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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 1,099 records · Page 61
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Direct Evidence for Buffer-Enhanced Proton-Coupled Electron Transfer Generation of a High-Valent Metal-Oxo Complex

Here, the oxidation of metal-aquo and -hydroxo complexes to generate the high-valent metal-oxo species used in oxidative catalysis is often kinetically slow due to sluggish proton transfer between ligated −H 2 O/–OH in the proton-coupled electron transfer (PCET) chemistry. In this research, a ruthenium water oxidation catalyst anchored to a conductive tin-doped indium oxide (ITO) thin film, abbreviated ITO|Ru II –OH 2 , was characterized by spectroscopic and electrochemical methods in acetate or phosphate buffers. The deprotonated intermediate, Ru II –OH, was observed spectroscopically in the PCET half-reaction ITO(e – )|Ru III –OH + H + → ITO|Ru II –OH 2 indicating an underlying stepwise ET-PT mechanism. In contrast, at elevated buffer concentrations, this intermediate was absent, and a 2–4 order of magnitude increase in the proton transfer rate constant was observed. Kinetic data for this PCET reaction measured as a function of the driving force provided the reorganization energy λ = 1.05 eV and was assigned to a concerted electron–proton transfer (EPT) mechanism. In addition, the standard heterogeneous rate constants for two PCET equilibria, Ru III –OH + H + + e – ⇌ Ru II –OH 2 and Ru IV = O + H + + e – ⇌ Ru III –OH were enhanced by these same buffers. Collectively, the data show that the added buffers can enhance the kinetics and thermodynamics for PCET reactions relevant to oxidative catalysis.

Catalysts↗
DOE OSTI2012

Synthesis and magnetic properties of the high-pressure scheelite-type GdCrO{sub 4} polymorph

The scheelite-type polymorph of GdCrO{sub 4} has been obtained from the corresponding zircon-type compound under high pressure and temperature conditions, namely 4 GPa and 803 K. The crystal structure has been determined by X-ray powder diffraction. This GdCrO{sub 4} scheelite crystallizes in a tetragonal symmetry with space group I4{sub 1}/a (No. 88, Z=4), a=5.0501(1) A, c=11.4533(2) A and V=292.099(7) A{sup 3}. The thermal decomposition leads to the formation of the zircon-polymorph as intermediate phase at 773 K to end in the corresponding GdCrO{sub 3} distorted perovskite-structure at higher temperatures. Magnetic susceptibility and magnetization measurements suggest the existence of long-range antiferromagnetic interactions which have been also confirmed from specific heat measurements. Neutron powder diffraction data reveal the simultaneous antiferromagnetic Gd{sup 3+} and Cr{sup 5+} ordering in the scheelite-type GdCrO{sub 4} with a T{sub N}{approx}20 K. The magnetic propagation vector was found to be k=(0 0 0). Combined with group theory analysis, the best neutron powder diffraction fit was obtained with a collinear antiferromagnetic coupling in which the m{sub Cr{sup 5}{sup +}} and m{sub Gd{sup 3}{sup +}} magnetic moments are confined in the tetragonal basal plane according to the mixed representation {Gamma}{sub 6} Circled-Plus {Gamma}{sub 8}. Thermal decomposition of the GdCrO{sub 4} high pressure polymorph, from the scheelite-type through the zircon-type structure as intermediate to end in the GdCrO{sub 3} perovskite. Highlights: Black-Right-Pointing-Pointer New high pressure GdCrO{sub 4} polymorph crystallizing in the scheelite type structure. Black-Right-Pointing-Pointer It is an antiferromagnet with a metamagnetic transition at low magnetic fields. Black-Right-Pointing-Pointer We have determined its magnetic structure from powder neutron diffraction data. Black-Right-Pointing-Pointer Otherwise, the room pressure zircon-polymorph is a ferromagnet. Black-Right-Pointing-Pointer The paper will be a great contribution in the study of 3d-4f magnetic interactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Electrophotocatalysis with a Trisaminocyclopropenium Radical Dication

Abstract Visible‐light photocatalysis and electrocatalysis are two powerful strategies for the promotion of chemical reactions. Here, these two modalities are combined in an electrophotocatalytic oxidation platform. This chemistry employs a trisaminocyclopropenium (TAC) ion catalyst, which is electrochemically oxidized to form a cyclopropenium radical dication intermediate. The radical dication undergoes photoexcitation with visible light to produce an excited‐state species with oxidizing power (3.33 V vs. SCE) sufficient to oxidize benzene and halogenated benzenes via single‐electron transfer (SET), resulting in C−H/N−H coupling with azoles. A rationale for the strongly oxidizing behavior of the photoexcited species is provided, while the stability of the catalyst is rationalized by a particular conformation of the cis ‐2,6‐dimethylpiperidine moieties.

