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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 847 records · Page 47

Acute effects of head-down tilt and hypoxia on modulators of fluid homeostasis

In an effort to understand the interaction between acute postural fluid shifts and hypoxia on hormonal regulation of fluid homeostasis, the authors measured the responses to head-down tilt with and without acute exposure to normobaric hypoxia. Plasma atrial natriuretic peptide (ANP), cyclic guanosine monophosphate (cGMP), cyclic adenosine monophosphate (cAMP), plasma aldosterone (ALD), and plasma renin activity (PRA) were measured in six healthy male volunteers who were exposed to a head-down tilt protocol during normoxia and hypoxia. The tilt protocol consisted of a 17 degrees head-up phase (30 minutes), a 28 degrees head-down phase (1 hour), and a 17 degrees head-up recovery period (2 hours, with the last hour normoxic in both experiments). Altitude equivalent to 14,828 ft was simulated by having the subjects breathe an inspired gas mixture with 13.9% oxygen. The results indicate that the postural fluid redistribution associated with a 60-minute head-down tilt induces the release of ANP and cGMP during both hypoxia and normoxia. Hypoxia increased cGMP, cAMP, ALD, and PRA throughout the protocol and significantly potentiated the increase in cGMP during head-down tilt. Hypoxia had no overall effect on the release of ANP, but appeared to attenuate the increase with head-down tilt. This study describes the acute effects of hypoxia on the endocrine response during fluid redistribution and suggests that the magnitude, but not the direction, of these changes with posture is affected by hypoxia.

Posture↗

Experimental Investigation of Magnesium Powder Combustion With C02 for Mars Ascent Applications

Combustion of metals with CO2 has been identified as a possible propellant for Mars ascent applications. CO2 could be condensed from the Martian atmosphere, reducing the amount of propellant that must be transported from Earth. An attractive feature of this approach compared to other in situ propellant concepts is that no chemical processing on Mars is required. Magnesium has been identified as the most promising metal for this application because it ignites and burns easily in CO2. Preliminary systems studies indicate a 2 to 1 delivered mass advantage for Mg ascent propulsion using in situ C02, as compared to a conventional storable propellant system. The Propulsion Research Center at MSFC is undertaking an experimental investigation of magnesium powder combustion with CO2 in order to provide fundamental data on the combustion performance of Mg powder + CO2 mixtures needed to assess the feasibility of developing a practical Mg powder + CO2 rocket engine. Initial combustion experiments will be carried out in a small scale atmospheric pressure dump combustor. Effects of varying the Mg particle size, firing rate and O/F ratio on combustion stability and efficiency will be investigated. The combustion process will be characterized by optical flame measurements and extraction of combustion product samples. The experimental facility is currently being prepared and combustion experiments will begin during the first quarter of 2005. The final paper will describe the test facility and initial experimental results.

Foote, John P.↗

Hydrogen Isotope Measurements of Organic Acids and Alcohols by Pyrolysis-GC-MS-TC-IRMS: Application to Analysis of Experimentally Derived Hydrothermal Mineral-Catalyzed Organic Products

We report results of experiments to measure the H isotope composition of organic acids and alcohols. These experiments make use of a pyroprobe interfaced with a GC and high temperature extraction furnace to make quantitative H isotope measurements. This work compliments our previous work that focused on the extraction and analysis of C isotopes from the same compounds [1]. Together with our carbon isotope analyses our experiments serve as a "proof of concept" for making C and H isotope measurements on more complex mixtures of organic compounds on mineral surfaces in abiotic hydrocarbon formation processes at elevated temperatures and pressures. Our motivation for undertaking this work stems from observations of methane detected within the Martian atmosphere [2-5], coupled with evidence showing extensive water-rock interaction during Mars history [6-8]. Methane production on Mars could be the result of synthesis by mineral surface-catalyzed reduction of CO2 and/or CO by Fischer-Tropsch Type (FTT) reactions during serpentization [9,10]. Others have conducted experimental studies to show that FTT reactions are plausible mechanisms for low-molecular weight hydrocarbon formation in hydrothermal systems at mid-ocean ridges [11-13]. Our H isotope measurements utilize an analytical technique combining Pyrolysis-Gas Chromatograph-Mass Spectrometry-High Temperature Conversion-Isotope Ratio Mass Spectrometry (Py-GC-MS-TC-IRMS). This technique is designed to carry a split of the pyrolyzed GC-separated product to a Thermo DSQII quadrupole mass spectrometer as a means of making qualitative and semi-quantitative compositional measurements of separated organic compounds, therefore both chemical and isotopic measurements can be carried out simultaneously on the same sample.

