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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 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Multi-isocenter hybrid electron and rapid arc photon treatment for reirradiation of extensive recurrent inflammatory breast cancer

Delivering an adequate and homogenous dose to a large volume of recurrent cutaneous disease can be challenging even with modern techniques. Here, the authors describe a 3-isocenter hybrid electron and rapid arc photon radiation treatment plan to provide optimal tumor coverage to an extensive recurrence of inflammatory breast carcinoma. This approach allowed for homogeneous treatment of a large volume while effectively modulating dose to previously irradiated tissue and minimizing dose to the underlying heart, lungs and brachial plexus.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2017

Extension of the Dytlewski-style dead time correction formalism for neutron multiplicity counting to any order

Here, neutron multiplicity counting using shift-register calculus is an established technique in the science of international nuclear safeguards for the identification, verification, and assay of special nuclear materials. Typically passive counting is used for Pu and mixed Pu-U items and active methods are used for U materials. Three measured counting rates, singles, doubles and triples are measured and, in combination with a simple analytical point-model, are used to calculate characteristics of the measurement item in terms of known detector and nuclear parameters. However, the measurement problem usually involves more than three quantities of interest, but even in cases where the next higher order count rate, quads, is statistically viable, it is not quantitatively applied because corrections for dead time losses are currently not available in the predominant analysis paradigm. In this work we overcome this limitation by extending the commonly used dead time correction method, developed by Dytlewski, to quads. We also give results for pents, which may be of interest for certain special investigations. Extension to still higher orders, may be accomplished by inspection based on the sequence presented. We discuss the foundations of the Dytlewski method, give limiting cases, and highlight the opportunities and implications that these new results expose. In particular there exist a number of ways in which the new results may be combined with other approaches to extract the correlated rates, and this leads to various practical implementations.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

A Chopper Extension to model neutron transport with non-static surfaces and high-speed moving media in MCNPX 2.7

Neutron beamlines frequently include moving components such as neutron choppers. These components are typically wheels that rotate about a fixed axis in order to preferentially transmit or absorb neutrons of the desired energies. Capabilities were developed and implemented into MCNPX to include materials and surfaces in motion. In conclusion, the Chopper Extension implements rotating surfaces and media in MCNPX in order to provide a direct way to include rotating components in models for background calculation purposes.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2024

The gravity extension for MCNP 6.2

Standard MCNP particle tracking takes place along straight-line trajectories from interaction point to interaction point. There is a feature within MCNP that is planned for deprecation that provides surface boundary conditions for approximating gravity for planetary cases, but this feature is not applicable to a cold neutron beam. A new extension has been developed to track particles along parabolic trajectories with a constant acceleration. MCNP contains 1st and 2nd-order surfaces as well as a special case of 4th-order surfaces for simple tori, and the intersection of parabolic trajectories with these surfaces becomes 2nd, 4th, and 8th-order equations in time, respectively. Solving these equations utilizes a fast algorithm for finding the roots of polynomials. Finally, the theory, MCNP input card, and examples of using this new feature will be discussed.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

Updating the MCNP neutron guide extension for supermirror absorption, gamma production, and neutron polarization

As supermirror technology has developed, there is a trend towards higher m-values for supermirrors which propagate more neutrons with higher divergence to experimental areas. These supermirrors have thousands of alternating layers of typically nickel and titanium with varying thicknesses deposited on the surface. Neutrons of grazing incidence are reflected from these layers with a probability dependent on the angle of incidence and the wavelength of the neutron. Those neutrons that are not reflected may be captured in the supermirror layers and produce high energy gamma rays that require shielding. The supermirror extension for MCNP has been updated to estimate the capture of neutrons in the supermirror layers of a neutron guide through the banking of photons in a virtual supermirror layer and the reduction of the weight of the neutrons transmitted into the substrate. A new functionality has been added to simulate neutron polarization specifically in the context of a supermirror polarizer for neutron beamlines. In conclusion, the underlying theory, code implementation in MCNP, and examples of gamma production and a V-cavity polarizer will be discussed.

