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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 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Understanding How Reservoir Operations Influence Methane Emissions: A Conceptual Model

Because methane is a potent greenhouse gas (GHG), understanding controls on methane emissions from reservoirs is an important goal. Yet, reservoirs are complex ecosystems, and mechanisms by which reservoir operations influence methane emissions are poorly understood. In part, this is because emissions occur in ‘hot spots’ and ‘hot moments’. In this study, we address three research questions, ‘What are the causal pathways through which reservoir operations and resulting water level fluctuations (WLF) influence methane emissions?’; ‘How do influences from WLF differ for seasonal drawdown and diurnal hydropeaking operations?’; and ‘How does understanding causal pathways inform practical options for mitigation?’. A graphical conceptual model is presented that links WLF in reservoirs to methane emissions via four causal pathways: (1) water-column mixing (2) drying–rewetting cycles, (3) sediment delivery and redistribution, and (4) littoral vegetation. We review what is known about linkages for WLF at seasonal and diurnal resolutions generate research questions, and hypothesize strategies for moderating methane emissions by interrupting each causal pathway. Those related to flow management involve basin-scale management of tributary flows, seasonal timing of hydropeaking (pathway #1), timing and rates of drawdown (pathway #2). In addition, we describe how sediment (pathway #3) and vegetation management (pathway #4) could interrupt linkages between WLF and emissions. We demonstrate the strength of conceptual modeling as a tool for generating plausible hypotheses and suggesting mitigation strategies. Future research is needed to develop simpler models at appropriate timescales that can be validated and used to manage flow releases from reservoirs.

13 HYDRO ENERGY↗
DOE OSTI2024

Methodology for Exploring Water and Hydropower Operating Criteria That Simultaneously Improve Economic and Environmental Considerations

Despite the reliability and flexibility of hydropower, the operation of hydroelectric power plants may have significant impacts on the downstream river system, including its water stage, sediment transport, and water temperature, ultimately affecting the ecology. To address these challenges, there is a need to identify water scheduling patterns that improve both hydropower economics and the environment relative to current operations. This paper presents a new methodology to explore promising operational criteria/rules that can achieve such improvements. Typical environmental impact statements and relicensing processes generally perform detailed site-specific analyses of a few alternatives that focus on reservoir water release operating rules and their associated environmental impacts. In contrast, the methodology presented in this article uses a widely applicable approach that explores a much larger solution space. This large set of potential alternatives can be represented in a multidimensional space for which one axis represents the economic value and the other axis quantify individual environmental impacts (e.g., sediment transport and fish growth), and they are explored via two approaches: a Monte Carlo simulation that identifies “win–win” alternatives and a multi-objective optimization problem that identifies Pareto-optimal alternatives.

13 HYDRO ENERGY↗
DOE OSTI2023

Inhomogeneous Enrichment of Radioactive Nuclei in the Galaxy: Deposition of Live 53 Mn, 60 Fe, 182 Hf, and 244 Pu into Deep-sea Archives. Surfing the Wave?

Abstract While modeling the galactic chemical evolution (GCE) of stable elements provides insights to the formation history of the Galaxy and the relative contributions of nucleosynthesis sites, modeling the evolution of short-lived radioisotopes (SLRs) can provide supplementary timing information on recent nucleosynthesis. To study the evolution of SLRs, we need to understand their spatial distribution. Using a three-dimensional GCE model, we investigated the evolution of four SLRs: 53 Mn, 60 Fe, 182 Hf, and 244 Pu with the aim of explaining detections of recent (within the last ≈1–20 Myr) deposition of live 53 Mn, 60 Fe, and 244 Pu of extrasolar origin into deep-sea reservoirs. We find that core-collapse supernovae are the dominant propagation mechanism of SLRs in the Galaxy. This results in the simultaneous arrival of these four SLRs on Earth, although they could have been produced in different astrophysical sites, which can explain why live extrasolar 53 Mn, 60 Fe, and 244 Pu are found within the same, or similar, layers of deep-sea sediments. We predict that 182 Hf should also be found in such sediments at similar depths.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Mid-Holocene Antarctic sea-ice increase driven by marine ice sheet retreat

Abstract. Over recent decades Antarctic sea-ice extent has increased, alongside widespread ice shelf thinning and freshening of waters along the Antarctic margin. In contrast, Earth system models generally simulate a decrease in sea ice. Circulation of water masses beneath large-cavity ice shelves is not included in current Earth System models and may be a driver of this phenomena. We examine a Holocene sediment core off East Antarctica that records the Neoglacial transition, the last major baseline shift of Antarctic sea ice, and part of a late-Holocene global cooling trend. We provide a multi-proxy record of Holocene glacial meltwater input, sediment transport, and sea-ice variability. Our record, supported by high-resolution ocean modelling, shows that a rapid Antarctic sea-ice increase during the mid-Holocene (∼ 4.5 ka) occurred against a backdrop of increasing glacial meltwater input and gradual climate warming. We suggest that mid-Holocene ice shelf cavity expansion led to cooling of surface waters and sea-ice growth that slowed basal ice shelf melting. Incorporating this feedback mechanism into global climate models will be important for future projections of Antarctic changes.

