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At least 1,009 records · Page 56
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Fungal necromass presents a high potential for Mercury immobilization in soil

Past industrial activities have generated many contaminated lands from which Mercury (Hg) escapes, primarily by volatilization. Current phytomanagement techniques aim to limit Hg dispersion by increasing its stabilization in soil. Although soil fungi represent a source of Hg emission associated with biovolatilization mechanisms, there is limited knowledge about how dead fungal residues (i.e., fungal necromass) interact with soil Hg. This study determined the Hg biosorption potential of fungal necromass and the chemical drivers of passive Hg binding with dead mycelia. Fungal necromass was incubated under field conditions with contrasting chemical properties at a well-characterized Hg phytomanagement experimental site in France. After four months of incubation in soil, fungal residues passively accumulated substantial quantities of Hg in their recalcitrant fractions ranging from 400 to 4500 μg Hg/kg. In addition, infrared spectroscopy revealed that lipid compounds explained the amount of Hg biosorption to fungal necromass. In conclusion, based on these findings, we propose that fungal necromass is likely an important factor in Hg immobilization in soil.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Electronic Structure, Optical Properties, and Photoelectrochemical Activity of Sn-Doped Fe 2 O 3 Thin Films

Hematite (Fe 2 O 3 ) is a well-known oxide semiconductor suitable for photoelectrochemical (PEC) water splitting and industry gas sensing. It is widely known that Sn doping of Fe 2 O 3 can enhance the device performance, yet the underlying mechanism remains elusive. In this work, we determine the relationship between electronic structure, optical properties and PEC activity of Sn doped Fe 2 O 3 by studying highly crystalline, well-controlled thin films prepared by pulsed laser deposition (PLD). We show that Sn doping substantially increases the n-type conductivity of Fe 2 O 3 , and the conduction mechanism is better described by small-polaron hoping (SPH) model. Only 0.2% Sn doping significantly reduce the activation energy barrier for SPH conduction from at least 0.5 eV for undoped Fe 2 O 3 to 0.14 eV for doped ones. A combination of X-ray photoemission, X-ray absorption spectroscopy and DFT calculations reveals the Fermi level gradually shifts toward the conduction band minimum with Sn doping. A localized Fe 2+ like gap state is observed at the top of valence band, accounting for the SPH conduction. Interestingly, in contrast to the literature, we find that only 0.2% Sn doping in Fe 2 O 3 significantly improves the PEC activity, while more Sn decreases it. The improved PEC activity is partially attributed to an increased band bending potential which facilitates the charge separation at space charge region. The reduced activation energy barrier for SPH will facilitate the transport of photo-excited carriers for the enhanced PEC, which is of interest for further carrier dynamics study.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

A standardized quantitative analysis strategy for stable isotope probing metagenomics

ABSTRACT Stable isotope probing (SIP) facilitates culture-independent identification of active microbial populations within complex ecosystems through isotopic enrichment of nucleic acids. Many DNA-SIP studies rely on 16S rRNA gene sequences to identify active taxa, but connecting these sequences to specific bacterial genomes is often challenging. Here, we describe a standardized laboratory and analysis framework to quantify isotopic enrichment on a per-genome basis using shotgun metagenomics instead of 16S rRNA gene sequencing. To develop this framework, we explored various sample processing and analysis approaches using a designed microbiome where the identity of labeled genomes and their level of isotopic enrichment were experimentally controlled. With this ground truth dataset, we empirically assessed the accuracy of different analytical models for identifying active taxa and examined how sequencing depth impacts the detection of isotopically labeled genomes. We also demonstrate that using synthetic DNA internal standards to measure absolute genome abundances in SIP density fractions improves estimates of isotopic enrichment. In addition, our study illustrates the utility of internal standards to reveal anomalies in sample handling that could negatively impact SIP metagenomic analyses if left undetected. Finally, we present SIPmg , an R package to facilitate the estimation of absolute abundances and perform statistical analyses for identifying labeled genomes within SIP metagenomic data. This experimentally validated analysis framework strengthens the foundation of DNA-SIP metagenomics as a tool for accurately measuring the in situ activity of environmental microbial populations and assessing their genomic potential. IMPORTANCE Answering the questions, “who is eating what?” and “who is active?” within complex microbial communities is paramount for our ability to model, predict, and modulate microbiomes for improved human and planetary health. These questions can be pursued using stable isotope probing to track the incorporation of labeled compounds into cellular DNA during microbial growth. However, with traditional stable isotope methods, it is challenging to establish links between an active microorganism’s taxonomic identity and genome composition while providing quantitative estimates of the microorganism’s isotope incorporation rate. Here, we report an experimental and analytical workflow that lays the foundation for improved detection of metabolically active microorganisms and better quantitative estimates of genome-resolved isotope incorporation, which can be used to further refine ecosystem-scale models for carbon and nutrient fluxes within microbiomes.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Artificial Intelligence for Digital Security and Protections

