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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 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

Precision Study of Excited State Effects in Nucleon Matrix Elements

We present a dedicated precision analysis of the influence of excited states on the calculation of several nucleon matrix elements. This calculation is performed at fixed values of the lattice spacing, volume and pion mass that are typical of contemporary lattice computations. We focus on the nucleon axial charge, g{sub A}, for which we use 7,500 measurements, and on the average momentum of the unpolarized isovector parton distribution, x{sub u-d}, for which we use 23,000 measurements. All computations are done employing N{sub f}=2+1+1 maximally-twisted-mass Wilson fermions and non-perturbatively calculated renormalization factors. We find that excited state effects are negligible for g{sub A} and lead to a O(10%) downward shift for x{sub u-d}.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Precise Measurements of Beam Spin Asymmetries in Semi-Inclusive π 0 production

We present studies of single-spin asymmetries for neutral pion electroproduction in semi-inclusive deep-inelastic scattering of 5.776 GeV polarized electrons from an unpolarized hydrogen target, using the CEBAF Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility. A substantial sin Φ h amplitude has been measured in the distribution of the cross section asymmetry as a function of the azimuthal angle Φ h of the produced neutral pion. The dependence of this amplitude on Bjorken x and on the pion transverse momentum is extracted with significantly higher precision than previous data and is compared to model calculations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Precision measurement of the ratio of the charged kaon leptonic decay rates

A precision measurement of the ratio RK of the rates of kaon leptonic decays K+- --> e nu and K+- --> mu nu with the full data sample collected by the NA62 experiment at CERN in 2007-2008 is reported. The result, obtained by analysing ~150000 reconstructed K+- --> e nu candidates with 11% background contamination, is RK = (2.488+-0.010)*10^{-5}, in agreement with the Standard Model expectation.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

High precision measurement of Compton scattering in the 5 GeV region

The cross section of atomic electron Compton scattering $\gamma + e \rightarrow \gamma^\prime + e^\prime $ was measured in the 4.40--5.475 GeV photon beam energy region by the {\em PrimEx} collaboration at Jefferson Lab with an accuracy of 2\% and less. The results are consistent with theoretical predictions that include next-to-leading order radiative corrections. The measurements provide the first high precision test of this elementary QED process at beam energies greater than 0.1 GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Exploring the NΛ–NΣ coupled system with high precision correlation techniques at the LHC

The interaction of Λ and Σ hyperons (Y) with nucleons (N) is strongly influenced by the coupled-channel dynamics. Due to the small mass difference of the NΛ and NΣ systems, the sizable coupling strength of the NΣ↔NΛ processes constitutes a crucial element in the determination of the NΛ interaction. In this letter we present the most precise measurements on the interaction of pΛ pairs, from zero relative momentum up to the opening of the NΣ channel. The correlation function in the relative momentum space for pΛ ⊕$\bar{p}$$\bar{Λ}$ pairs measured in high-multiplicity triggered pp collisions at $\sqrt{s}$=13 TeV at the LHC is reported. The opening of the inelastic NΣ channels is visible in the extracted correlation function as a cusp-like structure occurring at relative momentum k*=289 MeV/c. This represents the first direct experimental observation of the NΣ↔NΛ coupled channel in the pΛ system. The correlation function is compared with recent chiral effective field theory calculations, based on different strengths of the NΣ↔NΛ transition potential. A weaker coupling, as possibly supported by the present measurement, would require a more repulsive three-body NNΛ interaction for a proper description of the Λ in-medium properties, which has implications on the nuclear equation of state and for the presence of hyperons inside neutron stars.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Shape polarization in the tin isotopes near N = 60 from precision g-factor measurements on short-lived 11/2 - isomers

