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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 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Plasmon-Assisted Direct Interfacial Charge Transfer Enables Molecular Photodissociation on Metal Surfaces

Plasmonic photocatalysis is promising for driving reactions out of equilibrium, leading to enhanced rates and selectivity, but the energy and charge transfer mechanism at the interface remains to be explored. Here, we revisit visible-light plasmon-assisted photodissociation of dimethyl disulfide molecules (S–S bond cleavage) over single-crystalline silver and copper surfaces, using density functional theory calculations and the delta self-consistent field method. We investigate different excitation mechanisms and show that the direct intramolecular excitations, as suggested earlier to explain the experimental findings, cannot address the observed catalytic bond activation. Instead, the calculated excitations mediated by the metal Fermi level agree well with the threshold energy and maximum-yield energy in experiments and suggest that the reaction follows a direct interfacial charge transfer mechanism. Furthermore, we show that the excitation energy and the charge transfer can be modulated by introducing excess charges in the systems. Here, this study thus provides a fundamental understanding of interfacial charge transfer for driving plasmonic photocatalysis.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

The connectome of the adult Drosophila mushroom body provides insights into function

Making inferences about the computations performed by neuronal circuits from synapse-level connectivity maps is an emerging opportunity in neuroscience. The mushroom body (MB) is well positioned for developing and testing such an approach due to its conserved neuronal architecture, recently completed dense connectome, and extensive prior experimental studies of its roles in learning, memory, and activity regulation. Here, we identify new components of the MB circuit in Drosophila , including extensive visual input and MB output neurons (MBONs) with direct connections to descending neurons. We find unexpected structure in sensory inputs, in the transfer of information about different sensory modalities to MBONs, and in the modulation of that transfer by dopaminergic neurons (DANs). We provide insights into the circuitry used to integrate MB outputs, connectivity between the MB and the central complex and inputs to DANs, including feedback from MBONs. Our results provide a foundation for further theoretical and experimental work.

Li, Feng↗
DOE OSTI2014

The RNA recognition motif domains of RBM5 are required for RNA binding and cancer cell proliferation inhibition

Highlights: • RNA recognition motif domains of RBM5 are essential for cell proliferation inhibition. • RNA recognition motif domains of RBM5 are essential for apoptosis induction. • RNA recognition motif domains of RBM5 are essential for RNA binding. • RNA recognition motif domains of RBM5 are essential for caspase-2 alternative splicing. - Abstract: RBM5 is a known putative tumor suppressor gene that has been shown to function in cell growth inhibition by modulating apoptosis. RBM5 also plays a critical role in alternative splicing as an RNA binding protein. However, it is still unclear which domains of RBM5 are required for RNA binding and related functional activities. We hypothesized the two putative RNA recognition motif (RRM) domains of RBM5 spanning from amino acids 98–178 and 231–315 are essential for RBM5-mediated cell growth inhibition, apoptosis regulation, and RNA binding. To investigate this hypothesis, we evaluated the activities of the wide-type and mutant RBM5 gene transfer in low-RBM5 expressing A549 cells. We found that, unlike wild-type RBM5 (RBM5-wt), a RBM5 mutant lacking the two RRM domains (RBM5-ΔRRM), is unable to bind RNA, has compromised caspase-2 alternative splicing activity, lacks cell proliferation inhibition and apoptosis induction function in A549 cells. These data provide direct evidence that the two RRM domains of RBM5 are required for RNA binding and the RNA binding activity of RBM5 contributes to its function on apoptosis induction and cell growth inhibition.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2022

Emulation Framework for Distributed Large-Scale Systems Integration

Recent trends in systems engineering include integration of very large-scale systems, which entails significant challenges when they are geographically dispersed. In these scenarios, intelligent integration of distributed large-scale systems requires significant coordination among hardware elements as well as all software components. The approach of integrated systems (both computing platform and experimental equipment) for end-to-end orchestration is called federation. Virtual frameworks can aid in the testing, assessment, and implementation of a functional system of interconnected resources. We present an emulation framework that replicates the software environments of multi-site federations of computing systems and instruments. Our emulation framework allows systems engineers to reduce developmentcost and avoid disruptions to production infrastructure. Our framework was effectively used to develop and test software modules for various tasks including container orchestration and instrument access. For performance assessment, however, the emulated framework is severely limited in providing accurate network and IO measurements at 10 Gbps and higher data rates. The data transfer performance profiles estimated using these emulated measurements are usually inaccurate for high bandwidth and high latency connections, since emulation does not accurately reflect the critical network transport dynamics.We utilize measurements from a physical testbed with hardware network emulators to obtain data transfer profiles that closely match the expected profiles for the emulated federations. We show the effectiveness of our approach by an illustrative example of integrated (federated) multi-site ultra large-scale systems that are connected via high speed wide area networks.

