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All sourcesNASA NTRSDOE OSTI
NASA NTRS2002

A Comparison of the Age-Spectra from Data Assimilation Models

We use kinematic and diabatic back trajectory calculations, driven by winds from a general circulation model (GCM) and two different data assimilation systems (DAS), to compute the age spectrum at three latitudes in the lower stratosphere. The age-spectra are compared to chemical transport model (CTM) calculations, and the mean ages from all of these studies are compared to observations. The age spectra computed using the GCM winds show a reasonably well-isolated tropics in good agreement with observations; however, the age spectra determined from the DAS differ from the GCM spectra. For the diabatic trajectory calculations, the age spectrum is too broad as a result of too much exchange between the tropics and mid-latitudes. The age spectrum determined using the kinematic trajectory calculation is less broad and lacks an age offset; both of these features are due to excessive vertical dispersion of parcels. The tropical and mid-latitude mean age difference between the diabatically and kinematically determined age-spectra is about one year, the former being older. The CTM calculation of the age spectrum using the DAS winds shows the same dispersive characteristics of the kinematic trajectory calculation. These results suggest that the current DAS products will not give realistic trace gas distributions for long integrations; they also help explain why the mean ages determined in a number of previous DAS driven CTM's are too young compared with observations. Finally, we note trajectory-generated age spectra show significant age anomalies correlated with the seasonal cycles, and these anomalies can be linked to year-to-year variations in the tropical heating rate. These anomalies are suppressed in the CTM spectra suggesting that the CTM transport is too diffusive.

Schoeberl, Mark R.↗
NASA NTRS2002

A Comparison of the Lower Stratospheric Age-Spectra Derived from a General Circulation Model and Two Data Assimilation Systems

We use kinematic and diabatic back trajectory calculations, driven by winds from a general circulation model (GCM) and two different data assimilation systems (DAS), to compute the age spectrum at three latitudes in the lower stratosphere. The age-spectra are compared to chemical transport model (CTM) calculations, and the mean ages from all of these studies are compared to observations. The age spectra computed using the GCM winds show a reasonably isolated tropics in good agreement with observations; however, the age spectra determined from the DAS differ from the GCM spectra. For the DAS diabatic trajectory calculations there is too much exchange between the tropics and mid-latitudes. The age spectrum is thus too broad and the tropical mean age is too old as a result of mixing older mid latitude air with tropical air. Likewise the mid latitude mean age is too young due to the in mixing of tropical air. The DAS kinematic trajectory calculations show excessive vertical dispersion of parcels in addition to excessive exchange between the tropics and mid latitudes. Because air is moved rapidly to the troposphere from the vertical dispersion, the age spectrum is shifted toward the young side. The excessive vertical and meridional dispersion compensate in the kinematic case giving a reasonable tropical mean age. The CTM calculation of the age spectrum using the DAS winds shows the same vertical and meridional dispersive characteristics of the kinematic trajectory calculation. These results suggest that the current DAS products will not give realistic trace gas distributions for long integrations; they also help explain why the extra tropical mean ages determined in a number of previous DAS driven CTM s are too young compared with observations. Finally, we note trajectory-generated age spectra . show significant age anomalies correlated with the seasonal cycles. These anomalies can be linked to year-to-year variations in the tropical heating rate. The anomalies are suppressed in the CTM spectra suggesting that the CTM transport scheme is too diffusive.

Schoeberl, Mark R.↗
DOE OSTI2020

Degradation of impact toughness in cast stainless steels during long-term thermal aging

Cast austenitic stainless steels (CASSs) have been extensively used for the large components of nuclear reactor primary coolant systems. Since the cast steels inevitably contain degradable metastable phases and replacement of the large coolant system components is impractical, the thermal embrittlement of CASS components has been a serious concern in the extended-term operation of nuclear power plants. This study aimed to systematically measure and analyze the effect of long-term thermal aging on the Charpy impact toughness to provide a comprehensive understanding of thermal degradation behavior and a practical aging model to predict the degree of thermal degradation in the cast stainless steels. Additionally, the materials tested in the research include eight CASS alloys (two CF3s, one CF3M, three CF8s, and two CF8Ms) and two reference wrought materials (304L and 316L), in which the nominal δ-ferrite content ranges from ~2% to 33%. These stainless steels have been thermally aged at two light water reactor (LWR) temperatures (290 and 330 °C) and at two accelerated-aging temperatures (360 and 400 °C) for up to 30,000 h; these include both under-aged and over-aged conditions relative to the extended service lifetime (80 years). Charpy impact testing was performed for aged and non-aged specimens, and the impact (absorbed) energy parameters were correlated with a new aging parameter (A). Both the reduction of impact fracture toughness and the shift of ductile-brittle transition temperature were strongly dependent on the δ-ferrite content and degree of thermal aging. A linear relationship was found between the increasing rate of the index transition temperature T 41J and aging parameter A; base on which an empirical model was proposed for prediction of the transition temperature as a simple function of the aging parameter (A) and δ-ferrite content (F). Finally, the critical aging parameter for embrittlement (AC) was evaluated and compared with the existing δ-ferrite content criteria.