The g factors of 11/2 - isomers in semimagic 109 Sn and 111 Sn (isomeric lifetimes $\tau$ = 2.9(3) ns and $\tau$ = 14.4(7) ns, respectively) were measured by an extension of the Time Differential Perturbed Angular Distribution technique, which uses LaBr3 detectors and the hyperfine fields of a gadolinium host to achieve precise measurements in a new regime of short-lived isomers. The results, g(11/2 - ; 109 Sn) = -0.186(8) and g(11/2 - ; 111 Sn) = -0.214(4), are significantly lower in magnitude than those of the 11/2 - isomers in the heavier isotopes and depart from the value expected for a near pure neutron h 11/2 configuration. Broken-symmetry density functional theory calculations applied to the sequence of 11/2 - states reproduce the magnitude and location of this deviation. The g(11/2 - ) values are affected by shape core polarization; the odd Oh 11/2 neutron couples to J π = 2 + , 4 + , 6 + ... configurations in the weakly-deformed effective core, causing a decrease in the g-factor magnitudes.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Precision tests of fundamental physics with η and η ' mesons

Decays of the neutral and long-lived $\eta$ and $\eta'$ mesons provide a unique, flavor-conserving laboratory to test low-energy Quantum Chromodynamics and search for new physics beyond the Standard Model. They have drawn world-wide attention in recent years and have inspired broad experimental programs in different high-intensity-frontier centers. Additionally, new experimental data will offer critical inputs to precisely determine the light quark mass ratios, $\eta$-$\eta'$ mixing parameters, and hadronic contributions to the anomalous magnetic moment of the muon. At the same time, it will provide a sensitive probe to test potential new physics. This includes searches for hidden photons, light Higgs scalars, and axion-like particles that are complementary to worldwide efforts to detect new light particles below the GeV mass scale, as well as tests of discrete symmetry violation. In this review, we give an update on theoretical developments, discuss the experimental opportunities, and identify future research needed in this field.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

A precisely substituted benzopyran targets androgen refractory prostate cancer cells through selective modulation of estrogen receptors

Dietary consumption of phytoestrogens like genistein has been linked with lower incidence of prostate cancer. The estradiol-like benzopyran core of genistein confers estrogen receptor-β (ER-β) selectivity that imparts weak anti-proliferative activity against prostate cancer cells. DL-2-[4-(2-piperidinoethoxy)phenyl]-3-phenyl-2H-1-benzopyran (BP), a SERM designed with benzopyran core, targeted androgen independent prostate cancer (PC-3) cells 14-times more potently than genistein, ~ 25% more efficiently than tamoxifen and 6.5-times more actively than ICI-182780, without forfeiting significant specificity in comparison to genistein. BP increased apoptosis (annexin-V and TUNEL labeling), arrested cell cycle, and significantly increased caspase-3 activity along with mRNA expressions of estrogen receptor (ER)-β and FasL (qPCR) in PC-3 cells. In classical ERE-luc reporter assay BP behaved as a potent ER-α antagonist and ER-β agonist. Accordingly, it decreased expression of ER-α target PS2 (P < 0.01) and increased expression of ER-β target TNF-α (P < 0.05) genes in PC-3. ER-β deficient PC-3 (siRNA-transfected) was resistant to apoptotic and anti-proliferative actions of SERMs, including stimulation of FasL expression by BP. BP significantly inhibited phosphorylation of Akt and ERK-1/2, JNK and p38 in PC-3 (immunoblotting), and thus adopted a multi-pathway mechanism to exert a more potent anti-proliferative activity against prostate cancer cells than natural and synthetic SERMs. Its precise ER-subtype specific activity presents a unique lead structure for further optimization. - Highlights: • BP with benzopyran core of genistein was identified for ER-β selective action. • BP was 14-times more potent than genistien in targeting prostate cancer cells. • It behaved as a potent ER-β agonist and ER-α antagonist in gene reporter assays. • BP's anti-proliferative action was inhibited significantly in ER-β deficient cells. • BP — a unique lead structure for further optimization.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

Sub-Sampled Imaging for STEM: Maximising Image Speed, Resolution and Precision Through Reconstruction Parameter Refinement

Sub-sampling during image acquisition in scanning transmission electron microscopy (STEM) has been shown to provide a means to increase the overall speed of acquisition while at the same time providing an efficient means to control the dose, dose rate and dose overlap delivered to the sample. In this paper, we discuss specifically the parameters used to reconstruct sub-sampled images and highlight their effect on inpainting using the beta-process factor analysis (BPFA) methodology. The selection of the main control parameters can have a significant effect on the resolution, precision and sensitivity of the final inpainted images, and here we demonstrate a method by which these parameters can be optimised for any image in STEM. As part of this paper, we also provide a link to open source code and a tutorial on its use, whereby these parameters can be tested for any datasets. When coupled with the hardware necessary to rapidly sub-sample images in STEM, this approach can have significant implications for imaging beam sensitive materials and dynamic processes.

