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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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All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

TOMOGRAPHY OF THE FERMI -LAT γ -RAY DIFFUSE EXTRAGALACTIC SIGNAL VIA CROSS CORRELATIONS WITH GALAXY CATALOGS

Building on our previous cross-correlation analysis (Xia et al. 2011) between the isotropic γ-ray background (IGRB) and different tracers of the large-scale structure of the universe, we update our results using 60 months of data from the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope (Fermi). For this study, we perform a cross-correlation analysis both in configuration and spherical harmonics space between the IGRB and objects that may trace the astrophysical sources of the IGRB: QSOs in the Sloan Digital Sky Survey (SDSS) DR6, the SDSS DR8 Main Galaxy Sample, luminous red galaxies (LRGs) in the SDSS catalog, infrared-selected galaxies in the Two Micron All Sky Survey (2MASS), and radio galaxies in the NRAO VLA Sky Survey (NVSS). The benefit of correlating the Fermi-LAT signal with catalogs of objects at various redshifts is to provide tomographic information on the IGRB, which is crucial in separating the various contributions and clarifying its origin. The main result is that, unlike in our previous analysis, we now observe a significant (>3.5σ) cross-correlation signal on angular scales smaller than 1° in the NVSS, 2MASS, and QSO cases and, at lower statistical significance (~3.0σ), with SDSS galaxies. The signal is stronger in two energy bands, E > 0.5 GeV and E > 1 GeV, but it is also seen at E > 10 GeV. No cross-correlation signal is detected between Fermi data and the LRGs. These results are robust against the choice of the statistical estimator, estimate of errors, map cleaning procedure, and instrumental effects. Finally, we test the hypothesis that the IGRB observed by Fermi-LAT originates from the summed contributions of three types of unresolved extragalactic sources: BL Lacertae objects (BL Lacs), flat spectrum radio quasars (FSRQs), and star-forming galaxies (SFGs). Finally, we find that a model in which the IGRB is mainly produced by SFGs ($72_{-37}^{+23}$% with 2σ errors), with BL Lacs and FSRQs giving a minor contribution, provides a good fit to the data. We also consider a possible contribution from misaligned active galactic nuclei, and we find that, depending on the details of the model and its uncertainty, they can also provide a substantial contribution, partly degenerate with the SFG one.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Testing the Recycled Gabbro Hypothesis for the Origin of “Ghost Plagioclase” Melt Signatures Using 87 Sr/ 86 Sr of Individual Olivine-Hosted Melt Inclusions From Hawai'i

Melt inclusions with large, positive Sr anomalies have been described in multiple tectonic settings, and the origins of this unusual geochemical feature are debated. Three origins have been proposed, all involving plagioclase as the source of the elevated Sr: (i) direct assimilation of plagioclase-rich lithologies, (ii) recycled lower oceanic gabbro in the mantle source, and (iii) shallow-level diffusive interaction between present day lower oceanic crust (i.e., plagioclase-bearing lithologies) and the percolating melt. A “ghost plagioclase” signature (i.e., a large, positive Sr anomaly without associated high Al 2 O 3 ) is present in melt inclusions from Mauna Loa. Here, we present new 87 Sr/ 86 Sr measurements of individual olivine-hosted melt inclusions from three Hawaiian volcanoes, Mauna Loa, Loihi, and Koolau. The data set includes a Mauna Loa melt inclusion with the highest reported Sr anomaly (or highest (Sr/Ce) N , which is 7.2) for Hawai'i. All melt inclusions have 87 Sr/ 86 Sr values within the range reported previously for the lavas from each volcano. Critically, the 87 Sr/ 86 Sr of the high (Sr/Ce) N melt inclusion lies within the narrow range of 87 Sr/ 86 Sr for Mauna Loa melts that lack high (Sr/Ce) N signatures. Therefore, to explain the high (Sr/Ce) N ratio of the ghost plagioclase signature using an ancient recycled gabbro, the gabbro-infused mantle source would have had to evolve, by chance, to have the same 87 Sr/ 86 Sr as the source of the Mauna Loa melts that lack a recycled gabbro (ghost plagioclase) signature. Alternatively, shallow-level diffusive interactions between Mauna Loa plagioclase-rich cumulates and a percolating mantle-derived melt provides a simpler explanation for the presence of the high (Sr/Ce) N Mauna Loa melts.

