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At least 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

FLAW STABILITY ANALYSIS OF SURFACE CRACKS IN DOE STANDARD CANISTERS UNDER OPERATION LOADS AND WELDING RESIDUAL STRESSES

There are over 3000 commercial spent nuclear fuel (SNF) storage canisters that are made of stainless steel and planned for multi-purpose functions of SNF handling: interim storage, transportation, and ultimate disposal at a future SNF disposition location. To date, many multi-purpose canisters (MPC) are located in coastal regions for long-term storage. The canisters are fabricated by welding, and post-welding heat treatment is not required for relieving welding residual stresses (WRS). As a result, these canisters may be susceptible to chloride induced stress corrosion cracking (CISCC) due to the chloride-bearing marine salts. The flaw stability analysis of MPC canisters was performed at SRNL (i.e., PVP2016-4935 and PVP2016-63887) for through-wall flaws and for surface flaws respectively, where WRS was considered, and the failure assessment diagram (FAD)-based fracture mechanics method codified by API 579-1/ASME FFS-1-2007 Edition was adopted.

DOE standard canister↗
DOE OSTI2021

Activation of the CaR-CSE/H2S pathway confers cardioprotection against ischemia-reperfusion injury

Ischemia-reperfusion (I/R) injury is a multifactorial process triggered when an organ is subjected to transiently reduced blood supply. The result is a cascade of pathological complications and organ damage due to the production of reactive oxygen species following reperfusion. The present study aims to evaluate the role of activated calcium-sensing receptor (CaR)-cystathionine γ-lyase (CSE)/hydrogen sulfide (H2S) pathway in I/R injury. Firstly, an I/R rat model with CSE knockout was constructed. Transthoracic echocardiography, TTC and HE staining were performed to determine the cardiac function of rats following I/R Injury, followed by TUNEL staining observation on apoptosis. Besides, with the attempt to better elucidate how CaR-CSE/H2S affects I/R, in-vitro culture of human coronary artery endothelial cells (HCAECs) was conducted with gadolinium chloride (GdCl3, a CaR agonist), H{sub 2}O{sub 2}, siRNA against CSE (siCSE), or W7 (a CaM inhibitor). The interaction between CSE and CaM was subsequently detected. Plasma oxidative stress indexes, H2S and CSE, and apoptosis-related proteins were all analyzed following cell apoptosis. We found that H2S elevation led to the improvement whereas CSE knockdown decreased cardiac function in rats with I/R injury. Moreover, oxidative stress injury in I/R rats with CSE knockout was aggravated, while the increased expression of H2S and CSE in the aortic tissues resulted in alleviated the oxidative stress injury. Moreover, increased H2S and CSE levels were found to inhibit cell apoptotic ability in the aortic tissues after I/R injury, thus attenuating oxidative stress injury, accompanied by inhibited expression of apoptosis-related proteins. In HCAECs following oxidative stress treatment, siCSE and CaM inhibitor were observed to reverse the protection of CaR agonist. Coimmunoprecipitation assay revealed the interaction between CSE and CaM. Taken together, all above-mentioned data provides evidence that activation of the CaR-CSE/H2S pathway may confer a potent protective effect in cardiac I/R injury.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2025

Enhanced MPM framework with multipatch isogeometric analysis for geotechnical applications

