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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Theory of hysteresis during electron heating of electromagnetic wave scattering by self-organized dust structures in complex plasmas

Dust structuring is a natural and universal process in complex plasmas. The scattering of electromagnetic waves by dust structures is governed by the factor of coherency, i.e., the total number of coherent electrons in a single structure. In the present paper, we consider how the factor of coherency changes due to additional pulse electron heating and show that it obeys a hysteresis. After the end of the pulse heating, the scattering intensity differs substantially from that before heating. There are three necessary conditions for scattering hysteresis: first, the radiation wavelength should be larger than the pattern (structure) size; second, the total number of coherent electrons confined by the structure should be large; and third, the heating pulse duration should be shorter than the characteristic time of dust structure formation. We present the results of numerical calculations using existing models of self-consistent dust structures with either positively or negatively charged dust grains. It is shown that, depending on the grain charge and the ionization rate, two types of hysteresis are possible: one with a final increase of the scattering and the other with a final decrease of the scattering. It is suggested that the hysteresis of coherent scattering can be used as a tool in laboratory experiments and that it can be a basic mechanism explaining the observed hysteresis in radar scattering by noctilucent clouds during active experiments on electron heating in mesosphere.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Scattering matrix pole expansions for complex wave numbers in R -matrix theory

In this followup article to Ducru et al., we establish new results on scattering matrix pole expansions for complex wave numbers in R-matrix theory. In the past, two branches of theoretical formalisms emerged to describe the scattering matrix in nuclear physics: R-matrix theory and pole expansions. The two have been quite isolated from one another. Recently, our study of Brune's alternative parametrization of R-matrix theory has shown the need to extend the scattering matrix (and the underlying R-matrix operators) to complex wave numbers. Two competing ways of doing so have emerged from a historical ambiguity in the definitions of the shift S and penetration P functions: the legacy Lane and Thomas's “force closure” approach versus analytic continuation (which is the standard in mathematical physics). The R-matrix community has not yet come to a consensus as to which to adopt for evaluations in standard nuclear data libraries, such as ENDF. Here, in this article, we argue in favor of analytic continuation of R-matrix operators. We bridge R-matrix theory with the Humblet-Rosenfeld pole expansions, and discover new properties of the Siegert-Humblet radioactive poles and widths, including their invariance properties to changes in channel radii a c . We then show that analytic continuation of R-matrix operators preserves important physical and mathematical properties of the scattering matrix—canceling spurious poles and guaranteeing generalized unitarity—while still being able to close channels below thresholds.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

From weak antilocalization to Kondo scattering in a magnetic complex oxide interface

Quantum corrections to electrical resistance can serve as sensitive probes of the magnetic landscape of a material. For example, interference between time-reversed electron paths gives rise to weak localization effects, which can provide information about the coupling between spins and orbital motion, while the Kondo effect is sensitive to the presence of spin impurities. In this work, we use low-temperature magnetotransport measurements to reveal a gradual transition from weak antilocalization (WAL) to Kondo scattering in the quasi-two-dimensional electron gas formed at the interface between SrTiO 3 and the Mott insulator NdTiO 3 . This transition occurs as the thickness of the NdTiO 3 layer is increased. Analysis of the Kondo scattering and WAL points to the presence of atomic-scale magnetic impurities coexisting with nanoscale magnetic regions that affect transport via a strong magnetic exchange interaction. This leads to distinct magnetoresistance behaviors that can serve as a sensitive probe of magnetic properties in two dimensions.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Synthesis and characterization of monodisperse, mesoporous, and magnetic sub-micron particles doped with a near-infrared fluorescent dye