58 GEOSCIENCES↗
DOE OSTI2013

HARD X-RAY LAGS IN ACTIVE GALACTIC NUCLEI: TESTING THE DISTANT REVERBERATION HYPOTHESIS WITH NGC 6814

We present an X-ray spectral and temporal analysis of the variable active galaxy NGC 6814, observed with Suzaku during 2011 November. Remarkably, the X-ray spectrum shows no evidence for the soft excess commonly observed amongst other active galaxies, despite its relatively low level of obscuration, and is dominated across the whole Suzaku bandpass by the intrinsic powerlaw-like continuum. Despite this, we clearly detect the presence of a low-frequency hard lag of ∼1600 s between the 0.5-2.0 and 2.0-5.0 keV energy bands at greater than 6σ significance, similar to those reported in the literature for a variety of other active galactic nuclei (AGNs). At these energies, any additional emission from, e.g., a very weak, undetected soft excess, or from distant reflection must contribute less than 3% of the observed countrates (at 90% confidence). Given the lack of any significant continuum emission component other than the powerlaw, we can rule out models that invoke distant reprocessing for the observed lag behavior, which must instead be associated with this continuum emission. These results are fully consistent with a propagating fluctuation origin for the low-frequency hard lags, and with the interpretation of the high-frequency soft lags—a common feature seen in the highest quality AGN data with strong soft excesses—as reverberation from the inner accretion disk.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Testing the light:nutrient hypothesis: Insights into biofilm structure and function using metatranscriptomics

Aquatic biofilms are hotspots of biogeochemical activity due to concentrated microbial biomass (Battin, Kaplan, Newbold, & Hansen, 2003). However, biofilms are often considered a single entity when their role in biogeochemical transformations is assessed, even though these biofilms harbour functionally diverse microbial communities (Battin, Besemer, Bengtsson, Romani, & Packmann, 2016; Veach, Stegen, Brown, Dodds, & Jumpponen, 2016). Often overlooked are the biotic interactions among biofilm components that can affect ecosystem-scale processes such as primary production and nutrient cycling. These interactions are likely to be especially important under resource limitation. Light is a primary resource mediating algal photosynthesis and both phototrophic and heterotrophic production due to bacterial reliance on C-rich algal exudates (Cole, 1982). However, current understanding of function–structure linkages in streams has yet to unravel the relative degree of these microbial feedbacks under resource availability gradients. In this issue of Molecular Ecology, Bengtsson, Wagner, Schwab, Urich, and Battin (2018) studied stream biofilm responses to light availability to understand its impact across three domains of life. By integrating biogeochemical rate estimation and metatranscriptomics within a microcosm experiment, they were able to link primary production and nutrient uptake rates to algal and bacterial metabolic processes and specify what taxa contributed to gene expression. Under low light, diatoms and cyanobacteria upregulated photosynthetic machinery and diatom-specific chloroplast rRNA suggesting heightened transcriptional activity under light limitation to maintain phototrophic energy demands. Under high light, heterotrophic bacteria upregulated mRNAs related to phosphorous (P) metabolism while biofilm P uptake increased indicating high bacterial-specific P demand when algal biomass was high. Together, these results indicate that biogeochemical function is mediated by complex microbial interactions across trophic levels.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2016

Testing the binary trigger hypothesis in FUors

We present observations of three FU Orionis objects (hereafter, FUors) with nonredundant aperture-mask interferometry at 1.59 μm and 2.12 μm that probe for binary companions on the scale of the protoplanetary disk that feeds their accretion outbursts. We do not identify any companions to V1515 Cyg or HBC 722, but we do resolve a close binary companion to V1057 Cyg that is at the diffraction limit (ρ=58.3±1.4 mas or 30 ± 5 au) and currently much fainter than the outbursting star (ΔK{sup ′}=3.34±0.10 mag). Given the flux excess of the outbursting star, we estimate that the mass of the companion (M∼0.25M{sub ⊙}) is similar to or slightly below that of the FUor itself, and therefore it resembles a typical T Tauri binary system. Our observations only achieve contrast limits of ΔK{sup ′}∼4 mag, and hence we are only sensitive to companions that were near or above the pre-outburst luminosity of the FUors. It remains plausible that FUor outbursts could be tied to the presence of a close binary companion. However, we argue from the system geometry and mass reservoir considerations that these outbursts are not directly tied to the orbital period (i.e., occurring at periastron passage), but instead must only occur infrequently.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1978

A test of the comet hypothesis of the Tunguska Meteor Fall - Nature of the meteor 'thermal' explosion paradox

The hypothesis that a comet was responsible for the Tunguska Meteor Fall is rejected because the hypothesis does not seem to account for the intense terminal spherical shock. A porous meteoroid model is proposed, and an analysis indicates that an entity of this type might produce an aerodynamic heat flux large enough to account for the terminal meteor explosion. It is suggested that the presence of olivine and of highly irregular macrostructure in meteors might indicate the presence of some porosity. For a highly porous meteoroid, it is postulated that during entry into the atmosphere the aerodynamic heat transfer at its external or pore walls would become so intensified as to cause either complete ablation with popping or a solid-liquid-vapor phase transition accompanied by an explosion.

