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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 883 records · Page 49
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Experimental Characterization of Hygrothermal Aging: Competition Between Thermo-Oxidation and Hydrolysis Phenomena

Abstract In this work, we have presented a comparison between effects of accelerated thermo-oxidative, hydrolytic and hygrothermal aging on the mechanical and chemical properties of a polyurethane based (PUB) adhesive. The adhesive is a flexible adhesive which is extensively used in automobile industry as a glass sealant. During service life it gets exposed to the hygrothermal environment and the integrity of matrix interface is most vulnerable. This study focuses on weighing and comparing effects of different aging environments on material behavior; and it shows that hygrothermal aging environment results as a competition between two sub-aging phenomena i.e., thermo-oxidation and hydrolytic aging. Samples were exposed to 0%RH, 80%RH and submerged condition in distilled water. Uni-axial tensile tests, and cross-link density analysis by swelling test were carried out on as-received and aged samples. The aging process was conducted at three different temperatures (60°C, 80°C and 95°C) and for four different exposure durations of 1, 10, 30, and 90 days. This work confirms that the effect of hygrothermal aging is a result of competition between thermo-oxidation and hydrolytic aging environments. The total mechanical and environmental damage incurred by specimens is a collaborative effect of all exposure environments involved i.e., aging time, temperature, oxygen, water and humidity. The results are in agreement with the chemical test outcomes as well.

Shaafaey, Mamoon↗
NASA NTRS1981

Development of a high-temperature durable catalyst for use in catalytic combustors for advanced automotive gas turbine engines

Durable catalytic reactors for advanced gas turbine engines were developed. Objectives were: to evaluate furnace aging as a cost effective catalytic reactor screening test, measure reactor degradation as a function of furnace aging, demonstrate 1,000 hours of combustion durability, and define a catalytic reactor system with a high probability of successful integration into an automotive gas turbine engine. Fourteen different catalytic reactor concepts were evaluated, leading to the selection of one for a durability combustion test with diesel fuel for combustion conditions. Eight additional catalytic reactors were evaluated and one of these was successfully combustion tested on propane fuel. This durability reactor used graded cell honeycombs and a combination of noble metal and metal oxide catalysts. The reactor was catalytically active and structurally sound at the end of the durability test.

Tong, H.↗
NASA NTRS1992

The effect of space environment on the development and aging of Drosophila Melanogaster (7-IML-1)

This experiment involves the study of the development of eggs of the fly, Drosophila, exposed to microgravity. It is presumed that oogenesis, rather than further states of embryonic development, is sensitive to gravity. This hypothesis will be tested by collecting eggs layered at specific times inflight and postflight from flies exposed to 0 and 1 g. This portion of the experiment is a repetition of an earlier experiment flown in Biorack during the Spacelab D1 Mission. An added feature of the experiment for the First International Microgravity Laboratory (IML-1) Mission is to study the effect of microgravity on the life span of Drosophila male flies. Various aspects of the investigation are discussed.

Marco, Roberto↗
DOE OSTI2021

Aging mechanisms of filled cross-linked polyethylene (XLPE) cable insulation material exposed to simultaneous thermal and gamma radiation

Thermal and simultaneous thermal and gamma radiation aging experiments were conducted on an industry grade cross-linked polyethylene (XLPE) cable insulation material, which is a composite material with XLPE as polymer matrix and various additives and fillers. Reverse engineering was conducted to identify and quantify the material composition given that this information was not revealed by the cable manufacture. Samples were then aged at temperatures of 60, 90, and 115 °C, exposed to gamma radiation for total doses of 0 to 324 kGy, and at dose rates of 0 to 540 Gy/h. Aging mechanisms were studied using various materials characterization techniques including pyrolysis gas chromatography mass spectrometry (Py-GCMS), differential scanning calorimetry (DSC), nuclear magnetic resonance spectroscopy (NMR), and gel-fraction tests. Results show that the flame-retardant components were decomposed into smaller molecules when the material was exposed to gamma radiation, while no changes were observed when the samples were aged thermally without gamma radiation. With exposure to gamma radiation, the crystalline phase of the XLPE were damaged by gamma radiation introducing defects in the crystals, resulting in smaller and less perfect crystals. The dominance of chain scission or chain reformation process largely depends on the chain mobility, which is decided by the aging temperature. Chain scission was seen to dominate when the material was exposed to gamma radiation at 60 °C. Chain cross-linking slightly dominated when the material was exposed to gamma radiation at 90 °C and became more dominant with exposure to gamma radiation at 115 °C. No significant change to the XLPE polymer matrix was observed when the samples were exposed to thermal aging without gamma radiation. Finally, antioxidant is more effective in protecting the XLPE polymer matrix under thermal aging, but less effective with sample exposure to gamma radiation.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
NASA NTRSDate not supplied