Gamma production↗
DOE OSTI2020

Stromules, functional extensions of plastids within the plant cell

We report stromules are thin tubular extensions of the plastid compartment surrounded by the envelope membrane. A myriad of functions have been proposed for them, and they likely have multiple roles. Recent work has illuminated aspects of their formation, especially the important of microtubules in their movement and microfilaments in anchoring. A variety of biotic and abiotic stresses result in induction of stromule formation, and in recent years, stromule formation has been strongly implicated as part of the innate immune response. Both stromules and chloroplasts relocate to surround the nucleus when pathogens are sensed, possibly to supply signaling molecules such as reactive oxygen species. In addition to the nucleus, stromules have been observed in close proximity to other compartments such as mitochondria, endoplasmic reticulum, and the plasma membrane, potentially facilitating exchange of substrates and products to carry out important biosynthetic pathways. Much remains to be learned about the identity of proteins and other molecules released from chloroplasts and stromules and how they function in plant development and defense.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Heavy-ion collisions and fission dynamics with the time-dependent Hartree–Fock theory and its extensions

Microscopic methods and tools to describe nuclear dynamics have considerably been improved in the past few years. They are based on the time-dependent Hartree–Fock (TDHF) theory and its extensions to include pairing correlations and quantum fluctuations. The TDHF theory is the lowest level of approximation of a range of methods to solve the quantum many-body problem, showing its universality to describe many-fermion dynamics at the mean-field level. The range of applications of TDHF to describe realistic systems allowing for detailed comparisons with experiment has considerably increased. For instance, TDHF is now commonly used to investigate fusion, multi-nucleon transfer and quasi-fission reactions. Thanks to the inclusion of pairing correlations, it has also recently led to breakthroughs in our description of the saddle to scission evolution, and, in particular, the non-adiabatic effects near scission. Beyond mean-field approaches such as the time-dependent random-phase approximation (TDRPA) and stochastic mean-field methods have reached the point where they can be used for realistic applications. We review recent progresses in both techniques and applications to heavy-ion collision and fission.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

An extensive cocktail approach for rapid risk assessment of in vitro CYP450 direct reversible inhibition by xenobiotic exposure

Acute exposure to environmental factors strongly affects the metabolic activity of cytochrome P450 (P450). As a consequence, the risk of interaction could be increased, modifying the clinical outcomes of a medication. Because toxic agents cannot be administered to humans for ethical reasons, in vitro approaches are therefore essential to evaluate their impact on P450 activities. In this work, an extensive cocktail mixture was developed and validated for in vitro P450 inhibition studies using human liver microsomes (HLM). The cocktail comprised eleven P450-specific probe substrates to simultaneously assess the activities of the following isoforms: 1A2, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1, 2J2 and subfamily 3A. The high selectivity and sensitivity of the developed UHPLC-MS/MS method were critical for the success of this methodology, whose main advantages are: (i) the use of eleven probe substrates with minimized interactions, (ii) a low HLM concentration, (iii) fast incubation (5 min) and (iv) the use of metabolic ratios as microsomal P450 activities markers. This cocktail approach was successfully validated by comparing the obtained IC{sub 50} values for model inhibitors with those generated with the conventional single probe methods. Accordingly, reliable inhibition values could be generated 10-fold faster using a 10-fold smaller amount of HLM compared to individual assays. This approach was applied to assess the P450 inhibition potential of widespread insecticides, namely, chlorpyrifos, fenitrothion, methylparathion and profenofos. In all cases, P450 2B6 was the most affected with IC{sub 50} values in the nanomolar range. For the first time, mixtures of these four insecticides incubated at low concentrations showed a cumulative inhibitory in vitro effect on P450 2B6. - Highlights: • Ten P450 isoforms activities assessed simultaneously with only one incubation. • P450 activity levels measured using the metabolic ratio approach. • IC{sub 50} values generated 10-fold faster and cheaper compared to individual assays. • P450 2B6 was the most affected by pesticides with IC{sub 50} in the nanomolar range. • Cumulative inhibition of P450 2B6 by mixtures of four low-dosed insecticides.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2019

