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At least 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Hygrothermal aging and recycling effects on mechanical and thermal properties of recyclable thermoplastic glass fiber composites

Abstract Glass fiber‐reinforced polymer composites are widely used in marine applications, including renewable energy devices and submarines, due to their strength‐to‐weight ratios and corrosion resistance. As sustainability becomes more important, recyclable thermoplastic composites are gaining attention in marine energy applications. These materials face harsh conditions such as high chloride water, UV radiation, pressurization, and thermal cycling, which can affect their durability and recyclability. This study examines the impact of hygrothermal aging on the recyclability of an Elium glass fiber (GF) composite. Samples were mechanically ground for recycling, and mechanical and thermal properties were compared between aged and unaged samples. After seawater aging, the tensile strength and modulus of the unaged composite dropped by 25% and 13% respectively, due to water ingress along the fiber‐matrix interface. The recycled composite showed reduced flexural strength as the long fiber composite was converted into short fibers during the process. Differential scanning calorimetry (DSC) revealed no change in glass transition temperature after aging. Weight loss (25%) was attributed to the thermal stability of the glass fibers. Dynamic mechanical analysis (DMA) showed that the storage modulus increased with aging, and fracture analysis confirmed a mixed mode of failure for aged composites. Highlights Hygrothermal aging lowers mechanical performance of Elium® GF composites. Failure mechanism tends to be matrix cracking and interface bonding. Glass transition temperature is not reduced by hygrothermal aging. Fractured composite was successfully recycled via thermoforming. Flexural strength of the recycled composite is lower.

17 WIND ENERGY↗
DOE OSTI2020

The Role of Pentaerythritol Tetranitrate (PETN) Aging in Determining Detonator Firing Characteristics

Pentaerythritol tetranitrate (PETN) is one of the most commonly used explosives for both military and mining applications. PETN is used in EBW (exploding bridge wire) and EFI (exploding foil initiator) detonator devices. Due the widespread usage of PETN, studies focusing on how the explosive changes with age, primarily its function in detonators has received particular interest. Aging studies have identified several factors that affect PETN detonator function over time, most notably the specific surface area of the explosive powder. Though small-scale studies have been performed on specific detonator systems with isolated batches of material, what is missing is a large statistically-significant study focusing on PETN aging characteristics - such as powder coarsening - and their influence on detonator performance. Herein we report the first large statistically viable PETN aging study focusing on four batches of PETN powder from the same stock of PETN using two stabilizers, polysaccharide and TriPEON. PETN was aged both as a free-flowing powder as well as in modified EBW RP-2 detonators, for one month at 75 °C. The PETN powder has been analyzed chemically using Fisher specific surface area analysis, SEM imaging and light scattering particle size analysis. Additionally the detonators were tested for performance through voltage-sweep threshold testing and function time measurements. Findings from the study indicate that aging at 75 °C for one month significantly changes the specific surface area and particle size of unstabilized PETN, leading to increases in detonator function time, but not detonator threshold values. Powders stabilized with TriPEON displayed less significant increases in function time, while powder stabilized with polysaccharide exhibited no aging effects, despite the high temperature aging.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
DOE OSTI2025

Dual aging pathways of Cu-SSZ-13 SCR catalysts: Hydrothermal vs. sulfur-induced deactivation

Hydrothermal aging (HTA) and chemical poisoning are two primary factors contributing to the real-world degradation of Cu-SSZ-13 SCR catalysts. Investigating field-returned samples offers valuable insights into performance degradation caused by these mechanisms. However, the simultaneous presence of both deactivation pathways complicates the isolation of their individual effects in post-mortem analyses. In this study, we separately prepared model Cu-SSZ-13 SCR catalysts subjected to hydrothermal-aging and sulfur-induced chemical poisoning. Using various characterization techniques, we elucidated the specific role of each aging process in catalyst deactivation and compared the results to real-world field-aged catalysts. Our findings show that hydrothermal aging at 650 °C for 100 h caused dealumination of the zeolite framework but no significant CuO x cluster formation. In contrast, sulfur aging (via sulfur exposure, calcination at 550 °C, and desulfation up to 750 °C) led to CuO x formation without any observable dealumination. On model catalysts, sulfur poisoning was found to reduce Cu mobility and the amount of active Cu sites, thus degrading catalyst activity. Although some activity was recovered upon desulfation, a portion of the initial catalyst activity remained irreversibly lost due to CuO x formation. We demonstrate that this occurs because sulfated species impede the ability of multi-nuclear Cu species (e.g., Cu dimers) to split back into their isolated form, leading to CuSO 4 -clusters that oxidatively desulfate to CuO x species. This degradation pathway explains the significant reduction in activity of field-aged samples, where substantial CuSO 4 -cluster accumulation leads to reduced active Cu and subsequent conversion to CuO x . Furthermore, the conclusions from model catalysts were extended directly to field-aged commercial samples, elucidating the decline in activity and chemical properties during field deployment.

