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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Application of Microwave Plasma Atomic Emission Spectrometry and Hydride Generation for Determination of Arsenic and Selenium in Mineral Water

The ability to determine arsenic and selenium at their maximum acceptable concentrations (MAC) in drinking water via microwave plasma atomic emission spectrometry (MP-AES) and hydride generation is shown in this study. The determination of these elements is possible even in samples with a high degree of mineralization (up to 12 g/L). To provide the required sensitivity of determination of both elements, certain operating modes of the spray chamber for hydride generation are chosen. The conditions for the determination of these elements in mineral and medical-table waters are proposed.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Plasma process optimization for N-type doping applications

Plasma doping (PLAD) has been adopted across the implant technology space and into high volume production for both conventional DRAM and NAND doping applications. PLAD has established itself as an alternative to traditional ion implantation by beamline implantation. The push for high doping concentration, shallow doping depth, and conformal doping capability expand the need for a PLAD solution to meet such requirements. The unique doping profile and doping characteristics at high dose rates allow for PLAD to deliver a high throughput, differentiated solution to meet the demand of evolving transistor technology. In the PLAD process, ions are accelerated to the wafer as with a negative wafer bias applied to the wafer. Competing mechanisms, such as deposition, sputtering, and etching inherent in plasma doping require unique control and process optimization. In this work, we look at the distinctive process tool control and characterization features which enable an optimized doping process using n-type (PH{sub 3} or AsH{sub 3}) chemistries. The data in this paper will draw the relationship between process optimization through plasma chemistry study to the wafer level result.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Plasma chemistry study of PLAD processes

Plasma doping (PLAD) shows very different impurity profiles compared to the conventional beam-line-based ion implantations due to its non-mass separation property and plasma environment. There is no simulation for PLAD process so far due to a lack of a dopant profile model. Several factors determine impurity profiles of PLAD process. The most significant factors are: plasma chemistry and deposition/etching characteristics of multi-ion species plasmas. In this paper, we present plasma chemistry and deposition/etching characteristics of PLAD processes versus co-gas dilutions. Four dopant plasmas including B{sub 2}H{sub 6}, BF{sub 3}, AsH{sub 3}, and PH{sub 3}, and two non-dopant plasmas including CH{sub 4} and GeH{sub 4} are studied and demonstrated.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Growth of antiphase-domain-free GaP on Si substrates by metalorganic chemical vapor deposition using an in situ AsH{sub 3} surface preparation

Antiphase-domain (APD) free GaP films were grown on Si(100) substrates prepared by annealing under dilute AsH{sub 3} in situ in an MOCVD reactor. LEED and AES surface analysis of Si(100) surfaces prepared by this treatment show that AsH{sub 3} etching quickly removes O and C contaminants at a relatively low temperature (690–740 °C), and creates a single-domain “A-type” As/Si surface reconstruction. The resulting GaP epilayers grown at the same temperature are APD-free, and could thereby serve as templates for direct growth of III-V semiconductors on Si. This single chamber process has a low thermal budget, and can enable heteroepitaxial integration of III-Vs and Si at an industrial scale.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Low-level arsenic exposure via drinking water consumption and female fecundity - A preliminary investigation

High level arsenic exposure is associated with reproductive toxicity in experimental and observational studies; however, few data exist to assess risks at low levels. Even less data are available to evaluate the impact of low level arsenic exposure on human fecundity. Our aim in this pilot study was a preliminary evaluation of associations between low level drinking water arsenic contamination and female fecundity. This retrospective study was conducted among women previously recruited to a hospital-based case-control study of spontaneous pregnancy loss in Timiá¹£ County, Romania. Women (n=94) with planned pregnancies of 5–20 weeks gestation completed a comprehensive physician-administered study questionnaire and reported the number of menstrual cycles attempting to conceive as the time to pregnancy (TTP). Drinking water samples were collected from residential drinking water sources and we determined arsenic levels using hydride generation-atomic absorption spectrometry (HG-AAS). Multivariable Cox-proportional hazards regression with Efron approximation was employed to evaluate TTP as a function of drinking water arsenic concentrations among planned pregnancies, adjusted for covariates. There was no main effect for drinking water arsenic exposure, yet the conditional probability for pregnancy was modestly lower among arsenic exposed women with longer TTPs, relative to women with shorter TTPs, and relative to unexposed women. For example, 1 µg/L average drinking water arsenic conferred 5%, 8%, and 10% lower likelihoods for pregnancy in the 6th, 9th, and 12th cycles, respectively (P=0.01). While preliminary, our results suggest that low level arsenic contamination in residential drinking water sources may further impair fecundity among women with longer waiting times; however, this hypothesis requires confirmation by a future, more definitive study. - Highlights: • We assessed low level drinking water arsenic as a predictor of fecundability. • Arsenic did not affect time to pregnancy among women conceiving quickly. • Arsenic increased time to pregnancy among women taking longer to conceive. • Low level drinking water arsenic may adversely impact women with lower fecundity.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2014

