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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 703 records · Page 39
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Developing a radiation-aging model for polymeric foam cushions

Motivation: A major component of the A&L constitutive modeling effort over the last couple of years has involved developing a thermal aging model for foam cushions. Through extensive studies of uniaxial compression data, we have established that the Ogden N = 2 Hyperfoam in conjunction with the Tobolsky two-network model [Ref. 4] provides an accurate theoretical framework to describe the results, both for the traditional (stochastic) as well as the AM (3D-printed) foam pads. The results display numerical accuracy over a wide range of compression levels, from low to moderate up to slightly over 90% of lock-up. Over the last few weeks we have been exploring radiation aging data on a specific 3D printed foam, i.e., SE1700 AM FCT foam, to see if the Ogden + Tobolsky model can explain such data as well, and if so, how the various model parameters change as a function of dosage. As this report shows, the answer is indeed yes. We find that the modulus of the second (i.e., induced network) increases nearly proportionally with the radiation dosage, with a smaller sub-linear decrease in the primary shear modulus of the original network. This is consistent with the interpretation that exposure to energetic gamma-radiation is dominated by the formation of new cross-links. Significance: An important goal of A&L modeling efforts is to develop a fully age-aware materials model that can describe the joint effects of commonly present aging drivers like temperature, radiation, humidity, etc. Such a model is necessary to assess the lifetime of essential components like polymeric foams and rubber pads.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Irradiation Effects on Reactor Concrete Structures

As the US Light Water Reactor (LWR) fleet ages, irradiation and environmental effects may degrade concrete structures within the reactor cavity of nuclear power plants (NPPs). Concrete components provide structural support and serve as a containment barrier and radiation shield. Among the most important constituents of concrete are the aggregates and cement paste phases. These two phases deteriorate due to different factors, aggregates swell due to the presence of neutron irradiation, while the cement may lose water due to gamma-ray-induced hydrolysis. The authors will present a series of results from different characterization techniques (i.e. TEM, XRD, XRF, EBSD and ellipsometry) and Fast Fourier Transform (FFT) micro-mechanical simulations using MOSAIC that demonstrates the effects of irradiation, moisture, temperature, and constraint on reactor cavity concrete (RCC). The development of new numerical techniques and understanding of the irradiation effects in concrete are crucial for the assessment and life extension of the NPPs.

Arregui Mena, Jose'↗
DOE OSTI2015

Distribution Atlas of Proliferating Bone Marrow in Non-Small Cell Lung Cancer Patients Measured by FLT-PET/CT Imaging, With Potential Applicability in Radiation Therapy Planning

Purpose: Proliferating bone marrow is exquisitely sensitive to ionizing radiation. Knowledge of its distribution could improve radiation therapy planning to minimize unnecessary marrow exposure and avoid consequential prolonged myelosuppression. [18F]-Fluoro-3-deoxy-3-L-fluorothymidine (FLT)–positron emission tomography (PET) is a novel imaging modality that provides detailed quantitative images of proliferating tissues, including bone marrow. We used FLT-PET imaging in cancer patients to produce an atlas of marrow distribution with potential clinical utility. Methods and Materials: The FLT-PET and fused CT scans of eligible patients with non-small cell lung cancer (no distant metastases, no prior cytotoxic exposure, no hematologic disorders) were reviewed. The proportions of skeletal FLT activity in 10 predefined bony regions were determined and compared according to age, sex, and recent smoking status. Results: Fifty-one patients were studied: 67% male; median age 68 (range, 31-87) years; 8% never smokers; 70% no smoking in the preceding 3 months. Significant differences in marrow distribution occurred between sex and age groups. No effect was detected from smoking in the preceding 3 months. Using the mean percentages of FLT uptake per body region, we created an atlas of the distribution of functional bone marrow in 4 subgroups defined by sex and age. Conclusions: This atlas has potential utility for estimating the distribution of active marrow in adult cancer patients to guide radiation therapy planning. However, because of interindividual variation it should be used with caution when radiation therapy risks ablating large proportions of active marrow; in such cases, individual FLT-PET scans may be required.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2015

