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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Random sampling of the Green’s Functions for reversible reactions with an intermediate state

Exact random variate generators were developed to sample Green’s functions used in Brownian Dynamics (BD) algorithms for the simulations of chemical systems. These algorithms, which use less than a kilobyte of memory, provide a useful alternative to the table look-up method that has been used in similar work. The cases that are studied with this approach are (1) diffusion-influenced reactions; (2) reversible diffusion-influenced reactions and (3) reactions with an intermediate state such as enzymatic catalysis. The results are validated by comparison with those obtained by the Independent Reaction Times (IRT) method. This work is part of our effort in developing models to understand the role of radiation chemistry in the radiation effects on human body and may eventually be included in event-based models of space radiation risk.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
NASA NTRSDate not supplied

An Initial Concept for Intermediate-State, Passenger-Carrying Urban Air Mobility Operations

This paper describes a general “vision” concept of operations (ConOps) for intermediate state, passenger-carrying urban air mobility (UAM) missions that has been developed jointly by NASA and Deloitte with input from stakeholders in the UAM ecosystem. This vision ConOps provides a broad overview of some of the high-level requirements for realizing the simultaneous operation of hundreds of aircraft over a single metropolitan area in a wide range of weather conditions as conceptualized by many visionaries at the time of its publication. The concepts contained in this vision ConOps are intended to provide a starting point for further discussions and investigations into how UAM operations can be best enabled. Consequently, we also describe some of the areas where additional research is required before a detailed baseline ConOps can be finalized.

urban air mobility↗
DOE OSTI2018

Unexpected Intermediate State Photoinduced in the Metal-Insulator Transition of Submicrometer Phase-Separated Manganites

At ultrafast timescales, the initial and final states of a first-order metal-insulator transition often coexist forming clusters of the two phases. In this work, we report an unexpected third long-lived intermediate state emerging at the photoinduced first-order metal-insulator transition of La 0.325 Pr 0.3 Ca 0.375 MnO 3 , known to display submicrometer length-scale phase separation. Using magnetic force microscopy and time-dependent magneto-optical Kerr effect, we determined that the third state is a nanoscale mixture of the competing ferromagnetic metallic and charge-ordered insulating phases, with its own physical properties. This discovery bridges the two different families of colossal magnetoresistant manganites known experimentally and shows for the first time that the associated states predicted by theory can coexist in a single sample.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Two-photon exchange from intermediate state resonances in elastic electron-proton scattering

In this paper, we use a recently developed dispersive approach to compute the two-photon exchange (TPE) correction to elastic electron-proton scattering, including contributions from hadronic $J^P=1/2^\pm$ and $3/2^\pm$ resonant intermediate states below~1.8~GeV. For the transition amplitudes from the proton ground state to the resonant excited states we employ new exclusive meson electroproduction data from CLAS at $Q^2 \lesssim 5$~GeV$^2$, and we explore the effects of both fixed and dynamic widths for the resonances. Among the resonant states, the $N(1520)~\!3/2^-$ becomes dominant for $Q^2 \gtrsim 2$~GeV$^2$, with a sign opposite to the comparably sized $\Delta(1232)~\!3/2^+$ contribution, leading to an overall increase in the size of the TPE correction to the cross section relative to the nucleon only contribution at higher $Q^2$ values. The results are in good overall agreement with recent $e^+ p$ to $e^- p$ cross section ratio and polarization transfer measurements, and provide compelling evidence for a resolution of the electric to magnetic form factor ratio discrepancy.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

19.31% binary organic solar cell and low non-radiative recombination enabled by non-monotonic intermediate state transition