Imam, Neena↗
DOE OSTI2021

Pseudo-atomic orbital behavior in graphene nanoribbons with four-membered rings

The incorporation of nonhexagonal rings into graphene nanoribbons (GNRs) is an effective strategy for engineering localized electronic states, bandgaps, and magnetic properties. Here, we demonstrate the successful synthesis of nanoribbons having four-membered ring (cyclobutadienoid) linkages by using an on-surface synthesis approach involving direct contact transfer of coronene-type precursors followed by thermally assisted [2 + 2] cycloaddition. The resulting coronene-cyclobutadienoid nanoribbons feature a narrow 600-meV bandgap and novel electronic frontier states that can be interpreted as linear chains of effective p x and p y pseudo-atomic orbitals. We show that these states give rise to exceptional physical properties, such as a rigid indirect energy gap. This provides a previously unexplored strategy for constructing narrow gap GNRs via modification of precursor molecules whose function is to modulate the coupling between adjacent four-membered ring states.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Acquisition and Implementation of a Comprehensive Environmental Permits Linking Tool at Savannah River Site - 20234

Historically, Savannah River Nuclear Solutions LLC (SRNS) tracked environmental regulatory commitments and the requirements from hundreds of permits at the Savannah River Site (SRS) using several separate methods, making integrated compliance assurance cumbersome and labor-intensive. When SRNS experienced an increase in environmental issues in 2017, SRNS management and U.S. Department of Energy - Savannah River (DOE-SR) management decided a single, proactive approach was needed to capture environmental permit information (including regulations, Consent Orders, DOE Orders, and any other state or federally issued statement of requirements), track the tasks necessary to ensure compliance with these requirements, and thereby mitigate the risk of noncompliance. SRNS developed a list of mandatory objectives that the tool must meet to function as a Comprehensive Environmental Permits Linking Tool (CEPLT). A key requirement was the ability to map Site permits to their governed locations and display the associated requirements at the compliance point (e.g., outfall, stack, waste unit, etc.). Several options included modifying existing onsite resources, building a custom onsite solution, purchasing an off-the-shelf solution, and contracting an offsite developer to build a custom solution. SRNS concluded an off-the-shelf solution with configuration and customization options would provide the flexibility to fit the unique needs of Savannah River Site (SRS) while taking advantage of industry-tested software and providing a reduced deployment timeline. SRNS chose Gensuite{sup R} a, a cloud-based solution that offers numerous a la carte applications in the environmental, health, and safety arenas, as the best candidate. SRNS selected three (3) integrated applications (Compliance Calendar, Permit Manager, and Mapper) to function as the CEPLT. The Compliance Calendar module allows for creation and tracking of regulatory commitment tasks assigned to responsible environmental professionals. Permit Manager organizes permits and other requirement documents, linking the commitments in each to Compliance Calendar tasks and/or implementing procedures. Mapper provides GIS capability for mapping the data from the other two modules to their physical onsite locations. The CEPLT was configured to allow for other SRS Site Tenants to eventually utilize the applications. Additionally, DOE-SR uses the CEPLT to provide an overview of contractor environmental compliance activities and to organize DOE-specific documents and tasks. The CEPLT fulfilled the requirement of meeting current compliance needs as well as providing the ability to grow as new organizations are incorporated and functionality is expanded. SRNS now uses the CEPLT to more effectively manage permit requirements, improve knowledge transfer, and increase the Site's overall protection of the environment, the Site worker, and the public. Possible future uses of the system include integration of mobile applications for timely communication of potential non-compliant conditions and DOE complex-wide deployment allowing for enhanced DOE site and Head Quarters oversight. Implementation of CEPLT will result in cost savings, both in terms of dollars and man-hours. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2014