36 MATERIALS SCIENCE↗
DOE OSTI2021

SIRT1 reduces epigenetic and non-epigenetic changes to maintain the quality of postovulatory aged oocytes in mice

Highlights: • The intensity of H3K9ac and H3K4me2/3 increased in postovulatory aged oocytes. • SIRT1 overexpression inhibited the increase of H3K9ac and H3K4me2/3. • SIRT1 overexpression ameliorated aging-induced epigenetic and non-epigenetic changes in oocytes. Postovulatory oocyte aging has a major influence on the development potential of embryos. Many antioxidants can delay oocyte aging by regulating the expression of SIRT1. However, there is a lack of knowledge on SIRT1 function in postovulatory oocyte aging. In vitro transcribed RNA of Sirt1 was injected into fresh oocytes to investigate the function of SIRT1 during postovulatory oocyte aging. In the present study, SIRT1 was found to be down-regulated in aged oocytes compared with fresh oocytes. Meanwhile the intensity of acetylation of H3K9 (H3K9ac) and H3K4 methylation increased in postovulatory aged oocytes. After the oocytes were injected with SIRT1 and aged for 12 h, the intensity of H3K9ac and H3K4 methylation markedly decreased compared with controls. Furthermore, SIRT1 overexpression also reduced the aging-induced oocyte morphological changes and reactive oxygen species accumulation, maintained the spindle normal morphology and attenuated the aging-associated abnormalities of mitochondrial function. The role of SIRT1 in protecting oocyte aging was diminished when oocytes with overexpressed SIRT1 were cultured with SIRT1 inhibitor EX-527. Briefly, these present results show that SIRT1 not only reduced the non-epigenetic changes such as abnormal oocyte morphology, ROS accumulation, spindle defects and mitochondrial dysfunctions but also regulated the epigenetic changes in order to maintain the quality of postovulatory aged oocytes.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Age-related accumulation of advanced glycation end-products-albumin, S100β, and the expressions of advanced glycation end product receptor differ in visceral and subcutaneous fat

Visceral fat induces more inflammation by activating macrophages than subcutaneous fat, and inflammation is an underlying feature of the pathogeneses of various diseases, including cardiovascular disease and diabetes. Advanced glycation end products (AGEs), S100β, and their receptors, the receptor for advanced glycation end products (RAGE), lead to macrophage activation. However, little information is available regarding the differential accumulations of AGE-albumin (serum albumin modified by AGEs), S100β, or expressions of RAGE in different adipocyte types in fat tissues. In this study, the authors investigated whether age-related AGE-albumin accumulations S100β level, and RAGE expressions differ in subcutaneous and visceral fat tissues. Subcutaneous and visceral fat were harvested from 3- and 28-week-old rats. Macrophage activation was confirmed by Iba1 staining, and AGE-albumin accumulations and RAGE expressions were assessed by confocal microscopy. S100β were analyzed by immunoblotting. It was found that activated macrophage infiltration, AGE-albumin accumulation, and S100β in visceral fat was significantly greater in 28-week-old rats than in 3-week-old rats, but similar in subcutaneous fat. The expression of RAGE in visceral fat was much greater in 28-week-old rats, but its expression in subcutaneous fat was similar in 3- and 28-week-old rats. Furthermore, inflammatory signal pathways (NFκB, TNF-α) and proliferation pathways (FAK) in visceral fat were more activated in 28-week-old rats. These results imply that age-related AGE-albumin accumulation, S100β, and RAGE expression are more prominent in visceral than in subcutaneous fat, suggesting that visceral fat is involved in the pathogenesis of inflammation-induced diseases in the elderly. - Highlights: • The age-related AGE-albumin accumulation and S100β were more prominent in visceral than subcutaneous fat. • The age-related RAGE expression were more prominent in visceral than subcutaneous fat. • The inflammatory signal pathway were more activated in aged animal visceral than subcutaneous fat. • The results suggested visceral fat is involved in inflammation-induced diseases in the elderly.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