Proper functioning of nuclear power plants relies on a mix of well-regulated human and machine-driven workflows. This regulation supports nuclear safety through a series of processes and many of the tasks that support these processes have a repetitive nature that make artificial intelligence (AI) informed by machine learning (ML) a potential aid in a variety of tasks. AI is being evaluated for activities that include inspections, fuel processing, monitoring, and other activities. The introduction of any new technology presents a potential new attack vector. In the case of AI/ML, there are many attacks that have already been discovered and over time the attacks can be expected to follow the growth pattern observed in cyber security. While future planning is necessary, current efforts need to be established now to predict the threat emergence over the next year 10 years and mitigate potential threats. Based on these observations, AI/ML will need to become trustworthy, which corresponds to techniques and procedures that emphasize AI explainability along with resilience techniques to data, algorithms, models, and systems. This kind of system robustness is the foundation for defenses against AI/ML-specific attacks. Attempting to look forward and take a broad view of capabilities provides input to research roadmaps and the ability to distill vulnerabilities into specific use cases may provide greater assistance in understanding the technology benefits while introducing new risks. The impact of current and future AI in three areas—capabilities, challenges, and recovery strategies—represents an initial attempt at balancing both.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
DOE OSTI2020

Glove-based sensors for multimodal monitoring of natural sweat

Sweat sensors targeting exercise or chemically induced sweat have shown promise for noninvasive health monitoring. Natural thermoregulatory sweat is an attractive alternative as it can be accessed during routine and sedentary activity without impeding user lifestyles and potentially preserves correlations between sweat and blood biomarkers. We present simple glove-based sensors to accumulate natural sweat with minimal evaporation, capitalizing on high sweat gland densities to collect hundreds of microliters in just 30 min without active sweat stimulation. Sensing electrodes are patterned on nitrile gloves and finger cots for in situ detection of diverse biomarkers, including electrolytes and xenobiotics, and multiple gloves or cots are worn in sequence to track overarching analyte dynamics. Direct integration of sensors into gloves represents a simple and low-overhead scheme for natural sweat analysis, enabling sweat-based physiological monitoring to become practical and routine without requiring highly complex or miniaturized components for analyte collection and signal transduction.

42 ENGINEERING↗
NASA NTRS2013

Overview of the LADEE Ultraviolet-visible Spectrometer: Design, Performance and Planned Operations

The Lunar Atmosphere and Dust Environment Explorer (LADEE) is an orbital lunar science mission currently under development to address the goals of the 2003 National Research Council decadal survey, the Lunar Exploration Analysis Group Roadmap, and the "Scientific Context for Exploration of the Moon" (SCEM) report, and has been recommended for execution by the 2011 Planetary Missions Decadal Survey. The mission s focus is to study the pristine state of the lunar atmosphere and dust environment prior to possible lunar exploration activities by countries, including the United States, China, India, and Japan, among others. Activity on the lunar surface has the potential of altering the tenuous lunar atmosphere, but changing the type and concentration of gases in the atmosphere. Before these activities occur it is important to make measurements of the current lunar atmosphere in its unmodified state. LADEE will determine the composition of the lunar atmosphere and investigate the processes that control its distribution and variability, including sources, sinks, and surface interactions. It will monitor variations in known gases, such as sodium, potassium, argon and helium, and will search for other, as-yet-undetected gases of both lunar and extra-lunar origin. LADEE will also determine whether dust is present in the lunar exosphere, and reveal the processes that contribute to its sources and variability. Launch is planned for August, 2013.

Colaprete, A.↗
DOE OSTI2025

Convective potential and fuel availability complement near-surface weather in regulating global wildfire activity

Wildfires are favored by hot, dry, windy, rainless conditions—this knowledge about fire weather informs both short-term forecast and long-term prediction of wildfire activity. Yet, wildfires rely on the availability of ignition and fuel, which are underrepresented in fire forecast and prediction practices. By analyzing satellite measurements and atmospheric reanalysis, here we show that near-surface weather only partially captures wildfire occurrence and intensity across the daily to seasonal timescales. Beyond near-surface weather, convection and fuel abundance play a complementary role in regulating burning processes. Specifically, enhanced atmospheric convection is identified for over 40% of the low-human-impact regions and 61% of global burnable areas during wildfire ignition and spreading periods. Meanwhile, 56% of shrublands and 54% of grasslands see higher fuel load with actual occurrence of fire. Our results highlight the role of convection and fuel in wildfire forecast, prompting a revisit of wildfire prediction under intertwined atmospheric and terrestrial changes.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1991