Achieving stable stress solutions at large strains using the Material Point Method (MPM) is challenging due to the accumulation of errors associated with geometry discretization, cell-crossing noise, and volumetric locking. Several simplified attempts exist in the literature to mitigate these errors, including higher-order frameworks. However, the stability of the MPM solution in such frameworks has been limited to simple geometries and the single-phase formulation (i.e., neglecting pore fluid). Although never explored, multipatch isogeometric analysis offers desirable qualities to simulate complex geometries while mitigating errors in the MPM. The degree of required high-order spatial integration has also never been investigated to infer a minimum limit for the stability of the stress solution in MPM. This paper presents a general-purpose numerical framework for simulating stable stresses in porous media, capturing both near incompressibility and multiphase interactions. First, the numerical framework is presented considering Non-Uniform Rational B-splines (NURBS) to perform isogeometric analysis (IGA) in MPM. Additionally, a volumetric strain smoothing algorithm is used to alleviate errors associated with volumetric locking. Second, the manifestation of cell-crossing errors is assessed via a series of problems with orders ranging from linear to cubic interpolation functions. Third, the use of NURBS is investigated and verified for problems with circular geometries. Finally, multipatch analysis is deployed to simulate plane strain and 3D penetration in soils, considering nearly incompressible elastoplastic (total stress) analysis and fully-coupled hydro-mechanical (effective stress) analysis. The stability of the solution is also analyzed for different constitutive models. From the results, it can be concluded that the framework using cubic interpolation functions with strain smoothing is the most convenient, presenting stable stress solutions for a broad range of multiphase geotechnical applications.

58 GEOSCIENCES↗
DOE OSTI2025

Transcript profiling of plastid ferrochelatase two mutants reveals that chloroplast singlet oxygen signals lead to global changes in RNA profiles and are mediated by Plant U-Box 4

Abstract Background In response to environmental stresses, chloroplasts generate reactive oxygen species, including singlet oxygen ( 1 O 2 ), an excited state of oxygen that regulates chloroplast-to-nucleus (retrograde) signaling, chloroplast turnover, and programmed cell death (PCD). Yet, the central signaling mechanisms and downstream responses remain poorly understood. TheArabidopsis thaliana plastid ferrochelatase two(fc2) mutant conditionally accumulates 1 O 2 , and Plant U-Box 4 (PUB4), a cytoplasmic E3 ubiquitin ligase, is involved in propagating 1 O 2 signals for chloroplast turnover and cellular degradation. Thus, thefc2andfc2 pub4mutants are useful genetic tools to elucidate these signaling pathways. Previous studies have focused on the role of 1 O 2 in promoting cellular degradation infc2mutants, but its impact on retrograde signaling from mature chloroplasts (the major site of 1 O 2 production) is poorly understood. Results To gain mechanistic insights into 1 O 2 signaling pathways, we compared transcriptomes of adult wt,fc2, andfc2 pub4plants. The accumulation of 1 O 2 infc2plants broadly repressed genes involved in chloroplast function and photosynthesis, while inducing genes and transcription factors involved in abiotic and biotic stress, the biosynthesis of jasmonic acid (JA) and salicylic acid (SA), microautophagy, and senescence. Elevated JA and SA levels were observed in 1 O 2 -stressedfc2plants.pub4reversed most of this 1 O 2 -induced gene expression and reduced the JA content infc2plants. Thepub4mutation also blocked JA-induced senescence pathways in the dark. However, fc2 pub4 plantsmaintained constitutively elevated levels of SA even in the absence of bulk 1 O 2 accumulation. Conclusions Together, this work demonstrates that infc2plants, 1 O 2 leads to a robust retrograde signal that may protect cells by downregulating photosynthesis and ROS production while simultaneously mounting a stress response involving SA and JA. The induction of microautophagy and senescence pathways indicate that 1 O 2 -induced cellular degradation is a genetic response to this stress, and the bulk of this transcriptional response is modulated by the PUB4 protein. However, the effect ofpub4on hormone synthesis and signaling is complex and indicates that an intricate interplay of SA and JA are involved in promoting stress responses and programmed cell death during photo-oxidative damage.