Socki, Richard A.↗

Surfactant Studies for Bench Scale Operation

A study has been carried out to examine the effect of a surfactant, sodium lignosulfonate, on the coal liquefaction process to increase coal conversions. A series of coal liquefaction experiments with surfactant addition were conducted in a stirred batch autoclave with 1:2 coal-solvent mixtures with Illinois #6 coal at temperatures from 300 to 400 degrees C and hydrogen pressures from 1500 to 1800 psig. The treated products were analyzed for overall conversion and the distribution of the converted products into lighter and heavy oil fractions, respectively. The batch autoclave results indicate an increase in coal conversions due to surfactant addition at all processing conditions. The analysis also indicates an upgrading of the product slate for temperatures not exceeding 350 degrees C...

Sharma, Pramod K.↗

Mechanism of structural colors in binary mixtures of nanoparticle-based supraballs

Inspired by structural colors in avian species, various synthetic strategies have been developed to produce noniridescent, saturated colors using nanoparticle assemblies. Nanoparticle mixtures varying in particle chemistry and size have additional emergent properties that affect the color produced. For complex multicomponent systems, understanding the assembled structure and a robust optical modeling tool can empower scientists to identify structure-color relationships and fabricate designer materials with tailored color. Here, we demonstrate how we can reconstruct the assembled structure from small-angle scattering measurements using the computational reverse-engineering analysis for scattering experiments method and use the reconstructed structure in finite-difference time-domain calculations to predict color. We successfully, quantitatively predict experimentally observed color in mixtures containing strongly absorbing nanoparticles and demonstrate the influence of a single layer of segregated nanoparticles on color produced. The versatile computational approach that we present is useful for engineering synthetic materials with desired colors without laborious trial-and-error experiments.

36 MATERIALS SCIENCE↗

Synergistically Chemical and Thermal Coupling between Graphene Oxide and Graphene Fluoride for Enhancing Aluminum Combustion

Metal combustion reaction is highly exothermic and is used in energetic applications, such as propulsion, pyrotechnics, powering micro- and nano-devices, and nanomaterials synthesis. Aluminum (Al) is attracting great interest in those applications because of its high energy density, earth abundance, and low toxicity. Nevertheless, Al combustion is hard to initiate and progresses slowly and incompletely. On the other hand, ultrathin carbon nanomaterials, such as graphene, graphene oxide (GO), and graphene fluoride (GF), can also undergo exothermic reactions. Herein, we demonstrate that the mixture of GO and GF significantly improves the performance of Al combustion as interactions between GO and GF provide heat and radicals to accelerate Al oxidation. Overall, our experiments and reactive molecular dynamics simulation reveal that GO and GF have strong chemical and thermal couplings through radical reactions and heat released from their oxidation reactions. GO facilitates the dissociation of GF, and GF accelerates the disproportionation and oxidation of GO. When the mixture of GO and GF is added to micron-sized Al particles, their synergistic couplings generate reactive oxidative species, such as CF x and CF x O y , and heat, which greatly accelerates Al combustion. This work demonstrates a new area of using synergistic couplings between ultrathin carbon nanomaterials to accelerate metal combustion and potentially oxidation reactions of other materials.

36 MATERIALS SCIENCE↗

Experimental Studies of Brines and Evaporites as Applied to Mars: Initial Results from 1998-1999 Runs

We are performing laboratory experiments to determine the concentrations and rates of dissolution of ions that could occur in closed, juvenile groundwater systems on Mars. Our approach is to incubate unaltered Mars-analog minerals in initially pure liquid water in contact with a Mars gas mixture for one year. At exponentially increasing time intervals, aliquots of the solutions at three different temperatures are extracted and analyzed using standard terrestrial laboratory geochemical techniques. Ultimately, our experiments will produce Mars analog brines which will be freeze dried to create evaporites. The physical and chemical properties of these evaporites will be compared with spacecraft remote sensing and in situ compositional and physical data. Additional information is contained in the original extended abstract.