47 OTHER INSTRUMENTATION↗
DOE OSTI2019

A designed bacterial microcompartment shell with tunable composition and precision cargo loading

Microbes often augment their metabolism by conditionally constructing proteinaceous organelles, known as bacterial microcompartments (BMCs), that encapsulate enzymes to degrade organic compounds or assimilate CO 2 . BMCs self-assemble and are spatially delimited by a semi-permeable shell made up of hexameric, trimeric, and pentameric shell proteins. Bioengineers aim to recapitulate the organization and efficiency of these complex biological architectures by redesigning the shell to incorporate non-native enzymes from biotechnologically relevant pathways. To meet this challenge, a diverse set of synthetic biology tools are required, including methods to manipulate the properties of the shell as well as target and organize cargo encapsulation. We designed and determined the crystal structure of a synthetic shell protein building block with an inverted sidedness of its N- and C-terminal residues relative to its natural counterpart; the inversion targets genetically fused protein cargo to the lumen of the shell. Moreover, the titer of fluorescent protein cargo encapsulated using this strategy is controllable using an inducible tetracycline promoter. Furthermore, these results expand the available set of building blocks for precision engineering of BMC-based nanoreactors and are compatible with orthogonal methods which will facilitate the installation and organization of multi-enzyme pathways.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

DNA Origami Incorporated into Solid-State Nanopores Enables Enhanced Sensitivity for Precise Analysis of Protein Translocations

The rapidly advancing field of nanotechnology is driving the development of precise sensing methods at the nanoscale, with solid-state nanopores emerging as promising tools for biomolecular sensing. Here, this study investigates the increased sensitivity of solid-state nanopores achieved by integrating DNA origami structures, leading to the improved analysis of protein translocations. Using holo human serum transferrin (holo-hSTf) as a model protein, we compared hybrid nanopores incorporating DNA origami with open solid-state nanopores. Results show a significant enhancement in holo-hSTf detection sensitivity with DNA origami integration, suggesting a unique role of DNA interactions beyond confinement. This approach holds potential for ultrasensitive protein detection in biosensing applications, offering advancements in biomedical research and diagnostic tool development for diseases with low-abundance protein biomarkers. Further exploration of origami designs and nanopore configurations promises even greater sensitivity and versatility in the detection of a wider range of proteins, paving the way for advanced biosensing technologies.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

In situ Infrared Spectroelectrochemistry for Understanding Structural Transformations of Precisely Defined Ions at Electrochemical Interfaces

Understanding the intrinsic properties of electroactive species at electrode-electrolyte interfaces (EEIs) is essential to the rational design of high-performance solid-state energy conversion and storage systems. In situ spectroscopy combined with cyclic voltammetry (CV) provides insights into structural changes of electroactive species at functioning EEIs. Ion soft-landing enables precisely-controlled deposition of massand charge-selected ions onto electrode surfaces thereby avoiding the contamination inherent with conventional electrode preparation techniques. In this contribution, we describe a new approach for the simultaneous electrochemical and spectroscopic characterization of soft-landed ions at operating solid-state EEIs. The technique exploits a specially-fabricated three-electrode cell that is compatible with in situ infrared reflection absorption spectroscopy (IRRAS) characterization of the softlanded ions. Keggin polyoxometalate (POM) anions, PW12O40 3-, were selected as a model system for these experiments due to their multielectron redox activity, structural stability, and well-characterized IRRAS spectrum. In situ CV measurements indicated continuous multielectron transfer processes of the soft-landed PW12O40 3- anions over a large potential range of -2.1 to -0.3 V. A distinct shift in the wavenumber of the terminal W=Ot stretching vibration in the IRRAS spectra was observed during the multielectron reduction process. The results demonstrate the capabilities of the in situ spectroelectrochemical approach for examining structural changes of well-defined electroactive species during electron transfer processes at operating solid-state EEIs.

