14,369 research outputs found
Eddy Impacts on the Florida Current
The Gulf Stream in the Atlantic carries warm water northwards and forms both the return closure of the subtropical gyre as well as the upper limb of the meridional overturning circulation. Recent time series recorded east of the Bahamas at 26°N indicate that from May 2009 to April 2011, in contrast with past observations, the northward flowing Antilles Current covaried with the Gulf Stream in the Florida Straitsâthe Florida Currentâeven though the Florida and Antilles Currents are separated by banks and islands spanning 150?km. The peak-to-trough amplitude of transport variations during this period was 15?Ă?106?m3?s?1 for the Florida Current and 12?Ă?106?m3?s?1 for the Antilles Current, at time scales of 50?days to a year. From satellite observations, we show that the fluctuations in both the Florida and Antilles Currents between May 2009 and April 2011 are driven by eddy activity east of the Bahamas. Since the Florida Current time series is a critical time series for the state of the oceans, and often compared to climate models, this newly identified source of variability needs careful consideration when attributing the variability of the Florida Current to changes in the larger-scale circulations (e.g., gyre and overturning) or wind forcing.<br/
Resolved stellar population of distant galaxies in the ELT era
The expected imaging capabilities of future Extremely Large Telescopes (ELTs)
will offer the unique possibility to investigate the stellar population of
distant galaxies from the photometry of the stars in very crowded fields. Using
simulated images and photometric analysis we explore here two representative
science cases aimed at recovering the characteristics of the stellar
populations in the inner regions of distant galaxies. Specifically: case A) at
the center of the disk of a giant spiral in the Centaurus Group, (mu B~21,
distance of 4.6 Mpc); and, case B) at half of the effective radius of a giant
elliptical in the Virgo Cluster (mu~19.5, distance of 18 Mpc). We generate
synthetic frames by distributing model stellar populations and adopting a
representative instrumental set up, i.e. a 42 m Telescope operating close to
the diffraction limit. The effect of crowding is discussed in detail showing
how stars are measured preferentially brighter than they are as the confusion
limit is approached. We find that (i) accurate photometry (sigma~0.1,
completeness >90%) can be obtained for case B) down to I~28.5, J~27.5 allowing
us to recover the stellar metallicity distribution in the inner regions of
ellipticals in Virgo to within ~0.1 dex; (ii) the same photometric accuracy
holds for the science case A) down to J~28.0, K~27.0, enabling to reconstruct
of the star formation history up to the Hubble time via simple star counts in
diagnostic boxes. For this latter case we discuss the possibility of deriving
more detailed information on the star formation history from the analysis of
their Horizontal Branch stars. We show that the combined features of high
sensitivity and angular resolution of ELTs may open a new era for our knowledge
of the stellar content of galaxies of different morphological type up to the
distance of the Virgo cluster.Comment: 21 pages, 17 figures, PASP accepted in pubblicatio
A prototype system for observing the Atlantic Meridional Overturning Circulation - scientific basis, measurement and risk mitigation strategies, and first results
The Atlantic Meridional Overturning Circulation (MOC) carries up to one quarter of the global northward heat transport in the Subtropical North Atlantic. A system monitoring the strength of the MOC volume transport has been operating since April 2004. The core of this system is an array of moored sensors measuring density, bottom pressure and ocean currents. A strategy to mitigate risks of possible partial failures of the array is presented, relying on backup and complementary measurements. The MOC is decomposed into five components, making use of the continuous moored observations, and of cable measurements across the Straits of Florida, and wind stress data. The components compensate for each other, indicating that the system is working reliably. The year-long average strength of the MOC is 18.7±5.6 Sv, with wind-driven and density-inferred transports contributing equally to the variability. Numerical simulations suggest that the surprisingly fast density changes at the western boundary are partially linked to westward propagating planetary wave
Unlocking the potential within: A preliminary study of individual and community outcomes from a university enabling program in rural Australia
© 2016, Adult Learning Australia Inc. All rights reserved.
Many rural communities have a pool of mature-aged local people seeking a career change or better lifestyle, which inevitably involves reskilling or upskilling. These people have strong local ties and are committed to their community. University enabling programs provide a bridge to higher education. This longitudinal study explores the impact on rural mature-aged people of participation in a university enabling program, in terms of further study and employment outcomes. The benefits of enabling programs extend beyond individuals, to family and friends, and beyond. These broader benefits include an enhanced local skills base in key industry areas, and an increased awareness of the value of higher education within the community. Enabling programs are a powerful but under-valued tool in helping to unlock and harness the potential within rural communities, both in the medium and longer term
The FUV spectrum of TW Hya. I. Observations of H Fluorescence
We observed the classical T Tauri star TW Hya with \textit{HST}/STIS using
the E140M grating, from 1150--1700 \AA, with the E230M grating, from 2200--2900
\AA, and with \FUSE from 900--1180 \AA. Emission in 143 Lyman-band H lines
representing 19 progressions dominates the spectral region from 1250--1650 \AA.