Moore, J. M.↗

Internal structure of shock waves in disparate mass mixtures

The detailed flow structure of a normal shock wave for a gas mixture is investigated using the direct-simulation Monte Carlo method. A variable diameter hard-sphere (VDHS) model is employed to investigate the effect of different viscosity temperature exponents (VTE) for each species in a gas mixture. Special attention is paid to the irregular behavior in the density profiles which was previously observed in a helium-xenon experiment. It is shown that the VTE can have substantial effects in the prediction of the structure of shock waves. The variable hard-sphere model of Bird shows good agreement, but with some limitations, with the experimental data if a common VTE is chosen properly for each case. The VDHS model shows better agreement with the experimental data without adjusting the VTE. The irregular behavior of the light-gas component in shock waves of disparate mass mixtures is observed not only in the density profile, but also in the parallel temperature profile. The strength of the shock wave, the type of molecular interactions, and the mole fraction of heavy species have substantial effects on the existence and structure of the irregularities.

Chung, Chan-Hong↗

Development of Thin Gap GEM-µRWELL Hybrid Detectors at Jefferson Lab

Over the past few decades, Micro Pattern Gaseous Detector (MPGD) technologies have been increasingly adopted as tracking detector options in High Energy and Nuclear Physics experiments thanks to their good spatial resolution, high-rate capability, stability and more importantly their ability for large area coverage at a relatively low cost compared to the alternative. The thin gap GEM-µRWELL hybrid detector is the latest addition to the MPGD family, that was introduced to vastly improve the spatial resolution capability of gaseous trackers when deployed in the barrel region to cover large angular acceptance of the central tracker in a collider experiment. In this talk, I will re-introduce the concept and motivation for the development of thin gap GEM-µRWELL hybrid technology with an emphasis on the initial studies that establish the proof-of-concept of the technology. I will then discuss the more recent results from latest beam test campaign at Jefferson Lab in May 2025 to study detector efficiency performance with various gas mixtures. I will also briefly present the ongoing activities to develop large area thin gap GEM-µRWELL tracking detectors for the ePIC experiment of the future Electron Ion Collider as well as the exploration of the technology to provide large area tracking options to the muon system of experiments at a future Higgs Factory Collider such as the FCC-ee for example. Finally, I will conclude with some perspectives on new ideas under exploration to develop the next generation of thin gap MPGD technologies with enhanced timing and spatial resolution capabilities

Gnanvo, Kondo [Thomas Jefferson National Accelerat↗

Spacelab J: Microgravity and life sciences

Spacelab J is a joint venture between NASA and the National Space Development Agency of Japan (NASDA). Using a Spacelab pressurized long module, 43 experiments will be performed in the areas of microgravity and life sciences. These experiments benefit from the microgravity environment available on an orbiting Shuttle. Removed from the effects of gravity, scientists will seek to observe processes and phenomena impossible to study on Earth, to develop new and more uniform mixtures, to study the effects of microgravity and the space environment on living organisms, and to explore the suitability of microgravity for certain types of research. Mission planning and an overview of the experiments to be performed are presented. Orbital research appears to hold many advantages for microgravity science investigations, which on this mission include electronic materials, metals and alloys, glasses and ceramics, fluid dynamics and transport phenomena, and biotechnology. Gravity-induced effects are eliminated in microgravity. This allows the investigations on Spacelab J to help scientists develop a better understanding of how these gravity-induced phenomena affect both processing and products on Earth and to observe subtle phenomena that are masked in gravity. The data and samples from these investigations will not only allow scientists to better understand the materials but also will lead to improvements in the methods used in future experiments. Life sciences research will collect data on human adaptation to the microgravity environment, investigate ways of assisting astronauts to readapt to normal gravity, explore the effects of microgravity and radiation on living organisms, and gather data on the fertilization and development of organisms in the absence of gravity. This research will improve crew comfort and safety on future missions while helping scientists to further understand the human body.

