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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,657 records · Page 92
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

First-principles thermodynamic assessment of Sr-containing secondary phase formation in strontium-substituted lanthanum manganites for solid oxide cell applications

Sr-secondary phase formation is a potentially significant degradation mode with direct impact upon solid-oxide cell (SOC) commercial viability. A first-principles based thermodynamic study was performed for La 1−x Sr x MnO 3±δ (LSM) perovskites to assess their stability against formation of different Sr-secondary phases, including SrO, SrCrO 4 , SrSO 4 , SrCO 3 , and Sr(OH) 2 , for SOC applications. The Sr-secondary phase formation reaction free energies were determined via a thermodynamic model by combining ab initio lattice dynamics calculations for the solid phases and ab initio thermodynamic data for the gas phases. The current approach expands the previously reported thermodynamic modeling studies by integrating first-principles based point defect equilibria into the thermodynamic analysis. The modeling results obtained using this new approach indicate an increased tendency to form the SrO oxide upon decreasing the oxygen partial pressure. Additionally, the enhancing factors to form the Sr-related secondary phase from the associated SrO activity in LSM are further quantified by considering the equilibrium of SrO reacting with the contaminant gas species as a function of temperature and pressure.

defect thermodynamics modeling↗
DOE OSTI2015

SIMULATIONS OF THE SPATIAL AND TEMPORAL INVARIANCE IN THE SPECTRA OF GRADUAL SOLAR ENERGETIC PARTICLE EVENTS

The spatial and temporal invariance in the spectra of energetic particles in gradual solar events is reproduced in simulations. Based on a numerical solution of the focused transport equation, we obtain the intensity time profiles of solar energetic particles (SEPs) accelerated by an interplanetary shock in three-dimensional interplanetary space. The shock is treated as a moving source of energetic particles with a distribution function. The time profiles of particle fluxes with different energies are calculated in the ecliptic at 1 AU. According to our model, we find that shock acceleration strength, parallel diffusion, and adiabatic cooling are the main factors in forming the spatial invariance in SEP spectra, and perpendicular diffusion is a secondary factor. In addition, the temporal invariance in SEP spectra is mainly due to the effects of adiabatic cooling. Furthermore, a spectra invariant region, which agrees with observations but is different from the one suggested by Reames et al. is proposed based on our simulations.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

First-Principles Thermodynamic Assessments of Sr-Containing Secondary Phase Formation in La1-xSrxMnO3±δ Perovskites for Solid Oxide Cell Applications

Sr-secondary phase formation is a potentially significant degradation mode threatening solid-oxide cell (SOC) commercial viability. A first-principles thermodynamic study was performed for rhombohedral perovskite (La1-xSrx) MnO3±δ (LSM) to assess its stability against Sr secondary phase formation in SOC applications. In this work, the Sr secondary phase formation reaction free energies were determined by combining ab initio lattice dynamics calculations for the solid phases and an ab initio thermodynamics approach for the gas phases. Furthermore, this approach goes beyond previous thermodynamic modeling studies by integrating first-principles based point-defect equilibria into the analyses. The modeling results indicate an increased tendency to form SrO oxide from LSM upon decreasing the oxygen partial pressure. Additionally, enhancing factors to form the Sr-related secondary phase from the associated SrO activity in LSM are further quantified by considering the equilibrium of SrO reacting with contaminant gas species as a function of temperature and gas pressure.

Defect and phase stability↗
NASA NTRS2008

Probabilistic Multi-Factor Interaction Model for Complex Material Behavior

The Multi-Factor Interaction Model (MFIM) is used to evaluate the divot weight (foam weight ejected) from the launch external tanks. The multi-factor has sufficient degrees of freedom to evaluate a large number of factors that may contribute to the divot ejection. It also accommodates all interactions by its product form. Each factor has an exponent that satisfies only two points, the initial and final points. The exponent describes a monotonic path from the initial condition to the final. The exponent values are selected so that the described path makes sense in the absence of experimental data. In the present investigation the data used was obtained by testing simulated specimens in launching conditions. Results show that the MFIM is an effective method of describing the divot weight ejected under the conditions investigated.

Chamis, Christos C.↗
NASA NTRS2008

Probabilistic Multi-Factor Interaction Model for Complex Material Behavior

The Multi-Factor Interaction Model (MFIM) is used to evaluate the divot weight (foam weight ejected) from the launch external tanks. The multi-factor has sufficient degrees of freedom to evaluate a large number of factors that may contribute to the divot ejection. It also accommodates all interactions by its product form. Each factor has an exponent that satisfies only two points the initial and final points. The exponent describes a monotonic path from the initial condition to the final. The exponent values are selected so that the described path makes sense in the absence of experimental data. In the present investigation, the data used was obtained by testing simulated specimens in launching conditions. Results show that the MFIM is an effective method of describing the divot weight ejected under the conditions investigated.

