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All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Transfer Function Models and Sensitivity Analysis

In many situations, real or induced flaws such as tight cracks with known morphology cannot be manufactured in part configuration specimens or in real parts. Typically, fatigue cracks are manufactured in simple geometry specimens such as flat plates, dog-bone shaped flat or round specimens. If a nondestructive evaluation (NDE) technique is required to provide a reliably detectable target flaw size denoted as α_(90/95) for induced flaws in real part, then the direct method for qualifying the NDE procedure is to use the appropriate induced flaw specimens and perform probability of detection analysis using these flaws. This can be described as direct POD demonstration testing, which may follow guidelines of MIL-HDBK-1823. This paper considers a case, where induced flaws are not available in part configuration specimens. Therefore, a direct POD demonstration study cannot be undertaken. In such situation, general practice for NDE procedure qualification is to use artificial flaws in simple geometry and part configuration specimens, and induced flaws in the chosen simple geometry specimens. Signal response data is taken on all sets of artificial and induced flaws. NDE procedure testing on induced flaw in simple geometry specimen is called NDE demonstration testing here. A transfer function NDE procedure qualification method for forward case calculates predicted induced flaw size for demonstration using a chosen target flaw size. Another transfer function method for inverse case, calculates the target flaw size using a given demonstration flaw size. The transfer function analysis assumes relationship of artificial flaw signal responses in real parts and simple geometry specimens; and induced flaw responses in simple geometry specimens to induced flaws in real parts. The signal response transfer relationships model should be defined before transfer function models can be devised. Assuming that the signal response transfer relationships model is valid, forward and inverse case transfer function methods have been devised. Because of lack of signal response data from induced flaws in real part, 90/95% POD/confidence (P/C) cannot be demonstrated directly. However, the transfer function method may be assessed using simulation to evaluate whether the resulting target flaw size or demonstration flaw size provides adequate confidence to the assumed signal response transfer relationships model. Therefore, the transfer function approach is a risk assessment approach. Both the signal response transfer relationships model and the transfer function model are important in managing risk in results provided by the transfer function NDE technique qualification or assessment. The signal response transfer relationships model needs to be validated with empirical data and then transfer function model needs to be validated for desired P/C on case-by-case basis.

Nondestructive evaluation↗
NASA NTRS2022

Run Time Assurance for Electric Vertical Takeoff and Landing Aircraft

NASA is conducting research to demonstrate and evaluate the application of Run Time Assurance (RTA) as a means to assure safety in Electric Vertical Takeoff and Landing (eVTOL) aircraft with highly automated or autonomous flight capability supervised by a single onboard pilot. The work described in this report demonstrates an application of RTA and examines the implications for design and analysis of aircraft functions and systems; aircraft safety hazards; safety assurance; development assurance; and pilot tasks and performance. This research effort also seeks to assess the efficacy of the combined application of traditional Functional Hazard Analysis (FHA) and the more modern System Theoretic Process Analysis (STPA) techniques to perform hazard analyses on aircraft with complex automated and autonomous systems and an onboard pilot. During the research effort we developed architectural designs of two alternate eVTOL aircraft, generally following the process characterized in the SAE standards ARP4754 and ARP4761. The design has focused on the control architectures of these aircraft, which are identical except that one incorporates RTA techniques to reduce the criticality of some key software components. Artifacts of this process include a taxonomy of aircraft-level functions, aircraft-level architecture diagrams, aircraft-level functional hazard assessments (AFHA), function allocations onto aircraft systems and subsystems, functional block diagrams for a select set of control-related functions, and system-level functional hazard assessments (SFHA) for those functions. This project has highlighted the notion that DAL D is something of a sweet spot for low-confidence controllers in an RTA-based design. Among the many activities described in DO-178C, the activities related to requirement verifiability, algorithmic accuracy, and test coverage can be the most challenging for the kinds of advanced control techniques that may be desirable in novel UAM designs, such as adaptive control, machine-learning, artificial intelligence, numerical search, and Monte Carlo based algorithms. Moreover, the standard requires that development teams demonstrate that errors leading to unacceptable failure conditions have been removed from the software. The RTA architecture, which cordons off the low-confidence function, makes it much easier to show this for these kinds of algorithms. With regard to the use of STPA and FHA as complementary hazard analysis techniques, our research effort led us to the conclusion that STPA should be used to derive requirements for hardware and software systems and/or components. Also, STPA is a natural complement to other processes in ARP4754A involving design studies and iteration.