Recently, multifunctional silica nanoparticles have been investigated extensively for their potential use in biomedical applications. We have prepared sub-micron monodisperse and stable multifunctional mesoporous silica particles with a high level of magnetization and fluorescence in the near infrared region using an one-pot synthesis technique. Commercial magnetite nanocrystals and a conjugated-NIR-dye were incorporated inside the particles during the silica condensation reaction. The particles were then coated with polyethyleneglycol to stop aggregation. X-ray diffraction, N{sub 2} adsorption analysis, TEM, fluorescence and absorbance measurements were used to structurally characterize the particles. These mesoporous silica spheres have a large surface area (1978 m{sup 2}/g) with 3.40 nm pore diameter and a high fluorescence in the near infrared region at {lambda}=700 nm. To explore the potential of these particles for drug delivery applications, the pore accessibility to hydrophobic drugs was simulated by successfully trapping a hydrophobic ruthenium dye complex inside the particle with an estimated concentration of 3 wt%. Fluorescence imaging confirmed the presence of both NIR dye and the post-grafted ruthenium dye complex inside the particles. These particles moved at approximately 150 {mu}m/s under the influence of a magnetic field, hence demonstrating the multifunctionality and potential for biomedical applications in targeting and imaging. - Graphical Abstract: Hydrophobic fluorescent Ruthenium complex has been loaded into the mesopores as a surrogate drug to simulate drug delivery and to enhance the multifunctionality of the magnetic NIR emitting particles. Highlights: > Monodisperse magnetic mesoporous silica particles emitting in the near infrared region are obtained in one-pot synthesis. > We prove the capacity of such particles to uptake hydrophobic dye to mimic drug loading. > Loaded fluorescent particles can be moved under a magnetic field in a microfluidic device.

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

Second order Møller-Plesset and coupled cluster singles and doubles methods with complex basis functions for resonances in electron-molecule scattering

The method of complex basis functions is applied to molecular resonances at correlated levels of theory. Møller-Plesset perturbation theory at second order and equation-of-motion electron attachment coupled-cluster singles and doubles (EOM-EA-CCSD) methods based on a non-Hermitian self-consistent-field reference are used to compute accurate Siegert energies for shape resonances in small molecules including N 2 - , CO - , CO 2 - , and CH 2 O - . Analytic continuation of complex θ-trajectories is used to compute Siegert energies, and the θ-trajectories of energy differences are found to yield more consistent results than those of total energies. Furthermore, the ability of such methods to accurately compute complex potential energy surfaces is investigated, and the possibility of using EOM-EA-CCSD for Feshbach resonances is explored in the context of e-helium scattering.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Mechanism of Charge Transport in Cobalt and Iron Phthalocyanine Thin Films Grown by Molecular Beam Epitaxy

Cobalt phthalocyanine (CoPc), iron phthalocyanine (FePc) and their composite (CoPc-FePc) films have been grown by molecular beam epitaxy (MBE). Grazing incidence X-ray diffraction (GIXRD) and scanning electron microscope (SEM) studies showed that composite films has better structural ordering compared to individual CoPc and FePc films. The temperature dependence of resistivity (in the temperature range 25 K- 100 K) showed that composite films are metallic, while individual CoPc and FePc films are in the critical regime of metal-to-insulator (M-I) transition The composite films show very high mobility of 110 cm{sup 2} V{sup -1} s{sup -1} at room temperature i.e. nearly two order of magnitude higher compared to pure CoPc and FePc films.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Parameterization of Direct and Doorway Processes in R-Matrix Formalism

R-matrix formalism is extended beyond compound nuclear (CN) resonant reactions to include parameterization of direct as well as doorway processes. Direct processes in the R-matrix exterior are parameterized by a unitary matrix that introduces mixing among wave function coefficients of the incoming and outgoing wave function components at the R-matrix channel surface. Doorway processes are parameterized by separating the Hilbert space of the interior R-matrix region into its doorway and CN subspaces, from which doorway state eigenenergies, reduced width amplitudes, and the strengths of their coupling to CN levels appear as new R-matrix parameters. Parameterization of generalized as well as the conventional Reich–Moore approximation for eliminated capture channels in the presence of direct, doorway, and CN processes is presented along with a complex-valued scattering length with contributions from direct, doorway, and CN capture processes. Derivation of Brune’s alternative R-matrix parameters is extended to include doorway states. This work suggests how R-matrix formalism could be extended further by adopting the concepts from related reaction formalisms.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2010

