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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 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Resolving Lipid Structures for Threat-Agnostic Signatures

Development of threat-agnostic biosignatures is critical for the detection of and response to biological threats that go beyond the historical list-based approach. Lipids are a class of structurally diverse biomolecules that hold great promise as relevant threat-agnostic biosignatures, yet the fundamental challenge of resolving and decoding structural differences among lipids remains an obstacle in the pursuit of signature development. Structural analysis of complex lipids remains stymied due to spectral complexity and the inability to resolve low abundance lipids. To address these challenges, we integrated ozonolysis with ion mobility mass spectrometry (IMS-MS) analysis to determine the structural information for complex lipid species and (2) reduced lipid sample complexity prior to introduction into the IMS-MS using normal phase high pressure liquid chromatography (HPLC) to enable the ozonolysis of low abundance lipids. We applied these new capabilities to define the lipid structures in antimicrobial resistant (AMR) and antimicrobial susceptible (AMS) biothreat organism Yersinia pestis and cells infected with Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2) variants.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2012

Refinement of Modeling Techniques for the Structural Evaluation of Hanford Single-Shell Nuclear Waste Storage Tanks

Abstract: A total of 149 tanks out of 177 at the Hanford Site (in Washington State, USA) belong to the first generation of underground nuclear waste storage tanks known as single shell tanks (SSTs). These tanks were constructed between 1943 and 1964 and are well beyond their design life. All the SSTs had been removed from active service by November 1980 and have been later interim stabilized by removing the pumpable liquids. The remaining waste in the tanks is in the form of salt cake and sludge awaiting r permanent disposal.. The evaluation of the structural integrity of these tanks is of utmost importance not only for the continued safe storage of the waste until waste retrieval and closure, but also to assure safe retrieval and closure operations. This article discusses the structural analysis approach, modeling challenges and issues encountered during the ongoing analysis of record (AOR) for evaluating the structural integrity of the SSTs. There are several geometrical and material nonlinearities and uncertainties to be dealt with while performing the modern finite element analysis of these tanks. Several studies were conducted to refine the models in order to minimize modeling artifacts introduced by soil arching, boundary effects, concrete cracking, and concrete-soil interface behavior. The analysis takes into account the temperature history of the tanks and allowable mechanical operating loads of these tanks for proper estimation of creep strains and thermal degradation of material properties. The loads imposed in the AOR models also include anticipated loads that these tanks may see during waste retrieval and closure. Due to uncertainty in a number of inputs to the models, sensitivity studies were conducted to address questions related to the boundary conditions to realistically or conservatively represent the influence of surrounding tanks in a tank farm, the influence of backfill excavation slope, the extent of backfill and the total extent of undisturbed soil surrounding the backfill. The article also discusses the criteria and design standards used for evaluating the structural integrity of these underground concrete tanks. Because of the non-availability of complete data on the thermal and operating history for many of the individual tanks, some of the data was assumed or interpolated. However, the models developed for the analysis of record represent the bounding scenarios and include the worst and extreme loading cases that the tanks were subjected to or anticipated. The modeling refinement techniques followed in the AOR resulted in conservative estimates for force and moment demands at various sections in the concrete tanks. The SSTs are classified into 4 types as per their configuration and capacity. This article discusses the modeling aspects related to two types of SSTs that have been analyzed until now. The TOLA results combined with seismic demands from seismic analysis for the analysis of record indicate that the tanks analyzed are structurally stable as per the evaluation criteria established. These results are presented in a separate article. The modeling techniques, methodology and evaluation criteria developed for evaluating the structural integrity of SSTs at Hanford are in general applicable to any similar tanks or underground concrete storage structures.