Behavioral consequences of low dose radiation and sex differences in MCAT mouse model

Our study used 1-year old C57BL/6NJ male and female mice (astronaut-relevant age) that underwent exposure to 0.5 gray of gamma radiation and were euthanized 12 weeks after. In this study, we used an MCAT mouse model for mitochondrial ROS quenching, which overexpress human catalase. MCAT mice were shown to live longer and age better. Hence, in this study we determined whether quenching ROS in the mitochondria will mitigate the adverse effects of ionizing radiation exposure on spaceflight-relevant tissues. As part of the analysis, we have completed 5 different behavioral tests which focus on memory, physical stance, stress, anxiety, and other mission relevant behaviors. In the Neuro-score battery, performed after both 1and 8 weeks post IR we saw that all female groups had significantly higher scores compared to males. When comparing the baseline vs 8 weeks of radiation, we saw that all the male groups (including the sham) had lower neuro-score, pointing out to aging effect in addition to IR. In the female groups only the female IR group had lower neuro-score and the MCAT group was protected from this effect. In the Nestlet building test we saw similarly that only females were affected by radiation, having lower scores and this effect was mitigated in the MCAT animals as well. In the Catwalk test we saw that females were faster, had higher swing speed and stride length in all four paws. Males had higher stand, step cycle and max contact area. Aging is associated with slowing of gait speed, swing speed and shortening of stride length which we see in males, this is consistent with physical appearance where males look markedly older. In the Light-Dark Box test we saw that females were more frequently present in the light side and altered zones more frequently, pointing out to a more exploratory and less anxious pattern of behavior. Similarly, to what was detected in the Nest building and Neuro-score test, in the Barnes maze test, during the acquisition phase (learning) we saw that IR affected more the females who did not do better in the maze after 4 days. On the other hand, during the probe phase of the test (spatial memory) the females visited the target hole and the box quadrant more often, but also had more errors vs males, which points out to possible serial escape vs spatial escape strategy. Overall, we see that older females look physically better are faster and perform better almost in all behavioral tests compared to their male counterparts. On the other hand, they are more sensitive to low dose radiation in many cases, in some cases this effect was mitigated in the MCAT model pointing out to the importance of ROS in these stressors. In the near future we will focus on corelating these behavioral tests with molecular findings such as for example brain IHC, plasma and hippocampal cytokines in order to find specific biomarkers for behavioral deficits.

radiation↗
DOE OSTI2017

Drivers of terrestrial plant production across broad geographical gradients

Abstract Terrestrial net primary production (NPP) varies across global climate gradients, but the mechanisms through which climate drives this variation remain subject to debate. Specifically, it is debatable whether NPP is primarily influenced by ‘direct’ effects of climate on the kinetics of plant metabolism or ‘indirect’ effects of climate on plant size, stand biomass, stand age structure and growing season length. We clarify several issues in this debate by presenting multiple lines of evidence that support a primarily indirect influence of climate on global variation in NPP across broad geographical gradients. First, we highlight > 60 years of research that suggests leaf area, growing season length, plant biomass and/or plant age are better predictors of NPP than climate or latitude. Second, we refute recent claims that using biomass and age as predictors of NPP represents circular reasoning. Third, we illustrate why effects of climate on the kinetics of plant production must be evaluated using instantaneous (not annualized) rates of productivity. Fourth, we review recent analyses showing that the effects of biomass and age on NPP are much stronger than the effects of climate. Fifth, we present new analyses of a high‐quality NPP dataset that demonstrate further that biomass, age and growing season length are better predictors of global variation in NPP than climate variables. Our results are consistent with the hypothesis that variation in NPP across global climate gradients primarily reflects the influence of climate on growing season length and stand biomass, as well as stand age, rather than the effects of temperature and precipitation on the kinetics of metabolism. However, this hypothesis should be evaluated further using larger, high‐quality observational and experimental datasets spanning multiple geographical scales.

