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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 1,045 records · Page 58
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Decellularized ECM derived from normal bone involved in the viability and chemo-sensitivity in multiple myeloma cells

Multiple myeloma (MM) is an incurable plasma cell malignancy. The progression of MM is closely related to the bone microenvironment. Bone matrix proteins are remodeled and manipulated to govern cancer growth during the process of MM. However the role of normal bone extracellular matrix in MM is still unclear. In this study the decellularized extracellular matrix derived from normal SD rats’ skulls (N-dECM) was prepared by decellularization technology. The CCK 8 assay and the dead-live cell kit assay were used to determine the viability of MM cells and the sensitivity to bortezomib. The Realtime PCR and Western blot assay were used to assay the mRNA and protein related to MM. Under the treatment of N-dECM, we found that the viability of MM cells was inhibited and the sensitivity of MM cells to bortezomib was increased. Additionally, the expression levels of APRIL and TACI, which participated in the progression of MM, were significantly decreased in MM cells. It suggested that N-dECM might inhibit the development of MM via APRIL-TACI axis, and our study may provide a novel and potential biomaterial for MM therapy.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2024

Multiple aspects maintenance ontology-based intelligent maintenance optimization framework for safety-critical systems

Abstract Maintenance optimization is a process for improving the efficiency of maintenance strategies and activities, considering various aspects of the target system and components, such as the probabilities of system failures and the cost of repair and replacement of a failed component. The improvement of maintenance optimization algorithms generally requires information from various data sources. For example, it may require the system risk information derived from risk analysis tools or the residual lifetime of a component from fault prognosis tools. The requirements of data acquisition (DAQ) and aggregation pose new challenges for maintenance management systems (MMSs) that implement and use these maintenance optimization algorithms. This paper proposes a multiple aspects maintenance ontology-based framework to facilitate DAQ from MMSs, online monitoring systems, fault detection and discrimination tools, risk assessment tools, decision-making tools, and component identification tools, and accelerate the implementation and verification of contemporary maintenance optimization models and algorithms. The proposed framework consists of a multi-aspect maintenance ontology with critical information for maintenance optimization and application interfaces for collecting information from various data sources, such as fault prognosis tools, online monitoring tools, risk assessment tools, and decision-making algorithms. In addition, this paper proposes a heuristic method for integrating concepts and properties from other existing ontologies into the proposed framework when the existing ontology is not fully compatible with the ontology under construction. Finally, the paper verifies the proposed ontology framework using a feedwater system designed for nuclear power plants with valves and filters as the components under maintenance.

Diao, Xiaoxu (ORCID:0000000346726352)↗
DOE OSTI2024

Deciphering Photoinduced Catalytic Reaction Mechanisms in Natural and Artificial Photosynthetic Systems on Multiple Temporal and Spatial Scales Using X-ray Probes

Utilization of renewable energies for catalytically generating value-added chemicals is highly desirable in this era of rising energy demands and climate change impacts. Artificial photosynthetic systems or photocatalysts utilize light to convert abundant CO 2 , H 2 O, and O 2 to fuels, such as carbohydrates and hydrogen, thus converting light energy to storable chemical resources. Here, the emergence of intense X-ray pulses from synchrotrons, ultrafast X-ray pulses from X-ray free electron lasers, and table-top laser-driven sources over the past decades opens new frontiers in deciphering photoinduced catalytic reaction mechanisms on the multiple temporal and spatial scales. Operando X-ray spectroscopic methods offer a new set of electronic transitions in probing the oxidation states, coordinating geometry, and spin states of the metal catalytic center and photosensitizers with unprecedented energy and time resolution. Operando X-ray scattering methods enable previously elusive reaction steps to be characterized on different length scales and time scales. The methodological progress and their application examples collected in this review will offer a glimpse into the accomplishments and current state in deciphering reaction mechanisms for both natural and synthetic systems. Looking forward, there are still many challenges and opportunities at the frontier of catalytic research that will require further advancement of the characterization techniques.

