Search NASA⌕ Search

SEARCH · Search NASA

Results for “cell resistances”

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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Electrochemical CO 2 Utilization: Scalable System Operation for Formic Acid Production

In recent years, research into the electrochemical reduction of CO 2 has grown exponentially. Formic acid (FA) has become a particular value product from CO 2 due to its versatility [1], optimal atom economy [2], and thermodynamic favorable [3]. FA can be produced electrochemically via a direct two-electron transfer process involving CO 2 with a proton source, requiring less energy input and fewer reaction steps than the conventional Kemira process. However, product selectivity, electrode stability, and low faradic efficiency due to increased resistance under constant current, remain key issues for CO 2 reduction to FA [4]. University of Kentucky’s Center for Applied Energy Research (UK CAER) is currently investigating reactor designs to address the challenges associated with electrochemical CO 2 conversion to FA [5]. The current reactor system employs: (1) an organic-based charge carrier which shuttles charge directly to the catalyst to enable CO 2 reduction to FA; (2) novel electrode materials to mitigate large voltages and improve conductivity; and (3) a flow system which not only allows for the volumetric scale-up of both charge carrier and catalyst, but also decouples the charger carrier re-energized and FA production processes to protect the catalyst’s stability due to overpotential. Through careful adjustment of electrode, charge carrier, and electrolyte selection, cell resistances have decreased by over 15%, facilitating conduction necessary for effective CO 2 reduction to FA. The system uses a highly specific engineered catalyst, which has produced over 100 mM FA at a rate of over 10 mM FA/hour following the aforementioned electrode/charge carrier changes. System design considerations (flow rate, bulk volume) and modeling of the system will also be discussed.

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2026

All‐Solid‐State Batteries With Mechanically Stable Interfaces Consisting of a Zero‐Strain Cation‐Disordered Rocksalt Cathode

Interface stabilization is critical to the development of working all‐solid‐state batteries. Rigid cathode/solid electrolyte interfaces often disintegrate due to anisotropic volume change of cathode‐active materials, resulting in irreversible capacity loss. Herein, we demonstrate that Li 1.211 Mo 0.467 Cr 0.3 O 2 (LMCO), a pioneering cation‐disordered rocksalt oxide (DRX) cathode that has intrinsically small volume change upon lithium intercalation, can be integrated with a thiophosphate‐based solid electrolyte for all‐solid‐state batteries. Interface stability of the all‐solid LMCO cell was investigated by electrochemical impedance spectroscopy, X‐ray micro‐computed tomography, and electron microscopy. Since LMCO was initially synthesized as a layered phase exhibiting a large volume change, interface disintegration can be observable in the early cycles. As layered LMCO phase‐transformed into DRX LMCO in subsequent cycles, reintegration of the interfaces occurs within a pressurized cell as a result of its zero‐stain behavior. Consequently, the DRX LMCO cathode maintains interface integrity, and thus electrical wiring, over an extended number of cycles, leading to improved capacity retention with small internal cell resistance.

DRX↗
DOE OSTI2023

Two‐Membrane Dual Non‐Aqueous/Aqueous Electrolyte Flow Cell Operation for Electrochemical Conversion of CO 2 to Methyl Formate

Recently, tandem cathodic reactions have been demonstrated in non-aqueous solvents to couple CO 2 reduction to a secondary reaction to create novel species that are not produced in aqueous CO 2 electrolysis. One reaction that can be performed with high selectivity and durability is the electrochemical conversion of CO 2 to formic acid and in-situ esterification with methanol to produce methyl formate. However, the translation to a high-performance flow electrolyzer is far from trivial, as the non-aqueous catholyte leads to reactor challenges including flooding the gas diffusion electrode. Here, in this study, a two-membrane flow electrolyzer with both anion and cation exchange membranes was used with flowing methanol catholyte and aqueous anolyte. This design prevented methanol from flooding the cathode, which was a pervasive limiting issue for electrolyzers with a single membrane. Methyl formate production at 42.9 % faradaic efficiency was achieved with pure methanol in a flow electrolyzer with stable performance beyond 80 min. However, low-water-content catholyte compositions also led to increased cell resistance and lower operating current densities. Thus, with the present ionomer materials there is a tradeoff between methyl formate selectivity and current density depending on water concentration, highlighting a need for new ionomers tailored for desirable non-aqueous solvents such as methanol.