Final Report, The Influence of Organic-Aerosol Emissions and Aging on Regional and Global Aerosol Size Distributions and the CCN Number Budget

We conducted laboratory experiments and analyzed data on aging of organic aerosol and analysis of field data on volatility and CCN activity. With supplemental ASR funding we participated in the FLAME-IV campaign in Missoula MT in the Fall of 2012, deploying a two-chamber photochemical aging system to enable experimental exploration of photochemical aging of biomass burning emissions. Results from that campaign will lead to numerous publications, including demonstration of photochemical production of Brown Carbon (BrC) from secondary organic aerosol associated with biomass burning emissions as well as extensive characterization of the effect of photochemical aging on the overall concentrations of biomass burning organic aerosol. Excluding publications arising from the FLAME-IV campaign, project research resulted in 8 papers: [11, 5, 3, 10, 12, 4, 8, 7], including on in Nature Geoscience addressing the role of organic compounds in nanoparticle growth [11]

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Elamipretide effects on the skeletal muscle phosphoproteome in aged female mice

The age-related decline in skeletal muscle mass and function is known as sarcopenia. Sarcopenia progresses based on complex processes involving protein dynamics, cell signaling, oxidative stress, and repair. We have previously found that 8-week treatment with elamipretide improves skeletal muscle function, reverses redox stress, and restores protein S-glutathionylation changes in aged female mice. This study tested whether 8-week treatment with elamipretide also affects global phosphorylation in skeletal muscle consistent with functional improvements and S-glutathionylation. Using female 6–7-month-old mice and 28–29-month-old mice, we found that phosphorylation changes did not relate to S-glutathionylation modifications, but that treatment with elamipretide did partially reverse age-related changes in protein phosphorylation in mouse skeletal muscle.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

Effect of isothermal and non-isothermal aging on the low cycle fatigue behavior of an Al–Cu–Mg–Si forging alloy

Highlights: • Non-isothermal aging treatment is performed to improve low cycle fatigue performance of an Al-Cu-Mg-Si forging alloy. • Mixed precipitation characteristic manifested as shearable and non-shearable θ' phases is obtained by non-isothermal aging. • Planar slip associated with particle shearing mechanism contributes to the high fatigue crack propagation resistance. - Abstract: Low cycle fatigue (LCF) behavior of an Al–Cu–Mg–Si forging alloy was investigated at room temperature. Isothermal aging (T6) and non-isothermal aging (NIA) treatments were applied to produce different microstructures. Under the same strain amplitude, the LCF life of NIA specimen exceeded that of T6 specimen. Besides, NIA specimens exhibited cyclic stability behavior in contrast to cyclic hardening behavior of T6 specimens. The different LCF behaviors could be rationalized by different deformation mechanisms under cyclic straining. T6 specimens with non-shearable θ′-phases underwent Orowan bypassing mechanism leading to the cyclic hardening behavior. While NIA specimens with shearable and non-shearable θ′-phases suffered from both particle shearing and Orowan bypassing mechanisms resulting in the cyclic stability behavior. Non-shearable θ′-phases bypassed by dislocations introduced more stress concentration, while shearable θ′-phases cut through by dislocations caused less stress concentration. Therefore, fatigue life of NIA specimen is longer than that of T6 specimen.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Structural basis for potency differences between GDF8 and GDF11

