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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 937 records · Page 52
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Chiral assemblies of pinwheel superlattices on substrates

The unique topology and physics of chiral superlattices make their self-assembly from nanoparticles highly sought after yet challenging in regard to (meta)materials. In this report we show that tetrahedral gold nanoparticles can transform from a perovskite-like, low-density phase with corner-to-corner connections into pinwheel assemblies with corner-to-edge connections and denser packing. Whereas corner-sharing assemblies are achiral, pinwheel superlattices become strongly mirror asymmetric on solid substrates as demonstrated by chirality measures. Liquid-phase transmission electron microscopy and computational models show that van der Waals and electrostatic interactions between nanoparticles control thermodynamic equilibrium. Variable corner-to-edge connections among tetrahedra enable fine-tuning of chirality. The domains of the bilayer superlattices show strong chiroptical activity as identified by photon-induced near-field electron microscopy and finite-difference time-domain simulations. The simplicity and versatility of substrate-supported chiral superlattices facilitate the manufacture of metastructured coatings with unusual optical, mechanical and electronic characteristics.

42 ENGINEERING↗
DOE OSTI2018

Unique Symmetry-Breaking Phenomenon during the Self-assembly of Macroions Elucidated by Simulation

Various soluble hydrophilic macroions can self-assemble into hollow, spherical, monolayered supramolecular “blackberry”-type structures, despite their like-charged nature. However, how the 3-D symmetrical macroions prefer to form 2-D monolayers in bulk solution, especially for the highly symmetrical “Keplerate” polyoxometalates and functionalized C 60 macroions has been a mystery. Through molecular dynamics simulations, using a model specifically designed for macroions in solution, the mechanism of this intriguing symmetry-breaking process is found to be related to the apparently asymmetric charge distribution on the surface of macroions in the equatorial belt area (the area which can be effectively involved in the counterion-mediated attraction). As a result, the electric field lines around macroions during the self-assembly process clearly show that the symmetry-breaking happens at the dimer level effectively defining the plane of the self-assembly. These findings are expected to contribute to our fundamental knowledge of complex solution systems that are found in many fields from materials science to biological phenomena.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Lipid membrane templated misfolding and self-assembly of intrinsically disordered tau protein

The aggregation of the intrinsically disordered tau protein into highly ordered β-sheet-rich fibrils is implicated in the pathogenesis of a range of neurodegenerative disorders. The mechanism of tau fibrillogenesis remains unresolved, particularly early events that trigger the misfolding and assembly of the otherwise soluble and stable tau. We investigated the role the lipid membrane plays in modulating the aggregation of three tau variants, the largest isoform hTau40, the truncated construct K18, and a hyperphosphorylation-mimicking mutant hTau40/3Epi. Despite being charged and soluble, the tau proteins were also highly surface active and favorably interacted with anionic lipid monolayers at the air/water interface. Membrane binding of tau also led to the formation of a macroscopic, gelatinous layer at the air/water interface, possibly related to tau phase separation. At the molecular level, tau assembled into oligomers composed of ~ 40 proteins misfolded in a β-sheet conformation at the membrane surface, as detected by in situ synchrotron grazing-incidence X-ray diffraction. Concomitantly, membrane morphology and lipid packing became disrupted. Our findings support a general tau aggregation mechanism wherein tau’s inherent surface activity and favorable interactions with anionic lipids drive tau-membrane association, inducing misfolding and self-assembly of the disordered tau into β-sheet-rich oligomers that subsequently seed fibrillation and deposition into diseased tissues.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Device-quality, reconfigurable metamaterials from shape-directed nanocrystal assembly

