1,093 research outputs found

    New Constraints on the Composition of Jupiter from Galileo Measurements and Interior Models

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    Using the helium abundance measured by Galileo in the atmosphere of Jupiter and interior models reproducing the observed external gravitational field, we derive new constraints on the composition and structure of the planet. We conclude that, except for helium which must be more abundant in the metallic interior than in the molecular envelope, Jupiter could be homogeneous (no core) or could have a central dense core up to 12 Earth masses. The mass fraction of heavy elements is less than 7.5 times the solar value in the metallic envelope and between 1 and 7.2 times solar in the molecular envelope. The total amount of elements other than hydrogen and helium in the planet is between 11 and 45 Earth masses.Comment: 15 pages, 2 figures (1 color

    CAPSTONE: A Summary of Flight Operations to Date in the Cislunar Environment

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    The cislunar environment is about to get much busier and with this increase in traffic comes an increase in the demand for limited resources such as Earth based tracking of and communications with assets operating in and around the Moon. With the number of NASA, commercial, and international missions to the Moon growing rapidly, the need to make these future endeavors as efficient as possible is a challenge that is being solved now. Advanced Space is aiming to mitigate these resource limitations by enabling spacecraft in the cislunar environment to navigate autonomously and reduce the need for oversubscribed ground assets for navigation and maneuver planning. Launched in June 2022, the Cislunar Autonomous Positioning System Technology Operations and Navigation Experiment (CAPSTONE) mission utilizes a 12U CubeSat to demonstrate both the core software for the Cislunar Autonomous Positioning System (CAPS) as well as a validation of the mission design and operations of the Near Rectilinear Halo Orbit (NRHO) that NASA has baselined for the Artemis Lunar Gateway architecture. The CAPS software enables cislunar missions to manage their navigation functions themselves and reduces the reliance on Earth based tracking requirements without putting these missions at increased risk. Upon arrival in the NRHO, the CAPSTONE spacecraft will soon initiate its navigation demonstration mission in collaboration with the Lunar Reconnaissance Orbiter (LRO) operations team at NASA’s Goddard Space Flight Center to demonstrate autonomous inter-spacecraft ranging and autonomous navigation between the CAPSTONE spacecraft and LRO. Critical success criteria for CAPSTONE in this demonstration are 1) semi-autonomous operations and orbital maintenance of a spacecraft in an NRHO, 2) collection of inter-spacecraft ranging data, and 3) execution of the CAPS navigation software system in autonomous mode on-board the CAPSTONE spacecraft. Additionally, CAPSTONE continues to demonstrate an innovative one-way ranging navigation approach utilizing a Chip Scale Atomic Clock (CSAC), unique firmware installed on the Iris radio, and onboard autonomous navigation algorithms developed JPL an implemented by Advanced Space. Advanced Space, along with our partners at NASA’s Space Technology Mission Directorate, (STMD), Advanced Exploration Systems (AES), Launch Services Program (LSP), NASA Ames’ Small Spacecraft Office, the Jet Propulsion Lab (JPL), Terran Orbital and Rocket Lab, envision the CAPSTONE mission as a key enabler of both NASA’s upcoming Gateway operations involving multiple spacecraft and eventually the ever-expanding commercial cislunar economy. Over the next 21 months, CAPSTONE will demonstrate an efficient low energy orbital transfer to the lunar vicinity, an insertion into the NRHO, and a risk reducing validation of key exploration operations and technologies required for the ultimate success of NASA’s lunar exploration plans. This paper includes an overview of the mission, the current mission operational status, lessons learned from the launch, lunar transfer, and insertion into the NRHO, an overview of operations plan for the NRHO, and other lessons learned to date in order to inform future missions in support of national exploration and scientific objectives

