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NASA NTRS1993

Engine materials characterization and damage monitoring by using x ray technologies

X ray attenuation measurement systems that are capable of characterizing density variations in monolithic ceramics and damage due to processing and/or mechanical testing in ceramic and intermetallic matrix composites are developed and applied. Noninvasive monitoring of damage accumulation and failure sequences in ceramic matrix composites is used during room-temperature tensile testing. This work resulted in the development of a point-scan digital radiography system and an in situ x ray material testing system. The former is used to characterize silicon carbide and silicon nitride specimens, and the latter is used to image the failure behavior of silicon-carbide-fiber-reinforced, reaction-bonded silicon nitride matrix composites. State-of-the-art x ray computed tomography is investigated to determine its capabilities and limitations in characterizing density variations of subscale engine components (e.g., a silicon carbide rotor, a silicon nitride blade, and a silicon-carbide-fiber-reinforced beta titanium matrix rod, rotor, and ring). Microfocus radiography, conventional radiography, scanning acoustic microscopy, and metallography are used to substantiate the x ray computed tomography findings. Point-scan digital radiography is a viable technique for characterizing density variations in monolithic ceramic specimens. But it is very limited and time consuming in characterizing ceramic matrix composites. Precise x ray attenuation measurements, reflecting minute density variations, are achieved by photon counting and by using microcollimators at the source and the detector. X ray computed tomography is found to be a unique x ray attenuation measurement technique capable of providing cross-sectional spatial density information in monolithic ceramics and metal matrix composites. X ray computed tomography is proven to accelerate generic composite component development. Radiographic evaluation before, during, and after loading shows the effect of preexisting volume flaws on the fracture behavior of composites. Results from one-, three-, five-, and eight-ply ceramic composite specimens show that x ray film radiography can monitor damage accumulation during tensile loading. Matrix cracking, fiber-matrix debonding, fiber bridging, and fiber pullout are imaged throughout the tensile loading of the specimens. In situ film radiography is found to be a practical technique for estimating interfacial shear strength between the silicon carbide fibers and the reaction-bonded silicon nitride matrix. It is concluded that pretest, in situ, and post-test x ray imaging can provide greater understanding of ceramic matrix composite mechanical behavior.

Baaklini, George Y.↗
NASA NTRS2016

The Lick AGN Monitoring Project 2011: Spectroscopic Campaign and Emission-line Light Curves

In the Spring of 2011 we carried out a 2.5 month reverberation mapping campaign using the 3 m Shane telescope at Lick Observatory, monitoring 15 low-redshift Seyfert 1 galaxies. This paper describes the observations, reductions and measurements, and data products from the spectroscopic campaign. The reduced spectra were fitted with a multicomponent model in order to isolate the contributions of various continuum and emission-line components. We present light curves of broad emission lines and the active galactic nucleus (AGN) continuum, and measurements of the broad Hβ line widths in mean and rms spectra. For the most highly variable AGNs we also measured broad H beta line widths and velocity centroids from the nightly spectra. In four AGNs exhibiting the highest variability amplitudes, we detect anticorrelations between broad H beta width and luminosity, demonstrating that the broad-line region "breathes" on short timescales of days to weeks in response to continuum variations. We also find that broad H beta velocity centroids can undergo substantial changes in response to continuum variations; in NGC 4593, the broad H beta velocity shifted by approximately 250 km s(exp -1) over a 1 month period. This reverberation-induced velocity shift effect is likely to contribute a significant source of confusion noise to binary black hole searches that use multi-epoch quasar spectroscopy to detect binary orbital motion. We also present results from simulations that examine biases that can occur in measurement of broad-line widths from rms spectra due to the contributions of continuum variations and photon-counting noise.

