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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 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

TrxR2 deficiencies promote chondrogenic differentiation and induce apoptosis of chondrocytes through mitochondrial reactive oxygen species

Thioredoxin reductase 2 (TrxR2) is a selenium (Se) containing protein. Se deficiency is associated with an endemic osteoarthropathy characterized by impaired cartilage formation. It is unclear whether TrxR2 have roles in cartilage function. We examined the effects of TrxR2 on chondrogenic ATDC5 cells through shRNA-mediated gene silencing of TrxR2. We demonstrated TrxR2 deficiencies could enhance chondrogenic differentiation and apoptosis of ATDC5 cells. TrxR2 deficiencies increased accumulation of cartilage glycosaminoglycans (GAGs) and mineralization. TrxR2 deficiencies also stimulated expression of extracellular (ECM) gene including Collagen II and Aggrecan. The enhanced chondrogenic properties were further confirmed by activation of Akt signaling which are required for chondrogenesis. In addition, TrxR2 deficiencies promoted chondrocyte proliferation through acceleration of cell cycle progression by increase in both S and G2/M phase cell distribution accompanied with induction of parathyroid hormone-related protein (PTHrP). Moreover, TrxR2 deficiencies induced chondrocyte death via apoptosis and increased cell sensitivity to exogenous oxidative stress. Furthermore, TrxR2 deficiencies induced emission of mitochondrial reactive oxygen species (ROS) without alteration of mitochondrial membrane potential and intracellular ATP content. Finally, treatment of TrxR2 deficiency cells with N-acetylcysteine (NAC) inhibited mitochondrial ROS production and chondrocyte apoptosis. NAC also prevented chondrogenic differentiation of TrxR2 deficiency cells by suppression of ECM gene expression, GAGs accumulation and mineralization, as well as attenuation of Akt signaling. Thus, TrxR2-mediated mitochondrial integrity is indispensable for chondrogenic differentiation of ATDC5 cells. TrxR2 deficiency-induced impaired proliferation and death of chondrocytes may be the pathological mechanism of the osteoarthropathy due to Se deficiency. Notably, this study also uncover the roles of mitochondrial ROS which could stimulate cartilage ECM synthesis that offer novel insights for development of therapeutic agent to prevent cartilage degeneration in human disease. - Highlights: • TrxR2 deficiencies enhance chondrogenic differentiation. • TrxR2 deficiencies stimulate chondrocyte proliferation. • TrxR2 deficiencies induce chondrocyte apoptosis. • TrxR2 deficiencies increase emission of mitochondrial ROS. • Mitochondrial ROS regulate chondrocyte proliferation, differentiation, and apoptosis.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Nanoscale Three-Dimensional Microstructural Characterization of an Sn-Rich Solder Alloy Using High-Resolution Transmission X-Ray Microscopy (TXM)

Abstract Three-dimensional (3D) nondestructive microstructural characterization was performed using full-field transmission X-ray microscopy on an Sn-rich alloy, at a spatial resolution of 60 nm. This study highlights the use of synchrotron radiation along with Fresnel zone plate optics to perform absorption contrast tomography for analyzing nanoscale features of fine second phase particles distributed in the tin matrix, which are representative of the bulk microstructure. The 3D reconstruction was also used to quantify microstructural details of the analyzed volume.

3D reconstruction↗
DOE OSTI2022

Comment on “Microhydration of Biomolecules: Revealing the Native Structures by Cold Ion IR Spectroscopy”

This paper presents a re-examination of the conclusions of a study reported in The Journal of Physical Chemistry Letters (Saparbaev et al., 2021, 12, 907) that compared the structure of microsolvated ions formed by electrospray ionization to those formed in the gas-phase via a previously published cryogenic ion trap approach. We conducted additional experiments that clearly show that most of the observed differences in the IR spectra can be accounted for by considering the different spectroscopic action schemes used to obtain them. In particular, the presence of the D 2 -tag induces shifts in some of the N-H and O-H peaks which need to be carefully considered before comparing spectra. Furthermore, once these spectral effects are taken into account, we show that both clustering approaches yields similar clusters structures for the small GlyH + (H 2 O)n species. Using unimolecular reaction rate theory, we also show that for the small complexes considered here, only the gas-phase equilibrium distribution of conformers should be expected in both experimental approaches. In addition, the barrier heights necessary to kinetically trap high-energy conformers at 298K is explored using a series of model polyalanine chains.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Gas-Phase Temperature Mapping of Evaporating Microdroplets