58 GEOSCIENCES↗
DOE OSTI2025

Water Column Respiration in the Yakima River Basin is Explained by Temperature, Nutrients and Suspended Solids

Understanding aquatic ecosystem metabolism involves the study of two key processes: carbon fixation via primary production and organic C mineralization as total ecosystem respiration (ERtot). In streams and rivers, ERtot includes respiration in the water column (ERwc) and in the sediments (ERsed). While literature surveys suggest that ERsed is often a dominant contributor to ERtot, recent studies indicate that the relative influence of sediment-associated processes versus water column processes can fluctuate along the river continuum. Still, a comprehensive understanding of the factors contributing to these shifts within basins and across stream orders is needed. Here we contribute to this need by measuring ERwc and collecting water samples across 47 sites in the Yakima River basin, Washington, USA. We found that ERwc rates varied throughout the basin during baseflow conditions, ranging from –7.38 to 0.36 g O2 m?3 d?1, and encompassed the range of ERwc literature values. Additionally, by comparing to ERtot estimates for rivers across the contiguous United States, we suggest that the contribution of ERwc rates to reach-scale ERtot rates across the Yakima River was likely highly variable, but we did not test this directly. We observed that temperature, nutrient concentrations (dissolved organic carbon, total dissolved nitrogen), and total suspended solids explained 41% of ERwc variability across the basin. Our findings highlight the potential relevance of water column processes in aquatic ecosystem metabolism, with the Yakima River basin serving as an environmentally diverse river network representative of the larger Columbia River basin that spans much of the Pacific Northwest region of the United States. Our results are generally congruent with previous work, suggesting that the observed variability and suite of associated environmental factors influencing ERwc are potentially transferable across basins.

Laan, Maggi M.↗
DOE OSTI2023

Importance of ice nucleation and precipitation on climate with the Parameterization of Unified Microphysics Across Scales version 1 (PUMASv1)

Cloud microphysics is critical for weather and climate prediction. In this work, we document updates and corrections to the cloud microphysical scheme used in the Community Earth System Model (CESM) and other models. These updates include a new nomenclature for the scheme, now called Parameterization of Unified Microphysics Across Scales (PUMAS), and the ability to run the scheme on graphics processing units (GPUs). The main science changes include refactoring an ice number limiter and associated changes to ice nucleation, adding vapor deposition onto snow, and introducing an implicit numerical treatment for sedimentation. We also detail the improvements in computational performance that can be achieved with GPU acceleration. We then show the impact of these scheme changes on the (a) mean state climate, (b) cloud feedback response to warming, and (c) aerosol forcing. We find that corrections are needed to the immersion freezing parameterization and that ice nucleation has important impacts on climate. We also find that the revised scheme produces less cloud liquid and ice but that this can be adjusted by changing the loss process for cloud liquid (autoconversion). Furthermore, there are few discernible effects of the PUMAS changes on cloud feedbacks but some reductions in the magnitude of aerosol–cloud interactions (ACIs). Small cloud feedback changes appear to be related to the implicit sedimentation scheme, with a number of factors affecting ACIs.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Fluid Induced Elemental and Mineralogy Alterations of Caney Shale