Liu, V. C.↗
NASA NTRS1984

Tests of the lunar hypothesis

The concept that the Moon was fissioned from the Earth after core separation is the most readily testable hypothesis of lunar origin, since direct comparisons of lunar and terrestrial compositions can be made. Differences found in such comparisons introduce so many ad hoc adjustments to the fission hypothesis that it becomes untestable. Further constraints may be obtained from attempting to date the volatile-refractory element fractionation. The combination of chemical and isotopic problems suggests that the fission hypothesis is no longer viable, and separate terrestrial and lunar accretion from a population of fractionated precursor planetesimals provides a more reasonable explanation.

Taylor, S. R.↗
NASA NTRS2007

Real-time Affective Indices of Potential CRM Breakdown: Qualitative Testing of an Operational Hypothesis

This viewgraph presentation begins by showing several cases where poor crew resource management (CRM) resulted in aircraft accidents. The presenter reviews the emotional states that are present in a situation that frequently leads to an accident. The operational answer suggested is given as an acronym: PACE, which stand for Probe, Alert, Challenge, Emergency Action.

Dickerson, Mark↗
NASA NTRS1998

Tests of the Giant Impact Hypothesis

The giant impact hypothesis has gained popularity as a means of explaining a volatile-depleted Moon that still has a chemical affinity to the Earth. As Taylor's Axiom decrees, the best models of lunar origin are testable, but this is difficult with the giant impact model. The energy associated with the impact would be sufficient to totally melt and partially vaporize the Earth. And this means that there should he no geological vestige of Barber times. Accordingly, it is important to devise tests that may be used to evaluate the giant impact hypothesis. Three such tests are discussed here. None of these is supportive of the giant impact model, but neither do they disprove it.

Jones, J. H.↗
DOE OSTI2016

Contemporary Trends in Radiation Oncology Resident Research

Purpose: To test the hypothesis that recent resident research productivity might be different than a decade ago, and to provide contemporary information about resident scholarly activity. Methods and Materials: We compiled a list of radiation oncology residents from the 2 most recent graduating classes (June 2014 and 2015) using the Association of Residents in Radiation Oncology annual directories. We queried the PubMed database for each resident's first-authored publications from postgraduate years (PGY) 2 through 5, plus a 3-month period after residency completion. We abstracted corresponding historical data for 2002 to 2007 from the benchmark publication by Morgan and colleagues (Int J Radiat Oncol Biol Phys 2009;74:1567-1572). We tested the null hypothesis that these 2 samples had the same distribution for number of publications using the Wilcoxon rank-sum test. We explored the association of demographic factors and publication number using multivariable zero-inflated Poisson regression. Results: There were 334 residents publishing 659 eligible first-author publications during residency (range 0-17; interquartile range 0-3; mean 2.0; median 1). The contemporary and historical distributions were significantly different (P<.001); contemporary publication rates were higher. Publications accrued late in residency (27% in PGY-4, 59% in PGY-5), and most were original research (75%). In the historical cohort, half of all articles were published in 3 journals; in contrast, the top half of contemporary publications were spread over 10 journals—most commonly International Journal of Radiation Oncology • Biology • Physics (17%), Practical Radiation Oncology (7%), and Radiation Oncology (4%). Male gender, non-PhD status, and larger residency size were associated with higher number of publications in the multivariable analysis. Conclusion: We observed an increase in first-author publications during training compared with historical data from the mid-2000s. These contemporary figures may be useful to medical students considering radiation oncology, current residents, training programs, and prospective employers.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2026

Potential Applications of Quantum Computing at Los Alamos National Laboratory, v0.3.0

Since the scientific revolution in the 16th and 17th centuries, the process of scientific discovery has followed an iterative feedback process of observation, hypothesis development and testing with physical experiments, which is widely referred to as the scientific method. This process remained largely unchanged until the middle of the 20th century, when the emergence of digital computers empowered scientist to build and inspect detailed simulations of physical phenomena. Over the last century, computational tools have transformed modern approaches to scientific discovery by enabling fast and affordable hypothesis testing before physical experiments are conducted, shown in Figure 1-1. Some notable examples include: global climate forecasts to understand how the environment may change over decades [130]; modeling the behavior of plasma to design fusion reactors [59]; and understanding the behavior of molecules in biological processes [161, 223].