Microstructure evolution of 7050 Al alloy during age-forming

The microstructure evolution of the 7050 Al alloy treated by age-forming was studied using a designed device which can simulate the age-forming process. The grain shape, grain boundary misorientation and grain orientation evolution of 7050 Al alloy during age-forming have been quantitatively characterized by electron backscattering diffraction technique. The results show that age-forming produced abundant low-angle boundaries and elongated grains, which attributed to stress induced dislocation movement and grain boundary migration during the age-forming process. On the other side, the stress along rolling direction caused some unstable orientation grains to rotate towards the Brass and S orientations during the age-forming process. Hence, the intensity of the rolling texture orientation in age-formed samples is enhanced. But this effect decays gradually with increasing aging time, since stress decreases and precipitation hardening occurs during the age-forming process. - Highlights: • Quantitative analysis of grain evolution of 7050 Al alloys during age-forming • Stress induces some grain rotation of 7050 Al alloys during age-forming. • Creep leads to elongate grain of 7050 Al alloys during age-forming. • Obtains a trend on texture evolution during age-forming applied stress.

36 MATERIALS SCIENCE↗
DOE OSTI2013

THE AGES OF 55 GLOBULAR CLUSTERS AS DETERMINED USING AN IMPROVED ΔV{sup HB}{sub TO} METHOD ALONG WITH COLOR-MAGNITUDE DIAGRAM CONSTRAINTS, AND THEIR IMPLICATIONS FOR BROADER ISSUES

Ages have been derived for 55 globular clusters (GCs) for which Hubble Space Telescope Advanced Camera for Surveys photometry is publicly available. For most of them, the assumed distances are based on fits of theoretical zero-age horizontal-branch (ZAHB) loci to the lower bound of the observed distributions of HB stars, assuming reddenings from empirical dust maps and metallicities from the latest spectroscopic analyses. The age of the isochrone that provides the best fit to the stars in the vicinity of the turnoff (TO) is taken to be the best estimate of the cluster age. The morphology of isochrones between the TO and the beginning part of the subgiant branch (SGB) is shown to be nearly independent of age and chemical abundances. For well-defined color-magnitude diagrams (CMDs), the error bar arising just from the 'fitting' of ZAHBs and isochrones is ≈ ± 0.25 Gyr, while that associated with distance and chemical abundance uncertainties is ∼ ± 1.5-2 Gyr. The oldest GCs in our sample are predicted to have ages of ≈13.0 Gyr (subject to the aforementioned uncertainties). However, the main focus of this investigation is on relative GC ages. In conflict with recent findings based on the relative main-sequence fitting method, which have been studied in some detail and reconciled with our results, ages are found to vary from mean values of ≈12.5 Gyr at [Fe/H] ∼< – 1.7 to ≈11 Gyr at [Fe/H] ∼> –1. At intermediate metallicities, the age-metallicity relation (AMR) appears to be bifurcated: one branch apparently contains clusters with disk-like kinematics, whereas the other branch, which is displaced to lower [Fe/H] values by ≈0.6 dex at a fixed age, is populated by clusters with halo-type orbits. The dispersion in age about each component of the AMR is ∼ ± 0.5 Gyr. There is no apparent dependence of age on Galactocentric distance (R{sub G}) nor is there a clear correlation of HB type with age. As previously discovered in the case of M3 and M13, subtle variations have been found in the slope of the SGB in the CMDs of other metal-poor ([Fe/H] ∼< – 1.5) GCs. They have been tentatively attributed to cluster-to-cluster differences in the abundance of helium. Curiously, GCs that have relatively steep 'M13-like' SGBs tend to be massive systems, located at small R{sub G}, that show the strongest evidence of in situ formation of multiple stellar populations. The clusters in the other group are typically low-mass systems (with 2-3 exceptions, including M3) that, at the present time, should not be able to retain the matter lost by mass-losing stars due either to the development of GC winds or to ram-pressure stripping by the halo interstellar medium. The apparent separation of the two groups in terms of their present-day gas retention properties is difficult to understand if all GCs were initially ∼20 times their current masses. The lowest-mass systems, in particular, may have never been massive enough to retain enough gas to produce a significant population of second-generation stars. In this case, the observed light element abundance variations, which are characteristic of all GCs, were presumably present in the gas out of which the observed cluster stars formed.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Age gradients in the stellar populations of massive star forming regions based on a new stellar chronometer

