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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Atomic-Scale Characterization of Dilute Dopants in Topological Insulators via STEM–EDS Using Registration and Cell Averaging Techniques

Magnetic dopants in three-dimensional topological insulators (TIs) offer a promising avenue for realizing the quantum anomalous Hall effect (QAHE) without the necessity for an external magnetic field. Understanding the relationship between site occupancy of magnetic dopant elements and their effect on macroscopic property is crucial for controlling the QAHE. By combining atomic-scale energy-dispersive X-ray spectroscopy (EDS) maps obtained by aberration-corrected scanning transmission electron microscopy (AC-STEM) and novel data processing methodologies, including semi-automatic lattice averaging and frame registration, we have determined the substitutional sites of Mn atoms within the 1.2% Mn-doped Sb 2 Te 3 crystal. More importantly, the methodology developed in this study extends beyond Mn-doped Sb 2 Te 3 to other quantum materials, traditional semiconductors, and even electron irradiation sensitive materials.

36 MATERIALS SCIENCE↗
DOE OSTI2026

JUMP Into STEM 2018-2025: Challenge Highlights and Implementation Guidance

Building sciences and technology directly impact human health, productivity, and resource consumption (e.g., energy and critical minerals). Addressing emerging challenges in this field requires skilled building science professionals. JUMP into STEM sought to inspire the next generation of building scientists through a real-world competition that introduced participants to the field and connected them with national laboratory and industry professionals. This report highlights select challenges from past competitions which are tailored for academic and industry professionals who aim to develop or recruit multidisciplinary talent. It also includes additional guidance to support the effective replication of these challenges.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2026

Multi-Semester Mentoring and GPA Trajectories in SPINS: A Longitudinal Program Evaluation of STEM Scholars

This exploratory longitudinal program evaluation examined GPA trajectories among 14 STEM scholars participating in the Scholarly Partnership in Nuclear Security (SPINS) mentoring program at an HBCU. Using de-identified administrative data (37 scholar-semester observations), the study compared baseline and latest term GPAs anchored to each scholar’s first funded semester. A Wilcoxon signed-rank test was used to assess within-student change. Mean GPA increased modestly from 3.46 (SD = 0.30) at baseline to 3.61 (SD = 0.33) at the latest observed semester, with 12 of 14 scholars (85.7%) showing net improvement (median change = +0.12). The Wilcoxon signed-rank test indicated a statistically significant positive shift (W = 18, p = 0.030). However, scholars entered the program with a high baseline GPA, and ceiling effects were evident for several participants. Grounded in Social Cognitive Career Theory, findings suggest that multi-semester participation in SPINS is associated with GPA stability and modest improvement in an already high-performing cohort. Results should be interpreted cautiously given the small sample size and single-group design. The study highlights the value of sustained, culturally responsive mentoring at an HBCU while underscoring the need for larger evaluations with comparison cohorts and broader psychosocial outcomes. An evidence-informed mentoring framework is proposed to strengthen multi-semester support.

42 ENGINEERING↗
DOE OSTI2024

Direct Fabrication of Atomically Defined Pores in MXenes Using Feedback-Driven STEM

Controlled fabrication of nanopores in 2D materials offer the means to create robust membranes needed for ion transport and nanofiltration. Techniques for creating nanopores have relied upon either plasma etching or direct irradiation; however, aberration-corrected scanning transmission electron microscopy (STEM) offers the advantage of combining a sub-Å sized electron beam for atomic manipulation along with atomic resolution imaging. Here, for this work, a method for automated nanopore fabrication is utilized with real-time atomic visualization to enhance the mechanistic understanding of beam-induced transformations. Additionally, an electron beam simulation technique, Electron-Beam Simulator (E-BeamSim) is developed to observe the atomic movements and interactions resulting from electron beam irradiation. Using the MXene Ti 3 C 2 T x , the influence of temperature on nanopore fabrication is explored by tracking atomic transformations and find that at room temperature the electron beam irradiation induces random displacement and results in titanium pileups at the nanopore edge, which is confirmed by E-BeamSim. At elevated temperatures, after removal of the surface functional groups and with the increased mobility of atoms results in atomic transformations that lead to the selective removal of atoms layer by layer. This work can lead to the development of defect engineering techniques within functionalized MXene layers and other 2D materials.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Twist-Angle-Dependent Excitons in Moiré MoTe 2 Visualized by Cryogenic STEM and Monochromated EELS