Chamis, Christos C.↗
NASA NTRS2009

Probabilistic Multi-Factor Interaction Model for Evaluating Continuous Smooth Curves

The Multi-Factor Interaction Model (MFIM) is used to evaluate the divot weight (foam weight ejected) from launch external tanks. The MFIM has sufficient degrees of freedom to evaluate a large number of factors that may contribute to the divot ejection. It also accommodates all interactions by its product form. Each factor has an exponent that satisfies only two points the initial and final points. They are selected so that the MFIM will generate a common curve to fit the individual point data. The results show that the approach used generates the continuous curve.

Chamis, Christos C.↗
NASA NTRS2010

A Unique Computational Algorithm to Simulate Probabilistic Multi-Factor Interaction Model Complex Material Point Behavior

The Multi-Factor Interaction Model (MFIM) is used to evaluate the divot weight (foam weight ejected) from the launch external tanks. The multi-factor has sufficient degrees of freedom to evaluate a large number of factors that may contribute to the divot ejection. It also accommodates all interactions by its product form. Each factor has an exponent that satisfies only two points--the initial and final points. The exponent describes a monotonic path from the initial condition to the final. The exponent values are selected so that the described path makes sense in the absence of experimental data. In the present investigation, the data used was obtained by testing simulated specimens in launching conditions. Results show that the MFIM is an effective method of describing the divot weight ejected under the conditions investigated.

Chamis, Christos C.↗
NASA NTRS1997

Renal stone risk assessment during Space Shuttle flights

PURPOSE: The metabolic and environmental factors influencing renal stone formation before, during, and after Space Shuttle flights were assessed. We established the contributing roles of dietary factors in relationship to the urinary risk factors associated with renal stone formation. MATERIALS AND METHODS: 24-hr. urine samples were collected prior to, during space flight, and following landing. Urinary and dietary factors associated with renal stone formation were analyzed and the relative urinary supersaturation of calcium oxalate, calcium phosphate (brushite), sodium urate, struvite and uric acid were calculated. RESULTS: Urinary composition changed during flight to favor the crystallization of calcium-forming salts. Factors that contributed to increased potential for stone formation during space flight were significant reductions in urinary pH and increases in urinary calcium. Urinary output and citrate, a potent inhibitor of calcium-containing stones, were slightly reduced during space flight. Dietary intakes were significantly reduced for a number of variables, including fluid, energy, protein, potassium, phosphorus and magnesium. CONCLUSIONS: This is the first in-flight characterization of the renal stone forming potential in astronauts. With the examination of urinary components and nutritional factors, it was possible to determine the factors that contributed to increased risk or protected from risk. In spite of the protective components, the negative contributions to renal stone risk predominated and resulted in a urinary environment that favored the supersaturation of stone-forming salts. Dietary and pharmacologic therapies need to be assessed to minimize the potential for renal stone formation in astronauts during/after space flight.

STS Shuttle Project↗
NASA NTRS1996

Renal-Stone Risk Assessment During Space Shuttle Flights

The metabolic and environmental factors influencing renal stone formation before, during, and after Space Shuttle flights were assessed. We established the contributing roles of dietary factors in relationship to the urinary risk factors associated with renal stone formation. 24-hr urine samples were collected prior to, during space flight, and following landing. Urinary factors associated with renal stone formation were analyzed and the relative urinary supersaturation ratios of calcium oxalate, calcium phosphate (brushite), sodium urate, struvite and uric acid were calculated. Food and fluid consumption was recorded for a 48-hr period ending with the urine collection. Urinary composition changed during flight to favor the crystallization of stone-forming salts. Factors that contributed to increased potential for stone formation during space flight were significant reductions in urinary pH and increases in urinary calcium. Urinary output and citrate, a potent inhibitor of calcium-containing stones, were slightly reduced during space flight. Dietary intakes were significantly reduced for a number of variables, including fluid, energy, protein, potassium, phosphorus and magnesium. This is the first in-flight characterization of the renal stone forming potential in astronauts. With the examination of urinary components and nutritional factors, it was possible to determine the factors that contributed to increased risk or protected from risk. In spite of the protective components, the negative contributions to renal stone risk predominated and resulted in a urinary environment that favored the supersaturation of stone-forming salts. The importance of the hypercalciuria was noted since renal excretion was high relative to the intake.