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

Multiple N–H and C–H Hydrogen Atom Abstractions Through Coordination-Induced Bond Weakening at Fe-Amine Complexes

We report the use of the reported Fe-phthalocyanine complex, PcFe (1; Pc = 1,4,8,11,15,18,22,25-octaethoxy-phthalocyanine), to generate PcFe–amine complexes 1-(NH 3 ) 2 , 1-(MeNH 2 ) 2 , and 1-(Me 2 NH) 2 . Treatment of 1 or 1-(NH 3 ) 2 to an excess of the stable aryloxide radical, 2,4,6-tritert-butylphenoxyl radical ( t Bu ArO•), under NH 3 resulted in catalytic H atom abstraction (HAA) and C–N coupling to generate the product 4-amino-2,4,6-tritert-butylcyclohexa-2,5-dien-1-one (2) and t Bu ArOH. Exposing 1-(NH 3 ) 2 to an excess of the trityl (CPh 3 ) variant, 2,6-di-tert-butyl-4-tritylphenoxyl radical ( Tr ArO • ), under NH 3 did not lead to catalytic ammonia oxidation as previously reported in a related Ru-porphyrin complex. However, pronounced coordination-induced bond weakening of both α N–H and β C–H in the alkylamine congeners, 1-(MeNH 2 ) 2 and 1-(Me 2 NH) 2 , led to multiple HAA events yielding the unsaturated cyanide complex, 1-(MeNH 2 )(CN), and imine complex, 1-(MeN=CH 2 ) 2 , respectively. Subsequent C–N bond formation was also observed in the latter upon addition of a coordinating ligand. Detailed computational studies support an alternating mechanism involving sequential N–H and C–H HAA to generate these unsaturated products.

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

An Ab Initio Multiple Cloning Method for Non-Adiabatic Excited-State Molecular Dynamics in NWChem

The recently developed ab-initio multiple cloning (AIMC) approach based on the multicongurational Ehrenfest (MCE) method provides a powerful and accurate way of describing the excited-state dynamics of molecular systems. The AIMC method is a controlled approximation to non-adiabatic dynamics with a particular strength in the proper description of decoherence effects due to branching of vibrational wavepackets at a level crossing. In this work, we report a new implementation of the AIMC algorithm in the open source NWChem computational chemistry program. The framework combines linear-response time-dependent density functional theory with Ehrenfest mean-eld theory to determine the equations of motion for classical trajectories. The multi-dimensional wave function is decomposed into a superposition of Gaussian coherent states guided by Ehrenfest trajectories (i.e., MCE approach), which can clone with fully quantum mechanical amplitudes and phases. By using an efficient time-derivative based non-adiabatic coupling approach within the AIMC method, all observable are calculated on-the-y in the non-adiabatic molecular dynamics process. As a representative example, we apply our implementation to study the ultrafast photoinduced electronic and vibrational energy transfer in a pyridine molecule. The effects of the cloning procedure on electronic and vibrational coherence, relaxation and unidirectional energy transfer are discussed. This new AIMC implementation provides a high-level non-adiabatic molecular dynamics framework for simulating photoexcited dynamics in complex molecular systems and experimentally relevant ultrafast spectroscopic probes, such as nonlinear coherent optical and X-ray signals.

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

Simulating the Excited-State Dynamics of Polaritons with Ab Initio Multiple Spawning

Over the past decade, there has been a growth of interest in polaritonic chemistry, where the formation of hybrid light–matter states (polaritons) can alter the course of photochemical reactions. These hybrid states are created by strong coupling between molecules and photons in resonant optical cavities and can even occur in the absence of light when the molecule is strongly coupled with the electromagnetic fluctuations of the vacuum field. Here, we present a first-principles model to simulate nonadiabatic dynamics of such polaritonic states inside optical cavities by leveraging graphical processing units (GPUs). Our first implementation of this model is specialized for a single molecule coupled to a single-photon mode confined inside the optical cavity but with any number of excited states computed using complete active space configuration interaction (CASCI) and a Jaynes–Cummings-type Hamiltonian. Using this model, we have simulated the excited-state dynamics of a single salicylideneaniline (SA) molecule strongly coupled to a cavity photon with the ab initio multiple spawning (AIMS) method. We demonstrate how the branching ratios of the photodeactivation pathways for this molecule can be manipulated by coupling to the cavity. We also show how one can stop the photoreaction from happening inside of an optical cavity. Finally, we also investigate cavity-based control of the ordering of two excited states (one optically bright and the other optically dark) inside a cavity for a set of molecules, where the dark and bright states are close in energy.

