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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

The effect of realistic conductivities on the high-latitude neutral thermospheric circulation

The dynamics of the high latitude thermosphere are dominated by the ion circulation pattern driven by magnetospheric convection. The reaction of the neutral thermosphere is influenced by both the magnitude of the ion convection velocity and by the conductivity of the thermosphere. Using a three-dimensional, time-dependent, thermospheric, neutral model together with different ionospheric models, the effect of changes in conductivity can be assessed. The ion density is described by two models: the first is the empirical model of Chiu (1975) appropriate for very quiet geomagnetic conditions, and the second is a modified version of the theoretical model of Quegan et al. (1982). The differences in the neutral circulation resulting from the use of these two ionospheric models emphasizes the need for realistic high latitude conductivities when attempting to model average or disturbed geomagnetic conditions, and a requirement that models should couple realistically the ionosphere and the neutral thermosphere. An attempt is made to qualitatively interpret some of the features of the neutral circulation produced at high latitudes by magnetospheric processes.

Fuller-Rowell, T. J.↗
NASA NTRS2006

Laboratory Spectroscopy of Large Carbon Molecules and Ions in Support of Space Missions

One of the major objectives of Laboratory Astrophysics is the optimization of data return from space missions by measuring spectra of atomic and molecular species in laboratory environments that mimic interstellar conditions (WhitePaper (2002, 2006)). Among interstellar species, PAHs are an important and ubiquitous component of carbon-bearing materials that represents a particularly difficult challenge for gas-phase laboratory studies. We present the absorption spectra of jet-cooled neutral and ionized PAHs and discuss the implications for astrophysics. The harsh physical conditions of the interstellar medium have been simulated in the laboratory. We are now, for the first time, in the position to directly compare laboratory spectra of PAHs and carbon nanoparticles with astronomical observations. This new phase offers tremendous opportunities for the data analysis of current and upcoming space missions geared toward the detection of large aromatic systems (HST/COS, FUSE, JWST, Spitzer).

Salana, Farid↗
DOE OSTI2022

A reduced model for the ITER divertor based on SOLPS solutions for ITER Q = 10 baseline conditions: A. identifying options for the control parameters*

Edge codes such as SOLPS coupled to neutral codes such as EIRENE have become so comprehensive and sophisticated that they now constitute, in effect, 'code-experiments' that, as for actual experiments, can benefit from interpretation using simple models and conceptual frameworks, i.e. reduced models. The first task is the identification of options for the reduced model control parameters that are best suited for control of the action of the divertor, i.e. for control of target power loading and sputter-erosion, primarily. A strong correlation between the electron temperature at the divertor target, T e,t , and the neutral deuterium D 2 density at the target, n D2,t , flux-tube resolved, has recently been reported for a number of code studies including SOLPS-4.3 modeling of a set of ~50 ITER baseline cases: Q DT = 10, q 95 = 3, P SOL = 100 MW, metallic walls, and Ne seeding. This part A of the present study reports new results for largely the same ITER cases, confirming the strong correlations reported earlier between local values of T e,t , and (i) n D2,t , and (ii) normalized volumetric losses of power and pressure in the divertor. Strong correlations have now also been found, and are reported here for the first time, between T e,t and all of the divertor target quantities of practical interest. A physical explanation for this surprising result has not been fully identified; nevertheless it has encouraging implications for reduced modeling of the ITER divertor. For such ITER conditions, (i) the global Ne injection rate, Inj Ne [Ne/s], and (ii) the electron temperature at the location on the target where the peak power deposition occurs, T e,t @q ⊥,pk (eV), are found to be promising reduced model control parameters. In the companion report, part B, a reduced model for the ITER divertor is developed and described in detail, based on reversed-direction 2 point modelling, Rev2PM. The input to the reduced model is a value of the variable pair (T et @q ⟂,pk ,Inj Ne ) and the output are values of the various target as well as divertor-entrance quantities of practical interest, e.g. q ⊥,pk , n e,Xpt (the electron density at the poloidal location of the X-point), etc. In part B the reduced model is quantitatively characterized using one half of the code cases; it is then used to successfully predict (replicate) the code values of e.g. n e,Xpt for the other half of the cases.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
NASA NTRS1993