Periodic and stochastic thermal modulation of protein folding kinetics

Chemical reactions are usually observed either by relaxation of a bulk sample after applying a sudden external perturbation, or by intrinsic fluctuations of a few molecules. Here we show that the two ideas can be combined to measure protein folding kinetics, either by periodic thermal modulation, or by creating artificial thermal noise that greatly exceeds natural thermal fluctuations. We study the folding reaction of the enzyme phosphoglycerate kinase driven by periodic temperature waveforms. As the temperature waveform unfolds and refolds the protein, its fluorescence color changes due to FRET (Förster resonant Energy Transfer) of two donor/acceptor fluorophores labeling the protein. We adapt a simple model of periodically driven kinetics that nicely fits the data at all temperatures and driving frequencies: The phase shifts of the periodic donor and acceptor fluorescence signals as a function of driving frequency reveal reaction rates. We also drive the reaction with stochastic temperature waveforms that produce thermal fluctuations much greater than natural fluctuations in the bulk. Such artificial thermal noise allows the recovery of weak underlying signals due to protein folding kinetics. This opens up the possibility for future detection of a stochastic resonance for protein folding subject to noise with controllable amplitude.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Phylogenomic discovery and engineering of nitrogen fixation into the bioenergy woody crop poplar

Biological nitrogen fixation (BNF) is a key process enabling plants in specific lineages to convert atmospheric dinitrogen (N₂) into bioavailable ammonia through symbioses with diazotrophic microbes. Expanding this capability beyond native nitrogen-fixing clades into non-nodulating crops would reduce synthetic fertilizer use, lowering energy inputs and environmental impacts in agriculture. Supported by DOE Funding Award DE-SC0018247, the NitFix project advanced foundational knowledge required to engineer root-nodule symbioses in new host species. The team generated the most comprehensive phylogenomic analysis to date of all known nodulating lineages, resolving the evolutionary history of nitrogen-fixing symbiosis and identifying core gene suites retained across nodulating taxa. Through multimodal genomics, transcriptomics, and functional analyses in Medicago truncatula and related species, the project mapped regulatory networks underlying nodule organogenesis, bacterial infection, and nitrogen-fixation efficiency. Key discoveries include the identification of conserved signaling modules for rhizobial recognition, transcription factors controlling nodule differentiation, and metabolic pathways integrating fixed nitrogen into plant growth. The project also developed enabling tools—including optimized transformation pipelines, gene-editing workflows, and imaging-based phenotyping—to accelerate engineering efforts in emerging models. Together, these results refine the mechanistic framework of symbiotic nitrogen fixation and highlight transferable components essential for rewiring these traits into non-nodulating crops.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2014

Spin transfer torque generated magnetic droplet solitons (invited)

We present recent experimental and numerical advancements in the understanding of spin transfer torque generated magnetic droplet solitons. The experimental work focuses on nano-contact spin torque oscillators (NC-STOs) based on orthogonal (pseudo) spin valves where the Co fixed layer has an easy-plane anisotropy, and the [Co/Ni] free layer has a strong perpendicular magnetic anisotropy. The NC-STO resistance and microwave signal generation are measured simultaneously as a function of drive current and applied perpendicular magnetic field. Both exhibit dramatic transitions at a certain current dependent critical field value, where the microwave frequency drops 10 GHz, modulation sidebands appear, and the resistance exhibits a jump, while the magnetoresistance changes sign. We interpret these observations as the nucleation of a magnetic droplet soliton with a large fraction of its magnetization processing with an angle greater than 90°, i.e., around a direction opposite that of the applied field. This interpretation is corroborated by numerical simulations. When the field is further increased, we find that the droplet eventually collapses under the pressure from the Zeeman energy.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Bacterial microcompartments as metabolic modules for plant synthetic biology

Summary Bacterial microcompartments ( BMC s) are megadalton‐sized protein assemblies that enclose segments of metabolic pathways within cells. They increase the catalytic efficiency of the encapsulated enzymes while sequestering volatile or toxic intermediates from the bulk cytosol. The first BMC s discovered were the carboxysomes of cyanobacteria. Carboxysomes compartmentalize the enzyme ribulose‐1,5‐bisphosphate carboxylase/oxygenase (RuBis CO ) with carbonic anhydrase. They enhance the carboxylase activity of RuBis CO by increasing the local concentration of CO 2 in the vicinity of the enzyme's active site. As a metabolic module for carbon fixation, carboxysomes could be transferred to eukaryotic organisms (e.g. plants) to increase photosynthetic efficiency. Within the scope of synthetic biology, carboxysomes and other BMC s hold even greater potential when considered a source of building blocks for the development of nanoreactors or three‐dimensional scaffolds to increase the efficiency of either native or heterologously expressed enzymes. The carboxysome serves as an ideal model system for testing approaches to engineering BMC s because their expression in cyanobacteria provides a sensitive screen for form (appearance of polyhedral bodies) and function (ability to grow on air). We recount recent progress in the re‐engineering of the carboxysome shell and core to offer a conceptual framework for the development of BMC ‐based architectures for applications in plant synthetic biology.