Michaletz, Sean T.↗
NASA NTRS1977

Diogenite exposure ages

He, Ne and Ar isotopes have been measured in six, and Al-26 in two diogenites. Cosmic-ray exposure ages corrected for shielding effects using Ne-22/Ne-21 ratios are generally concordant. Five diogenites have a group age of 14 Myr and three others may have a group age of 24 Myr, implying that two collisions may have produced 8 of the 9 diogenites.

Herzog, G. F.↗
DOE OSTI2025

Improved representation of black carbon mixing structures suggests stronger direct radiative heating

Black carbon significantly influences the Earth system because of its strong solar radiation absorption. However, its direct radiative effect remains poorly understood in current climate models, partly because current climate models oversimplify the diverse structures formed when black carbon mixes with other atmospheric components. Here we show that incorporating more realistic, multi-mixing-structure representations of black carbon increases the direct radiative effect. We find that aged black carbon particles, with thicker coatings and higher embedded fractions, enhance the direct radiative effect more efficiently. Using machine learning alongside the Community Earth System Model, we show that the direct radiative effect at the top of the atmosphere in regions with heavy black carbon pollution is 31.6% greater when multi-mixing structures are considered. These findings highlight the importance of modeling complex mixing structures of particle-resolved black carbon to accurately capture their warming impacts on global atmosphere, particularly in highly polluted regions.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2014

Soiling of building envelope surfaces and its effect on solar reflectance – Part II: Development of an accelerated aging method for roofing materials

Highly reflective roofs can decrease the energy required for building air conditioning, help mitigate the urban heat island effect, and slow global warming. However, these benefits are diminished by soiling and weathering processes that reduce the solar reflectance of most roofing materials. Soiling results from the deposition of atmospheric particulate matter and the growth of microorganisms, each of which absorb sunlight. Weathering of materials occurs with exposure to water, sunlight, and high temperatures. This study developed an accelerated aging method that incorporates features of soiling and weathering. The method sprays a calibrated aqueous soiling mixture of dust minerals, black carbon, humic acid, and salts onto preconditioned coupons of roofing materials, then subjects the soiled coupons to cycles of ultraviolet radiation, heat and water in a commercial weatherometer. Three soiling mixtures were optimized to reproduce the site-specific solar spectral reflectance features of roofing products exposed for 3 years in a hot and humid climate (Miami, Florida); a hot and dry climate (Phoenix, Arizona); and a polluted atmosphere in a temperate climate (Cleveland, Ohio). A fourth mixture was designed to reproduce the three-site average values of solar reflectance and thermal emittance attained after 3 years of natural exposure, which the Cool Roof Rating Council (CRRC) uses to rate roofing products sold in the US. This accelerated aging method was applied to 25 products₋single ply membranes, factory and field applied coatings, tiles, modified bitumen cap sheets, and asphalt shingles₋and reproduced in 3 days the CRRC's 3-year aged values of solar reflectance. In conclusion, this accelerated aging method can be used to speed the evaluation and rating of new cool roofing materials.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2015

Age at exposure and attained age variations of cancer risk in the Japanese A-bomb and radiotherapy cohorts

Purpose: Phenomenological risk models for radiation-induced cancer are frequently applied to estimate the risk of radiation-induced cancers at radiotherapy doses. Such models often include the effect modification, of the main risk to radiation dose response, by age at exposure and attained age. The aim of this paper is to compare the patterns in risk effect modification by age, between models obtained from the Japanese atomic-bomb (A-bomb) survivor data and models for cancer risks previously reported for radiotherapy patients. Patterns in risk effect modification by age from the epidemiological studies of radiotherapy patients were also used to refine and extend the risk effect modification by age obtained from the A-bomb survivor data, so that more universal models can be presented here. Methods: Simple log-linear and power functions of age for the risk effect modification applied in models of the A-bomb survivor data are compared to risks from epidemiological studies of second cancers after radiotherapy. These functions of age were also refined and fitted to radiotherapy risks. The resulting age models provide a refined and extended functional dependence of risk with age at exposure and attained age especially beyond 40 and 65 yr, respectively, and provide a better representation than the currently available simple age functions. Results: It was found that the A-bomb models predict risk similarly to the outcomes of testicular cancer survivors. The survivors of Hodgkin’s disease show steeper variations of risk with both age at exposure and attained age. The extended models predict solid cancer risk increase as a function of age at exposure beyond 40 yr and the risk decrease as a function of attained age beyond 65 yr better than the simple models. Conclusions: The standard functions for risk effect modification by age, based on the A-bomb survivor data, predict second cancer risk in radiotherapy patients for ages at exposure prior to 40 yr and attained ages before 55 yr reasonably well. However, for larger ages, the refined and extended models can be applied to predict the risk as a function of age.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

