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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Facile bottom-up synthesis of partially oxidized black phosphorus nanosheets as metal-free photocatalyst for hydrogen evolution

Few-layer black phosphorus (BP) nanosheets were first reported as a 2D material for the application of field-effect transistors in 2014 and have stimulated intense activity among physicists, chemists, and material and biomedical scientists, driving research into novel synthetic techniques to produce BP nanosheets. At present, exfoliation is the main route toward few-layer BP nanosheets via employing bulk BP as raw material. However, this is a complicated and time-consuming process, which is difficult for the large-scale synthesis of BP nanosheets. Moreover, BP degrades rapidly when exfoliated to nanoscale dimensions, resulting in the rapid loss of semiconducting properties. Here in this paper, we report the direct wet-chemical synthesis of few-layer BP nanosheets in gram-scale quantities in a bottom-up approach based on common laboratory reagents at low temperature, showing excellent stability due to partial oxidation of surface. Solvent and temperature are two critical factors, controlling not only the formation of BP nanosheets but also the thickness. The as-prepared BP nanosheets can extract hydrogen from pure water (pH = 6.8), exhibiting more than 24-fold higher activity than the well-known C 3 N 4 nanosheets. Our results reporting the ability to prepare few-layer BP nanosheets with a facile, scalable, low-cost approach take us a step closer to real-world applications of phosphorene including next-generation metal-free photocatalysts for photosynthesis.

08 HYDROGEN↗
DOE OSTI2020

Experimental testing of hypotheses for temperature‐ and pH ‐based niche specialization of ammonia oxidizing archaea and bacteria

Summary Investigation of niche specialization in microbial communities is important in assessing consequences of environmental change for ecosystem processes. Ammonia oxidizing bacteria (AOB) and archaea (AOA) present a convenient model for studying niche specialization. They coexist in most soils and effects of soil characteristics on their relative abundances have been studied extensively. This study integrated published information on the influence of temperature and pH on AOB and AOA into several hypotheses, generating predictions that were tested in soil microcosms. The influence of perturbations in temperature was determined in pH 4.5, 6 and 7.5 soils and perturbations in pH were investigated at 15°C, 25°C and 35°C. AO activities were determined by analysing changes in amoA gene and transcript abundances, stable isotope probing and nitrate production. Experimental data supported major predictions of the effects of temperature and pH, but with several significant discrepancies, some of which may have resulted from experimental limitations. The study also provided evidence for unpredicted activity of AOB in pH 4.5 soil. Other discrepancies highlighted important deficiencies in current knowledge, particularly lack of consideration of niche overlap and the need to consider combinations of factors when assessing the influence of environmental change on microbial communities and their activities.