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

Activation, Dehydrogenation, and Carbon–Carbon Coupling of Methane by Iridium Cations Studied by Infrared Multiple Photon Dissociation Spectroscopy and Density Functional Theory

Products resulting from the sequential activation of one, two, three, and four methane molecules by atomic iridium cations were characterized by gas-phase infrared multiple photon dissociation spectroscopy and density functional theory (DFT) calculations. Iridium cations were generated using a laser ablation source and reacted with methane in a linear radiofrequency ion trap before mass analysis and spectroscopic interrogation in a Fourier transform ion cyclotron resonance mass spectrometer coupled to the free-electron laser for intracavity experiments (FELICE) beamline. Product ions were irradiated using infrared light over the 250–1500 cm –1 range. Comparisons between the experimental and DFT-calculated spectra enabled structural determination of the products formed. The observed products include HIrCH + , Ir(CH 2 ) 2 + , H s Ir(C 3 H 5 ) + , and Ir(CH 3 ) s (C 3 H 5 ) + , where the subscript s denotes a syn orientation of the two ligands. Furthermore, formation of the latter two products provides evidence for efficient C–H bond activation and subsequent C–C coupling on the atomic iridium cation.

Chemical reactions↗
DOE OSTI2020

Nonadiabatic Dynamics of Photoexcited cis-Stilbene Using Ab Initio Multiple Spawning

The photochemistry of cis-stilbene proceeds through two pathways: cis-trans isomerization and ring closure to 4a,4b-dihydrophenanthrene (DHP). Despite serving for many decades as a model system for photoisomerization, the photodynamics of cis-stilbene is still not fully understood. In this work, we use ab initio multiple spawning on a SA-2-CASSCF(2,2) potential energy surface to simulate the nonadiabatic dynamics of isolated cis-stilbene. We find the cyclization (to DHP and cis-stilbene) and isomerization (to trans- and cis-stilbene) reaction coordinates to be orthogonal; branching between the two pathways is determined on the S1 excited state within 150 fs of photoexcitation. Furthermore ,trajectory basis functions (TBFs) undergoing cyclization decay rapidly to the ground state in 250 fs, while TBFs moving along the isomerization coordinate remain on the excited state longer, with the majority decaying between 300 and 500 fs. We observe three avoided crossing regions in the dynamics: two along the isomerization coordinate (displaying pyramidalization and migration of an ethylenic hydrogen or phenyl group), and one DHP-like conical intersection along the cyclization coordinate. The isomeric form of the vibrationally hot photoproducts (as determined by measurement 2 ps after photoexcitation) is determined within less than 50 fs of decay to the ground state mediated by passage through a conical intersection. Excess vibrational energy of ground state cis- and trans-stilbene is channelled into phenyl torsions (with mostly opposing directionality). Finally, our simulations are validated by direct comparison to experiment for the absorption spectrum, branching ratio of the three photoproducts (44:52:4 cis-stilbene:trans-stilbene:DHP), and excited state lifetime (520 ± 40 fs).

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

Multiplex Detection of Multiple-Quantum/Single-Quantum NMR Correlation Spectra

High-ordered multiple-quantum coherences have been used to gauge the size of coupled networks of nuclear spins but are seldom used in modern high-resolution solid-state NMR spectroscopy due to the low resolution of earlier techniques. Herein, we extend this work to the third dimension by designing an MQ spin counting experiment with full chemical resolution of the nuclei involved in the coherences. The technique uses multiplex processing to simultaneously acquire MQ/1Q correlation 2D spectra, with all even-ordered values of M, in the same amount of time it would take to acquire the 2Q/1Q spectrum alone. Further, we apply this multiplexed MQ/1Q correlation method to probe site clustering on functionalized silica surfaces and find the first evidence of clusters involving three or more functionalities. When applied to a supported zirconium metallocene, the observation of a 6Q coherence between six cyclopentadienyl proton nuclei confirms the colocation of two cyclopentadienyl ligands on a single metal center.

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

Multiple Operando Fields Can Identify a Predictive Mass Transport Theory in Electrolytes

An electrolyte transport theory connects its transport properties, evolution of spatiotemporal fields (e.g., concentration), and corresponding macroscopic current and voltage responses. Given this interconnection, the transport properties are typically inferred by analyzing the macroscopic response through the lens of a chosen electrolyte transport theory. Unfortunately, the same macroscopic measurements can be analyzed by using different theories to arrive at seemingly dissimilar properties that are inconsistent with each other. Here, we offer a resolution to this dilemma by analyzing multiple spatiotemporal (i.e., operando) fields for a given electrolyte. We show that predictive transport theory can analyze operando fields to estimate underlying transport properties and subsequently predict another operando field. A theory passing this test identifies meaningful transport properties such that the electrolyte behavior can be accurately predicted over a wide range of excitations, and is critical to property-based electrolyte screening and electrolyte discovery efforts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Use of a Multiple Hydride Donor To Achieve an n-Doped Polymer with High Solvent Resistance

