Support for Higher Education: Perceptions of Selected University Administrators and Legislators in Tennessee

Excerpt:This quantitative study examined the perceptions of selected university administrators and legislators concerning levels of support for Tennessee public higher education

Applied Nanotechnology for Human Space Exploration

A viewgraph presentation describing nanotechnology for human space exploration is shown. The topics include: 1) NASA's Strategic Vision; 2) Exploration Architecture; 3) Future Exploration Mission Requirements Cannot be met with Conventional Materials; 4) Nanomaterials: Single Wall Carbon Nanotubes; 5) Applied Nanotechnology at JSC: Fundamentals to Applications; 6) Technology Readiness Levels (TRL); 7) Growth, Modeling, Diagnostics and Production; 8) Characterization: Purity, Dispersion and Consistency; 9) Processing; 10) Nanoelectronics: Enabling Technologies; 11) Applications for Human Space Exploration; 12) Exploration Life Support: Atmosphere Revitalization System; 13) Advanced and Exploration Life Support: Regenerable CO2 Removal; 14) Exploration Life Support: Water Recovery; 15) Advanced Life Support: Water Disinfection/Recovery; 16) Power and Energy: Supercapacitors and Fuel Cells; 17) Nanomaterials for EMI Shielding; 18) Active Radiation Dosimeter; 19) Advanced Thermal Protection System (TPS) Repair; 20) Thermal Radiation and Impact Protection (TRIPS); 21) Nanotechnology: Astronaut Health Management; 22) JSC Nanomaterials Group Collaborations

Enhanced Raman Microprobe Imaging of Single-Wall Carbon Nanotubes

We explore Raman microprobe capabilities to visualize single wall carbon nanotubes (SWCNTs). Although this technique is limited to a micron scale, we demonstrate that images of individual SWCNTs, bundles or their agglomerates can be generated by mapping Raman active elementary excitations. We measured the Raman response from carbon vibrations in SWCNTs excited by confocal scanning of a focused laser beam. Carbon vibrations reveal key characteristics of SWCNTs as nanotube diameter distribution (radial breathing modes, RBM, 100-300 cm(exp -1)), presence of defects and functional groups (D-mode, 1300-1350 cm(exp -1)), strain and oxidation states of SWCNTs, as well as metallic or semiconducting character of the tubes encoded in the lineshape of the G-modes at 1520-1600 cm(exp - 1). In addition, SWCNTs are highly anisotropic scatterers. The Raman response from a SWCNT is maximal for incident light polarization parallel to the tube axis and vanishing for perpendicular directions. We show that the SWCNT bundle shape or direction can be determined, with some limitations, from a set of Raman images taken at two orthogonal directions of the incident light polarization

On the Correlation between L Dwarf Optical and Infrared Variability and Radio Aurorae

Photometric variability attributed to cloud phenomena is common in L/T transition brown dwarfs. Recent studies show that such variability may also trace aurorae, suggesting that localized magnetic heating may contribute to observed brown dwarf photometric variability. We assess this potential correlation with a survey of 17 photometrically variable brown dwarfs using the Karl G. Jansky Very Large Array (VLA) at 4 -- 8 GHz. We detect quiescent and highly circularly polarized flaring emission from one source, 2MASS J17502484-0016151, which we attribute to auroral electron cyclotron maser emission. The detected auroral emission extends throughout the frequency band at $\sim$5 -- 25$\sigma$, and we do not detect evidence of a cutoff. Our detection confirms that 2MASS J17502484-0016151 hosts a magnetic field strength of $\geq$2.9 kG, similar to those of other radio-bright ultracool dwarfs. We show that H$\alpha$ emission continues to be an accurate tracer of auroral activity in brown dwarfs. Supplementing our study with data from the literature, we calculate the occurrence rates of quiescent emission in L dwarfs with low- and high-amplitude variability and conclude that high amplitude O/IR variability does not trace radio magnetic activity in L dwarfs.Comment: 26 pages, 5 figures, 6 table

On the Correlation between L Dwarf Optical and Infrared Variability and Radio Aurorae