The total H emission line flux is erg cm
s, which corresponds to at TW Hya's
distance of 56 pc. A broad stellar \Lya line photoexcites the H from
excited rovibrational levels of the ground electronic state to excited
electronic states. The \ion{C}{2} 1335 \AA doublet, \ion{C}{3} 1175 \AA\
multiplet, and \ion{C}{4} 1550 \AA doublet also electronically excite H.
The velocity shift of the H lines is consistent with the photospheric
radial velocity of TW Hya, and the emission is not spatially extended beyond
the 0\farcs05 resolution of \textit{HST}. The H lines have an intrinsic
FWHM of \kms. One H line is significantly weaker than
predicted by this model because of \ion{C}{2} wind absorption. We also do not
observe any H absorption against the stellar \Lya profile. From these
results, we conclude that the H emission is more consistent with an origin
in a disk rather than in an outflow or circumstellar shell. We also analyze the
hot accretion-region lines (e.g., \ion{C}{4}, \ion{Si}{4}, \ion{O}{6}) of TW
Hya, which are formed at the accretion shock, and discuss some reasons why Si
lines appear significantly weaker than other TR region lines.Comment: accepted by ApJ, 42 pages -- 20 text, 11 figure
The present and future system for measuring the Atlantic meridional overturning circulation and heat transport
of the global combined atmosphere-ocean heat flux and
so is important for the mean climate of the Atlantic
sector of the Northern Hemisphere. This meridional heat
flux is accomplished by both the Atlantic Meridional
Overturning Circulation (AMOC) and by basin-wide
horizontal gyre circulations. In the North Atlantic
subtropical latitudes the AMOC dominates the meridional heat flux, while in subpolar latitudes and in the subtropical South Atlantic the gyre circulations are
also important. Climate models suggest the AMOC will
slow over the coming decades as the earth warms, causing widespread cooling in the Northern hemisphere and additional sea-level rise. Monitoring systems for selected components of the AMOC have been in place in some areas for decades, nevertheless the present observational network provides only a partial view of the AMOC, and does not unambiguously resolve the full variability of the circulation. Additional observations, building on existing measurements, are required to more completely quantify the Atlantic meridional heat transport. A basin-wide monitoring
array along 26.5°N has been continuously measuring the strength and vertical structure of the AMOC and meridional heat transport since March 31, 2004. The array has demonstrated its ability to observe the AMOC variability at that latitude and also a variety of surprising variability that will require substantially longer time series to understand fully. Here we propose monitoring the Atlantic meridional heat transport throughout the Atlantic at selected critical latitudes that have already been identified as regions of interest for the study of deep water formation and the strength of the subpolar gyre, transport variability of the Deep Western Boundary Current (DWBC) as well as the upper limb of the AMOC, and inter-ocean and intrabasin exchanges with the ultimate goal of determining regional and global controls for the AMOC in the North and South Atlantic Oceans. These new arrays will
continuously measure the full depth, basin-wide or choke-point circulation and heat transport at a number
of latitudes, to establish the dynamics and variability at
each latitude and then their meridional connectivity.
Modeling studies indicate that adaptations of the 26.5°N
type of array may provide successful AMOC monitoring at other latitudes. However, further analysis and the development of new technologies will be needed to optimize cost effective systems for providing long term monitoring and data recovery at climate time scales. These arrays will provide benchmark observations of the AMOC that are fundamental for assimilation, initialization, and the verification of coupled hindcast/forecast climate models
Stationarity, soft ergodicity, and entropy in relativistic systems
Recent molecular dynamics simulations show that a dilute relativistic gas
equilibrates to a Juettner velocity distribution if ensemble velocities are
measured simultaneously in the observer frame. The analysis of relativistic
Brownian motion processes, on the other hand, implies that stationary
one-particle distributions can differ depending on the underlying
time-parameterizations. Using molecular dynamics simulations, we demonstrate
how this relativistic phenomenon can be understood within a deterministic model
system. We show that, depending on the time-parameterization, one can
distinguish different types of soft ergodicity on the level of the one-particle
distributions. Our analysis further reveals a close connection between time
parameters and entropy in special relativity. A combination of different
time-parameterizations can potentially be useful in simulations that combine
molecular dynamics algorithms with randomized particle creation, annihilation,
or decay processes.Comment: 4 page
Cocaine Disrupts Pup-Induced Maternal Behavior in Juvenile and Adult Rats
Impaired onset of maternal behavior in first generation rat dams was previously correlated with rearing by cocaine-treated dams and prenatal cocaine exposure. Pup-induced maternal behavior in non-lactating rats has not been examined with regard to cocaine exposure and rearing conditions. First generation male and female juveniles and young adult males reared by cocaine-treated or control dams and prenatally exposed to either cocaine or control conditions were tested for pup-induced maternal behavior at postnatal days 28 and 60. We now report disruptions in pup-induced maternal behavior in both 28 and 60 day old first generation offspring attributable to rearing condition and prenatal cocaine exposure. Originally published Neurotoxicology and Teratology, Vol. 29, No. 6, Nov 200
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