Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “aging”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 703 records · Page 39
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Effect of Aging Treatment on the Precipitation Behavior and Mechanical Properties of Mg-9Gd-3Y-1.5Zn-0.5Zr Alloy

Aging heat treatments of an extruded Mg-9Gd-3Y-1.5Zn-0.5Zr (wt.%) alloy at 200, 225, and 250 °C for various times were studied. The results show that dynamic recrystallization (DRX) occurred during the extrusion process and the alloy exhibited a significant aging hardening response at temperatures ranging from 200 to 225 °C. The precipitation sequence of the alloy at 225 °C was supersaturated solid solution (SSSS) → β″ (D0{sub 19}, Mg{sub 3}RE) → β′ (bco, Mg{sub 15}RE{sub 3}), where the β′ phase was the primary precipitated phase. A large amount of discontinuous lamellar-shaped 14H-structure long period stacking ordered (LPSO) phase was also observed in the α-Mg matrix before and after aging treatments. Owing to the combined strengthening effect of fine DRXed grains, β′ nanoparticles, and widespread LPSO phases, the ultimate tensile strength and tensile yield strength of the peak-aged extruded alloy reached 409 and 303 MPa, respectively. The elongation in this circumstance was ~7.1%, which was slightly lower than that of the alloy before aging treatment.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Microstructure, Corrosion and Magnetic Behavior of an Aged Dual-Phase Stainless Steel

In the present work, the effect of the precipitation phenomena on corrosion and magnetic behavior of an aged dual-phase stainless steel was investigated. Aging treatment caused the precipitation of the σ phase, chromium carbides and secondary austenite, which was accompanied by the shifting of the δ/γ interfaces inside the δ ferrite grains. Aging between 700 and 850 °C strongly deteriorated the pitting corrosion resistance of the studied material. Magnetic investigation of the aged material using the vibration sample magnetic technique revealed the sensitivity of the intrinsic magnetic properties to the smallest microstructural change. This was confirmed by the Eddy current technique that led also to the evaluation of the aging-induced localized corrosion.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Determination of Gray Cast Iron Age Strengthening by Nondestructive Methods: Effect of Alloying Elements

Gray cast iron age strengthening is a phenomenon known as a modification of the alloy’s structure by iron-nitride precipitation during few days after casting. It generates an evolution of cast iron mechanical properties as a gain of hardness and Young’s modulus. In a first time, this article presents the possibility to monitor the aging time and the intensity of age strengthening using two nondestructive methods: nonstandard Rockwell hardness and inert frequencies measurement. In a second time, the study shows the influence of the alloying elements on this phenomenon and particularly the influence of free nitrogen amount, which is a first-order parameter to control aging. Finally, a prediction model of the time and the intensity of age strengthening has been elaborated using the results of the two different monitoring described.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Prevalence of Modifiable Cancer Risk Factors Among U.S. Adults Aged 18–44 Years

Introduction: Carcinogen exposure and unhealthy habits acquired in young adulthood can set the stage for the development of cancer at older ages. This study measured the current prevalence of several cancer risk factors among young adults to assess opportunities to intervene to change the prevalence of these risk factors and potentially reduce cancer incidence. Methods: Using 2015 National Health Interview Survey data (analyzed in 2016), the prevalence of potential cancer risk factors was estimated among U.S. adults aged 18–44 years, based on responses to questions about diet, physical activity, tobacco product use, alcohol, indoor tanning, sleep, human papillomavirus vaccine receipt, and obesity, stratified by sex, age, and race/ethnicity. Results: The prevalence of some risk factors varied by age and race/ethnicity. Obesity (one in four people) and insufficient sleep (one in three people) were common among men and women. Physical inactivity (one in five men, one in four women); binge drinking (one in four men, one in eight women); cigarette smoking (one in five men, one in seven women); and frequent consumption of red meat (one in four men, one in six women) also were common. More than half of the population of adults aged 18–44 years consumed sugar-sweetened beverages daily and processed meat at least once a week. Most young adults had never had the human papillomavirus vaccine. Conclusions: Findings can be used to target evidence-based environmental and policy interventions to reduce the prevalence of cancer risk factors among young adults and prevent the development of future cancers.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