The ISM in the M82 starburst

We have observed (O 1) (63 microns) and (Si 2) (35 microns) in the central 700 pc of the starburst galaxy M82. The luminosities in these transitions are 7.1 x 10(exp 7) solar luminosity and 6.2 x 10(exp 7) solar luminosity, respectively, which are each approx. 0.15% of the bolometric luminosity from this region. The ratios of (O 1) line luminosity to (O 3), (Si 2) (35 microns), and to bolometric luminosities in M82 are similar to those in M42, M17, and Sgr A. These similarities, and the association of the bulk of the (O 1) and (Si 2) emission with the ionized emission, suggest that the dominant emission mechanism for (O 1) and (Si 2) in M82 is the same as in these Galactic regions, namely warm gas photodissociated by UV flux from the OB stars responsible for the nearby H 2 regions. We argue that shock or x ray heated gas or H 2 plasma is a minor contributor to the intensities of these fine structure lines. Both the (O 1) (53 microns) and the (Si 2) (35 microns) spectrum show an asymmetric line profile indistinguishable in shape from those of the (O 3) (52 and 88 microns) and (N 3) (57 microns) lines and similar to that of the more extended (C 2) 158 micron line measured previously in M82. We detect two distinct velocity components, which we attribute to emission from two regions at either end of the central bar, where the bar connects to an orbiting torus of neutral gas seen in H 1 and CO J = 1-0. We model separately the two velocity components and derive the physical conditions in these two regions. The clouds in these regions are small, R approx. 1-2 pc, have warm neutral gas surfaces, T approx. 200 K, and are concentrated with volume filling factors of approx. 0.02 and area filling factors of 1-5. The entire central region (R approx. 700 pc) is characterized by a large number, approx. 5 x 10(exp 4), of 2 x 10(exp 3) solar mass clouds with surface densities of approx. 3 x 10(exp 4) cm(exp -3), illuminated by FUV fluxes 10(exp 4) times the average local interstellar value for the Milky Way. These clouds reside in the harsh conditions of a starburst nucleus, with photoevaporation times of 10(exp 6) yr, and collision timescales only about an order of magnitude longer.

Lord, Steven↗
DOE OSTI2021

Systematic investigations on iron cycling in phosphorus/siderophore systems: Synergism or antagonism?

Synergisms between microbial exudates on Fe (hydr)oxide dissolution as an effective Fe acquisition pathway have been recently addressed and vigorously debated. However, Fe liberation mechanisms and where siderophores and phosphorus (P) coexist received little attentions. Current study systematically investigated ferrihydrite dissolution in the presence of desferrioxamine B (DFOB) (a kind of fungally-derived siderophores) and inorganic/organic phosphorus (orthophosphate, Pi; myo-inositol hexaphosphate, IHP), as a function of solute pH, reaction time and reagent content. Reacted solids were characterized by N 2 -BET adsorption, zeta (ζ) potential analysis, sequential extraction analysis (SEDEX), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), micro Raman spectroscopy and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). Our results indicate that upon reaction with P-only or (DFOB + P) systems, interfacial complexation partially switched from monolayer bidentate-binuclear surface complexes to ternary complexes, or laterally transformed into amorphous Fe–P precipitates. The Fe-Pi complex precipitated more readily under acidic conditions, and Fe-IHP complex preferentially nucleated in neutral-alkaline environments. Phosphorus slightly promoted Fe release from minerals and fixation to the leached layer or interfacial liquid zone initially, but subsequently prevented further attacks from protons and DFOB. The co-effects of P and DFOB likely correspond to two successive scenarios: 1) DFOB is preferentially attracted toward ferrihydrite surfaces by negative electrical fields induced by adsorbed phosphorus and can act synergistically with labile P–Fe complexes, resulting in intensive temporal dissolution of Fh; 2) subsequent Fe shuttling to DFOB can be prohibited by stabilized, passive P/Fe–P layers. Finally, our results emphasize the antagonism between P compounds and siderophores (i.e., DFOB here) on ferrihydrite dissolution to improve understanding of the biologically-mediated Fe cycling in natural systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Three-Dimensional Pore Networks in Miocene Stevens Sandstone of California: Implications for CO 2 Geologic Storage