Combined effect of NaAlO2 and NaOH on the early age hydration of Portland cement with a high concentration of borate solution

The early age hydration of ordinary Portland cement in 5 M borate solution, with or without the addition of NaAlO{sub 2} and/or NaOH, was investigated. Hydration was measured using calorimetry, X-ray diffraction, thermogravimetric analysis, {sup 11}B and {sup 27}Al magic angle spinning NMR analysis, and scanning transmission electron microscopy. The purpose of this study was to reveal the mechanisms behind the retardation caused by a high concentration borate solution and the restoration of hydration through the combined addition of NaOH and NaAlO{sub 2}. Amorphous ulexite, which formed on the surface of the cement particles and prevented the further dissolution of anhydrous phases, was identified as the retardation product. The mechanism of the combined addition of NaAlO{sub 2} and NaOH in overcoming retardation was to transform amorphous ulexite into B-AFt and gowerite (CaB{sub 6}O{sub 10}·5H{sub 2}O). Formation of gowerite is favorable because of the much higher boron immobilization capacity in weight percentage, comparing to usual boron-containing phases reported previously.

36 MATERIALS SCIENCE↗
DOE OSTI2018

The Life Cycle of Anvil Clouds and the Top-of-Atmosphere Radiation Balance over the Tropical West Pacific

Observations from a geostationary satellite are used to study the life cycle of mesoscale convective systems (MCS), their associated anvil clouds, and their effects on the radiation balance over the warm pool of the tropical western Pacific Ocean. In their developing stages, MCS primarily consist of clouds that are optically thick and have a negative net cloud radiative effect (CRE). As MCS age, ice crystals in the anvil become larger, the cloud top lowers somewhat, and cloud radiative effects decrease in magnitude. Shading from anvils causes cool anomalies in the underlying sea surface temperature (SST) of up to −0.6°C. MCS often occur in clusters that are embedded within large westward-propagating disturbances, and therefore shading from anvils can cool SSTs over regions spanning hundreds of kilometers. Triggering of convection is more likely to follow a warm SST anomaly than a cold SST anomaly on a time scale of several days. This information is used to evaluate hypotheses for why, over the warm pool, the average shortwave and longwave CRE are individually large but nearly cancel. The results are consistent with the hypothesis that the cancellation in CRE is caused by feedbacks among cloud albedo, large-scale circulation, and SST.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

The effect of barrier films and exposure on the aging of vacuum insulation panels with fumed silica cores

Vacuum insulation panels have very low thermal conductivities compared to conventional insulation materials. The reduction of the core pressure significantly lowers gas phase conduction and overall thermal conductivity. As a consequence, increases in gas pressure can significantly increase thermal conductivity of the VIP. In addition, the thermal conductivity of the core is sensitive to moisture content. For vacuum insulation panels with fumed silica cores, work shows that the measured thermal conductivity increases by 0.5 x 10-3 W/mK per mass percent increase in water content [1]. This is significant since the thermal conductivity of vacuum insulation panels with fumed silica cores is in the range of 0.004 W/mK. This work investigates the long-term behavior of vacuum insulation panels comprised of fumed silica cores with polymer (ethylene vinyl alcohol) and metalized (aluminized) barrier films exposed to different exposure conditions: ambient conditions; exterior conditions in a mixed humid climate; and 24oC and 80 percent relative humidity. Results show that the increase in thermal conductivity is more pronounced for vacuum insulation panels made using polymer barrier films compared to the same panel protected by a metalized film. The increase is more pronounced when exposed to high relative humidity, 80 percent. After almost two years exposure, the decrease in thermal conductivity for vacuum insulation panels protected by a metalized barrier films are between 4 and 11 percent depending on exposure condition. The smallest decrease is for ambient conditions where the largest decrease is for exposure to 80 percent relative humidity. Similar behavior was observed for panels protected using polymer films, except the decrease in thermal conductivity was significantly higher, between approximately 20 and 60 percent, in the same order as for panels protected by metalized films. Measurements are ongoing with an attempt to develop a better relationship between these types of tests and vacuum insulation panel service life.