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

Development of Half-Sandwich Ru, Os, Rh, and Ir Complexes Bearing the Pyridine-2-ylmethanimine Bidentate Ligand Derived from 7-Chloroquinazolin-4(3H)-one with Enhanced Antiproliferative Activity

Kinesin spindle protein (KSP) inhibitors are one of the most promising anticancer agents developed in recent years. Herein, we report the synthesis of ispinesib-core pyridine derivative conjugates, which are potent KSP inhibitors, with half-sandwich complexes of ruthenium, osmium, rhodium, and iridium. Conjugation of 7-chloroquinazolin-4(3H)-one with the pyridine-2-ylmethylimine group and the organometallic moiety resulted in up to a 36-fold increased cytotoxicity with IC 50 values in the micromolar and nanomolar range also toward drug-resistant cells. All studied conjugates increased the percentage of cells in the G 2 /M phase, simultaneously decreasing the number of cells in the G 1 /G 0 phase, suggesting mitotic arrest. Additionally, ruthenium derivatives were able to generate reactive oxygen species (ROS); however, no significant influence of the organometallic moiety on KSP inhibition was observed, which suggests that conjugation of a KSP inhibitor with the organometallic moiety modulates its mechanism of action.

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

Electrochemical Conversion of CO 2 to Methyl Formate in a Flow Electrolyzer with Mixed Propylene Carbonate/Methanol Catholyte

Despite the promise of electrochemical carbon dioxide reduction as a technology for the production of clean fuels and decarbonization of the chemical industry, research has mostly focused on aqueous systems with a relatively limited set of products that have been achieved via electrosynthesis. Increasingly, CO 2 electroreduction in nonaqueous solvents is being pursued to develop new avenues for expanding the suite of products that can be made with high selectivity. CO 2 reduction in alcohols coupled with in situ esterification to produce esters is one such route that utilizes nonaqueous electrolyte. To be practical, such electrochemical syntheses need to be translated to a high-performance reactor such as a flow electrolyzer. However, many organic solvents, such as alcohols, wet and flood porous electrodes, thus impeding reactor performance. In this work, methanol was mixed with propylene carbonate as a catholyte for a gas-fed CO 2 flow electrolyzer that avoided cathode flooding. Simultaneously, a dual aqueous anolyte was used for water oxidation as a scalable and sustainable anodic half-reaction. The performance effect of methanol concentration, catholyte acidity, CO 2 flow rate, and dilute water in the catholyte were investigated. With 10 vol % methanol in 90 vol % propylene carbonate, 63% faradaic efficiency for methyl formate ester product was sustained without cathode flooding. However, improvements are still needed to lower the cell resistance and further increase the operating current density.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

A cocrystal structure of dengue capsid protein in complex of inhibitor

Dengue virus (DENV) was listed as a top 10 public health threat by the World Health Organization in 2019. No clinically approved anti-DENV drug is currently available. Here we report the high-resolution cocrystal structure (1.5 Å) of the DENV-2 capsid protein in complex with an inhibitor that potently suppresses DENV-2 but not other DENV serotypes. The inhibitor induces a “kissing” interaction between two capsid dimers. The inhibitor-bound capsid tetramers are assembled inside virions, resulting in defective uncoating of nucleocapsid when infecting new cells. Resistant DENV-2 emerges through one mutation that abolishes hydrogen bonds in the capsid structure, leading to a loss of compound binding. Structure-based analysis has defined the amino acids responsible for the inhibitor’s inefficacy against other DENV serotypes. The results have uncovered an antiviral mechanism through inhibitor-induced tetramerization of the viral capsid and provided essential structural and functional knowledge for rational design of panserotype DENV capsid inhibitors.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Assessing Electrolyte Fluorination Impact on Calendar Aging of Blended Silicon-Graphite Lithium-Ion Cells Using Potentiostatic Holds