A model for arsenic anti-site incorporation in GaAs grown by hydride vapor phase epitaxy

GaAs growth by hydride vapor phase epitaxy (HVPE) has regained interest as a potential route to low cost, high efficiency thin film photovoltaics. In order to attain the highest efficiencies, deep level defect incorporation in these materials must be understood and controlled. The arsenic anti-site defect, As{sub Ga} or EL2, is the predominant deep level defect in HVPE-grown GaAs. In the present study, the relationships between HVPE growth conditions and incorporation of EL2 in GaAs epilayers were determined. Epitaxial n-GaAs layers were grown under a wide range of deposition temperatures (T{sub D}) and gallium chloride partial pressures (P{sub GaCl}), and the EL2 concentration, [EL2], was determined by deep level transient spectroscopy. [EL2] agreed with equilibrium thermodynamic predictions in layers grown under conditions in which the growth rate, R{sub G}, was controlled by conditions near thermodynamic equilibrium. [EL2] fell below equilibrium levels when R{sub G} was controlled by surface kinetic processes, with the disparity increasing as R{sub G} decreased. The surface chemical composition during growth was determined to have a strong influence on EL2 incorporation. Under thermodynamically limited growth conditions, e.g., high T{sub D} and/or low P{sub GaCl}, the surface vacancy concentration was high and the bulk crystal was close to equilibrium with the vapor phase. Under kinetically limited growth conditions, e.g., low T{sub D} and/or high P{sub GaCl}, the surface attained a high GaCl coverage, blocking As adsorption. This competitive adsorption process reduced the growth rate and also limited the amount of arsenic that incorporated as As{sub Ga}. A defect incorporation model which accounted for the surface concentration of arsenic as a function of the growth conditions, was developed. This model was used to identify optimal growth parameters for the growth of thin films for photovoltaics, conditions in which a high growth rate and low [EL2] could be attained.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Arsenic exposure from drinking water is associated with decreased gene expression and increased DNA methylation in peripheral blood

Background: Exposure to inorganic arsenic increases the risk of cancer and non-malignant diseases. Inefficient arsenic metabolism is a marker for susceptibility to arsenic toxicity. Arsenic may alter gene expression, possibly by altering DNA methylation. Objectives: To elucidate the associations between arsenic exposure, gene expression, and DNA methylation in peripheral blood, and the modifying effects of arsenic metabolism. Methods: The study participants, women from the Andes, Argentina, were exposed to arsenic via drinking water. Arsenic exposure was assessed as the sum of arsenic metabolites in urine (U-As), using high performance liquid-chromatography hydride-generation inductively-coupled-plasma-mass-spectrometry, and arsenic metabolism efficiency was assessed by the urinary fractions (%) of the individual metabolites. Genome-wide gene expression (N = 80 women) and DNA methylation (N = 93; 80 overlapping with gene expression) in peripheral blood were measured using Illumina DirectHyb HumanHT-12 v4.0 and Infinium Human-Methylation 450K BeadChip, respectively. Results: U-As concentrations, ranging 10–1251 μg/L, was associated with decreased gene expression: 64% of the top 1000 differentially expressed genes were down-regulated with increasing U-As. U-As was also associated with hypermethylation: 87% of the top 1000 CpGs were hypermethylated with increasing U-As. The expression of six genes and six individual CpG sites were significantly associated with increased U-As concentration. Pathway analyses revealed enrichment of genes related to cell death and cancer. The pathways differed somewhat depending on arsenic metabolism efficiency. We found no overlap between arsenic-related gene expression and DNA methylation for individual genes. Conclusions: Increased arsenic exposure was associated with lower gene expression and hypermethylation in peripheral blood, but with no evident overlap. - Highlights: • Women exposed to inorganic arsenic were studied for molecular responses in blood. • Arsenic is associated with decreased gene expression and increased DNA methylation. • Arsenic related pathways differed to some extent due to arsenic metabolism efficiency.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2013