Aldykiewicz Jr, Antonio↗
DOE OSTI2021

Accuracy of Tau Positron Emission Tomography as a Prognostic Marker in Preclinical and Prodromal Alzheimer Disease: A Head-to-Head Comparison Against Amyloid Positron Emission Tomography and Magnetic Resonance Imaging

Importance: Tau positron emission tomography (PET) tracers have proven useful for the differential diagnosis of dementia, but their utility for predicting cognitive change is unclear. Objective: To examine the prognostic accuracy of baseline fluorine 18 ( 18 F)-flortaucipir and [18F]RO948 (tau) PET in individuals across the Alzheimer disease (AD) clinical spectrum and to perform a head-to-head comparison against established magnetic resonance imaging (MRI) and amyloid PET markers. Design, setting, and participants: This prognostic study collected data from 8 cohorts in South Korea, Sweden, and the US from June 1, 2014, to February 28, 2021, with a mean (SD) follow-up of 1.9 (0.8) years. A total of 1431 participants were recruited from memory clinics, clinical trials, or cohort studies; 673 were cognitively unimpaired (CU group; 253 [37.6%] positive for amyloid-β [Aβ]), 443 had mild cognitive impairment (MCI group; 271 [61.2%] positive for Aβ), and 315 had a clinical diagnosis of AD dementia (315 [100%] positive for Aβ). Exposures: [ 18 F]Flortaucipir PET in the discovery cohort (n = 1135) or [ 18 F]RO948 PET in the replication cohort (n = 296), T1-weighted MRI (n = 1431), and amyloid PET (n = 1329) at baseline and repeated Mini-Mental State Examination (MMSE) evaluation. Main outcomes and measures: Baseline [ 18 F]flortaucipir/[ 18 F]RO948 PET retention within a temporal region of interest, MRI-based AD-signature cortical thickness, and amyloid PET Centiloids were used to predict changes in MMSE using linear mixed-effects models adjusted for age, sex, education, and cohort. Mediation/interaction analyses tested whether associations between baseline tau PET and cognitive change were mediated by baseline MRI measures and whether age, sex, and APOE genotype modified these associations. Results: Among 1431 participants, the mean (SD) age was 71.2 (8.8) years; 751 (52.5%) were male. Findings for [ 18 F]flortaucipir PET predicted longitudinal changes in MMSE, and effect sizes were stronger than for AD-signature cortical thickness and amyloid PET across all participants (R 2 , 0.35 [tau PET] vs 0.24 [MRI] vs 0.17 [amyloid PET]; P < .001, bootstrapped for difference) in the Aβ-positive MCI group (R2, 0.25 [tau PET] vs 0.15 [MRI] vs 0.07 [amyloid PET]; P < .001, bootstrapped for difference) and in the Aβ-positive CU group (R 2 , 0.16 [tau PET] vs 0.08 [MRI] vs 0.08 [amyloid PET]; P < .001, bootstrapped for difference). These findings were replicated in the [ 18 F]RO948 PET cohort. MRI mediated the association between [ 18 F]flortaucipir PET and MMSE in the groups with AD dementia (33.4% [95% CI, 15.5%-60.0%] of the total effect) and Aβ-positive MCI (13.6% [95% CI, 0.0%-28.0%] of the total effect), but not the Aβ-positive CU group (3.7% [95% CI, -17.5% to 39.0%]; P = .71). Age (t = -2.28; P = .02), but not sex (t = 0.92; P = .36) or APOE genotype (t = 1.06; P = .29) modified the association between baseline [ 18 F]flortaucipir PET and cognitive change, such that older individuals showed faster cognitive decline at similar tau PET levels. Conclusions and relevance: The findings of this prognostic study suggest that tau PET is a promising tool for predicting cognitive change that is superior to amyloid PET and MRI and may support the prognostic process in preclinical and prodromal stages of AD.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

The Effect of Bainite Type on the Evolution of Carbide Constituent During an Accelerated Aging in Cr-Mo-V Steel

This paper aims to understand the effect of the type of bainite (i.e., the lower, the upper and the granular, developed by bainitic hardening at 550, 650 and 750 °C, respectively) on the evolution of carbide constituent due to a subsequent aging (at 700 °C for up to 500 h). The secondary carbides were identified by x-ray diffraction in the configurations of M{sub 3}C, M{sub 7}C{sub 3}, M{sub 23}C{sub 6}, M{sub 2}C, M{sub 6}C and MC (M=Fe, Cr, Mo, Mn and V), which varied with the time of aging. Despite that the three types of bainites shared similar constituent of carbides after the aging for 2-100 h, the constituent of the upper bainite (M{sub 7}C{sub 3} + M{sub 23}C{sub 6} + MC) was different from that of granular bainite and lower bainite (M{sub 7}C{sub 3} + M{sub 23}C{sub 6} + MC + M{sub 6}C) after the aging for 500 h. The concentration of the enrichment of alloying elements in ferrite matrix plays a dominant role in governing the precipitation of carbides in the aged steel.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Evaluation of the toxic effects of celecoxib on Xenopus embryo development