We report the ability to insolubilize doped semiconducting polymer layers can help enable the fabrication of efficient multilayer solution-processed electronic and optoelectronic devices. Here, we present a promising approach to simultaneously n-dope and largely insolubilize conjugated polymer films using tetrakis[{4-(1,3-dimethyl-2,3-dihydro-1H-benzo[d]imidazol-2-yl)phenoxy}methyl]methane (tetrakis-O-DMBI-H), which consists of four 2,3-dihydro-1H-benzoimidazole (DMBI-H) n-dopant moieties covalently linked to one another. Doping a thiophene-fused benzodifurandione-based oligo(p-phenylenevinylene)-co-thiophene polymer (TBDOPV-T) with tetrakis-O-DMBI-H results in a highly n-doped film with bulk conductivity of 15 S cm –1 . Optical absorption spectra provide evidence for film retention of ~93% after immersion in o-dichlorobenzene for 5 min. The optical absorption signature of the charge carriers in the n-doped polymer decreases only slightly more than that of the neutral polymer under these conditions, indicating that the exposure to solvent also results in negligible dedoping of the film. Moreover, thermal treatment studies on a tetrakis-O-DMBI-H-doped TBDOPV-T film in contact with another undoped polymer film indicate immobilization of the molecular dopant in TBDOPV-T. This is attributed to the multiple electrostatic interactions between each dopant tetracation and up to four nearby anionic doped polymer segments.

36 MATERIALS SCIENCE↗
DOE OSTI2020

A near-explicit mechanistic evaluation of Isoprene photochemical seecondary organic aerosol formation and evolution: simulations of multiple chamber experiments with and without added NOx

Experimentally determined yields of secondary organic aerosol (SOA) from the photochemical oxidation of isoprene in the absence of aqueous acidic aerosol vary substantially, both within a given experiment and across different environmental chamber conditions. The underlying mechanisms driving this variation remain poorly evaluated, leading to significant uncertainty in how to extrapolate laboratory chamber results to the atmosphere. Herein, we compare SOA predictions from a near-explicit gas-phase chemical mechanism of isoprene oxidation by the hydroxyl radical (OH) in the presence and absence of nitrogen oxide radicals (NOx), to multiple chamber experiments on non-aqueous isoprene photochemical SOA (ipSOA) conducted by different groups in different chambers. SOA is predicted by volatility-driven gas-particle partitioning of hundreds of individual reaction products. The mechanism includes simplified descriptions of particle-phase organic chemistry, including organic hydroperoxide photolysis, and organic nitrate hydrolysis and accretion reactions. The model has good skill (mean normalized bias typically within 25%) at predicting the observed formation and evolution of ipSOA across a range of chambers and conditions at low NOx. The model has much less skill at describing the observed non-linear response of ipSOA to elevated NOx. Organic nitrate hydrolysis is unable to explain significant ipSOA at high NOx, whereas particle-phase accretion reactions of tertiary nitrates may play a role. Uncertainties in the chamber radical environment and fate of key organic peroxy radicals (RO2) remain as or even more important than vapor losses to chamber walls in determining how best to extrapolate chamber-based yields to the atmosphere. Implications for likely atmospheric yields of ipSOA and recommendations for future chamber experiments are discussed.

Thornton, Joel A.↗
DOE OSTI2022

Leveraging Multiple Raman Excitation Wavelength Systems for Process Monitoring of Nuclear Waste Streams

Processing nuclear waste from sites such as Hanford is a significant environmental cleanup need while being a significant logistical challenge. Integration of process monitoring tools, that can provide in situ and real-time feedback about the process, can significantly alleviate needs to collect grab samples for process control and product characterization. Raman spectroscopy paired with chemometric analysis is one process monitoring tool that can provide chemical composition information on a large number of chemical targets in nuclear waste streams. However, methods to improve limits of detection as well as drop uncertainty in quantification are needed. Optimizing instrument specifications can achieve this, here this is demonstrated by comparing limits of detection for key analytes when using Raman systems with 671 nm, 532 nm, and 405 nm excitation wavelengths. Generally, limits of detection decease (allowing the measurement of lower salt concentrations) with decreasing wavelength. Similarly, data collection times and averaging were optimized. Finally, multiple chemometric modeling approaches were leveraged, including multiblock methods that combined data from all three Raman systems to simultaneously quantify targets with improved sensitivity.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2021

Can Multiple Ions in an Ionic Liquid Improve the Biomass Pretreatment Efficacy?

