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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 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Atomistic Defect Makes a Phase Plate for the Generation and High-Angular Splitting of Electron Vortex Beams

Topological defects in solid-state materials by breaking the translational symmetry offer emerging properties that are not present in their parental phases. For example, edge dislocations—the 2π phase-winding topological defects—in antiferromagnetic NiO crystals can exhibit ferromagnetic behaviors. We study how these defects could give rise to topological orders when they interact with a high-energy electron beam. To probe this interaction, we formed a coherent electron nanobeam in a scanning transmission electron microscope and recorded the far-field transmitted patterns as the beam steps through the edge dislocation core in [001] NiO. Surprisingly, we found the amplitude patterns of the <020> Bragg disks evolve in a similar manner to the evolution of an annular solar eclipse. Using the ptychographic technique, we recovered the missing phase information in the diffraction plane and revealed the topological phase vortices in the diffracted beams. Through atomic topological defects, the wave function of electrons can be converted from plane wave to electron vortex. Technologically, this approach provides a feasible route for the fabrication of phase plates that can generate electron vortex beams with an angular separation that is three orders of magnitude larger than what traditional nanofabrication technology can offer. This advance will enable the collection of magnetic circular dichroism spectra with high spatial resolution and high efficiency, boosting the understanding of the relationship between symmetry breaking and magnetic property of individual topological defect at the atomic scale.

36 MATERIALS SCIENCE↗
DOE OSTI2020

SPLIT: Stable Protein Coacervation Using a Light Induced Transition

Protein coacervates serve as hubs to concentrate and sequester proteins and nucleotides and thus function as membraneless organelles to manipulate cell physiology. We have engineered a coacervating protein to create tunable, synthetic membraneless organelles that assemble in response to a single pulse of light. Coacervation is driven by the intrinsically disordered RGG domain from the protein LAF-1, and opto-responsiveness is coded by the protein PhoCl, which cleaves in response to 405 nm light. We developed a fusion protein containing a solubilizing maltose-binding protein domain, PhoCl, and two copies of the RGG domain. Several seconds of illumination at 405 nm is sufficient to cleave PhoCl, removing the solubilization domain and enabling RGG-driven coacervation within minutes in cellularsized water-in-oil emulsions. An optimized version of this system displayed light-induced coacervation in Saccharomyces cerevisiae. Finally, the methods described here provide novel strategies for inducing protein phase separation using light.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