Urinary arsenic profiles and the risks of cancer mortality: A population-based 20-year follow-up study in arseniasis-endemic areas in Taiwan

Few studies investigated the association between chronic arsenic exposure and the mortality of cancers by estimating individual urinary arsenic methylation profiles. Therefore, we compared with the general population in Taiwan to calculate the standardized mortality ratio (SMR) in arseniasis-endemic area of Taiwan from 1996 to 2010 and evaluated the dose-response relationships between environmental arsenic exposure indices or urinary arsenic profiles and the mortality of cause-specific cancer. A cohort of 1563 residents was conducted and collected their urine sample and information regarding arsenic exposure from a questionnaire. All-cause death was identified using the National Death Registry of Taiwan. Urinary arsenic profiles were measured using high performance liquid chromatography–hydride generator–atomic absorption spectrometry. We used Cox proportional hazard models to evaluate the mortality risks. In results, 193 all-site cancer deaths, and 29, 71, 43 deaths respectively for liver, lung and bladder cancers were ascertained. The SMRs were significantly high in arseniasis-endemic areas for liver, lung, and bladder cancers. People with high urinary InAs% or low DMA% or low secondary methylation index (SMI) were the most likely to suffer bladder cancer after adjusting other risk factors. Even stopping exposure to arsenic from the artesian well water, the mortality rates of the residents were higher than general population. Finally, urinary InAs%, DMA% and SMI could be the potential biomarkers to predict the mortality risk of bladder cancer. -- Highlights: ► The SMRs were significantly high in arseniasis-endemic areas for liver, lung, and bladder cancers. ► People with high urinary InAs% were the most likely to suffer bladder cancer. ► People with low DMA% or low SMI were the most likely to suffer bladder cancer.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2013

The effect of cigarette smoke and arsenic exposure on urothelial carcinoma risk is modified by glutathione S-transferase M1 gene null genotype

Inter-individual variation in the metabolism of xenobiotics, caused by factors such as cigarette smoking or inorganic arsenic exposure, is hypothesized to be a susceptibility factor for urothelial carcinoma (UC). Therefore, our study aimed to evaluate the role of gene–environment interaction in the carcinogenesis of UC. A hospital-based case–control study was conducted. Urinary arsenic profiles were measured using high-performance liquid chromatography–hydride generator-atomic absorption spectrometry. Genotyping was performed using a polymerase chain reaction-restriction fragment length polymorphism technique. Information about cigarette smoking exposure was acquired from a lifestyle questionnaire. Multivariate logistic regression was applied to estimate the UC risk associated with certain risk factors. We found that UC patients had higher urinary levels of total arsenic, higher percentages of inorganic arsenic (InAs%) and monomethylarsonic acid (MMA%) and lower percentages of dimethylarsinic acid (DMA%) compared to controls. Subjects carrying the GSTM1 null genotype had significantly increased UC risk. However, no association was observed between gene polymorphisms of CYP1A1, EPHX1, SULT1A1 and GSTT1 and UC risk after adjustment for age and sex. Significant gene–environment interactions among urinary arsenic profile, cigarette smoking, and GSTM1 wild/null polymorphism and UC risk were observed after adjustment for potential risk factors. Overall, gene–environment interactions simultaneously played an important role in UC carcinogenesis. In the future, large-scale studies should be conducted using tag-SNPs of xenobiotic-metabolism-related enzymes for gene determination. -- Highlights: ► Subjects with GSTM1 null genotype had significantly increased UC risk. ► UC patients had poor arsenic metabolic ability compared to controls. ► GSTM1 null genotype may modify arsenic related UC risk.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