van der Waals twisted bilayers of transition-metal dichalcogenides exhibit diverse excitonic phenomena arising from moiré superlattices and lattice reconstruction. While interlayer strain and relaxation reshape their electronic bands, their nanoscale influence on the excitonic fine structure remains poorly understood. Here, we study the interplay between spin–orbit coupling (SOC) and the moiré lattice by probing excitons in H-type twisted (∼8-layer × 8-layer) MoTe 2 using atomic-resolution scanning transmission electron microscopy (STEM) combined with monochromated electron energy loss spectroscopy (EELS) at cryogenic temperature. Spatially resolved spectra reveal moiré-site-dependent variations in excitonic absorption, including modulation of the X B exciton across the moiré unit cell. We find that SOC in MoTe 2 increases with the twist angle within the studied range (2–4.5°), with the largest value observed at 4°. Furthermore, these findings establish the twist angle as a tunable parameter for SOC via moiré engineering and link local structural relaxation to excitonic fine structure in twisted MoTe 2 .

cryogenic STEM/EELS↗
DOE OSTI2025

Emergence of lignin-carbohydrate interactions during plant stem maturation visualized by solid-state NMR

Lignification waterproofs and strengthens secondary plant cell walls but increases the energy cost of sugar release for biofuels. The physical association between lignin and the carbohydrate scaffold that accommodates lignin polymerization, along with the distinct roles of lignin units and carbohydrate partners during lignification, remain unclear. Here, we map lignin-carbohydrate spatial proximity by solid-state NMR in 13 C-labeled Arabidopsis inflorescence stems during secondary cell wall formation. Analyses include wild-type plants and mutants that selectively or globally disrupt lignin biosynthesis. Mature walls in basal regions show enrichment of S-lignin and dense carbohydrate-lignin packing. Acetylated xylan predominantly associates with S-lignin, while methylated pectin unexpectedly interacts with G-lignin during early-stage lignification. The importance of S-lignin in stabilizing the carbohydrate-lignin interface is highlighted by weak lignin-carbohydrate contacts and compromised mechanical properties in the low-S fah1 mutant, whereas the ref3 mutant, despite reduced lignin content, remains unaffected due to a high S/G ratio. Thus, molecular mixing patterns, rather than lignin content, critically determine the structure and properties of lignocellulosic materials.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Difficult Measurements of Materials Systems at Cryogenic Temperatures: Cryo-EELS and Cryo-4D-STEM

Scanning/transmission electron microscopy (S/TEM) in materials science has traditionally been accomplished at room temperature due to their solid state in this temperature range and relative insensitivity to radiolysis damage. Cooling to cryogenic temperatures tended to introduce instabilities such as vibration and drift and can lead to the buildup of carbon contamination or ice reducing contrast. The need to expand TEM experimental techniques into new fields such as quantum and battery materials led to new efforts to reduce these instabilities while achieving temperatures at or well below liquid nitrogen (77 K). Further, developments in detector and spectrometer technology brought new capabilities for high resolution electron energy loss spectroscopy (EELS) and scanning nanodiffraction (4D-STEM). These experimental modalities can require even tighter controls of drift, vibration, and exposure time. Here this presentation will discuss accomplishing difficult experiments at cryogenic temperatures in honor of the late Dr. Lena Kourkoutis who inspired and led many such experiments.

36 MATERIALS SCIENCE↗
DOE OSTI2024

A compact stem-loop DNA aptamer targets a uracil-binding pocket in the SARS-CoV-2 nucleocapsid RNA-binding domain

Abstract SARS-CoV-2 nucleocapsid (N) protein is a structural component of the virus with essential roles in the replication and packaging of the viral RNA genome. The N protein is also an important target of COVID-19 antigen tests and a promising vaccine candidate along with the spike protein. Here, we report a compact stem-loop DNA aptamer that binds tightly to the N-terminal RNA-binding domain of SARS-CoV-2 N protein. Crystallographic analysis shows that a hexanucleotide DNA motif (5′-TCGGAT-3′) of the aptamer fits into a positively charged concave surface of N-NTD and engages essential RNA-binding residues including Tyr109, which mediates a sequence-specific interaction in a uracil-binding pocket. Avid binding of the DNA aptamer allows isolation and sensitive detection of full-length N protein from crude cell lysates, demonstrating its selectivity and utility in biochemical applications. We further designed a chemically modified DNA aptamer and used it as a probe to examine the interaction of N-NTD with various RNA motifs, which revealed a strong preference for uridine-rich sequences. Our studies provide a high-affinity chemical probe for the SARS-CoV-2 N protein RNA-binding domain, which may be useful for diagnostic applications and investigating novel antiviral agents.