36 MATERIALS SCIENCE↗
NASA NTRS2011

Gravito-Inertial Force Resolution in Perception of Synchronized Tilt and Translation

Natural movements in the sagittal plane involve pitch tilt relative to gravity combined with translation motion. The Gravito-Inertial Force (GIF) resolution hypothesis states that the resultant force on the body is perceptually resolved into tilt and translation consistently with the laws of physics. The purpose of this study was to test this hypothesis for human perception during combined tilt and translation motion. EXPERIMENTAL METHODS: Twelve subjects provided verbal reports during 0.3 Hz motion in the dark with 4 types of tilt and/or translation motion: 1) pitch tilt about an interaural axis at +/-10deg or +/-20deg, 2) fore-aft translation with acceleration equivalent to +/-10deg or +/-20deg, 3) combined "in phase" tilt and translation motion resulting in acceleration equivalent to +/-20deg, and 4) "out of phase" tilt and translation motion that maintained the resultant gravito-inertial force aligned with the longitudinal body axis. The amplitude of perceived pitch tilt and translation at the head were obtained during separate trials. MODELING METHODS: Three-dimensional mathematical modeling was performed to test the GIF-resolution hypothesis using a dynamical model. The model encoded GIF-resolution using the standard vector equation, and used an internal model of motion parameters, including gravity. Differential equations conveyed time-varying predictions. The six motion profiles were tested, resulting in predicted perceived amplitude of tilt and translation for each. RESULTS: The modeling results exhibited the same pattern as the experimental results. Most importantly, both modeling and experimental results showed greater perceived tilt during the "in phase" profile than the "out of phase" profile, and greater perceived tilt during combined "in phase" motion than during pure tilt of the same amplitude. However, the model did not predict as much perceived translation as reported by subjects during pure tilt. CONCLUSION: Human perception is consistent with the GIF-resolution hypothesis even when the gravito-inertial force vector remains aligned with the body during periodic motion. Perception is also consistent with GIF-resolution in the opposite condition, when the gravito-inertial force vector angle is enhanced by synchronized tilt and translation.

Wood, Scott J.↗
NASA NTRS1973

Motivation in vigilance - A test of the goal-setting hypothesis of the effectiveness of knowledge of results.

This study tested the prediction, derived from the goal-setting hypothesis, that the facilitating effects of knowledge of results (KR) in a simple vigilance task should be related directly to the level of the performance standard used to regulate KR. Two groups of Ss received dichotomous KR in terms of whether Ss response times (RTs) to signal detections exceeded a high or low standard of performance. The aperiodic offset of a visual signal was the critical event for detection. The vigil was divided into a training phase followed by testing, during which KR was withdrawn. Knowledge of results enhanced performance in both phases. However, the two standards used to regulate feedback contributed little to these effects.

Warm, J. S.↗
DOE OSTI2017

Testing the Kerr Black Hole Hypothesis Using X-Ray Reflection Spectroscopy

We present the first X-ray reflection model for testing the assumption that the metric of astrophysical black holes is described by the Kerr solution. We employ the formalism of the transfer function proposed by Cunningham. The calculations of the reflection spectrum of a thin accretion disk are split into two parts: the calculation of the transfer function and the calculation of the local spectrum at any emission point in the disk. The transfer function only depends on the background metric and takes into account all the relativistic effects (gravitational redshift, Doppler boosting, and light bending). Our code computes the transfer function for a spacetime described by the Johannsen metric and can easily be extended to any stationary, axisymmetric, and asymptotically flat spacetime. Transfer functions and single line shapes in the Kerr metric are compared to those calculated from existing codes to check that we reach the necessary accuracy. We also simulate some observations with NuSTAR and LAD/eXTP and fit the data with our new model to show the potential capabilities of current and future observations to constrain possible deviations from the Kerr metric.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