Whitson, Peggy A.↗
NASA NTRS1989

Assessing applicants to the NASA flight program for their renal stone-forming potential

Because spaceflight can provoke the formation of kidney stones, 24-hour urine samples for 104 male applicants were analyzed for stone-forming risk factors prior to their selection into the NASA astronaut-mission specialist corps. A high level of supersaturation (with either calcium oxalate, brushite, or monosodium urate) was noted in these applicants which predisposes them to the crystallization of stone-forming calcium salts. It is suggested that most of the abnormal stone risk factors found were environmental, rather than metabolic, in origin.

Pak, Charles Y. C.↗
DOE OSTI2023

Lorentz factor for time-of-flight neutron Bragg and total scattering

We report the three fundamental origins of the Lorentz factor for neutron time-of-flight powder diffraction are revisited. A detailed derivation of the Lorentz factor is presented in the context of diffuse scattering modelling in reciprocal space when perfect periodicity is assumed, and the total scattering pattern is constructed in its discrete form – the factor in this case becomes 1/Q 2 (or d 2 ). Discussion is also presented with respect to practical data reduction where a vanadium measurement is usually taken as the normalization factor (to account for various factors such as detector efficiency), and it is shown that the existence of the Lorentz factor is independent of such a normalization process.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Anomaly detection in collider physics via factorized observables

To maximize the discovery potential of high-energy colliders, experimental searches should be sensitive to unforeseen new physics scenarios. This goal has motivated the use of machine learning for unsupervised anomaly detection. In this paper, we introduce a new anomaly detection strategy called : factorized observables for regressing conditional expectations. Our approach is based on the inductive bias of factorization, which is the idea that the physics governing different energy scales can be treated as approximately independent. Assuming factorization holds separately for signal and background processes, the appearance of nontrivial correlations between low- and high-energy observables is a robust indicator of new physics. Under the most restrictive form of factorization, a machine-learned model trained to identify such correlations will in fact converge to the optimal new physics classifier. We test on a benchmark anomaly detection task for the Large Hadron Collider involving collimated sprays of particles called jets. By teasing out correlations between the kinematics and substructure of jets, our method can reliably extract percent-level signal fractions. This strategy for uncovering new physics adds to the growing toolbox of anomaly detection methods for collider physics with a complementary set of assumptions. Published by the American Physical Society 2024

Astronomy & Astrophysics↗
NASA NTRS2000

Is it Possible to have the Similar Unit Cell in Crystals of Different form from the same Macromolecule? (A Case Study of Ribosome Crystals)

Three different types of ribosome crystals were grown by the vapor diffusion technique in hanging drops as described in (1,2). The ribosome is a large asymmetric RNA-protein complex (2.3 million Da), which is protein syntheses machinery of the cell. In this poster we would like to discuss the features of ribosome crystallization. Ribosomes were purified from the thermophilic bacteria Thermus thermophilus by centrifugation (3). Three types of crystals (needle, flat tetragonal and tetragonal-like pyramid) can be grown from the same solution; furthermore, in the same drop using 10-15% 2-methyl-2,4- pentanediol as a precipitant. The crystals appeared in 5-48 hours. The crystals were stable and can co-exist in solution over long period of time. The kinetics of appearance of different crystal forms was different: first the needle crystals were grown, then the tetragonal, and finally the tetragonal pyramids. Later studies of the process of ribosome crystal growth depending on supersaturation showed that low supersaturation results in the appearance of tetragonal plates or tetragonal-like pyramids. An electron microscopy study, together with computer modeling, has shown that crystals of different forms have a high probability of having the same unit cell parameters. According to these experiments the following conclusion can be dranvn: the level of supersaturation of the macromolecule in a crystallizing solution is one of the major factors for forming three-dimensional crystals convenient for X-rays diffraction analysis. From the same macromolecule solution, crystals of different forms can be grown at approximately the same conditions by varying the concentration of macromolecule in the solution. Ion-macromolecule and water-macromolecule interactions, apparently, play the main role in the formation of the unit cell of the crystals.

