111 research outputs found
The development of ocean test beds for ocean technology adaptation and integration into the emerging U.S. offshore wind energy industry
The landscape of applied ocean technology is rapidly changing with forces of innovation emerging from basic ocean science research methodologies as well as onshore high tech sectors. There is a critical need for ocean-related industries to continue to modernize via the adoption of state-of-the-art practices to advance rapidly changing industry objectives, maintain competitiveness, and be careful stewards of the ocean as a common resource. These objectives are of national importance for the dynamic ocean energy sector, and a mechanism by which new and promising technologies can be validated and adopted in an open and benchmarked process is needed. POWER-US seeks to develop Ocean Test Beds as research and development infrastructure capable of driving innovative observations, modeling, and monitoring of the physical, biological, and use characteristics present in offshore wind energy installation areas.AK acknowledges internal support from the Woods Hole Oceanographic Institution via the Houghton Foundation Award
Formation and Evolution of Planetary Systems: Cold Outer Disks Associated with Sun-like stars
We present the discovery of debris systems around three solar mass stars
based upon observations performed with the Spitzer Space Telescope as part of a
Legacy Science Program, ``the Formation and Evolution of Planetary Systems''
(FEPS). We also confirm the presence of debris around two other stars. All the
stars exhibit infrared emission in excess of the expected photospheres in the
70 micron band, but are consistent with photospheric emission at <= 33 micron.
This restricts the maximum temperature of debris in equilibrium with the
stellar radiation to T < 70 K. We find that these sources are relatively old in
the FEPS sample, in the age range 0.7 - 3 Gyr. Based on models of the spectral
energy distributions, we suggest that these debris systems represent materials
generated by collisions of planetesimal belts. We speculate on the nature of
these systems through comparisons to our own Kuiper Belt, and on the likely
planet(s) responsible for stirring the system and ultimately releasing dust
through collisions. We further report observations of a nearby star HD 13974 (d
=11 pc) that is indistinguishable from a bare photosphere at both 24 micron and
70 micron. The observations place strong upper limits on the presence of any
cold dust in this nearby system (L_IR/L_* < 10^{-5.2}).Comment: 31 pages, 9 figures, accepted for publication in Ap
The Jet and Circumnuclear Environment of 3C 293
We present the new HST near-infrared polarimetry, broad and narrow-band
imaging, and MERLIN 4.5GHz Multi-Frequency Synthesis radio imaging of 3C 293, a
unique radio galaxy whose host is an obvious merger remnant, in an
exceptionally under-dense region of space. We have discovered near-infrared,
optical, and ultra-violet synchrotron emission from the jet. In the optical,
the jet is mostly obscured by a dust lane, but three knots are clear in our HST
NICMOS images at 1.6 and 2.0 microns, clearly aligning with features in the
radio. The outer jet knot is highly polarized (~15%) at 2 microns, confirming
the synchrotron emission mechanism. The radio-IR spectral index steepens
significantly with distance from the nucleus, as in 3C 273 and in contrast to M
87. The inner knot is visible (with hindsight) on the WFPC2 and STIS images
obtained for the earlier 3CR HST snapshot surveys. There is no [Fe II] emission
seen associated with the jet, constraining the role of shock-induced ionisation
by the jet. Overall there is a strong implication that the NIR jet emission is
indeed synchrotron.
From our NIR images, the core of the galaxy is clearly identifiable with the
main feature in the western extension of the radio ``jet'' image, although no
unresolved AGN component is identifiable even at K-band, consistent with an
FRII-like nucleus obscured by an optically thick torus. The galaxy appears to
have a single nucleus, with any multiple nuclei falling within the central
</~100 pc.Comment: ApJ accepted. 31 pages, 12 figures reproduced here at low resolution.