The Miocene Stevens Sandstone in the San Joaquin Basin of California is increasingly recognized as a promising candidate for CO 2 geological storage due to the enormous storage capacity, proven sealing, and existing infrastructure. In this study, computed microtomography imaging and pore network modeling were employed to investigate the influence of pore geometry and wettability on the CO 2 injectivity and residual trapping. Image analysis revealed that a significant fraction of the cement and matrix consists of microporous regions. The microporosity can substantially increase the overall pore space, yet its contribution to permeability remains modest, particularly in samples with low permeability. The intrinsic heterogeneity of turbidite reservoirs further complicates the reservoir properties among different layers. Two-phase flow simulations under varying wettability conditions (water-wet, weak water-wet, and neutral-wet) demonstrated that the CO 2 injection is predominantly controlled by macropores. CO 2 invades microporous regions only after these larger pores are filled. The presence of microporosity leads to a decrease in both initial and residual CO 2 saturations, with the magnitude of the reduction being influenced by wettability. Neutral-wet scenarios exhibit higher CO 2 mobility and thus lower residual trapping than water-wet scenarios. The results imply that heterogeneity in pore geometry and cement distribution across different layers can result in stratified CO 2 flow pathways, complicating efforts to predict injection performance. Overall, the Stevens Sandstone shows considerable promise for CO 2 geologic storage, but effective implementation will require detailed characterization of the pore structure as well as the integration of reactive fluid flow to account for potential mineral dissolution and fines migration.

fluids↗
DOE OSTI2020

Arsenic Fate in Peat Controlled by the pH-Dependent Role of Reduced Sulfur

Reduced sulfur (S) has a contrasting role in the fate of arsenic (As) in peatlands. Sulfur bridges provide efficient binding of As to organic carbon (C), but the formation of aqueous As–S species, so-called thioarsenates, leads to a low to no sorption tendency to organic C functional groups. Here, we studied how pH changes the role of reduced S in desorption and retention of presorbed As in model peat. Control desorption experiments without S addition revealed that As was mobilized, predominantly as arsenite, in all treatments with relative mobilization increasing with pH (4.5 < 7.0 < 8.5). Addition of sulfide or polysulfide caused substantial As retention at acidic conditions but significantly enhanced As desorption compared to controls at neutral to alkaline pH. Thioarsenates dominated As speciation at pH 7.0 and 8.5 (maximum, 79%) and remained in solution without (re)sorption to peat. Predominance of arsenite in control experiments and no evidence of surface-bound thioarsenates at pH 7.0 suggest mobilization to proceed via arsenite desorption, reaction with dissolved or surface-bound reduced S, and formation of thioarsenates. Our results suggest that natural or management-related increases in pH or increases in reduced S in near-neutral pH environments can turn organic matter from an As sink into a source.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Radicals as Exceptional Electron-Withdrawing Groups: Nucleophilic Aromatic Substitution of Halophenols Via Homolysis-Enabled Electronic Activation

While heteroatom-centered radicals are understood to be highly electrophilic, their ability to serve as transient electron-withdrawing groups and facilitate polar reactions at distal sites has not been extensively developed. Here, we report a new strategy for the electronic activation of halophenols, wherein generation of a phenoxyl radical via formal homolysis of the aryl O-H bond enables direct nucleophilic aromatic substitution of the halide with carboxylate nucleophiles under mild conditions. Pulse radiolysis and transient absorption studies reveal that the neutral oxygen radical (O • ) is indeed an extraor-dinarily strong electron-withdrawing group [σ p - (O • ) = 2.79 vs. σ p - (NO 2 ) = 1.27]. Additional mechanistic and computational studies indicate that the key phenoxyl intermediate serves as an open-shell electron-withdrawing group in these reactions, lowering the barrier for nucleophilic substitution by more than 20 kcal/mol relative to the closed-shell phenol form of the substrate. Finally, by using radicals as transient activating groups, this homolysis-enabled electronic activation strategy provides a powerful platform to expand the scope of nucleophile-electrophile couplings and enable previously challenging transformations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Heterosynaptic plasticity in biomembrane memristors controlled by pH