Evaporation is a ubiquitous and complex phenomenon of importance to many natural and industrial systems. Evaporation occurs when molecules near the free interface overcome intermolecular attractions with the bulk liquid. As molecules escape the liquid phase, heat is removed, causing evaporative cooling. The influence of evaporative cooling on inducing a temperature difference with the surrounding atmosphere as well as within the liquid is poorly understood. Here, we develop a technique to overcome past difficulties encountered during the study of heterogeneous droplet evaporation by coupling a piezo-driven droplet generation mechanism to a controlled micro-thermocouple to probe microdroplet evaporation. The technique allowed us to probe the gas-phase temperature distribution using a micro-thermocouple (50 μm) in the vicinity of the liquid–vapor interface with high spatial (±10 μm) and temporal (±100 ms) resolution. We experimentally map the temperature gradient formed surrounding sessile water droplets having varying curvature dictated by the apparent advancing contact angle (100° ≲ θ ≲ 165°). The experiments were carried out at temperatures below and above ambient for a range of fixed droplet radii (130 μm ≲ R ≲ 330 μm). Our results provide a primary validation of the centuries-old theoretical framework underpinning heterogeneous droplet evaporation mediated by the working fluid, substrate, and gas thermophysical properties, droplet apparent contact angle, and droplet size. We show that microscale droplets residing on low-thermal-conductivity substrates such as glass absorb up to 8× more heat from the surrounding gas compared to droplets residing on high-thermal-conductivity substrates such as copper. Finally, our work not only develops an experimental understanding of the heat transfer mechanisms governing droplet evaporation but also presents a powerful platform for the study and characterization of liquid–vapor transport at curved interfaces wetting and nonwetting advanced functional surfaces.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Effects of Phosphonate Structures on Brine–Biotite Interactions under Subsurface Relevant Conditions

Phosphonates have been widely used as scale inhibitors in energy-related subsurface operations, where their performance is greatly affected by interactions with rocks and minerals. However, information about commonly used phosphonate scale inhibitor–shale interactions is limited. In this study, using Fe-bearing mica (biotite) as a model phyllosilicate mineral, the effects of three common phosphonates, namely, iminodi(methylene)phosphonate (IDMP), nitrilotris(methylene)phosphonate (NTMP), and diethylenetriaminepenta(methylene)phosphonate (DTPMP), were studied at 95 °C and 102 atm CO2. During the experiments (0–70 h), IDMP remained stable, while NTMP and DTPMP were degraded and released phosphate, formate, and new phosphonates with smaller molecular weights. As a result of the differences in complexation capability, IDMP, with the fewest phosphonate functional groups, promoted biotite dissolution mainly through surface complexation and DTPMP, with the most functional groups, promoted biotite dissolution mainly through aqueous complexation. Furthermore, the presence of phosphonates enhanced secondary precipitation of P-, Fe-, and Al-bearing minerals, and their phosphonate structures affected the morphologies, phases, and distributions of secondary precipitates. Owing to phosphonate–biotite interactions (mainly as a result of surface adsorption), the biotite surfaces became much more hydrophilic. This study provides new insights into structure-dependent phosphonate–mineral interactions, and the results have important implications for the safety and efficiency of energy-related subsurface operations.

bio-inspired, mechanical behavior, carbon sequestr↗
DOE OSTI2018

Power laws and critical fragmentation in global forests

The replacement of forest areas with human-dominated landscapes usually leads to fragmentation, altering the structure and function of the forest. Here we studied the dynamics of forest patch sizes at a global level, examining signals of a critical transition from an unfragmented to a fragmented state, using the MODIS vegetation continuous field. We defined wide regions of connected forest across continents and big islands, and combined five criteria, including the distribution of patch sizes and the fluctuations of the largest patch over the last sixteen years, to evaluate the closeness of each region to a fragmentation threshold. Regions with the highest deforestation rates–South America, Southeast Asia, Africa–all met these criteria and may thus be near a critical fragmentation threshold. This implies that if current forest loss rates are maintained, wide continental areas could suddenly fragment, triggering extensive species loss and degradation of ecosystems services.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Temporal X-ray Reconstruction using Temporal and Spectral Measurements at LCLS