Non-fullerene acceptors based organic solar cells represent the frontier of the field, owing to both the materials and morphology manipulation innovations. Non-radiative recombination loss suppression and performance boosting are in the center of organic solar cell research. Here, we developed a non-monotonic intermediate state manipulation strategy for state-of-the-art organic solar cells by employing 1,3,5-trichlorobenzene as crystallization regulator, which optimizes the film crystallization process, regulates the self-organization of bulk-heterojunction in a non-monotonic manner, i.e., first enhancing and then relaxing the molecular aggregation. As a result, the excessive aggregation of non-fullerene acceptors is avoided and we have achieved efficient organic solar cells with reduced non-radiative recombination loss. In PM6:BTP-eC9 organic solar cell, our strategy successfully offers a record binary organic solar cell efficiency of 19.31% (18.93% certified) with very low non-radiative recombination loss of 0.190 eV. And lower non-radiative recombination loss of 0.168 eV is further achieved in PM1:BTP-eC9 organic solar cell (19.10% efficiency), giving great promise to future organic solar cell research.

14 SOLAR ENERGY↗
DOE OSTI2011

Structures of segments of [alpha]-synuclein fused to maltose-binding protein suggest intermediate states during amyloid formation

Aggregates of the protein {alpha}-synuclein are the main component of Lewy bodies, the hallmark of Parkinson's disease. {alpha}-Synuclein aggregates are also found in many human neurodegenerative diseases known as synucleinopathies. In vivo, {alpha}-synuclein associates with membranes and adopts {alpha}-helical conformations. The details of how {alpha}-synuclein converts from the functional native state to amyloid aggregates remain unknown. In this study, we use maltose-binding protein (MBP) as a carrier to crystallize segments of {alpha}-synuclein. From crystal structures of fusions between MBP and four segments of {alpha}-synuclein, we have been able to trace a virtual model of the first 72 residues of {alpha}-synuclein. Instead of a mostly {alpha}-helical conformation observed in the lipid environment, our crystal structures show {alpha}-helices only at residues 1-13 and 20-34. The remaining segments are extended loops or coils. All of the predicted fiber-forming segments based on the 3D profile method are in extended conformations. We further show that the MBP fusion proteins with fiber-forming segments from {alpha}-synuclein can also form fiber-like nano-crystals or amyloid-like fibrils. Our structures suggest intermediate states during amyloid formation of {alpha}-synuclein.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2016

Warfarin traps human vitamin K epoxide reductase in an intermediate state during electron transfer

Although warfarin is the most widely used anticoagulant worldwide, the mechanism by which warfarin inhibits its target, human vitamin K epoxide reductase (hVKOR), remains unclear. We show that warfarin blocks a dynamic electron-transfer process in hVKOR. A major fraction of cellular hVKOR is at an intermediate redox state of this process containing a Cys51-Cys132 disulfide, a characteristic accommodated by a four-transmembrane-helix structure of hVKOR. Warfarin selectively inhibits this major cellular form of hVKOR, whereas disruption of the Cys51-Cys132 disulfide impairs warfarin binding and causes warfarin resistance. Relying on binding interactions identified by cysteine alkylation footprinting and mass spectrometry coupled with mutagenesis analysis, we are able to conduct structure simulations to reveal a closed warfarin-binding pocket stabilized by the Cys51-Cys132 linkage. Understanding the selective warfarin inhibition of a specific redox state of hVKOR should enable the rational design of drugs that exploit the redox chemistry and associated conformational changes in hVKOR.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Large structural modulations in the relaxor ferroelectric and intermediate state of strontium rich members (x>0.6) of the Sr{sub x}Ba{sub 1−x}Nb{sub 2}O{sub 6} (sbn) solid solution series