Plant Sciences↗
DOE OSTI2025

Revealing structure and shaping priorities in plant and fungal cell wall architecture via solid-state NMR

Plant and fungal cell walls are essential for growth, adaptation, and survival, with their intricate architectures dictating both resistance to stress and susceptibility to antifungal or biomass-degrading strategies. Understanding how these walls are built, remodeled, and function at the molecular level is therefore central to both clinical and biotechnological applications. Solid-state nuclear magnetic resonance (ssNMR) has emerged as a uniquely powerful tool for this purpose, as it reveals the structure, dynamics, and interactions of intact biopolymers without disrupting their native organization. Using this approach, recent studies have shown how structural polymorphism, polymer-polymer interactions, and species-specific remodeling govern mechanical integrity, drug resistance, and stress adaptation. Applications highlighted here include lignin-carbohydrate packing during plant stem maturation, fungal wall reorganization under treatment by wall-targeting antifungals such as echinocandin and nikkomycin, and the functional diversity of glucans, chitins, and mannans. Together, these insights uncover conserved principles of polymer assembly across kingdoms while informing new opportunities for antifungal development and biomass utilization. Ongoing advances in sensitivity and resolution are expected to broaden the reach of ssNMR and further accelerate its role in linking structural heterogeneity to biosynthetic complexity and biological function.

Antifungal↗
DOE OSTI2023

Exact solutions of burst pressure for thick-walled cylinders in power-law strain hardening steels

Exact solutions of burst pressure for defect-free, thick-walled cylindrical pressure vessels with capped ends are developed using the flow theory of plasticity in terms of the Tresca, von Mises, and Zhu-Leis yield criteria. The material is assumed to obey a power-law strain hardening rule, and the finite strain theory is adopted to describe large plastic deformation. On this basis, internal pressure is obtained as a complex polynomial function of effective strains on the inside and outside surfaces of the pressure vessel with the use of the Bernoulli numbers. At burst failure, the effective strains and stresses on the inside and outside surfaces are first determined, and then three flow solutions of burst pressure are obtained as a power series function of the diameter ratio (D o /D i ), strain hardening exponent (n), and ultimate tensile strength (UTS). The power series solution is confirmed to agree well with the exact flow solution of burst pressure in a closed-form for each yield criterion, and the results show that the von Mises flow solution is an upper bound prediction, the Tresca flow solution is a lower bound prediction, and the Zhu-Leis flow solution is an intermediate prediction of burst pressure. In conclusion, two sets of full-scale burst test data are then utilized to evaluate and validate the proposed flow solutions of burst pressure for both thin-walled pipes and thick-walled cylindrical pressure vessels.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Deformation Behaviors in Single BCC‐Phase Refractory Multi‐Principal Element Alloys under Dynamic Conditions

The mechanical behavior and microstructural evolution of a BCC-phase NbTaTiV refractory multi-principal element alloy (RMPEA) is studied over a wide range of strain rates (10 −3 to 10 3 s −1 ) and temperatures (room temperature to 850 °C). The mechanical property of present RMPEA shows less strain-rate dependence and strong resistance to softening at high temperatures. Under high strain-rate loading, the formation of thin type-I twins is observed, which could lead to an increase in strain-hardening rates. However, this hardening mechanism competes with adiabatic heating effects, resulting in the deterrence of strain-hardening behaviors. In contrast, substantial strain-hardening occurs at cryogenic temperatures due to the formation of twins, which act as stronger barriers to dislocation motion and interact with each other. To further understand the different strain-hardening behaviors, density functional theory (DFT) calculations predict relatively low stacking fault energies and high twinning stress for the NbTaTiV RMPEA.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Empirical Characterization and Modeling of Cohesive – to – Adhesive Shear Fracture Mode Transition due to Increased Adhesive Layer Thicknesses of Fiber Reinforced Composite Single – Lap Joints