we report over the last few decades, efforts to transition the global production of fuels and chemicals toward renewable carbon feedstocks have accelerated. A large portion of these efforts have focused on valorization of one of the most abundant renewable carbon sources, lignocellulose. Pretreatment of lignocellulose is the first critical step in this process. In this study, novel ionic liquid (IL) systems consisting of multiple ions known to be effective at biomass pretreatment were tested on woody and grassy biomass. Molecular simulations and experimental results established the synergistic advantages of combining specific individual components in these systems. For pine (woody) biomass, pretreatment with the combination of imidazolium, cholinium, acetate, and lysinate ions achieved 80% glucose and 70% xylose yields at high biomass loading. For sorghum biomass, an IL system comprising cholinium, lysinate, and palmitate ions not only enabled a 98% glucose yield but was also found to be biocompatible in a one-pot configuration, producing the biofuel precursor bisabolene using an engineered strain of the yeast Rhodosporidium toruloides.

09 BIOMASS FUELS↗
DOE OSTI2021

Selective Methane Oxidation to Methanol on ZnO/Cu 2 O/Cu(111) Catalysts: Multiple Site-Dependent Behaviors

Due to the abundance of natural gas in our planet, a major goal is to achieve a direct methane to methanol conversion at medium to low temperatures using mixtures of methane and oxygen. Here, we report an efficient catalyst, ZnO/Cu 2 O/Cu(111), for this process investigated using a combination of reactor testing, scanning tunneling microscopy, ambient-pressure x-ray photoemission spectroscopy, density functional calculations, and kinetic Monte Carlo simulations. The catalyst is capable of methane activation at room temperature and transforms mixtures of methane and oxygen to methanol at 450 K with a selectivity of ~30%. This performance is not seen for other heterogenous catalysts which usually require the addition of water to enable a significant conversion of methane to methanol. The unique coarse structure of the ZnO islands supported on a Cu 2 O/Cu(111) substrate provides a collection of multiple centers that display different catalytic activity during the reaction. ZnO-Cu 2 O step sites are active centers for methanol synthesis when exposed to CH 4 and O 2 due to an effective O-O bond dissociation, which enables a methane-to-methanol conversion with a reasonable selectivity. Upon addition of water, the defected O-rich ZnO sites, introduced by Zn vacancies, show superior behavior towards methane conversion and enhance the overall methanol selectivity to over 80%. Thus, in this case, the surface sites involved in a direct CH 4 → to CH 3 OH conversion are different from those engaged in methanol formation without water. Furthermore, the identification of the site-dependent behavior of ZnO/Cu 2 O/Cu(111) opens a design strategy for guiding efficient methane reforming with high methanol selectivity.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Using Multiple Signatures to Improve Accuracy of Substorm Identification

Abstract We have developed a new procedure for combining lists of substorm onset times from multiple sources. We apply this procedure to observational data and to magnetohydrodynamic (MHD) model output from 1–31 January 2005. We show that this procedure is capable of rejecting false positive identifications and filling data gaps that appear in individual lists. The resulting combined onset lists produce a waiting time distribution that is comparable to previously published results, and superposed epoch analyses of the solar wind driving conditions and magnetospheric response during the resulting onset times are also comparable to previous results. Comparison of the substorm onset list from the MHD model to that obtained from observational data reveals that the MHD model reproduces many of the characteristic features of the observed substorms, in terms of solar wind driving, magnetospheric response, and waiting time distribution. Heidke skill scores show that the MHD model has statistically significant skill in predicting substorm onset times.

Haiducek, John D.↗
DOE OSTI2023

Compound Continental Risk of Multiple Extreme Floods in the United States

Abstract Understanding spatially correlated floods and modeling joint hazard associated with threshold exceedances across multiple locations is crucial for accurate estimation of continental‐scale portfolio risk. This work uses a non‐parametric copula‐based spatial simulator to analyze peak floods across the United States to derive the first‐of‐its‐kind continental portfolio risk estimates at the 10‐ and 100‐year return levels. We find significant interdependence in floods across the nation, revealing the recurring pattern of extreme events affecting the Northeast, Central, West, and Northwest United States in the same year. The stochastic simulator effectively manages high‐dimensional data and offers reliable uncertainty estimates for both spatially dependent floods and the aggregated flood losses at the continental level. El Niño‐Southern Oscillation and Atlantic Multidecadal Oscillation are identified as statistically significant tele‐connectors of aggregate loss. This research aims to advance the understanding of compound continental flood hazard and the potential large‐scale climate teleconnections that lead to such compound floods.

Geology↗