Sand and dust issues for the MESUR mission

The presence of particles in the Martian atmosphere increases the rate of erosion of the heat shield during the entry phase of the MESUR mission. Preliminary analysis has shown that under certain conditions particles will penetrate the bow shock of the entry vehicle, impact and erode the heat shield, above the anticipated rate from the ablation process. Knowledge of the distribution, sizes, and composition of particles suspended in the atmosphere will permit the estimation of the heat shield recession both for a nominal Mars atmosphere and in dust storm conditions. On the surface of Mars, sand and dust can effect the operations and design of the science instruments (i.e., imaging) and lander subsystems (i.e., solar arrays). Distribution and deposition of sand and dust on the planet's surface will dictate the feasibility of using solar arrays as a power source for the lander. Furthermore, the potential abrasive nature of blowing particles must be understood in order to properly select suitable materials for lander structure and any components exposed to the environment. The selection of lander material may also be dictated by corrosive and chemically active properties of particles at a potential landing site. Some key interests concerning sand and dust on the surface and in the atmosphere are summarized in a number of questions that are included.

Wercinski, P. F.↗
DOE OSTI2022

Novel small molecule FGF 23 inhibitors increase serum phosphate and improve skeletal abnormalities in Hyp mice

We report that excess fibroblast growth factor 23 (FGF23) causes hereditary hypophosphatemic rickets, such as X-linked hypophosphatemia (XLH) and tumor induced osteomalacia (TIO). A small molecule that specifically binds to FGF23 to prevent activation of the FGFR/a-Klotho complex has potential advantages over the currently approved systemically administered FGF23 blocking antibody. Using structure-based drug design we previously identified ZINC13407541 (N-[[2-(2-phenylethenyl)cyclopenten-1-yl]methylidene]hydroxylamine) as a small molecule antagonist for FGF23. Additional structure-activity studies developed a series of ZINC13407541 analogues with enhanced drug-like properties. In this study, we tested in a pre-clinical Hyp mouse homologue of XLH a direct connect analogue (8n) [(E)-2-(4-(tert-butyl)phenyl)cyclopent-1-ene-1-carbaldehyde oxime] that exhibited the greatest stability in microsomal assays, and 13a [(E)-2-((E)-4-methylstyryl)benzaldehyde oxime] that exhibited increased in vitro potency. Using cryo-electron microscopy (Cryo-EM) structure and computational docking, we identified a key binding residue (Q156) of the FGF23 antagonists, ZINC13407541 and its analogues (8n and 13a) in the N-terminal domain of FGF23 protein. Site-directed mutagenesis and bimolecular fluorescence complementation (BiFC)-fluorescence resonance energy transfer (FRET) assay confirmed the binding site of these three antagonists. We found that pharmacological inhibition of FGF23 with either of these compounds blocked FGF23 signaling and increased serum phosphate and 1,25(OH)2D concentrations in Hyp mice. Long-term parenteral treatment with 8n or 13a also enhanced linear bone growth, increased mineralization of bone, and narrowed the growth plate in Hyp mice. The more potent 13a compound had greater therapeutic effects in Hyp mice. Further optimization of these FGF23 inhibitors may lead to versatile drugs to treat excess FGF23-mediated disorders.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

Evolution of the SARS-CoV -2 proteome in three dimensions (3D) during the first 6 months of the COVID -19 pandemic

Understanding the molecular evolution of the SARS-CoV-2 virus as it continues to spread in communities around the globe is important for mitigation and future pandemic preparedness. Three-dimensional structures of SARS-CoV-2 proteins and those of other coronavirusess archived in the Protein Data Bank were used to analyze viral proteome evolution during the first 6 months of the COVID-19 pandemic. Analyses of spatial locations, chemical properties, and structural and energetic impacts of the observed amino acid changes in >48 000 viral isolates revealed how each one of 29 viral proteins have undergone amino acid changes. Catalytic residues in active sites and binding residues in protein–protein interfaces showed modest, but significant, numbers of substitutions, highlighting the mutational robustness of the viral proteome. Energetics calculations showed that the impact of substitutions on the thermodynamic stability of the proteome follows a universal bi-Gaussian distribution. Here detailed results are presented for potential drug discovery targets and the four structural proteins that comprise the virion, highlighting substitutions with the potential to impact protein structure, enzyme activity, and protein–protein and protein–nucleic acid interfaces. Characterizing the evolution of the virus in three dimensions provides testable insights into viral protein function and should aid in structure-based drug discovery efforts as well as the prospective identification of amino acid substitutions with potential for drug resistance.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS2012