Here, to ensure a strong adhesive bond, most standards and adhesive manufacturers specify a maximum adhesive gap of 1 mm when bonding fiber reinforced composite structures. In manufacturing large components, such as joining two halves of wind turbine blades, meeting this gap tolerance specification is impractical; gaps larger than 10 mm are common in large adhesively bonded composite structures using state-of-the-art manufacturing techniques. Currently, there is a lack of fundamental understanding of the failure mechanics of adhesive gaps larger than 3 mm. To create such understanding, glass fiber - acrylic thermoplastic composite panels bonded using different epoxy adhesives within single-lap joint samples with adhesive thicknesses of 0.1 mm, 0.3 mm, 1 mm, 3 mm, 5 mm, and 10 mm were sheared to failure. A transition from cohesive to adhesive failure was observed to occur about 1 mm to 3 mm joint thicknesses. Plotting the shear stress normalized by the ratio of the joint width to thickness as a function of the joint thickness normalized by the joint length is shown to result in the ability to fit simple empirically derived models of the cohesive-to-adhesive failure transition, regardless of the adhesive. Furthermore, using these normalized variables, all the observed cohesively failed specimens collapse to a single master curve, as do the adhesively failed specimens.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Climate-driven succession in marine microbiome biodiversity and biogeochemical function

Abstract Seasonal and El Niño-Southern Oscillation (ENSO) warming result in similar ocean changes as predicted with climate change. Climate-driven environmental cycles have strong impacts on microbiome diversity, but impacts on microbiome function are poorly understood. Here we quantify changes in microbial genomic diversity and functioning over 11 years covering seasonal and ENSO cycles at a coastal site in the southern California Current. We observe seasonal oscillations between large-genome lineages during cold, nutrient rich conditions in winter and spring versus small-genome lineages, including Prochlorococcus and Pelagibacter , in summer and fall. Parallel interannual changes separate communities depending on ENSO condition. Biodiversity shifts translate into clear oscillations in microbiome functional potential. Ocean warming induced an ecosystem with less iron but more macronutrient stress genes, depressed organic carbon degradation potential and biomass, and elevated carbon-to-nutrient biomass ratios. The consistent microbial response observed across time-scales points towards large climate-driven changes in marine ecosystems and biogeochemical cycles.

Larkin, Alyse A. (ORCID:0000000344660791)↗
DOE OSTI2022

Exploring the deformation behavior of nanotwinned Al–Zr alloy via in situ compression

Nanotwinned metals have demonstrated the capacity for concomitant high strength and ductility. However, metals with high stacking fault energies, such as aluminum (Al), have a low propensity for twin formation. Here, we show the fabrication of supersaturated solid-solution Al–Zr alloys with a high density of growth twins. Incoherent twin boundaries (ITBs) are strong barriers to dislocation motion, while mobile partial dislocations promote plasticity. These deformable nanotwinned Al–Zr alloys reach a flow stress of ∼1 GPa, as demonstrated using in situ micropillar compression tests. Density functional theory calculations uncover the role Zr solute plays in the formation and deformation of the nanotwinned microstructure. This study features a strategy for incorporating ITBs and 9R phase into Al alloys for simultaneous benefits to strength and deformability.

Richter, N. A. (ORCID:0000000332732276)↗
DOE OSTI2023

An assessment of spall failure modes in laser powder bed fusion fabricated stainless steel 316L with low-volume intentional porosity

Here, this paper reports on spall failure and damage modes in Laser Powder Bed Fusion fabricated Stainless Steel 316L (SS316L) with intentional levels of low-volume (1–5 vol. %) porosity and pore sizes of 200, 350, and 500 μm. The fabricated specimens were subjected to uniaxial-strain plate-impact loading at ~4.5 GPa, to initiate incipient spall failure. Analysis of velocimetry profiles measured using multi-probe photon-Doppler velocimetry coupled with post-mortem analysis of soft-recovered samples reveals local suppression of spall failure (termed as spall-dominated) as a function of porosity, as the failure mechanism transitions from spall-centered tensile stress dominated to a pore-centered microstructure-dominated damage mode involving void/crack nucleation and growth at pre-existing pores. The critical porosity level where the suppression of spall failure is first observed, as well as the spall location, is dependent on both the volume fraction and the size of the initially fabricated pores. In samples of 500 μm pore size, the suppression of spall failure is observed with as little as 1 vol. % porosity, while samples with smaller pores (200 μm) still experience spall-centered tensile stress dominated failure with higher levels (5 vol. %) of porosity. In the case of pore-centered microstructure-dominated failure, spall damage can occur but the spall plane is shifted toward the rear free surface, or more generally in areas further away from the region with pores. Highly heterogeneous deformation twinning, shear banding, grain rotation, and cracking are observed in the vicinity of pre-existing pores and expected spall failure sites.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Continuous polymer films deposited on top of porous substrates using plasma-enhanced atomic layer deposition and molecular layer deposition

