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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

High-peak-power low-threshold AlGaAs/GaAs stripe laser diodes on Si substrates grown by migration-enhanced molecular beam epitaxy

A high-peak-power low-threshold AlGaAs/GaAs double-heterostructure stripe laser diode on Si substrats, grown by hybrid migration-enhanced molecular beam epitaxy (MEMBE) and metalorganic chemical vapor deposition (MOCVD) has been demonstrated for the first time. These devices showed the highest peak powers of up to 184 mW per facet reported so far for double-heterostructure stripe laser diodes on Si substrates, room-temperature pulsed threshold currents as low as 150 mA, and differential quantum efficiencies as high as 30 percent without mirror facet coating. An intrinsic threshold current density has been estimated to be about 2 kA/sq cm when taking current spreading and lateral diffusion effects into account. Low dislocation density shows that MEMBE can be a useful method to grow high-quality GaAs and AlGaAs/GaAs layers on Si substrates by combining with MOCVD.

Kim, Jae-Hoon↗
NASA NTRS1993

Striped tape arrays

The topics are presented in viewgraph form and include the following: introduction to striping; applications; tape technologies; robots; access times; striping options and issues; and reliability issues.

Drapeau, Ann L.↗
NASA NTRS2017

Perfluorinated Alkyl Acids and Fecundity Assessment in Striped Mullet (Mugil Cephalus) at Merritt Island National Wildlife Refuge

This study investigated wild caught Striped mullet (Mugil cephalus) at Merritt Island National Wildlife Refuge (MINWR) for levels of 15 perfluoroalkyl acids (PFAAs) in tandem with fecundity measurements (n 42) and oocyte developmental stages (n 128). PFAAs measurements were undertaken for liver (n 128), muscle (n 49), and gonad (n 10). No significant negative impacts of liver PFAA burden on wild-caught, mullet fecundity endpoints are observed in this study; however, changes in PFAAs are seen in the liver as mullet progress through different sub-stages of oocyte development. Of the PFAAs with significant changes by sub-stage of oocyte development, the carboxylic acids (perfluorooctanoic acid, perfluorononanoic acid, and perfluorotridecanoic acid) increase in the liver with increasing sub-stage while the sulfonic acid and its precursor (perfluorooctanesulfonic acid (PFOS) and perfluorooctanesulfonamide, respectively) decrease in the liver with increasing stage of oocyte development. This is a unique find and suggests PFAAs change location of compartmentalization as mullet progress towards spawning. Investigations also revealed higher than expected median muscle and gonad levels of PFOS in Striped mullet collected at MINWR (9.01 ngg and 80.2 ngg, respectively).

Jacqueline T Bangma↗
NASA NTRS2020

Striped Mullet Migration Patterns in the Indian River Lagoon: A Network Analysis Approach to Spatial Fisheries Management

Striped mullet (Mugil cephalus) are numerically abundant forage fish, highly valuable as prey and commercially valuable to humans. From September to December, mullet in the Indian River Lagoon (IRL), Florida undergo an annual migration from inshore foraging habitats to oceanic spawning sites. However, their migratory pathways, in particular their intra-estuarine movement pathways, remain unknown. To address this knowledge gap, we utilized passive acoustic telemetry to assess the movement patterns of M. cephalus within the IRL. Thirty-two fish were tagged, generating usable tracks from 18 individuals. The mean (±s.d.) time that fish were detected in the array was ~38 ± 90 days, with the longest at 444 days. We also document the first evidence of skipped spawning in M. cephalus inhabiting waters of the southeastern United States. These data suggest impoundments around the Merritt Island National Wildlife Refuge appear to serve as important refugia for striped mullet while the Banana and Indian Rivers act as corridors during their inshore migratory movements. Through spatial fisheries management, high value habitat and connective elements utilized by mullet and other vital forage fish may be identified, to benefit both natural and human dynamics in estuarine systems.

Acoustic telemetry↗
NASA NTRS1981

AlGaAs/GaAs transverse junction stripe lasers with distributed feedback

Transverse junction stripe (TJS) lasers with periodic feedback were fabricated in two geometries. An interferometric and wet chemical etching technique was used to create a feedback grating across the entire pumping region for the distributed feedback (DFB) TJS laser and to create the separate distributed Bragg reflectors/DBR) for the TJS/DBR laser. The TJS/DFB laser was a double heterostructure device grown by liquid phase epitaxy (LPE) and had a third order grating etched in the top ALO.2GaO.8As layer. The grating was buried by growing an ALO.35GaO.65As layer on the grating by metal organic chemical vapor deposition (MO-CVD). The TJS/DBR laser was also fabricated in an LPE double heterostructure. The top AlGaAs layer was thinned to 0.1 micron over more than half of the laser so that the grating would be close to the GaAs active layer and optical field. Single mode operation in both configurations was obtained. The thermal shift of the laser wavelength in both cases was less than 1 Angstrom/deg K, compared to the 3 Angstrom/deg K shift of the spontaneous emission peak.