PIP4Kγ as a potential target for Huntington's disease

Phosphoinositide lipids provide spatial and temporal regulation of cell signaling and membrane traffic. The PI5P‐4‐kinase family is one of the less studied phosphoinositide lipid kinases. These enzymes catalyze the conversion of phosphatidylinositol 5‐phosphate to phosphatidylinositol 4,5‐bis phosphate. A recent study by Vicinanza et al., a suggested that depletion of the PI5P‐4‐kinase, PIP4Kγ promotes a non‐canonical autophagy pathway. Moreover, this depletion reduced the presence of huntingtin‐exon1‐polyglutamine aggregates. Expression of exon1 of huntingtin with an extended polyglutamine tract is a model for huntingtin protein aggregates. To further test the hypothesis that PIP4Kγ is a potential target to reduce huntingtin aggregates, we tested the depletion of PIP4Kγ in cell culture models that express full length mutant huntingtin (mHtt). We determined that depletion of PIP4Kγ, but not PIP4Kα or PIP4Kβ, lowers the levels of mHtt in patient fibroblasts and in immortalized Hdh Q111 mouse striatal neurons. We show that PIP4Kγ‐dependent depletion of mHtt requires lysosomal function because the depletion is blocked by the lysosomal inhibitor, bafilomycin A1. Moreover, we show that depletion of PIP4Kγ increases autophagic flux, as measured by an increase in LC3‐II levels by western blot analysis and an increase in LC3‐II puncta by microscopy. Our studies suggest that PIP4kγ should be further pursued as a target for Huntington's disease. Support or Funding Information This work was supported by AHA postdoctoral fellowship 14POST20480137 (Sai Srinivas Panapakkam Giridharan), NIH grants R01GM050403 and NS064015 (Lois S Weisman) and by HSS funding 1R03MH084839 (Juan Marugan)

Giridharan, Sai Srinivas Panapakkam↗
DOE OSTI2016

Nonequilibrium Physics and Phase-Field Modeling of Multiphase Flow in Porous Media

The overarching goal of this project was to develop a new continuum theory of multiphase flow in porous media. The theory follows a phase-field modeling approach, and therefore has a sound thermodynamical basis. It is a phenomenological theory in the sense that its formulation is driven by macroscopic phenomena, such as viscous instabilities during multifluid displacement. The research agenda was organized around a set of hypothesis on hitherto unexplained behavior of multiphase flow. All these hypothesis are nontrivial, and testable. Indeed, a central aspect of the project was testing each hypothesis by means of carefully-designed laboratory experiments, therefore probing the validity of the proposed theory. The proposed research places an emphasis on the fundamentals of flow physics, but is motivated by important energy-driven applications in earth sciences, as well as microfluidic technology.

42 ENGINEERING↗
DOE OSTI2019

Bacterial Tradeoffs in Growth Rate and Extracellular Enzymes

Like larger organisms, bacteria possess traits, or phenotypic characteristics, that influence growth and impact ecosystem processes. Still, it remains unclear how these traits are organized across bacterial lineages. Using 49 bacterial strains isolated from leaf litter in Southern California, we tested the hypothesis that bacterial growth rates trade off against extracellular enzyme investment. We also tested for phylogenetic conservation of these traits under high and low resource conditions represented, respectively, by Luria broth (LB) and a monomer-dominated medium extracted from plant litter. In support of our hypotheses, we found a negative correlation between the maximum growth rate and the total activity of carbon-, nitrogen-, and phosphorus-degrading extracellular enzymes. However, this tradeoff was only observed under high resource conditions. We also found significant phylogenetic signal in maximum growth rate and extracellular enzyme investment under high and low resource conditions. Driven by our bacterial trait data, we proposed three potential life history strategies. Resource acquisition strategists invest heavily in extracellular enzyme production. Growth strategists invest in high growth rates. Bacteria in a third category showed lower potential for enzyme production and growth, so we tentatively classified them as maintenance strategists that may perform better under conditions we did not measure. These strategies were related to bacterial phylogeny, with most growth strategists belonging to the phylum Proteobacteria and most maintenance and resource acquisition strategists belonging to the phylum Actinobacteria. By accounting for extracellular enzyme investment, our proposed life history strategies complement existing frameworks, such as the copiotroph-oligotroph continuum and Grime’s competitorstress tolerator-ruderal triangle. Our results have biogeochemical implications because allocation to extracellular enzymes versus growth or stress tolerance can determine the fate and form of organic matter cycling through surface soil.

59 BASIC BIOLOGICAL SCIENCES↗