Su, Pei↗
DOE OSTI2017

Metallic Hydrogen in Atomically Precise Gold Nanoclusters

Hydrogen–metal interaction is the foundation of many technologies and processes, but how hydrogen behaves in atomically precise gold nanoclusters remains unknown even though they have been used in hydrogenation catalysis and water splitting. Herein, we investigate how hydrogen interacts with [Au25(SR)18]q clusters and mono-atom-doped bimetallic [M1Au24(SR)18]q clusters (M = Pt, Pd, Ag, Cu, Hg, or Cd) from first principles. We find that hydrogen behaves as a metal in these clusters and contributes its 1s electron to the superatomic free-electron count. This opposite behavior compared to that of the hydride in Cu and Ag clusters allows the small hydrogen to interstitially dope the gold clusters and tune their superatomic electronic structure. The doping energetics shows that when an eight-electron superatom is formed after H doping, the binding energy of H is much stronger, while binding of H with an already eight-electron superatom is much weaker. Indeed, frontier orbitals and the HOMO–LUMO gaps of [Au25H1(SR)18]0, [Au25H2(SR)18]+, [PtAu24H2(SR)18]0, [PdAu24H2(SR)18]0, [AgAu24H(SR)18]0, and [CuAu24H(SR)18]0 all have very similar features, because they are all eight-electron superatoms. By calculating the Gibbs free energies of hydrogen adsorption, we predict that PtAu24(SR)18, PdAu24(SR)18, and center-doped CuAu24(SR)18 can be good electrocatalysts for the hydrogen evolution reaction.

Hu, Guoxiang↗
DOE OSTI2023

High-Precision Calculation of Nanoparticle (Nanocrystal) Potentials of Mean Force and Internal Energies

Thermodynamic stability assessment of nanocrystal systems requires precise free energy calculations. This study highlights the importance of meticulous control over various factors, including the thermostat, time step, potential cutoff, initial configuration, sampling method, and overall simulation duration. Free energy computations in dry (solvent-free) systems are on the order of several hundred $k_BT$ but can be obtained with consistent accuracy. However, calculation of internal energies becomes challenging, as they are typically much larger in magnitude than free energies and exhibit significant noise and reduced reliability. To address this limitation, we propose a new internal energy estimate that drastically reduces the noise. Here, we also present formulas that enable the optimization of the parameters of the harmonic bias potential for optimal convergence. Finally, we discuss the implications of these findings for the computation of free energies in nanocrystal clusters and superlattices.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

When Do Band Gap Calculations Agree with Experiments in Monolayer-Protected Cu 14 and Au 20 Atomically Precise Nanoclusters? A (TD)-DFT Comparison of HOMO–LUMO, Fundamental, Optical, and Electrochemical Energy Gaps

In view of the tremendous progress in atomically precise metal nanoclusters where electrochemical and optical energetics are routinely supported by computations to establish structure−function correlations, we explore the relationship between different protocols for measuring and computing band gaps of two distinct organic ligand-protected nanoclusters: [Cu 14 H 10 (MBN) 3 (PPh 3 ) 8 ] + and Au 20 (TBBT) 16 . Through UV/visible spectroscopy and differential pulse voltammetry, we measure optical and electrochemical band gaps in those systems. We then compare these experimentally determined gaps to HOMO−LUMO gaps, fundamental gaps, vertical excitation energies, and E o ox − E o red potentials computed using different density functional theory (DFT) or time-dependent DFT (TDDFT) methods. Specifically, in both copper and gold nanoclusters, we test the effect of truncating inert ligands from the model and compare density functionals with varying degrees of Hartree−Fock (HF) exchange from 0 to 50%, range-separated hybrids with a varying long-range tuning parameter, different correlation functionals, basis sets, and (equilibrium and nonequilibrium) continuum solvation models. Despite having different frontier orbital characters (the copper nanocluster has a metal-to-ligand charge transfer character while the gold nanocluster has metal-centered frontier orbitals), both nanoclusters display a similar sensitivity of the HOMO−LUMO gap to the HF exchange that is partially mitigated when computing the fundamental, optical, and electrochemical gaps. Other factors, such as the nature of the correlation functional, basis set, and geometry relaxation, have a considerably smaller effect on computed band gaps in these systems. Overall, this work provides guidelines for factors of varied importance for correlating computed and experimental band gap values.