Catalyst Deactivation↗
DOE OSTI2011

Older Age Predicts Decreased Metastasis and Prostate Cancer-Specific Death for Men Treated With Radiation Therapy: Meta-Analysis of Radiation Therapy Oncology Group Trials

Purpose: The impact of age on prostate cancer (PCa) outcome has been controversial; therefore, we analyzed the effect of age on overall survival (OS), distant metastasis, prostate cancer-specific death (PCSD), and nonprostate cancer death (NPCD) on patients with locally advanced PCa. Methods and Materials: Patients who participated in four Radiation Therapy Oncology Group (RTOG) phase III trials, 8531, 8610, 9202, and 9413, were studied. Cox proportional hazards regression was used for OS analysis, and cumulative events analysis with Fine and Gray's regression was used for analyses of metastasis, PCSD, and NPCD. Results: Median follow-up of 4,128 patients with median age of 70 (range, 43-88 years) was 7.3 years. Most patients had high-risk disease: cT3 to cT4 (54%) and Gleason scores (GS) of 7 (45%) and 8 to 10 (27%). Older age ({<=}70 vs. >70 years) predicted for decreased OS (10-year rate, 55% vs. 41%, respectively; p < 0.0001) and increased NPCD (10-year rate, 28% vs. 46%, respectively; p < 0.0001) but decreased metastasis (10-year rate, 27% vs. 20%, respectively; p < 0.0001) and PCSD (10-year rate, 18% vs. 14%, respectively; p < 0.0001). To account for competing risks, outcomes were analyzed in 2-year intervals, and age-dependent differences in metastasis and PCSD persisted, even in the earliest time periods. When adjusted for other covariates, an age of >70 years remained associated with decreased OS (hazard ratio [HR], 1.56 [95% confidence interval [CI], 1.43-1.70] p < 0.0001) but with decreased metastasis (HR, 0.72 [95% CI, 0.63-0.83] p < 0.0001) and PCSD (HR, 0.78 [95% CI, 0.66-0.92] p < 0.0001). Finally, the impact of the duration of androgen deprivation therapy as a function of age was evaluated. Conclusions: These data support less aggressive PCa in older men, independent of other clinical features. While the biological underpinning of this finding remains unknown, stratification by age in future trials appears to be warranted.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2016

Effects of Aging on Hippocampal Neurogenesis After Irradiation

Purpose: To assess the influence of aging on hippocampal neuronal development after irradiation (IR). Methods and Materials: Male mice, 2, 4, 6, 12, and 18 months of age, were given a single dose of 0 or 5 Gy of IR. A bromodeoxyuridine (BrdU) incorporation study was used to label newborn cells. Neural progenitors, newborn neurons, and microglia in dentate gyrus (DG) were identified by phenotypic markers, and their numbers were quantified by nonbiased stereology 9 weeks after IR. Results: BrdU-positive or newborn cells in DG decreased with aging and after IR. The number of neuroblasts and newborn neurons decreased with aging, and a further significant reduction was observed after IR. Total type 1 cells (the putative neural stem cells), and newborn type 1 cells decreased with aging, and further reduction in total type 1 cells was observed after IR. Aging-associated activation of microglia in hippocampus was enhanced after IR. Conclusions: The aging-associated decline in hippocampal neurogenesis was further inhibited after IR. Ablation of neural progenitors and activation of microglia may contribute to the inhibition of neuronal development after IR across all ages.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2021

Recycled polyethylene and crumb rubber composites modified asphalt with improved aging resistance and thermal stability