Molecular layer deposition (MLD) is able to produce ultrathin polymer films with control over thickness, cross-linking, and chemical composition. With these capabilities, MLD should be useful in the fabrication of novel polymer membranes on porous supports. However, confining a continuous MLD film to the surface of porous substrates is difficult because of MLD film growth in the pores. The deposition in the pores lowers the conductance of the porous support. This paper presents a method to deposit continuous polymer films on top of porous substrates. In this method, Al2O3 plasma-enhanced atomic layer deposition (PE-ALD) using trimethylaluminum and oxygen plasma as the reactants was first used to cap the pores of the substrate. Subsequently, a polyamide MLD film was deposited on the Al2O3 PE-ALD capping layer using m-phenylenediamine and trimesoyl chloride as the reactants. The Al2O3 pore caps were then removed from the porous substrate by etching from the backside using a timed exposure to a dilute sodium hydroxide solution. This method was demonstrated using anodic aluminum oxide (AAO) and polyethersulfone (PES) porous substrates. Al2O3 PE-ALD film growth was limited to the top of the porous substrate, resulting in rapid surface recombination or high sticking coefficients for the reactive plasma species within the pores. Gas permeance measurements confirmed the pore capping of the AAO substrates. The reopening of the pores by dissolving the Al2O3 pore caps with a sodium hydroxide solution was monitored using gas permeance versus etch time. The removal of the Al2O3 pore caps from the PES substrates could also dissolve the Al2O3 layer underneath the MLD film. The loss of this Al2O3 layer led to the detachment of the MLD film from the PES substrate. However, the MLD film could be anchored to the PES support at fractures located in the Al2O3 film prior to the MLD. The Al2O3 film fracture allowed the MLD film to anchor firmly to the PES substrate by MLD in the pores of the PES porous substrate. The distance between the anchor points was a function of fracture density. This distance could be controlled by applying a tensile stress to the Al2O3 PE-ALD film to fracture the film through sample bending. This method produced firmly anchored polymer MLD films on top of the PES porous substrates.

Welch, Brian C. (ORCID:000000029747045X)↗
DOE OSTI2019

Directed aging, memory, and nature’s greed

Disordered materials are often out of equilibrium and evolve very slowly in a rugged and tortuous energy landscape. This slow evolution, referred to as aging, is deemed undesirable as it often leads to material degradation. However, we show that aging also encodes a memory of the stresses imposed during preparation. Because of inhomogeneous local stresses, the material itself decides how to evolve by modifying stressed regions differently from those under less stress. Because material evolution occurs in response to stresses, aging can be “directed” to produce sought-after responses and unusual functionalities that do not inherently exist. Aging obeys a natural “greedy algorithm” as, at each instant, the material simply follows the path of most rapid and accessible relaxation. Our experiments and simulations illustrate directed aging in examples in which the material’s elasticity transforms as desired because of an imposed deformation.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

The novel anti-CRISPR AcrIIA22 relieves DNA torsion in target plasmids and impairs SpyCas9 activity

