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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 793 records · Page 44
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Terrain-Relative Navigation with Neuro-Inspired Elevation Encoding

Terrain-relative navigation (TRN) encompasses a wide variety of algorithms that perform localization with respect to the terrain below a flying vehicle. In traditional approaches, measurements of the terrain are matched to a map carried onboard. This work presents a terrain-relative navigation filter with a position measurement inspired by neural activity associated with positioning in nature. Here, the filter is shown to produce accurate position measurements that outperform popular optimization and template matching methods given poor prior knowledge of the position. The proposed method is also better-suited to distributed implementation than optimization-based methods.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2021

Encoding Frequency Constraints in Preventive Unit Commitment Using Deep Learning With Region-of-Interest Active Sampling

With the increasing penetration of renewable energy, frequency response and its security are of significant concerns for reliable power system operations. Frequency-constrained unit commitment (FCUC) is proposed to address this challenge. Despite existing efforts in modeling frequency characteristics in unit commitment (UC), current strategies can only handle oversimplified low-order frequency response models and do not consider wide-range operating conditions. This paper presents a generic data-driven framework for FCUC under high renewable penetration. Here, deep neural networks (DNNs) are trained to predict the frequency response using real data or high-fidelity simulation data. Next, the DNN is reformulated as a set of mixed-integer linear constraints to be incorporated into the ordinary UC formulation. In the data generation phase, all possible power injections are considered, and a region-of-interest active sampling is proposed to include power injection samples with frequency nadirs closer to the UFLC threshold, which enhances the accuracy of frequency constraints in FCUC. The proposed FCUC is investigated on the IEEE 39-bus system. Then, a full-order dynamic model simulation using PSS/E verifies the effectiveness of FCUC in frequency-secure generator commitments.

42 ENGINEERING↗
DOE OSTI2016

The function of the PduJ microcompartment shell protein is determined by the genomic position of its encoding gene

Bacterial microcompartments (MCPs) are complex organelles that consist of metabolic enzymes encapsulated within a protein shell. Here, we investigate the function of the PduJ MCP shell protein. PduJ is 80% identical in amino acid sequence to PduA and both are major shell proteins of the 1,2-propanediol (1,2-PD) utilization (Pdu) MCP of Salmonella . Prior studies showed that PduA mediates the transport of 1,2-PD (the substrate) into the Pdu MCP. Surprisingly, however, results presented here establish that PduJ has no role 1,2-PD transport. The crystal structure revealed that PduJ was nearly identical to that of PduA and, hence, offered no explanation for their differential functions. Interestingly, however, when a pduJ gene was placed at the pduA chromosomal locus, the PduJ protein acquired a new function, the ability to mediate 1,2-PD transport into the Pdu MCP. To our knowledge, these are the first studies to show that that gene location can determine the function of a MCP shell protein. We propose that gene location dictates protein-protein interactions essential to the function of the MCP shell.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

A genetically encoded biosensor reveals spatiotemporal variation in cellular phosphate content in Brachypodium distachyon mycorrhizal roots

Arbuscular mycorrhizal (AM) symbiosis is accompanied by alterations to root cell metabolism and physiology, and to the pathways of orthophosphate (Pi) entry into the root, which increase with Pi delivery to cortical cells via arbuscules. How AM symbiosis influences the Pi content and Pi response dynamics of cells in the root cortex and epidermis is unknown. Using fluorescence resonance energy transfer (FRET)-based Pi biosensors, here we mapped the relative cytosolic and plastidic Pi content of Brachypodium distachyon mycorrhizal root cells, analyzed responses to extracellular Pi and traced extraradical hyphae-mediated Pi transfer to colonized cells. Colonized cortical cells had a higher cytosolic Pi content relative to noncolonized cortical and epidermal cells, while plastidic Pi content was highest in cells at the infection front. Pi application to the entire mycorrhizal root resulted in transient changes in cytosolic Pi that differed in direction and magnitude depending on cell type and arbuscule status; cells with mature arbuscules showed a substantial transient increase in cytosolic Pi while those with collapsed arbuscules showed a decrease. Directed Pi application to extraradical hyphae resulted in measurable changes in cytosolic Pi of colonized cells 18 h after application. Our experiments reveal that cells within a mycorrhizal root vary in Pi content and Pi response dynamics.