Crumb rubbers (CR) and recycled Polyethylene (PE) are commonly used as modifiers to improve the asphalt properties. However, the addition of these modifiers individually may result in phase separation of PE and inadequate degradation of CR, which may not simultaneously satisfy the rheological and aging resistance of the binder blends. In this study, a type of CR/PE composites manufactured through melt extrusion procedures was adopted for the improvement of the modified binder blends. The modified binder blends after short-term (RTFO) and long-term (PAV) aging were collected for dynamic shear rheometer and bending beam rheometer tests. FTIR tests were also used to quantify the aging resistance, while differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were applied to evaluate the thermal behaviors of the binder blends. Optical microscopy tests were used to explore the modification mechanism and visualize the microstructures of original and PAV aged binder blends. Test results showed that CR/PE composites could significantly improve the aging resistance of the binder blends. The dispersed PE particles still interacted with each other and meanwhile worked with the diffused rubbery phase, which could form a similar TPEs network. The oxidation and high-temperature aging of such binder blends would strengthen the network that resisted the aging severity of the binder blends. Furthermore, it was also revealed that CR/PE modified asphalt could sustain more heat before a rapid degradation and the well-dispersed PE particles could interact with the diffused CR particles to form a network to resist aging.

02 PETROLEUM↗
DOE OSTI2014

Strengthening of Cu–Ni–Si alloy using high-pressure torsion and aging

An age-hardenable Cu–2.9%Ni–0.6%Si alloy was subjected to high-pressure torsion. Aging behavior was investigated in terms of hardness, electrical conductivity and microstructural features. Transmission electron microscopy showed that the grain size is refined to ∼ 150 nm and the Vickers microhardness was significantly increased through the HPT processing. Aging treatment of the HPT-processed alloy led to a further increase in the hardness. Electrical conductivity is also improved with the aging treatment. It was confirmed that the simultaneous strengthening by grain refinement and fine precipitation is achieved while maintaining high electrical conductivity. Three dimensional atom probe analysis including high-resolution transmission electron microscopy revealed that nanosized precipitates having compositions of a metastable Cu{sub 3}Ni{sub 5}Si{sub 2} phase and a stable NiSi phase were formed in the Cu matrix by aging of the HPT-processed samples and these particles are responsible for the additional increase in strength after the HPT processing. - Highlights: • Grain refinement is achieved in Corson alloy the size of ∼150nm by HPT. • Aging at 300°C after HPT leads to further increase in the mechanical property. • Electrical conductivity reaches 40% IACS after aging for 100 h. • 3D-APT revealed the formation of nanosized-precipitates during aging treatment. • Simultaneous hardening in both grain refinement and precipitation is achieved.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Comparative study of structure formation and mechanical behavior of age-hardened Ti–Nb–Zr and Ti–Nb–Ta shape memory alloys

This work sets out to study the peculiar effects of aging treatment on the structure and mechanical behavior of cold-rolled and annealed biomedical Ti–21.8Nb–6.0Zr (TNZ) and Ti–19.7Nb–5.8Ta (TNT) (at.%) shape memory alloys by means of transmission electron microscopy, X-ray diffractometry, functional fatigue and thermomechanical testing techniques. Dissimilar effects of aging treatment on the mechanical behavior of Zr- and Ta-doped alloys are explained by the differences in the ω-phase formation rate, precipitate size, fraction and distribution, and by their effect on the alloys' critical stresses and transformation temperatures. Even short-time aging of the TNZ alloy leads to its drastic embrittlement caused by “overaging”. On the contrary, during aging of the TNT alloy, formation of finely dispersed ω-phase precipitates is gradual and controllable, which makes it possible to finely adjust the TNT alloy functional properties using precipitation hardening mechanisms. To create in this alloy nanosubgrained dislocation substructure containing highly-dispersed coherent nanosized ω-phase precipitates, the following optimum thermomechanical treatment is recommended: cold rolling (true strain 0.37), followed by post-deformation annealing (600 °C, 15–30 min) and age-hardening (300 °C, 30 min) thermal treatments. It is shown that in TNT alloy, pre-transition diffraction effects (diffuse reflections) can “mask” the β-phase substructure and morphology of secondary phases. - Highlights: • TNZ alloy is characterized by much higher ω-phase precipitation rate than TNT alloy. • Difference in precipitation rates is linked to the difference in Zr and Ta diffusion mobility. • Aging of nanosubgrained TNZ alloy worsens its properties irrespective of the aging time. • Aging time of nanosubgrained TNT alloy can be optimized to improve its properties.