A major impediment to understanding star formation in massive star-forming regions (MSFRs) is the absence of a reliable stellar chronometer to unravel their complex star formation histories. We present a new estimation of stellar ages using a new method that employs near-infrared (NIR) and X-ray photometry, Age {sub JX} . Stellar masses are derived from X-ray luminosities using the L{sub X} -M relation from the Taurus cloud. J-band luminosities are compared to mass-dependent pre-main-sequence (PMS) evolutionary models to estimate ages. Age {sub JX} is sensitive to a wide range of evolutionary stages, from disk-bearing stars embedded in a cloud to widely dispersed older PMS stars. The Massive Young Star-Forming Complex Study in Infrared and X-ray (MYStIX) project characterizes 20 OB-dominated MSFRs using X-ray, mid-infrared, and NIR catalogs. The Age {sub JX} method has been applied to 5525 out of 31,784 MYStIX Probable Complex Members. We provide a homogeneous set of median ages for over 100 subclusters in 15 MSFRs; median subcluster ages range between 0.5 Myr and 5 Myr. The important science result is the discovery of age gradients across MYStIX regions. The wide MSFR age distribution appears as spatially segregated structures with different ages. The Age {sub JX} ages are youngest in obscured locations in molecular clouds, intermediate in revealed stellar clusters, and oldest in distributed populations. The NIR color index J – H, a surrogate measure of extinction, can serve as an approximate age predictor for young embedded clusters.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

A variational encoder–decoder approach to precise spectroscopic age estimation for large Galactic surveys

Constraints on the formation and evolution of the Milky Way Galaxy require multidimensional measurements of kinematics, abundances, and ages for a large population of stars. Ages for luminous giants, which can be seen to large distances, are an essential component of studies of the Milky Way, but they are traditionally very difficult to estimate precisely for a large data set and often require careful analysis on a star-by-star basis in asteroseismology. Because spectra are easier to obtain for large samples, being able to determine precise ages from spectra allows for large age samples to be constructed, but spectroscopic ages are often imprecise and contaminated by abundance correlations. Here we present an application of a variational encoder–decoder on cross-domain astronomical data to solve these issues. The model is trained on pairs of observations from APOGEE and Kepler of the same star in order to reduce the dimensionality of the APOGEE spectra in a latent space while removing abundance information. The low dimensional latent representation of these spectra can then be trained to predict age with just ∼1000 precise seismic ages. We demonstrate that this model produces more precise spectroscopic ages (∼ 22 per cent overall, ∼ 11 per cent for red-clump stars) than previous data-driven spectroscopic ages while being less contaminated by abundance information (in particular, our ages do not depend on [α/M]). We create a public age catalogue for the APOGEE DR17 data set and use it to map the age distribution and the age-[Fe/H]-[α/M] distribution across the radial range of the Galactic disc.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2026

Cellular signaling within aged skeletal muscle reveals a dysregulated stress-induced remodeling response following volumetric muscle loss in female mice

Severe muscle trauma disrupts endogenous repair mechanisms, producing chronic functional deficits that are incompletely characterized in aged populations. This study investigated inflammatory, molecular, and physiological responses to volumetric muscle loss in young adult and aged female mice. Serum cytokine profiling revealed elevated baseline inflammation in aged animals and a blunted response to injury, with cytokines such as IL-6 increasing 4.4-fold in young versus 1.8-fold in aged mice at day 3 compared to baseline. By day 28 post-injury, histological analyses showed comparable reductions in muscle size and increases in fibrosis across ages. Despite these similar tissue-level outcomes, age-dependent differences emerged in downstream functional and molecular responses. Muscle functional testing demonstrated persistent force deficits independent of age but altered muscle relaxation kinetics in aged mouse muscles (p < 0.001), suggesting dysregulated excitation-contraction coupling. Additionally, mice displayed age-associated differences in post-injury limb loading. Global proteomic analyses further confirmed age-associated enrichment of complement and antigen-processing pathways alongside metabolic dysfunction (p < 0.05). Phosphoproteomic profiling revealed reduced basal kinase activity in the muscles of aged mice yet exaggerated injury-induced phosphorylation of Mapk1-associated phosphosites, indicating a dysregulated stress response. Collectively, these findings suggest that aged murine muscles function within a heightened inflammatory and perturbed kinase-signaling environment that may hinder the coordination of regenerative programs, underscoring the need for regenerative strategies that address age-specific molecular contexts to improve functional recovery across the lifespan.

