354 research outputs found
Monitoring Oyster Point seagrasses : 1995 to 1999
In the present report, an assessment of changes in seagrass distribution and
abundance since the baseline (November 1995) and previous monitoring surveys of
December 1997 and November 1998 is included. We provide a quantification of
changes between years and comment on the possible impacts of the dredging
program
Preliminary evaluation of an acoustic technique for mapping tropical seagrass habitats
Seagrass meadows in Queensland are important nursery habitat for commercial species of penaeid prawns and fish. Seagrasses are essential food for dugong, Dugong dugon, and green sea turtles, Chelonia mydas (Linnaeus) and act as nutrient and sediment sinks. Seagrasses in coastal regions play important roles in maintaining sediment stability and water clarity. Coastal seagrass meadows are therefore an important resource
economically and ecologically. Information on the species composition, abundance and
distribution of seagrasses is used by management to zone for protection of seagrass habitats
Indications of coherence-incoherence crossover in layered transport
For many layered metals the temperature dependence of the interlayer
resistance has a different behavior than the intralayer resistance. In order to
better understand interlayer transport we consider a concrete model which
exhibits this behavior. A small polaron model is used to illustrate how the
interlayer transport is related to the coherence of quasi-particles within the
layers. Explicit results are given for the electron spectral function,
interlayer optical conductivity and the interlayer magnetoresistance. All these
quantities have two contributions: one coherent (dominant at low temperatures)
and one incoherent (dominant at high temperatures).Comment: 6 pages, 4 figures, REVTEX
Using aerobic exercise to evaluate sub-lethal tolerance of acute warming in fishes
We investigated whether fatigue from sustained aerobic swimming provides a sub-lethal endpoint to define tolerance of acute warming in fishes, as an alternative to loss of equilibrium (LOE) during a critical thermal maximum (CTmax) protocol. Two species were studied, Nile tilapia (Oreochromis niloticus) and pacu (Piaractus mesopotamicus). Each fish underwent an incremental swim test to determine gait transition speed (UGT), where it first engaged the unsteady anaerobic swimming mode that preceded fatigue. After suitable recovery, each fish was exercised at 85% of their own UGT and warmed 1°C every 30 min, to identify the temperature at which they fatigued, denoted as CTswim. Fish were also submitted to a standard CTmax, warming at the same rate as CTswim, under static conditions until LOE. All individuals fatigued in CTswim, at a mean temperature approximately 2°C lower than their CTmax. Therefore, if exposed to acute warming in the wild, the ability to perform aerobic metabolic work would be constrained at temperatures significantly below those that directly threatened survival. The collapse in performance at CTswim was preceded by a gait transition qualitatively indistinguishable from that during the incremental swim test. This suggests that fatigue in CTswim was linked to an inability to meet the tissue oxygen demands of exercise plus warming. This is consistent with the oxygen and capacity limited thermal tolerance (OCLTT) hypothesis, regarding the mechanism underlying tolerance of warming in fishes. Overall, fatigue at CTswim provides an ecologically relevant sub-lethal threshold that is more sensitive to extreme events than LOE at CTmax
Baseline survey of Hinchinbrook region seagrasses - October (spring) 1996
Current coastal zone management issues in the Hinchinbrook region include protection of
fisheries habitats, dugong habitat areas and increases in aquaculture, agriculture and tourist
operations. A regional coastal management plan which is being developed, also requires
detailed information on seagrass resources for the coastal zone from Dunk Island in the north,
to Cleveland Bay in the south. Decreases in estimates of dugong abundance in the southern
half of the Great Barrier Reef region since the 1980's have also prompted the need for
detailed baseline and monitoring surveys of seagrasses in this and other regions
Entanglement between a qubit and the environment in the spin-boson model
The quantitative description of the quantum entanglement between a qubit and
its environment is considered. Specifically, for the ground state of the
spin-boson model, the entropy of entanglement of the spin is calculated as a
function of , the strength of the ohmic coupling to the environment,
and , the level asymmetry. This is done by a numerical
renormalization group treatment of the related anisotropic Kondo model. For
, the entanglement increases monotonically with , until it
becomes maximal for . For fixed , the entanglement
is a maximum as a function of for a value, .Comment: 4 pages, 3 figures. Shortened version restricted to groundstate
entanglemen
Symmetrized mean-field description of magnetic instabilities in k-(BEDT-TTF)_2Cu[N(CN)]_2 Y salts
We present a novel and convenient mean-field method, and apply it to study
the metallic/antiferromagnetic interface of k-(BEDT-TTF)_2Cu[N(CN)]_2 Y organic
superconductors (BEDT_TTF is bis-ethylen-dithio-tetrathiafulvalene, Y=Cl, Br).