Karpova, E. A.↗
DOE OSTI2013

Expected Power-Utility Maximization Under Incomplete Information and with Cox-Process Observations

We consider the problem of maximization of expected terminal power utility (risk sensitive criterion). The underlying market model is a regime-switching diffusion model where the regime is determined by an unobservable factor process forming a finite state Markov process. The main novelty is due to the fact that prices are observed and the portfolio is rebalanced only at random times corresponding to a Cox process where the intensity is driven by the unobserved Markovian factor process as well. This leads to a more realistic modeling for many practical situations, like in markets with liquidity restrictions; on the other hand it considerably complicates the problem to the point that traditional methodologies cannot be directly applied. The approach presented here is specific to the power-utility. For log-utilities a different approach is presented in Fujimoto et al. (Preprint, 2012).

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

RFP tags for labeling secretory pathway proteins

Highlights: • Membrane protein Orai1 can be used to report the fusion properties of RFPs. • Artificial puncta are affected by dissociation constant as well as pKa of RFPs. • Among tested RFPs mOrange2 is the best choice for secretory protein labeling. - Abstract: Red fluorescent proteins (RFPs) are useful tools for live cell and multi-color imaging in biological studies. However, when labeling proteins in secretory pathway, many RFPs are prone to form artificial puncta, which may severely impede their further uses. Here we report a fast and easy method to evaluate RFPs fusion properties by attaching RFPs to an environment sensitive membrane protein Orai1. In addition, we revealed that intracellular artificial puncta are actually colocalized with lysosome, thus besides monomeric properties, pKa value of RFPs is also a key factor for forming intracellular artificial puncta. In summary, our current study provides a useful guide for choosing appropriate RFP for labeling secretory membrane proteins. Among RFPs tested, mOrange2 is highly recommended based on excellent monomeric property, appropriate pKa and high brightness.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Engineering a Cysteine-Free Form of Human Fibroblast Growth Factor-1 for “Second Generation” Therapeutic Application

Human fibroblast growth factor-1 (FGF-1) has broad therapeutic potential in regenerative medicine but has undesirable biophysical properties of low thermostability and 3 buried cysteine (Cys) residues (at positions 16, 83, and 117) that interact to promote irreversible protein unfolding under oxidizing conditions. Mutational substitution of such Cys residues eliminates reactive buried thiols but cannot be accomplished simultaneously at all 3 positions without also introducing further substantial instability. The mutational introduction of a novel Cys residue (Ala66Cys) that forms a stabilizing disulfide bond (i.e., cystine) with one of the extant Cys residues (Cys83) effectively eliminates one Cys while increasing overall stability. This increase in stability offsets the associated instability of remaining Cys substitution mutations and permits production of a Cys-free form of FGF-1 (Cys16Ser/Ala66Cys/Cys117Ala) with only minor overall instability. The addition of a further stabilizing mutation (Pro134Ala) creates a Cys-free FGF-1 mutant with essentially wild-type biophysical properties. The elimination of buried free thiols in FGF-1 can substantially increase the protein half-life in cell culture. In this work, we show that the effective cell survival/mitogenic functional activity of a fully Cys-free form is also substantially increased and is equivalent to wild-type FGF-1 formulated in the presence of heparin sulfate as a stabilizing agent. The results identify this Cys-free FGF-1 mutant as an advantageous “second generation” form of FGF-1 for therapeutic application.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2015

Construction of single-crystalline supramolecular networks of perchlorinated hexa-peri-hexabenzocoronene on Au(111)

The self-assembly of the perchlorinated hexa-peri-hexabenzocoronene (PCHBC) molecules on Au(111) has been studied by a low temperature scanning tunneling microscopy (STM) combining with density functional theory based first principle calculations. Highly ordered supramolecular networks with single domains limited by the terraces are formed on Au(111) substrate. High resolution images of the PCHBC molecules, confirmed by first principle simulations, are obtained. It reveals the close-packed arrangement of the PCHBC molecules on Au(111). The calculated charge distribution of PCHBC molecules shows the existence of attractive halogen–halogen interaction between neighboring molecules. Compared with the disordered adsorption of hexa-peri-hexabenzocoronene on Au(111), we conclude that the formation of attractive ClCl interactions between neighbors is the key factor to form the highly ordered, close-packed networks. Due to the steric hindrance resulted from the peripheral chlorine atoms, the PCHBC molecule is contorted and forms the doubly concave conformation, which is different from the hexa-peri-hexabenzocoronene with a planar structure. By using this supramolecular network as a template, we deposited C{sub 60} molecules on it at room temperature with low coverage. The STM images taken at low temperature show that the C{sub 60} molecules are mono-dispersed on the networks and adsorb on top of the PCHBC molecules, forming a typical concave-convex host-guest system.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