XRCC1 Arg194Trp and Arg399Gln polymorphisms and arsenic methylation capacity are associated with urothelial carcinoma

The association between DNA repair gene polymorphisms and bladder cancer has been widely studied. However, few studies have examined the correlation between urothelial carcinoma (UC) and arsenic or its metabolites. The aim of this study was to examine the association between polymorphisms of the DNA repair genes, XRCC1 Arg194Trp, XRCC1 Arg399Gln, XRCC3 Thr241Met, and XPD Lys751Gln, with urinary arsenic profiles and UC. To this end, we conducted a hospital-based case–control study with 324 UC patients and 647 age- and gender-matched non-cancer controls. Genomic DNA was used to examine the genotype of XRCC1 Arg194Trp, XRCC1 Arg399Gln, XRCC3 Thr241Met, and XPD Lys751Gln by PCR-restriction fragment length polymorphism analysis (PCR-RFLP). Urinary arsenic profiles were measured by high performance liquid chromatography (HPLC) linked with hydride generator and atomic absorption spectrometry. The XRCC1 399 Gln/Gln and 194 Arg/Trp and Trp/Trp genotypes were significantly related to UC, and the odds ratio (OR) and 95% confidence interval (95%CI) were 1.68 (1.03–2.75) and 0.66 (0.48–0.90), respectively. Participants with higher total urinary arsenic levels, a higher percentage of inorganic arsenic (InAs%) and a lower percentage of dimethylarsinic acid (DMA%) had a higher OR of UC. Participants carrying XRCC1 risk diplotypes G-C/G-C, A-C/A-C, and A-T/G-T, and who had higher total arsenic levels, higher InAs%, or lower DMA% compared to those with other XRCC1 diplotypes had a higher OR of UC. Our results suggest that the XRCC1 399 Gln/Gln and 194 Arg/Arg DNA repair genes play an important role in poor arsenic methylation capacity, thereby increasing the risk of UC in non-obvious arsenic exposure areas. - Highlights: • The XRCC1 399Gln/Gln genotype was significantly associated with increased OR of UC. • The XRCC1 194 Arg/Trp and Trp/Trp genotype had a significantly decreased OR of UC. • Combined effect of the XRCC1 genotypes and poor arsenic methylation capacity on UC.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

Renin–angiotensin–aldosterone system related gene polymorphisms and urinary total arsenic is related to chronic kidney disease

A recent study demonstrated that an increased risk of chronic kidney disease (CKD) was associated with high urinary total arsenic levels. However, whether genomic instability is related to CKD remains unclear. An association between CKD and genetic polymorphisms of regulation enzymes of the renin–angiotensin–aldosterone system (RAAS), such as angiotensin-converting enzyme (ACE), angiotensinogen (AGT), angiotensin II type I receptor (AT1R), and aldosterone synthase (CYP11B2) has not been shown. The aim of the present study was to investigate the relationship between arsenic, genetic polymorphisms of RAAS enzymes and CKD. A total of 233 patients and 449 age- and gender-matched controls were recruited from the Taipei Medical University Hospital, Taipei Municipal Wan Fang Hospital and the Shin Kong Wu Ho-Su Memorial Hospital. Concentrations of urinary arsenic were determined by a high-performance liquid chromatography-linked hydride generator, and atomic absorption spectrometry. Polymorphisms of ACE(I/D), AGT(A[− 20]C), (T174M), (M235T), AT1R(A1166C) and CYP11B2(C[− 344]T) were examined by polymerase chain reaction and restriction fragment length polymorphism. Subjects carrying the CYP11B2 TT genotype had a higher odds ratio (OR), 1.39 (0.96–2.01), of CKD; while those with the AGT(A[− 20]C) CC genotype had an inverse OR of CKD (0.20 (0.05–0.81)), and a high-risk genotype was defined as A/A + A/C for AGT(A[− 20C]) and T/T for CYP11B2(C[− 344]T). The trend test showed a higher OR for CKD in patients who had either high urinary total arsenic levels or carried the high-risk genotype, or both, compared to patients with low urinary total arsenic levels, who carried the low-risk genotype, and could also be affected by the hypertension or diabetes status. - Highlights: • AGT(− 20 C) and CYP11B2(− 344 T) genotypes were significantly associated with CKD. • Combined effect of high-risk genotypes and high urinary total arsenic on OR of CKD. • Combined effect on the CKD was modified by the hypertension and diabetes status.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Combined effects of DNA methyltransferase 1 and 3A polymorphisms and urinary total arsenic levels on the risk for clear cell renal cell carcinoma