32Pi tracing↗
DOE OSTI2024

The expression of genes encoding novel Sesame oleosin variants facilitates enhanced triacylglycerol accumulation in Arabidopsis leaves and seeds

Summary Triacylglycerols (TAG), accumulate within lipid droplets (LD), predominantly surrounded by OLEOSINs (OLE), that protect TAG from hydrolysis. We tested the hypothesis that identifying and removing degradation signals from OLE would promote its abundance, preventing TAG degradation and enhancing TAG accumulation. We tested whether mutating potential ubiquitin‐conjugation sites in a previously reported improved Sesamum indicum OLE ( SiO ) variant, o3‐3 Cys‐OLE ( SiCO herein), would stabilize it and increase its lipogenic potential. SiCOv1 was created by replacing all five lysines in SiCO with arginines. Separately, six cysteine residues within SiCO were deleted to create SiCOv2. SiCOv1 and SiCOv2 mutations were combined to create SiCOv3. Transient expression of SiCOv3 in Nicotiana benthamiana increased TAG by two‐fold relative to SiCO. Constitutive expression of SiCOv3 or SiCOv5 , containing the five predominant TAG‐increasing mutations from SiCOv3 , in Arabidopsis along with mouse DGAT2 ( mD ) increased TAG accumulation by 54% in leaves and 13% in seeds compared with control lines coexpressing SiCO and mD. Lipid synthesis rates increased, consistent with an increase in lipid sink strength that sequesters newly synthesized TAG, thereby relieving the constitutive BADC‐dependent inhibition of ACCase reported for WT Arabidopsis. These OLE variants represent novel factors for potentially increasing TAG accumulation in a variety of oil crops.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Clinical manifestation of hemophilia A in the absence of mutations in the F8 gene that encodes FVIII: role of microRNAs

BACKGROUND Hemophilia A (HA) is associated with mutations in the F8 gene that expresses factor VIII (FVIII). Unexpectedly, HA also manifests in a small subset of individuals with no mutations (exonic or intronic) in their F8 gene. MicroRNAs (miRNAs) cause translational interference, affecting protein quality and stoichiometry. Here, by analyzing miRNAs of two patients from this subset, we evaluated miRNA‐based FVIII suppression as a testable hypothesis to explain FVIII deficiency in patients with HA with no F8 gene mutations. STUDY DESIGN AND METHODS To test the hypothesis, miRNA sequencing from two patients with mild and moderate HA with no mutations in their F8 gene, followed by experimental verification, was used to identify a group of upregulated miRNAs in patients with HA compared to normal controls; with binding sites in the 3′ untranslated region (UTR) of F8 messenger RNA (mRNA), a prerequisite for miRNA‐based gene regulation. From this pool, miR‐374b‐5p and miR‐30c‐5p, known to be expressed in human liver, where FVIII is expressed, were subjected to extensive characterization. RESULTS In two cell lines that constitutively express FVIII, we demonstrated that overexpression of miR‐374b or miR‐30c decreased FVIII expression, while an miR‐30c inhibitor partially restored FVIII expression. CONCLUSION These data support a role for microRNAs in fine‐tuning F8 gene regulation. Based on our findings, our current model suggests that in HA cases where the F8 gene is normal and is predicted to express normal levels of FVIII, F8 mRNA 3′ UTR targeting miRNAs may be responsible for a FVIII‐deficiency phenotype clinically manifesting as HA.

Jankowska, Katarzyna I.↗
DOE OSTI2014

Identification and environmental distribution of dcpA encoding the 1,2-dichloropropane-to-propene reductive dehalogenase in organohalide-respiring Chloroflexi

Dehalococcoides mccartyi (Dhc) strains KS and RC grow with 1,2-dichloropropane (1,2-D) as an electron acceptor in enrichment cultures derived from hydrocarbon-contaminated and pristine river sediments, respectively. Transcription, expression, enzymatic and PCR analyses implicated the reductive dehalogenase gene dcpA in 1,2-D dichloroelimination to propene and inorganic chloride. Quantitative real-time PCR (qPCR) analyses demonstrated Dhc cell increase during growth with 1,2-D and suggested that both Dhc strains carried a single dcpA gene copy per genome. Dhc strain RC and strain KS produced 1.8 0.1 x 107 and 1.4 0.5 x 107 cells per mole of propene formed, respectively. The dcpA gene was identified in 1,2-D-to-propene-dechlorinating microcosms established with sediment samples collected from different geographical locations in Europe and North and South America. Clone library analysis revealed two distinct dcpA phylogenetic clusters, both of which the dcpA gene-targeted qPCR assay captured, suggesting the qPCR assay is useful for site assessment and bioremediation monitoring at 1,2-D-contaminated sites.

Padilla-Crespo, Elizabeth↗