Habing, Krista M.↗
DOE OSTI2016

Real-time measurements of secondary organic aerosol formation and aging from ambient air in an oxidation flow reactor in the Los Angeles area

Field studies in polluted areas over the last decade have observed large formation of secondary organic aerosol (SOA) that is often poorly captured by models. The study of SOA formation using ambient data is often confounded by the effects of advection, vertical mixing, emissions, and variable degrees of photochemical aging. An oxidation flow reactor (OFR) was deployed to study SOA formation in real-time during the California Research at the Nexus of Air Quality and Climate Change (CalNex) campaign in Pasadena, CA, in 2010. A high-resolution aerosol mass spectrometer (AMS) and a scanning mobility particle sizer (SMPS) alternated sampling ambient and reactor-aged air. The reactor produced OH concentrations up to 4 orders of magnitude higher than in ambient air. OH radical concentration was continuously stepped, achieving equivalent atmospheric aging of 0.8 days–6.4 weeks in 3 min of processing every 2 h. Enhancement of organic aerosol (OA) from aging showed a maximum net SOA production between 0.8–6 days of aging with net OA mass loss beyond 2 weeks. Reactor SOA mass peaked at night, in the absence of ambient photochemistry and correlated with trimethylbenzene concentrations. Reactor SOA formation was inversely correlated with ambient SOA and O x , which along with the short-lived volatile organic compound correlation, indicates the importance of very reactive ( τ OH ~ 0.3 day) SOA precursors (most likely semivolatile and intermediate volatility species, S/IVOCs) in the Greater Los Angeles Area. Evolution of the elemental composition in the reactor was similar to trends observed in the atmosphere (O : C vs. H : C slope ~ –0.65). Oxidation state of carbon (OSc) in reactor SOA increased steeply with age and remained elevated (OS C ~ 2) at the highest photochemical ages probed. The ratio of OA in the reactor output to excess CO (ΔCO, ambient CO above regional background) vs. photochemical age is similar to previous studies at low to moderate ages and also extends to higher ages where OA loss dominates. The mass added at low-to-intermediate ages is due primarily to condensation of oxidized species, not heterogeneous oxidation. The OA decrease at high photochemical ages is dominated by heterogeneous oxidation followed by fragmentation/evaporation. A comparison of urban SOA formation in this study with a similar study of vehicle SOA in a tunnel suggests the importance of vehicle emissions for urban SOA. Pre-2007 SOA models underpredict SOA formation by an order of magnitude, while a more recent model performs better but overpredicts at higher ages. Furthermore, these results demonstrate the value of the reactor as a tool for in situ evaluation of the SOA formation potential and OA evolution from ambient air.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS2003

Aging Optimization of Aluminum-Lithium Alloy C458 for Application to Cryotank Structures