Exposure to mercury among Spanish preschool children: Trend from birth to age four

The purpose of this study is to describe the total hair mercury concentrations and their determinants in preschool Spanish children, as well as to explore the trend in mercury exposure from birth to the age four. This evolution has been scarcely studied in other birth cohort studies. The study population was 580 four year old children participating in the INMA (i.e. Childhood and Environment) birth cohort study in Valencia (2008–2009). Total mercury concentration at age four was measured in hair samples by atomic absorption spectrometry. Fish consumption and other covariates were obtained by questionnaire. Multivariate linear regression models were conducted in order to explore the association between mercury exposure and fish consumption, socio-demographic characteristics and prenatal exposure to mercury. The geometric mean was 1.10 µg/g (95%CI: 1.02, 1.19). Nineteen percent of children had mercury concentrations above the equivalent to the Provisional Tolerable Weekly Intake proposed by WHO. Mercury concentration was associated with increasing maternal age, fish consumption and cord blood mercury levels, as well as decreasing parity. Children whose mothers worked had higher mercury levels than those with non working mothers. Swordfish, lean fish and canned fish were the fish categories most associated with hair mercury concentrations. We observed a decreasing trend in mercury concentrations between birth and age four. In conclusion, the children participating in this study had high hair mercury concentrations compared to reported studies on children from other European countries and similar to other countries with high fish consumption. The INMA study design allows the evaluation of the exposure to mercury longitudinally and enables this information to be used for biomonitoring purposes and dietary recommendations. - Highlights: • The geometric mean of hair Hg concentrations was 1.10 µg/g. • 19% of children had Hg concentrations above the RfD proposed by the WHO. • Hair Hg concentrations in children increased as a function of total fish intake. • Swordfish, lean fish and canned fish were the most related to Hg concentrations. • There was a decrease in Hg concentrations from birth to age four.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2014

Environmental cadmium and lead exposures and age-related macular degeneration in U.S. adults: The National Health and Nutrition Examination Survey 2005 to 2008

Age-related macular degeneration (AMD) is a complex disease resulting from the interplay of genetic predisposition and environmental exposures, and has been linked to oxidative stress and inflammatory mechanisms. Lead and cadmium can accumulate in human retinal tissues and may damage the retina through oxidative stress, and may thereby play a role in the development of AMD. We examined associations between blood lead, blood cadmium, and urinary cadmium concentrations and the presence of AMD in 5390 participants aged 40 years and older with blood lead and blood cadmium measures and a subsample of 1548 with urinary cadmium measures in the 2005–2008 National Health and Nutrition Examination Surveys. AMD was identified by grading retinal photographs with a modification of the Wisconsin Age-Related Maculopathy Grading System. The weighted prevalence of AMD was 6.6% (n=426). Controlling for age, gender, race/ethnicity, education and body mass index, adults in the highest blood cadmium quartile had higher odds of AMD compared to the lowest quartile (odds ratio [OR], 1.56; 95% CI, 1.02–2.40), with a significant trend across quartiles (p-trend=0.02). After further adjustment for pack-years of cigarette smoking, estimates were somewhat attenuated (OR, 1.43; 95% CI, 0.91–2.27; p-trend=0.08). Similar associations were found with urinary cadmium. The association between urinary cadmium and AMD was stronger in non-Hispanic whites (NHW) than in non-Hispanic blacks (NHB) (OR, 3.31; 95% CI, 1.37–8.01 for levels above versus below the median among NHW; OR,1.45; 95% CI, 0.40–5.32 for levels above versus below the median among NHB; p-interaction=0.03). We found no association between blood lead levels and AMD. Higher cadmium body burden may increase risk of AMD, particularly among non-Hispanic white individuals; however, additional studies are needed before firm conclusions can be drawn. - Highlights: • We examined the association of cadmium and lead with age-related macular degeneration (AMD) in U.S. adults. • Cadmium in both blood and urine was borderline significantly associated with the risk of AMD. • Blood lead was not associated with the risk of AMD. • The association between urine cadmium and AMD was stronger in whites than in blacks.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Hallmarks of Alzheimer disease are evolving relentlessly in Metropolitan Mexico City infants, children and young adults. APOE4 carriers have higher suicide risk and higher odds of reaching NFT stage V at ≤ 40 years of age