Silicon-based lithium-ion batteries have started to meet cycle life metrics, but they exhibit poor calendar life. Here, electrolyte fluorination impact on calendar fade of blended silicon-graphite anodes is explored using a LiPF 6 in EC:EMC:FEC electrolyte vs LiBOB in EC:EMC electrolyte. We utilize a combined experimental-modeling approach applying potentiostatic voltage holds (V-hold) to evaluate electrolyte suitability for calendar life in a shortened testing timeframe (~2 months). Our theoretical framework deconvolutes the irreversible parasitic capacity losses (lithium lost to the solid electrolyte interphase) from the V-hold electrochemical data. Unfluorinated electrolyte (dominant LiBOB reduction) exhibits higher cell resistance as compared to fluorinated electrolyte (dominant FEC reduction). Both systems have similar irreversible capacities during the voltage hold duration with slower rate of parasitic capacity loss for the LiBOB system. Extrapolation of the parasitic losses to end of life capacity fade of 20% shows LiBOB electrolyte outperforming LiPF 6 electrolyte in calendar life. The results demonstrate the applicability of the V-hold protocol as a rapid material screening tool providing semi-quantitative calendar lifetime estimates.

25 ENERGY STORAGE↗
DOE OSTI2024

PpIX‐enabled fluorescence‐based detection and photodynamic priming of platinum‐resistant ovarian cancer cells under fluid shear stress

Over 75% percent of ovarian cancer patients are diagnosed with advanced-stage disease characterized by unresectable intraperitoneal dissemination and the presence of ascites, or excessive fluid build-up within the abdomen. Conventional treatments include cytoreductive surgery followed by multi-line platinum and taxane chemotherapy regimens. Despite an initial response to treatment, over 75% of patients with advanced-stage ovarian cancer will relapse and succumb to platinum-resistant disease. Recent evidence suggests that fluid shear stress (FSS), which results from the movement of fluid such as ascites, induces epithelial-to-mesenchymal transition and confers resistance to carboplatin in ovarian cancer cells. This study demonstrates, for the first time, that FSS-induced platinum resistance correlates with increased cellular protoporphyrin IX (PpIX), the penultimate downstream product of heme biosynthesis, the production of which can be enhanced using the clinically approved pro-drug aminolevulinic acid (ALA). These data suggest that, with further investigation, PpIX could serve as a fluorescence-based biomarker of FSS-induced platinum resistance. Additionally, this study investigates the efficacy of PpIX-enabled photodynamic therapy (PDT) and the secretion of extracellular vesicles under static and FSS conditions in Caov-3 and NIH:OVCAR-3 cells, two representative cell lines for high-grade serous ovarian carcinoma (HGSOC), the most lethal form of the disease. FSS induces resistance to ALA-PpIX-mediated PDT, along with a significant increase in the number of EVs. Finally, the ability of PpIX-mediated photodynamic priming (PDP) to enhance carboplatin efficacy under FSS conditions is quantified. These preliminary findings in monolayer cultures necessitate additional studies to determine the feasibility of PpIX as a fluorescence-based indicator, and mediator of PDP, to target chemoresistance in the context of FSS.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Influence of the Bulk Resistivity on Silicon Heterojunction Solar Cells and Module Reliability

Recent developments in industry on surface passivation open the possibility of using less doped substrates in silicon solar cells. In this report we investigate how the bulk resistivity affects the performance of silicon cells and the reliability of modules. Herein, n- and p-type silicon heterojunction cells with bulk resistivities between 3 and 15 000 Ωcm are studied. We measure the current–voltage characteristics of n-type cells across the resistivity range, and we find comparable responses to illumination intensities between 0.1 and 1 suns. The cells with bulk resistivities over 1000 Ωcm show breakdown voltages larger than -1000 V, almost two orders of magnitude higher than in typical commercial cells. Although modules have bypass-diodes to prevent cells from going into breakdown, higher breakdown voltages can improve the reliability of modules in case of bypass-diode failure and reduce the module cost by easing the number of bypass-diodes required. Finally, the cells have been submitted to light soaking. The float-zone p-type cells with bulk resistivities over 10 000 Ωcm are less sensitive to light-induced degradation than cells with bulk resistivities below 10 Ωcm. The former show to recover few hours after light soaking, while the latter recover only after dark annealing.