Density Functional Extension to Excited-State Mean-Field Theory

Here, we investigate an extension of excited-state mean-field theory in which the energy expression is augmented with density functional components in an effort to include the effects of weak electron correlations. The approach remains variational and entirely time independent, allowing it to avoid some of the difficulties associated with linear response and the adiabatic approximation. In particular, all of the electrons' orbitals are relaxed state specifically, and there is no reliance on Kohn-Sham orbital energy differences, both of which are important features in the context of charge transfer. Preliminary testing shows clear advantages for single-component charge transfer states, but the method, at least in its current form, is less reliable for states in which multiple particle-hole transitions contribute significantly.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Extension of structure-reactivity correlations for the hydrogen abstraction reaction by bromine atom and comparison to chlorine atom and hydroxyl radical

Recently we presented structure-reactivity correlations for the gas-phase ambient-temperature rate constants for hydrogen abstraction from sp 3 -hybridized carbon by chlorine atom and hydroxyl radical (Cl•/HO• + HCR 3 → HCl/HOH + •CR 3 ); the reaction enthalpy effect was represented by the independent variable Δ r H and the polar effect by the independent variables F and R, the Hammett constants for field/inductive and resonance effects. Both these reactions are predominantly exothermic and have early transition states. Here we present a parallel treatment for Br• whose reaction is significantly endothermic with a correspondingly late transition state. In spite of lower expectations because the available data base is less extensive and much more scattered and because long temperature extrapolations are often required, the resulting least-squares fit (log k 298,Br = –0.147 Δ r H –4.32 ΣF –4.28 ΣR –12.38 with r 2 = 0.92) was modestly successful and useful for initial predictions. The coefficient of Δ r H was ~4-fold greater, indicative of the change from an early to a late transition state; meanwhile the sizable coefficients of ΣF and ΣR indicate the persistence of the polar effect. Although the mean unsigned deviation of 0.79 log k 298 units is rather large, it must be considered in the context of a total span of over 15 log units in the data set. Lastly, the major outliers are briefly discussed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Extension of Hopfield’s Electron Transfer Model To Accommodate Site–Site Correlation

Extension of the Förster analogue for the ET rate constant (based on virtual intermediate electron detachment or attachment states) with inclusion of site–site correlation due to coulomb terms associated with solvent reorganization energy and the driving force, has been developed and illustrated for a simple three-state, two-mode model. Furthermore, the model is applicable to charge separation (CS), recombination (CR), and shift (CSh) ET processes, with or without an intervening bridge. The model provides a unified perspective on the role of virtual intermediate states in accounting for the thermal Franck–Condon weighted density of states (FCWD), the gaps controlling superexchange coupling, and mean absolute redox potentials, with full accommodation of site–site coulomb interactions. We analyzed two types of correlation: aside from the site–site correlation due to coulomb interactions, we have emphasized the intrinsic “nonorthogonality” which generally pertains to reaction coordinates (RCs) for different ET processes involving multiple electronic states, as may be expressed by suitably defined direction cosines (cos(θ)). A pair of RCs may be nonorthogonal even when the site–site coulomb correlations are absent. While different RCs are linearly independent in the mathematical sense for all θ ≠ 0°, they are independent in the sense of being “uncorrelated” only in the limit of orthogonality (θ = 90°). There is application to more than two coordinates is straightforward and may include both discrete and continuum contributions.