Highlights: • Exposures to fine particulate matter (PM{sub 2.5}) are associated with Alzheimer's disease(AD) risk. • AD starts in the brainstem of children. • AD hallmarks are present in 202/203 CDMX residents ages 11 months to 40 years. • APOE4 carriers have 4.92 times higher suicide odds versus APOE3. • Highly oxidative, ubiquitous nanoparticles are a plausible path into AD pathogenesis. Exposures to fine particulate matter (PM{sub 2.5}) and ozone (O{sub 3}) above USEPA standards are associated with Alzheimer's disease (AD) risk. Metropolitan Mexico City (MMC) residents have life time exposures to PM{sub 2.5} and O{sub 3} above USEPA standards. We investigated AD intra and extracellular protein aggregates and ultrastructural neurovascular pathology in 203 MMC residents age 25.36 ± 9.23 y. Immunohistochemical methods were used to identify AT8 hyperphosphorilated tau (Htau) and 4G8 (amyloid β 17-24). Primary outcomes: staging of Htau and amyloid, per decade and cumulative PM{sub 2.5} (CPM{sub 2.5}) above standard. Apolipoprotein E allele 4 (APOE4), age and cause of death were secondary outcomes. Subcortical pretangle stage b was identified in an 11month old baby. Cortical tau pre-tangles, neurofibrillary tangles (NFT) Stages I-II, amyloid phases 1–2, Htau in substantia nigrae, auditory, oculomotor, trigeminal and autonomic systems were identified by the 2nd decade. Progression to NFT stages III-V was present in 24.8% of 30–40 y old subjects. APOE4 carriers have 4.92 times higher suicide odds (p = 0.0006), and 23.6 times higher odds of NFT V (p < 0.0001) v APOE4 non-carriers having similar CPM{sub 2.5} exposure and age. Age (p = 0.0062) and CPM{sub 2.5} (p = 0.0178) were significant for developing NFT V. Combustion-derived nanoparticles were associated with early and progressive damage to the neurovascular unit. Alzheimer's disease starting in the brainstem of young children and affecting 99.5% of young urbanites is a serious health crisis. Air pollution control should be prioritised. Childhood relentless Htau makes a fundamental target for neuroprotective interventions and the first two decades are critical. We recommend the concept of preclinical AD be revised and emphasize the need to define paediatric environmental, nutritional, metabolic and genetic risk factor interactions of paramount importance to prevent AD. AD evolving from childhood is threating the wellbeing of our children and future generations.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Formation, cooling history and age of impact events on the IIE iron parent body: Evidence from the Miles meteorite