Highlights: • Celecoxib is a non-steroidal anti-inflammatory drug that inhibits cyclooxygenase-2. • Celecoxib produced significant toxic and teratogenic effects in Xenopus embryos. • Embryo organ-specific pathology was consistent with gene expression changes. • Celecoxib inhibited pericyte activity and cardiovascular development. • The safety of celecoxib use in pregnant women requires careful analysis. Celecoxib is a non-steroidal anti-inflammatory drug that selectively inhibits cyclooxygenase-2 and is prescribed for severe pain and inflammation. The excellent therapeutic effects of celecoxib mean that it is frequently used clinically, including for women of child-bearing age. However, the prenatal effects of this compound have not been studied extensively in vertebrates. The present study examined the developmental toxicity of celecoxib using a frog embryo teratogenic assay-Xenopus (FETAX). In addition, we examined its effects on cell migration using co-cultures of human umbilical vein endothelial cells and 10T1/2 cells. These studies revealed that celecoxib induced concentration-dependent mortality and various malformations of the Xenopus internal organs, including gut miscoiling, haemorrhage, and oedema. Celecoxib also downregulated the expression of vascular wall markers (Msr and alpha smooth muscle actin) and other organ-specific markers (Nkx2.5, Cyl104 and IFABP). In vitro co-culture studies revealed that celecoxib inhibited pericyte migration and differentiation into vascular smooth muscle cells. In conclusion, celecoxib was both toxic and teratogenic in Xenopus embryos, where it produced serious heart and vessel malformation by inhibiting vascular wall maturation and vascular network formation.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Coupled Physics Simulation of Expansive Reactions in Concrete with the Grizzly Code

The Grizzly code is being developed under the US Department of Energy’s Light Water Sustainability program as a tool to model aging mechanisms and their effects on the integrity of critical nuclear power plant components. An important application for Grizzly is the modeling of aging in concrete structures, which can be due to a number of mechanisms. Initial focus in this area has been on modeling expansive reactions due to alkali-silica reactions or radiation-induced volumetric expansion. Grizzly is an inherently multiphysics modeling platform that naturally permits including the effects of multiple coupled physics in a simulation. Models have been developed for transport of heat and moisture in concrete, and these have been coupled and used as inputs to models for expansive reactions. This paper summarizes this capability as well as work currently underway to couple it with mechanical deformation models that account for nonlinear constitutive behavior.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2015

Radiation Effects on Mortality from Solid Cancers Other than Lung, Liver, and Bone Cancer in the Mayak Worker Cohort: 1948–2008

Radiation effects on mortality from solid cancers other than lung, liver, and bone cancer in the Mayak worker cohort: 1948–2008. The cohort of Mayak Production Association (PA) workers in Russia offers a unique opportunity to study the effects of prolonged low dose rate external gamma exposures and exposure to plutonium in a working age population. We examined radiation effects on the risk of mortality from solid cancers excluding sites of primary plutonium deposition (lung, liver, and bone surface) among 25,757 workers who were first employed in 1948–1982. During the period 1948–2008, there were 1,825 deaths from cancers other than lung, liver and bone. Using colon dose as a representative external dose, a linear dose response model described the data well. The excess relative risk per Gray for external gamma exposure was 0.16 (95% CI: 0.07 – 0.26) when unadjusted for plutonium exposure and 0.12 (95% CI 0.03 – 0.21) when adjusted for plutonium dose and monitoring status. There was no significant effect modification by sex or attained age. Plutonium exposure was not significantly associated with the group of cancers analyzed after adjusting for monitoring status. Site-specific risks were uncertainly estimated but positive for 13 of the 15 sites evaluated with a statistically significant estimate only for esophageal cancer. Comparison with estimates based on the acute exposures in atomic bomb survivors suggests that the excess relative risk per Gray for prolonged external exposure in Mayak workers may be lower than that for acute exposure but, given the uncertainties, the possibility of equal effects cannot be dismissed.

60 APPLIED LIFE SCIENCES↗