galaxies: Seyfert↗
NASA NTRS2005

Influence of Coronal Abundance Variations

The PI of this project was Jeff Scargle of NASA/Ames. Co-I's were Alma Connors of Eureka Scientific/Wellesley, and myself. Part of the work was subcontracted to Eureka Scientific via SAO, with Vinay Kashyap as PI. This project was originally assigned grant number NCC2-1206, and was later changed to NCC2-1350 for administrative reasons. The goal of the project was to obtain, derive, and develop statistical and data analysis tools that would be of use in the analyses of high-resolution, high-sensitivity data that are becoming available with new instruments. This is envisioned as a cross-disciplinary effort with a number of "collaborators" including some at SA0 (Aneta Siemiginowska, Peter Freeman) and at the Harvard Statistics department (David van Dyk, Rostislav Protassov, Xiao-li Meng, Epaminondas Sourlas, et al). We have developed a new tool to reliably measure the metallicities of thermal plasma. It is unfeasible to obtain high-resolution grating spectra for most stars, and one must make the best possible determination based on lower-resolution, CCD-type spectra. It has been noticed that most analyses of such spectra have resulted in measured metallicities that were significantly lower than when compared with analyses of high- resolution grating data where available (see, e.g., Brickhouse et al., 2000, ApJ 530,387). Such results have led to the proposal of the existence of so-called Metal Abundance Deficient, or "MAD" stars (e.g., Drake, J.J., 1996, Cool Stars 9, ASP Conf.Ser. 109, 203). We however find that much of these analyses may be systematically underestimating the metallicities, and using a newly developed method to correctly treat the low-counts regime at the high-energy tail of the stellar spectra (van Dyk et al. 2001, ApJ 548,224), have found that the metallicities of these stars are generally comparable to their photospheric values. The results were reported at the AAS (Sourlas, Yu, van Dyk, Kashyap, and Drake, 2000, BAAS 196, v32, #54.02), and at the conference on Statistical Challenges in Modem Astronomy (Sourlas, van Dyk, Kashyap, Drake, and Pease, 2003, SCMA 111, Eds. E.D.Feigelson, G.J.Babu, New York:Springer, p489-490). We also described the limitations of one of the most egregiously misused and misapplied statistical tests in astrophysical literature, the F-test for verifying model components (Protassov, van Dyk, Connors, Kashyap, and Siemiginowska, 2002, ApJ, 571,545). Indeed, a search through the ApJ archives turned up 170 papers in the 5 previous years that used the F-test explicitly in some form or the other, and with the vast majority of them not using it correctly! Indeed, looking at just 4 issues of the ApJ in 2001, we found 13 instances of its use, of which nine were demonstrably incorrect. Clearly, it is difficult to understate the importance of this issue. We also worked on speeding up Bayes Blocks and Sparse Bayes Blocks algorithms to make them more tractable for large searches. We also supported staistics students and postdocs in both explicit physics- model-based (spectra with tens of thousands of atomic lines) and "model-free" -- i.e. non-parametric or semi-parametric -- algorithms. Work on using more of the latter is just beginning; while using multi-scale methods for Poisson imaging has come to hition. In fact, "An Image Restoration Technique with Error Estimates", by D. Esch, A. Connors, M. Karovska, and D. van Dyk, was published by ApJ (Esch et a1.2004, ApJ, 610, 1213). The code has been delivered to M. Karovska for CXC; and is available for beta-testing upon request. The other large project we worked on was on the self-consistent modeling of logN-logs curves in the Poisson limit. logN-logs curves are a fundamental tool in the study of source populations, luminosity functions, and cosmological parameters. However, their determination is hampered by statistical effects such as the Eddington bias, incompleteness due to detection efficiency, faint source flux fluctuations, etc. We have develed a new and powerful method using the full Poisson machinery that allows us to model the logN-logs distribution of X-ray sources in a self-consistent manner. Because we properly account for all the above statistical effects, our modeling is valid over the full range of the data, and not just for strong sources, as is normally done. Using a Bayesian approach and modeling the fluxes with known functional forms such as simple or broken power-laws, and conditioning the expected photon counts on the fluxes, the background contamination, effective area, detector vignetting, and detection probability, we can delve deeply into the low counts regime and extend the usefulness of medium sensitivity surveys such as ChAMP by orders of magnitude. The built-in flexibility of the algorithm also allows a simultaneous analysis of multiple datasets. We have applied this analysis to a set a Chandra observations (Sourlas, Kashyap, Zezas, van Dyk, 2004, HEAD #8, #16.32)

Scargle, Jeffrey D.↗
NASA NTRSDate not supplied

Seed surface sanitization and persistence of E.coli through different tissues of ‘Red Robin’ Tomato (Solanum lycopersicum cv. Red Robin)