High resolution version available from
http://www.stsci.edu/~floyd/BIBLIOTECA/3c293
Lidar Sensor Performance in Closed-Loop Flight Testing of the Morpheus Rocket-Propelled Lander to a Lunar-Like Hazard Field
For the first time, a suite of three lidar sensors have been used in flight to scan a lunar-like hazard field, identify a safe landing site, and, in concert with an experimental Guidance, Navigation, and Control (GN&C) system, help to guide the Morpheus autonomous, rocket-propelled, free-flying lander to that safe site on the hazard field. The lidar sensors and GN&C system are part of the Autonomous Precision Landing and Hazard Detection and Avoidance Technology (ALHAT) project which has been seeking to develop a system capable of enabling safe, precise crewed or robotic landings in challenging terrain on planetary bodies under any ambient lighting conditions. The 3-D imaging Flash Lidar is a second generation, compact, real-time, aircooled instrument developed from a number of components from industry and NASA and is used as part of the ALHAT Hazard Detection System (HDS) to scan the hazard field and build a 3-D Digital Elevation Map (DEM) in near-real time for identifying safe sites. The Flash Lidar is capable of identifying a 30 cm hazard from a slant range of 1 km with its 8 cm range precision (1-s). The Flash Lidar is also used in Hazard Relative Navigation (HRN) to provide position updates down to a 250m slant range to the ALHAT navigation filter as it guides Morpheus to the safe site. The Navigation Doppler Lidar (NDL) system has been developed within NASA to provide velocity measurements with an accuracy of 0.2 cm/sec and range measurements with an accuracy of 17 cm both from a maximum range of 2,200 m to a minimum range of several meters above the ground. The NDL"TM"s measurements are fed into the ALHAT navigation filter to provide lander guidance to the safe site. The Laser Altimeter (LA), also developed within NASA, provides range measurements with an accuracy of 5 cm from a maximum operational range of 30 km down to 1 m and, being a separate sensor from the Flash Lidar, can provide range along a separate vector. The LA measurements are also fed into the ALHAT navigation filter to provide lander guidance to the safe site. The flight tests served as the culmination of the TRL 6 journey for the ALHAT system and included launch from a pad situated at the NASA-Kennedy Space Center Shuttle Landing Facility (SLF) runway, a lunar-like descent trajectory from an altitude of 250m, and landing on a lunar-like hazard field of rocks, craters, hazardous slopes, and safe sites 400m down-range just off the North end of the runway. The tests both confirmed the expected performance and also revealed several challenges present in the flight-like environment which will feed into future TRL advancement of the sensors. Guidance provided by the ALHAT system was impeded in portions of the trajectory and intermittent near the end of the trajectory due to optical effects arising from air heated by the rocket engine. The Flash Lidar identified hazards as small as 30 cm from the maximum slant range of 450 m which Morpheus could provide; however, it was occasionally susceptible to an increase in range noise due to scintillation arising from air heated by the Morpheus rocket engine which entered its Field-of-View (FOV). The Flash Lidar was also susceptible to pre-triggering, during the HRN phase, on a dust cloud created during launch and transported down-range by the wind. The NDL provided velocity and range measurements to the expected accuracy levels yet it was also susceptible to signal degradation due to air heated by the rocket engine. The LA, operating with a degraded transmitter laser, also showed signal attenuation over a few seconds at a specific phase of the flight due to the heat plume generated by the rocket engine
Red hot frogs:Identifying the Australian frogs most at risk of extinction
More than a third of the world’s amphibian species are listed as Threatened or Extinct, with a recent assessment identifying 45 Australian frogs (18.4% of the currently recognised species) as ‘Threatened’ based on IUCN criteria. We applied structured expert elicitation to 26 frogs assessed as Critically Endangered and Endangered to estimate their probability of extinction by 2040. We also investigated whether participant experience (measured as a self-assigned categorical score, i.e. ‘expert’ or ‘non-expert’) influenced the estimates. Collation and analysis of participant opinion indicated that eight species are at high risk (>50% chance) of becoming extinct by 2040, with the disease chytridiomycosis identified as the primary threat. A further five species are at moderate–high risk (30–50% chance), primarily due to climate change. Fourteen of the 26 frog species are endemic to Queensland, with many species restricted to small geographic ranges that are susceptible to stochastic events (e.g. a severe heatwave or a large bushfire). Experts were more likely to rate extinction probability higher for poorly known species (those with <10 experts), while non-experts were more likely to rate extinction probability higher for better-known species. However, scores converged following discussion, indicating that there was greater consensus in the estimates of extinction probability. Increased resourcing and management intervention are urgently needed to avert future extinctions of Australia’s frogs. Key priorities include developing and supporting captive management and establishing or extending in-situ population refuges to alleviate the impacts of disease and climate change