14 SOLAR ENERGY↗
DOE OSTI2023

Graphite resistive heated diamond anvil cell for simultaneous high-pressure and high-temperature diffraction experiments

High-pressure and high-temperature experiments using a resistively heated diamond anvil cell have the advantage of heating samples homogeneously with precise temperature control. Here, we present the design and performance of a graphite resistive heated diamond anvil cell (GRHDAC) setup for powder and single-crystal x-ray diffraction experiments developed at the Extreme Conditions Beamline (P02.2) at PETRA III, Hamburg, Germany. In the GRHDAC, temperatures up to 2000 K can be generated at high pressures by placing it in a water-cooled vacuum chamber. Temperature estimates from thermocouple measurements are within +/–35 K at the sample position up to 800 K and within +90 K between 800 and 1400 K when using a standard seat combination of cBN and WC. Isothermal compression at high temperatures can be achieved by employing a remote membrane control system. Importantly, the advantage of the GRHDAC is demonstrated through the study of geophysical processes in the Earth’s crust and upper mantle region.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

IRS4 promotes the progression of non-small cell lung cancer and confers resistance to EGFR-TKI through the activation of PI3K/Akt and Ras-MAPK pathways

IRS4 is a member of the insulin receptor substrate (IRS) protein family. It acts as a cytoplasmic adaptor protein, integrating and transmitting signals from receptor protein tyrosine kinases to the intracellular environment. IRS4 can induce mammary tumorigenesis and is usually overexpressed in non-small cell lung cancer (NSCLC). However, little is known about the role of IRS4 in the development and progression of lung cancer. In this study, we show that IRS4 knockout suppresses the proliferation, colony formation, migration, and invasion of A549 lung cancer cells, as well as tumor growth in a nude mouse xenograft model. In contrast, stable expression of IRS4 showed the opposite effects. As expected, IRS4 was found to activate the PI3K/Akt and Ras-MAPK pathways, and we also showed that IRS4 depletion significantly enhanced the sensitivity of EGFR tyrosine kinase inhibitor (EGFR-TKI)-resistant cells to gefitinib. Taken together, these results show that IRS4 promotes NSCLC progression and may represent a potential therapeutic target for EGFR-TKI-resistant NSCLC.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

Creating and Preserving Nanoparticles during Co-Sintering of Solid Oxide Electrodes and Its Impact on Electrocatalytic Activity

A novel processing method that creates and preserves ceramic nanoparticles in solid oxide electrodes during co-sintering at traditional sintering temperatures is introduced. Specifically, carbon templated samarium-doped ceria nanoparticles (nSDC) were successfully integrated with commercial lanthanum strontium cobalt ferrite (LSCF) and commercial SDC powders, producing LSCF-SDC-nSDC cathodes upon processing. The effect of nSDC concentration on cathode electrocatalytic activity was investigated at low operational temperatures, 600 °C–700 °C, with symmetrical cells. Low nSDC loadings, ≤5 wt% nSDC, significantly decreased cell polarization resistance whereas higher loadings increased it. The best electrochemical performance was achieved with 5 wt% nSDC, lowering the polarization resistance by 41% at 600 °C. Fuel cell tests demonstrate that adding 5 wt% nSDC increased the maximum fuel cell power density by 38%. Electrochemical impedance spectra showed substantial improvements in both fuel cell polarization resistance and ohmic resistance, indicating that nSDC increased the electrocatalytically active area of the cathode. This work demonstrates a simple, novel method for effectively increasing electrocatalytic activity of solid oxide electrodes at low operational temperatures.