36 MATERIALS SCIENCE↗
DOE OSTI2015

The effect of aging treatment on the fracture toughness and impact strength of injection molded Ni-625 superalloy parts

In this study, the effect of aging heat treatment on fracture toughness and impact strength of Ni-625 superalloy fabricated by using powder injection molding (PIM) method was examined. After a feedstock was prepared by mixing the prealloyed Ni-625 superalloy powder, which was fabricated by gas atomisation, with a polymeric binder system and then it was granulated, it was shaped through the use of injection. The molded specimens were sintered at 1300 °C for 3 h after a two-stage debinding process. Once the sintered specimens were treated in the solution at 1150 °C for 2 h, they were quenched. Aging treatment was performed by keeping specimens at 745 °C for 22 h. Fracture toughness and impact tests were performed on sintered and aged specimens. Microstructure examinations were performed by using optical microscope, scanning electron microscope, and transmission electron microscope. The results revealed that aging heat treatment led to the formation of some carbides and intermetallic phases in the microstructure. While the hardness of the aged specimens increased due to these phases, their fracture toughness and impact strength values decreased. - Highlights: • Ni-625 superalloy components were produced by means of powder injection molding. • The produced components were subjected to aging treatment. • Aging process provided approximately 50% increase in the hardness of components. • Intermetallic precipitates, carbides and TCP phases occurred within the aged parts. • Fracture toughness and impact strength values decreased due to the hard phases.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Precipitation behavior during aging and creep in 18Cr–9Ni–3Cu–Nb–N steel

Highlights: • The creep strength of 18Cr–9Ni–3Cu–Nb–N steel degraded in the long term. • Nb rich MX particles precipitated in grain interior after aging for just one hour at 650 to 800 °C. • The time required for precipitation of modified Z phase was about 2500 h at 650 °C and 1050 h at 700 °C. • Fine Cu particles were detected in grain interior after aging for one hour. • Large Cu particles were located at the interface between the σ phase and the matrix after long-term aging at 650 °C and 700 °C. - Abstract: Microstructural changes during aging and creep were investigated in 18Cr–9Ni–3Cu–Nb–N steel (KA-SUS304J1HTB, ASME Code Case 2328), focusing on copper phase, MX carbonitride and Z phase. The creep strength of 18Cr–9Ni–3Cu–Nb–N steel was much higher than that of conventional SUS304 steel in the short term. However, the difference of these two steels was small in the long term, because the creep strength of 18Cr–9Ni–3Cu–Nb–N steel degraded in the long term. Niobium rich MX particles precipitated in grain interior after aging for just one hour at 650 to 800 °C. Modified Z phase [Cr(Nb, V)N] particles were observed after aging accompanied by the disappearance of MX particles. The time required for precipitation of modified Z phase was about 2500 h at 650 °C and 1050 h at 700 °C. Fine copper particles were detected in grain interior after aging for one hour. Large copper particles were located at the interface between the σ phase and the matrix after long-term aging at 650 °C and 700 °C.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Statin-induced myotoxicity is exacerbated by aging: A biophysical and molecular biology study in rats treated with atorvastatin

Statin-induced skeletal muscle damage in rats is associated to the reduction of the resting sarcolemmal chloride conductance (gCl) and ClC-1 chloride channel expression. These drugs also affect the ClC-1 regulation by increasing protein kinase C (PKC) activity, which phosphorylate and close the channel. Also the intracellular resting calcium (restCa) level is increased. Similar alterations are observed in skeletal muscles of aged rats, suggesting a higher risk of statin myotoxicity. To verify this hypothesis, we performed a 4–5-weeks atorvastatin treatment of 24-months-old rats to evaluate the ClC-1 channel function by the two-intracellular microelectrodes technique as well as transcript and protein expression of different genes sensitive to statins by quantitative real-time-PCR and western blot analysis. The restCa was measured using FURA-2 imaging, and histological analysis of muscle sections was performed. The results show a marked reduction of resting gCl, in agreement with the reduced ClC-1 mRNA and protein expression in atorvastatin-treated aged rats, with respect to treated adult animals. The observed changes in myocyte-enhancer factor-2 (MEF2) expression may be involved in ClC-1 expression changes. The activity of PKC was also increased and further modulate the gCl in treated aged rats. In parallel, a marked reduction of the expression of glycolytic and mitochondrial enzymes demonstrates an impairment of muscle metabolism. No worsening of restCa or histological features was found in statin-treated aged animals. These findings suggest that a strong reduction of gCl and alteration of muscle metabolism coupled to muscle atrophy may contribute to the increased risk of statin-induced myopathy in the elderly. - Highlights: • This work characterizes the causes of atorvastatin related myotoxicity in aged rats. • Skeletal muscle chloride channel ClC-1 is a target of statin-induced side effects. • ClC-1 dysfunction is worsened by aging process. • Age-related changes of energy production contribute to statin-induced myotoxicity. • These findings suggest caution with statin therapy during aging.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2012