Range-wide sources of variation in reproductive rates of northern spotted owls
We conducted a range-wide investigation of the dynamics of site-level reproductive rate of northern spotted owls using survey data from 11 study areas across the subspecies geographic range collected during 1993–2018. Our analytical approach accounted for imperfect detection of owl pairs and misclassification of successful reproduction (i.e., at least one young fledged) and contributed further insights into northern spotted owl population ecology and dynamics. Both nondetection and state misclassification were important, especially because factors affecting these sources of error also affected focal ecological parameters. Annual probabilities of site occupancy were greatest at sites with successful reproduction in the previous year and lowest for sites not occupied by a pair in the previous year. Site-specific occupancy transition probabilities declined over time and were negatively affected by barred owl presence. Overall, the site-specific probability of successful reproduction showed substantial year-to-year fluctuations and was similar for occupied sites that did or did not experience successful reproduction the previous year. Site-specific probabilities for successful reproduction were very small for sites that were unoccupied the previous year. Barred owl presence negatively affected the probability of successful reproduction by northern spotted owls in Washington and California, as predicted, but the effect in Oregon was mixed. The proportions of sites occupied by northern spotted owl pairs showed steep, near-monotonic declines over the study period, with all study areas showing the lowest observed levels of occupancy to date. If trends continue it is likely that northern spotted owls will become extirpated throughout large portions of their range in the coming decades
A Computational Study on the Role of Gap Junctions and Rod Ih Conductance in the Enhancement of the Dynamic Range of the Retina
Recent works suggest that one of the roles of gap junctions in sensory systems is to enhance their dynamic range by avoiding early saturation in the first processing stages. In this work, we use a minimal conductance-based model of the ON rod pathways in the vertebrate retina to study the effects of electrical synaptic coupling via gap junctions among rods and among AII amacrine cells on the dynamic range of the retina. The model is also used to study the effects of the maximum conductance of rod hyperpolarization activated current Ih on the dynamic range of the retina, allowing a study of the interrelations between this intrinsic membrane parameter with those two retina connectivity characteristics. Our results show that for realistic values of Ih conductance the dynamic range is enhanced by rod-rod coupling, and that AII-AII coupling is less relevant to dynamic range amplification in comparison with receptor coupling. Furthermore, a plot of the retina output response versus input intensity for the optimal parameter configuration is well fitted by a power law with exponent . The results are consistent with predictions of more theoretical works and suggest that the earliest expression of gap junctions along the rod pathways, together with appropriate values of rod Ih conductance, has the highest impact on vertebrate retina dynamic range enhancement
Resveratrol Increases Glucose Induced GLP-1 Secretion in Mice: A Mechanism which Contributes to the Glycemic Control
Resveratrol (RSV) is a potent anti-diabetic agent when used at high doses. However, the direct targets primarily responsible for the beneficial actions of RSV remain unclear. We used a formulation that increases oral bioavailability to assess the mechanisms involved in the glucoregulatory action of RSV in high-fat diet (HFD)-fed diabetic wild type mice. Administration of RSV for 5 weeks reduced the development of glucose intolerance, and increased portal vein concentrations of both Glucagon-like peptid-1 (GLP-1) and insulin, and intestinal content of active GLP-1. This was associated with increased levels of colonic proglucagon mRNA transcripts. RSV-mediated glucoregulation required a functional GLP-1 receptor (Glp1r) as neither glucose nor insulin levels were modulated in Glp1r-/- mice. Conversely, levels of active GLP-1 and control of glycemia were further improved when the Dipeptidyl peptidase-4 (DPP-4) inhibitor sitagliptin was co-administered with RSV. In addition, RSV treatment modified gut microbiota and decreased the inflammatory status of mice. Our data suggest that RSV exerts its actions in part through modulation of the enteroendocrine axis in vivo
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