Huang, He↗
DOE OSTI2025

Light-Driven C(sp 3 )–C(sp 3 ) Bond Functionalizations Enabled by the PCET Activation of Alcohol O–H Bonds

Methods that enable the selective functionalization of C–C bonds offer unique opportunities for the skeletal diversification of complex molecules and provide access to unique structures without the need for de novo synthesis. While considerable advances have been made in transition-metal-based approaches, much recent work has focused on alternative strategies for C–C bond cleavage enabled by transient free radicals. In particular, alkoxy radicals derived from simple alcohols are known to significantly destabilize adjacent C–C bonds, enabling spontaneous cleavage to eject a carbon-centered radical and afford carbonyl products via β-fragmentation. Here, while this reactivity has long been recognized, its applications in synthesis have been limited, in part, by the challenges associated with generating the key alkoxy radical intermediates.

Alcohols↗
DOE OSTI2014

Effects of a weakly 3-D equilibrium on ideal magnetohydrodynamic instabilities

The effect of a small three-dimensional equilibrium distortion on an otherwise axisymmetric configuration is shown to be destabilizing to ideal magnetohydrodynamic modes. The calculations assume that the 3-D fields are weak and that shielding physics is present so that no islands appear in the resulting equilibrium. An eigenfunction that has coupled harmonics of different toroidal mode number is constructed using a perturbation approach. The theory is applied to the case of tokamak H-modes with shielded resonant magnetic perturbations (RMPs) present indicating RMPs can be destabilizing to intermediate-n peeling-ballooning modes.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2012

Livingston Parish Landfill Methane Recovery Project (Feasibility Study)

The Woodside Landfill is owned by Livingston Parish, Louisiana and is operated under contract by Waste Management of Louisiana LLC. This public owner/private operator partnership is commonplace in the solid waste industry today. The landfill has been in operation since approximately 1988 and has a permitted capacity of approximately 41 million cubic yards. Based on an assumed in-place waste density of 0.94 ton per cubic yard, the landfill could have an expected design capacity of 39.3 million tons. The landfill does have an active landfill gas collection and control system (LFGCCS) in place because it meets the minimum thresholds for the New Source Performance Standards (NSPS). The initial LFGCS was installed prior to 2006 and subsequent phases were installed in 2007 and 2010. The Parish received a grant from the United States Department of Energy in 2009 to evaluate the potential for landfill gas recovery and utilization at the Woodside Landfill. This includes a technical and economic feasibility study of a project to install a landfill gas to energy (LFGTE) plant and to compare alternative technologies. The LFGTE plant can take the form of on-site electrical generation, a direct use/medium Btu option, or a high-Btu upgrade technology. The technical evaluation in Section 2 of this report concludes that landfill gas from the Woodside landfill is suitable for recovery and utilization. The financial evaluations in sections 3, 4, and 5 of this report provide financial estimates of the returns for various utilization technologies. The report concludes that the most economically viable project is the Electricity Generation option, subject to the Parish’s ability and willingness to allocate adequate cash for initial capital and/or to obtain debt financing. However, even this option does not present a solid return: by our estimates, there is a 19 year simple payback on the electricity generation option. All of the energy recovery options discussed in this report economically stressed. The primary reason for this is the recent fundamental shift in the US energy landscape. Abundant supplies of natural gas have put downward pressure on any project that displaces natural gas or natural gas substitutes. Moreover, this shift appears long-term as domestic supplies for natural gas may have been increased for several hundred years. While electricity prices are less affected by natural gas prices than other thermal projects, they are still significantly affected since much of the power in the Entergy cost structure is driven by natural gas-fired generation. Consequently, rates reimbursed by the power company based on their avoided cost structure also face downward pressure over the near and intermediate term. In addition, there has been decreasing emphasis on environmental concerns regarding the production of thermal energy, and as a result both the voluntary and mandatory markets that drive green attribute prices have softened significantly over the past couple of years. Please note that energy markets are constantly changing due to fundamental supply and demand forces, as well as from external forces such as regulations and environmental concerns. At any point in the future, the outlook for energy prices may change and could deem either the electricity generation or pipeline injection project more feasible. This report is intended to serve as the primary background document for subsequent decisions made at Parish staff and governing board levels.