Photometric variability attributed to cloud phenomena is common in L/T transition brown dwarfs. Recent studies show that such variability may also trace aurorae, suggesting that localized magnetic heating may contribute to observed brown dwarf photometric variability. We assess this potential correlation with a survey of 17 photometrically variable brown dwarfs using the Karl G. Jansky Very Large Array at 4–8 GHz. We detect quiescent and highly circularly polarized flaring emission from one source, 2MASS J17502484-0016151, which we attribute to auroral electron cyclotron maser emission. The detected auroral emission extends throughout the frequency band at ~5–25σ, and we do not detect evidence of a cutoff. Our detection confirms that 2MASS J17502484-0016151 hosts a magnetic field strength of ≥2.9 kG, similar to those of other radio-bright ultracool dwarfs. We show that Hα emission continues to be an accurate tracer of auroral activity in brown dwarfs. Supplementing our study with data from the literature, we calculate the occurrence rates of quiescent emission in L dwarfs with low- and high-amplitude variability and conclude that high-amplitude optical and infrared variability does not trace radio magnetic activity in L dwarfs

HAZMAT. V. The Ultraviolet and X-ray Evolution of K Stars

Knowing the high-energy radiation environment of a star over a planet's formation and evolutionary period is critical in determining if that planet is potentially habitable and if any biosignatures could be detected, as UV radiation can severely change or destroy a planet's atmosphere. Current efforts for finding a potentially habitable planet are focused on M stars, yet K stars may offer more habitable conditions due to decreased stellar activity and more distant and wider habitable zones (HZ). While M star activity evolution has been observed photometrically and spectroscopically, there has been no dedicated investigation of K-star UV evolution. We present the first comprehensive study of the near-UV, far-UV, and X-ray evolution of K stars. We used members of young moving groups and clusters ranging in age from 10 - 625 Myr combined with field stars and their archived GALEX UV and ROSAT X-ray data to determine how the UV and X-ray radiation evolve. We find that the UV and X-ray flux incident on a HZ planet is 5 - 50 times lower than that of HZ planets around early-M stars and 50 - 1000 times lower than those around late-M stars, due to both an intrinsic decrease in K dwarf stellar activity occurring earlier than for M dwarfs and the more distant location of the K dwarf HZ.Comment: 27 pages, 19 figure

Current Population Statistics Do Not Favor Photoevaporation over Core-Powered Mass Loss as the Dominant Cause of the Exoplanet Radius Gap

We search for evidence of the cause of the exoplanet radius gap, i.e. the dearth of planets with radii near $1.8\ R_\oplus$. If the cause was photoevaporation, the radius gap should trend with proxies for the early-life high-energy emission of planet-hosting stars. If, alternatively, the cause was core-powered mass loss, no such trends should exist. Critically, spurious trends between the radius gap and stellar properties arise from an underlying correlation with instellation. After accounting for this underlying correlation, we find no trends remain between the radius gap and stellar mass or present-day stellar activity as measured by near-UV emission. We dismiss the nondetection of a radius gap trend with near-UV emission because present-day near-UV emission is unlikely to trace early-life high-energy emission, but we provide a catalog of GALEX near-UV and far-UV emission measurements for general use. We interpret the nondetection of a radius gap trend with stellar mass by simulating photoevaporation with mass-dependent evolution of stellar high-energy emission. The simulation produces an undetectable trend between the radius gap and stellar mass under realistic sources of error. We conclude that no evidence, from this analysis or others in the literature, currently exists that clearly favors either photoevaporation or core powered mass loss as the primary cause of the exoplanet radius gap. However, repeating this analysis once the body of well-characterized $< 4\ R_\oplus$ planets has roughly doubled could confirm or rule out photoevaporation.Comment: 27 pages, 32 figures, accepted to Ap

Carbon Nanotube-Enhanced Carbon-Phenenolic Ablator Material

This viewgraph presentation reviews the use of PICA (phenolic impregnated carbon ablator) as the selected material for heat shielding for future earth return vehicles. It briefly reviews the manufacturing of PICA and the advantages for the use of heat shielding, and then explains the reason for using Carbon Nanotubes to improve strength of phenolic resin that binds carbon fibers together. It reviews the work being done to create a carbon nanotube enhanced PICA. Also shown are various micrographic images of the various PICA materials