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

Extension of the Highly Mobile Membrane Mimetic to Transmembrane Systems through Customized in Silico Solvents

Typically, the mechanics of the protein–lipid interactions of transmembrane proteins are difficult to capture with conventional atomic molecular dynamics, due to the slow lateral diffusion of lipids restricting sampling to states near the initial membrane configuration. The highly mobile membrane mimetic (HMMM) model accelerates lipid dynamics by modeling the acyl tails nearest to the membrane center as a fluid organic solvent while maintaining an atomic description of the lipid headgroups and short acyl tails. The HMMM has been applied to many peripheral protein systems; however, the organic solvent used to date caused deformations in transmembrane proteins by intercalating into the protein and disrupting interactions between individual side chains. We ameliorate the effect of the solvent on transmembrane protein structure through the development of two new in silico Lennard-Jones solvents. The parameters for the new solvents were determined through an extensive parameter search in order to match the bulk properties of alkanes in a highly simplified model. Using these new solvents, we substantially improve the insertion free energy profiles of 10 protein side chain analogues across the entire bilayer. Furthermore, we reduce the intercalation of solvent into transmembrane systems, resulting in native-like transmembrane protein structures from five different topological classes within a HMMM bilayer. The parametrization of the solvents, in addition to their computed physical properties, is discussed. By combining high lipid lateral diffusion with intact transmembrane proteins, we foresee the developed solvents being useful to efficiently identify membrane composition inhomogeneities and lipid binding caused by the presence of membrane proteins.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

MOF Linker Extension Strategy for Enhanced Atmospheric Water Harvesting

A linker extension strategy for generating metal–organic frameworks (MOFs) with superior moisture-capturing properties is presented. Applying this design approach involving experiment and computation results in MOF-LA2-1 {[Al(OH)(PZVDC)], where PZVDC 2– is (E)-5-(2-carboxylatovinyl)-1H-pyrazole-3-carboxylate}, which exhibits an approximately 50% water capacity increase compared to the state-of-the-art water-harvesting material MOF-303. The power of this approach is the increase in pore volume while retaining the ability of the MOF to harvest water in arid environments under long-term uptake and release cycling, as well as affording a reduction in regeneration heat and temperature. Density functional theory calculations and Monte Carlo simulations give detailed insight pertaining to framework structure, water interactions within its pores, and the resulting water sorption isotherm.

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

Hemispheric and large-scale land-surface air temperature variations: An extensive revision and an update to 2010

This study is an extensive revision of the Climatic Research Unit (CRU) land station temperature database that has been used to produce a grid-box data set of 5° latitude × 5° longitude temperature anomalies. The new database (CRUTEM4) comprises 5583 station records of which 4842 have enough data for the 1961–1990 period to calculate or estimate the average temperatures for this period. Many station records have had their data replaced by newly homogenized series that have been produced by a number of studies, particularly from National Meteorological Services (NMSs). Hemispheric temperature averages for land areas developed with the new CRUTEM4 data set differ slightly from their CRUTEM3 equivalent. The inclusion of much additional data from the Arctic (particularly the Russian Arctic) has led to estimates for the Northern Hemisphere (NH) being warmer by about 0.1°C for the years since 2001. The NH/Southern Hemisphere (SH) warms by 1.12°C/0.84°C over the period 1901–2010. The robustness of the hemispheric averages is assessed by producing five different analyses, each including a different subset of 20% of the station time series and by omitting some large countries. CRUTEM4 is also compared with hemispheric averages produced by reanalyses undertaken by the European Centre for Medium-Range Weather Forecasts (ECMWF): ERA-40 (1958–2001) and ERA-Interim (1979–2010) data sets. For the NH, agreement is good back to 1958 and excellent from 1979 at monthly, annual, and decadal time scales. For the SH, agreement is poorer, but if the area is restricted to the SH north of 60°S, the agreement is dramatically improved from the mid-1970s.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

January 2016 extensive summer melt in West Antarctica favoured by strong El Niño

Over the past two decades the primary driver of mass loss from the West Antarctic Ice Sheet (WAIS) has been warm ocean water underneath coastal ice shelves, not a warmer atmosphere. Yet, surface melt occurs sporadically over low-lying areas of the WAIS and is not fully understood. Here we report on an episode of extensive and prolonged surface melting observed in the Ross Sea sector of the WAIS in January 2016. A comprehensive cloud and radiation experiment at the WAIS ice divide, downwind of the melt region, provided detailed insight into the physical processes at play during the event. The unusual extent and duration of the melting are linked to strong and sustained advection of warm marine air toward the area, likely favoured by the concurrent strong El Niño event. Finally, the increase in the number of extreme El Niño events projected for the twenty-first century could expose the WAIS to more frequent major melt events.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Extensive Soot Compaction by Cloud Processing from Laboratory and Field Observations