09 BIOMASS FUELS↗
DOE OSTI2023

Comparative Study of High-Resolution LysB29(Nε-myristoyl) des(B30) Insulin Structures Display Novel Dynamic Causal Interrelations in Monomeric-Dimeric Motions

The treatment of insulin-dependent diabetes mellitus is characterized by artificial supplementation of pancreatic β-cell ability to regulate sugar levels in the blood. Even though various insulin analogs are crucial for reasonable glycemic control, understanding the dynamic mechanism of the insulin analogs may help to improve the best-protracted insulin analog to assist people with type 1 diabetes (T1D) to live comfortably while maintaining tight glycemic control. Here, we present the high-resolution crystal structure of NN304, known as insulin detemir, to 1.7 Å resolution at cryogenic temperature. We computationally further investigated our crystal structure’s monomeric-dimeric conformation and dynamic profile by comparing it with a previously available detemir structure (PDB ID: 1XDA). Our structure (PDB ID: 8HGZ), obtained at elevated pH, provides electrostatically triggered minor movements in the equilibrium between alternate conformational substates compared to the previous structure, suggesting it might induce an intermediate state in the dissociation pathway of the insulin detemir’s hexamer:dihexamer equilibrium. Supplemented with orientational cross-correlation analysis by a Gaussian network model (GNM), this alternate oligomeric conformation offers the distinct cooperative motions originated by loose coupling of distant conformational substates of a protracted insulin analog that has not been previously observed.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1977

Wideband heterodyne receiver for laser communication system

A heterodyne receiver for laser communication is described which includes a front end having a cooled photomixer contained in a hermetically sealed spaced quality housing designed for wide bandwidth transmission. The photomixer is coupled through a wideband preamplifier to the receiver back end which includes a frequency tracking network and demodulating equipment. The receiver is capable of tracking a Doppler frequency shift of 750 MHz, positive or negative, and has an instantaneous intermediate frequency information bandwidth of 400 MHz. The receiver system is also capable of operating over a wide temperature range and is designed to be suitable for use in outer space communication.

Flattau, T.↗
DOE OSTI2018

Coupling of Acetaldehyde to Crotonaldehyde on CeO 2– x (111): Bifunctional Mechanism and Role of Oxygen Vacancies

Selective C–C coupling of oxygenates is pertinent to the manufacture of fuel and chemical products from biomass and from derivatives of C 1 compounds (i.e., oxygenates produced from methane and CO 2 ). Here we report a combined experimental and theoretical study on the temperature-programmed reaction (TPR) of acetaldehyde (AcH) on a partially reduced CeO 2– x (111) thin film surface. The experiments have been carried out under ultra-high-vacuum conditions without continuous gas exposure, allowing better isolation of active sites and reactive intermediates than in flow reaction conditions. AcH does not undergo aldol condensation in a typical TPR procedure, even though the enolate form of AcH (CH 2 CHO) is readily produced on CeO 2– x (111) with oxygen vacancies. We find however that a tailored “double-ramp” TPR procedure is able to successfully produce an aldol adduct, crotonaldehyde (CrA). Using density functional theory calculations and microkinetic modeling we explore several possible C–C coupling pathways. We conclude that the double-ramp procedure allows surface oxygen vacancy dimers, stabilized by adsorbate occupation, to form dynamically during the TPR. The vacancy dimers in turn enable C–C coupling to occur between an enolate and an adjacent AcH molecule via a bifunctional enolate–keto mechanism that is distinct from conventional acid- or base-catalyzed aldol condensation reactions. Here, the proposed mechanism indicates that CrA desorption is rate-limiting while C–C coupling is facile.

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

Quantification of Key Peroxy and Hydroperoxide Intermediates in the Low-Temperature Oxidation of Dimethyl Ether

Dimethyl ether (DME) oxidation is a model chemical system with a small number of prototypical reaction intermediates that also has practical importance for low-carbon transportation. Although it has been studied experimentally and theoretically, ambiguity remains in the relative importance of competing DME oxidation pathways in the low-temperature autoignition regime. To focus on the primary reactions in DME autoignition, we measured the time-resolved concentration of five intermediates, CH 3 OCH 2 OO (ROO), OOCH 2 OCH 2 OOH (OOQOOH), HOOCH 2 OCHO (hydroperoxymethyl formate, HPMF), CH 2 O, and CH 3 OCHO (methyl formate, MF), from photolytically initiated experiments. We performed these studies at P = 10 bar and T = 450-575 K, using a high-pressure photolysis reactor coupled to a time-of-flight mass spectrometer with tunable vacuum-ultraviolet synchrotron ionization at the Advanced Light Source. Our measurements reveal that the timescale of ROO decay and product formation is much shorter than predicted by current DME combustion models. The models also strongly underpredict the observed yields of CH 2 O and MF and do not capture the temperature dependence of OOQOOH and HPMF yields. Adding the ROO + OH $\rightarrow$ RO + HO 2 reaction to the chemical mechanism (with a rate coefficient approximated from similar reactions) improves the prediction of MF. Increasing the rate coefficients of ROO ↔ QOOH and QOOH + O 2 ↔ OOQOOH reactions brings the model predictions closer to experimental observations for OOQOOH and HPMF, while increasing the rate coefficient for the QOOH $\rightarrow$ 2 CH 2 O + OH reaction is needed to improve the predictions of formaldehyde. In conclusion, to aid future quantification of DME oxidation intermediates by photoionization mass spectrometry, we report experimentally determined ionization cross-sections for ROO, OOQOOH, and HPMF.