Transverse deflecting structures (TDSs) are widely used in accelerator physics to measure the longitudinal density of particle bunches. When used in combination with a dispersive section, the whole longitudinal phase space density can be imaged. At the Linac Coherent Light Source (LCLS), the installation of such a device downstream of the undulators enables the reconstruction of the X-ray temporal intensity profile by comparing longitudinal phase space distributions with lasing on and lasing off. However, the resolution of this TDS is limited to around 1 fs rms (root mean square), and therefore, it is not possible to resolve single self-amplified spontaneous emission (SASE) spikes within an X-ray photon pulse. By combining the power spectrum from a high resolution photon spectrometer and the temporal structure from the TDS, the overall resolution is enhanced, thus allowing the observation of temporal, single SASE spikes. The combined data from the spectrometer and the TDS is analysed using an iterative algorithm to obtain the actual intensity profile. In this paper, we present some improvements to the reconstruction algorithm as well as real data taken at LCLS.

47 OTHER INSTRUMENTATION↗
DOE OSTI2025

Elucidating the phase transformations and grain growth behavior of O3-type sodium-ion layered oxide cathode materials during high temperature synthesis

Understanding the formation mechanism of layered oxide cathodes via solid-state synthesis is imperative to achieving controllability over their materials properties and electrochemical behaviors. In this work, we investigate the phase and microstructure evolution during the synthesis of NaNi 1/3 Fe 1/3 Mn 1/3 O 2 , a model sodium-ion layered oxide cathode, using a combination of imaging, diffraction, and spectroscopic techniques. We unravel the synthetic mechanistic pathways involved in the high-temperature calcination reaction, as well as elaborate the synthesis-microstructure-performance relationship of this material. The formation of the final layered oxide phase involves a gradual transformation through a sodiated oxyhydroxide intermediate. During the reaction, the precursor dehydration reaction dominates at 250–550 °C, while the major sodiation reaction occurs at 550–850 °C. Alongside multiple stages of phase transformations, the final grain structure formation occurs through the continuous growth of the (003) and (104) facets. During the reaction, Mn acts as the charge-compensating element and exhibits depth-dependent characteristics. When the sodiation reaction dominates over dehydration, the reaction intermediates undergo gradual electronic structure changes with increasing temperature, as indicated by the spectral features of TM3d-O2p hybrid states. Calcination duration is also a critical parameter governing the microstructure, surface reactivity, phase fraction distribution and electrochemical performance of the material. The optimal calcination duration was determined to be 18 hours at 850 °C under the conditions evaluated here. Calcination beyond this duration was found to be detrimental to electrochemical performance due to Na and O loss and heterogeneous sodium distribution throughout the particles. Our work sheds light on the complex crystallographic-chemical-microstructural evolution of sodium ion layered oxide cathodes and provides insight into precisely tuning material properties which are intimately linked to battery performances.

25 ENERGY STORAGE↗
DOE OSTI2024

Quantum to classical parton evolution in the QGP

We study the time evolution of the density matrix of a high energy quark in the presence of a dense QCD background that is modeled as a stochastic Gaussian color field. At late times, we find that only the color singlet component of the quark’s reduced density matrix survives the in-medium evolution and that the density matrix becomes asymptotically diagonal in both transverse position and momentum spaces. In addition, we observe an accelerated entropy growth due to the larger phase space being explored by the quark and that the quantum and classical quark entropies converge at late times. We further observe that the quark state loses all memory of the initial condition. Combined with the fact that the reduced density matrix satisfies Boltzmann-diffusion transport, we conclude that the quark reduced density matrix can be interpreted as a classical phase space distribution.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2014

Investigation of effect of solenoid magnet on emittances of ion beam from laser ablation plasma

A magnetic field can increase an ion current of a laser ablation plasma and is expected to control the change of the plasma ion current. However, the magnetic field can also make some fluctuations of the plasma and the effect on the beam emittance and the emission surface is not clear. To investigate the effect of a magnetic field, we extracted the ion beams under three conditions where without magnetic field, with magnetic field, and without magnetic field with higher laser energy to measure the beam distribution in phase space. Then we compared the relations between the plasma ion current density into the extraction gap and the Twiss parameters with each condition. We observed the effect of the magnetic field on the emission surface.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

Direct imaging of crystal structure and defects in metastable Ge{sub 2}Sb{sub 2}Te{sub 5} by quantitative aberration-corrected scanning transmission electron microscopy

Knowledge about the atomic structure and vacancy distribution in phase change materials is of foremost importance in order to understand the underlying mechanism of fast reversible phase transformation. In this Letter, by combining state-of-the-art aberration-corrected scanning transmission electron microscopy with image simulations, we are able to map the local atomic structure and composition of a textured metastable Ge{sub 2}Sb{sub 2}Te{sub 5} thin film deposited by pulsed laser deposition with excellent spatial resolution. The atomic-resolution scanning transmission electron microscopy investigations display the heterogeneous defect structure of the Ge{sub 2}Sb{sub 2}Te{sub 5} phase. The obtained results are discussed. Highly oriented Ge{sub 2}Sb{sub 2}Te{sub 5} thin films appear to be a promising approach for further atomic-resolution investigations of the phase change behavior of this material class.