Soot particles form during combustion of carbonaceous materials and impact climate and air quality. When freshly emitted, they are typically fractal-like aggregates. After atmospheric aging, they can act as cloud condensation nuclei, and water condensation or evaporation restructure them to more compact aggregates, affecting their optical, aerodynamic, and surface properties. Here we survey the morphology of ambient soot particles from various locations and different environmental and aging conditions. We used electron microscopy and show extensive soot compaction after cloud processing. We further performed laboratory experiments to simulate atmospheric cloud processing under controlled conditions. We find that soot particles sampled after evaporating the cloud droplets, are significantly more compact than freshly emitted and interstitial soot, confirming that cloud processing, not just exposure to high humidity, compacts soot. Our findings have implications for how the radiative, surface, and aerodynamic properties, and the fate of soot particles are represented in numerical models.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Interactions between Kuroshio Extension and Central Tropical Pacific lead to preferred decadal-timescale oscillations in Pacific climate

Abstract The Kuroshio Extension (KE) exhibits prominent decadal fluctuations that enhance the low-frequency variability of North Pacific climate. Using available observations, we show evidence that a preferred decadal timescale in the KE emerges from the interaction between KE and the central tropical Pacific via Meridional Modes. Specifically, we show that changes in the KE states apply a persistent downstream atmospheric response (e.g. wind stress curl, 0–12 months timescales) that projects on the atmospheric forcing of the Pacific Meridional Modes (PMM) over 9 months timescales. Subsequently, the PMM energizes the central tropical Pacific El Niño Southern Oscillation (CP-ENSO) and its atmospheric teleconnections back to the Northern Hemisphere (1–3 months timescale), which in turn excites oceanic Rossby waves in the central/eastern North Pacific that propagate westward changing the KE (~3 years timescales). Consistent with this hypothesis, the cross-correlation function between the KE and the PMM/CP-ENSO indices exhibits a significant sinusoidal shape corresponding to a preferred spectral power at decadal timescales (~10 years). This dynamics pathway (KE→PMM/CP-ENSO→KE) may provide a new mechanistic basis to explain the preferred decadal-timescale of the North Pacific and enhance decadal predictability of Pacific climate.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Enhanced interactions of Kuroshio Extension with tropical Pacific in a changing climate

Quasi-decadal climate of the Kuroshio Extension (KE) is pivotal to understanding the North Pacific coupled ocean–atmosphere dynamics and their predictability. Recent observational studies suggest that extratropical-tropical coupling between the KE and the central tropical Pacific El Niño Southern Oscillation (CP-ENSO) leads to the observed preferred decadal time-scale of Pacific climate variability. By combining reanalysis data with numerical simulations from a high-resolution climate model and a linear inverse model (LIM), we confirm that KE and CP-ENSO dynamics are linked through extratropical-tropical teleconnections. Specifically, the atmospheric response to the KE excites Meridional Modes that energize the CP-ENSO (extratropicstropics), and in turn, CP-ENSO teleconnections energize the extratropical atmospheric forcing of the KE (tropicsextratropics). However, both observations and the model show that the KE/CP-ENSO coupling is non-stationary and has intensified in recent decades after the mid-1980. Given the short length of the observational and climate model record, it is difficult to attribute this shift to anthropogenic forcing. However, using a large-ensemble of the LIM we show that the intensification in the KE/CP-ENSO coupling after the mid-1980 is significant and linked to changes in the KE atmospheric downstream response, which exhibit a stronger imprint on the subtropical winds that excite the Pacific Meridional modes and CP-ENSO.

54 ENVIRONMENTAL SCIENCES↗