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

Machine learning to discover mineral trapping signatures due to CO 2 injection

Mineral trapping is pursued as a geological CO 2 sequestration (GCS) mechanism because it permanently stores CO 2 in solid phases or minerals. However, CO 2 mineral-trapping mechanisms are poorly understood due to (1) lack of sufficient field and laboratory data characterizing these complex processes, and (2) challenges to develop site-specific reactive-transport models coupling fluid flow and geochemical reactions occurring at various temporal (from milliseconds to years) and spatial (from pore (millimeters) to field (kilometers)) scales. Reactive transport with additional complexities such as heterogeneity can make the simulation outputs even more difficult to interpret because of complex nonlinearity and multi-scale interdependencies. Furthermore, the values of model outputs such as concentrations can vary by several orders of magnitude, making it harder to correlate and characterize the impact of the variables via traditional data interpretation techniques such as exploratory data analyses. Recently, machine learning (ML) has shown promise in feature discovery and in highlighting hidden mechanisms that cannot be obtained by existing data-analytics and statistical methods. In this study, we applied an unsupervised ML approach, non-negative matrix factorization with custom -means clustering (NMF) to the data generated by reactive-transport simulations of GCS. The reactive-transport data consisted of 19 attributes, including four physio-chemical variables (pH, porosity, aqueous CO 2 , and sequestered CO 2 ), six chemical species (K + , Na + , HCO, Ca 2+ , Mg 2+ , Fe 2+ ), and four carbonate minerals (calcite, dolomite, siderite, and ankerite), a feldspar mineral (albite), and four clay minerals (illite, clinochlore, kaolinite, and smectite) over a period of 200 years of simulation time. Furthermore, the simulation data used was for Morrow B sandstone at the Farnsworth hydrocarbon unit in Texas. Data are sampled at two locations within the model domain: (1) at the injection well and (2) 200 m west of the injection well. The injection was performed for a period of 10 years. Using NMF, we estimated the temporal interdependencies among the 19 attributes over a span of 200 years. We found that NMF was able to identify four reaction stages and their dominant attributes; these cannot be directly discerned through traditional visualization (e.g., line plots, Pareto analysis, Glyph-based visualization methods) or exploratory data analysis tools of the simulation data. The four stages were: reactions in the injection phase followed by short-, mid-, and long-term reactions. The NMF analysis also revealed that 10 among the 19 attributes are dominant. These dominant attributes for mineral trapping include calcite, dolomite at injection well, siderite at 200 m away from the injection well, clinochlore, kaolinite, Na + , K + , Ca 2+ , Mg 2+ , pH, and aqeuous CO 2 . Finally, at late times (65–200 years), our results showed that calcite plays a major role in mineral trapping with insignificant contribution from siderite, ankerite, and clay minerals. These findings make the proposed unsupervised ML-model attractive for reactive-transport sensing towards real-time GCS monitoring.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Investigation of soil properties using different techniques of mid‐infrared spectroscopy

Summary Diffuse reflectance spectroscopy (DRF), attenuated total reflectance spectroscopy (ATR) and Fourier transform infrared photoacoustic spectroscopy (PAS) are useful techniques that are commonly used to characterize soil properties. Here, these techniques were used to evaluate individual properties of 1456 paddy soil samples from Nanjing, China, to explore their features in the mid‐infrared range. The diffuse reflectance spectroscopy showed broad and shouldered peaks that ranged from 4000 to 500 cm −1 . Attenuated total reflectance spectroscopy produced main peaks around 1000 cm −1 . Fourier transform infrared photoacoustic spectroscopy spectra showed several moderate intensity peaks in the regions of 4000–2600 and 2500–500 cm −1 . The effective variables (wavenumbers) were selected using an uninformative variable elimination (UVE) algorithm to predict soil pH, and soil organic matter (SOM), total nitrogen (TN) and available phosphorus (AP) contents; it used a self‐adaptive partial least squares model (SAM–PLS). The results showed that selected wavenumbers improved the accuracy of prediction for pH, and SOM, TN and AP contents. For the prediction of pH, ATR spectra showed marginally better performance than the other spectra. The DRF spectroscopy was the optimal method for SOM and TN prediction. Available phosphorus contents were predicted poorly by all three spectra. Furthermore, mid‐infrared incident light paths, absorption modes, sensing styles, as well as peak interference and the prediction model, were the main factors that affected the assessment of soil properties in the three types of spectroscopy. Highlights Soil spectra data were measured with DRF, ATR and PAS spectrometers over the range 4000–500 cm −1 . A UVE algorithm was used to select effective wavenumbers from the full spectrum. The pH, SOM, TN and AP were estimated using three techniques based on a SAM–PLS model. Mid‐infrared incident light paths and absorption modes affected prediction performance of the three techniques.

Ma, F.↗
DOE OSTI2016

Correction for turbidity and pH interference for in situ hexavalent chromium monitoring - 16297

Hexavalent chromium is of increasing concern worldwide because of its toxicity, mobility in aqueous media, and relative abundance in waste effluent from a variety of industrial processes. Some of that waste has reached groundwater aquifers. Because of these factors, the fate and transport of hexavalent chromium in aquifers is of great importance for evaluating risk to fresh water sources and to the biosphere, and for designing means for abatement or remediation. Conventional sampling and analysis of groundwater samples from wells is labor intensive and therefore budget limited. The result is inadequate temporal and spatial characterization of contaminant plumes with respect to rate of movement, concentrations, and contaminant flux. A submersible hexavalent chromium sensor designed for extended-term deployment and based on ultraviolet colorimetry has been developed and tested at the Hanford Site, Washington. Adaptation of the method for in situ measurements requires automatic correction for sample turbidity and pH for every measurement. Turbidity is compensated nephelometrically. A method for estimating sample pH based on absorbance measurements made using two different wavelengths is presented. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2022