Significance Colloidal nanocrystals with defined sizes and shapes are ideal building blocks for nanofabrication. However, the ability to arbitrarily arrange them on surfaces with control over their orientation remains elusive. Here we report a shallow-template-assisted DNA-mediated assembly strategy to precisely arrange colloidal nanocrystals on surfaces, with single-particle control across submillimeter areas. In addition, the oligonucleotide bonds between the nanocrystals and substrate can be reversibly expanded and contracted enabling postsynthetic tunability of the assembled structures. Using this approach, we synthesized a nanocrystal-based, dynamically tunable metasurface (an anomalous reflector), thereby illustrating the potential for unique device construction via DNA programmable assembly.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Hierarchical supramolecular assembly of a single peptoid polymer into a planar nanobrush with two distinct molecular packing motifs

Significance The preparation of hierarchical biomimetic nanostructures remains a challenging task. Bioinspired peptoid polymers offer a promising opportunity to encode assembly information within the component chains. Here, we report a one-pot preparation of planar nanobrush structures from poly(ethyleneglycol)- block -poly( N -octylglycine) based on tuning the interplay of crystallization and solvophobicity. Each nanobrush assembly is composed of two distinct structural domains, which form sequentially by control of the solution temperature, and contain distinct molecular packing motifs. Micellar intermediates first assemble into linear arrays at elevated temperature in a mesophase state, followed by lateral, crystallization-driven growth in a living manner upon cooling. Precise control over the nanobrush dimensions could be achieved. The structural tunability and excellent biocompatibility of polypeptoids offer great potential for nanomaterials inaccessible previously.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Concept Descriptions for the VTR Rabbit System and Driver Fuel Test Assemblies

Two of the experiment vehicles being developed for the Versatile Test Reactor (VTR) are presented here. The first is a rabbit system that will enable rapid insertion of small test capsules into the high fast flux of the VTR core for relatively short durations. The rabbit concept development includes the construction/demonstration of a near-full-scale system in a deep-water pool to demonstrate functionality, development of a concept of operations and initial procedures, and validation of thermal-hydraulic modeling. In addition, modeling efforts are underway to simulate the thermal and neutronic environment of a rabbit capsule. The second type of experiment vehicle presented here is a driver fuel test assembly for inserting fuel and materials tests into the core by replacing a driver fuel assembly. Here, a novel design for dismountable test assemblies is proposed for the VTR.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2021

Contributions of environmental and maternal transmission to the assembly of leaf fungal endophyte communities

Leaf fungal endophytes (LFEs) contribute to plant growth and responses to stress. Fungi colonize leaves through maternal transmission, e.g. via the seed, and through environmental transmission, e.g. via aerial dispersal. The relative importance of these two pathways in assembly and function of the LFE community is poorly understood. We used amplicon sequencing to track switchgrass (Panicum virgatum) LFEs in a greenhouse and field experiment as communities assembled from seed endophytes and rain fungi (integration of wet and dry aerial dispersal) in germinating seeds, seedlings, and adult plants. Rain fungi varied temporally and hosted a greater portion of switchgrass LFE richness (greater than 65%) than were found in seed endophytes (greater than 25%). Exposure of germinating seeds to rain inoculum increased dissimilarity between LFE communities and seed endophytes, increasing the abundance of rain-derived taxa, but did not change diversity. In the field, seedling LFE composition changed more over time, with a decline in seed-derived taxa and an increase in richness, in response to environmental transmission than LFEs of adult plants. Furthermore, we show that environmental transmission is an important driver of LFE assembly, and likely plant growth, but its influence depends on both the conditions at the time of colonization and plant life stage.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

PyMDA : microcrystal data assembly using Python

The recent developments at microdiffraction X-ray beamlines are making microcrystals of macromolecules appealing subjects for routine structural analysis. Microcrystal diffraction data collected at synchrotron microdiffraction beamlines may be radiation damaged with incomplete data per microcrystal and with unit-cell variations. A multi-stage data assembly method has previously been designed for microcrystal synchrotron crystallography. Here the strategy has been implemented as a Python program for microcrystal data assembly ( PyMDA ). PyMDA optimizes microcrystal data quality including weak anomalous signals through iterative crystal and frame rejections. Beyond microcrystals, PyMDA may be applicable for assembling data sets from larger crystals for improved data quality.