Source record↗

Simulations of Attosecond Metallization in Quartz and Diamond Probed with Inner-Shell Transient Absorption Spectroscopy

When dielectrics are hit with intense infrared (IR) laser pulses, transient metalization can occur. The initial attosecond dynamics behind this metallization are not entirely understood. Therefore, simulations are needed to understand this process and to help interpret experimental observations of it, such as with attosecond transient absorption (ATA). In this paper, we present first-principles simulations of ATA based on bulk-mimicking clusters and real-time time-dependent density functional theory (RT-TDDFT), with Koopmans-tuned range-separated hybrid functionals and Gaussian basis sets. Our method gives good agreement with the experiment for the breakdown threshold in silica and diamond. This breakdown voltage corresponds to a Keldysh parameter of approximately one and thus involves a transition to a regime where the dynamics are driven by tunneling. Pumping at an amplitude just below this value causes a mixture of multiphoton and tunneling excitations across the band gap to occur. The computed extreme ultraviolet and X-ray attosecond transient spectra also agree well with the experiment and show a decrease in optical density due to the transient population of the conduction band from the IR field. First-principles approaches such as this are valuable for interpreting the complicated modulations in a spectrum and for guiding future attosecond experiments on solids.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Smectite clays in Mars soil - Evidence for their presence and role in Viking biology experimental results

Evidence for the presence of smectite clays in Martian soils is reviewed and results of experiments with certain active clays simulating the Viking biology experiments are reported. Analyses of Martian soil composition by means of X-ray fluorescence spectrometry and dust storm spectroscopy and Martian geological history strongly suggest the presence of a mixture of weathered ferro-silicate minerals, mainly nontronite and montmorillonite, accompanied by soluble sulphate salts, as major constituents. Samples of montmorillonite and nontronite incubated with (C-14)-formate or the radioactive nutrient medium solution used in the Viking Labeled Release experiment, were found to produce patterns of release of radioactive gas very similar to those observed in the Viking experiments, indicating the iron-catalyzed decomposition of formate as the reaction responsible for the Viking results. The experimental results of Hubbard (1979) simulating the results of the Viking Pyrolytic Release experiment using iron montmorillonites are pointed out, and it is concluded that many of the results of the Viking biology experiments can be explained in terms of the surface activity of smectite clays in catalysis and adsorption.

Banin, A.↗

Mixture-process variable approach to optimize a microemulsion electrokinetic chromatography method for the quality control of a nutraceutical based on coenzyme Q10

In recent years, multivariate optimization has played an increasing role in analytical method development. ICH guidelines recommend using statistical design of experiments to identify the design space, in which multivariate combinations of composition variables and process variables have been demonstrated to provide quality results. Considering a microemulsion electrokinetic chromatography method (MEEKC), the performance of the electrophoretic run depends on the proportions of mixture components (MCs) of the microemulsion and on the values of process variables (PVs). In the present work, for the first time in the literature, a mixture-process variable (MPV) approach was applied to optimize a MEEKC method for the analysis of coenzyme Q10 (Q10), ascorbic acid (AA), and folic acid (FA) contained in nutraceuticals. The MCs (buffer, surfactant-cosurfactant, oil) and the PVs (voltage, buffer concentration, buffer pH) were simultaneously changed according to a MPV experimental design. A 62-run MPV design was generated using the I-optimality criterion, assuming a 46-term MPV model allowing for special-cubic blending of the MCs, quadratic effects of the PVs, and some MC-PV interactions. The obtained data were used to develop MPV models that express the performance of an electrophoretic run (measured as peak efficiencies of Q10, AA, and FA) in terms of the MCs and PVs. Contour and perturbation plots were drawn for each of the responses. Finally, the MPV models and criteria for the peak efficiencies were used to develop the design space and an optimal subregion (i.e., the settings of the mixture MCs and PVs that satisfy the respective criteria), as well as a unique optimal combination of MCs and PVs.