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

Pulsed-Potential Electrolysis Enhances Electrochemical C–N Coupling by Reorienting Interfacial Ions

The electrochemical processing of anthropogenic CO 2 is an emerging technology aimed at utilizing renewable energies to synthesize valuable chemicals. Recently, developments in broadening the scope of the CO 2 reduction reaction (CO 2 RR) by enabling heteroatom coupling have surged with a focus on C–N bond formation. Herein, we investigate the factors that govern the selectivity and activity in synthesizing urea from environmentally malignant chemical feedstocks (CO 2 and NO 3 – ). Through a combination of electrolyte optimization and pulsed potential electrolysis, electrochemical urea production was optimized to a Faradaic efficiency of 60.4% with current densities reaching as high as 310 μA cm –2 . This work was further supported by in situ surface enhanced infrared absorbance spectroscopy that reveals the formation of C–N-related species at low overpotentials. Density functional theory calculations revealed that the reaction progresses between early reduction intermediates for the CO 2 RR and NO 3 RR and offered insights into the impacts of pulsed-potential on substrate transport.

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

Higher harmonic flow coefficients of identified hadrons in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76 $ TeV

The elliptic, triangular, quadrangular and pentagonal anisotropic flow coefficients for π ± , K ± and p + $\bar{p}$ in Pb-Pb collisions at √s NN =2.76 TeV were measured with the ALICE detector at the Large Hadron Collider. The results were obtained with the Scalar Product method, correlating the identified hadrons with reference particles from a different pseudorapidity region. Effects not related to the common event symmetry planes (non-flow) were estimated using correlations in pp collisions and were subtracted from the measurement. The obtained flow coefficients exhibit a clear mass ordering for transverse momentum (p T ) values below ≈ 3 GeV/c. In the intermediate p T region (3 < p T < 6 GeV/c), particles group at an approximate level according to the number of constituent quarks, suggesting that coalescence might be the relevant particle production mechanism in this region. The results for p T < 3 GeV/c are described fairly well by a hydrodynamical model (iEBE-VISHNU) that uses initial conditions generated by A Multi-Phase Transport model (AMPT) and describes the expansion of the fireball using a value of 0.08 for the ratio of shear viscosity to entropy density (η/s), coupled to a hadronic cascade model (UrQMD). Finally, expectations from AMPT alone fail to quantitatively describe the measurements for all harmonics throughout the measured transverse momentum region. However, the comparison to the AMPT model highlights the importance of the late hadronic rescattering stage to the development of the observed mass ordering at low values of p T and of coalescence as a particle production mechanism for the particle type grouping at intermediate values of p T for all harmonics.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Modeling heat transport processes in enhanced geothermal systems: Validation study from EGS Collab Experiment 1

Heat recovery from enhanced geothermal systems (EGS) is a complex process involving heat transport in both fracture networks and rock formations. A comprehensive understanding of and the ability to model the underlying heat transport mechanisms is important for the success of EGS but remains challenging in practice due to the generally insufficient characterization of EGS reservoirs. In the present study, we analyze an extensively monitored intermediate-scale EGS field experiment performed in a well-characterized testbed. The high-resolution, high-quality measurements from the field experiment enable the development of a high-fidelity model incorporating a well-constrained fracture network. Based on the field experiment, we investigate the complex heat transport processes in an EGS-relevant environment and validate the capability of a numerical approach in simulating these inherently coupled heat transport processes. A series of numerical simulations were performed to study the effects of different heat transport mechanisms, including thermal convection with fracture flow, thermal conduction in rock formations, and the Joule-Thomson effect. The agreement of thermal responses between field measurements and simulation results indicates that our numerical approach can appropriately model the heat transport processes pertaining to heat recovery from EGS reservoirs.