Seed surface sanitization via chemical processes removes/reduces microbes from the external surfaces of the seed and thereby could have an impact on the plants’ health or productivity. To determine the impact of seed surface sanitization on the plants’ microbiome, sanitized and unsanitized seeds from ‘Red Robin’ Tomato (Solanumlycopersicum cv. Red Robin) were exposed to Escherichia coli (E. coli) and grown in a controlled environment growth chamber simulating environmental conditions aboard the International Space Station (ISS). Plants were harvested at four intervals, days 11, 33,42 and 76 post-germination. Changes in the microbial communities of leaf, stem, root, and fruit because of E. coli exposure and the persistence of E. coli itself were investigated using aerobic plate count (APC), qPCR and 16S rRNA sequencing. It was determined that E. coli persisted for longer periods of time in plants from sanitized versus unsanitized seeds and was identified in root tissue more frequently than in leaf or stem tissue. E. coli was not detected in fruits raised from either sanitized or unsanitized seeds. The 16S rRNA sequencing showed dynamic changes in the abundance of members of the phylum Proteobacteria, Bacteroidetes, Actinobacteria, and Firmicutes in all tissue types studied. We observed minimal or no changes in the alpha diversity of leaf stem and fruit tissue with time, or between sanitized and unsanitized seeds. Roots showed significant differences in alpha diversity with time and seed sanitization status. Beta-diversity showed that time had more of an influence on all samples versus the E. coli treatment. Members of phyla Proteobacteria and Bacteroidetes were found to be differentially abundant across leaf, stem and root tissue. Our results indicated that the seed surface sanitization, although a requirement for sending seeds to space, might influence the developing microbiome. This research was funded by NASA’s Space Life and Physical Sciences Research and Applications.

Anirudha R Dixit↗
NASA NTRS1998

Osteoblastic phenotype of rat marrow stromal cells cultured in the presence of dexamethasone, beta-glycerolphosphate, and L-ascorbic acid

We investigated the effects of the time course of addition of osteogenic supplements dexamethasone, beta-glycerolphosphate, and L-ascorbic acid to rat marrow stromal cells, and the exposure time on the proliferation and differentiation of the cells. It was the goal of these experiments to determine the time point for supplement addition to optimize marrow stromal cell proliferation and osteoblastic differentiation. To determine this, two studies were performed; one study was based on the age of the cells from harvest, and the other study was based on the duration of exposure to supplemented medium. Cells were seen to proliferate rapidly at early time points in the presence and absence of osteogenic supplements as determined by 3H-thymidine incorporation into the DNA of replicating cells. These results were supported by cell counts ascertained through total DNA analysis. Alkaline phosphatase (ALP) activity and osteocalcin production at 21 days were highest for both experimental designs when the cells were exposed to supplemented medium immediately upon harvest. The ALP levels at 21 days were six times greater for cells maintained in supplements throughout than for control cells cultured in the absence of supplements for both studies, reaching an absolute value of 75 x 10(-7) micromole/min/cell. Osteocalcin production reached 20 x 10(-6) ng/cell at 21 days in both studies for cells maintained in supplemented medium throughout the study, whereas the control cells produced an insignificant amount of osteocalcin. These results suggest that the addition of osteogenic supplements to marrow-derived cells early in the culture period did not inhibit proliferation and greatly enhanced the osteoblastic phenotype of cells in a rat model.

Non-NASA Center↗
NASA NTRS1963

The Explorer XVI Micrometeoroid Satellite: Description and Preliminary Results for the Period December 16, 1962 Through January 13, 1963

Explorer XVI (1962 Beta Chi l) data that have been analyzed for the period between December 16, 1962 (launch date), and January 13, 1963, indicate that the orbit achieved was close to the predicted orbit. Ten punctures of annealed 0.001-inch-thick beryllium-copper have been used to determine a puncture rate of 0.035 per square foot per day in this material. One puncture of a 0.002-inch-thick sample has also occurred in this period. A tentative evaluation of the puncture rate for the 0.001-inch beryllium-copper in terms of the rate for an equivalent thickness of aluminum has been attempted, and the result has been compared with two different puncture rate estimates. The three micrometeoroid impact detecting systems are operating. Counting rates for the high- and low-sensitivity systems were close to anticipated values near the end of one week. Two of the 0.001-inch-steel-covered grid detectors have been punctured, but none of the 0.003- or 0.006-inch-steel-covered grid detectors have indicated punctures. One of the cadmium sulfide cells indicates three punctures of the 0.00025-inch Mylar cover. None of the 0.002- or 0.003-inch-copper-wire cards have indicated a break in the period covered. Telemetry temperatures were initially higher than expected although they remained well within operating limits. Sensor temperatures have remained within the expected bounds.