    CAPSTONE: A CubeSat Pathfinder for the Lunar Gateway Ecosystem

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    The cislunar environment is about to get much busier and with this increase in traffic comes an increase in the demand for limited resources such as Earth based tracking of and communications with assets operating in and around the Moon. With the number of NASA, commercial, and international missions to the Moon growing rapidly in the next few years, the need to make these future endeavors as efficient as possible is a challenge that is being solved now. Advanced Space is aiming to mitigate these resource limitations by enabling the numerous spacecraft in the cislunar environment to navigate autonomously and reduce the need for oversubscribed ground assets for navigation and maneuver planning. Scheduled to launch on a Rocket Lab Electron in October 2021, the Cislunar Autonomous Positioning System Technology Operations and Navigation Experiment (CAPSTONE) mission will leverage a 12U CubeSat to demonstrate both the core software for the Cislunar Autonomous Positioning System (CAPS) as well as a validation of the mission design and operations of the Near Rectilinear Halo Orbit (NRHO) that NASA has baselined for the Artemis Lunar Gateway architecture. Currently being developed in a Phase III of NASA’s SBIR program, our CAPS software will allow missions to manage themselves and enable more critical communications to be prioritized between Earth and future cislunar missions without putting these missions at increased risk. CAPSTONE is the pathfinder mission for NASA’s Artemis program. The overall mission will include collaboration with the Lunar Reconnaissance Orbiter (LRO) operations team at NASA Goddard Space Flight Center to demonstrate inter-spacecraft ranging between the CAPSTONE spacecraft and LRO and with the NASA Gateway Operations team at NASA Johnson Space Center to inform the requirements and autonomous mission operations approach for the eventual Gateway systems. Critical success criteria for CAPSTONE in this demonstration are a transfer to and arrival into an NRHO, semi-autonomous operations and orbital maintenance of a spacecraft in an NRHO, collection of inter-spacecraft ranging data, and execution of the CAPS navigation software system on-board the CAPSTONE spacecraft. Advanced Space along with our partners at NASA’s Space Technology Mission Directorate, Advanced Exploration Systems, Launch Services Program, NASA Ames Small Spacecraft Office, Tyvak Nano-Satellite Systems and Rocket Lab, envision the CAPSTONE mission as a key enabler of both NASA’s Gateway operations involving multiple spacecraft and eventually the ever-expanding commercial cislunar economy. This low cost, high value mission will demonstrate an efficient low energy orbital transfer to the lunar vicinity and an insertion and operations approach to the NRHO that ultimately will demonstrate a risk reducing validation of key exploration operations and technologies required for the ultimate success of NASA’s lunar exploration plans, including the planned human return to the lunar surface. This presentation will include the current mission status (which would include the launch and early mission operations), the operations plan for the NRHO, and lessons learned to date in order to inform future CubeSat pathfinders in support of national exploration and scientific objectives

    Comparison of prestellar core elongations and large-scale molecular cloud structures in the Lupus 1 region

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    Turbulence and magnetic fields are expected to be important for regulating molecular cloud formation and evolution. However, their effects on sub-parsec to 100 parsec scales, leading to the formation of starless cores, are not well understood. We investigate the prestellar core structure morphologies obtained from analysis of the Herschel-SPIRE 350 mum maps of the Lupus I cloud. This distribution is first compared on a statistical basis to the large-scale shape of the main filament. We find the distribution of the elongation position angle of the cores to be consistent with a random distribution, which means no specific orientation of the morphology of the cores is observed with respect to the mean orientation of the large-scale filament in Lupus I, nor relative to a large-scale bent filament model. This distribution is also compared to the mean orientation of the large-scale magnetic fields probed at 350 mum with the Balloon-borne Large Aperture Telescope for Polarimetry during its 2010 campaign. Here again we do not find any correlation between the core morphology distribution and the average orientation of the magnetic fields on parsec scales. Our main conclusion is that the local filament dynamics---including secondary filaments that often run orthogonally to the primary filament---and possibly small-scale variations in the local magnetic field direction, could be the dominant factors for explaining the final orientation of each core

    Volume 15

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    Introduction Dr. Amorette Barber, Director, Office of Student Research From the Editor Dr. Hannah Dudley-Shotwell Artist’s Statement Connor Thompson On mentorship Dr. John Miller The Meat of the Matter: Allen, Human and Animal in Terry Blsson’s “They’re Made of Out of Meat” by Emily Steffenhagen “Please REBLOG!”: An Ethical analysis of Doxxing, Internet Vigilantism and Racists Getting Fired by Emily Robertson Journaling: Paper Has More Patience Than People by Luis Fernando Dos Reis The Effects of Climate Change on the Archeological World by Emily Farmer Lowered Seat Height Does Not Impair Wingate Performance in Untrained Cyclists by Samuel Villa, Robert Allison, and Zachary Chessor Intentions, Interpretations, and the Paradoxes of Asimov’s Laws of Robotics by Meagan Borden How Trans-Exclusionary Radical Feminists Define and Defend Women’s Spaces by Austin Burnett The Impeachment of Andrew Johnson by Larry W. Grant, Jr. “unsex me here”: Lady Macbeth’s Performance of Female Masculinity by Tristan Marowski Monstrosity, Queer Desire, and écriture féminine in Sherldan le Fanu’s Carmilla by Emma Moore The Surfaces of Loathsome Beauty in the Picture of Dorian Gray by Pearl Sif

    The balloon-borne large-aperture submillimeter telescope for polarimetry: BLAST-Pol