Innovative Technologies for Global Space Exploration

Under the direction of NASA's Exploration Systems Mission Directorate (ESMD), Directorate Integration Office (DIO), The Tauri Group with NASA's Technology Assessment and Integration Team (TAIT) completed several studies and white papers that identify novel technologies for human exploration. These studies provide technical inputs to space exploration roadmaps, identify potential organizations for exploration partnerships, and detail crosscutting technologies that may meet some of NASA's critical needs. These studies are supported by a relational database of more than 400 externally funded technologies relevant to current exploration challenges. The identified technologies can be integrated into existing and developing roadmaps to leverage external resources, thereby reducing the cost of space exploration. This approach to identifying potential spin-in technologies and partnerships could apply to other national space programs, as well as international and multi-government activities. This paper highlights innovative technologies and potential partnerships from economic sectors that historically are less connected to space exploration. It includes breakthrough concepts that could have a significant impact on space exploration and discusses the role of breakthrough concepts in technology planning. Technologies and partnerships are from NASA's Technology Horizons and Technology Frontiers game-changing and breakthrough technology reports as well as the External Government Technology Dataset, briefly described in the paper. The paper highlights example novel technologies that could be spun-in from government and commercial sources, including virtual worlds, synthetic biology, and human augmentation. It will consider how these technologies can impact space exploration and will discuss ongoing activities for planning and preparing them.

Hay, Jason↗
DOE OSTI2022

Corrosion-Resistant Coatings on Spent Nuclear Fuel Canisters to Mitigate and Repair Potential Stress Corrosion Cracking (FY22 Status)

This report summarizes the activities performed by Sandia National Laboratories in FY22 to identify and test coating materials for the prevention, mitigation, and/or repair of potential chloride-induced stress corrosion cracking in spent nuclear fuel dry storage canisters. This work continues efforts by Sandia National Laboratories that are summarized in previous reports in FY20 and FY21 on the same topic. The previous work detailed the specific coating properties desired for application and implementation to spent nuclear fuel canisters (FY20) and identified several potential coatings for evaluation (FY21). In FY22, Sandia National Laboratories, in collaboration with four industry partners through a Memorandum of Understanding, started evaluating the physical, mechanical, and corrosion-resistance properties of 6 different coating systems (11 total coating variants) to develop a baseline understanding of the viability of each coating type for use to prevent, mitigate, and/or repair potential stress corrosion on cracking on spent nuclear fuel canisters. This collaborative R&D program leverages the analytical and laboratory capabilities at Sandia National Laboratories and the material design and synthesis capabilities of the industry collaborators. The coating systems include organic (polyetherketoneketone, modified polyimide/polyurea, modified phenolic resin), organic/inorganic ceramic hybrids (silane-based polyurethane hybrid and a quasi-ceramic sol-gel polyurethane hybrid), and hybrid systems in conjuncture with a Zn-rich primer. These coatings were applied to stainless steel coupons (the same coupons were supplied to all vendors by SNL for direct comparison) and have undergone several physical, mechanical, and electrochemical tests. The results and implications of these tests are summarized in this report. These analyses will be used to identify the most effective coatings for potential use on spent nuclear fuel dry storage canisters, and also to identify specific needs for further optimization of coating technologies for their application on spent nuclear fuel canisters. In FY22, Sandia National Laboratories performed baseline testing and atmospheric exposure tests of the coating samples supplied by the vendors in accordance with the scope of work defined in the Memorandum of Understanding. In FY23, Sandia National Laboratories will continue evaluating coating performance with a focus on thermal and radiolytic stability.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2023

Corrosion-Resistant Coatings on Spent Nuclear Fuel Canisters to Mitigate and Repair Potential Stress Corrosion Cracking (FY23 Status)

This report summarizes the activities performed by Sandia National Laboratories in FY23 to identify and test coating materials for the prevention, mitigation, and/or repair of potential chloride-induced stress corrosion cracking in spent nuclear fuel dry storage canisters. This work continues efforts by Sandia National Laboratories that are summarized in previous reports from FY20 through FY22 on the same topic. In FY23, Sandia National Laboratories, in collaboration with five industry partners through a memorandum of understanding, evaluated the physical, mechanical, and corrosion-resistance properties of eight different coating systems. The evaluation included thermal and radiation environments relevant to various time periods of storage for spent nuclear fuel canisters. The coating systems include polymeric (polyetherketoneketone, modified polyimide/polyurea, modified phenolic resin, epoxy), organic/inorganic ceramic hybrids (silane-based polyurethane hybrid and a quasi-ceramic sol-gel polyurethane hybrid), and coatings utilizing a Zn-rich primer applied to stainless steel coupons. The results and implications of these tests are summarized in this report. These analyses will be used to identify the most effective coatings for potential use on spent nuclear fuel dry storage canisters and to identify specific needs for further optimization of coating technologies for application on spent nuclear fuel canisters.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS1997

