239 research outputs found
Alien Registration- Boudreau, Dolph P. (Auburn, Androscoggin County)
https://digitalmaine.com/alien_docs/30952/thumbnail.jp
Optical Geolocation for Small Unmanned Aerial Systems
This paper presents an airborne optical geolocation system using four optical targets to provide position and attitude estimation for a sUAS supporting the NASA Acoustic Research Mission (ARM), where the goal is to reduce nuisance airframe noise during approach and landing. A large precision positioned microphone array captures the airframe noise for multiple passes of a Gulfstream III aircraft. For health monitoring of the microphone array, the Acoustic Calibration Vehicle (ACV) sUAS completes daily flights with an onboard speaker emitting tones at frequencies optimized for determining microphone functionality. An accurate position estimate of the ACV relative to the array is needed for microphone health monitoring. To this end, an optical geolocation system using a downward facing camera mounted to the ACV was developed. The 3D positioning of the ACV is computed using the pinhole camera model. A novel optical geolocation algorithm first detects the targets, then a recursive algorithm tightens the localization of the targets. Finally, the position of the sUAS is computed using the image coordinates of the targets, the 3D world coordinates of the targets, and the camera matrix. A Real-Time Kinematic GPS system is used to compare the optical geolocation system
Drought affects sex ratio and growth of painted turtles in a long-term study in Nebraska
Climate forecasts suggest the Great Plains of North America have increased risk of droughts during global warming. Environmental factors have potential to influence turtle populations in aquatic habitats through temperature-dependent sex determination and influences on food availability. Long-term studies are critical to evaluate the influence of climatic variation on turtles. We used a 12-year set of mark-recapture data collected from painted turtles (Chrysemys picta, n = 162) in a pond in Keith County, Nebraska during 2005â2016 to assess variation in sex ratio and growth dynamics. Southwest Nebraska experienced two periods of drought during our study (Palmer Hydrologic Drought Index [PHDI] range: -4.5 to 6.7). Despite a relatively stable depth of water in our study pond, the proportion of males in the second size class (carapace length 95â130 mm) decreased when the PHDI during their incubation period indicated hotter, drier conditions. Discrete, mean annual growth (G) of females \u3e30 mm below asymptotic carapace length was greater during wetter years (Gnon-drought = 15.0, Gdrought = 11.5), and a drought coefficient (D) in our modified von Bertalanffy model reflected reduced growth of both males (D = -0.0226) and females (D = -0.0393) during drought years. Our long-term research provides context to the complexity by which turtle species may respond to changes in long-term climate conditions
Geometric Aspects of Ambrosetti-Prodi operators with Lipschitz nonlinearities
For Dirichlet boundary conditions on a bounded domain, what happens to the
critical set of the Ambrosetti-Prodi operator if the nonlinearity is only a
Lipschitz map? It turns out that many properties which hold in the smooth case
are preserved, despite of the fact that the operator is not even differentiable
at some points. In particular, a global Lyapunov-Schmidt decomposition of great
convenience for numerical inversion is still available
Development of high-performance alkali-hybrid polarized He-3 targets for electron scattering
Background: Polarized He-3 targets have been used as effective polarized neutron targets for electron scattering experiments for over twenty years. Over the last ten years, the effective luminosity of polarized He-3 targets based on spin-exchange optical pumping has increased by over an order of magnitude. This has come about because of improvements in commercially-available lasers and an improved understanding of the physics behind the polarization process. Purpose: We present the development of high-performance polarized He-3 targets for use in electron scattering experiments. Improvements in the performance of polarized He-3 targets, target properties, and operating parameters are documented. Methods: We utilize the technique of alkali-hybrid spin-exchange optical pumping to polarize the He-3 targets. Spectrally narrowed diode lasers used for the optical pumping greatly improved the performance. A simulation of the alkali-hybrid spin-exchange optical pumping process was developed to provide guidance in the design of the targets. Data was collected during the characterization of 24 separate glass target cells, each of which was constructed while preparing for one of four experiments at Jefferson Laboratory in Newport News, Virginia. Results: From the data obtained we made determinations of the so-called X-factors that quantify a temperaturedependent and as-yet poorly understood spin-relaxation mechanism that limits the maximum achievable He-3 polarization to well under 100%. The presence of the X-factor spin-relaxation mechanism was clearly evident in our data. Good agreement between the simulation and the actual target performance was obtained by including details such as off-resonant optical pumping. Included in our results is ameasurement of the K-He-3 spin-exchange rate coefficient k(se)(K) = (7.46 +/- 0.62) x 10(-20) cm(3)/s over the temperature range 503 K to 563 K. Conclusions: In order to achieve high performance under the operating conditions described in this paper, the K to Rb alkali vapor density ratio should be about 5 +/- 2 and the line width of the optical pumping lasers should be no more than 0.3 nm. Our measurements of the X-factors under these conditions seem to indicate the He-3 polarization is limited to approximate to 90%. The simulation results, now benchmarked against experimental data, are useful for the design of future targets. Further work is required to better understand the temperature dependence of the X-factor spin-relaxation mechanism and the limitations of our optical pumping simulation