36 MATERIALS SCIENCE↗
DOE OSTI2014

The information-theoretical entropy of some quantum oscillators

The Wehrl entropy or the 'classical' entropy associated with a quantum system is the entropy of the probability distribution in phase space, corresponding to the Husimi Q-function in terms of coherent states. In the present paper, we shall focus our attention on the examination of the Wehrl entropy for both the pure and the mixed (thermal) states of the pseudoharmonic oscillator (PHO). The choice of the PHO is interesting because this oscillator is an intermediate between the ideal one-dimensional harmonic oscillator (HO-1D) and the more practical anharmonicone.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Roles of dynamical symmetry breaking in driving oblate-prolate transitions of atomic clusters

This paper explores the driving mechanisms for structural transitions of atomic clusters between oblate and prolate isomers. We employ the hyperspherical coordinates to investigate structural dynamics of a seven-atom cluster at a coarse-grained level in terms of the dynamics of three gyration radii and three principal axes, which characterize overall mass distributions of the cluster. Dynamics of gyration radii is governed by two kinds of forces. One is the potential force originating from the interactions between atoms. The other is the dynamical forces called the internal centrifugal forces, which originate from twisting and shearing motions of the system. The internal centrifugal force arising from twisting motions has an effect of breaking the symmetry between two gyration radii. As a result, in an oblate isomer, activation of the internal centrifugal force that has the effect of breaking the symmetry between the two largest gyration radii is crucial in triggering structural transitions into prolate isomers. In a prolate isomer, on the other hand, activation of the internal centrifugal force that has the effect of breaking the symmetry between the two smallest gyration radii is crucial in triggering structural transitions into oblate isomers. Activation of a twisting motion that switches the movement patterns of three principal axes is also important for the onset of structural transitions between oblate and prolate isomers. Based on these trigger mechanisms, we finally show that selective activations of specific gyration radii and twisting motions, depending on the isomer of the cluster, can effectively induce structural transitions of the cluster. The results presented here could provide further insights into the control of molecular reactions.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Laser-plasmas in the relativistic-transparency regime: science and applications

Laser-plasma interactions in the novel regime of relativistically induced transparency (RIT) have been harnessed to generate intense ion beams efficiently with average energies exceeding 10 MeV/nucleon (>100 MeV for protons) at “table-top” scales in experiments at the LANL Trident Laser. By further optimization of the laser and target, the RIT regime has been extended into a self-organized plasma mode. This mode yields an ion beam with much narrower energy spread while maintaining high ion energy and conversion efficiency. This mode involves self-generation of persistent high magnetic fields (~10 4 T, according to particle-in-cell simulations of the experiments) at the rear-side of the plasma. These magnetic fields trap the laser-heated multi-MeV electrons, which generate a high localized electrostatic field (~0.1 TV/m). After the laser exits the plasma, this electric field acts on a highly structured ion-beam distribution in phase space to reduce the energy spread, thus separating acceleration and energy-spread reduction. Thus, ion beams with narrow energy peaks at up to 18 MeV/nucleon are generated reproducibly with high efficiency (≈5%). The experimental demonstration has been done with 0.12 PW, high-contrast, 0.6 ps Gaussian 1.053 μm laser pulses irradiating planar foils up to 250 nm thick at 2–8 × 10 20 W/cm 2 . These ion beams with co-propagating electrons have been used on Trident for uniform volumetric isochoric heating to generate and study warm-dense matter at high densities. These beam plasmas have been directed also at a thick Ta disk to generate a directed, intense point-like Bremsstrahlung source of photons peaked at ~2 MeV and used it for point projection radiography of thick high density objects. In addition, prior work on the intense neutron beam driven by an intense deuterium beam generated in the RIT regime has been extended. Neutron spectral control by means of a flexible converter-disk design has been demonstrated, and the neutron beam has been used for point-projection imaging of thick objects. Finally, we discuss the plans and prospects for further improvements and applications.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Impact of bootstrap current and Landau-fluid closure on ELM crashes and transport