Background: Growth/differentiation factor 8 (GDF8) and GDF11 are two highly similar members of the transforming growth factor β (TGFβ) family. While GDF8 has been recognized as a negative regulator of muscle growth and differentiation, there are conflicting studies on the function of GDF11 and whether GDF11 has beneficial effects on age-related dysfunction. To address whether GDF8 and GDF11 are functionally identical, we compared their signaling and structural properties. Results: Here, in this paper, we show that, despite their high similarity, GDF11 is a more potent activator of SMAD2/3 and signals more effectively through the type I activin-like receptor kinase receptors ALK4/5/7 than GDF8. Resolution of the GDF11:FS288 complex, apo-GDF8, and apo-GDF11 crystal structures reveals unique properties of both ligands, specifically in the type I receptor binding site. Lastly, substitution of GDF11 residues into GDF8 confers enhanced activity to GDF8. Conclusions: These studies identify distinctive structural features of GDF11 that enhance its potency, relative to GDF8; however, the biological consequences of these differences remain to be determined.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

The Effects on Non-Actinide Impurities from Aging Heat Source Plutonium in Stainless Steel Containers

Replacing the tantalum vials used for 238 PuO 2 sample collection and storage with stainless steel sample vials has several advantages. These advantages include a decreased cost, better material availability, and ease of fabrication. However, it must first be demonstrated that the alloying elements contained in stainless steel are not leached into the 238 PuO 2 such that product specifications are exceeded. In order to determine the suitability of stainless steel for this application, two seperate 238 PuO 2 fuel lots were investigated. These two fuel lots had been stored in stainless steel containers since their first sampling date of March of 2015, and were again sampled in February of 2019.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2024

Effect of Part Size, Displacement Rate, and Aging on Compressive Properties of Elastomeric Parts of Different Unit Cell Topologies Formed by Vat Photopolymerization Additive Manufacturing

Due to its ability to achieve geometric complexity at high resolution and low length scales, additive manufacturing (AM) has increasingly been used for fabricating cellular structures (e.g., foams and lattices) for a variety of applications. Specifically, elastomeric cellular structures offer tunability of compliance as well as energy absorption and dissipation characteristics. However, there are limited data available on compression properties for printed elastomeric cellular structures of different designs and testing parameters. In this work, the authors evaluate how unit cell topology, part size, the rate of compression, and aging affect the compressive response of polyurethane-based simple cubic, body-centered, and gyroid structures formed by vat photopolymerization AM. Finite element simulations incorporating hyperelastic and viscoelastic models were used to describe the data, and the simulated results compared well with the experimental data. Of the designs tested, only the parts with the body-centered unit cell exhibited differences in stress–strain responses at different part sizes. Of the compression rates tested, the highest displacement rate (1000 mm/min) often caused stiffer compressive behavior, indicating deviation from the quasi-static assumption and approaching the intermediate rate response. The cellular structures did not change in compression properties across five weeks of aging time, which is desirable for cushioning applications. This work advances knowledge on the structure–property relationships of printed elastomeric cellular materials, which will enable more predictable compressive properties that can be traced to specific unit cell designs.

36 MATERIALS SCIENCE↗
NASA NTRS1991

Effect of a prior stretch on the aging response of an Al-Cu-Li-Ag-Mg-Zr alloy

Recently, a family of Al-Cu-Li alloys containing minor amounts of Ag, Mg, and Zr and having desirable combinations of strength and toughness were developed. The Weldalite (trademark) alloys exhibit a unique characteristic in that with or without a prior stretch, they obtain significant strength-ductility combinations upon natural and artificial aging. The ultra-high strength (approximately 690 MPa yield strength) in the peak-aged tempers (T6 and T8) were primarily attributed to the extremely fine T(sub 1) (Al2CuLi) or T(sub 1)-type precipitates that occur in these alloys during artificial aging, whereas the significant natural aging response observed is attributed to strengthening from delta prime (Al3Li) and GP zones. In recent work, the aging behavior of an Al-Cu-Li-Ag-Mg alloy without a prior stretch was followed microstructurally from the T4 to the T6 condition. Commercial extrusions, rolled plates, and sheets of Al-Cu-Li alloys are typically subjected to a stretching operation before artificial aging to straighten the extrusions and, more importantly, introduce dislocations to simulate precipitation of strengthening phases such as T(sub 1) by providing relatively low-energy nucleation sites. The goals of this study are to examine the microstructure that evolves during aging of an alloy that was stretch after solution treatment and to compare the observations with those for the unstretched alloy.

