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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 1,729 records · Page 96
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Multi-omics analysis reveals the dynamic interplay between Vero host chromatin structure and function during vaccinia virus infection

The genome folds into complex configurations and structures thought to profoundly impact its function. The intricacies of this dynamic structure-function relationship are not well understood particularly in the context of viral infection. To unravel this interplay, here we provide a comprehensive investigation of simultaneous host chromatin structural (via Hi-C and ATAC-seq) and functional changes (via RNA-seq) in response to vaccinia virus infection. Over time, infection significantly impacts global and local chromatin structure by increasing long-range intra-chromosomal interactions and B compartmentalization and by decreasing chromatin accessibility and inter-chromosomal interactions. Local accessibility changes are independent of broad-scale chromatin compartment exchange (~12% of the genome), underscoring potential independent mechanisms for global and local chromatin reorganization. While infection structurally condenses the host genome, there is nearly equal bidirectional differential gene expression. Despite global weakening of intra-TAD interactions, functional changes including downregulated immunity genes are associated with alterations in local accessibility and loop domain restructuring. Therefore, chromatin accessibility and local structure profiling provide impactful predictions for host responses and may improve development of efficacious anti-viral counter measures including the optimization of vaccine design.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Resilience of the Aurivillius structure upon La and Cr doping in a Bi 5 Ti 3 FeO 15 multiferroic

Here, combining the experimental techniques of high-resolution X-ray diffraction, magnetometry, specific heat measurement, and X-ray photoelectron, Raman and dielectric spectroscopy techniques, we have studied the influence of La and Cr doping on the crystal structure and magnetism of the room temperature Aurivillius multiferroic Bi 5 Ti 3 FeO 15 by investigating the physical properties of (Bi 4 La)Ti 3 FeO 15 and Bi 5 Ti 3 (Fe 0.5 Cr 0.5 )O 15 . The parent (Bi 5 Ti 3 FeO 15 ) and the doped ((Bi 4 La)Ti 3 FeO 15 and Bi 5 Ti 3 (Fe 0.5 Cr 0.5 )O 15 ) compounds crystallize in the A2 1 am space group, which is confirmed through our analysis of high-resolution synchrotron X-ray diffraction data obtained on phase-pure polycrystalline powders. We determined the oxidation states of the metal atoms in the studied compounds as Fe 3+ , Ti 4+ , Cr 3+ , and La 3+ through the analysis of X-ray photoelectron spectroscopy data. The magnetic susceptibilities of the three compounds are marked by the absence of a long-range ordered ground state, but dominated by superparamagnetic clusters with dominant antiferromagnetic interactions. This signature of short-range magnetism is also seen in specific heat as a low temperature enhancement which is suppressed upon the application of external magnetic fields up to 8 T. Our dielectric spectroscopy experiments showed that the three studied compounds display similar features in the dielectric constant measured as a function of frequency. However, upon doping La at the Bi site, the width of the ferroelectric hysteresis loop increases for (Bi 4 La)Ti 3 FeO 15 compared to that of the parent compound Bi 5 Ti 3 FeO 15 , and with Cr doping, Bi 5 Ti 3 (Fe 0.5 Cr 0.5 )O 15 becomes a leaky dielectric. The resilience of the Aurivillius crystal structure towards doping of La at the Bi site and Cr at the Fe site is clearly seen in the bulk properties of magnetic susceptibility, specific heat and the average crystal structure. The relevance of changes in the local structure is evident from our Raman spectroscopy and X-ray pair distribution function studies.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Solvation directed morphological control in metal oxide nanostructures

The development of structural hierarchy on various length scales during the crystallization process is ubiquitous in biological systems and minerals and is common in synthetic nanomaterials. The driving forces for the formation of complex architectures range from local interfacial interactions, that modify interfacial speciation, local supersaturation, and nucleation barriers, to macroscopic interparticle forces. Although it is enticing to interpret the formation of hierarchical architectures as the assembly of independently nucleated building blocks, crystallization pathways often follow monomer-by-monomer addition with structural complexity arising from interfacial chemical coupling and strongly correlated fluctuation dynamics in the electric double layers. Here, we show that the development of structural hierarchy through heterogeneous nucleation is driven by dipolar and solvation forces. Specifically, coupled simulations and experimental studies revealed that dipole build-up along the slow growth direction can trigger twinning and the development of branched architectures. Enthalpic solvation interactions were shown to either enhance or reduce the dipole moment of the nanoparticles and, thereby, control crystal morphology and architecture. The systematic studies of chemical coupling between different solvents and undercoordinated surface atoms of the growing nanocrystals revealed the mechanism of dimensionality control and the development of structural hierarchy without ligands or structure-directing agents.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2010