Regulation of Selenocysteine Content of Human Selenoprotein P by Dietary Selenium and Insertion of Cysteine in Place of Selenocysteine
Selenoproteins are a unique group of proteins that contain selenium in the
form of selenocysteine (Sec) co-translationally inserted in response to a UGA
codon with the help of cis- and trans-acting factors. Mammalian selenoproteins
contain single Sec residues, with the exception of selenoprotein P (SelP) that
has 7â15 Sec residues depending on species. Assessing an individualâs selenium
status is important under various pathological conditions, which requires a
reliable selenium biomarker. Due to a key role in organismal selenium
homeostasis, high Sec content, regulation by dietary selenium, and
availability of robust assays in human plasma, SelP has emerged as a major
biomarker of selenium status. Here, we found that Cys is present in various
Sec positions in human SelP. Treatment of cells expressing SelP with
thiophosphate, an analog of the selenium donor for Sec synthesis, led to a
nearly complete replacement of Sec with Cys, whereas supplementation of cells
with selenium supported Sec insertion. SelP isolated directly from human
plasma had up to 8% Cys inserted in place of Sec, depending on the Sec
position. These findings suggest that a change in selenium status may be
reflected in both SelP concentration and its Sec content, and that
availability of the SelP-derived selenium for selenoprotein synthesis may be
overestimated under conditions of low selenium status due to replacement of
Sec with Cys
The Power of Environmental Observatories for Advancing Multidisciplinary Research, Outreach, and Decision Support: The Case of the Minnesota River Basin
An edited version of this paper was published by AGU. Copyright 2019 American Geophysical Union.Observatoryâscale data collection efforts allow unprecedented opportunities for integrative, multidisciplinary investigations in large, complex watersheds, which can affect management decisions and policy. Through the National Science Foundationâfunded REACH (REsilience under Accelerated CHange) project, in collaboration with the Intensively Managed LandscapesâCritical Zone Observatory, we have collected a series of multidisciplinary data sets throughout the Minnesota River Basin in southâcentral Minnesota, USA, a 43,400âkm2 tributary to the Upper Mississippi River. Postglacial incision within the Minnesota River valley created an erosional landscape highly responsive to hydrologic change, allowing for transdisciplinary research into the complex cascade of environmental changes that occur due to hydrology and land use alterations from intensive agricultural management and climate change. Data sets collected include water chemistry and biogeochemical data, geochemical fingerprinting of major sediment sources, highâresolution monitoring of river bluff erosion, and repeat channel crossâsectional and bathymetry data following major floods. The data collection efforts led to development of a series of integrative reduced complexity models that provide deeper insight into how water, sediment, and nutrients route and transform through a large channel network and respond to change. These models represent the culmination of efforts to integrate interdisciplinary data sets and science to gain new insights into watershedâscale processes in order to advance management and decision making. The purpose of this paper is to present a synthesis of the data sets and models, disseminate them to the community for further research, and identify mechanisms used to expand the temporal and spatial extent of shortâterm observatoryâscale data collection efforts
Gas dynamics in high-luminosity polarized He-3 targets using diffusion and convection
The dynamics of the movement of gas is discussed for two-chambered polarized
He-3 target cells of the sort that have been used successfully for many
electron scattering experiments. A detailed analysis is presented showing that
diffusion is a limiting factor in target performance, particularly as these
targets are run at increasingly high luminosities. Measurements are presented
on a new prototype polarized He-3 target cell in which the movement of gas is
due largely to convection instead of diffusion. NMR tagging techniques have
been used to visualize the gas flow, showing velocities along a
cylindrically-shaped target of between 5-80 cm/min. The new target design
addresses one of the principle obstacles to running polarized He-3 targets at
substantially higher luminosities while simultaneously providing new
flexibility in target geometry.Comment: First revision: 14 pages, 9 figures, submitted to Phys. Rev. C. We
have shortened our discussion of the limitations inherent in various
historical He-3 targets, and we have added a discussion exploring the optimal
performance that can be expected from a suitably modified target based on
diffusion-based mixing. A reference (Jones et. al.) was added. The results we
present have not change
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