36 MATERIALS SCIENCE↗
DOE OSTI2022

SourceFinder: a Machine-Learning-Based Tool for Identification of Chromosomal, Plasmid, and Bacteriophage Sequences from Assemblies

High-throughput genome sequencing technologies enable the investigation of complex genetic interactions, including the horizontal gene transfer of plasmids and bacteriophages. However, identifying these elements from assembled reads remains challenging due to genome sequence plasticity and the difficulty in assembling complete sequences. In this study, we developed a classifier, using random forest, to identify whether sequences originated from bacterial chromosomes, plasmids, or bacteriophages. The classifier was trained on a diverse collection of 23,211 chromosomal, plasmid, and bacteriophage sequences from hundreds of bacterial species. In order to adapt the classifier to incomplete sequences, each complete sequence was subsampled into 5,000 nucleotide fragments and further subdivided into k-mers. This three-class classifier succeeded in identifying chromosomes, plasmids, and bacteriophages using k-mer distributions of complete and partial genome sequences, including simulated metagenomic scaffolds with minimum performance of 0.939 area under the receiver operating characteristic curve (AUC). This classifier, implemented as SourceFinder, has been made available as an online web service to help the community with predicting the chromosomal, plasmid, and bacteriophage sources of assembled bacterial sequence data (https://cge.food.dtu.dk/services/SourceFinder/).

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Complete Assembly of Circular and Chloroplast Genomes Based on Global Optimization

This paper focuses on the last two stages of genome assembly, namely scaffolding and gap-filling, and shows that they can be solved as part of a single optimization problem. Our approach is based on modeling genome assembly as a problem of finding a simple path in a specific graph that satisfies as many as possible of the distance constraints encoding the insert-size information. We formulate it as a mixed-integer linear programming problem and apply an optimization solver to find the exact solutions on a benchmark of chloroplasts. We show that the presence of repetitions in the set of unitigs is the main reason for the existence of multiple equivalent solutions that are associated to alternative subpaths. We also describe two sufficient conditions and we design efficient algorithms for identifying these subpaths. Comparisons of the results achieved by our tool with the ones obtained with recent assemblers are presented.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Metagenome-assembled genomes from topsoils along a hillslope water gradient across early snowmelt to late summer in East River, CO

Drought is changing the American Mountain West at unprecedented rates with unknown consequences to soil microbiome composition and function. As a part of LBNL Watershed Science Focus Area (SFA), we investigated shifts in microbial community and transcriptional activity on a subalpine conifer-meadow transition zone throughout the summer of 2023 as soil dried down. This work took place in Crested Butte, CO on Snodgrass mountain, using a proxy for drought conditions.Here we present metagenome assembled genomes (MAGs) for the bacterial and archaeal community at 0-10cm from three sites along a hillslope water gradient across five timepoints from early snowmelt to late summer. 42 metagenomes were sequenced at Joint Genome Institute (JGI) and can be found under the JGI GOLD (Genomes Online Database) sequencing project Gs0166660. Metagenomes were assembled through an inhouse pipeline (see methods), binned using four autobinners (concoct, maxbin2, metabat2, and vamb) and consolidated using dastool. The consolidated bins from all metagenomes were pooled, filtered by completeness (>70%) and contamination (<10%), and dereplicated at 95% ANI using drep. This dataset (1) a zip file of 157 MAGs (as fasta files, Gs0166660_bins_tar.gz), (2) sample metadata file with sample IGSNs (International Generic Sample Numbers) (samples.csv), (3) bounding box coordinates for the sampled locations (Gs0166660.kml), (4) metagenome assembly and coassembly metadata file listing IMG/M (Integrated Microbial Genomes/Metagenomes) metagenome accessions linking samples to metagenomes (EastRiver_Drought_ESSDive_Metadata.csv), (5) location metadata file (locations.csv), (6) file-level metadata file (flmd.csv) and (7) data dictionary (dd.csv) file.This work was supported by the Watershed Function Science Focus Area at Lawrence Berkeley National Laboratory funded by the US Department of Energy, Office of Science, Biological and Environmental Research under Contract No. DE-AC02-05CH11231.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Controlled synthesis and ordered assembly of Co 3 O 4 nanowires using genetically engineered bacterial flagella as biotemplates (Final Technical Report)