Hafich, M. J.↗
NASA NTRS1990

High-power operation of highly reliable narrow stripe pseudomorphic single quantum well lasers emitting at 980 nm

Ridge waveguide pseudomorphic InGaAs/GaAs/AlGaAs single-quantum-well lasers exhibiting record high quantum efficiencies and high output power densities (105 mW per facet from a 6 micron wide stripe) at a lasing wavelength of 980 nm are discussed that were fabricated from a graded index separate confinement heterostructure grown by molecular beam epitaxy. Life testing at an output power of 30 mW per uncoated facet reveals a slow gradual degradation during the initial 500 h of operation after which the operating characteristics of the lasers become stable. The emission wavelength, the high output power, and the fundamental lateral mode operation render these lasers suitable for pumping Er3+-doped fiber amplifiers.

Larsson, A.↗
NASA NTRS1987

Riblets for Stars and Stripes

Stars and Stripes racing yacht brought the American's Cup back to the United States. Originating from NASA's drag reduction technology, the boats "secret weapon" was that the hull's underside was coated with riblets. Riblets are small, barely visible grooves on the surface of an airplane intended to reduce skin friction by smoothing the turbulent airflow next to the skin. Grooves are V-shaped with the angle pointing in the direction of the airflow. No deeper than a scratch, they have a pronounced beneficial influence on air turbulence. *No longer commercially available.

Source record↗
NASA NTRS1994

The beetle Tribolium castaneum has a fushi tarazu homolog expressed in stripes during segmentation

The genetic control of embryonic organization is far better understood for the fruit fly Drosophila melanogaster than for any other metazoan. A gene hierarchy acts during oogenesis and embryogenesis to regulate the establishment of segmentation along the anterior-posterior axis, and homeotic selector genes define developmental commitments within each parasegmental unit delineated. One of the most intensively studied Drosophila segmentation genes is fushi tarazu (ftz), a pair-rule gene expressed in stripes that is important for the establishment of the parasegmental boundaries. Although ftz is flanked by homeotic selector genes conserved throughout the metazoa, there is no evidence that it was part of the ancestral homeotic complex, and it has been unclear when the gene arose and acquired a role in segmentation. We show here that the beetle Tribolium castaneum has a ftz homolog located in its Homeotic complex and expressed in a pair-rule fashion, albeit in a register differing from that of the fly gene. These and other observations demonstrate that a ftz gene preexisted the radiation of holometabolous insects and suggest that it has a role in beetle embryogenesis which differs somewhat from that described in flies.

NASA Discipline Developmental Biology↗
NASA NTRS2016

Weak-Lensing Mass Calibration of the Atacama Cosmology Telescope Equatorial Sunyaev-Zeldovich Cluster Sample with the Canada-France-Hawaii Telescope Stripe 82 Survey

Mass calibration uncertainty is the largest systematic effect for using clustersof galaxies to constrain cosmological parameters. We present weak lensing mass measurements from the Canada-France-Hawaii Telescope Stripe 82 Survey for galaxy clusters selected through their high signal-to-noise thermal Sunyaev-Zeldovich (tSZ) signal measured with the Atacama Cosmology Telescope (ACT). For a sample of 9 ACT clusters with a tSZ signal-to-noise greater than five, the average weak lensing mass is (4.8 plus or minus 0.8) times 10 (sup 14) solar mass, consistent with the tSZ mass estimate of (4.7 plus or minus 1.0) times 10 (sup 14) solar mass, which assumes a universal pressure profile for the cluster gas. Our results are consistent with previous weak-lensing measurements of tSZ-detected clusters from the Planck satellite. When comparing our results, we estimate the Eddington bias correction for the sample intersection of Planck and weak-lensing clusters which was previously excluded.

Battaglia, N.↗
NASA NTRS2020

Caltech–NRAO Stripe 82 Survey (CNSS). III. The First Radio-discovered Tidal Disruption Event, CNSS J0019+00

We present the discovery of a nuclear transient with the Caltech–NRAO Stripe 82 Survey (CNSS), a dedicated radio transient survey carried out with the Karl G.Jansky Very Large Array (VLA). This transient, CNSS J001947.3+003527, exhibited a turn-on over a timescale of <~1 yr, increasing in flux density at 3 GHz from <0.14 mJy in 2014 February to 4.4 ± 0.1 mJy in 2015 March, reaching a peak luminosity of 5 x 10^28 erg s-1 Hz-1 around 2015 October. The association of CNSS J0019+00 with the nucleus (Gaia and our very-long baseline interferometry positions are consistent to within 1 pc) of a nearby S0 Seyfert galaxy at 77 Mpc, together with the radio spectral evolution, implies that this transient is most likely a tidal disruption event (TDE). Our equipartition analysis indicates the presence of a ∼15,000 km s−1 outflow, having energy ∼1049 erg. We derive the radial density profile for the circumnuclear material in the host galaxy to be proportional to R−2.5. All of these properties suggest resemblance with radio-detected thermal TDEs like ASASSN-14li and XMMSL1 J0740-85. No significant X-ray or optical emission is detected from CNSS J0019+00, although this may simply be due to the thermal emission being weak during our late-time follow-up observations. From the CNSS survey we have obtained the first unbiased measurement of the rate of radio TDEs, R(>500μJy) of about 2 × 10−3 deg−2, or equivalently a volumetric rate of about 10 Gpc−3 yr−1. This rate implies that all-sky radio surveys such as the VLA Sky Survey and those planned with ASKAP, will find many tens of radio TDEs over the next few years.

M M Anderson↗