Single Shell Tank, Structural analysis, Structural↗
DOE OSTI2014

Isolating the anthropogenic component of Arctic warming

Structural equation modeling is used in statistical applications as both confirmatory and exploratory modeling to test models and to suggest the most plausible explanation for a relationship between the independent and the dependent variables. Although structural analysis cannot prove causation, it can suggest the most plausible set of factors that influence the observed variable. Here, we apply structural model analysis to the annual mean Arctic surface air temperature from 1900 to 2012 to find the most effective set of predictors and to isolate the anthropogenic component of the recent Arctic warming by subtracting the effects of natural forcing and variability from the observed temperature. We also find that anthropogenic greenhouse gases and aerosols radiative forcing and the Atlantic Multidecadal Oscillation internal mode dominate Arctic temperature variability. Finally, our structural model analysis of observational data suggests that about half of the recent Arctic warming of 0.64 K/decade may have anthropogenic causes.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2012

Crystal Structure of BamB from Pseudomonas aeruginosa and Functional Evaluation of Its Conserved Structural Features

The assembly of β-barrel Outer Membrane Proteins (OMPs) in the outer membrane is essential for Gram-negative bacteria. The process requires the β-Barrel Assembly Machine (BAM), a multiprotein complex that, in E. coli, is composed of the OMP BamA and four lipoproteins BamB-E. Whereas BamA and BamD are essential, deletion of BamB, C or E produce membrane permeability defects. Here we present the high-resolution structure of BamB from Pseudomonas aeruginosa. This protein can complement the deletion of bamB in E. coli indicating that they are functionally equivalent. Conserved structural features include an eight-bladed β-propeller fold stabilized by tryptophan docking motifs with a central pore about 8 Å in diameter at the narrowest point. This pore distinguishes BamB from related b-propellers, such as quinoprotein dehydrogenases. However, a double mutation designed to block this pore was fully functional indicating that the opening is not essential. Two loops protruding from the bottom of the propeller are conserved and mediate binding to BamA. Conversely, an additional loop only present in E. coli BamB is not required for function. A cluster of highly conserved residues in a groove between blades 6 and 7 is crucial for proper BamB folding or biogenesis. It has been proposed that BamB may bind nascent OMPs by β-augmentation to its propeller outer strands, or recognize the aromatic residue signature at the C-terminus of OMPs. However, Isothermal Titration Calorimetry experiments and structural analysis do not support these proposals. The structural and mutagenesis analysis suggests that the main function of BamB is to bind and modulate BamA, rather than directly interact with nascent OMPs.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Effect of Cr doping in the microstructure, electrical and magnetic properties of In{sub 2−x}Cr{sub x}O{sub 3} system (x=0.1 and x=0.2)

In this paper a sol-gel method followed by a spin coating technique have been used to fabricate In{sub 2−x}Cr{sub x}O{sub 3} thin films with x=0.1 and 0.2. The structural analysis using an x-ray diffractometer showed that films have bixibyte cubic structure with good orientations to (222) directions. Microstructure analysis using atomic force microscope showed that sample with x=0.1 has clear pores and the particles tend to agglomerate and collect together with some holes seen on surface at x=0.2. The structure analysis using transmission electron microscope showed that the average grain size is 7.9 nm and 5.6 nm for samples x=0.1 and 0.2, respectively. The electrical measurements were carried out using Hall effect measurement system. The resistivity, carrier concentration and mobility for sample with x=0.1 is 27ohm.cm, 8.1×1016 cm{sup −3} and 1.9 cm{sup 2}V{sup −1}S{sup −1}, respectively and for higher dopant the film became insulator. The film with x=0.1 has metallic like behavior at 80-165K while semiconducting like behavior observed at 170-300K. Thermal activated conduction band and hoping conduction models have been used to estimate conducting mechanism in semiconducting part. Both samples show magnetic behavior at room temperature. The magnetic moment decreased from 6.7 emu/cm{sup 3} for x=0.1 to 2.8 emu/cm{sup 3} for x=0.2 while the coercivity increased from 85 Oe for x=0.1 to 120 Oe for x=0.2.

36 MATERIALS SCIENCE↗