Morphological, molecular and functional differences of adult bone marrow- and adipose-derived stem cells isolated from rats of different ages

Adult mesenchymal stem cells have self-renewal and multiple differentiation potentials, and play important roles in regenerative medicine. However, their use may be limited by senescence or age of the donor, leading to changes in stem cell functionality. We investigated morphological, molecular and functional differences between bone marrow-derived (MSC) and adipose-derived (ASC) stem cells isolated from neonatal, young and old rats compared to Schwann cells from the same animals. Immunocytochemistry, RT-PCR, proliferation assays, western blotting and transmission electron microscopy were used to investigate expression of senescence markers. Undifferentiated and differentiated ASC and MSC from animals of different ages expressed Notch-2 at similar levels; protein-38 and protein-53 were present in all groups of cells with a trend towards increased levels in cells from older animals compared to those from neonatal and young rats. Following co-culture with adult neuronal cells, dMSC and dASC from animals of all ages elicited robust neurite outgrowth. Mitotracker{sup Registered-Sign} staining was consistent with ultrastructural changes seen in the mitochondria of cells from old rats, indicative of senescence. In conclusion, this study showed that although the cells from aged animals expressed markers of senescence, aged MSC and ASC differentiated into SC-like cells still retain potential to support axon regeneration. -- Highlights: Black-Right-Pointing-Pointer Aged MSC and ASC differentiated into Schwann-like cells support axon regeneration. Black-Right-Pointing-Pointer p53 expression does not appreciably influence the biology of Schwann or stem cells. Black-Right-Pointing-Pointer Notch 2 expression was similar in cells derived from animals of different ages. Black-Right-Pointing-Pointer Proliferation rates of dMSC varied little over time or with animal age.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2023

Estimating the Meridional Extent of Adiabatic Mixing in the Stratosphere Using Age-Of-Air

Wave-induced adiabatic mixing in the winter midlatitudes is one of the key processes impacting stratospheric transport. Understanding its strength and structure is vital to understanding the distribution of trace gases and their modulation under a changing climate. Age-of-air is often used to understand stratospheric transport, and this study proposes refinements to the vertical age gradient theory of Linz et al. (2021), https://doi.org/10.1029/2021JD035199. The theory assumes exchange of air between a well-mixed tropics and a well-mixed extratropics, separated by a transport barrier, quantifying the adiabatic mixing flux across the interface using age-based measures. These assumptions are re-evaluated and a refined framework that includes the effects of meridional tracer gradients is established to quantify the mixing flux. This is achieved, in part, by computing a circulation streamfunction in age-potential temperature coordinates to generate a complete distribution of parcel ages being mixed in the midlatitudes. The streamfunction quantifies the “true” age of parcels mixed between the tropics and the extratropics. Applying the revised theory to an idealized and a comprehensive climate model reveals that ignoring the meridional gradients in age leads to an underestimation of the wave-driven mixing flux. Stronger, and qualitatively similar fluxes are obtained in both models, especially in the lower-to-middle stratosphere. While the meridional span of adiabatic mixing in the two models exhibits some differences, they show that the deep tropical pipe, that is, latitudes equatorward of 15° barely mix with older midlatitude air. The novel age-potential temperature circulation can be used to quantify additional aspects of stratospheric transport.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2013