Kumar, K. S.↗
NASA NTRS1992

Effects of Fe/C phase separation on the ages of white dwarfs

The energy release associated with the phase separation of Fe from C in a predominantly C white dwarf is calculated. The total gravitational-plus-internal energy differences between models of homogeneous compositions and those wth Fe-enriched cores are computed. In the unlikely case where the core is pure Fe, a substantial extension of the white dwarf cooling times is found, even with the small cosmic abundance of this element. For the more realistic core compositions that result if the Fe/C phase diagram is either of the spindle or of the azeotropic type, the energy release is still sufficient to prolong the cooling times by about 0.6 Gyr, comparable to that produced by C/O phase separation. Phase separation is found to produce an appreciable 'bump' in the luminosity function, although not one large enough to exceed the observational errors at low luminosities.

Xu, Z. W.↗
DOE OSTI2025

ZTF SN Ia DR2: An environmental study of Type Ia supernovae using host galaxy image decomposition

The second data release of Type Ia supernovae (SNe Ia) observed by the Zwicky Transient Facility has provided a homogeneous sample of 3628 SNe Ia with photometric and spectral information. This unprecedented sample size enables us to better explore our currently tentative understanding of the dependence of the host environment on SN Ia properties. In this paper, we make use of two-dimensional image decomposition to model the host galaxies of SNe Ia. We model elliptical galaxies as well as disc and spiral galaxies with or without central bulges and bars. This allows for the categorisation of SN Ia based on their morphological host environment, as well as the extraction of intrinsic galaxy properties corrected for both cosmological and atmospheric effects, through point-spread-function (PSF) convolution. We find that although this image decomposition technique leads to a significant bias towards elliptical galaxies in our final sample of processed galaxies, the overall results are still robust. By successfully modelling 728 host galaxies, we find that the photometric properties of SNe Ia found in discs and in elliptical galaxies correlate fundamentally differently with their host environment. We identified strong linear relations between light-curve stretch and our model-derived galaxy colour for both the elliptical (16.8σ) and disc (5.1σ) subpopulations of SNe Ia. Lower-stretch SNe Ia are found in redder environments, which we identify as an age and/or metallicity effect. Within the subpopulation of SNe Ia found in disc-containing galaxies, we find a significant linear trend (6.1σ) between light-curve stretch and model-derived local r-band surface brightness, which we link to the age and metallicity gradients found in disc galaxies. SN Ia colour shows little correlation with the host environment, as is seen in the literature. We do identify a possible dust effect in our model-derived surface brightness (3.3σ) for SNe Ia in disc galaxies.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Microstructure evolution and mechanical properties of Cu/Sn/Ag TLP-bonded joint during thermal aging

Highlights: • The thermal reliability of the Cu/Sn/Ag TLP-bonded joint was investigated through high-temperature storage. • A diffusion reaction occurred at the interface between Cu{sub 3}Sn and Ag{sub 3}Sn during thermal aging. • The mechanism of the Cu{sub 3}Sn/Ag{sub 3}Sn interfacial reaction was investigated from thermodynamics and kinetics. - Abstract: Low-temperature transient liquid phase (TLP) bonding is a promising joining technology for high-temperature electronic devices packaging. However, the effect of thermal aging on the joint microstructure and performance has been rarely studied so far. In this paper, the relationship between microstructural evolution and mechanical property was developed for the Cu/Sn/Ag TLP-bonded joint during 350 °C aging. Experimental results show that an interfacial reaction occurs between the intermetallic compounds (IMCs) of Cu{sub 3}Sn and Ag{sub 3}Sn, which induces that a great amount of Cu{sub 3}Sn particles or wedges embed into the Ag-Sn phase layer. The reaction process is controlled by a volume diffusion of Cu elements from the Cu substrate, and capable of promoting the transformation from Ag{sub 3}Sn into Ag(Sn) solid solution. Cu{sub 41}Sn{sub 11} phase can be formed at the expense of Cu{sub 3}Sn and Cu, of which transformation process is completely achieved after aging for 480 h, and the Cu(Sn) solid solution intimately contacts with the opposite Ag(Sn) solid solution in many areas after aging for 960 h. The joint mechanical property initially declines due to the formation of Cu{sub 41}Sn{sub 11} phase and Cu-Sn IMCs grain coarsening, and then increases because of the complete depletion of Cu{sub 3}Sn and substantial precipitation of Cu(Sn) solid solution. After aging for nearly 1000 h, the joint still maintains a high shear strength of >40 MPa, indicating an excellent thermal reliability.