Micrometeoroid↗
NASA NTRSDate not supplied

Progress Towards the Design of a Natural Laminar Flow Wing for a Low-Boom Concept using CDISC

The X-59 is being developed to evaluate the ability to reduce sonic boom loudness to acceptable levels, with the ultimate goal of enabling supersonic flight overland. If successful, one of the future research challenges will be focused on reducing fuel burn. In this paper, Natural Laminar Flow (NLF) is proposed as a technology to decrease fuel burn for a low-boom configuration. This will require an evaluation of the compatibility of NLF wings for a low-boom configuration. As a first step towards this goal, the CATNLF method was employed using the CDISC design module to perform NLF design on an isolated wing from a low-boom configuration. The results show that the NLF wing features laminar flow over 46% of the wing upper surface, providing a potential 8.3 drag count reduction relative to the design with no laminar flow. Off-design analyses were additionally performed to evaluate the performance of the NLF wing for changes in angle of attack and Mach number. The results showed that the NLF wing offers a performance benefit over the entire range of off-design conditions considered, with most of the laminar flow maintained for near cruise conditions. Future work will consider the full configuration, which will enable an assessment of the impact of the NLF wing design on sonic boom loudness. Additionally, attachment line transition will be addressed, which was predicted to result in a loss of laminar flow on the inboard 50% span for this work. Finally, future research will focus on developing a method for effectively choosing the frequency-beta pairs used for the stability analysis to improve transition prediction and provide a more accurate estimate of the performance benefit.

Supersonic↗
NASA NTRSDate not supplied

Progress Towards the Design of a Natural Laminar Flow Wing for a Low-Boom Concept Using CDISC

The X-59 is being developed to evaluate the ability to reduce boom loudness to acceptable levels, with the ultimate goal of enabling supersonic flight overland. If successful, one of the future research challenges will be focused on reducing fuel burn. In this paper, Natural Laminar Flow (NLF) is proposed as a technology to decrease fuel burn for a low-boom configuration. This will require an evaluation of the compatibility of NLF wings for a low-boom configuration. As a first step towards this goal, the CATNLF method was employed using the CDISC design module to perform NLF design on an isolated wing from a low-boom configuration. The results show that the NLF wing features laminar flow over 46\% of the wing upper surface, providing a potential 8.3 drag count reduction relative to the design with no laminar flow. Off-design analyses were additionally performed to evaluate the performance of the NLF wing for changes in angle of attack and Mach number. The results showed that the NLF wing offers a performance benefit over the entire range of off-design conditions considered, with the majority of the laminar flow maintained for near cruise conditions. Future work will consider the full configuration, which will enable an assessment of the impact of the NLF wing design on sonic boom loudness. Additionally, attachment line transition will be addressed, which was predicted to result in a loss of laminar flow on the inboard 50\% span for this work. Finally, future research will focus on developing a method for effectively choosing the frequency-beta pairs used for the stability analysis to improve transition prediction and provide a more accurate estimate of the performance benefit.

Supersonic↗
NASA NTRS2014

Herschel/PACS Photometry of Transiting-Planet Host Stars with Candidate Warm Debris Disks

Dust in debris disks is produced by colliding or evaporating planetesimals, which are remnants of the planet formation process. Warm dust disks, known by their emission at less than or equal to 24 micrometer, are rare (4% of FGK main sequence stars) and especially interesting because they trace material in the region likely to host terrestrial planets, where the dust has a very short dynamical lifetime. Statistical analyses of the source counts of excesses as found with the mid-IR Wide Field Infrared Survey Explorer (WISE) suggest that warm-dust candidates found for the Kepler transiting-planet host-star candidates can be explained by extragalactic or galactic background emission aligned by chance with the target stars. These statistical analyses do not exclude the possibility that a given WISE excess could be due to a transient dust population associated with the target. Here we report Herschel/PACS 100 and 160 micron follow-up observations of a sample of Kepler and non-Kepler transiting-planet candidates' host stars, with candidate WISE warm debris disks, aimed at detecting a possible cold debris disk in any one of them. No clear detections were found in any one of the objects at either wavelength. Our upper limits confirm that most objects in the sample do not have a massive debris disk like that in beta Pic. We also show that the planet-hosting star WASP-33 does not have a debris disk comparable to the one around eta Crv. Although the data cannot be used to rule out rare warm disks around the Kepler planet-hosting candidates, the lack of detections and the characteristics of neighboring emission found at far-IR wavelengths support an earlier result suggesting that most of the WISE-selected IR excesses around Kepler candidate host stars are likely due to either chance alignment with background IR-bright galaxies and/or to interstellar emission.