Chemical calculations↗
DOE OSTI2025

Investigating Morphology and Diffusion in Simulations of Precise Anion-Conducting Polymers

Using atomistic molecular dynamics simulations, we investigate the morphology and transport properties of a new class of polymers which are functionalized with quaternary ammonium groups for use as anion exchange membranes. The polymers are precision polyolefins with either a trimethylammonium (p5CNMe3) or a dimethyl-hexyl ammonium (p5CNMe2Hx) pendant group at every fifth carbon along a polyethylene backbone. Simulations are performed at hydration levels of 5, 10, 15, and 20 water molecules per ammonium group. The hydrated polymers form nanoscale, percolated hydrophilic domains (water channels) in the hydrophobic polymer matrix that become wider with increasing water content. Water and hydroxide anion diffusion coefficients also increase with increasing water content. The morphology of the water domains is similar in both polymers, while the diffusion coefficients are somewhat lower in p5CNMe2Hx at fixed water content. Furthermore, the diffusion coefficients in both polymers fall on the same curve as a function of the fractal dimension of the percolated water channels, which appears to be a useful scalar measure of the effects of the nanoscale morphology on water and hydroxide anion transport.

Anion exchange membrane↗
DOE OSTI2016

Role of Periodicity and Acid Chemistry on the Morphological Evolution and Strength in Precise Polyethylenes

We report herein the morphology evolution under tensile deformation for strictly linear polyethylenes with associating functional groups. In situ X-ray scattering measurements during elongation reveal that periodic acid group placement along the backbone is required to form hierarchical layered morphologies that lead to strain hardening. This phenomenon was observed in both semicrystalline and amorphous precise acid polyethylenes with acrylic, geminal acrylic, and phosphonic acids. Polymers with nonperiodic (pseudorandom) acid placement fail to form layered morphologies and instead retain a liquidlike distribution of acid aggregates. Acid chemistry and acid concentration influence morphological evolution in both periodic and nonperiodic polymers predominately through the modification of T g and percent crystallinity, which subsequently impact the mechanical properties. Our results indicate that hierarchical acid-rich layered structures, commensurate with improved mechanical properties, form in polymers with strictly periodic chemical structures and sufficient chain mobility for chain alignment during elongation.

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

Heterogeneous chain dynamics and aggregate lifetimes in precise acid-containing polyethylenes: Experiments and simulations

Melt state dynamics for a series of strictly linear polyethylenes with precisely spaced associating functional groups were investigated. The periodic pendant acrylic acid groups form hydrogen-bonded acid aggregates within the polyethylene (PE) matrix. The dynamics of these nanoscale heterogeneous morphologies were investigated from picosecond to nanosecond timescales by both quasi-elastic neutron scattering (QENS) measurements and fully atomistic molecular dynamics (MD) simulations. Two dynamic processes were observed. The faster dynamic processes which occur at the picosecond timescales are compositionally insensitive and indicative of spatially restricted local motions. The slower dynamic processes are highly composition dependent and indicate the structural relaxation of the polymer backbone. Higher acid contents, or shorter PE spacers between pendant acid groups, slow the structural relaxation timescale and increase the stretching parameter (β) of the structural relaxation. Additionally, the dynamics of specific hydrogen atom positions along the backbone correlate structural heterogeneity imposed by the associating acid groups with a mobility gradient along the polymer backbone. At time intervals (<2 ns), the mean-squared displacements for the four methylene groups closest to the acid groups are up to 10 times smaller than those of methylene groups further from the acid groups. At longer timescales acid aggregates rearrange and the chain dynamics of the slow, near-aggregate regions and the faster bridge regions converge, implying a characteristic timescale for the passage of chains between aggregates. As a result, the characterization of the nanoscale chain dynamics in these associating polymer systems both provides validation of simulation force fields and provides understanding of heterogeneous chain dynamics in associating polymers.

36 MATERIALS SCIENCE↗