New Results on Baryon Spectroscopy from MAMI

An overview of the MAMI-C electron accelerator facility (E{sub 0} = 1.6 GeV) and the experimental setups of the A1 and A2 collaborations for electro- and photoproduction reactions is given. Several experimental results and their interpretations for baryon spectroscopy are discussed. The topics presented here are the beam-helicity asymmetry I{center_dot} for {pi}{pi} photoproduction in the second resonance region, the photoproduction of {pi}{sup 0{eta}} up to beam energies of {omega} = 1.4 GeV as a way to study the {Delta}(1700)D{sub 33} baryon, and polarisation observables in h electro- and photoproduction in order to investigate an unexpected s-d-wave phase shift and its possible implications for the nature of the S{sub 11}(1535) resonance.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Photoproduction of the {Lambda}*(1520) Hyperon

The photoproduction of the {Lambda}*(1520) on both the proton and neutron have been studied by using the CLAS eg3 run data set. The reactions are {gamma}d{yields}K{sup +{Lambda}}*(n) and {gamma}d{yields}K{sup 0{Lambda}}*(p) with {Lambda}*{yields}pK{sup -}. Preliminary total and differential cross sections have been extracted in the photon energy region 1.75 GeV<E{sub {gamma}<}5.50 GeV. This is the first time that the photoproduction of {Lambda}*(1520) on the neutron is reported, and we will extend the results on the proton to higher energies than in previous studies.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

On {eta} and {pi}{sup 0}{eta} photoproduction

The recently discovered enhancement of {eta} photoproduction on the quasi-free neutron at energies around {radical}(s){approx}1.67 GeV is addressed within an SU(3) coupled channels model. The K{Sigma} threshold plays a significant role and the quasi-free cross sections on proton and neutron, {sigma}{sub n} and {sigma}{sub p}, can be quantitatively explained. For the reaction {gamma}-vectorp{yields}{pi}{sup 0}{eta}p, we evaluate the polarization observables I{sup S} and I{sup C} from a chiral unitary amplitude developed earlier. The I{sup S} and I{sup C} observables have been recently measured for the first time by the CBELSA/TAPS collaboration. We show the significance of the {Delta}(1700)D{sub 33} resonance and its S-wave decay into {eta}{Delta}(1232) which further confirms the dynamical nature of this resonance.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

New developments for a chiral effective theory of nuclear matter

We report on the recent developments of a new effective field theory for nuclear matter. We present first the nuclear matter chiral power counting that takes into account both short- and long-range inter-nucleon interactions. It also identifies non-perturbative strings of diagrams, related to the iteration of nucleon-nucleon interactions, which have to be re-summed. The methods of unitary chiral perturbation theory has been shown to be a useful tool in order to perform those resummations and provide sensible results up-to next-to-leading order for the ground state energy per particle of nuclear matter, in-medium chiral quark condensate and the self-energy and axial-vector couplings of the pion.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Kaon Production Off the Nucleon

We have studied the weak kaon production off the nucleon induced by neutrinos at the low and intermediate energies. The studied mechanisms are the main source of kaon production for neutrino energies up to 1.2 to 1.5 GeV for the various channels and the cross sections are large enough to be amenable to be measured by experiments such as MINERvA and T2K.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Pion photoproduction in a dynamical coupled-channel model

Pion photoproduction reactions are investigated in a dynamical coupled-channel approach based on the Juelich {pi}N model, which presently includes the hadronic {pi}N and {eta}N stable channels as well as the {pi}{Delta}, {sigma}N and {rho}N effective channels. This model has been quite successful in the description of {pi}N{yields}{pi}N scattering for center-of-mass energies up to 1.9 GeV. The full pion photoproduction amplitude is constructed to satisfy the generalized Ward-Takahashi identity and hence, it is fully gauge invariant. The calculated differential cross sections and photon spin asymmetries up to 1.65 GeV center-of-mass energy for the reactions {gamma}p{yields}{pi}{sup +}n, {gamma}p{yields}{pi}{sup 0}p and {gamma}n{yields}{pi}{sup -}p are in good agreement with the experimental data.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Juelich-Georgia meson-baryon model

Meson-baryon scattering and photon-nucleon reactions are described in a coupled-channel approach for energies below 2 GeV. Poles and residues of the reaction amplitudes are obtained by analytical continuation. The dependence of the resonance poles on the pion mass is investigated.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Differential cross sections and spin density matrix elements for {gamma}p {yields} {phi}p from CLAS