Wide Field Infrared Survey Explorer (WISE)↗
NASA NTRS1994

The Seyfert II nature of the IRAS source FSC 10214+4724

We have observed the rest-frame optical and UV spectra of the luminous, high redshift Infrared Astronomy Satellite (IRAS) source FSC 10214+4724. We find the optical emission lines to be characterized by ratios similar to those found in Seyfert II galaxies. We support the conclusion of previous work that the UV emission lines are similar to those attributed to Active Galactic Nuclei (AGN) rather than to star formation. The ratio H alpha/H beta greater than or equal to 20 (2 sigma lower limit) implies substantial reddening of the narrow line region with A(sub V) greater than 5.5, sufficient to hide a broad line region in our H alpha observations. Given this large inferred reddening and the strength of the UV continuum and emission lines, we conclude (as have others) that simple screen models of reddening are not appropriate for this object. These properties are very similar to those of the infrared luminous galaxies at lower redshift, suggesting that FSC 10244+4724 is the luminous extreme of the same population. We also present H band (1.6 micrometer) imaging polarimetry observations and find that the rest-frame optical emission is unpolarized (P = 3.2% +/- 22.0%). This deep image of the field shows FSC 10214+4724 to possess an unresolved core, with several companions located within 10 sec of the point source. We find it unlikely that this group of objects is physically associated with FSC 10214+4724 at z = 2.3, and we argue that their magnitudes and colors are more consistant with those expected with those expected for galaxies in a foreground group. While galaxy number counts would suggest that such a projection has a low probability of being observed randomly, a foreground group might gravitational lens the z = 2.3 source, making such random statistics inappropriate, and contribute to the large observed luminosity of FSC 10214+4724. Comparison of H band images taken on two occasions one year apart show that FSC 10214+4724 had varied by 0.16 +/- 0.03 mag relative to a nearby star during that time. The UV-optical emission line spectra, the bright dereddened continuum magnitude (K less than 12) of the unresolved core, its extremely large bolometric luminosity, strong UV polarization, and possible variability all suggest that FSC 10214+4724 harbors an obscured AGN. Given that we observe no spectral features attributable to star formation, it appears either that star formation in FSC 10214+4724 is more highly obscured at optical and UV wavelengths than the narrow line region of the AGN, or that the AGN (rather than star formation) dominates the large luminosity of this object.

Elston, Richard↗
NASA NTRS1993

A petabyte size electronic library using the N-Gram memory engine

A model library containing petabytes of data is proposed by Triada, Ltd., Ann Arbor, Michigan. The library uses the newly patented N-Gram Memory Engine (Neurex), for storage, compression, and retrieval. Neurex splits data into two parts: a hierarchical network of associative memories that store 'information' from data and a permutation operator that preserves sequence. Neurex is expected to offer four advantages in mass storage systems. Neurex representations are dense, fully reversible, hence less expensive to store. Neurex becomes exponentially more stable with increasing data flow; thus its contents and the inverting algorithm may be mass produced for low cost distribution. Only a small permutation operator would be recalled from the library to recover data. Neurex may be enhanced to recall patterns using a partial pattern. Neurex nodes are measures of their pattern. Researchers might use nodes in statistical models to avoid costly sorting and counting procedures. Neurex subsumes a theory of learning and memory that the author believes extends information theory. Its first axiom is a symmetry principle: learning creates memory and memory evidences learning. The theory treats an information store that evolves from a null state to stationarity. A Neurex extracts information data without a priori knowledge; i.e., unlike neural networks, neither feedback nor training is required. The model consists of an energetically conservative field of uniformly distributed events with variable spatial and temporal scale, and an observer walking randomly through this field. A bank of band limited transducers (an 'eye'), each transducer in a bank being tuned to a sub-band, outputs signals upon registering events. Output signals are 'observed' by another transducer bank (a mid-brain), except the band limit of the second bank is narrower than the band limit of the first bank. The banks are arrayed as n 'levels' or 'time domains, td.' The banks are the hierarchical network (a cortex) and transducers are (associative) memories. A model Neurex was built and studied. Data were 50 MB to 10 GB samples of text, data base, and images: black/white, grey scale, and high resolution in several spectral bands. Memories at td, S(m(sub td)), were plotted against outputs of memories at td-1. S(m(sub td)) was Boltzman distributed, and memory frequencies exhibited self-organized criticality (SOC); i.e., 'l/f(sup beta)' after long exposures to data. Whereas output signals from level n may be encoded with B(sub output) = O(-log(2)f(sup beta)) bits, and input data encoded with B(sub input) = O((S(td)/S(td-1))(sup n)), B(sup output)/B(sub input) is much less than 1 always, the Neurex determines a canonical code for data and it is a lossless data compressor. Further tests are underway to confirm these results with more data types and larger samples.

Bugajski, Joseph M.↗