ABSTRACT: Studies were conducted on cores and rock cuttings recovered from two wells drilled in Caney shale in the Southern Oklahoma. Mineralogical compositions of these samples were obtained by X-Ray Diffraction (XRD) measurements using two methods of sample preparation: conventional powder (by crushing and grinding of rock fragments) and spray-drying of micronized rock powder method. Microstructure and microanalysis were acquired by Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS). Batch experiments were then conducted using selected rock samples and fracturing fluid whilst deionized water was used as control sample for fluid/rock interaction. These were conducted at 95°C and ambient pressure for various time periods to assess the geochemical reactivity of the Caney shale. The rock samples were subsequently recovered from fluid, dried and analysis repeated using identical XRD and SEM/EDS measurements, following the same conditions. Preliminary experimental results show rock mineralogical compositions are predominantly quartz with relatively high clay content. The clay minerals are mainly illite. Carbonate content is less than 10% by weight for most samples, with other non-clay minerals pyrite, albite, dolomite, and some apatite. In general, sprayed samples showed more intense peaks and less full width at half maxima (FWHM) relative to conventional rock-powder samples. Post-experimental mineralogical changes were observed in samples with clay portions breaking down to amorphous entities. As expected, dissolution of carbonates (calcite and dolomite) was observed and newly detected dissolution of biogenic micro quartz resulted in formation of amorphous silica. 1.0 INTRODUCTION Formation of sedimentary rocks involves processes where rock sediments are emplaced with fluids starting interactions that persist over long periods. During the lithification process, sediments and fluids react and attain equilibrium state. This equilibrium is disturbed during drilling, completion, hydraulic fracturing and other operations that involve the introduction of engineered fluids into the subsurface. To return to equilibrium, dissolution and precipitation of minerals may occur. These reactions have implications on the petrophysical properties of the reservoir. Whiles dissolution and precipitation of minerals can enhance porosity and permeability, the reverse can also be true. For example, when acidic fluids are introduced into formations with high carbonate contents, carbonate minerals dissolve into solution thus increasing the porosity and permeability of the formation. In contrast, when alkaline fluids with pH above 11 are introduced into an illite-rich shale formation, the rock-fluid interaction leads to de-flocculation of illite platelets causing substantial increase in clay fines migration, consequently significant reduction in permeability (Salles et al., 2008).

Awejori, G.↗
DOE OSTI2021

Mastering Medaka Culture: Improved Techniques for Increasing Egg and Fry Production in Japanese Rice Fish ( Oryzias latipes )

Aquatic systems are integral to ecosystem function and human health. By trapping sediments and retaining nutrients, wetlands protect our water quality. However, a wetland’s capacity to trap sediments and nutrients also means they can capture many contaminants (e.g., heavy metals and radionuclides) released into the environment due to anthropogenic activities. Both heavy metals and radionuclides have detrimental effects on wildlife at acute dosages. However, little is known regarding underlying biological responses associated with chronic low dose exposure to both ionizing radiation and heavy metals. Our long-term research goal is to work to fill this knowledge gap using Medaka (Oryzias latipes), small fish amenable to experimental manipulation. However, the current study focused on altering the husbandry protocol of a laboratory colony of Medaka in a way that would increase colony size to at least 400 individual fish over a six-week period. At the beginning of our work, we followed a strict cleaning, feeding and egg harvesting protocol. Two weeks into our work, we suspected that food limitations may be negatively impacting egg production and noticed fungal growth on eggs. Thus, we altered the feeding regime and egg harvesting protocol. The altered protocol more than tripled egg production and almost doubled of fry production. By the end of our study the colony had 673 individuals: 191 adults and 482 fry. Furthermore, our protocol changes resulted in growth of the colony at sufficient numbers to begin experiments related to investigating sub-lethal impacts of heavy metals and radionuclides on Medaka.

Thompson, Melissa↗
DOE OSTI2022

Calcium carbonate minerals as scavengers of metals and radionuclides: Their role in natural attenuation and remediation

Calcium carbonates (CaCO3) are ubiquitous naturally occurring minerals in subsurface sediments. Calcium carbonate coatings are common in many terrestrial environments and are known to coat a variety of reactive mineral surfaces in soils and sediments, altering their reactivity and chemical behavior. For these reasons, contaminant interactions with CaCO3 minerals are relevant to contaminant fate and transport. Significant advancements have been made recently toward identifying relevant contaminant (e.g., U, I, and Cr) attenuation mechanisms, which may also serve as a basis for in situ remediation strategies. Hence, the objective of this review paper is to 1) describe the state-of-knowledge of calcium carbonate minerals as universal scavengers of metals and radionuclides; 2) provide a state of the science of how calcium carbonate interactions affect contaminant fate and transport in the subsurface environmental systems; and 2) provide insights on the use of calcium carbonate natural attenuation mechanisms and their application to the remediation of complex sites. Knowledge gaps are also identified that, when closed, can advance the use of carbonate minerals for in situ remedy applications.

