Current research in oxidation-resistant carbon-carbon composites at NASA. Langley Research Center

The significant potential of carbon-carbon composites for high-temperature structural applications is well established. For hypersonic vehicle applications, desirable properties include low density, high specific strength and stiffness, low coefficients of thermal expansion, and retention of mechanical properties above 3000 F. A significant problem associated with carbon materials, however, is that they oxidize rapidly in air at temperatures above about 800 F, and therefore must be protected from oxidation. Successful development of effective methods of oxidation protection is key to the eventual utilization of carbon-carbon composites on hypersonic vehicles such as NASP. In this presentation, the basic elements of an oxidation-protection system are described. Results from oxidation-performance evaluations of state-of-the-art ACC-4 type material in simulated airframe vehicle environments (temperature, pressure, and time) conducted at NASA Langley are also presented. NASA Langley has an active research effort to improve the oxidation resistance of carbon-carbon materials for airframe structural and vehicle thermal protection applications. Conversion coating and sealant development research is highlighted

Lifetime predictions for the Solar Maximum Mission (SMM) and San Marco spacecraft

Lifetime prediction techniques developed by the Goddard Space Flight Center (GSFC) Flight Dynamics Division (FDD) are described. These techniques were developed to predict the Solar Maximum Mission (SMM) spacecraft orbit, which is decaying due to atmospheric drag, with reentry predicted to occur before the end of 1989. Lifetime predictions were also performed for the Long Duration Exposure Facility (LDEF), which was deployed on the 1984 SMM repair mission and is scheduled for retrieval on another Space Transportation System (STS) mission later this year. Concepts used in the lifetime predictions were tested on the San Marco spacecraft, which reentered the Earth's atmosphere on December 6, 1988. Ephemerides predicting the orbit evolution of the San Marco spacecraft until reentry were generated over the final 90 days of the mission when the altitude was less than 380 kilometers. The errors in the predicted ephemerides are due to errors in the prediction of atmospheric density variations over the lifetime of the satellite. To model the time dependence of the atmospheric densities, predictions of the solar flux at the 10.7-centimeter wavelength were used in conjunction with Harris-Priester (HP) atmospheric density tables. Orbital state vectors, together with the spacecraft mass and area, are used as input to the Goddard Trajectory Determination System (GTDS). Propagations proceed in monthly segments, with the nominal atmospheric drag model scaled for each month according to the predicted monthly average value of F10.7. Calibration propagations are performed over a period of known orbital decay to obtain the effective ballistic coefficient. Progagations using plus or minus 2 sigma solar flux predictions are also generated to estimate the despersion in expected reentry dates. Definitive orbits are compared with these predictions as time expases. As updated vectors are received, these are also propagated to reentryto continually update the lifetime predictions

“You gotta believe in something, something, something”: Evoking literacy lives as \u3cem\u3enostalgia for the future\u3c/em\u3e

We render in this theoretical inquiry, informed by empirical data, understandings of how preservice teachers’ literacy lives come into curricular considerations of future teaching and learning in the secondary English classroom. In doing this work, we wondered about the past, present, and future lives of teachers: how might we understand the teaching of English as profoundly nostalgic work? Building upon the notion of “nostalgia for the future”, and drawing across curriculum theory, literacy research, teaching and teacher education research, and the music of Frank Ocean, we attend to dangerous nostalgia in the current political moment, while also finding nostalgia for the future useful for ways in which through this considering we may envision and enact more just futures. We assert this nostalgia for the future, one necessarily prospective and not solely retrospective, as informed by written reflections authored by preservice teachers and teacher educators, and reflections of teaching activities in undergraduate and internship-year teacher-preparation courses. Ultimately we argue the concept affords a frame for making sense of the past while also orienting preservice teachers forward, building on that past critically for the work of imagining and constructing more just worlds for their future students

Characterization of a 5-eV neutral atomic oxygen beam facility

An experimental effort to characterize an existing 5-eV neutral atomic oxygen beam facility being developed at Princeton Plasma Physics Laboratory is described. This characterization effort includes atomic oxygen flux and flux distribution measurements using a catalytic probe, energy determination using a commercially designed quadrupole mass spectrometer (QMS), and the exposure of oxygen-sensitive materials in this beam facility. Also, comparisons were drawn between the reaction efficiencies of materials exposed in plasma ashers, and the reaction efficiencies previously estimated from space flight experiments. The results of this study show that the beam facility is capable of producing a directional beam of neutral atomic oxygen atoms with the needed flux and energy to simulate low Earth orbit (LEO) conditions for real time accelerated testing. The flux distribution in this facility is uniform to +/- 6 percent of the peak flux over a beam diameter of 6 cm

Prospective randomized controlled pilot study on the effects of almond consumption on skin lipids and wrinkles.