Preliminary differential cross-sections and the {rho}{sub MM'}{sup 0} spin density matrix elements (SDME) for the reaction {gamma}{rho} {yields} {phi}p for both charged-({phi} {yields} K{sup +}K-) and neutral-mode ({phi} {yields} K{sub L}{sup 0}K{sub S}{sup 0}) topologies obtained from CLAS are presented. Our kinematic coverage is from near production threshold ({radical}(s){approx}1.97 GeV) to ({radical}(s) 2.84 GeV), with a wide coverage in the production angle. As seen in previous LEPS results, the differential cross-sections show a localized 'bump' between ({radical}(s){approx}2 and 2.2 GeV that is not expected from a simple Pomeron exchange picture. Comparisons between the charged- and neutral-mode results and possible effects from the K{sup +}{Lambda}(1520) channel are discussed. Our SDME results confirm the well-known deviations from t-channel helicity conservation (TCHC) for Pomeron exchange, but s-channel helicity conservation (SCHC) is also seen to be broken.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

From hadrons to nuclei with charm and bottom flavors

We discuss new exotic nuclei which contain D-bar and B mesons. As simplest systems, we consider D-bar(B) bound systems with one nucleon and two nucleons. With respecting to the heavy quark symmetry, we derive the one pion exchange potential as a long range force as an interaction between D-bar(B) meson and nucleon. We solve the Schroedinger equation with coupled channels, and investigate the D-barN (BN) bound states. We further discuss the possibility of existence of D-barNN (BNN). We discuss the possible observations of these exotic states in experiments in accelerator facilities.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Neutrino Induced Pion Production at SciBooNE

We report measurements of neutrino induced pion production processes on carbon target with an average energy of {approx}0.8 GeV by SciBooNE experiment at Fermilab. These measurements are important inputs for current and future accelerator-based neutrino oscillation experiments in the interpretation of neutrino oscillation signals.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Strange particle production at low and intermediate energies

The weak kaon production off the nucleon induced by neutrinos and antineutrinos is studied at low and intermediate energies of interest for some ongoing and future neutrino oscillation experiments. We develop a microscopical model based on the SU(3) chiral Lagrangians. The studied mechanisms are the main source of kaon production for neutrino energies up to 2 GeV for the various channels and the cross sections are large enough to be amenable to be measured by experiments such as Minerva, T2K and NOvA.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Hard x-ray (>100 keV) imager to measure hot electron preheat for indirectly driven capsule implosions on the NIF

We have fielded a hard x-ray (>100 keV) imager with high aspect ratio pinholes to measure the spatially resolved bremsstrahlung emission from energetic electrons slowing in a plastic ablator shell during indirectly driven implosions at the National Ignition Facility. These electrons are generated in laser plasma interactions and are a source of preheat to the deuterium-tritium fuel. First measurements show that hot electron preheat does not limit obtaining the fuel areal densities required for ignition and burn.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

Rare B{sub (s)} decays in the standard model and in a scenario with two universal extra dimensions

I consider the exclusive B{yields}K*{gamma}, B{yields}K*{sub 2}{gamma}, B{sub s}{yields}{phi}{gamma} and B{yields}K{eta}{sup ( Prime )}{gamma} radiative decays in the Standard Model and in a scenario with two universal extra dimensions compactified on a chiral square. Computed branching fractions depend on 1/R, the size of the extra dimensions, so that comparison with available data allows to put bounds on such a parameter. The most stringent bound comes from the mode B*{sup 0}{yields}K*{sup 0}{gamma} and reads: 1/R > 710 GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Nuclear pairing from bare interaction: Two and three-body chiral forces

In a recent paper the {sup 1}S{sub 0} pairing gap in isospin-symmetric nuclear matter and finite nuclei has been investigated starting from the chiral nucleon-nucleon potential at the N{sup 3}LO order in the two-body sector and the N{sup 2}LO order in the three-body sector. To include realistic nuclear forces in RHB (Relativistic Hartree Bolgoliubov) calculations we relied on a separable representation of the pairing interaction. In this paper we would like to show recent results concerning isotonic chains with N= 28,50,82.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2012

Antikaons in the extended relativistic mean-field models for neutron star

We review the role of antikaons in recent versions of relativistic mean field models and focus on the interactions in which all parameters are obtained by fitting finite nuclear data and successfully applied to reproduce a variety of nuclear and neutron star (NS) properties. We show that the recently observed 1.97 solar mass NS can be explained in three ways: (i) A stiffer EoS with both antikaons (K{sup -}, K-bar {sup 0}), (ii) a relatively softer EoS with K{sup -} and (iii) a softer EoS with nucleon phase only.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