Compared with aluminum alloys such as 2219, which is widely used in space vehicle for cryogenic tanks and unpressurized structures, aluminum-lithium alloys possess attractive combinations of lower density and higher modulus along with comparable mechanical properties. These characteristics have resulted in the successful use of the aluminum-lithium alloy 2195 (Al-1.0 Li-4.0 Cu-0.4 Mg-0.4 Ag-0.12 Zr) for the Space Shuttle External Tank, and the consideration of newer U.S. aluminum-lithium alloys such as L277 and C458 for future space vehicles. These newer alloys generally have lithium content less than 2 wt. % and their composition and processing have been carefully tailored to increase the toughness and reduce the mechanical property anisotropy of the earlier generation alloys such 2090 and 8090. Alloy processing, particularly the aging treatment, has a significant influence on the strength-toughness combinations and their dependence on service environments for aluminum-lithium alloys. Work at NASA Marshall Space Flight Center on alloy 2195 has shown that the cryogenic toughness can be improved by employing a two-step aging process. This is accomplished by aging at a lower temperature in the first step to suppress nucleation of the strengthening precipitate at sub-grain boundaries while promoting nucleation in the interior of the grains. Second step aging at the normal aging temperature results in precipitate growth to the optimum size. A design of experiments aging study was conducted for plate. To achieve the T8 temper, Alloy C458 (Al-1.8 Li-2.7 Cu-0.3 Mg-0.08 Zr-0.3 Mn-0.6 Zn) is typically aged at 300F for 24hours. In this study, a two-step aging treatment was developed through a comprehensive 2(exp 4) full factorial design of experiments study and the typical one-step aging used as a reference. Based on the higher lithium content of C458 compared with 2195, the first step aging temperature was varied between 175F and 250F. The second step aging temperatures was varied between 275F and 325F, which is in the range of the single-step aging temperature. The results of the design of experiments used for the T8 temper as well as a smaller set of experiments for the T6 temper will be presented. The process of selecting the optimum aging treatment, based on the measured mechanical properties at room and cryogenic temperature as well as the observed deformation mechanisms, will be presented in detail. The implications for the use of alloy C458 in cryotanks will be discussed.

Sova, B. J.↗
NASA NTRS2003

Aging Optimization of Aluminum-Lithium Alloy C458 for Application to Cryotank Structures

Compared with aluminum alloys such as 2219, which is widely used in space vehicle for cryogenic tanks and unpressurized structures, aluminum-lithium alloys possess attractive combinations of lower density and higher modulus along with comparable mechanical properties. These characteristics have resulted in the successful use of the aluminum-lithium alloy 2195 (Al-1.0 Li-4.0 Cu-0.4 Mg-0.4 Ag-0.12 Zr) for the Space Shuttle External Tank, and the consideration of newer U.S. aluminum-lithium alloys such as L277 and C458 for future space vehicles. These newer alloys generally have lithium content less than 2 wt. % and their composition and processing have been carefully tailored to increase the toughness and reduce the mechanical property anisotropy of the earlier generation alloys such 2090 and 8090. Alloy processing, particularly the aging treatment, has a significant influence on the strength-toughness combinations and their dependence on service environments for aluminum-lithium alloys. Work at NASA Marshall Space Flight Center on alloy 2195 has shown that the cryogenic toughness can be improved by employing a two-step aging process. This is accomplished by aging at a lower temperature in the first step to suppress nucleation of the strengthening precipitate at sub-grain boundaries while promoting nucleation in the interior of the grains. Second step aging at the normal aging temperature results in precipitate growth to the optimum size. A design of experiments aging study was conducted for plate. To achieve the T8 temper, Alloy C458 (Al-1.8 Li-2.7 Cu-0.3 Mg- 0.08 Zr-0.3 Mn-0.6 Zn) is typically aged at 300 F for 24 hours. In this study, a two-step aging treatment was developed through a comprehensive 24 full factorial design of experiments study and the typical one-step aging used as a reference. Based on the higher lithium content of C458 compared with 2195, the first step aging temperature was varied between 175 F and 250 F. The second step aging temperatures was varied between 275 F and 325 F, which is in the range of the single-step aging temperature. The results of the design of experiments used for the T8 temper as well as a smaller set of experiments for the T6 temper will be presented. The process of selecting the optimum aging treatment, based on the measured mechanical properties at room and cryogenic temperature as well as the observed deformation mechanisms, will be presented in detail. The implications for the use of alloy C458 in cryotanks will be discussed.

Sova, B. J.↗
DOE OSTI2017

Aging Processes of Silver Mordenite and Silver Functionalized Aerogel in Dry Air, Humid Air and NO/N{sub 2}