Most iron meteorites formed in planetary cores during differentiation, but the IIE iron meteorites have chemical and physical features that are inconsistent with this origin. By combining mineral chemistry, mineral modes and three-dimensional petrography, we reconstruct the bulk chemistry of the felsic silicate-bearing Miles IIE iron meteorite and demonstrate that the silicate inclusion compositions are similar to partial melts produced experimentally from an H chondrite composition. We use the reconstructed bulk composition, mineralogy and thermodynamic modelling to show that melting above ~ 1200°C under reducing conditions formed metal (Fe-Ni alloy) and felsic silicate partial melts. Upon cooling, the melts crystallized Mg-rich pyroxenes, Na- and K-rich feldspars, and tridymite. Importantly, this mechanism enriches cosmochemically volatile elements (i.e., those with a 50% condensation temperature of ~430–830°C, like Na and K) to the level found in the felsic silicate inclusions. The presence of crystallographically disordered srilankite (only stable above 1160°C) and an absence of Widmanstätten texture require both high peak temperatures and rapid cooling, which cannot be explained by core formation. Instead, they point to small melt volumes, a transient heat pulse, and small thermal mass, and imply efficient physical segregation of silicate and metallic melts through buoyancy separation followed by rapid cooling that arrested the separation of metal and silicate liquid phases. In situ 207 Pb/ 206 Pb age of 4542.3 ± 4.0 Ma in Zr-oxide and phosphate minerals dates the melting event that formed the silicate inclusions. This age aligns with the earliest ages found in other IIE iron meteorite silicates and requires a heating event ~25 million years after the solar system formed. We found 39 Ar/ 40 Ar ages of 3495 ± 52 Ma (low-T) and 4303 ± 7 Ma (high-T) in a K-feldspar grain, with the 3495 Ma age aligning with later thermal events recorded in other IIE iron meteorites. Dating reveals the complex petrogenetic and thermal history of Miles and the IIE iron meteorites. This is the first IIE iron meteorite found to record evidence of heating at 4.5 and 3.5 Ga likely from impact events. We propose that high-velocity impact(s) into an iron-rich, porous chondritic parent body at ~4.54 Ga produced immiscible metal and silicate melts that cooled rapidly and trapped low density silicate inclusions within high density metal. Other IIE irons that formed at lower peak temperatures (900–1000°C) contain chondritic silicate inclusions and relict chondrules, supporting this conceptual model. In conclusion, this petrogenesis is consistent with thermodynamic modelling, experimental data and the wide range of peak temperatures and cooling rates observed in the IIE iron meteorites.

58 GEOSCIENCES↗
DOE OSTI2013

A Reanalysis of Curvature in the Dose Response for Cancer and Modifications by Age at Exposure Following Radiation Therapy for Benign Disease

Purpose: To assess the shape of the dose response for various cancer endpoints and modifiers by age and time. Methods and Materials: Reanalysis of the US peptic ulcer data testing for heterogeneity of radiogenic risk by cancer endpoint (stomach, pancreas, lung, leukemia, all other). Results: There are statistically significant (P<.05) excess risks for all cancer and for lung cancer and borderline statistically significant risks for stomach cancer (P=.07), and leukemia (P=.06), with excess relative risks Gy{sup -1} of 0.024 (95% confidence interval [CI] 0.011, 0.039), 0.559 (95% CI 0.221, 1.021), 0.042 (95% CI -0.002, 0.119), and 1.087 (95% CI -0.018, 4.925), respectively. There is statistically significant (P=.007) excess risk of pancreatic cancer when adjusted for dose-response curvature. General downward curvature is apparent in the dose response, statistically significant (P<.05) for all cancers, pancreatic cancer, and all other cancers (ie, other than stomach, pancreas, lung, leukemia). There are indications of reduction in relative risk with increasing age at exposure (for all cancers, pancreatic cancer), but no evidence for quadratic variations in relative risk with age at exposure. If a linear-exponential dose response is used, there is no significant heterogeneity in the dose response among the 5 endpoints considered or in the speed of variation of relative risk with age at exposure. The risks are generally consistent with those observed in the Japanese atomic bomb survivors and in groups of nuclear workers. Conclusions: There are excess risks for various malignancies in this data set. Generally there is a marked downward curvature in the dose response and significant reduction in relative risk with increasing age at exposure. The consistency of risks with those observed in the Japanese atomic bomb survivors and in groups of nuclear workers implies that there may be little sparing effect of fractionation of dose or low-dose-rate exposure.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2020

