in some simple models, which
provide examples of symmetry breaking before and after inflation, or in which
there is no symmetry during inflation and no phase transition at all. One
effect of these observations is to relax the constraints from isocurvature
fluctuations due to the axion during inflation. We also observe new
possibilities for evading the constraints due to cosmic strings and domain
walls, but they seem less generic.Comment: 14 pages. Several references adde
Quantum Films Adsorbed on Graphite: Third and Fourth Helium Layers
Using a path-integral Monte Carlo method for simulating superfluid quantum
films, we investigate helium layers adsorbed on a substrate consisting of
graphite plus two solid helium layers. Our results for the promotion densities
and the dependence of the superfluid density on coverage are in agreement with
experiment. We can also explain certain features of the measured heat capacity
as a function of temperature and coverage.Comment: 13 pages in the Phys. Rev. two-column format, 16 Figure
A 2dF spectroscopic study of globular clusters in NGC 5128: Probing the formation history of the nearest giant Elliptical
We have performed a spectroscopic study of globular clusters (GCs) in the
giant elliptical NGC 5128 using the 2dF facility at the Anglo-Australian
telescope. We obtained integrated optical spectra for a total of 254 GCs, 79 of
which are newly confirmed on the basis of their radial velocities and spectra.
In addition, we obtained an integrated spectrum of the galaxy starlight along
the southern major axis. We derive an empirical metallicity distribution
function (MDF) for 207 GCs (~14 of the estimated total GC system) based upon
Milky Way GCs. This MDF is multimodal at high statistical significance with
peaks at [Z/H]~-1.3 and -0.5. A comparison between the GC MDF and that of the
stellar halo at 20 kpc (~4 Reff) reveals close coincidence at the metal-rich
ends of the distributions. However, an inner 8 kpc stellar MDF shows a clear
excess of metal-rich stars when compared to the GCs. We compare a higher S/N
subsample (147 GCs) with two stellar population models which include non-solar
abundance ratio corrections. The vast majority of our sample (~90%) appears
old, with ages similar to the Milky Way GC system. There is evidence for a
population of intermediate-age (~4-8 Gy) GCs (<15% of the sample) which are on
average more metal-rich than the old GCs. We also identify at least one younger
cluster (~1-2 Gy) in the central regions of the galaxy. Our observations are
consistent with a picture where NGC 5128 has undergone at least two mergers
and/or interactions involving star formation and limited GC formation since
z=1, however the effect of non-canonical hot stellar populations on the
integrated spectra of GCs remains an outstanding uncertainty in our GC age
estimates.Comment: 17 figures, some long table
Unconventional carrier-mediated ferromagnetism above room temperature in ion-implanted (Ga, Mn)P:C
Ion implantation of Mn ions into hole-doped GaP has been used to induce
ferromagnetic behavior above room temperature for optimized Mn concentrations
near 3 at.%. The magnetism is suppressed when the Mn dose is increased or
decreased away from the 3 at.% value, or when n-type GaP substrates are used.
At low temperatures the saturated moment is on the order of one Bohr magneton,
and the spin wave stiffness inferred from the Bloch-law T^3/2 dependence of the
magnetization provides an estimate Tc = 385K of the Curie temperature that
exceeds the experimental value, Tc = 270K. The presence of ferromagnetic
clusters and hysteresis to temperatures of at least 330K is attributed to
disorder and proximity to a metal-insulating transition.Comment: 4 pages, 4 figures (RevTex4
On the validity of mean-field amplitude equations for counterpropagating wavetrains
We rigorously establish the validity of the equations describing the
evolution of one-dimensional long wavelength modulations of counterpropagating
wavetrains for a hyperbolic model equation, namely the sine-Gordon equation. We
consider both periodic amplitude functions and localized wavepackets. For the
localized case, the wavetrains are completely decoupled at leading order, while
in the periodic case the amplitude equations take the form of mean-field
(nonlocal) Schr\"odinger equations rather than locally coupled partial
differential equations. The origin of this weakened coupling is traced to a
hidden translation symmetry in the linear problem, which is related to the
existence of a characteristic frame traveling at the group velocity of each
wavetrain. It is proved that solutions to the amplitude equations dominate the
dynamics of the governing equations on asymptotically long time scales. While
the details of the discussion are restricted to the class of model equations
having a leading cubic nonlinearity, the results strongly indicate that
mean-field evolution equations are generic for bimodal disturbances in
dispersive systems with \O(1) group velocity.Comment: 16 pages, uuencoded, tar-compressed Postscript fil
The role of AGN in the colour transformation of galaxies at redshifts z~1
We explore the role of AGN in establishing and/or maintaining the bimodal
colour distribution of galaxies by quenching their star-formation and hence,
causing their transition from the blue to the red cloud. Important tests for
this scenario include (i) the X-ray properties of galaxies in the transition
zone between the two clouds and (ii) the incidence of AGN in post-starbursts,
i.e. systems observed shortly after (<1Gyr) the termination of their
star-formation. We perform these tests by combining deep Chandra observations
with multiwavelength data from the AEGIS survey. Stacking the X-ray photons at
the positions of galaxies (0.4<z<0.9) not individually detected at X-ray
wavelengths suggests a population of obscured AGN among sources in the
transition zone and in the red cloud. Their mean X-ray and mid-IR properties
are consistent with moderately obscured low-luminosity AGN, Compton thick
sources or a mix of both. Morphologies show that major mergers are unlikely to
drive the evolution of this population but minor interactions may play a role.
The incidence of obscured AGN in the red cloud (both direct detections and
stacking results) suggests that BH accretion outlives the termination of the
star-formation. This is also supported by our finding that post-starburst
galaxies at z~0.8 and AGN are associated, in agreement with recent results at
low-z. A large fraction of post-starbursts and red cloud galaxies show evidence
for at least moderate levels of AGN obscuration. This implies that if AGN
outflows cause the colour transformation of galaxies, then some nuclear gas and
dust clouds either remain unaffected or relax to the central galaxy regions
after the quenching their star-formation.Comment: Accepted for publication in MNRA
- …