Our previous study showed that high urinary total arsenic levels were associated with higher odds ratio (OR) for renal cell carcinoma (RCC). Single nucleotide polymorphisms (SNPs) of DNA methyltransferases (DNMTs) might influence DNMT enzyme activity associated with tumorigenesis. In this study, we investigated the association of five SNPs from DNMT1 (rs8101626 and rs2228611), DNMT3A (rs34048824 and rs1550117), and DNMT3B (rs1569686) with the risk of clear cell renal cell carcinoma (ccRCC). We also examined the combined effects of DNMT genotypes and urinary arsenic levels on ccRCC risk. We conducted a hospital-based case-control study, which included 293 subjects with ccRCC and 293 age- and gender-matched controls. The urinary arsenic species were determined by a high performance liquid chromatography-linked hydride generator and atomic absorption spectrometry. Genotypes were investigated using polymerase chain reaction and restriction fragment length polymorphism analyses. We observed that the DNMT1 rs8101626 G/G genotype was significantly associated with reduced odds ratio (OR) of ccRCC [OR = 0.38, 95% confidence interval (CI) 0.14–0.99]. Subjects with concurrent DNMT1 rs8101626 A/A + A/G and DNMT3A rs34048824 T/T + T/C genotypes had significantly higher OR for ccRCC [OR = 2.88, 95% CI 1.44–5.77]. Participants with the high-risk genotype of DNMT1 rs8101626 and DNMT3A rs34048824 with concurrently high urinary total arsenic levels had even higher OR of ccRCC in a dose-response manner. This is the first study to evaluate variant DNMT1 rs8101626 and DNMT3A rs34048824 genotypes that modify the arsenic-related ccRCC risk in a geographic area without significant arsenic exposure in Taiwan. - Highlights: • High urinary total arsenic level or polymorphism of DNMT1 increased the OR of ccRCC. • High risk genotypes of combination of DNMT1 and DNMT3A increased the OR of ccRCC. • A joint effect of urinary total arsenic level and DNMTs genotypes may affect ccRCC.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2013

Polymorphism of inflammatory genes and arsenic methylation capacity are associated with urothelial carcinoma

Chronic exposure to arsenic can generate reactive oxidative species, which can induce certain proinflammatory cytokines such as tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6) and interleukin-8 (IL-8). TNF-α, IL-6 and IL-8 have been shown to be involved in the development and progression of various cancers, including bladder cancer. This study aimed to investigate the joint effect of the polymorphism of TNF-α − 308 G/A, IL-6 − 174 G/C, IL-8 − 251 T/A and urinary arsenic profiles on urothelial carcinoma (UC) risk. This study evaluated 300 pathologically-confirmed cases of UC and 594 cancer-free controls. Urinary arsenic species were detected using high-performance liquid chromatography-linked hydride generator and atomic absorption spectrometry. The polymorphism of TNF-α − 308 G/A, IL-6 − 174 G/C and IL-8 − 251 T/A was determined using polymerase chain reaction-restriction fragment length polymorphism. The joint effects on UC risk were estimated by odds ratios and 95% confidence intervals using unconditional logistic regression. We found that the TNF-α − 308 A/A and IL-8 − 251 T/T polymorphisms were significantly associated with UC. Moreover, significant dose–response joint effect of TNF-α − 308 A/A or IL-8 − 251 T/T genotypes and arsenic methylation indices were seen to affect UC risk. The present results also showed a significant increase in UC risk in subjects with the IL-8 − 251 T/T genotype for each SD increase in urinary total arsenic and MMA%. In contrast, a significant decrease in UC risk was found in subjects who carried the IL-8 − 251 T/T genotype for each SD increase in DMA%. - Highlights: • Joint effect of the TNF-α -308 A/A genotype and urinary total arsenic affected UC. • Joint effect of the IL-8 -251 T/T genotype and urinary total arsenic affected UC. • Urinary total arsenic level, TNF-α -308 A/A and IL-8 -251 T/T genotype affected UC.