To overcome CRISPR-Cas defense systems, many phages and mobile genetic elements (MGEs) encode CRISPR-Cas inhibitors called anti-CRISPRs (Acrs). Nearly all characterized Acrs directly bind Cas proteins to inactivate CRISPR immunity. Here, using functional metagenomic selection, we describe AcrIIA22, an unconventional Acr found in hypervariable genomic regions of clostridial bacteria and their prophages from human gut microbiomes. AcrIIA22 does not bind strongly to SpyCas9 but nonetheless potently inhibits its activity against plasmids. To gain insight into its mechanism, we obtained an X-ray crystal structure of AcrIIA22, which revealed homology to PC4-like nucleic acid–binding proteins. Based on mutational analyses and functional assays, we deduced that acrIIA22 encodes a DNA nickase that relieves torsional stress in supercoiled plasmids. This may render them less susceptible to SpyCas9, which uses free energy from negative supercoils to form stable R-loops. Modifying DNA topology may provide an additional route to CRISPR-Cas resistance in phages and MGEs.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Stepwise Dynamic Calibration of a Hydromechanical Simulation Using Time-Lapse Vertical Seismic Profile

This study aims to develop a methodology for calibrating subsurface stress changes through time-lapse Vertical Seismic Profiling (VSP) integration. The selected study site is the 13-10A injector well within the ongoing CO2-EOR operation of the Farnsworth Field Unit. The Time-lapse VSP dataset carries the combined effects of fluid substitution and mean effective stress changes, thereby providing a dataset amenable for the calibration of production and injection-induced stress changes. The concept is similar to calibrating a reservoir simulation model in that the process honor real field data to set up an inverse problem. The solution optimizes the independent and impactful geomechanical parameters that replicate the observed time-lapse seismic velocity changes. This stress calibration is enabled by 4D geomechanical modeling and the VSP Integration workflow. This calibration benefits from extensive geological, geophysical and geomechanical characterization through 3D seismic data, geophysical well logs, and core assessed as part of the 1D MEM conducted on the 13-10A subject well. These data are used to develop a site-specific rock physics model. The Biot Gassmann workflow combines rock physics and reservoir simulation outputs to determine the fluid substitution contribution to seismic velocity change. Additionally, modeled seismic velocity attributed to mean effective stress are determined from the geomechanical simulation outputs, and the stress-velocity relationship developed from the ultrasonic seismic velocity measurements on the extracted Morrow B core. A penalty function is then formed between the modeled seismic velocities and the observed time-lapse VSP dataset. Four independent and impactful geomechanical parameters have been determined. These are the bulk modulus and shear modulus for zero porosity and the shear and compressional seismic velocity to mean effective stress derivatives. The dataset of numerous coupled hydromechanical- geomechanical simulation realizations is built by combining variations of the four stated geomechanical parameters. A machine learning-assisted workflow comprised of an artificial neural network and a particle swarm optimizer are used to converge on the optimal geomechanical parameters. The successful execution of this workflow has affirmed the suitability of acoustic time-lapse measurements for 4D-VSP geomechanical stress calibration pending measurable stress sensitivities within the anticipated effective stress changes and the availability of suitable and reliable datasets for petroelastic modeling.

02 PETROLEUM↗
DOE OSTI2020

Experimental evolution reveals nitrate tolerance mechanisms in Desulfovibrio vulgaris

Elevated nitrate in the environment inhibits sulfate reduction by important microorganisms of sulfate-reducing bacteria (SRB). Several SRB may respire nitrate to survive under elevated nitrate, but how SRB that lack nitrate reductase survive to elevated nitrate remains elusive. To understand nitrate adaptation mechanisms, we evolved 12 populations of a model SRB (i.e., Desulfovibrio vulgaris Hildenborough, DvH) under elevated NaNO 3 for 1000 generations, analyzed growth and acquired mutations, and linked their genotypes with phenotypes. Nitrate-evolved (EN) populations significantly (p < 0.05) increased nitrate tolerance, and whole-genome resequencing identified 119 new mutations in 44 genes of 12 EN populations, among which six functional gene groups were discovered with high mutation frequencies at the population level. In this work, we observed a high frequency of nonsense or frameshift mutations in nitrosative stress response genes (NSR: DVU2543, DVU2547, and DVU2548), nitrogen regulatory protein C family genes (NRC: DVU2394-2396, DVU2402, and DVU2405), and nitrate cluster (DVU0246-0249 and DVU0251). Mutagenesis analysis confirmed that loss-of-functions of NRC and NSR increased nitrate tolerance. Also, functional gene groups involved in fatty acid synthesis, iron regulation, and two-component system (LytR/LytS) known to be responsive to multiple stresses, had a high frequency of missense mutations. Additionally, mutations in those gene groups could increase nitrate tolerance through regulating energy metabolism, barring entry of nitrate into cells, altering cell membrane characteristics, or conferring growth advantages at the stationary phase. This study advances our understanding of nitrate tolerance mechanisms and has important implications for linking genotypes with phenotypes in DvH.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