Run-time assurance↗
DOE OSTI2011

Configuration mixing of angular-momentum-projected triaxial relativistic mean-field wave functions. II. Microscopic analysis of low-lying states in magnesium isotopes

The recently developed structure model that uses the generator coordinate method to perform configuration mixing of angular-momentum projected wave functions, generated by constrained self-consistent relativistic mean-field calculations for triaxial shapes (3DAMP+GCM), is applied in a systematic study of ground states and low-energy collective states in the even-even magnesium isotopes {sup 20-40}Mg. Results obtained using a relativistic point-coupling nucleon-nucleon effective interaction in the particle-hole channel and a density-independent {delta} interaction in the pairing channel are compared to data and with previous axial 1DAMP+GCM calculations, both with a relativistic density functional and the nonrelativistic Gogny force. The effects of the inclusion of triaxial degrees of freedom on the low-energy spectra and E2 transitions of magnesium isotopes are examined.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRSDate not supplied

NESC GN&C TDT Workshop on 2D Image Motion Optical Transfer Functions, Pointing Performance Analysis, and Requirements

This course was prepared by the author in support of the NASA GN&C Technical Discipline Team (TDT). The purpose of this two-day course is to inform practicing GN&C engineers, and other system and subsystem engineers, including payload engineers and mission analysts, of methodologies to analyze the pointing performance of spacecraft and to write unambiguous pointing requirements that are relevant to optical payload performance. It is hoped that the seminar will contribute to a best-practices manual and contribute to accepted and uniform means of requirements definition, validation, and verification. The course material is designed to address the needs of not only practicing GN&C engineers, but also system and subsystem engineers of other disciplines, payload engineers, mission analysts, and even astronomers who need to understand how they interface to a GN&C subsystem. Much revision is the direct result of active student participation during the presentations and from feedback obtained through course evaluation forms.

2D Image↗
NASA NTRS1984

Penalty function finite element analysis of steady viscous incompressible flow in rotating coordinates

Finite element methods for incompressible viscous flow in turbomachines have not been presented in the literature previously. This paper develops a penalty function primitive variable method including Coriolis and centrifugal force terms for steady flow in a rotating coordinate system. Simplex elements are used with the result of solution times comparable to equivalent finite different solutions. Example cases considered are Couette flow, Poiseuile flow, flow over a step and flow in a rotating channel. Both laminar and turbulent flows are discussed. The accuracy of computed solutions compares well with theoretical solutions and experimenal measurements.

Rosen, M. C.↗
DOE OSTI2023

Synthetic Access to a Framework-Stabilized and Fully Sulfided Analogue of an Anderson Polyoxometalate that is Catalytically Competent for Reduction Reactions