Gonzalez‐Esquer, C. Raul↗
DOE OSTI2025

Tuning the Lifetimes of Photoinduced Deligation in a Metal–Organic Framework via Linker Functionalization

Recently photoinduced dynamic ligation in a metal–organic frameworks (MOFs) was reported, where a long-lived charge-transfer excited state (ca. 30 μs) featuring partial dissociation between the carboxylate linker and metal-based node was probed by time-resolved infrared (TRIR) spectroscopy. The study offers a new mechanistic perspective to evaluate the potential contribution from the excited state molecular configuration to the performance of MOF photocatalysts. In this work, by employing MIL-101(Fe) as the study platform, we have further explored the influence of intramolecular interactions on the stability of relevant excited states and demonstrated the effective tuning of their lifetimes through the incorporation of different functional groups into the system. The correlations between the varied excited state lifetimes and coordination configurations with specific functional groups (−NH 2 or −NO 2 ) was inferred from the analyses of infrared spectroscopic data and theoretical calculations, revealing the essential role of the intramolecular interactions (i.e., between the added functional groups and the carboxylate group) in the modulation of system energetics. Overall, the work presents a pathway to tune the excited state dynamics and expands the knowledge regarding the photoinduced dynamic ligation in carboxylate-based MOFs.

excited states↗
DOE OSTI2024

Manipulating symmetry-breaking charge separation employing molecular recognition

The exploration of symmetry-breaking charge separation (SB-CS) is imperative when designing functional light-harvesting materials. Past explorations, however, have been confined to covalent systems, more often than not requiring complicated/demanding syntheses and facing inconvenient regulation of charge transfer processes. Here, in this work, we present a concept that regulates the efficiency of SB-CS through molecular recognition utilizing a pyridinium-based cyclophane as a host. This host undergoes photo-driven excited-state SB-CS. By employing different guests with distinct frontier molecular orbital energy levels, we have achieved comprehensive control of electron transfer pathways in the cyclophane, modulating between accelerated (>10-fold) intramolecular SB-CS involving superexchange and direct intermolecular electron transfer between the host and guest. The improvement in SB-CS efficiency results in catalytic activity for the photo-oxidation of a sulfur-mustard simulant. This research offers an opportunity for tuning SB-CS by utilizing molecular recognition, which holds the potential for achieving precise regulation without complicated organic syntheses.

charge transfer↗
DOE OSTI2018

Remodeling neuronal ER–PM junctions is a conserved nonconducting function of Kv2 plasma membrane ion channels

The endoplasmic reticulum (ER) and plasma membrane (PM) form junctions crucial to ion and lipid signaling and homeostasis. The Kv2.1 ion channel is localized at ER–PM junctions in brain neurons and is unique among PM proteins in its ability to remodel these specialized membrane contact sites. Here, we show that this function is conserved between Kv2.1 and Kv2.2, which differ in their biophysical properties, modulation, and cellular expression. Kv2.2 ER–PM junctions are present at sites deficient in the actin cytoskeleton, and disruption of the actin cytoskeleton affects their spatial organization. Kv2.2-containing ER–PM junctions overlap with those formed by canonical ER–PM tethers. The ability of Kv2 channels to remodel ER–PM junctions is unchanged by point mutations that eliminate their ion conduction but eliminated by point mutations within the Kv2-specific proximal restriction and clustering (PRC) domain that do not impact their ion channel function. The highly conserved PRC domain is sufficient to transfer the ER–PM junction–remodeling function to another PM protein. Last, brain neurons in Kv2 double-knockout mice have altered ER–PM junctions. Together, these findings demonstrate a conserved in vivo function for Kv2 family members in remodeling neuronal ER–PM junctions that is distinct from their canonical role as ion-conducting channels shaping neuronal excitability.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

The allosteric mechanism of substrate-specific transport in SLC6 is mediated by a volumetric sensor

Neurotransmitter:sodium symporters (NSSs) in the SLC6 family terminate neurotransmission by coupling the thermodynamically favorable transport of ions to the thermodynamically unfavorable transport of neurotransmitter back into presynaptic neurons. Results from many structural, functional, and computational studies on LeuT, a bacterial NSS homolog, have provided critical insight into the mechanism of sodium-coupled transport, but the mechanism underlying substrate-specific transport rates is still not understood. We present a combination of molecular dynamics simulations, single-molecule fluorescence resonance energy transfer (smFRET) imaging, and measurements of Na + binding and substrate transport that reveals an allosteric substrate specificity mechanism. In this mechanism, residues F259 and I359 in the substrate binding pocket couple the binding of substrate to Na + release from the Na2 site by allosterically modulating the stability of a partially open, inward-facing state. We propose a model for transport selectivity in which residues F259 and I359 act as a volumetric sensor that inhibits the transport of bulky amino acids.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2013