A High-Voltage High-Reliability Scalable Architecture for Electric Vehicle Power Electronics (Final Report)

This project developed and demonstrated new composite converter technologies that lead to high power density (> 20 kW/L) at power levels of 10s of kW, 100s of kW, or possibly higher, with fundamental advances in converter efficiency and Q that lead to substantial increases in mean time to failure (MTTF). These advantages were realized through development of new composite converter topologies that perform buck, boost, or other conversion functions and that are scalable to higher voltage and power levels through sharing of voltage and current stresses among multiple dissimilar partial-power converter modules. The project led to experimental demonstration of a125 kW multifunction electric vehicle power conversion system having in-creased dc bus voltage (950 V nominal, 1200 V peak) that interfaces a 200 V to 400 V battery pack, and that includes integrated level 2 wired charging and wireless charging functions. The project incorporated SiC MOSFET modules having switching frequencies in excess of 100 kHz, planar magnetics, a hierarchical control architecture that enables scaling to higher voltages and powers with additional converter modules, and a high-power density in excess of 20 kW/L. The research demonstrated how a more complex converter approach can increase mean-time-to-failure, even though the number of elements is increased. This is achieved through significant reduction of temperature rise through fundamentally superior converter circuit topologies. The research also demonstrated new high power planar magnetics that increase power density. The technology is appropriate to a variety of applications including EV power trains, EV charging, PV inverters, battery storage, and similar areas. These systems potentially can be manufactured in the U.S.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2025

Nitrogen limitation causes a seismic shift in redox state and phosphorylation of proteins implicated in carbon flux and lipidome remodeling in Rhodotorula toruloides

Background: Oleaginous yeast are prodigious producers of oleochemicals, offering alternative and secure sources for applications in foodstuff, skincare, biofuels, and bioplastics. Nitrogen starvation is the primary strategy used to induce oil accumulation in oleaginous yeast as part of a global stress response. While research has demonstrated that post-translational modifications (PTMs), including phosphorylation and protein cysteine thiol oxidation (redox PTMs), are involved in signaling pathways that regulate stress responses in metazoa and algae, their role in oleaginous yeast remain understudied and unexplored. Results: Towards linking the yeast oleaginous phenotype to protein function, we integrated lipidomics, redox proteomics, and phosphoproteomics to investigate Rhodotorula toruloides under nitrogen-rich and starved conditions over time. Our lipidomics results unearthed interactions involving sphingolipids and cardiolipins with ER stress and mitophagy. Our redox and phosphoproteomics data highlighted the roles of the AMPK, TOR, and calcium signaling pathways in regulation of lipogenesis, autophagy, and oxidative stress response. As a first, we also demonstrated that lipogenic enzymes including fatty acid synthase are modified as a consequence of shifts in cellular redox states due to nutrient availability. Conclusions: We conclude that lipid accumulation is largely a consequence of carbon rerouting and autophagy governed by changes to PTMs, and not increases in the abundance of enzymes involved in central carbon metabolism and fatty acid biosynthesis. Our systems-level approach sets the stage for acquiring multidimensional data sets for protein structural modeling and predicting the functional relevance of PTMs using Artificial Intelligence/Machine Learning (AI/ML). Coupled to those bioinformatics approaches, the putative PTM switches that we delineate will enable advanced metabolic engineering strategies to decouple lipid accumulation from nitrogen limitation.

Lipid Signalling↗