Coenzyme Q10↗

A Multicomponent Blend as a Diesel Fuel Surrogate for Compression Ignition Engine Applications

A mixture of n-dodecane and m-xylene is investigated as a diesel fuel surrogate for compression ignition engine applications. Compared to neat n-dodecane, this binary mixture is more representative of diesel fuel because it contains an alkyl-benzene which represents an important chemical class present in diesel fuels. A detailed multi-component mechanism for n-dodecane and m-xylene was developed by combining a previously developed n-dodecane mechanism with a recently developed mechanism for xylenes. The xylene mechanism is shown to reproduce experimental ignition data from a rapid compression machine and shock tube, speciation data from the jet stirred reactor and flame speed data. This combined mechanism was validated by comparing predictions from the model with experimental data for ignition in shock tubes and for reactivity in a flow reactor. The combined mechanism, consisting of 2885 species and 11754 reactions, was reduced to a skeletal mechanism consisting 163 species and 887 reactions for 3D diesel engine simulations. The mechanism reduction was performed using directed relation graph (DRG) with expert knowledge (DRG-X) and DRG-aided sensitivity analysis (DRGASA) at a fixed fuel composition of 77% of n-dodecane and 23% m-xylene by volume. The sample space for the reduction covered pressure of 1 – 80 bar, equivalence ratio of 0.5 – 2.0, and initial temperature of 700 – 1600 K for ignition. The skeletal mechanism was compared with the detailed mechanism for ignition and flow reactor predictions. Finally, the skeletal mechanism was validated against a spray flame dataset under diesel engine conditions documented on the Engine Combustion Network (ECN) website. These multidimensional simulations were performed using a Representative Interactive Flame (RIF) turbulent combustion model. In conclusion, encouraging results were obtained compared to the experiments with regards to the predictions of ignition delay and lift-off length at different ambient temperatures.

30 DIRECT ENERGY CONVERSION↗

Convection and chemistry effects in CVD: A 3-D analysis for silicon deposition

The computational fluid dynamics code FLUENT has been adopted to simulate the entire rectangular-channel-like (3-D) geometry of an experimental CVD reactor designed for Si deposition. The code incorporated the effects of both homogeneous (gas phase) and heterogeneous (surface) chemistry with finite reaction rates of important species existing in silane dissociation. The experiments were designed to elucidate the effects of gravitationally-induced buoyancy-driven convection flows on the quality of the grown Si films. This goal is accomplished by contrasting the results obtained from a carrier gas mixture of H2/Ar with the ones obtained from the same molar mixture ratio of H2/He, without any accompanying change in the chemistry. Computationally, these cases are simulated in the terrestrial gravitational field and in the absence of gravity. The numerical results compare favorably with experiments. Powerful computational tools provide invaluable insights into the complex physicochemical phenomena taking place in CVD reactors. Such information is essential for the improved design and optimization of future CVD reactors.

Gokoglu, S. A.↗

Probing the Active Sites of MoS 2 Based Hydrotreating Catalysts Using Modulation Excitation Spectroscopy

The reactive surface sites of MoS 2 hydrotreating catalysts (unpromoted as well as Co- and Ni-promoted) supported on MgAl 2 O 4 spinel were investigated with respect to the substitution of sulfur by oxygen using in situ XAS coupled with modulation excitation spectroscopy (MES). Specifically, MES experiments were carried out by periodically cycling between a H 2 O and H 2 S containing hydrogen gas mixture at 400 °C. Due to the low fraction of S–O exchange, conventional XANES and EXAFS data hardly showed any changes when these catalysts were exposed to increasing ratios of H 2 O to H 2 S in an H 2 atmosphere. XANES and EXAFS data extracted at the Mo K-edge by MES analysis showed that for approximately 1% of the Mo atoms, sulfur atoms are replaced by oxygen atoms when exposed to H 2 O, causing partial oxidation of these active sites. The reaction is reversible and Mo returns to its initial sulfide phase when H 2 O is removed and H 2 S is supplied in the feed. In the case of Co- and Ni-promoted catalysts, the magnitude of S–O exchange was found to be reduced, indicating the beneficial effect of promotion. MES at the Ni K-edge showed that Ni was oxidized during H 2 O exposure, which in turn delayed the Mo oxidation in the Ni-promoted catalyst. The structures of these catalysts under S–O exchange were modeled using density functional theory (DFT) calculations, showing that the edge atoms are affected strongly. For all three catalysts, OH substitution is more favorable, while O substitution could be possible at high H 2 O pressure for unpromoted MoS 2 . Mo K-edge XANES spectra calculated using these simulated structures support the results obtained from the MES experiments. In conclusion, the presented approach using MES in combination with XAS and supported by DFT can be extended in general to catalysts under operando conditions and is thus a useful tool for determination of the active site on an atomic-scale.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