Spaceflight exposure effects on transcription, activity, and localization of alcohol dehydrogenase in the roots of Arabidopsis thaliana

Although considerable research and speculation have been directed toward understanding a plant's perception of gravity and the resulting gravitropic responses, little is known about the role of gravity-dependent physical processes in normal physiological function. These studies were conducted to determine whether the roots of plants exposed to spaceflight conditions may be experiencing hypoxia. Arabidopsis thaliana (L.) Heynh. plants were grown in agar medium during 6 or 11 d of spaceflight exposure on shuttle missions STS-54 (CHROMEX-03) and STS-68 (CHROMEX-05), respectively. The analysis included measurement of agar redox potential and root alcohol dehydrogenase (ADH) activity, localization, and expression. ADH activity increased by 89% as a result of spaceflight exposure for both CHROMEX-03 and -05 experiments, and ADH RNase protection assays revealed a 136% increase in ADH mRNA. The increase in ADH activity associated with the spaceflight roots was realized by a 28% decrease in oxygen availability in a ground-based study; however, no reduction in redox potential was observed in measurements of the spaceflight bulk agar. Spaceflight exposure appears to effect a hypoxic response in the roots of agar-grown plants that may be caused by changes in gravity-mediated fluid and/or gas behavior.

STS-68 Shuttle Project↗
NASA NTRS2000

Time- and dose-related interactions between glucocorticoid and cyclic adenosine 3',5'-monophosphate on CCAAT/enhancer-binding protein-dependent insulin-like growth factor I expression by osteoblasts

Glucocorticoid has complex effects on osteoblasts. Several of these changes appear to be related to steroid concentration, duration of exposure, or specific effects on growth factor expression or activity within bone. One important bone growth factor, insulin-like growth factor I (IGF-I), is induced in osteoblasts by hormones such as PGE2 that increase intracellular cAMP levels. In this way, PGE2 activates transcription factor CCAAT/enhancer-binding protein-delta (C/EBPdelta) and enhances its binding to a specific control element found in exon 1 in the IGF-I gene. Our current studies show that preexposure to glucocorticoid enhanced C/EBPdelta and C/EBPbeta expression by osteoblasts and thereby potentiated IGF-I gene promoter activation in response to PGE2. Importantly, this directly contrasts with inhibitory effects on IGF-I expression that result from sustained or pharmacologically high levels of glucocorticoid exposure. Consistent with the stimulatory effect of IGF-I on bone protein synthesis, pretreatment with glucocorticoid sensitized osteoblasts to PGE2, and in this context significantly enhanced new collagen and noncollagen protein synthesis. Therefore, pharmacological levels of glucocorticoid may reduce IGF-I expression by osteoblasts and cause osteopenic disease, whereas physiological transient increases in glucocorticoid may permit or amplify the effectiveness of hormones that regulate skeletal tissue integrity. These events appear to converge on the important role of C/EBPdelta and C/EBPbeta on IGF-I expression by osteoblasts.

NASA Program Biomedical Research and Countermeasur↗
DOE OSTI2021

Deep Optical Switching on Subpicosecond Timescales in an Amorphous Ge Metamaterial

Active nanostructured optical components show promise as potential building blocks for novel light-based computing and data processing architectures. However, nanoscale all-optical switches that have low activation powers and high-contrast ultrafast switching have been elusive so far. Here, pump–probe measurements performed on amorphous-Ge-based micro-resonator metasurfaces that exhibit strong resonant modes in the mid-infrared are reported. Relative change is observed in transmittance of ΔT/T ≈ 1 with picosecond (down to τ ≈ 0.5 ps) free carrier relaxation rates, obtained with very low pump fluences of 50 μJ cm –2 . In this work, these observations are attributed to efficient free carrier promotion, affecting light transmittance via high quality-factor optical resonances, followed by an increased electron–phonon scattering of free carriers due to the amorphous crystal structure of Ge. Full-wave simulations based on a permittivity model that describes free-carrier damping through crystal structure disorder find excellent agreement with the experimental data. These findings offer an efficient and robust platform for all-optical switching at the nanoscale.

36 MATERIALS SCIENCE↗