Impact of zero valent iron aging on reductive removal of technetium-99

Zero valent iron (ZVI) is a promising material for reductive removal of technetium from industrial waste streams. An example application of this method could be to treatment of low activity aqueous waste that is currently stored in tanks at the Hanford site. However, there is still a lack of understanding of the useful lifetime of ZVI for treatment and the changes in reductive removal of Tc over time. In this research, we studied the reductive removal of Tc from aqueous solutions by ZVI aged with up to 30 days by contact with 0.08 M NaCl solutions. These results show that ZVI could be used to remove Tc(VII) from aqueous solutions by its reduction to the less soluble and relatively immobile Tc(IV) with greater than 99% removal in three hours. Still, greater than 90% of Tc is removed with ZVI aging up to one week. However, after 10 days of aging of zero valent iron, a significant decrease in removal of Tc occurs (55% removal at three hours) followed by negligible removal after aging for two weeks or more which is consistent with formation of iron oxides on the surface. Further, these results correlate with XRD and FTIR analysis showing an increase in magnetite followed by maghemite and goethite with aging time.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Raman signatures from age-dating PuO 2 since last calcination

The self-irradiation of PuO 2 has been shown to affect the attributes of fifteen vibrational bands in the Raman spectrum. The vibrational bands correspond to the Raman allowed vibrational mode T 2g , overtones, defects, and bands from electronic origin. Defects in the crystal lattice from low-calcination temperature and alpha decay origins are responsible for the changes in the band attributes (band position, full-width half maximum (FWHM), intensity). Crystal lattice defects are also responsible for the growth of the defect bands. The temporal behavior of the vibrational bands can be used to estimate the age of the material since last calcination. Laser annealing was used to reset the material to full crystallinity prior to the aging study. 240 PuO 2 , with an alpha decay rate of 3.67 greater than the decay rate of 239 PuO 2 , was primarily used to assess the alpha decay-induced damage within 3 years. The aging study focused on the time-dependent properties of the T 2g band and the growth of defect bands. The FWHM of the T 2g band and the ratio of the areas of the defect bands/T 2g band were measured through a time period in excess of 3 years. The data from this study were found very close to the data describing the temporal evolution of the lattice constant measured with the X-ray diffraction (XRD) technique. The local physical properties of the material measured with Raman spectroscopy and the lattice parameter constant measured with XRD indicates a strong correlation between the two techniques. Although both techniques provide similar age-dating information, in contrast to the few milligram quantities required for XRD, Raman spectroscopy requires a 10 µm diameter PuO 2 particle to provide an estimate of the material age since last calcination.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2014

Characterization of rhenium compounds obtained by electrochemical synthesis after aging process

The proper identification of the molecular nature of the aged rhenium compound obtained by means of electrodeposition from an alkaline aqueous electrolyte was determined. Chemical, structural and vibrational experimental characterization of the aged Re compound showed agreement with quantum-computations, thereby allowing the unambiguous identification of the Re compound as H(ReO{sub 4})H{sub 2}O. - Graphical abstract: Rhenium oxides were electrodeposited on a copper surface and after environmental aging was formed the H(ReO{sub 4})H{sub 2}O compound. The characterization of the synthesized material was made through the comparison of experimental evidence with quantum mechanical computations carried out by means of density functional theory (DFT). - Highlights: • Aged rhenium compound obtained by means of electrodeposition was studied. • The study was made by combining experimental and DFT-computational information. • The aged electrodeposited material is consistent with the H(ReO{sub 4})H{sub 2}O compound.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Effect of as-cast microstructure heterogeneity on aging behavior of a high-pressure die-cast A380 alloy

Highlights: • The surface layer hardened much faster than the central region during age. • More quantity of finer precipitates was found in the surface layer during age. • The surface layer had a lower activation energy of precipitation. • Si promoted the precipitation via inducing dislocations in matrix. - Abstract: Microstructure and hardness evolution of a vacuum-assistant die-cast A380 alloy during heat treatment were investigated. Both surface layer and central region of the casting component were analyzed in die-cast state, solutionized state and artificial age state. During the artificial age, the surface layer hardened more significantly than the central region due to faster precipitation and more refined hardening phases in the surface layer. Detailed analysis on the macro-segregation, microstructure morphology and grain size revealed that the different aging behaviors exhibiting in the surface and the central region were mainly attributed to a combining effect of the enrichment of Si and Cu at the surface layer, the fully-divorced morphology of eutectic in die-cast microstructure, and the presence of the externally solidified crystals at the central region. The presence of the Si particles, which exhibited quite different thermal expansion properties, changed the density and the distribution of the dislocations in the α-Al matrix, and consequently changed the precipitation of the hardening phases.