60 APPLIED LIFE SCIENCES↗
NASA NTRS1997

Metal hydrides as electrode/catalyst materials for oxygen evolution/reduction in electrochemical devices

An at least ternary metal alloy of the formula, AB.sub.(5-Y)X(.sub.y), is claimed. In this formula, A is selected from the rare earth elements, B is selected from the elements of groups 8, 9, and 10 of the periodic table of the elements, and X includes at least one of the following: antimony, arsenic, and bismuth. Ternary or higher-order substitutions, to the base AB.sub.5 alloys, that form strong kinetic interactions with the predominant metals in the base metal hydride are used to form metal alloys with high structural integrity after multiple cycles of hydrogen sorption.

Bugga, Ratnakumar V.↗
DOE OSTI2017

Relation of polymorphism of arsenic metabolism genes to arsenic methylation capacity and developmental delay in preschool children in Taiwan

Inefficient arsenic methylation capacity has been associated with developmental delay in children. The present study was designed to explore whether polymorphisms and haplotypes of arsenic methyltransferase (AS3MT), glutathione-S-transferase omegas (GSTOs), and purine nucleoside phosphorylase (PNP) affect arsenic methylation capacity and developmental delay. A case-control study was conducted from August 2010 to March 2014. All participants were recruited from the Shin Kong Wu Ho-Su Memorial Teaching Hospital. In total, 179 children with developmental delay and 88 children without delay were recruited. Urinary arsenic species, including arsenite (As{sup III}), arsenate (As{sup V}), monomethylarsonic acid (MMA{sup V}), and dimethylarsinic acid (DMA{sup V}) were measured using a high-performance liquid chromatography-linked hydride generator and atomic absorption spectrometry. The polymorphisms of AS3MT, GSTO, and PNP were performed using the Sequenom MassARRAY platform with iPLEX Gold chemistry. Polymorphisms of AS3MT genes were found to affect susceptibility to developmental delay in children, but GSTO and PNP polymorphisms were not. Participants with AS3MT rs3740392 A/G + G/G genotype, compared with AS3MT rs3740392 A/A genotype, had a significantly lower secondary methylation index. This may result in an increased OR for developmental delay. Participants with the AS3MT high-risk haplotype had a significantly higher OR than those with AS3MT low-risk haplotypes [OR and 95% CI, 1.59 (1.08–2.34)]. This is the first study to show a joint dose-response effect of this AS3MT high-risk haplotype and inefficient arsenic methylation capacity on developmental delay. Our data provide evidence that AS3MT genes are related to developmental delay and may partially influence arsenic methylation capacity. - Highlights: • AS3MT genotypes were found to affect susceptibility to developmental delay. • AS3MT rs3740392 A/G and G/G genotype had a significantly low SMI (DMA/MMA) index. • AS3MT high-risk haplotype was significantly associated with developmental delay.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Effects of realgar on GSH synthesis in the mouse hippocampus: Involvement of system X{sub AG}{sup −}, system X{sub C}{sup −}, MRP-1 and Nrf2

Realgar is a type of mineral drug that contains arsenic and has neurotoxicity. Glutathione (GSH), which is the main antioxidant in the central nervous system, plays a key role in antioxidant defenses and the detoxification of arsenic. However, whether realgar interferes with the synthesis of GSH in the brain and the molecular mechanisms underlying its effects are largely unknown. Here, we used mouse models of exposure to realgar to show that realgar affects the synthesis of GSH in the hippocampus, leading to ultrastructural changes in hippocampal neurons and synapses and deficiencies in cognitive abilities, and that the mechanisms that cause this effect may be associated with alterations in the expression of system X{sub AG}{sup −}, system X{sub C}{sup −}, multidrug resistance-associated protein 1(MRP-1), nuclear factor E2-related factor 2 (Nrf2), γ-glutamylcysteine synthetase (γ-GCS), and the levels of glutamate (Glu) and cysteine (Cys) in the extracellular fluid. These findings provide a theoretical basis for preventing the drug-induced chronic arsenic poisoning in the nervous system that is triggered by realgar. - Highlights: • Realgar can induce neurotoxicity. • Realgar can modulate GSH levels in the hippocampus. • The mechanisms rely on expression changes of system X{sub AG}{sup −}, system X{sub C}{sup −}, MRP-1, Nrf2.