A new polymorph of Ba(AsO{sub 3}OH): Synthesis, crystal structure and vibrational spectra

A new monoclinic polymorph of Ba(AsO{sub 3}OH) was synthesized under hydrothermal conditions. It represents a previously unknown structure type. Its crystal structure was determined from a racemic twin using single-crystal X-ray diffraction data collected at 120 and 293 K [space group P2{sub 1}, a=7.2149(14)/7.2370(2), b=7.7028(15)/7.7133(2), c=21.7385(43)/21.8079(5) A, {beta}=95.95(3)/96.073(1){sup o}, V=1201.6(4)/1210.51(5) A{sup 3}, Z=12]. The crystal structure of P2{sub 1}-Ba(AsO{sub 3}OH) has a layered character and is built up of four types of regularly alternating layers parallel to (0 0 1). Every AsO{sub 3}OH tetrahedron is chelating to two Ba atoms and bridged by another two Ba atoms. Each OH group acts as hydrogen bond donor toward the oxygen atoms positioned in the same or adjacent layers. Although the H atoms could not be located, no ambiguities are present in the hydrogen-bonding scheme. Single-crystal vibrational spectroscopy (FTIR and Raman) was used to describe the vibrational behavior of the hydrogen bond system; particularly the spectroscopic manifestation of the very short and short hydrogen bonds (2.462(7)-2.575(7) A). In order to complement spectroscopic data on protonated orthoarsenates, infrared spectra of triclinic F1-bar -Sr(AsO{sub 3}OH) and the orthorhombic variety of Pbca-Ba(AsO{sub 3}OH) were recorded and discussed. Furthermore, structural features of other alkaline earth hydrogen arsenates are discussed. -- Graphical Abstract: Mesh type and topological structure of the cation layers seen along [0 0 1]; a-axis vertical, b-axis horizontal. A trace of the unit cell is drawn for reference. Display Omitted

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

Simulating the Daylight Performance of Complex Fenestration Systems Using Bidirectional Scattering Distribution Functions within Radiance

We describe two methods which rely on bidirectional scattering distribution functions (BSDFs) to model the daylighting performance of complex fenestration systems (CFS), enabling greater flexibility and accuracy in evaluating arbitrary assemblies of glazing, shading, and other optically-complex coplanar window systems. Two tools within Radiance enable a) efficient annual performance evaluations of CFS, and b) accurate renderings of CFS despite the loss of spatial resolution associated with low-resolution BSDF datasets for inhomogeneous systems. Validation, accuracy, and limitations of the methods are discussed.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2025

Selective deuteration of an RNA:RNA complex for structural analysis using small-angle scattering

The structures of RNA:RNA complexes regulate many biological processes. Despite their importance, protein-free RNA:RNA complexes represent a tiny fraction of experimentally determined structures. Here, we describe a joint small-angle X-ray and neutron scattering (SAXS/SANS) approach to structurally interrogate conformational changes in a model RNA:RNA complex. Using SAXS, we measured the solution structures of the individual RNAs and of the overall RNA:RNA complex. With SANS, we demonstrate, as a proof of principle, that isotope labeling and contrast matching (CM) can be combined to probe the bound state structure of an RNA within a selectively deuterated RNA:RNA complex. Furthermore, we show that experimental scattering data can validate and improve predicted AlphaFold 3 RNA:RNA complex structures to reflect its solution structure. In conclusion, our work demonstrates that in silico modeling, SAXS, and CM-SANS can be used in concert to directly analyze conformational changes within RNAs when in complex, enhancing our understanding of RNA structure in functional assemblies.