An Overview on the Marine Neurotoxin, Saxitoxin: Genetics, Molecular Targets, Methods of Detection and Ecological Functions

Marine neurotoxins are natural products produced by phytoplankton and select species of invertebrates and fish. These compounds interact with voltage-gated sodium, potassium and calcium channels and modulate the flux of these ions into various cell types. This review provides a summary of marine neurotoxins, including their structures, molecular targets and pharmacologies. Saxitoxin and its derivatives, collectively referred to as paralytic shellfish toxins (PSTs), are unique among neurotoxins in that they are found in both marine and freshwater environments by organisms inhabiting two kingdoms of life. Prokaryotic cyanobacteria are responsible for PST production in freshwater systems, while eukaryotic dinoflagellates are the main producers in marine waters. Bioaccumulation by filter-feeding bivalves and fish and subsequent transfer through the food web results in the potentially fatal human illnesses, paralytic shellfish poisoning and saxitoxin pufferfish poisoning. These illnesses are a result of saxitoxin’s ability to bind to the voltage-gated sodium channel, blocking the passage of nerve impulses and leading to death via respiratory paralysis. Recent advances in saxitoxin research are discussed, including the molecular biology of toxin synthesis, new protein targets, association with metal-binding motifs and methods of detection. The eco-evolutionary role(s) PSTs may serve for phytoplankton species that produce them are also discussed.

paralytic shellfish toxin↗
DOE OSTI2026

Operation-Induced BiVO4 Surface Reconstruction Modulates Photoelectrochemical Glycerol Photooxidation Stability and Activity

Abstract Operation-induced surface reconstruction of photoelectrodes is underexplored as a path to control stability and performance. We show how adaptive junctions form via surface reconstruction of BiVO4 during glycerol photooxidation and how these surfaces affect electrolyte-dependent kinetics and durability. Preferential V dissolution in both acidic and alkaline media forms a Bi-rich layer. In situ measurements through a dual-working-electrode platform quantify the changes in photovoltage and charge-transfer resistance derived from adaptive junction formation, while enabling quantitative separation of the driving forces for charge separation and interfacial catalysis. The reconstructed surface in acidic media improves hole-transfer kinetics, functions as a glycerol-oxidation catalyst, and imparts photostability. Surface reconstruction in alkaline media exhibits the opposite behavior, impeding hole injection. This instability is mitigated by trace Ni2+ ions, which drive in situ surface activation without cocatalyst pre-deposition. This study shows the significance of surface reconstruction in the design of durable photoelectrodes for applications targeting organic electro-oxidation.

Yang, Jin Wook↗
DOE OSTI2026

Nanoarchitectonic Semiconductor–Bio Hybrid Systems with Enhanced Charge Transfer for Hydrogen Peroxide Production

Nanoarchitectonics offers a systematic approach to creating an artificial framework by integrating different multiscale components such as semiconductor lattices and biological substances. However, most nanoarchitectonic abiotic-biotic hybrid systems have intrinsic limitations in imparting nonequilibrium biological features into semiconductor lattices at the nanoscale. Here, in this study, we report a new nanoarchitectonic system integrating bismuth oxychloride (BiOCl) nanosheets with purple membrane (PM) patches. PM is an archaeal subcellular fraction capable of unidirectionally transferring photogenerated charge carriers to its surroundings at the nanoscale independent of archaeal metabolism and retaining this dynamic functionality after isolation from living archaea. Microscopy, spectroscopy, electrochemical, and synchrotron X-ray scattering analyses verify that the nanoarchitectonic hybridization between BiOCl and PM generates a vertical heterostructure, thereby enhancing photogenerated charge-carrier dynamics and enabling the associated photocatalytic capacity. The resulting PM-BiOCl hybrid nanosheets efficiently convert dioxygen into hydrogen peroxide through a two-electron and two-proton transfer process under ambient conditions while simultaneously converting ethylene glycol into value-added chemicals. This study presents a nanoarchitectonic approach that leverages the photogenerated charge-carrier dynamics of the archaeal subcellular fractions to modulate the optoelectronic and catalytic capacity limitations of semiconductors.

catalysis↗