Mechanistic Differences between Electrochemical Hydrogenation and Hydrogenolysis of 5‐Hydroxymethylfurfural and Their pH Dependence

Abstract Hydrogenation and hydrogenolysis are two important reactions for electrochemical reductive valorization of biomass‐derived oxygenates such as 5‐hydroxymethylfurfural (HMF). In general, hydrogenolysis (which combines hydrogenation and deoxygenation) is more challenging than hydrogenation (which does not involve the cleavage of carbon–oxygen bonds). Thus, identifying factors and conditions that can promote hydrogenolysis is of great interest for reductive valorization of biomass‐derived oxygenates. For the electrochemical reduction of HMF and its derivatives, it is known that aldehyde hydrogenation is not a part of aldehyde hydrogenolysis but rather a competing reaction; however, no atomic‐level understanding is currently available to explain their electrochemical mechanistic differences. In this study, combined experimental and computational investigations were performed using Cu electrodes to elucidate the key mechanistic differences between electrochemical hydrogenation and hydrogenolysis of HMF. The results revealed that hydrogenation and hydrogenolysis of HMF involve the formation of different surface‐adsorbed intermediates via different reduction mechanisms and that lowering the pH promoted the formation of the intermediates required for aldehyde and alcohol hydrogenolysis. This study for the first time explains the origins of the experimentally observed pH‐dependent selectivities for hydrogenation and hydrogenolysis and offers a new mechanistic foundation upon which rational strategies to control electrochemical hydrogenation and hydrogenolysis can be developed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Evolution of a multi-step phosphorelay signal transduction system in Ensifer : recruitment of the sigma factor RpoN and a novel enhancer-binding protein triggers acid-activated gene expression: A model for acid-activated lpiA-acvB expression

Most Ensifer strains are comparatively acid sensitive, compromising their persistence in low pH soils. In the acid-tolerant strain Ensifer medicae WSM419, the acid-activated expression of lpiA is essential for enhancing survival in lethal acidic conditions. In this work, we characterise a multi-step phosphorelay signal transduction pathway consisting of TcsA, TcrA, FsrR, RpoN and its cognate enhancer-binding protein EbpA , which is required for the induction of lpiA and the downstream acvB gene. The fsrR, tcrA, tcsA and rpoN genes were constitutively expressed, whereas lpiA and acvB were strongly acid-induced. RACE mapping revealed that lpiA/acvB were co-transcribed as an operon from an RpoN promoter. In most Ensifer species, lpiA/acvB is located on the chromosome and the sequence upstream of lpiA lacks an RpoN-binding site. Almost all Ensifer meliloti strains completely lack ebpA, tcrA, tcsA and fsrR regulatory loci. In contrast, E. medicae strains have lpiA/acvB and ebpA/tcrA/tcsA/fsrR co-located on the pSymA megaplasmid, with lpiA/acvB expression coupled to an RpoN promoter. Here we provide a model for the expression of lpiA/acvB in E. medicae . This unique acid-activated regulatory system provides insights into an evolutionary process which may assist the adaptation of E. medicae to acidic environmental niches.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

Florida International University Research on Soil and Groundwater Contamination at DOE's Hanford and Savannah River Sites - 18547