HIV-1 dimerization initiation site↗
DOE OSTI2020

Understanding the Structure and Dynamics of Complex Biomembrane Interactions by Neutron Scattering Techniques

The membrane is one of the key structural materials of biology at the cellular level. Composed predominantly of a bilayer of lipids with embedded and bound proteins, it defines the boundaries of the cell and many organelles essential to life and therefore is involved in almost all biological processes. Membrane-specific interactions, such as drug binding to a membrane receptor or the interactions of an antimicrobial compound with the lipid matrix of a pathogen membrane, are of interest across the scientific disciplines. Herein we present a review, aimed at nonexperts, of the major neutron scattering techniques used in membrane studies: small-angle neutron scattering, neutron membrane diffraction, neutron reflectometry, quasielastic neutron scattering, and neutron spin echo. Neutron scattering techniques are well suited to studying biological membranes. The nondestructive nature of cold neutrons means that samples can be measured for long periods without fear of beam damage from ultraviolet, electron, or X-ray radiation, and neutron beams are highly penetrating, thus offering flexibility in samples and sample environments. Most important is the strong difference in neutron scattering lengths between the two most abundant forms of hydrogen, protium and deuterium. Changing the relative amounts of protium/deuterium in a sample allows the production of a series of neutron scattering data sets, enabling the observation of differing components within complex membrane architectures. This approach can be as simple as using the naturally occurring neutron contrast between different biomolecules to study components in a complex by changing the solution H 2 O/D 2 O ratio or as complex as selectively labeling individual components with hydrogen isotopes. This review presents an overview of each experimental technique with the neutron instrument configuration, related sample preparation and sample environment, and data analysis, highlighted by a special emphasis on using prominent neutron contrast to understand structure and dynamics. This review gives researchers a practical introduction to the often enigmatic suite of neutron beamlines, thereby lowering the barrier to taking advantage of these large-facility techniques to achieve new understandings of membranes and their interactions with other molecules.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2010

Syntheses, structures and properties of silver(I) complexes with flexible 1,3,5-tris(pyridylmethoxyl)benzene ligands

Five new silver(I) complexes [Ag{sub 2}(L{sub 2}){sub 2}](BF{sub 4}){sub 2}.CH{sub 3}CN.CH{sub 3}OH (1), [Ag(L{sub 2})(CF{sub 3}SO{sub 3})] (2), [Ag(L{sub 3})]ClO{sub 4}.CH{sub 3}OH (3), [Ag{sub 2}(L{sub 3}){sub 2}](CF{sub 3}SO{sub 3}){sub 2}.CH{sub 3}CN.CH{sub 3}OH.H{sub 2}O (4) and [Ag(L{sub 3})]PF{sub 6}.2CH{sub 3}CN (5) [L{sub 2}=1,3,5-tris(2-pyridylmethoxyl)benzene, L{sub 3}=1,3,5-tris(3-pyridylmethoxyl)benzene] were synthesized and characterized by single crystal X-ray diffraction analyses. In complexes 1-5, ligands L{sub 2} and L{sub 3} show different conformations and act as three-connectors, while the Ag(I) atom serves as three-connecting node to result in the formation of 2D and 3D frameworks. Complexes 1 and 2 with different counteranions have similar 2D network structure with the same (4,8{sup 2}) topology. Complex 3 has a 3D structure with (10,3)-a topology while complexes 4 and 5 have the same 2D (6,3) topological structure. The results showed that the structure of organic ligands and counteranions play subtle but important role in determining the structure of the complexes. In addition, the photoluminescence and anion-exchange properties of the complexes were investigated in the solid state at room temperature. - Graphical abstract: Five new silver(I) coordination frameworks with different topology were obtained and their structures were determined by single crystal X-ray diffraction studies. The influence of counteranion and ligand on the structure of complexes was discussed, the photoluminescence and anion-exchange properties were reported.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

Application of the complex-scaling method to few-body scattering

A formalism based on the complex-scaling method is developed for solving the few-particle scattering problem, in terms of bound state boundary conditions. Several applications are presented to demonstrate the efficiency of the method for computing the elastic and three-body breakup reactions in systems described by Hamiltonians which may include both short- and long-range interactions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