One major problem in the treatment of nuclear-fuel reprocessing off-gas streams is the loss of capacity of the adsorbents exposed to off-gas streams containing air, I{sub 2} vapor, H{sub 2}O vapor, NO and NO{sub 2} over extended periods of time. These aging processes decrease the adsorption capacity of the reduced silver exchanged mordenite (Ag{sup 0}Z) and silver functionalized silica aerogel (Ag{sup 0}-aerogel) columns during the long processing time of iodine adsorption. Significant work has been performed over the past few years at ORNL on Ag{sup 0}Z and Ag{sup 0}-aerogel aging. The Ag{sup 0}Z and Ag{sup 0}-aerogel were aged in 4 different gas streams at 150 deg. C for periods of time up to 6 months. The aging samples were then loaded with I{sub 2} to determine the capacity loss after the aging. The results are summaries in Tab. 1. It was found that both Ag{sup 0}Z and Ag{sup 0}-aerogel had different amounts of capacity loss in different gases. For example, 40% and 22% capacity loss were observed for Ag{sup 0}Z and Ag{sup 0}-aerogel when aged in dry air for 6 months, while 78% and 43% capacity loss were observed when aged in 1% NO{sub 1} for 2 months. In addition, it was found that Ag{sup 0}Z and Ag{sup 0}-aerogel had a different capacity loss when aged at the same conditions. For example, after aged in 2% NO{sub 2} for 2 months, Ag{sup 0}Z lost 30% iodine capacity, but there was no capacity loss for Ag{sup 0}- aerogel. The differences in capacity loss should be due to different aging processes occurred when Ag{sup 0}Z and Ag{sup 0}- aerogel were exposed to different gases. The mechanisms of the aging processes have not been determined and need to be studied with proper chemical and physical characterization methods. Towards this objective, experimental work is proposed and on-going to obtain data to determine the mechanisms of the aging processes of Ag{sup 0}Z and Ag{sup 0}-aerogel in different aging gas streams. In addition, models will be developed to describe the deactivation process of the adsorbents when exposed to off gases. The deactivation model will be included in the transport models for predicting the adsorption processes over these long-time periods.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

Weather aging effects on modified asphalt with rubber-polyethylene composites

Weather aging may cause more severe degradation on asphalt than thermal-oxidative aging due to the synergistic effect among oxygen, heat, ultraviolet (UV) radiation, and moisture. This study aimed to investigate weather aging effects and anti-aging mechanisms on asphalt modified with rubber-polyethylene (PE) composites. The modified binder blends and asphalt mixtures were subjected to outdoor weather aging. Dynamic shear rheometer (DSR), Fourier transform infrared spectroscopy (FTIR), Gel permeation chromatography (GPC), and optical microscopy tests were adopted to characterize the rheological properties, aging resistance, polymer degradation, and anti-aging mechanisms of modified binder blends, respectively. Mixture performance tests including Asphalt Pavement Analyzer (APA) and Ideal-CT tests were used to evaluate rutting and cracking resistance of asphalt mixtures. Results showed that weather aging can cause more severe aging to asphalt binders than pressure aging vessel (PAV) due to the severe degradation of PE particles. Rubber-PE composites alloyed with an extruder proved to stabilize PE particles in asphalt and significantly improve the aging resistance of modified binder blends. Furthermore, the enhanced aging resistance is attributed to the dispersion of PE particles and carbon black released by soluble rubbers.

Aging resistance↗
DOE OSTI2021

Application of Cable Condition Monitoring Technologies to Assess Age-Related Degradation of Industrial Cables Installed in Harsh Environments

The aging of electrical cables has been the subject of substantial research and development (R&D) projects performed by national and international laboratories, universities, and private organizations for many years. This R&D was conducted to develop guidance, equipment, and techniques to support aging management of in-service cables in industrial facilities such as nuclear power plants, research reactors, waste facilities, and fuel fabrication plants. Through these research efforts, condition monitoring technologies have been developed that can determine the severity of age-related degradation that occurs in industrial cables and insulation polymers during service. This paper summarizes the results of aging assessments that were performed for cables installed in two U.S. nuclear power plants, one a pressurized water reactor and one a boiling water reactor. These cables had been in service for over 40 years and during plant operation were exposed to harsh environmental conditions including elevated temperatures and radiation. For these assessments, a comprehensive series of measurements was performed to assess the aged condition of the cables. These cables came from different manufacturers, were manufactured in different years, and were constructed with a variety of jacket and insulation polymers including chloro-sulfonated polyethylene (CSPE), cross-linked polyethylene (XLPE)/cross-linked polyolefin (XLPO), neoprene, and ethylene propylene rubber (EPR). The goal of these assessments was to determine the current aged condition of the cable polymers and provide an estimate of how long the cable insulation materials could remain exposed to their in-service environmental conditions before reaching their end-of-life condition. Both nuclear power plants have received license renewals to extend their operation from 40 to 60 years, and the utilities need objective evidence to show that critical components such as cables will be able to function safely and reliably during the extended operating period. Furthermore, the results of these assessments showed that the cables exhibited different aged conditions depending on the type of polymers they were constructed with and the environment they were exposed to during service. Some of the cables and insulation polymers showed signs of significant age-related degradation and were estimated to have approximately 5 years of remaining service life. Other cables exhibited no signs of significant age-related degradation and were estimated to have 50 years or more of remaining service life. Using the results of these cable aging assessments, plant personnel were able to (1) determine the overall aged condition of cables and insulation polymers using objective test results, (2) identify aged or degraded cables before they caused operability issues, and (3) avoid unnecessary and costly replacement of cables that can continue to operate safely and reliably.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Chronic kidney disease and aging differentially diminish bone material and microarchitecture in C57Bl/6 mice