Nuclear weapons production and other defense-related activities at U.S. Department of Energy (DOE) sites have resulted in radionuclide and heavy metal contamination in surface and subsurface environments nationwide. The DOE Office of Environmental Management (DOE EM) faces a number of environmental challenges that are technically complex and unique to EM with tremendous associated cleanup costs. The success of the DOE EM mission will require development and insertion of innovative approaches and novel technologies to address the significant challenges associated with the remaining cleanup of contaminated sites. A key focus of the applied research portfolio addresses data gaps related to the behavior and chemistry of radionuclides of concern as well as the co-mingling of these contaminants in groundwater at EM sites such as Hanford, Savannah River, Oak Ridge and others. Florida International University (FIU) is conducting research in conjunction with Pacific Northwest National Laboratory (PNNL) and savannah River National Laboratory (SRNL) scientists to support environmental remediation efforts at Hanford and SRS. This research is focused on remediation technologies for contaminated soil and groundwater as well as the assessment of the fate and transport of contaminants in the environment. The overall objective is to reduce contaminant mobility through the development and application of state-of-the-art scientific and environmental remediation technologies. The FIU strategy is to conduct basic science research that fills knowledge gaps and complements work conducted at DOE sites. Support to Hanford includes contributing to the understanding of {sup 99}Tc chemistry and the fate and transport mechanisms of co-mingled contaminants including {sup 99}Tc, U(VI), Cr, and iodine (I). FIU has also provided basic science research that supports a treatability study currently underway at Hanford, which uses ammonia gas injection to manipulate pH and immobilize U(VI) in the subsurface. In addition, support for long-term monitored natural attenuation is provided through geophysical research that monitors subsurface contaminant and microbial responses. Research to evaluate the environmental factors that control the fate and transport of contaminants and co-contaminants in soil and groundwater is being performed for SRS. This research has contributed to the development, design, and deployment of innovative strategies to enhance the natural attenuation processes and to validate novel in situ remediation technologies. The SRS EM test bed demonstrations directly benefit SRS cleanup initiatives. Current investigations focus on natural organic compounds, such as humate, as a potential amendment for the treatment of uranium in groundwater associated with the SRS F-Area Seepage Basins plume, investigates the synergy between humate and silica to optimize the pH adjustment strategy for uranium remediation and investigates the interaction of Tc and I with soil from the Four Mile Branch wetland. Collaborative relationships between FIU and the national laboratories have provided synergy and benefits over the years to FIU, the national laboratories, the DOE complex, and the DOE EM mission. By working closely with the national laboratories, FIU research is not only closely aligned with the cleanup mission priorities at the DOE sites, but complements and supports the work at national laboratories. This coordination and leveraging of research efforts results in time- and cost-savings, and accelerates progress in the DOE EM environmental restoration mission. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Fracture mechanics of shales under chemically reactive conditions

Fracture growth processes under subsurface conditions are known to be affected by fluid chemical environment. Chemical effects on fracture growth are likely to be relevant during host rock and organic matter diagenesis and catagenesis, hydraulic fracturing, in systems undergoing enhanced oil recovery, in geothermal systems, and in CO 2 sequestration reservoirs. To address the chemical effects on opening-mode fracture growth under a wide range in fluid chemical conditions and for different rock types we conducted double-torsion fracture mechanics tests to determine mode-I fracture toughness (KIC), subcritical index (SCI), and the stress-intensity factor vs fracture velocity (K-V) behavior. We tested sandstones, shales and, altered crystalline rocks. Samples were tested in aqueous conditions with variable salinity, solution pH, and at temperatures of up to 70 °C. Fracture growth in shales is highly sensitive to the environmental conditions, with a reduction of KIC of up to 47% from ambient air to water-saturated conditions. The primary interactions between shales and reactive solutions are clay-water and carbonate dissolution. For clay-rich Woodford and Mancos shales, solutions with higher salinity reduce subcritical fracture growth, while acidic conditions favor fracture growth in carbonate-rich Marcellus shale. Increasing the solution temperature promotes fracture growth. In sandstone, chemical effects on fracture parameters are most pronounced for clay- and carbonate-rich samples. Both KIC and SCI are lower in water than in air for nearly all sandstone lithologies tested. SCI is further reduced in chlorite-cemented Tuscaloosa Sandstone in acidic solutions. Mount Simon Sandstone is also sensitive to pH, most significantly in diagenetically bleached samples. Compositionally mature Aztec Sandstone is affected by water saturation, but shows little sensitivity to chemical environment. Silicified gabbro shows a slight reduction in KIC but a >60% reduction in SCI in aqueous environments compared to ambient conditions. The reduction in SCI is most pronounced in alkaline and saline solutions, suggesting silica dissolution and cation exchange at the fracture tip facilitate subcritical fracture growth. Limited reduction in KIC is attributed to low permeability. Overall, our results demonstrate that fracture properties depend strongly on water saturation, on fluid composition and pH, and on temperature, with an increase in temperature lowering fracture resistance.