Wu, Hui↗
DOE OSTI2012

Hadron spectrum and infrared-finite behavior of QCD running coupling

We study the behavior of the QCD effective coupling α{sub s} in the low-energy region by exploiting the conventional meson spectrum within a relativistic quantum-field model based on analytical confinement of quarks and gluons. The spectra of quark-antiquark and two-gluon bound states are defined by using a master equation similar to the ladder Bethe-Salpeter equation. A new, independent and specific infrared-finite behavior of QCD coupling is found below energy scale ∼1 GeV. Particularly, an infrared-fixed point is extracted at α{sub s}(0) ≅ 0.757 for confinement scale Λ = 345 MeV. We provide a new analytic estimate of the lowest-state glueball mass. As applications, we also estimate masses of some intermediate and heavy mesons as well as the weak-decay constants of light mesons. By introducing only a minimal set of parameters (the quark masses m{sub f} and Λ) we obtain results in reasonable agreement with recent experimental data in a wide range of energy scale ∼0.1–10 GeV. We demonstrate that global properties of some low-energy phenomena may be explained reasonably in the framework of a simple relativistic quantum-field model if one guesses correct symmetry structure of the quark-gluon interaction in the confinement region and uses simple forms of propagators in the hadronisation regime. The model may serve a reasonable framework to describe simultaneously different sectors in low-energy particle physics.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Emergence of a Spin Microemulsion in Spin-Orbit Coupled Bose-Einstein Condensates

We report the first numerical prediction of a “spin microemulsion”—a phase with undulating spin domains resembling classical bicontinuous oil-water-surfactant emulsions—in two-dimensional systems of spinor Bose-Einstein condensates with isotropic Rashba spin-orbit coupling. Using field-theoretic numerical simulations, we investigated the melting of a low-temperature stripe phase with supersolid character and find that the stripes lose their superfluidity at elevated temperature and undergo a Kosterlitz-Thouless-like transition into a spin microemulsion. Momentum distribution calculations highlight a thermally broadened occupation of the Rashba circle of low-energy states with macroscopic and isotropic occupation around the ring. Here, we provide a finite-temperature phase diagram that positions the emulsion as an intermediate, structured isotropic phase with residual quantum character before transitioning at higher temperature into a structureless normal fluid.

Finite temperature field theory↗
DOE OSTI2014

Nonlinear generation of kinetic-scale waves by magnetohydrodynamic Alfvén waves and nonlocal spectral transport in the solar wind

We study the nonlocal nonlinear coupling and generation of kinetic Alfvén waves (KAWs) and kinetic slow waves (KSWs) by magnetohydrodynamic Alfvén waves (MHD AWs) in conditions typical for the solar wind in the inner heliosphere. This cross-scale process provides an alternative to the turbulent energy cascade passing through many intermediate scales. The nonlinearities we study are proportional to the scalar products of wave vectors and hence are called 'scalar' ones. Despite the strong Landau damping of kinetic waves, we found fast growing KAWs and KSWs at perpendicular wavelengths close to the ion gyroradius. Using the parametric decay formalism, we investigate two independent decay channels for the pump AW: forward decay (involving co-propagating product waves) and backward decay (involving counter-propagating product waves). The growth rate of the forward decay is typically 0.05 but can exceed 0.1 of the pump wave frequency. The resulting spectral transport is nonlocal and anisotropic, sharply increasing perpendicular wavenumbers but not parallel ones. AWs and KAWs propagating against the pump AW grow with about the same rate and contribute to the sunward wave flux in the solar wind. Our results suggest that the nonlocal decay of MHD AWs into KAWs and KSWs is a robust mechanism for the cross-scale spectral transport of the wave energy from MHD to dissipative kinetic scales in the solar wind and similar media.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Steering CO 2 hydrogenation toward C–C coupling to hydrocarbons using porous organic polymer/metal interfaces

The conversion of CO 2 into fuels and chemicals is an attractive option for mitigating CO 2 emissions. Controlling the selectivity of this process is beneficial to produce desirable liquid fuels, but C–C coupling is a limiting step in the reaction that requires high pressures. Here, we propose a strategy to favor C–C coupling on a supported Ru/TiO 2 catalyst by encapsulating it within the polymer layers of an imine-based porous organic polymer that controls its selectivity. Such polymer confinement modifies the CO 2 hydrogenation behavior of the Ru surface, significantly enhancing the C 2+ production turnover frequency by 10-fold. We demonstrate that the polymer layers affect the adsorption of reactants and intermediates while being stable under the demanding reaction conditions. Our findings highlight the promising opportunity of using polymer/metal interfaces for the rational engineering of active sites and as a general tool for controlling selective transformations in supported catalyst systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