Polyoxometalates (POMs) featuring 7, 12, 18, or more redox-accessible transition metal ions are ubiquitous as selective catalysts, especially for oxidation reactions. The corresponding synthetic and catalytic chemistry of stable, discrete, capping-ligand-free polythiometalates (PTMs), which could be especially attractive for reduction reactions, is much less well developed. Among the challenges are the propensity of PTMs to agglomerate and the tendency for agglomeration to block reactant access of catalyst active sites. Nevertheless, the pervasive presence of transition metal sulfur clusters metalloenzymes or cofactors that catalyze reduction reactions and the justifiable proliferation of studies of two-dimensional (2D) metal-chalcogenides as reduction catalysts point to the promise of well-defined and controllable PTMs as reduction catalysts. Here, we report the fabrication of agglomeration-immune, reactant-accessible, capping-ligand-free Co II Mo 6 IV S 24 n– clusters as periodic arrays in a water-stable, hierarchically porous Zr-metal–organic framework (MOF; NU1K) by first installing a disk-like Anderson polyoxometalate, Co III Mo 6 VI O 24 m– , in size-matched micropores where the siting is established via difference electron density (DED) X-ray diffraction (XRD) experiments. Flowing H 2 S, while heating, reduces molybdenum(VI) ions to Mo(IV) and quantitatively replaces oxygen anions with sulfur anions (S 2– , HS – , S 2 2– ). DED maps show that MOF-templated POM-to-PTM conversion leaves clusters individually isolated in open-channel-connected micropores. Importantly, the structure of the immobilized cluster as determined, in part, by X-ray photoelectron spectroscopy (XPS), X-ray absorption fine structure (XAFS) analysis, and pair distribution function (PDF) analysis of total X-ray scattering agrees well with the theoretically simulated structure. PTM@MOF displays both electrocatalytic and photocatalytic competency for hydrogen evolution. Nevertheless, the initially installed PTM appears to be a precatalyst, gaining competency only after the loss of ~3 to 6 sulfurs and exposure to hydride-forming metal ions.

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

Room temperature analysis of dielectric function of ZnO-based thin film on fused quartz substrate

A set of sample consist of pure ZnO and Cu-doped ZnO film were grown on fused-quartz substrates using pulsed laser deposition (PLD) technique. Here, we report room temperature spectroscopic ellipsometry analysis (covering energy range of 0.5 to 6.3 eV) of pure ZnO film and Cu doped ZnO film at 8 in at. %. The thickness of pure ZnO and Cu-doped ZnO film using in this study is about 350 nm. To extract the dielectric function of ZnO thin film, multilayer modeling is performed which takes into account reflections at each interface through Fresnel coefficients. This method based on Drude-Lorentz models that connect with Kramers-Kronig relations. The best fitting of Ψ (amplitude ratio) and Δ (phase difference) taken by SE measurement are obtained reasonably well by mean the universal fitting of three different photon incident angles. The imaginary part of dielectric function (ε{sub 2}) show the broad peak at around 3.3 eV assigned as combination of optical band energy edge with excitonic states. The exitonic states could not be observed clearly in this stage. The evolution of extracted dielectric function is observable by introducing 8% Cu as indicated by decreasing of excitonic intensity. This result indicates the screening of excitonic state. This study will bring us to have a good undestanding for the role of Cu impurities for ZnO thin films.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Comparative analysis of the functional properties of human and mouse ferroportin

Ferroportin (Fpn)—expressed at the plasma membrane of macrophages, enterocytes, and hepatocytes—mediates the transfer of cellular iron into the blood plasma. Under the control of the iron-regulatory hormone hepcidin, Fpn serves a critical role in systemic iron homeostasis. Although we have previously characterized human Fpn, a great deal of research in iron homeostasis and disorders uses mouse models. By way of example, the flatiron mouse, a model of classical ferroportin disease, bears the mutation H32R in Fpn and is characterized by systemic iron deficiency and macrophage iron retention. The flatiron mouse also appears to exhibit a manganese phenotype, raising the possibility that mouse Fpn serves a role in manganese metabolism. At odds with this observation, we have found that human Fpn does not transport manganese, so we considered the possibility that a species difference could explain this discrepancy. We tested the hypothesis that mouse but not human Fpn can transport manganese and performed a comparative analysis of mouse and human Fpn. We examined the functional properties of human Fpn, mouse Fpn, and mutant mouse Fpn by using radiotracer assays in RNA-injected Xenopus oocytes. We found that neither mouse nor human Fpn transports manganese. Mouse and human Fpn share identical properties with respect to substrate profile, calcium dependence, optimal pH, and hepcidin sensitivity. We have also demonstrated that Fpn is not an ATPase pump. Our findings validate the use of mouse models of ferroportin function in iron homeostasis and disease.