36 MATERIALS SCIENCE↗
DOE OSTI2019

High-energy synchrotron radiation X-ray diffraction measurements during in situ aging of a NiTi-15 at. % Hf high temperature shape memory alloy

NiTiHf high temperature shape memory alloys (HTSMAs) have begun to show considerable progress in their ability to be manufactured and are now on the cusp of becoming viable alloys for use in the aerospace industry, mainly as actuation devices. By aging the alloys at intermediate temperatures between 450 and up to 700 °C, Ni-rich NiTiHf HTSMAs form the H-phase, a Ni-rich nanoscale precipitate which can be used to strengthen the alloy and improve the shape memory response; however, precipitate phase evolution and growth has not yet been studied in-situ nor have the effects of previous thermo-mechanical processing on their formation. In this study, H-phase precipitate formation is observed experimentally in situ during aging of a Ni-rich NiTiHf alloy using high energy synchrotron radiation X-ray diffraction (SR-XRD) measurements. The effects of prior thermo-mechanical treatments, i.e. hot and cold rolling, on its formation rate and coarsening rate are compared. It is shown that growth of the H-phase can be observed in situ using SR-XRD and the H-phase formation rate seems to exhibit linear growth when aging at 550 °C, while increasing the temperature to 650 °C shows a logarithmic trend that plateaus after approximately 1 h of aging. Other properties such as incubation time, austenite lattice strains, texture evolution, and overall comparison between hot and cold rolling are discussed. New potential peak age conditions are suggested based on the diffraction data and evaluated using three-point bending and TEM imaging.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Aging mechanisms in RTV polysiloxane foams

The long-term use of polysiloxane foams requires a good understanding of the diverse factors that may influence their performance. The aim of the present work was to understand the interplay between in-service environments and reactive species that reside in the foams. Two foams (SX358 and S5370) were thermally aged under compressive strain to gauge the onset of compression set, an indicator of degradation. In this study, experiments were performed by either aging the foams in open air containers or in high humidity environments. Our results indicated that foams aged in open air environments exhibited less compression set than when aged in presence of moisture. These results were analyzed in terms of post-curing reactions, hydrolysis and rearrangement of the network, which are promoted by active residues that are left in the foam from the curing process. In particular, the residues from tin octoate, the catalyst used in the cure of the foams, were identified and their role in promoting aging was determined. Reactions were either catalyzed by tin(II) species or by a combination of trace amounts of water and octanoic acid, a product of the hydrolysis of tin octoate. More precisely, this work demonstrated that reactive residues promote chemical changes in the polymer, which resulted in compression set. On the other hand, the oxidized residues of the tin octoate show no catalytic activity towards promoting condensation reactions between silanol groups. In conclusion, our work established that, depending on service conditions, certain residues are more harmful to the foam's lifetime than others.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Direct measurement of energy loss due to aging effects in the condensed phase explosive PBX 9404

The explosive performance of PBX 9404, a condensed phase explosive with HMX and nitrocellulose reactive ingredients, was evaluated using the detonation cylinder expansion test after it had been naturally aged for over 46 years. Nitrocellulose is known to chemically degrade with age, but the corresponding effect on explosive performance is currently unknown. Two new cylinder tests were fielded with the oldest known PBX 9404 explosive (>46 years) and the data was compared with prior PBX 9404 cylinder test data. A method for comparing wall motion data collected by streak camera and laser interferometry diagnostics was also introduced. Analysis of the cylinder motion indicated that the aged explosive exhibits decreased performance, which varied with cylinder expansion radius and product specific volume. This energy decrement was found to be 0.8% of the total initial explosive energy per decade of age at a product volume of 7.0 cc/g. In conclusion, the measured energy decrement in explosives older than 37 years exceeds the chemical energy content of nitrocellulose, indicating that nitrocellulose decomposition radicals are likely degrading the normally stable HMX molecules during the aging process.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Zuotai and HgS differ from HgCl{sub 2} and methyl mercury in Hg accumulation and toxicity in weanling and aged rats