60 APPLIED LIFE SCIENCES↗
NASA NTRS1988

Feasibility studies of the growth of 3-5 compounds of boron by MOCVD

Boron-arsenic and boron-phosphorus films have been grown on Si sapphire and silicon-on-sapphire (SOS) by pyrolyzing Group 3 alkyls of boron, i.e., trimethylborane (TMB) and triethylborane (TEB), in the presence of AsH3 and PH3, respectively, in an H2 atmosphere. No evidence for reaction between the alkyls and the hydrides on mixing at room temperature was found. However, the films were predominantly amorphous. The film growth rate was found to depend on the concentration of alkyl boron compound and was essentially constant when TEB and AsH3 were pyrolyzed over the temperature range 550 C to 900 C. The films were found to contain mainly carbon impurities (the amount varying with growth temperature), some oxygen, and were highly stressed and bowed on Si substrates, with some crazing evident in thin (2 micron) B-P and thick (5 micron) B-As films. The carbon level was generally higher in films grown using TEB as the boron source. Films grown from PH3 and TMB showed a higher carbon content than those grown from AsH3 and TMB. Based on their B/As and B/P ratios, films with nominal compositions B sub12-16 As2 and B sub1.1-1.3 P were grown using TMB as the boron source.

Manasevit, H. M.↗
DOE OSTI2018

Multiple-metal exposure, diet, and oxidative stress in Uruguayan school children

Highlights: • In 6–8 year-old children, we examined associations between urinary concentrations of arsenic, cadmium, and lead, and urinary F{sub 2}–8α isoprostane and 8-hydroxy-2-deoxy-guanosine (8-OHdG). • Even at low-level, each doubling in urinary arsenic concentrations was associated with ~ 10 ng/mL higher 8-OHdG concentratio. • An indicator of mixture of the three metals was associated with higher 8-OHdG concentrations. • We found no effect modification by children's dietary antioxidant intake. Oxidative stress (OS) is an important consequence of exposure to toxic metals but it is unclear to what extent low-level metal exposures contribute to OS in children. We examined the cross-sectional association between urinary concentrations of arsenic (As), cadmium (Cd), and lead (Pb) and urinary markers of OS: F{sub 2}–8α isoprostane and 8-hydroxy-2-deoxy-guanosine (8-OHdG). We also tested effect modification by dietary intakes. Of the 211 children aged 6–8 years living in Montevideo who were eligible for the study because they had at least one OS marker measured via ELISA, 143 were included in a complete-case analysis. Urinary metals were measured with inductively coupled plasma mass spectrometry (ICP-MS: Pb, Cd) and high-performance liquid chromatography online with hydride generation ICP-MS (As-metabolites); concentrations were log{sub 2}-transformed. All urinary markers were adjusted for specific gravity of urine. Two 24-h dietary recalls were conducted to estimate children's dietary intakes, including total fruit and vegetable consumption and vitamin C, zinc and fiber intake. Ordinary least square (OLS) and weighted quantile sum (WQS) regressions were used to estimate the association between metals and each OS marker as outcome. Metal exposure was generally low: median urinary As, Cd, Pb 9.6 μg/L, 0.06 μg/L and 1.9 μg/L, respectively. Median 8-isoprostane concentration was 1.1 and 8-OHdG 39.6 ng/mL. Log{sub 2}-transformed urinary As concentrations were positively associated with 8-OHdG concentrations (10.90 [3.82, 17.97]) in covariate-adjusted OLS models which also took account of exposure to Cd and Pb. In WQS, a mixture index was also associated with higher 8-OHdG (8.71 [1.12, 16.3] for each 25% increase in index value), mostly driven by As exposure. There was little evidence of effect modification by dietary antioxidants. In sum, even at low-level, As exposure is associated with detectable oxidative damage to the DNA.

54 ENVIRONMENTAL SCIENCES↗