The method, which fully exploits the crystal symmetry, allows one to obtain the
mean-field solution of the 2D Hubbard model for very large lattices, up to
6x10^5 sites, yielding a reliable description of the phase boundary in a wide
region of the parameter space. The metal/antiferromagnet transtion appears to
be second order, except for a narrow region of the parameter space, where the
transition is very sharp and possibly first order. The cohexistence of metallic
and antiferromagnetic properties is only observed for the transient state in
the case of smooth second order transitions. The relevance of the present
resaults to the complex experimental behavior of centrosymmetric k-phase
BEDT-TTF salts is discussed.Comment: 9 pages in PS format, 7 figures (included in PS), 1 tabl
Mortality of babies enrolled in a community-based support programme: CONI PLUS (Care of Next Infant Plus).
OBJECTIVE: To report mortality in babies enrolled on a community-based programme, Care of Next Infant Plus (CONI PLUS), which primarily supports parents anxious because of previous sudden unexpected death in infancy (SUDI) in their extended family or following an apparent life threatening event (ALTE) in their baby.
DESIGN: Prospective observational study from 1996 to 2010 in the UK.
RESULTS: Of 6487 babies enrolled, 37 died (5.7 per 1000). There were 2789 (43.0%) SUDI related babies of whom, six died suddenly and unexpectedly (2.15 per 1000). Four babies were sharing a sofa at night or a bed with parent(s) who smoked or had consumed alcohol. Of the 1882 (29.0%) babies enrolled following an ALTE, five died suddenly and unexpectedly (2.66 per 1000): four unexplained and one due to infection. None occurred while sharing a sleep surface, and at least three died during the day. The remaining 1816 (28%) babies were enrolled for other reasons. Seven died suddenly and unexpectedly (3.85 per 1000), two were unexplained and none associated with bed sharing.
CONCLUSIONS: The number of SUDI deaths in babies enrolled on CONI PLUS is higher than expected from UK averages. Deaths in babies enrolled because of family history of SUDI were mostly associated with inappropriate sharing of a sleep surface at night and mostly outside the peak age range for sudden infant death. The opposite is true for those enrolled following an ALTE. The number of deaths is small but findings suggest a different mechanism for death in these two groups
Non-destructive, dynamic detectors for Bose-Einstein condensates
We propose and analyze a series of non-destructive, dynamic detectors for
Bose-Einstein condensates based on photo-detectors operating at the shot noise
limit. These detectors are compatible with real time feedback to the
condensate. The signal to noise ratio of different detection schemes are
compared subject to the constraint of minimal heating due to photon absorption
and spontaneous emission. This constraint leads to different optimal operating
points for interference-based schemes. We find the somewhat counter-intuitive
result that without the presence of a cavity, interferometry causes as much
destruction as absorption for optically thin clouds. For optically thick
clouds, cavity-free interferometry is superior to absorption, but it still
cannot be made arbitrarily non-destructive . We propose a cavity-based
measurement of atomic density which can in principle be made arbitrarily
non-destructive for a given signal to noise ratio
Entanglement of two-mode Bose-Einstein condensates
We investigate the entaglement characteristics of two general bimodal
Bose-Einstein condensates - a pair of tunnel-coupled Bose-Einstein condensates
and the atom-molecule Bose-Einstein condensate. We argue that the entanglement
is only physically meaningful if the system is viewed as a bipartite system,
where the subsystems are the two modes. The indistinguishibility of the
particles in the condensate means that the atomic constituents are physically
inaccessible and thus the degree of entanglement between individual particles,
unlike the entanglement between the modes, is not experimentally relevant so
long as the particles remain in the condensed state. We calculate the
entanglement between the modes for the exact ground state of the two bimodal
condensates and consider the dynamics of the entanglement in the tunnel-coupled
case.Comment: 11 pages, 8 figures, submitted to Physical Review A, to be presented
at the third UQ Mathematical Physics workshop, Oct. 4-6; changes made in
response to referee comment
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