Abstract In biology, heterosynaptic plasticity maintains homeostasis in synaptic inputs during associative learning and memory, and initiates long-term changes in synaptic strengths that nonspecifically modulate different synapse types. In bioinspired neuromorphic circuits, heterosynaptic plasticity may be used to extend the functionality of two-terminal, biomimetic memristors. In this article, we explore how changes in the pH of droplet interface bilayer aqueous solutions modulate the memristive responses of a lipid bilayer membrane in the pH range 4.97–7.40. Surprisingly, we did not find conclusive evidence for pH-dependent shifts in the voltage thresholds ( V* ) needed for alamethicin ion channel formation in the membrane. However, we did observe a clear modulation in the dynamics of pore formation with pH in time-dependent, pulsed voltage experiments. Moreover, at the same voltage, lowering the pH resulted in higher steady-state currents because of increased numbers of conductive peptide ion channels in the membrane. This was due to increased partitioning of alamethicin monomers into the membrane at pH 4.97, which is below the pKa (~5.3–5.7) of carboxylate groups on the glutamate residues of the peptide, making the monomers more hydrophobic. Neutralization of the negative charges on these residues, under acidic conditions, increased the concentration of peptide monomers in the membrane, shifting the equilibrium concentrations of peptide aggregate assemblies in the membrane to favor greater numbers of larger, increasingly more conductive pores. It also increased the relaxation time constants for pore formation and decay, and enhanced short-term facilitation and depression of the switching characteristics of the device. Modulating these thresholds globally and independently of alamethicin concentration and applied voltage will enable the assembly of neuromorphic computational circuitry with enhanced functionality. Impact statement We describe how to use pH as a modulatory “interneuron” that changes the voltage-dependent memristance of alamethicin ion channels in lipid bilayers by changing the structure and dynamical properties of the bilayer. Having the ability to independently control the threshold levels for pore conduction from voltage or ion channel concentration enables additional levels of programmability in a neuromorphic system. In this article, we note that barriers to conduction from membrane-bound ion channels can be lowered by reducing solution pH, resulting in higher currents, and enhanced short-term learning behavior in the form of paired-pulse facilitation. Tuning threshold values with environmental variables, such as pH, provide additional training and learning algorithms that can be used to elicit complex functionality within spiking neural networks. Graphical abstract

36 MATERIALS SCIENCE↗
DOE OSTI2022

Smart Packaging for Critical Energy Shipment (SPaCES)

Recent technical advances have brought forth revolutionary Smart Packaging (SP) technology. SP incorporates multiple electronics, chemical, and mechanical sensing technologies into packaging materials, and utilizes them to monitor and display package content status. SP can also employ embedded micro actuators to react to undesirable package conditions such as moisture/temperature anomalies or harmful chemical reactions and neutralize it. When further integrated with wireless sensing and secure networking, SP provides wholistic system-wide remote situation awareness capability for real-time crisis management. Finally, we also see that SP can be further integrated with 3D printing technology to offer form-factor customization and application specific solutions suitable for DOE (Department of Energy) NNSA’s (National Nuclear Security Administration) R/N (radiological/nuclear) material shipment and management needs; this has the potential to improve safety, security, and overall operation process quality. This report surveys SP technology as the state of the art (SOTA) and analyzes how it can integrate with cybersecurity and 3D printing to address NNSA’s critical R/N material shipment and storage requirements. This report further presents our FY23/24 investigation plan describing project background, goal, motivation, proposed work, and statement of work and cost.

47 OTHER INSTRUMENTATION↗
DOE OSTI2026

Role of Neutrals Versus Transport in Determining the Pedestal Density Structure: Final Technical Report

In fusion devices the plasma density plays a crucial role in determining the fusion reaction rate and has a direct impact on the fusion gain of a given device. This density is in general regulated by the particle sources and transport near the plasma edge, which give rise to an edge density pedestal. When predicting the performance of future devices, this density pedestal is often prescribed, rather than predicted, due to a lack of models which allow confident extrapolation. This project aims to advance these models through the focused validation of theoretical models related to the transport of fueling neutral particles, and through interpretive transport modeling in present day fusion plasmas, in which the penetration of neutrals is altered to better simulate future reactor-like conditions. Achievements in theory and model validation under this project have advanced our understanding of how much of the edge density profile is set by transport versus direct ionization, enabling interesting projections to future burning plasma devices.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1972

Seasonal effects on distributions of minor neutral constituents in the mesosphere and lower thermosphere.

Calculations have been made of the diurnal variations in minor neutral constituents in the mesosphere and lower thermosphere for the condition of 60 deg latitude, summer and winter. Excited molecular oxygen has been added, and the effects of absorption of Schumann-Runge bands have been taken into account. The results show significant seasonal differences, which may be interpreted mainly in terms of the difference of penetration of solar radiation and the duration of sunlit hours. However, the comparison of the observed seasonal and diurnal variations in the airglow emissions from hydroxyl, atomic oxygen (5577 A), and excited molecular oxygen with those calculated from models suggests that effects of large-scale meridional circulation (horizontal and vertical transports) may be important in explaining these observations. It is shown that the concentration of the constituents whose main loss mechanism is recombination with atomic oxygen decreases sharply above 80 km.

Shimazaki, T.↗
NASA NTRS1972

On the balance of stresses in the plasma sheet.