The major goals of the project are to gain a fundamental understanding on the influence of the displayed peptides and other processing parameters on the flagella assembly and the resulting biomimetic control over the synthesis and assembly of Co 3 O 4 nanoparticles (NPs) and nanowires (NWs). To pursue these goals, we designed two specific aims: Aim 1: Understanding the self-assembly of genetically engineered flagella and its outcome for site-specific nucleation and growth of Co 3 O 4 NPs and NWs. Aim 2: Understanding controllable alignment of 1D Co 3 O 4 -flagella NWs into highly ordered 2D and 3D structures.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

16S rRNA Amplicon sequence data and community assembly process file

Soils along a salinity gradient from a coastal forested floodplain (Beaver Creek in Western Washington) were analyzed for their microbial community composition and community assembly processes. These files contain processed 16S rRNA amplicon sequences into OTU table, the corresponding tree file, metadata, community assembly process analysis and results, microbial phyla abundances, and codes evaluating BNTI indices and community assembly process estimates.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

1,8-Dihydroxy Naphthalene—A New Building Block for the Self-Assembly with Boronic Acids and 4,4′-Bipyridine to Stable Host–Guest Complexes with Aromatic Hydrocarbons

The new Lewis acid–base adducts of general formula X(nad)B←NC5H4-C5H4N→B(nad)X [nad = 1,8-O2C10H6, X = C6H5 (2c), 3,4,5-F3-C6H2 (2d)] were synthesized in high yields via reactions of 1,8-dihydroxy naphthalene [nadH2] and 4,4′-bipyridine with the aryl boronic acids C6H5B(OH)2 and 3,4,5-F3-C6H2B(OH)2, respectively, and structurally characterized by multi-nuclear NMR spectroscopy and SCXRD. Self-assembled H-shaped Lewis acid–base adduct 2d proved to be effective in forming thermally stable host–guest complexes, 2d × solvent, with aromatic hydrocarbon solvents such as benzene, toluene, mesitylene, aniline, and m-, p-, and o-xylene. Crystallographic analysis of these solvent adducts revealed host–guest interactions to primarily occur via π···π contacts between the 4,4′-bipyridyl linker and the aromatic solvents, resulting in the formation of 1:1 and 1:2 host–guest complexes. Thermogravimetric analysis of the isolated complexes 2d × solvent revealed their high thermal stability with peak temperatures associated with the loss of solvent ranging from 122 to 147 °C. 2d, when self-assembled in an equimolar mixture of m-, p-, and o-xylene (1:1:1), preferentially binds to o-xylene. Collectively, these results demonstrate the ability of 1,8-dihydroxy naphthalene to serve as an effective building block in the selective self-assembly to supramolecular aggregates through dative covalent N→B bonds.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Assembly and Repair of Photosystem II in Chlamydomonas reinhardtii

Oxygenic photosynthetic organisms use Photosystem II (PSII) to oxidize water and reduce plastoquinone. Here, we review the mechanisms by which PSII is assembled and turned over in the model green alga Chlamydomonas reinhardtii. This species has been used to make key discoveries in PSII research due to its metabolic flexibility and amenability to genetic approaches. PSII subunits originate from both nuclear and chloroplastic gene products in Chlamydomonas. Nuclear-encoded PSII subunits are transported into the chloroplast and chloroplast-encoded PSII subunits are translated by a coordinated mechanism. Active PSII dimers are built from discrete reaction center complexes in a process facilitated by assembly factors. The phosphorylation of core subunits affects supercomplex formation and localization within the thylakoid network. Proteolysis primarily targets the D1 subunit, which when replaced, allows PSII to be reactivated and completes a repair cycle. While PSII has been extensively studied using Chlamydomonas as a model species, important questions remain about its assembly and repair which are presented here.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Dynamic Self-Assembly of Polyelectrolyte Composite Nanomaterial Film