Chronic kidney disease (CKD) is a common disease of aging and increases fracture risk over advanced age alone. Aging and CKD differently impair bone turnover and mineralization. We thus hypothesize that the loss of bone quality would be greatest with the combination of advanced age and CKD. We evaluated bone from young adult (6 mo.), middle-age (18 mo.), and old (24 mo.) male C57Bl/6 mice three months following either 5/6th nephrectomy, to induce CKD, or Sham procedures. CKD exacerbated losses of cortical and trabecular microarchitecture associated with aging. Aging and CKD each resulted in thinner, more porous cortices and fewer and thinner trabeculae. Bone material quality was also reduced with CKD, and these changes to bone material were distinct from those due to age. Aging reduced whole-bone flexural strength and modulus, micrometer-scale nanoindentation modulus, and nanometer-scale tissue and collagen strain (small-angle x-ray scattering [SAXS]. By contrast, CKD reduced work to fracture and variation in bone tissue modulus and composition (Raman spectroscopy), and increased percent collagen strain. The increased collagen strain burden was associated with loss of toughness in CKD. In addition, osteocyte lacunae became smaller, sparser, and more disordered with age for Sham mice, yet these age-related changes were not clearly observed in CKD. However, for CKD, larger lacunae positively correlated with increased serum phosphate levels, suggesting that osteocytes play a role in systemic mineral homeostasis. This work demonstrates that CKD reduces bone quality, including microarchitecture and bone material properties, and that loss of bone quality with age is compounded by CKD. Finally, these findings may help reconcile why bone mass does not consistently predict fracture in the CKD population, as well as why older individuals with CKD are at high risk of fragility.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2013

Aging phenotypes in cultured normal human mammary epithelial cells are correlated with decreased telomerase activity independent of telomere length

Shortening of telomeres, which are essential for maintenance of genomic integrity, is a mechanism commonly associated with the aging process. Here we ascertained whether changes in telomere lengths or telomerase activity correlated with age in normal human mammary epithelial cells (HMEC), or with phenotypes of aging in breast. Accordingly, flow cytometry fluorescence in situ hybridization (flowFISH) was used to determine relative telomere lengths (RTL), and telomerase activity was measured by the telomeric repeat amplification protocol (TRAP), in a collection of 41 primary HMEC strains established from women aged 16 to 91 years. RTL measurements of HMEC strains that were heterogeneous with respect to lineage composition revealed no significant associations between telomere length with age, maximum observed population doublings, or with lineage composition of the strains. However, within strains, luminal epithelial and cKit-expressing epithelial progenitor cells that were flow cytometry-enriched from individual HMEC strains exhibited significantly shorter telomeres relative to isogenic myoepithelial cells (P < 0.01). In unsorted strains, detectable telomerase activity did not correlate with RTL. Telomerase activity declined with age; the average age of strains that exhibited TRAP activity was 29.7 ± 3.9y, whereas the average age of strains with no detectable TRAP activity was 49.0 ± 4.9y (P < 0.01). Non-detectable TRAP activity also was correlated with phenotypes of aging previously described in HMEC strains; increased proportions of CD227-expressing luminal epithelial cells (P < 0.05) and cKit-expressing progenitor cells (P < 0.05). Telomere shortening did not correlate with the chronological ages of HMEC strains, whereas decreased telomerase activity correlated with age and with lineage distribution phenotypes characteristic of aging.

59 BASIC BIOLOGICAL SCIENCES↗