58 GEOSCIENCES↗
DOE OSTI2015

Systematic study on the influence of the morphology of α-MoO{sub 3} in the selective oxidation of propylene

A variety of morphologically different α-MoO{sub 3} samples were prepared by hydrothermal synthesis and applied in the selective oxidation of propylene. Their catalytic performance was compared to α-MoO{sub 3} prepared by flame spray pyrolysis (FSP) and a classical synthesis route. Hydrothermal synthesis from ammonium heptamolybdate (AHM) and nitric acid at pH 1–2 led to ammonium containing molybdenum oxide phases that were completely transformed into α-MoO{sub 3} after calcination at 550 °C. A one-step synthesis of α-MoO{sub 3} rods was possible starting from MoO{sub 3}·2H{sub 2}O with acetic acid or nitric acid and from AHM with nitric acid at 180 °C. Particularly, if nitric acid was used during synthesis, the rod-like morphology of the samples could be stabilized during calcination at 550 °C and the following catalytic activity tests, which was beneficial for the catalytic performance in propylene oxidation. Characterization studies using X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman spectroscopy showed that those samples, which retained their rod-like morphology during the activity tests, yielded the highest propylene conversion. - Graphical abstract: Hydrothermal synthesis from MoO{sub 3}·2H{sub 2}O in the presence of HNO{sub 3} led to rod-shaped particles which mainly expose (1 0 0) facets which are the most active surfaces. - Highlights: • Hydrothermal synthesis of MoO3 resulted in either rod or slab shaped particles depending on pH. • At pH<0 rods stable towards calcination and catalytic activity testing were formed. • Rod shaped particles had significantly higher activity than slab shaped ones. • The rod shaped particles mainly expose the (1 0 0) facets which are the most active surfaces. • Total surface area is not main determining factor for catalytic activity.

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

Final Technical Report Under SC0018278

Work supported by the grant "Stability and Control of Burning Tokamak Plasmas with Resistive Walls" in the period Aug 2017 to Aug 2018 can be cast in three general categories: (1) linear tearing regimes and the effects on the response to error fields and resistive walls: (2) nonlinear tearing modes in the presence of error fields, with locking; and (3) energetic particle effects. In the first category, we have completed a study of tearing mode regimes with extended MHD effects, including parallel dynamics and toroidal effects, notably favorable average curvature. This work has been presented at the 2018 Sherwood Conference in Ref.[1]. This work has been published in the ArXiv in Ref.[2] and is being prepared for publication in Physics of Plasmas. A systematic study of shaping in a tokamak plasma with resistive tearing layers and a resistive wall has been presented in the Ph D dissertation[3] by Dov Rhodes, a student of Andrew Cole at Columbia University. John Finn was on Rhodes's Ph D committee, and was a co-author of a paper published in Physics of Plasmas on that work. A detailed study of nonlinear tearing modes in the presence of finite beta, favorable average curvature, and an error field has been nearly completed. In this study it was found that the response to an error field with real frequency a tearing layer agreed with analytic results, and that tearing mode saturation by flattening of the current profile as well as destabilization due to flattening of the pressure profile were important factors in the locking process. This work was presented at the 2017 APS/DPP Conference and at the 2018 Sherwood Conference. The effects of energetic ions on tearing modes was presented at the 2017 APS/DPP Conference and in the Ph D dissertation of Michael Halfmoon. John Finn served as a committee member on Halfmoon's Ph D committee. Extensions to this work including two-fluid effects were performed and presented at the APS/DPP Conference in 2017.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2017

Diverse plant-associated pleosporalean fungi from saline areas: Ecological tolerance and nitrogen-status dependent effects on plant growth

