1,094 research outputs found
Using bio-physical modelling and population genetics for conservation and management of an exploited species, Pecten maximus L.
This is the final version. Available on open access from Wiley via the DOI in this recordData availability statement: The microsatellite data along with the site location data that support the findings of this study are openly available in FigShare at https://doi.org/10.6084/m9.figshare.12907430Connectivity between populations is important when considering conservation or the management of exploitation of vulnerable species. We investigated how populations of a broadcast-spawning marine species (scallop, Pecten maximus) that occur in discrete geographic locations were connected to each other. Population genetic insights were related to the outputs from a three-dimensional hydrodynamic model implemented with scallop larval behaviour to understand the extent to which these areas were linked by oceanographic processes and how this was altered by season and two contrasting years that had strongly different average temperature records (warm vs cold) to provide contrasting oceanographic conditions. Our results span from regional to shelf scale. Connectivity was high at a regional level (e.g. northern Irish Sea), but lower at scales >100 km between sites. Some localities were possibly isolated thus dependent on self-recruitment to sustain local populations. Seasonal timing of spawning and inter-annual fluctuations in seawater temperature influenced connectivity patterns, and hence will affect spatial recruitment. Summer rather than spring spawning increased connectivity among some populations, due to the seasonal strengthening of temperature-driven currents. Furthermore, the warm year resulted in higher levels of modelled connectivity than the cold year. The combination of genetic and oceanographic approaches provided valuable insights into the structure and connectivity at a continental shelf scale. This insight provides a powerful basis for defining conservation management units and the appropriate scale for spatial management. Temporal fluctuations in temperature impact upon variability in connectivity, suggesting that future work should account for ocean warming when investigating population resilience.Isle of Man GovernmentEuropean Fisheries FundEuropean Union Regional Development Fun
A slow gravity compensated Atom Laser
We report on a slow guided atom laser beam outcoupled from a Bose-Einstein
condensate of 87Rb atoms in a hybrid trap. The acceleration of the atom laser
beam can be controlled by compensating the gravitational acceleration and we
reach residual accelerations as low as 0.0027 g. The outcoupling mechanism
allows for the production of a constant flux of 4.5x10^6 atoms per second and
due to transverse guiding we obtain an upper limit for the mean beam width of
4.6 \mu\m. The transverse velocity spread is only 0.2 mm/s and thus an upper
limit for the beam quality parameter is M^2=2.5. We demonstrate the potential
of the long interrogation times available with this atom laser beam by
measuring the trap frequency in a single measurement. The small beam width
together with the long evolution and interrogation time makes this atom laser
beam a promising tool for continuous interferometric measurements.Comment: 7 pages, 8 figures, to be published in Applied Physics
A two-state Raman coupler for coherent atom optics
We present results on a Raman laser-system that resonantly drives a closed
two-photon transition between two levels in different hyperfine ground states
of 87Rb. The coupler is based on a novel optical design for producing two
phase-coherent optical beams to drive a Raman transition. Operated as an
outcoupler, it produces an atom laser in a single internal atomic state, with
the lower divergence and increased brightness typical of a Raman outcoupler.
Due to the optical nature of the outcoupling, the two-state outcoupler is an
ideal candidate for transferring photon correlations onto atom-laser beams. As
our laser system couples just two hyperfine ground states, it has also been
used as an internal state beamsplitter, taking the next major step towards free
space Ramsey interferometry with an atom laser.Comment: 7 Pages, 4 figures: Revised and published in Optics Expres
Cord Blood Glutathione Depletion in Preterm Infants: Correlation with Maternal Cysteine Depletion
Background: Depletion of blood glutathione (GSH), a key antioxidant, is known to occur in preterm infants. Objective: Our aim was to determine: 1) whether GSH depletion is present at the time of birth; and 2) whether it is associated with insufficient availability of cysteine (cys), the limiting GSH precursor, or a decreased capacity to synthesize GSH. Methodology: Sixteen mothers delivering very low birth weight infants (VLBW), and 16 mothers delivering healthy, full term neonates were enrolled. Immediately after birth, erythrocytes from umbilical vein, umbilical artery, and maternal blood were obtained to assess GSH [GSH] and cysteine [cys] concentrations, and the GSH synthesis rate was determined from the incorporation of labeled cysteine into GSH in isolated erythrocytes ex vivo, measured using gas chromatography mass spectrometry. Principal Findings: Compared with mothers delivering at full term, mothers delivering prematurely had markedly lower erythrocyte [GSH] and [cys] and these were significantly depressed in VLBW infants, compared with term neonates. A strong correlation was found between maternal and fetal GSH and cysteine levels. The capacity to synthesize GSH was as high in VLBW as in term infants. Conclusion: The current data demonstrate that: 1) GSH depletion is present at the time of birth in VLBW infants; 2) As VLBW neonates possess a fully active capacity to synthesize glutathione, the depletion may arise from inadequate cysteine availability, potentially due to maternal depletion. Further studies would be needed to determine whether maternal-fetal cysteine transfer is decreased in preterm infants, and, if so, whether cysteine supplementation of mothers at risk of delivering prematurely would strengthen antioxidant defense in preterm neonates
Control of an atom laser using feedback
A generalised method of using feedback to control Bose-Einstein condensates
is introduced. The condensates are modelled by the Gross-Pitaevskii equation,
so only semiclassical fluctations can be suppressed, and back-action from the
measurement is ignored. We show that for any available control, a feedback
scheme can be found to reduce the energy while the appropriate moment is still
dynamic. We demonstrate these schemes by considering a condensate trapped in a
harmonic potential that can be modulated in strength and position. The
formalism of our feedback scheme also allows the inclusion of certain types of
non-linear controls. If the non-linear interaction between the atoms can be
controlled via a Feshbach resonance, we show that the feedback process can
operate with a much higher efficiency.Comment: 6 pages, 7 figure
Pandemic Influenza: Risk of Multiple Introductions and the Need to Prepare for Them
Containing an emerging influenza H5N1 pandemic in its earliest stages may be feasible, but containing multiple introductions of a pandemic-capable strain would be more difficult. Mills and colleagues argue that multiple introductions are likely, especially if risk of a pandemic is high
Atom lasers: production, properties and prospects for precision inertial measurement
We review experimental progress on atom lasers out-coupled from Bose-Einstein
condensates, and consider the properties of such beams in the context of
precision inertial sensing. The atom laser is the matter-wave analog of the
optical laser. Both devices rely on Bose-enhanced scattering to produce a
macroscopically populated trapped mode that is output-coupled to produce an
intense beam. In both cases, the beams often display highly desirable
properties such as low divergence, high spectral flux and a simple spatial mode
that make them useful in practical applications, as well as the potential to
perform measurements at or below the quantum projection noise limit. Both
devices display similar second-order correlations that differ from thermal
sources. Because of these properties, atom lasers are a promising source for
application to precision inertial measurements.Comment: This is a review paper. It contains 40 pages, including references
and figure
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