ObjectiveAlmonds are a rich source of fatty acids and antioxidants, and their supplementation is known to significantly modulate serum lipids. The effects of almond on the skin's lipid barrier and the appearance of wrinkles have not yet been elucidated. The aim of this study was to investigate the effects of almond consumption on facial sebum production and wrinkles.MethodsThis was a prospective, investigator-blinded, randomized controlled trial in which subjects consumed 20% of their daily energy consumption in either almonds or a calorie-matched snack for 16 weeks. This study was completed at the UC Davis Dermatology clinic. Participants were a volunteer sample of generally healthy postmenopausal females with Fitzpatrick skin types 1 and 2. A facial photograph and image analysis system was used to obtain standardized photographs and information on wrinkle width and severity at 0, 8, and 16 weeks. Measurements of transepidermal water loss and sebum production were also completed at 0, 8, and 16 weeks.ResultsFifty healthy postmenopausal females were recruited, 31 participants were enrolled, and 28 completed the study. Under photographic analysis, the almond group had significantly decreased wrinkle severity and width compared with the control group at 16 weeks (p < .02). Changes in skin barrier function were nonsignificant, measured by the transepidermal water loss (p = .65) between the almond and control groups relative to baseline after 16 weeks. No adverse effects were reported.ConclusionOur study demonstrates that daily almond consumption may reduce wrinkle severity in postmenopausal females to potentially have natural antiaging benefits

Variation in DNA methylation patterns is more common among maize inbreds than among tissues

Chromatin modifications, such as DNA methylation, can provide heritable, epigenetic regulation of gene expression in the absence of genetic changes. A role for DNA methylation in meiotically stable marking of repetitive elements and other sequences has been demonstrated in plants. Methylation of DNA is also proposed to play a role in development through providing a mitotic memory of gene expression states established during cellular differentiation. We sought to clarify the relative levels of DNA methylation variation among different genotypes and tissues in maize (Zea mays L.). We have assessed genomewide DNA methylation patterns in leaf, immature tassel, embryo, and endosperm tissues of two inbred maize lines: B73 and Mo17. There are hundreds of regions of differential methylation present between the two genotypes. In general, the same regions exhibit differential methylation between B73 and Mo17 in each of the tissues that were surveyed. In contrast, there are few examples of tissue-specific DNA methylation variation. Only a subset of regions with tissue-specific variation in DNA methylation show similar patterns in both genotypes of maize and even fewer are associated with altered gene expression levels among the tissues. Our data indicates a limited impact of DNA methylation on developmental gene regulation within maize

An Exploratory Study of the Effects of Aquatic Walking on Function and Muscle Activity in Knee Osteoarthritis: Part 2

This paper presents Part 2 of a study that investigated the effects of an 8-week (3x/week) underwater treadmill (UT) walking intervention on knee osteoarthritis (KOA) outcomes in 6 adults with KOA (62.7 ± 14.2 years). The Knee Outcome Survey (KOS) for activities of daily living and muscle activity during a 10-m walk and a 20 cm step down were measured before and after the intervention. The following KOS measures improved after the UT walking program (p \u3c 0.05; g \u3e 0.8): stiffness, swelling, weakness, walking, going up stairs, going downstairs, kneeling on the front of the knee, squatting, and sitting with the knee bent. Knee flexion excursion during stance of walking increased after the UT walking intervention (p = .01). Co-activation between the tibialis anterior and medial gastrocnemius decreased during the 20 cm step down (p = .04). The findings of this study support using the WWE as a model for UT walking interventions in KOA

An Exploratory Study of Aquatic Walking on Symptoms and Functional Limitations in Persons with Knee Osteoarthritis: Part 1

This paper represents Part 1 of a study that explored the effects of an underwater treadmill (UT) walking program on pain and function in adults with knee osteoarthritis (KOA). The Western Ontario & McMaster Universities Osteoarthritis Index (WOMAC), numerical rating scale (NRS), timed up-and-go (TUG), and 10-m walk were assessed in 6 adults (62.7 ±14.2 years) who participated in an 8-week (3x/wk) UT walking intervention based on the Arthritis Foundation’s Walk With Ease (WWE) program. Walking pace was self-selected, and walking duration of each session was increased from 10 to 45 minutes throughout the study. Knee pain and function were assessed pre-control (PRC), pre-intervention (PRI) and post-intervention (PST). NRS improved from PRC and PRI to PST (p = .03, d = .37). WOMAC subscale scores of pain, (d = .36); stiffness (d = .44); pain during daily activities (d = .41); and total scores (d = .42) improved (p \u3c .05) from PRC to PST. Self-selected walking speed increased concurrently with decreased knee pain (NRS) from PRI to PST. The results support the WWE as a model for an UT walking program for improving knee pain in KOA

Kepler Observations of Rapid Optical Variability in the BL Lac Object W2r192+42

We present the first Kepler monitoring of a strongly variable BL Lac, W2R1926+42. The light curve covers 181 days with approx. 0.2% errors, 30 minute sampling and >90% duty cycle, showing numerous delta-I/I > 25% flares over timescales as short as a day. The flux distribution is highly skewed and non-Gaussian. The variability shows a strong rms-flux correlation with the clearest evidence to date for non-linearity in this relation. We introduce a method to measure periodograms from the discrete autocorrelation function, an approach that may be well-suited to a wide range of Kepler data. The periodogram is not consistent with a simple power-law, but shows a flattening at frequencies below 7x10(exp -5) Hz. Simple models of the power spectrum, such as a broken power law, do not produce acceptable fits, indicating that the Kepler blazar light curve requires more sophisticated mathematical and physical descriptions than currently in use