The amplitudes of the positional, occupational and adp modulations of sbn mixed crystals are strongly enhanced for high strontium contents. The increase of structural modulations is accompanied by reduced spontaneous electric polarization largely due to smaller off-center shifts of the niobium atoms. Beyond the room temperature ferroelectric – intermediate transition near x=0.77, anomal large U{sub 33} atomic displacement parameters of the niobium atoms indicate static disorder caused by loss of orientational coupling between residual shifts of Nb atoms in neighboring NbO{sub 6} octahedra. Change of satellite intensities show a reduction from two-dimensional to one-dimensional modulation which is not consistent with tetragonal symmetry. The pseudo-tetragonally twinned crystal structure of sbn82 was refined in the orthorhombic super-space group A2mm(½0γ)000. The apparent tetragonal symmetry of the other investigated sbn samples also seems to be due to pseudo tetragonal twinning with equal twin volumes. The modulations mainly consist of cooperatively tilted NbO{sub 6} octahedra and wave-like ordered incomplete occupation of the largest cation sites (Me2a and b) by Ba{sup 2+} and Sr{sup 2+}. Furthermore, the atomic displacement parameters of the Me2 sites are strongly modulated. - Graphical abstract: Satellite reflections and modulation coefficients in the solid solution series Sr{sub x}Ba{sub 1−x}Nb{sub 2}O{sub 6}. - Highlights: • The modulationed structures are refined for the whole composition range of sbn32–sbn82 in tetragonal and orthorhombic setting. • The amplitudes of positional, occupational and adp modulations increase strongly with the strontium content. • Evidence is presented that the sbn crystals are pseudo tetragonally twinned. • The ferroelectric–intermediate paraelectric transition is not accompanied by a change of symmetry. • Anomal adp of intermediate (non-ferroelectric) sbn82 indicate loss of coupling between off-center shifts of neighboring niobium.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Annihilation of p-bar + p {yields} e{sup +} + e{sup -} + {pi}{sup 0} and p-bar + p {yields} {gamma} + {pi}{sup 0} through an {omega}-Meson intermediate state

The s-channel annihilation of a proton and an antiproton into a neutral pion and a real or virtual photon followed by lepton pair emission is studied. Such a mechanism is expected to play a role at moderate values of the total energy {radical}s, when the pion is emitted in the angular region around 90 Degree-Sign in the center-of-mass system. A fair comparison with the existing data is obtained taking scattering and annihilation channels into account. The cross section is calculated and numerical results are given in the kinematical range accessible in the PANDA experiment at FAIR.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

B{sup (*)}B{sup (*)} intermediate states contribution to {Upsilon}(4S,5S){yields}{eta}{sub b}+{gamma} radiative decay

In this work, we investigate the rescattering effects in the radiative decay {Upsilon}(5S){yields}{eta}{sub b}+{gamma}, which were suggested to be crucially important for understanding the anomalous largeness of the branching ratios B({Upsilon}(5S){yields}{Upsilon}(1S)+{pi}{pi}) and B({Upsilon}(5S){yields}{Upsilon}(1S)+{eta}). Our calculations show that the rescattering effects may enhance {Gamma}({Upsilon}(10860){yields}{eta}{sub b}+{gamma}) by four orders, but the tetraquark structure does not. Recently the BABAR and CLEO collaborations have measured the mass of {eta}{sub b} and the branching ratios B({Upsilon}(2S){yields}{eta}{sub b}+{gamma}), B({Upsilon}(3S){yields}{eta}{sub b}+{gamma}). We hope that very soon, {Upsilon}(10860){yields}{eta}{sub b}+{gamma} will be measured and it would be an ideal opportunity for testing whether the rescattering or the tetraquark structure is responsible for the anomaly of B({Upsilon}(5S){yields}{Upsilon}(nS){pi}{sup +}{pi}{sup -}(n=1,2,3)), i.e., the future measurements on the radiative decays of {Upsilon}(5S) might be a touchstone of the two mechanisms.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Crystal Structure of the Maltose Transporter in a Pretranslocation Intermediate State

Adenosine triphosphate (ATP)-binding cassette (ABC) transporters convert chemical energy from ATP hydrolysis to mechanical work for substrate translocation. They function by alternating between two states, exposing the substrate-binding site to either side of the membrane. A key question that remains to be addressed is how substrates initiate the transport cycle. Using x-ray crystallography, we have captured the maltose transporter in an intermediate step between the inward- and outward-facing states. We show that interactions with substrate-loaded maltose-binding protein in the periplasm induce a partial closure of the MalK dimer in the cytoplasm. ATP binding to this conformation then promotes progression to the outward-facing state. These results, interpreted in light of biochemical and functional studies, provide a structural basis to understand allosteric communication in ABC transporters.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2016