Muhoza, Sixbert P. (ORCID:0000000299864241)↗
DOE OSTI2021

PGC1α regulates mitochondrial oxidative phosphorylation involved in cisplatin resistance in ovarian cancer cells via nucleo-mitochondrial transcriptional feedback

Mitochondria play an important role in effective cell energy production and cell survival under stress conditions, such as treatment with chemotherapeutic drugs. Mitochondrial biogenesis is increased in ovarian cancer tissues, which is accompanied by alteration of mitochondrial energy metabolism, structure, and dynamics. These factors are involved in tumorigenesis and apoptosis resistance, highlighting the role of mitochondria in resisting cisplatin toxicity. Cisplatin-resistant ovarian cancer cells are dependent on mitochondrial OXPHOS for energy supply, and intracellular PGC1α-mediated mitochondrial biogenesis levels are increased in this cell line, indicating the important role of mitochondrial oxidative phosphorylation in cisplatin resistance. As PGC1α is a key molecule for integrating and coordinating nuclear DNA and mitochondrial DNA transcriptional machinery, an investigation into the regulatory mechanism PGC1α in mitochondrial energy metabolism via transcription may provide new clues for solving chemotherapy resistance. In the present study, it was demonstrated that inhibiting the expression of PGC1α decreased nuclear and mitochondrial DNA transcription factor expression, leading to increased lactic acid production and decreased cellular oxygen consumption and mitochondrial oxidative phosphorylation. Furthermore, mitochondrial stress-induced ROS production, as a feedback signal from mitochondria to the cell nucleus, increased PGC1α expression in SKOV3/DDP cells, which was involved in mitochondrial oxidative phosphorylation regulation. Collectively, the present study provides evidence that PGC1α-mediated nuclear and mitochondrial transcription feedback regulates energy metabolism and is involved in ovarian cancer cells escaping apoptosis during cisplatin treatment.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

The AML microenvironment catalyzes a step-wise evolution to gilteritinib resistance

This study reports a stepwise evolution of gilteritinib resistance in acute myeloid leukemia (AML) relapse, and identifies therapeutic vulnerabilities that could be exploited. Our in vitro model demonstrates that extrinsic microenvironmental factors within the bone marrow nurture the growth of residual cells that underlie early gilteritinib resistance. These early resistant cells exhibit a dependency upon Aurora B (AURKB) and undergo dynamic metabolic adaptations that fostered their transition to late resistance. In line with clinical observations of gilteritinib resistance, late resistant cells displayed an expansion of NRAS mutant subclones and a unique metabolic profile that originated during early resistance. Pharmacological inhibition of AURKB resensitized early resistant cells to gilteritinib. Early resistant cells from AML patients were found to display exquisite sensitivitye to AURKB inhibition. Together, our findings support that eradication of early resistant AML cells may increase the efficacy and durability of gilteritinib.

AML, Proteomics↗
DOE OSTI2022

Local nm-Scale Imaging of Electrical Contact for Series Resistance Degradation of Silicon Solar Cells

We report on an electrical conduction mechanism for series resistance (Rs) degradation observed in a utility scale solar farm by nm-scale imaging of the local resistance at the Ag/Si interface of c-Si front metallization. Scanning spreading resistance microscopy imaging revealed that the number of point or small area electrical contacts decreased in a degraded cell compared to an unaffected cell, demonstrating the direct root cause of the Rs degradation. The degraded cell shows both a morphological and chemical difference in the screen-printed finger contact compared to the unaffected cell, which likely caused the degradation during the long-term field service. The reduction in electrical contact is likely caused by a structural change: The Ag particles in contact with the Si cell aggregate into bulk Ag, and a highly resistive ceramic oxide is formed in a "belt" shape at the Ag/Si interface. This resistive belt with a thickness of ~1 um blocks the current conduction from cell emitter to the Ag grid. Our results demonstrate an example of the multi-scale characterization approach for understanding degradation mechanisms in photovoltaics.

c-Si solar cell↗