Biochemistry & Molecular Biology↗
DOE OSTI2024

PCAST: Letter to the President on Expanding STEM Talent in the Federal Workforce

The President’s Council of Advisors on Science and Technology (PCAST) is the sole body of advisors from outside the federal government charged with making science, technology, and innovation policy recommendations to the President and the White House. Established by Executive Order, it is an independent Federal Advisory Committee comprised of distinguished individuals from industry, academia, and non-profit organizations with a range of perspectives and expertise. On October 23, 2024, PCAST sent a letter to the President with recommendations to strengthen the science, technology, engineering, and mathematics (STEM) workforce in the federal government.

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2025

Undergraduate Women in STEM Internship Program

In collaboration with the Universities Research Association, Inc. (URA), establishment of the Undergraduate Women in STEM Internship pilot program assists Fermi Research Alliance, LLC (FRA) with honoring its commitment to increasing gender, racial and ethnic workforce diversity. This focused initiative is intended to invite, support and yield a qualified pipeline of alumnae underrepresented in FRA’s science and technology management and technical staff positions. Interns in this program spend 10-12 weeks at Fermilab working under the direct leadership, guidance and supervision of scientists, engineers, computing professionals, technicians and staff across all directorates performing hands-on research. In addition, the intern cohort meets with mentors and advisors to grow their professional networks, to take part in engaging and inclusive intellectual discussions, to directly benefit from workplace resources, and to participate in professional development and social engagement opportunities. The design of each research project and the supervision, mentorship and evaluation is conducted by a scientific, engineering, computing professional at Fermilab.

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2026

Flow Regimes for Gas Migration in Liquid Stemming Columns

Some underground engineering projects require the design of an effective stemming column to confine pressurized gases within boreholes. While solid materials such as grout plugs are commonly used, their exothermic curing can damage diagnostic tools, particularly under harsh in situ conditions involving elevated pressure and temperature.

42 ENGINEERING↗
DOE OSTI2025

STEM Professional Development Program for Nuclear Security Science and Technology Consortium

This oral presentation captures the technical and developmental aspect of the program in support of UNLV. The goal of this project is to develop a steady pipeline of STEM educated professionals in area of national and international nuclear security. The goal is to train university students at NNSS laboratories in studies motivated by global nuclear security topics ranging from nuclear emergency response and management to physics experiments for stockpile stewardship program.

96 KNOWLEDGE MANAGEMENT AND PRESERVATION↗
DOE OSTI2025

Magnetic Phase Diagram of 2D Magnet Fe 5– x GeTe 2 Revealed by Cryogenic Lorentz 4D-STEM

A two-dimensional van der Waals ferromagnet Fe 5–x GeTe 2 (F5GT) exhibits room-temperature magnetic transition and magnetic anisotropy. Studies have identified diverse magnetic states, including stripe domains, skyrmionic type-I and topologically trivial type-II bubbles, depending on the magnetic and thermal history. Yet, the underlying micromagnetic energetics driving these states remains unclear. Here, we establish the magnetic phase diagram of bulk F5GT using cryogenic Lorentz four-dimensional scanning transmission electron microscopy. We reveal that stripe domains spontaneously form upon zero-field cooling, while metastable magnetic bubbles are stabilized by external fields. Transitions from type-I to type-II bubbles are driven by an oblique external field. Micromagnetic simulations confirm that these transitions arise from the interplay of uniaxial anisotropy, dipolar interactions, and external fields, without requiring significant Dzyaloshinskii–Moriya Interaction (DMI). In conclusion, these findings clarify the micromagnetic origin of spin textures of F5GT and establish it as a tunable platform for nanoscale topological magnetism.

2D Magnets↗
DOE OSTI2024

Expression of a mammalian RNA demethylase increases flower number and floral stem branching in Arabidopsis thaliana

Abstract RNA methylation plays a central regulatory role in plant biology and is a relatively new target for plant improvement efforts. In nearly all cases, perturbation of the RNA methylation machinery results in deleterious phenotypes. However, a recent landmark paper reported that transcriptome‐wide use of the human RNA demethylase FTO substantially increased the yield of rice and potatoes. Here, we have performed the first independent replication of those results and demonstrated broader transferability of the trait, finding increased flower and fruit count in the model species Arabidopsis thaliana . We also performed RNA‐seq of our FTO‐transgenic plants, which we analyzed in conjunction with previously published datasets to detect several previously unrecognized patterns in the functional and structural classification of the upregulated and downregulated genes. From these, we present mechanistic hypotheses to explain these surprising results with the goal of spurring more widespread interest in this promising new approach to plant engineering.

59 BASIC BIOLOGICAL SCIENCES↗