High Intensity Femtosecond XUV Pulse Interactions with Atomic Clusters: Final Report

We propose to expand our recent studies on the interactions of intense extreme ultraviolet (XUV) femtosecond pulses with atomic and molecular clusters. The work described follows directly from work performed under BES support for the past grant period. During this period we upgraded the THOR laser at UT Austin by replacing the regenerative amplifier with optical parametric amplification (OPA) using BBO crystals. This increased the contrast of the laser, the total laser energy to ~1.2 J , and decreased the pulse width to below 30 fs. We built a new all reflective XUV harmonic beam line into expanded lab space. This enabled an increase influence by a factor of 25 and an increase in the intensity by a factor of 50. The goal of the program proposed in this renewal is to extend this class of experiments to available higher XUV intensity and a greater range of wavelengths. In particular we plan to perform experiments to confirm our hypothesis about the origin of the high charge states in these exploding clusters, an effect which we ascribe to plasma continuum lowering (ionization potential depression) in a cluster nano-­plasma. To do this we will perform experiments in which XUV pulses of carefully chosen wavelength irradiate clusters composed of only low-Z atoms and clusters with a mixture of this low-­Z atom with higher Z atoms. The latter clusters will exhibit higher electron densities and will serve to lower the ionization potential further than in the clusters composed only of low Z atoms. This should have a significant effect on the charge states produced in the exploding cluster. We will also explore the transition of explosions in these XUV irradiated clusters from hydrodynamic expansion to Coulomb explosion. The work proposed here will explore clusters of a wider range of constituents, including clusters from solids. Experiments on clusters from solids will be enabled by development we performed during the past grant period in which we constructed and tested a cluster generator based on the Laser Ablation of Microparticles (LAM) method.

74 ATOMIC AND MOLECULAR PHYSICS↗

Yield degradation in inertial-confinement-fusion implosions due to shock-driven kinetic fuel-species stratification and viscous heating

Anomalous thermonuclear yield degradation (i.e., that not describable by single-fluid radiation hydrodynamics) in Inertial Confinement Fusion (ICF) implosions is ubiquitously observed in both Omega and National Ignition experiments. Multiple experimental and theoretical studies have been carried out to investigate the origin of such a degradation. Relative concentration changes of fuel-ion species, as well as kinetically enhanced viscous heating, have been among possible explanations proposed for certain classes of ICF experiments. In this study, we investigate the role of such kinetic plasma effects in detail. To this end, we use the iFP code to perform multi-species ion Vlasov-Fokker-Planck simulations of ICF capsule implosions with the fuel comprising various hydrodynamically equivalent mixtures of deuterium (D) and helium-3 (3He), as in the original. We employ the same computational setup as in O. Larroche, which was the first to simulate the experiments kinetically. However, unlike the Larroche study, and in partial agreement with experimental data, we find a systematic yield degradation in multi-species simulations versus averaged-ion simulations when the D-fuel fraction is decreased. This yield degradation originates in the fuel-ion species stratification induced by plasma shocks, which imprints the imploding system and results in the relocation of the D ions from the core of the capsule to its periphery, thereby reducing the yield relative to a non-separable averaged-ion case. By comparing yields from the averaged-ion kinetic simulations and from the hydrodynamic scaling, we also observe yield variations associated with ion kinetic effects other than fuel-ion stratification, such as ion viscous heating, which is typically neglected in hydrodynamic implosions' simulations. Since our kinetic simulations are driven by hydrodynamic boundary conditions at the fuel-ablator interface, they cannot capture the effects of ion viscosity on the capsule compression, or effects associated with the interface, which are expected to be important. As a result, studies of such effects are left for future work.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