Cell Biology↗
DOE OSTI2016

Density functional theory + U analysis of the electronic structure and defect chemistry of LSCF (La 0.5 Sr 0.5 Co 0.25 Fe 0.75 O 3-δ )

Reducing operating temperatures is a key step in making solid oxide fuel cell (SOFC) technology viable. A promising strategy for accomplishing this goal is employing mixed ion–electron conducting (MIEC) cathodes. La 1-x Sr x Co 1-y Fe y O 3-δ (LSCF) is the most widely employed MIEC cathode material; however, rational optimization of the composition of LSCF requires fundamental insight linking its electronic structure to its defect chemistry. To provide the necessary insight, density functional theory plus U (DFT+U) calculations are used to investigate the electronic structure of LSCF (xSr = 0.50, yCo = 0.25). The DFT+U calculations show that LSCF has a significantly different electronic structure than La 1-x Sr x FeO 3 because of the addition of cobalt, but that minimal electronic structure differences exist between La 0.5 Sr 0.5 Co 0.25 Fe 0.75 O 3 and La 0.5 Sr 0.5 Co 0.5 Fe 0.5 O 3 . The oxygen vacancy (V$-\atop{o}$) formation energy (ΔEf,vac) is calculated for V$-\atop{o}$ residing in different local environments within La 0.5 Sr 0.5 Co 0.25 Fe 0.75 O 3 . These results show that Co-V$-\atop{o}$-Co configurations have the highest ΔEf,vac, while Co-V$-\atop{o}$-Fe have the lowest ΔEf,vac and may act as traps for V$-\atop{o}$. We conclude that compositions with more Fe than Co are preferred because the additional Co-V$-\atop{o}$-Co sites would lead to higher overall ΔEf,vac (and lower V$-\atop{o}$ concentrations), while the trapping strength of the Image Co-V$-\atop{o}$-Fe sites is relatively weak (~0.3 eV).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRSDate not supplied

In-Depth Analysis of Subject Functional Performance and Subjective Feedback Data for Evaluating Argos Simulation Quality

Mechanical offloading systems such as the Active Response Gravity Offload System (ARGOS) at NASA Johnson Space Center (JSC) are used to simulate various partial gravity environments. ARGOS offloads pressurized suited subjects through a gimbaling pivot point system attached to a volumetric Portable Life Support System (PLSS). The pivot point can be configured to multiple locations with respect to the human-suit system center of gravity (CG). Previous work has tested and documented the interaction between different pivot point locations and measured CG. Observations indicated that small changes in pivot point location substantially affect the stability and functional performance (simulation quality) of a subject. This led to the development of a standardized gimbal assessment protocol to assess the functional performance of a pressurized suited subject as a function of the pivot point location, using the data obtained from a variety of planetary suit mobility tasks. As a result, an expansive repository of CG-related task metrics was generated from numerous ARGOS spacesuit test events, for different gimbal configurations and different test subjects. Based on the evaluation metrics and observed trends, several pivot point locations were iteratively identified to determine an “appropriate/optimal” configuration. This study thus describes the in-depth analysis of the CG evaluation metrics to better quantify trends and determine if specific factors are strongly associated with appropriate/optimal configurations. Quantitative and qualitative variables relating to subject task performance, subjective feedback, and anthropometry will be evaluated via probabilistic methods. The results from this study are expected to improve our understanding of optimal ARGOS gimbal settings, which will better inform the gimbal configuration identification process and improve simulation quality for extravehicular activity (EVA) training.