Qafoku, Nikolla↗
DOE OSTI2023

CRITICAL MINERAL RESOURCE ASSESSMENT OF COALS FROM THE POWDER RIVER BASIN, WYOMING, USA

Coal and associated sediments are potential sources of Rare Earth Elements (REE) and other critical minerals necessary for many consumer and defense-related products and development of energy technologies. For this study, 15 samples were sourced from Dry Fork Mine within the Powder River Basin near Gillette, Wyoming, to determine REE content along with select transition metals (t-metals) of interest in non-combusted coals and associated sediments. An excavator collected samples along a mine highwall, within benched intervals representing a foot to a few feet of coal strata. Homogenized sample subsets were crushed in an aluminum-ceramic vial, then passed through a 106-micron sieve. Sieved samples were pyrolyzed by a LECO TGA-108, which concurrently measured sample moisture, volatile, and ash content. Residual ash was then fused into a glass bead with lithium metaborate at a 6:1 Li-metaborate to sample ratio and then dissolved in 20% nitric acid. The nitric acid solutions containing digested beads were then diluted and passed through a 0.45 micron syringe filter. Filtered samples were analyzed by ICP-MS for REE and select t-metals. Reagent blanks were analyzed to assess for any potential contamination. Total REE plus Y (REE+Y) concentrations across the 15 samples range from 52 ppm to 1015 ppm with an average of 477 ppm on a dry ash basis. When normalized to upper continental crust (UCC; Taylor and McLennan, 1985) values, 13 of the 15 samples show average enrichment factors (EF) for REE+Y greater than 1. EF values indicate M-type enrichment (Sm through Er), as opposed to distinct preferential enrichment of light or heavy REE. T-metals with the highest average concentrations are V, Cu, Ni, and Zr at 215, 243, 123, and 118 ppm, respectively. Multiple t-metals had EF>1; however, Cu, Ge, and Sb have the highest average EF relative to UCC for t-metals, at 9.7, 8.0, and 17.0, respectively.

Copeland, Grant↗
DOE OSTI2024

The dynamics and stratigraphy of distributary channel networks (Final Technical Report)

Sedimentary reservoirs are frequently composed of the deposits of distributary channel networks. These networks are associated with coarse sediments (and high permeability) within the channel network, and relatively fine sediments (and low permeability) outside the channel network. The shape of the network is complex, and a product of the environmental boundary conditions under which it grows (Figure 1). These systems control heterogeneity at small and large scales within sedimentary basins, and understanding this heterogeneity and the links between scales represents the important scientific frontier addressed by this project.

58 GEOSCIENCES↗
DOE OSTI2025

A high-resolution record of Late Holocene drought in the eastern Sierra Nevada (California, USA) from June Lake carbonate geochemistry

As historic drought conditions become more common in western North America, Late Quaternary hydroclimate records become vital for putting present anthropogenic conditions into a longer-term context. Here, we establish a high-resolution record of drought for the eastern Sierra Nevada (California) using lacustrine carbonates from well-dated sediment cores. We used oxygen and carbon stable-isotope ratios, combined with high-resolution scanning X-ray fluorescence counts of calcium (Ca) and titanium (Ti), to reconstruct the drought record over the last 4600 years in June Lake. We found elevated δ 18 O and δ 13 C carbonate isotope values coinciding with peaks in both total inorganic carbon and Ca/Ti, suggesting enhanced carbonate precipitation in response to evaporative concentration of lake water. At least six intervals of prolonged (centennial-scale) carbonate deposition were identified, including three pulses during the Late Holocene Dry Period (LHDP; ~3500–2000 cal yr BP), the Medieval Climate Anomaly (~1200–800 cal yr BP), and the Current Warm Period, which began around 100 cal yr BP. This record highlights the complexities of the LHDP, an interval that was more variable at June Lake than has been previously described in regional records.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Relaxation behavior in low-frequency complex conductivity of sands caused by bacterial growth and biofilm formation by Shewanella oneidensis under a high-salinity condition