36 MATERIALS SCIENCE↗
NASA NTRS1984

On-orbit frequency stability analysis of the GPS NAVSTAR-1 quartz clock and the NAVSTARs-6 and -8 rubidium clocks

An on-orbit frequency stability performance analysis of the GPS NAVSTAR-1 quartz clock and the NAVSTARs-6 and -8 rubidium clocks is presented. The clock offsets were obtained from measurements taken at the GPS monitor stations which use high performance cesium standards as a reference. Clock performance is characterized through the use of the Allan variance, which is evaluated for sample times of 15 minutes to two hours, and from one day to 10 days. The quartz and rubidium clocks' offsets were corrected for aging rate before computing the frequency stability. The effect of small errors in aging rate is presented for the NAVSTAR-8 rubidium clock's stability analysis. The analysis includes presentation of time and frequency residuals with respect to linear and quadratic models, which aid in obtaining aging rate values and identifying systematic and random effects. The frequency stability values were further processed with a time domain noise process analysis, which is used to classify random noise process and modulation type.

Mccaskill, T. B.↗
NASA NTRS2001

The molecular responses of skeletal muscle satellite cells to continuous expression of IGF-1: implications for the rescue of induced muscular atrophy in aged rats

Approximately 50% of humans older than 85 years have physical frailty due to weak skeletal muscles. This indicates a need for determining mechanisms to combat this problem. A critical cellular factor for postnatal muscle growth is a population of myogenic precursor cells called satellite cells. Given the complex process of sarcopenia, it has been postulated that, at some point in this process, a limited satellite cell proliferation potential could become rate-limiting to the regrowth of old muscles. It is conceivable that if satellite cell proliferative capacity can be maintained or enhanced with advanced age, sarcopenia could potentially be delayed or prevented. Therefore, the purposes of this paper are to describe whether IGF-I can prevent muscular atrophy induced by repeated cycles of hindlimb immobilization, increase the in vitro proliferation in satellite cells from these muscles and, if so, the molecular mechanisms by which IGF-I mediates this increased proliferation. Our results provide evidence that IGF-I can enhance aged muscle regrowth possibly through increased satellite cell proliferation. The results also suggest that IGF-I enhances satellite cell proliferation by decreasing the cell cycle inhibitor, p27Kip1, through the PI3'-K/Akt pathway. These data provide molecular evidence for IGF-I's rescue effect upon aging-associated skeletal muscle atrophy.

NASA Discipline Musculoskeletal↗
DOE OSTI2015

Physical aging and charge transport in poly(3‐hexylthiophene)

The bulk charge transport in a series of regioregular poly(3‐hexylthiophene) materials with different molecular weights (MW) has been studied by the time‐of‐flight technique. Three distinct temperature regions with transitions at ∼60 and ∼140 °C in lower MW material (9.6 kDa), and four regions with an additional transition at ∼180 °C in higher MW material (32.3 kDa) are identified in the temperature dependence of charge carrier mobility and the origin of these transitions is discussed. A pronounced effect of physical aging which reveals as a reversible increase of charge mobility is found. Densification of amorphous phase in‐between the nanocrystals, which reduces the potential energy barriers and provides larger charge transfer integrals, is proposed as an origin of the effect.

Duzhko, Volodimyr V.↗