Photoinduced aging and viscosity evolution in Se-rich Ge-Se glasses

We propose here to investigate the non-equilibrium viscosity of Ge-Se glasses under and after light irradiation. Ge{sub 10}Se{sub 90} and Ge{sub 20}Se{sub 80} fibers have been aged in the dark and under ambient light, over months. During aging, both the relaxation of enthalpy and the viscosity have been investigated. The viscosity was measured by shear relaxation-recovery tests allowing the measurement of non-equilibrium viscosity. When Ge{sub 10}Se{sub 90} glass fibers are aged under irradiation, a relatively fast fictive temperature decrease is observed. Concomitantly, during aging under irradiation, the non-equilibrium viscosity increases and reaches an equilibrium after two months of aging. This viscosity increase is also observed in Ge{sub 20}Se{sub 80} fibers. Nevertheless, this equilibrium viscosity is far below the viscosity expected at the configurational equilibrium. As soon as the irradiation ceases, the viscosity increases almost instantaneously by about one order of magnitude. Then, if the fibers are kept in the dark, their viscosity slowly increases over months. The analysis of the shear relaxation functions shows that the aging is thermorheologically simple. On the other side, there is no simple relaxation between the shear relaxation functions measured under irradiation and those measured in the dark. These results clearly suggest that a very specific photoinduced aging process occurs under irradiation. This aging is due to photorelaxation. Nevertheless, the viscosity changes are not solely correlated to photoaging and photorelaxation. A scenario is proposed to explain all the observed viscosity evolutions under and after irradiation, on the basis of photoinduced transient defects.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Age and gender specific biokinetic model for strontium in humans

A biokinetic model for strontium in humans is necessary for quantification of internal doses due to strontium radioisotopes. The ICRP-recommended biokinetic model for strontium has limitation for use in a population study, because it is not gender specific and does not cover all age ranges. The extensive Techa River data set on 90Sr in humans (tens of thousands of measurements) is a unique source of data on long-term strontium retention for men and women of all ages at intake. These, as well as published data, were used for evaluation of age- and gender-specific parameters for a new compartment biokinetic model for strontium (Sr-AGe model). The Sr-AGe model has similar structure as the ICRP model for the alkaline earth elements. The following parameters were mainly reevaluated: gastro-intestinal absorption and parameters related to the processes of bone formation and resorption defining calcium and strontium transfers in skeletal compartments. The Sr-AGe model satisfactorily describes available data sets on strontium retention for different kinds of intake (dietary and intravenous) at different ages (0–80 years old) and demonstrates good agreement with data sets for different ethnic groups. The Sr-AGe model can be used for dose assessment in epidemiological studies of general population exposed to ingested strontium radioisotopes.

age dependence↗
DOE OSTI2017

Sex and age differences in the expression of liver microRNAs during the life span of F344 rats

Background: Physiological factors such as age and sex have been shown to be risk factors for adverse effects in the liver, including liver diseases and drug-induced liver injury. Previously, we have reported age- and sex-related significant differences in hepatic basal gene expression in rats during the life span that may be related to susceptibility to such adverse effects. However, the underlying mechanisms of the gene expression changes were not fully understood. In recent years, increasing evidence for epigenetic mechanisms of gene regulation has fueled interest in the role of microRNAs (miRNAs) in toxicogenomics and biomarker discovery. We therefore proposed that significant age and sex differences exist in baseline liver miRNA expression, and that comprehensive profiling of miRNAs will provide insights into the epigenetic regulation of gene expression in rat liver. Methods: To address this, liver tissues from male and female F344 rats were examined at 2, 5, 6, 8, 15, 21, 52, 78, and 104 weeks of age for the expression of 677 unique miRNAs. Following data processing, predictive pathway analysis was performed on selected miRNAs that exhibited prominent age and/or sex differences in expression. Results: Of the 314 miRNAs found to be expressed, 214 were differentially expressed; 65 and 212 miRNAs showed significant (false discovery rate (FDR) <5% and ≥1.5-fold change) sex- and age-related differences in expression, respectively. Thirty-eight miRNAs showed 2-week-specific expression, of which 31 miRNAs were found to be encoded within the Dlk1-Dio3 cluster located on chromosome 6. This cluster has been associated with tissue proliferation and differentiation, and liver energy homeostasis in postnatal development. Predictive pathway analysis linked sex-biased miRNA expression with sexually dimorphic molecular functions and toxicological functions that may reflect sex differences in hepatic physiology and disease. The expression of miRNAs (miR-18a, miR-99a, and miR-203, miR-451) was also found to associate with specific sexually dimorphic hepatic histopathology. The expression of miRNAs involved in regulating cell death, cell proliferation, and cell cycle was found to change as the rats matured from adult to old age. Conclusions: Overall, significant age- and sex-related differences in liver miRNA expression were identified and linked to histopathological findings and predicted functional pathways that may underlie susceptibilities to liver toxicity and disease.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Development of Cable Aging Acceptance Criteria for Nuclear Facilities