Complex electrical conductivity is increasingly used to monitor subsurface processes associated with microbial activities because microbial cells mostly have surface charges and thus electrical double layers. Although highly saline environments are frequently encountered in coastal and marine sediments, there are limited data available on the complex conductivity associated with microbial activities under a high-salinity condition. Therefore, we have developed the spectral responses of complex conductivity of sand associated with bacterial growth and biofilm formation under a highly saline condition of approximately 1% salinity and approximately 2 S/m pore water conductivity with an emphasis on relaxation behavior. A column test is performed, in which the model bacteria Shewanella oneidensis MR-1 are stimulated for cell growth and biofilm formation in a sand pack, whereas the complex conductivity is monitored from 0.01 Hz to 10 kHz. The test results indicate that the real conductivity increases in the early stage due to the microbial metabolites and the increased surface conduction with cell growth but soon begin to decrease because of the reduction of charge passages due to bioclogging. However, the imaginary conductivity significantly increases with time, and clear bell-shaped relaxation behaviors are observed with the peak frequency of 0.1–1 Hz, associated with the double-layer polarization of cells and electrically conductive pili and biofilms. The Cole-Cole relaxation model appears to capture such relaxation behaviors well, and the modeling results indicate gradual increases in normalized chargeability and decreases in relaxation time during bacterial growth and biofilm formation in the highly saline condition. Comparison with previous literature confirms that the high-salinity condition further increases the normalized chargeability, whereas it suppresses the phase shift and thus the imaginary conductivity. Our results suggest that the complex conductivity can effectively capture microbial biomass formation in sands under a highly saline condition.

58 GEOSCIENCES↗
DOE OSTI2026

Soil nitrogen mineralization rates, nutrient stocks, stable isotopes, and water volumetric measurements across terrestrial-aquatic interfaces from three wetlands at the Tanglewood Biological Station, Alabama

This dataset supports a broader study investigating wetland hydrologic and biogeochemical responses to inundation events. Soil samples were collected across four sampling events along terrestrial-aquatic gradients at three wetland sites located within the Tanglewood Biological Station in Alabama from April 2024 to June 2025. The contents in this data package include soil in-situ nitrogen mineralization rates (measurements of net nitrification, net ammonification, and net mineralization), nutrient stocks (total carbon, total nitrogen, and organic matter), stable isotopes (carbon and nitrogen), and water volumetric measurements (water-filled pore space). Water level data related to each wetland location can be found at https://data.ess-dive.lbl.gov/view/doi:10.15485/2530253 (Kirker et al., 2024), related water geochemistry data can be found at https://data.ess-dive.lbl.gov/datasets/doi:10.15485/3001967 (Forbes et al., 2025), and related surface water sediment chemistry data can be found at https://data.ess-dive.lbl.gov/datasets/doi:10.15485/3377325 (Molina Serpas et al., 2026). In addition to this readme, this data package also includes a file-level metadata (FLMD) file that describes each file and a data dictionary (DD) that describes all column/row headers and variable definitions. This dataset is comprised of (1) file-level metadata; (2) data dictionary; (3) field metadata and international generic sample numbers (IGSNs); (4) readme; (5) the field protocol; and (6) a subfolder with sample data. The sample data subfolder contains (1) net nitrification rate, (2) net ammonification rate, (3) areal net mineralization rate, (4) percent organic matter, (5) water-filled pore space, (6) total carbon content, (7) total nitrogen content, (8) stable carbon isotope (delta carbon-13), and (9) stable nitrogen isotope (delta nitrogen-15), and (10) methods codes. All files are .csv or .pdf.

13-C↗
DOE OSTI2025

From subsidies to stressors: Positively skewed ecological gradients alter biological responses to nutrients in streams

Abstract Subsidy–stress gradients offer a useful framework for understanding ecological responses to perturbation and may help inform ecological metrics in highly modified systems. Historic, region‐wide shifts from bottomland hardwood forest to row crop agriculture can cause positively skewed impact gradients in alluvial plain ecoregions, resulting in tolerant organisms that typically exhibit a subsidy response (increased abundance in response to environmental stressors) shifting to a stress response (declining abundance at higher concentrations). As a result, observed biological tolerance in modified ecosystems may differ from less modified regions, creating significant challenges for detecting biological responses to restoration efforts. Using the agriculturally dominated Mississippi Alluvial Plain (MAP) ecoregion in Mississippi, USA, as a case study, we tested the hypothesis that macroinvertebrate taxa that typically display a subsidy response to nutrient enrichment in less modified ecoregions (i.e., nutrient‐tolerance) shift to a stress response to increasing nutrients in highly modified watersheds with elevated baseline nutrient conditions (i.e., nutrient intolerance). The abundance and diversity of MAP‐specific intolerant taxa identified with threshold indicator taxa analysis were either unresponsive or exhibited a subsidy response to increasing nutrients in less modified ecoregions in Mississippi with less land alteration and lower nutrient concentrations, but declined at higher concentrations, providing evidence for a stress response to elevated nutrients in the MAP. Additionally, MAP‐specific tolerant and intolerant taxa richness responded to increased nutrients predictably and consistently across space and time within the MAP. However, in MAP streams, elevated specific conductance was predicted to dampen the response of tolerant and intolerant taxa richness to increasing nutrient concentrations, highlighting the importance of considering multistressor interactions when interpreting biological data. Lastly, we demonstrate the efficacy of this approach with sediment bacterial communities characterized with amplicon sequencing, which lack sufficient life history characteristics necessary for the development of multimetric indices. Both macroinvertebrate and bacterial communities responded similarly to increasing nutrient concentrations, suggesting DNA‐based approaches may provide an efficient biological assessment tool for monitoring water quality improvements in highly modified watersheds.