Results presented here are from 6-field Landau-Fluid simulations using shifted circular cross-section tokamak equilibria on BOUT++ framework. Linear benchmark results imply that the collisional and collisionless Landau resonance closures make a little difference on linear growth rate spectra which are quite close to the results with the flux limited Spitzer-Härm parallel flux. Both linear and nonlinear simulations show that the plasma current profile plays dual roles on the peeling-ballooning modes that it can drive the low-n peeling modes and stabilize the high-n ballooning modes. For fixed total pressure and current, as the pedestal current decreases due to the bootstrap current which becomes smaller when the density (collisionality) increases, the operational point is shifted downwards vertically in the J ped – α diagram, resulting in threshold changes of different modes. In conclusion, the bootstrap current can slightly increase radial turbulence spreading range and enhance the energy and particle transports by increasing the perturbed amplitude and broadening cross-phase frequency distribution.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

A new method for analyzing and visualizing plasma simulations using a phase-space tessellation

We apply a novel phase-space interpolation technique referred to as the simplex-in-cell (SIC) method to analyze two- and three-dimensional particle-in-cell (PIC) simulations of electromagnetic plasmas. SIC relies on a discretization of the initial phase-space distribution function into simplices, which allows an approximation to the full, continuously defined distribution function to be constructed at any later time in the simulation. This allows densities, currents, and even full momentum distribution functions to be measured at any point in the simulation domain without averaging over control volumes. The SIC approach applies to any PIC simulation for which a tessellation of the initial particle distribution can be constructed. In this study, we use outputs from standard PIC simulations of the Weibel instability and compare physical quantities such as charge and current densities calculated in postprocessing using SIC and standard particle deposits. Using 2D simulations with 1–65 536 particles-per-cell, we find that SIC eliminates discrete particle noise and in some cases can reach a given noise level using ~1000 times fewer simulation particles than with standard particle deposition schemes. In regions of low density, such as between current filaments, SIC is able to capture small amplitude features even with fewer particles than gridpoints due to the deformable nature of the SIC volume elements. Here, by calculating momentum distributions, we show how SIC can capture low density tails in the spectrum using far fewer particles than are necessary for standard particle deposits. We calculate the charge density on spatial grids of increasing resolution to demonstrate the ability of SIC to reveal fine-scale details that are not accessible with standard particle deposits. Finally, we show how SIC can be extended to 3D and give an example of its use to calculate the charge density from 3D PIC simulations of the Weibel instability. These results motivate the future implementation of SIC directly in the simulation force calculation for a novel low-noise electromagnetic plasma simulation method.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Phase modulation failsafe system for multi-kJ lasers based on optical heterodyne detection

Amplification of the transverse scattered component of stimulated Brillouin scattering (SBS) can contribute to optical damage in the large aperture optics of multi-kJ lasers. Because increased laser bandwidth from optical phase modulation (PM) can suppress SBS, high energy laser amplifiers are injected with PM light. Phase modulation distributes the single-frequency spectrum of a master oscillator laser among individual PM sidebands, so a sufficiently high modulation index β can maintain the fluence for all spectral components below the SBS threshold. To avoid injection of single frequency light in the event of a PM failure, a high-speed PM failsafe system (PMFS) must be employed. Because PM is easily converted to AM, essentially all PM failsafes detect AM, with the one described here employing a novel configuration where optical heterodyne detection converts PM to AM, followed by passive AM power detection. Although the PMFS is currently configured for continuous monitoring, it can also detect PM for pulse durations ≥2 ns and could be modified to accommodate shorter pulses. This PMFS was deployed on the Z-Beamlet Laser (ZBL) at Sandia National Laboratories, as required by an energy upgrade to support programs at Sandia’s Z Facility such as magnetized liner inertial fusion. Depending on the origin of a PM failure, the PMFS responds in as little as 7 ns. In the event of an instantaneous failure during initiation of a laser shot, this response time translates to a 30–50 ns margin of safety by blocking a pulse from leaving ZBL’s regenerative amplifier, which prevents injection of single frequency light into the main amplification chain. In conclusion, the performance of the PMFS, without the need for operator interaction, conforms to the principles of engineered safety.

47 OTHER INSTRUMENTATION↗