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    The Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry (BLAST-Pol) is a suborbital mapping experiment designed to study the role played by magnetic fields in the star formation process. BLAST-Pol is the reconstructed BLAST telescope, with the addition of linear polarization capability. Using a 1.8 m Cassegrain telescope, BLAST-Pol images the sky onto a focal plane that consists of 280 bolometric detectors in three arrays, observing simultaneously at 250, 350, and 500 um. The diffraction-limited optical system provides a resolution of 30'' at 250 um. The polarimeter consists of photolithographic polarizing grids mounted in front of each bolometer/detector array. A rotating 4 K achromatic half-wave plate provides additional polarization modulation. With its unprecedented mapping speed and resolution, BLAST-Pol will produce three-color polarization maps for a large number of molecular clouds. The instrument provides a much needed bridge in spatial coverage between larger-scale, coarse resolution surveys and narrow field of view, and high resolution observations of substructure within molecular cloud cores. The first science flight will be from McMurdo Station, Antarctica in December 2010.Comment: 14 pages, 9 figures Submitted to SPIE Astronomical Telescopes and Instrumentation Conference 201

    Iron bioavailability in two commercial cultivars of wheat: a comparison between wholegrain and white flour and the effects of nicotianamine and 2'-deoxymugineic acid on iron uptake into Caco-2 cells

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    Iron bioavailability in unleavened white and wholegrain bread made from two commercial wheat varieties was assessed by measuring ferritin production in Caco-2 cells. The breads were subjected to simulated gastrointestinal digestion and the digests applied to the Caco-2 cells. Although Riband grain contained a lower iron concentration than Rialto, iron bioavailability was higher. No iron was taken up by the cells from white bread made from Rialto flour or from wholegrain bread from either variety, but Riband white bread produced a small ferritin response. The results probably relate to differences in phytate content of the breads, although iron in soluble monoferric phytate was demonstrated to be bioavailable in the cell model. Nicotianamine, an iron chelator in plants involved in iron transport, was a more potent enhancer of iron uptake into Caco-2 cells than ascorbic acid or 2'-deoxymugineic acid, another metal chelator present in plants

    Deformable two-dimensional photonic crystal slab for cavity optomechanics

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    We have designed photonic crystal suspended membranes with optimized optical and mechanical properties for cavity optomechanics. Such resonators sustain vibration modes in the megahertz range with quality factors of a few thousand. Thanks to a two-dimensional square lattice of holes, their reflectivity at normal incidence at 1064 nm reaches values as high as 95%. These two features, combined with the very low mass of the membrane, open the way to the use of such periodic structures as deformable end-mirrors in Fabry-Perot cavities for the investigation of cavity optomechanical effect

    The tribulations of trials: Lessons learnt recruiting 777 older adults into REtirement in ACTion (REACT), a trial of a community, group-based active ageing intervention targeting mobility disability

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    © The Author(s) 2020. Published by Oxford University Press on behalf of The Gerontological Society of America. BACKGROUND: Challenges of recruitment to randomized controlled trials (RCTs) and successful strategies to overcome them should be clearly reported to improve recruitment into future trials. REtirement in ACTion (REACT) is a United Kingdom-based multicenter RCT recruiting older adults at high risk of mobility disability to a 12-month group-based exercise and behavior maintenance program or to a minimal Healthy Aging control intervention. METHODS: The recruitment target was 768 adults, aged 65 years and older scoring 4-9 on the Short Physical Performance Battery (SPPB). Recruitment methods include the following: (a) invitations mailed by general practitioners (GPs); (b) invitations distributed via third-sector organizations; and (c) public relations (PR) campaign. Yields, efficiency, and costs were calculated. RESULTS: The study recruited 777 (33.9% men) community-dwelling, older adults (mean age 77.55 years (SD 6.79), mean SPPB score 7.37 (SD 1.56)), 95.11% white (n = 739) and broadly representative of UK quintiles of deprivation. Over a 20-month recruitment period, 25,559 invitations were issued. Eighty-eight percent of the participants were recruited via GP invitations, 5.4% via the PR campaign, 3% via word-of-mouth, and 2.5% via third-sector organizations. Mean recruitment cost per participant was £78.47, with an extra £26.54 per recruit paid to GPs to cover research costs. CONCLUSIONS: REACT successfully recruited to target. Response rates were lower than initially predicted and recruitment timescales required adjustment. Written invitations from GPs were the most efficient method for recruiting older adults at risk of mobility disability. Targeted efforts could achieve more ethnically diverse cohorts. All trials should be required to provide recruitment data to enable evidence-based planning of future trials
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