Joseph Yao↗
DOE OSTI2016

Functional and structural analysis of a highly-expressed Yersinia pestis small RNA following infection of cultured macrophages

Non-coding small RNAs (sRNAs) are found in practically all bacterial genomes and play important roles in regulating gene expression to impact bacterial metabolism, growth, and virulence. We performed transcriptomics analysis to identify sRNAs that are differentially expressed in Yersinia pestis that invaded the human macrophage cell line THP-1, compared to pathogens that remained extracellular in the presence of host. Using ultra high-throughput sequencing, we identified 37 novel and 143 previously known sRNAs in Y. pestis . In particular, the sRNA Ysr170 was highly expressed in intracellular Yersinia and exhibited a log2 fold change ~3.6 higher levels compared to extracellular bacteria. We found that knock-down of Ysr170 expression attenuated infection efficiency in cell culture and growth rate in response to different stressors. In addition, we applied selective 2’-hydroxyl acylation analyzed by primer extension (SHAPE) analysis to determine the secondary structure of Ysr170 and observed structural changes resulting from interactions with the aminoglycoside antibiotic gentamycin and the RNA chaperone Hfq. Interestingly, gentamicin stabilized helix 4 of Ysr170, which structurally resembles the native gentamicin 16S ribosomal binding site. Lastly, we modeled the tertiary structure of Ysr170 binding to gentamycin using RNA motif modeling. Integration of these experimental and structural methods can provide further insight into the design of small molecules that can inhibit function of sRNAs required for pathogen virulence.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Functional Meta-Analysis of the Proteomic Responses of Arabidopsis Seedlings to the Spaceflight Environment Reveals Multi-Dimensional Sources of Variability across Spaceflight Experiments

The human quest for sustainable habitation of extraterrestrial environments necessitates a robust understanding of life’s adaptability to the unique conditions of spaceflight. This study provides a comprehensive proteomic dissection of the Arabidopsis plant’s responses to the spaceflight environment through a meta-analysis of proteomics data from four separate spaceflight experiments conducted on the International Space Station (ISS) in different hardware configurations. Raw proteomics LC/MS spectra were analyzed for differential expression in MaxQuant and Perseus software. The analysis of dissimilarities among the datasets reveals the multidimensional nature of plant proteomic responses to spaceflight, impacted by variables such as spaceflight hardware, seedling age, lighting conditions, and proteomic quantification techniques. By contrasting datasets that varied in light exposure, we elucidated proteins involved in photomorphogenesis and skotomorphogenesis in plant spaceflight responses. Additionally, with data from an onboard 1 g control experiment, we isolated proteins that specifically respond to the microgravity environment and those that respond to other spaceflight conditions. This study identified proteins and associated metabolic pathways that are consistently impacted across the datasets. Notably, these shared proteins were associated with critical metabolic functions, including carbon metabolism, glycolysis, gluconeogenesis, and amino acid biosynthesis, underscoring their potential significance in Arabidopsis’ spaceflight adaptation mechanisms and informing strategies for successful space farming.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2016

A Structural, Functional, and Computational Analysis of BshA, the First Enzyme in the Bacillithiol Biosynthesis Pathway

Bacillithiol is a compound produced by several Gram-positive bacterial species, including the human pathogens Staphylococcus aureus and Bacillus anthracis. It is involved in maintaining cellular redox balance as well as the destruction of reactive oxygen species and harmful xenobiotic agents, including the antibiotic fosfomycin. BshA, BshB, and BshC are the enzymes involved in bacillithiol biosynthesis. BshA is a retaining glycosyltransferase responsible for the first committed step in bacillithiol production, namely the addition of N-acetylglucosamine to l-malate. Retaining glycosyltransferases like BshA are proposed to utilize an S N i-like reaction mechanism in which leaving group departure and nucleophilic attack occur on the same face of the hexose. However, significant questions regarding the details of how BshA and similar enzymes accommodate their substrates and facilitate catalysis persist. Here we report X-ray crystallographic structures of BshA from Bacillus subtilis 168 bound with UMP and/or GlcNAc-mal at resolutions of 2.15 and 2.02 Å, respectively. These ligand-bound structures, along with our functional and computational studies, provide clearer insight into how BshA and other retaining GT-B glycosyltransferases operate, corroborating the substrate-assisted, S N i-like reaction mechanism. In conclusion, the analyses presented herein can serve as the basis for the design of inhibitors capable of preventing bacillithiol production and, subsequently, help combat resistance to fosfomycin in various pathogenic Gram-positive microorganisms.