DeVilbiss, Stephen E. [U.S. Geological Survey Lowe↗
DOE OSTI2021

Development of a stoichiometric magnesium potassium phosphate cement (MKPC) for the immobilization of powdered minerals

Ordinary Portland Cement (OPC)-based materials are not systematically adapted for immobilizing industrial hazardous waste, e.g. for aluminium powder or plutonium waste sludge. In such case, Magnesium Potassium Phosphate Cements (MKPC) represent an interesting alternative. }The originality of this research is to develop a formulation of a MKPC paste for hazardous waste immobilization, which incorporates a maximum amount of such waste, preferably in powdered form. To this purpose, a stoichiometric MKPC paste is selected, and its properties are improved by powdered waste addition. }Firstly, the physico-chemical mechanisms generating expansion in stoichiometric MKPC paste are analyzed. Swelling is attributed to a pH gradient in the paste, due to the progressive sedimentation of MgO particles in the fresh mix. }Secondly, over-stoichiometric MgO is replaced by varying amounts of minerals simulating the waste, of different mineralogy and granulometry, in order to achieve sufficient workability and no swelling. An optimal formulation is proposed, which incorporates powdered fly ash at a fine-to-cement mass ratio (F/C) of 1. Its mechanical performance and endogenous dimensional changes are comparable to typical over-stoichiometric pastes, and they stabilize between 7 and 28 days.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Engineering quorum-sensing circuits in Synechococcus elongatus PCC 7942 towards self-inducible systems

Despite significant potential for cyanobacteria as sustainable bioproduction chases, there are limited examples of scaled cyanobacterial bioproduction. In part, this is because most cyanobacterial species are poorly adapted to bioreactor cultivation conditions and lack features that facilitate biomass growth and harvesting at scale. We explored quorum sensing (QS) pathways derived from heterotrophic microbes as a method for autoinduction of gene expression circuits coordinated to population density in cyanobacteria. Here, we integrated genetic modules designed to produce and detect the diffusible QS signal, acyl-homoserine lactones (AHLs), in the cyanobacterial model, Synechococcus elongatus PCC 7942 (S. elongatus). We demonstrate that S. elongatus heterologously produces sufficient AHL signals to activate gene expression in a dose-dependent and population density-responsive manner. A hybrid combination of AHL synthesis enzyme from Vibrio fischeri (Lux system) with the transcription factor receiver from Pseudomonas aeruginosa (Las system) provides an ideal activation ratio and mitigates toxicity observed with some AHL systems. As a proof of concept, we coupled the QS pathway to the expression of a cell division inhibitory gene, cdv3, facilitating late-phase cell elongation, cell sedimentation, and improved biomass recovery. Our findings provide a foundation for the development of auto-induction systems leverageable to improve cyanobacterial biotechnology applications.

Acyl homoserine lactones (AHL)↗
DOE OSTI2020

Large-Scale Molecular Dynamics Simulation of the Dehydration of a Suspension of Smectite Clay Nanoparticles

Fine-grained sediments and sedimentary rocks play important roles in a variety of modern energy technologies from petroleum geology to geological carbon sequestration and radioactive waste management. However, despite their utility and ubiquity, many of their properties remain poorly understood. In particular, the ability to predict the permeability and mechanics of these media remains a persistent fundamental challenge in the geosciences. In the present work, we show how large-scale classical molecular dynamics (MD) simulations can help interpret the properties of fine-grained sedimentary material. All-atom simulations containing 30 discrete clay particles are utilized to understand the evolution of a clay nanoparticle suspension during its progressive dehydration. Microstructural (pore size distribution, tortuosity, anisotropy), thermodynamic (enthalpy and free energy of hydration, anion exclusion), mechanical (total suction), and transport properties (diffusion coefficient tensors of water and sodium) are calculated and compared to the experiment. Overall, our results provide new insight into the coupled chemistry, mechanics, and transport properties of disordered nanoparticle assemblages and shed light upon the important role of water films in controlling these properties.

02 PETROLEUM↗