Similar to mycorrhizal mutualists, the rhizospheric and endophytic fungi are also considered to act as active regulators of host fitness (e.g., nutrition and stress tolerance). Despite considerable work in selected model systems, it is generally poorly understood how plant-associated fungi are structured in habitats with extreme conditions and to what extent they contribute to improved plant performance. Here, we investigate the community composition of root and seed-associated fungi from six halophytes growing in saline areas of China, and found that the pleosporalean taxa (Ascomycota) were most frequently isolated across samples. A total of twenty-seven representative isolates were selected for construction of the phylogeny based on the multi-locus data (partial 18S rDNA, 28S rDNA, and transcription elongation factor 1-a), which classified them into seven families, one clade potentially representing a novel lineage. Fungal isolates were subjected to growth response assays by imposing temperature, pH, ionic and osmotic conditions. The fungi had a wide pH tolerance, while most isolates showed a variable degree of sensitivity to increasing concentration of either salt or sorbitol. Subsequent plant fungal co-culture assays indicated that most isolates had only neutral or even adverse effects on plant growth in the presence of inorganic nitrogen. Interestingly, when provided with organic nitrogen sources the majority of the isolates enhanced plant growth especially above ground biomass. Most of the fungi preferred organic nitrogen over its inorganic counterpart, suggesting that these fungi can readily mineralize organic nitrogen into inorganic nitrogen. Microscopy revealed that several isolates can successfully colonize roots and form melanized hyphae and/or microsclerotia-like structures within cortical cells suggesting a phylogenetic assignment as dark septate endophytes. Furthermore, this work provides a better understanding of the symbiotic relationship between plants and pleosporalean fungi, and initial evidence for the use of this fungal group in benefiting plant production.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2017

The Tiam1 guanine nucleotide exchange factor is auto-inhibited by its pleckstrin homology coiled-coil extension domain

T-cell lymphoma invasion and metastasis 1 (Tiam1) is a Dbl-family guanine nucleotide exchange factor (GEF) that specifically activates the Rho-family GTPase Rac1 in response to upstream signals, thereby regulating cellular processes including cell adhesion and migration. Tiam1 contains multiple domains, including an N-terminal pleckstrin homology coiled-coiled extension (PH n -CC-Ex) and catalytic Dbl homology and C-terminal pleckstrin homology (DH-PH c ) domain. Previous studies indicate that larger fragments of Tiam1, such as the region encompassing the N-terminal to C-terminal pleckstrin homology domains (PH n -PH c ), are auto-inhibited. However, the domains in this region responsible for inhibition remain unknown. Here, we show that the PH n -CC-Ex domain inhibits Tiam1 GEF activity by directly interacting with the catalytic DH-PH c domain, preventing Rac1 binding and activation. Enzyme kinetics experiments suggested that Tiam1 is auto-inhibited through occlusion of the catalytic site rather than by allostery. Small angle X-ray scattering and ensemble modeling yielded models of the PH n -PH c fragment that indicate it is in equilibrium between “open” and “closed” conformational states. Lastly, single-molecule experiments support a model in which conformational sampling between the open and closed states of Tiam1 contributes to Rac1 dissociation. Our results highlight the role of the PH n -CC-Ex domain in Tiam1 GEF regulation and suggest a combinatorial model for GEF inhibition and activation of the Rac1 signaling pathway.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

Enhanced Iron Solubility at Low pH in Global Aerosols

The composition and oxidation state of aerosol iron were examined using synchrotron-based iron near-edge X-ray absorption spectroscopy. By combining synchrotron-based techniques with water leachate analysis, impacts of oxidation state and mineralogy on aerosol iron solubility were assessed for samples taken from multiple locations in the Southern and the Atlantic Oceans; and also from Noida (India), Bermuda, and the Eastern Mediterranean (Crete). These sampling locations capture iron-containing aerosols from different source regions with varying marine, mineral dust, and anthropogenic influences. Across all locations, pH had the dominating influence on aerosol iron solubility. When aerosol samples were approximately neutral pH, iron solubility was on average 3.4%; when samples were below pH 4, the iron solubility increased to 35%. This observed aerosol iron solubility profile is consistent with thermodynamic predictions for the solubility of Fe(III) oxides, the major iron containing phase in the aerosol samples. Source regions and transport paths were also important factors affecting iron solubility, as samples originating from or passing over populated regions tended to contain more soluble iron. Although the acidity appears to affect aerosol iron solubility globally, a direct relationship for all samples is further confounded by factors such as anthropogenic influence, aerosol buffer capacity, mineralogy and physical processes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Nucleon axial form factor from elementary target data