The aim of this study is not only to investigate the feasibility of using PAH (polyallylamine hydrochloride) and PSS (poly styrene-4-sulfonic acid sodium salt) to prepare a film via a layer by layer self-assembly process entrained with silver nanoparticles, but also to show that the silver nanoparticles crystalline structure can be defined and deposited on the surface of the substrate in the desired alignment structure and manner, which is of great help to research on the LBL method in the cellulose field. The effect of outermost layer variation, assembly layers, and composition of multilayers on the formation of the LBL structure on a nanofibrillated cellulose (NFC)/polyvinyl alcohol (PVA) substrate was investigated. The deposition of PAH and PSS was monitored by Fourier-transform infrared spectroscopy (FT-IR). The morphology of the LBL film layers was observed by scanning electron microscope (SEM) and atomic force microscope (AFM). Furthermore, thermal degradation properties were investigated by thermogravimetric analysis (TGA), and physical properties of multilayer films were tested by a universal mechanical tester. The results reveal that PAH and PSS can be readily deposited on a NFC/PVA substrate by using LBL methodology to prepare self-assembled polyelectrolyte multilayer films. The surface morphology of the LBL composite changed from negative to positive charged depending on the final LBL treatment. Also, according to SEM and AFM analysis, silver nanoparticles were well dispersed in the (PAH/PSS) film, which significantly improved the thermal stability of the composite films.

36 MATERIALS SCIENCE↗
NASA NTRS2003

Metrics for in-space telescope assembly techniques

Reliable metrics are not yet available for choosing among human and robotic assets for space-based construction and servicing of large space telescopes. Using FAIR-DART as a reference design, we generated example event sequences for telescope assembly scenarios in enough detail to identify infrastructure assumptions and technology requirements. A systems trade among human and robotic techniques (human EVA, on-site telerobotic, ground-in-the- loop robotic, commanded or sequenced robotic, and autonomous/decision-making robotic) helped us to define key metrics in the human-robotic trade space, including quality, time, cost, and risk. Our methodology included examining representative end-member scenarios. Case A treated each step in the assembly sequence as if all other steps have no on-site human involvement, and Case B treated each step as if human EVA is already involved in all other steps. With this trade, we identified key enabling technologies and infrastructure for space-based assembly and servicing of large space telescopes.

space telescopes human and robotic in-space assemb↗
NASA NTRS2016

System Design and Implementation of the Detector Assembly of the Astro-H Soft X-Ray Spectrometer

The soft x-ray spectrometer (SXS) onboard Astro-H presents to the science community unprecedented capability (less than 7 eV at 6 keV) for high-resolution spectral measurements in the range of 0.5-12 keV to study extended celestial sources. At the heart of this SXS is the x-ray calorimeter spectrometer (XCS) where detectors (calorimeter array and anticoincidence detector) operate at 50 mK, the bias circuit operates at nominal 1.3 K, and the first stage amplifiers operateat 130 K, all within a nominal 20 cm envelope. The design of the detector assembly in this XCS originates from the Astro-E x-ray spectrometer (XRS) and lessons learned from Astro-E and Suzaku. After the production of our engineering model, additional changes were made in order to improve our flight assembly process for better reliability and overall performance. In this poster, we present the final design and implementation of the flight detector assembly, show comparison of parameters and performance to Suzakus XRS, and list susceptibilities to other subsystems as well as our lessons learned.

soft x-ray spectrometer↗