Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “P”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,207 records · Page 67
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Mechanisms and stability of Li dynamics in amorphous Li-Ti-P-S-based mixed ionic–electronic conductors: A machine learning molecular dynamics study

Mixed ionic–electronic conductors (MIECs) exhibit both high ionic and electronic conductivity to improve the battery performance. In this work, we investigate the mechanism and stability of transport channels in our recently developed MIEC material, amorphous Ti-doped lithium phosphorus sulfide (LPS), using molecular dynamics (MD) simulations with a 99% accurate machine-learning force field (MLFF) trained on ab initio MD data. The achieved MLFF helps efficient large-scale MD simulations on LPS with three Ti concentrations (10%, 20%, and 30%) and six temperatures (25°C to 225°C) to calculate ionic conductivity, activation energy, Li-ion transport mechanism, and configurational entropy. Results show that ionic conductivities and activation energies are consistent with our recent experimental values. Moreover, Li-ion transport occurs via free-volume diffusion facilitated by the formation of disordered Li-S polyhedra. The enhanced stability of transport channels at 10% and 20% Ti doping, compared to 0% and 30%, is observed by analyzing the vibrational and configurational entropy of these disordered Li-S polyhedra. Overall, this study highlights the utility of MLFF-based large-scale MD simulations in explaining the transport mechanism and the stability of Li-ion in Ti-doped LPS electrolyte with significant computational efficiency.

And configuration entropy↗
DOE OSTI2023

A mesoscale crystal plasticity model to predict room-temperature deformation and martensitic transformation of high-strength Quenching and Partitioning (Q&P) Steels and validation with synchrotron X-ray diffraction

Renowned for the superior mechanical properties and adeptness at cold-forming, Quenching and Partitioning (QP) steels have gained prominence as a promising candidate material in fabricating safety-critical components in various industries. The pertinent research on QP steels focus on the martensitic transformation of the Retained Austenite (RA) phase during cold-forming, a crucial mechanism that substantially influences the overall strength and ductility of QP steels. The austenite stability and transformation rate heavily rely on the local strain path and the initial microstructure, which is challenging for analytical prediction. In this paper, a mesoscale model is developed to capture the deformation and transformation kinetics of QP steels inside the microstructure. The model integrates the detailed explicit microstructure, acquired from characterization experiments, into a high-resolution finite element (FE) mesh. It distinctly model the deformation and interaction between the various phases and the effect on the transformation of RA. The model is validated with high energy X-ray diffraction (HEXRD) data, and shows excellent capability in predicting the asymmetric stress-strain behavior under uniaxial tension and compression, as well as the martensitic transformation rate. The model is used to investigate the strain and load partitioning effect of surrounding matrix to the transformation of RA, offering insights into the complex behavior of QP980 and facilitates further material development.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Antibacterial ADP-ribosyl cyclase toxins inhibit bacterial growth by rapidly depleting NAD(P) +

In metazoans, enzymes belonging to the bifunctional ADP-ribosyl cyclase/cyclic ADP-ribose (cADPr) hydrolase family regulate diverse cellular processes by synthesizing and hydrolyzing the intracellular second messenger cADPr, derived from the electron carrier NAD+. However, bacterial enzymes belonging to this family have not been characterized. Here, we identify a bacterial ADP-ribosyl cyclase that is associated with the type VII secretion system and functions as an antibacterial toxin. This enzyme, which we name Tac1, inhibits bacterial growth by rapidly hydrolyzing NAD+ and NADP+. We determine the X-ray crystal structure of Tac1 to a resolution of 1.4 Å, which reveals that this protein adopts the core catalytic fold of metazoan ADP-ribosyl cyclase enzymes such as CD38. Using a combination of biochemical and mutagenesis approaches, we identify catalytic residues within the active site of Tac1, which are responsible for the formation of a cADPr catalytic intermediate and subsequent hydrolysis of this intermediate into linear ADP-ribose. A bioinformatic analysis reveals that Tac1 is the founding member of a widespread family of bacterial ADP-ribosyl cyclase enzymes, many of which are associated with interbacterial conflict systems. We also identify enzymes in this family that are not associated with biological conflict systems and demonstrate that they produce cADPr as their major product rather than linear ADP-ribose, suggesting that these enzymes serve a biological function distinct from interbacterial antagonism. Together, these findings demonstrate that ADP-ribosyl cyclase/cADPr hydrolase enzymes function as toxins in diverse bacterial conflict systems and suggest that cADPr may play a previously overlooked role in bacterial physiology.

Colautti, Jake↗