Mercury sulfides are used in Ayurvedic medicines, Tibetan medicines, and Chinese medicines for thousands of years and are still used today. Cinnabar (α-HgS) and metacinnabar (β-HgS) are different from mercury chloride (HgCl{sub 2}) and methylmercury (MeHg) in their disposition and toxicity. Whether such scenario applies to weanling and aged animals is not known. To address this question, weanling (21 d) and aged (450 d) rats were orally given Zuotai (54% β-HgS, 30 mg/kg), HgS (α-HgS, 30 mg/kg), HgCl{sub 2} (34.6 mg/kg), or MeHg (MeHgCl, 3.2 mg/kg) for 7 days. Accumulation of Hg in kidney and liver, and the toxicity-sensitive gene expressions were examined. Animal body weight gain was decreased by HgCl{sub 2} and to a lesser extent by MeHg, but unaltered after Zuotai and HgS. HgCl{sub 2} and MeHg produced dramatic tissue Hg accumulation, increased kidney (kim-1 and Ngal) and liver (Ho-1) injury-sensitive gene expressions, but such changes are absent or mild after Zuotai and HgS. Aged rats were more susceptible than weanling rats to Hg toxicity. To examine roles of transporters in Hg accumulation, transporter gene expressions were examined. The expression of renal uptake transporters Oat1, Oct2, and Oatp4c1 and hepatic Oatp2 was decreased, while the expression of renal efflux transporter Mrp2, Mrp4 and Mdr1b was increased following HgCl{sub 2} and MeHg, but unaffected by Zuotai and HgS. Thus, Zuotai and HgS differ from HgCl{sub 2} and MeHg in producing tissue Hg accumulation and toxicity, and aged rats are more susceptible than weanling rats. Transporter expression could be adaptive means to reduce tissue Hg burden. - Highlights: • Aged rats are more susceptible to HgCl{sub 2} and MeHg toxicity than weanling rats. • Zuotai and HgS differ from HgCl{sub 2} and MeHg in producing toxicity. • Zuotai and HgS differ from HgCl{sub 2} and MeHg in much less tissue Hg accumulation. • Renal transporters are altered by HgCl{sub 2} and MeHg, but unaffected by Zuotai and HgS • Liver transporters are less affected than kidney transporters by HgCl{sub 2} and MeHg.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2019

Production of Secondary Organic Aerosol During Aging of Biomass Burning Smoke From Fresh Fuels and Its Relationship to VOC Precursors

After smoke from burning biomass is emitted into the atmosphere, chemical and physical processes change the composition and amount of organic aerosol present in the aged, diluted plume. During the fourth Fire Lab at Missoula Experiment, we performed smog-chamber experiments to investigate formation of secondary organic aerosol (SOA) and multiphase oxidation of primary organic aerosol (POA). We simulated atmospheric aging of diluted smoke from a variety of biomass fuels while measuring particle composition using high-resolution aerosol mass spectrometry. We quantified SOA formation using a tracer ion for low-volatility POA as a reference standard (akin to a naturally occurring internal standard). We report these smoke aging experiments revealed variable organic aerosol (OA) enhancements, even for smoke from similar fuels and aging mechanisms. This variable OA enhancement correlated well with measured differences in the amounts of emitted volatile organic compounds (VOCs) that could subsequently be oxidized to form SOA. For some aging experiments, we were able to predict the SOA production to within a factor of 2 using a fuel-specific VOC emission inventory that was scaled by burn-specific toluene measurements. For fires of coniferous fuels that were dominated by needle burning, volatile biogenic compounds were the dominant precursor class. For wiregrass fires, furans were the dominant SOA precursors. We used a POA tracer ion to calculate the amount of mass lost due to gas-phase oxidation and subsequent volatilization of semivolatile POA. Less than 5% of the POA mass was lost via multiphase oxidation-driven evaporation during up to 2 hr of equivalent atmospheric oxidation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