Precise neutrino-nucleon amplitudes are essential ingredients for predicting neutrino event rates in current and upcoming long-baseline neutrino oscillation experiments. A common neutrino interaction with a low reaction threshold and with most of the energy carried by two final state particles is quasielastic scattering, for which the nucleon axial form factor, 𝐹 𝐴⁡ (𝑄 2 ), is a dominant source of uncertainty. Improvements to the nucleon axial form factor rely on neutrino scattering data with elementary targets to reduce or eliminate the need for nuclear modeling systematics. This work examines constraints on the nucleon axial form factor that can be achieved from datasets of neutrino scattering on deuterium targets, Lattice QCD predictions, and from the recent hydrogen target data from the MINERvA Collaboration. Significant tension is found between hydrogen and deuterium target data, suggesting that extractions from deuterium underestimate both the central value and uncertainty of the form factor. Parametrizations for and uncertainties of the nucleon axial form factor using the 𝑧 expansion are provided.

FOS: Physical sciences↗
DOE OSTI2026

Pore-Scale Transport Effects in Electrochemical CO 2 Reduction on Gold via Coupled Microkinetic-Transport Modeling

A pore-resolved modeling framework is developed to quantify how pore-scale transport affects the intrinsic microkinetics of CO 2 -to-CO on Au. A DFT-informed microkinetic model is coupled self-consistently to a Generalized-Modified Poisson–Nernst–Planck (GMPNP) transport description in a single, electrolyte-filled cylindrical pore, allowing local concentrations and potential to feed back into site-specific reaction rates. FIB-SEM is used to determine pore sizes within realistic electrode materials. Across pore diameters, d p = 10–6000 nm, the surface-averaged CO 2 reduction rate is systematically reduced relative to the ideal microkinetic baseline where mass transport is not accounted for; the effectiveness factor 𝜂 𝑠,CO 2 , which quantifies this ratio, decreases rapidly at more negative potentials and is about 1% near −1.0 V vs SHE due to reactant depletion. Spatial maps reveal pore-bulk alkalization that emerges at higher cathodic bias, with a small, near-wall pH dip due to electrostatic repulsion of hydroxide at the cathode interface. For a fixed aspect ratio L p /d p , narrower pores exhibit larger 𝜂 𝑠,CO 2 by shortening diffusion paths, whereas variations in the aspect ratio L p /d p play a secondary role. A dimensionless analysis (surface/bulk Damköhler numbers) delineates operating regimes. In conclusion, this work offers a concept for incorporating microkinetic models into homogenized porous-electrode models through effectiveness factors and pore-size distribution.

Au-catalyst↗
DOE OSTI2018

Statistical Optimization of Polyhydroxybutyrate Production by Bacillus Pumilus H9 Using Cow Dung as a Cheap Carbon Source by Response Surface Methodology

A gram positive bacterium (designated strain H9) found to be a potential polyhydroxybutyrate (biodegradable polymer) producer was isolated from the soil samples of a stress prone environment (municipal waste areas). This bacterium was identified as Bacillus pumilus H9 from its morphological, physiological and 16S rRNA gene sequence analysis. A four-factor central composite rotary design was employed to optimize the medium and to find out the interactive effects of four variables, viz. concentrations of cow dung, sucrose, peptone and pH on PHB production. Using response surface methodology, a second-order polynomial equation was obtained by multiple regression analysis and a yield of 2.47 g/L of PHB dry weight was achieved from the optimized medium at pH 7. Here, we report cow dung as a cheap carbon source for the production of PHB. Further, phbA, phbB and phbC genes were amplified by polymerase chain reaction which confirms the bacterium to be able to produce polyhydroxybutyrate.

36 MATERIALS SCIENCE↗