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

Final Report Systems Level Analysis of the Function and Adaptive Responses of Methanogenic Consortia

The purpose of this research was to determine whether the syntrophic microbial associations that are central to the functioning of methane-producing terrestrial wetlands can be predictively modeled with coupled multi-species genome-scale metabolic models. Such models are important because methane is an important greenhouse gas and there is a need to predictively model how the methane-producing microbial communities will respond to environmental perturbations, such as global climate change. The research discovered that the most prodigious methane-producing microorganisms on earth participate in a previously unrecognized form of energy exchange. The methane-producers Methanosaeta and Methanosarcina forge biological electrical connections with other microbes in order to obtain electrons to reduce carbon dioxide to methane. This direct interspecies electron transfer (DIET) was demonstrated in complex microbial communities as well as in defined co-cultures. For example, metatranscriptomic analysis of gene expression in both natural communities and defined co-cultures demonstrated that Methanosaeta species highly expressed genes for the enzymes for the reduction of carbon dioxide to methane. Furthermore, Methanosaeta’s electron-donating partners highly expressed genes for the biological electrical connections known as microbial nanowires. A series of studies involving transcriptomics, genome resequencing, and analysis of the metabolism of a series of strains with targeted gene deletions, further elucidated the mechanisms and energetics of DIET in methane-producing co-cultures, as well as in a co-culture of Geobacter metallireducens and Geobacter sulfurreducens, which provided a system for studying DIET with two genetically tractable partners. Genome-scale modeling of DIET in the G. metallireducens/G. sulfurreducens co-culture suggested that DIET provides more energy to the electron-donating partner that electron exchange via interspecies hydrogen transfer, but that the performance of DIET may be strongly influenced by environmental factors. These studies have significantly modified conceptual models for carbon and electron flow in methane-producing environments and have developed a computational framework for predictive modeling the influence of environmental perturbations on methane-producing microbial communities. The results have important implications for modeling the response of methane-producing microbial communities to climate change as well as for the bioenergy strategy of converting wastes and biomass to methane.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2011

SAAF: SANS data Analysis using Analytical Functions

The recently completed Extended Q-Range Small Angle Scattering Diffractometer (EQ-SANS) has put the focus on its software needs with renewed urgency. In a series of efforts, we aim at providing a complete set of software solutions on the EQ-SANS instrument. These programs include initial data processing, data correction and reduction, analytical model fitting to the scattering data, Monte Carlo simulation for structure determination, and virtual instrument simulation for experiment planning. SAAF is one such program for analytical data modeling. It takes the reduced EQ-SANS data and allows users to fit the data to analytical models. These models are easy to write. They can either be user written, or from the pre-supplied model library.

Data Analysis↗
DOE OSTI2018

CaFe 2 O 4 oxygen carrier characterization during the partial oxidation of coal in the chemical looping gasification application

The calcium ferrite (CaFe 2 O 4 ) oxygen carrier characterization during chemical looping coal gasification was conducted using X-ray diffraction and Raman spectroscopic analysis. Density functional theory (DFT) analysis and experimental data were used to elucidate the mechanism for the selective oxidation of coal char. The Raman spectroscopic analyses indicated that the initial reduction of CaFe 2 O 4 were at the Fe (8) O 6 and Fe (7) O 6 octahedral sites which are related to the morphological changes at the [4 0 0] and [2 1 2] crystal planes. After the initial reduction, the Raman spectroscopic data indicated the remaining oxygen from Fe-O sites containing Ca (e.g. Fe–O–Ca) participated in the reduction reaction. Deep reduction of the CaFe 2 O 4 led to the removal of oxygen from the Fe–O–Ca bonds, indicated by the decrease in Raman intensities of the corresponding species, and the appearance of the CaO and Fe 0 . The oxygen ion diffusion controlling regime was due to the oxygen transfer occurring at the Fe octahedral sites. Furthermore, these results indicated calcium functions to control both the movement of oxygen ions through the solid and the rate of carbon oxidation in coal char leading to the selective oxidation to produce CO, the desirable product of the chemical looping gasification application.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