MHC class II complexes sample intermediate states along the peptide exchange pathway

The presentation of peptide-MHCII complexes (pMHCIIs) for surveillance by T cells is a well-known immunological concept in vertebrates, yet the conformational dynamics of antigen exchange remain elusive. By combining NMR-detected H/D exchange with Markov modelling analysis of an aggregate of 275 microseconds molecular dynamics simulations, we reveal that a stable pMHCII spontaneously samples intermediate conformations relevant for peptide exchange. More specifically, we observe two major peptide exchange pathways: the kinetic stability of a pMHCII’s ground state defines its propensity for intrinsic peptide exchange, while the population of a rare, intermediate conformation correlates with the propensity of the HLA-DM-catalysed pathway. Helix-destabilizing mutants designed based on our model shift the exchange behaviour towards the HLA-DM-catalysed pathway and further allow us to conceptualize how allelic variation can shape an individual’s MHC restricted immune response.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2014

Shape-memory transformations of NiTi: Minimum-energy pathways between austenite, martensites, and kinetically limited intermediate states

NiTi is the most used shape-memory alloy, nonetheless, a lack of understanding remains regarding the associated structures and transitions, including their barriers. Using a generalized solid-state nudge elastic band (GSSNEB) method implemented via density-functional theory, we detail the structural transformations in NiTi relevant to shape memory: those between body-centered orthorhombic (BCO) groundstate and a newly identified stable austenite (“glassy” B2-like) structure, including energy barriers (hysteresis) and intermediate structures (observed as a kinetically limited R-phase), and between martensite variants (BCO orientations). All results are in good agreement with available experiment. We contrast the austenite results to those from the often-assumed, but unstable B2. Furthermore, these high- and low-temperature structures and structural transformations provide much needed atomic-scale detail for transitions responsible for NiTi shape-memory effects.

36 MATERIALS SCIENCE↗
DOE OSTI2018

MHC Class II Complexes Sample Intermediate States along the Antigenic Peptide Exchange Pathway

The presentation of antigenic peptide-MHCII complexes (pMHCIIs) for surveillance by T cells is a well-known immunological concept in vertebrates, yet the conformational dynamics of antigen exchange remain elusive. By combining NMR-detected H/D exchange with Markov modelling analysis of an aggregate of milliseconds of adaptive molecular dynamics simulations, we reveal that a stable pMHCII spontaneously samples intermediate conformations that are both relevant for peptide exchange and consistent with X-ray crystallography.

Biophysics↗
DOE OSTI2021

Resolving Dynamics in the Ensemble: Finding Paths through Intermediate States and Disordered Protein Structures

Proteins have been found to inhabit a diverse set of three-dimensional structures. The dynamics that govern protein interconversion between structures happen over a wide range of time scales-picoseconds to seconds. Our understanding of protein functions and dynamics is largely reliant upon our ability to elucidate physically populated structures. From an experimental structural characterization perspective, we are often limited to measuring the ensemble-averaged structure both in the steady-state and time-resolved regimes. Generating kinetic models and understanding protein structure–function relationships require atomistic knowledge of the populated states in the ensemble. Here, we present ensemble refinement methodologies that integrate time-resolved experimental signals with molecular dynamics models. We first discuss integration of experimental structural restraints to molecular models in disordered protein systems that adhere to the principle of maximum entropy for creating a complete set of ensemble structures. We then propose strategies to find kinetic pathways between the refined structures, using time-resolved inputs to guide molecular dynamics trajectories and the use of inference to generate tailored stimuli to prepare a desired ensemble of protein states.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