The stress resulting from magnetic tension on the neutral sheet must, in a steady state, be balanced by any one or a combination of (1) a pressure gradient in the direction along the axis of the tail, (2) a similar gradient of plasma flow kinetic energy, and (3) the tension resulting from a pressure anisotropy within the plasma sheet. Stress balance in the first two cases requires that the ratios h/LX and BZ/BX be of the same order of magnitude, where h is the half-thickness of the neutral sheet, LX is the length scale for variations along the axis of the tail, and BZ and BX are the magnetic field components in the plasma sheet just outside the neutral sheet. The second case requires, in addition, that the plasma flow speed within the neutral sheet be of the order of or larger than the Alfven speed outside the neutral sheet. Stress balance in the third case requires that just outside the neutral sheet the plasma pressure obey the marginal firehose stability condition.

Rich, F. J.↗
NASA NTRS1973

Study of neutral composition of lower thermosphere at Fort Churchill.

On Feb. 4 and 6, 1969, and May 11, 1970, Aerobee rockets carrying neutral mass spectrometers were flown at Fort Churchill, Canada during conditions of low geomagnetic activity. As in earlier flights at White Sands, New Mexico, each rocket carried both 'open' and 'closed' ion source instruments. Vertical profiles of N2, O2, O, Ar, and He were measured. Results obtained were essentially the same as those observed at White Sands except that for the winter flights helium appeared to be in diffusive equilibrium.

Nier, A. O.↗
NASA NTRS1975

Determination of electron temperature in a penning discharge by the helium line ratio method

The helium line ratio technique was used to determine electron temperatures in a toroidal steady-state Penning discharge operating in helium. Due to the low background pressure, less than .0001 torr, and the low electron density, the corona model is expected to provide a good description of the excitation processes in this discharge. In addition, by varying the Penning discharge anode voltage and background pressure, it is possible to vary the electron temperature as measured by the line ratio technique over a wide range (10 to 100+ eV). These discharge characteristics allow a detailed comparison of electron temperatures measured from different possible line ratios over a wide range of temperatures and under reproducible steady-state conditions. Good agreement is found between temperatures determined from different neutral line ratios, but use of the helium ion line results in a temperature systematically 10 eV high compared to that from the neutral lines.

Richardson, R. W.↗
NASA NTRS1978

Quantitative calculations of helium ion escape fluxes from the polar ionospheres

An attempt is made to reduce the discrepancy between the earlier theoretical model and the recent experimental observations of H(+) outward fluxes for winter and summer hemispheres by improving the theoretical model. The helium photoionization cross sections used are accurate to 10%, the latest solar EUV fluxes measured by the Atmosphere Explorer satellites are incorporated, and the most recent MSIS model of the neutral atmosphere is contained in the model. A range of conditions covering solar cycle, seasonal, and geomagnetic conditions are studied. The results show a maximum H(+) escape flux of 1.4 times 10 to the 7th per sq cm per sec for solar maximum, winter, low magnetic activity conditions, which is within the scatter of the measured fluxes. The computed summer H(+) escape flux is a factor of 20 lower than the winter value. Possible reasons for the slight discrepancy between theory and experiment in summer are discussed.

Raitt, W. J.↗
NASA NTRS1980

The latitudinal variation of the charge exchange induced atomic hydrogen escape flux

Using plasma data from the Isis 2 spacecraft and Arecibo radar, diffusive equilibrium models of the ionosphere were constructed for equinox conditions. These plasmaspheric models were combined with models of the neutral atmosphere to calculate the atomic hydrogen escape flux due to charge exchange between thermal protons and to calculate cooler hydrogen and oxygen atoms as a function of dipole latitude and local time. These calculations showed that the daytime escape flux increases as the absolute value of the dipole latitude decreases, reaching its maximum value at the magnetic equator. At 15 hours local time (LT) on March 23, 1972, the calculated escape flux varied from an insignificant amount at 55 deg dipole latitude, to 3 x 10 to the 8th atoms/sq cm sec at the magnetic equators.

Maher, L. J., Jr.↗
NASA NTRS1980

A new determination of the ultraviolet heating efficiency of the thermosphere

Experimental measurements of relevant parameters over the last five years have made possible an accurate reassessment of the thermospheric heating efficiency for solar ultraviolet photons. The outcome of a steady state calculation applicable to mid-latitudes is reported here. The results are found to be significantly different from an earlier determination, both in magnitude and in variation with altitude. The heating efficiency is approximately 50% near the peak of the extreme ultraviolet energy deposition and falls to approximately 10% near 400 km. The implications for the understanding of the thermospheric energy budget are significant. The various energy channels by which solar energy is transferred to the neutral atmosphere are quantified and summer/winter and solar maximum/solar minimum conditions are compared.

Torr, M. R.↗