The aging of nuclear power plant electrical cables has been the subject of substantial research and development (R&D) projects in the nuclear industry, national and international laboratories, universities, and vendor organizations for several years. More specifically, these R&D efforts were conducted to develop equipment and techniques for assessing age-related degradation of in-service cables in nuclear facilities including power plants, research reactors, waste facilities and fuel fabrication plants. In recent years, cable R&D efforts in the nuclear arena have also included work to develop new cables for the next generation of reactors. Over time, exposure to harsh environmental conditions such as elevated temperatures, radiation, and humidity in nuclear installations can result in age-related degradation and failure of cables. In the current fleet of nuclear reactors, there are thousands of miles of cabling installed in each plant and many of these cables are exposed to these harsh environmental conditions. For these cables, the jacket and insulation polymers harden and become brittle over time, making them more susceptible to crack formation and growth, moisture intrusion, and other mechanisms that can lead to cable failure. Moreover, the existing U.S. fleet of 98 nuclear reactors has an average operating age of 38 years. Many of these nuclear power plants have applied for and almost all have been granted regulatory approval for license renewals to operate for 60 years, 20 years beyond their original 40-year life. Further, subsequent license renewals (SLRs) are underway with a few commercial nuclear power sites already approved to operate up to 80 years. As these reactors pursue operating life extensions, utilities must find a way to address issues associated with age-related degradation of cables. Designers of small modular reactors are also in need of technologies to evaluate the performance of cables that will be installed in harsher environments (e.g. higher temperatures, radiation doses, dose rates, etc.) than those present in current-generation reactors. Today, a variety of cable condition monitoring (CM) techniques have been developed and successfully used in nuclear facilities. These techniques are used to identify age-related degradation and assess the condition of cables to determine if their performance characteristics have changed with age. However, objective criteria must be developed for these CM tests to help quantify cable condition and thereby develop repair and replacement schedules. With operating life extending to 80 years and more SLRs on the horizon, both nuclear facilities and regulators need an objective means to determine the aged condition of cables.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Complete Iodine Loading of NO-Aged Ag 0 -Functionalized Silica Aerogel (Milestone Report)

In off-gas treatment systems within a nuclear fuel reprocessing plant, capture materials will be exposed to a gas stream for extended periods during their lifetime. This gas stream may be at elevated temperature and could contain water, NO x gas, or a variety of other constituents. For this reason, it is important to understand the effects of long-term exposure, or aging, on proposed capture materials. One material under consideration for iodine sequestration is silver-functionalized silica aerogel (Ag 0 -aerogel). The aim of this study was to determine the effect of extended exposure at 150°C to an air stream containing NO on the iodine capture capacity of Ag 0 -aerogel. Ag 0 -aerogel was provided by the Pacific Northwest National Laboratory (PNNL), which manufactures the material at a lab scale. Prior to aging, the material has an iodine loading capacity of approximately 290 mg I/g Ag 0 -aerogel. Previous studies have aged the material in a dry air stream or in a moist air stream for up to 6 months. Both tests resulted in a 22% loss in iodine capacity. Aging the material in a static 2% NO 2 environment for up to 2 months results in a 15% loss of iodine capacity.3 In this study, exposure of Ag 0 -aerogel to 1% NO at 150°C for 2 months produced a loss of 43% in iodine loading capacity. This is largest loss observed for aerogel aging studies to date. The performance of Ag 0 -aerogel in this study was compared to the performance of reduced silver mordenite (Ag 0 Z) in similar studies. Ag 0 Z is a zeolite mineral considered to be the current standard technology for iodine removal from off-gas streams of a potential US used fuel processing plant. In an aging study exposing Ag 0 Z to 1% NO for 2 months, an iodine capacity loss of over 80% was observed. This corresponds to a silver utilization of 13.5% for 2 month NO-aged Ag 0 Z, compared to 57% silver utilization for 2 month NO-aged aerogel. While iodine loading capacity and silver utilization are critical parameters in evaluating these materials, other properties must also be considered when selecting the appropriate material (e.g., relative material densities and potential waste form production technology). The resistance of Ag 0 -aerogel to NO is promising, and investigations of this material for use in iodine capture should continue to be pursued.

36 MATERIALS SCIENCE↗