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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Antineoplastic activity of Salmonella Typhimurium outer membrane nanovesicles

Highlights: • ST-OMVs is a promising antitumor monotherapy or as an adjuvant to chemotherapies. • ST-OMVs downregulated Ki-67 and upregulated CD49b immune-expression. • ST-OMVs downregulated angiogenesis by inhibiting VEGF gene expression. • ST-OMVs increased tumor cells apoptosis and autophagy (increased caspase-3and Beclin1). Nano-sized Gram-negative bacterial outer membrane vesicles possess unique structural and immunostimulatory effects that could be exploited to regress tumors by alerting the host immune system and reversing the immunosuppressive tumor microenvironment. The current study was conducted to investigate the antitumor activity of the outer membrane vesicles (ST-OMVs) of Salmonella Typhimurium ATCC 14028, in vitro in human colorectal carcinoma (HTC116), breast cancer (MCF-7), and hepatocellular carcinoma (HepG2) cell lines and in vivo in Ehrlich solid carcinoma-bearing mice model either as a mono-immunotherapy or as an adjuvant to a commonly used conventional chemotherapy. In addition, we investigated the safety of ST-OMVs. Adult Swiss albino female mice with transplanted Ehrlich solid carcinoma were treated with either ST-OMVs, paclitaxel or a combination of both. Tumor volume, growth inhibition rate, quantitative RT-PCR of Bax and VEGF genes expression, histopathology and immune-expression of caspase-3, Beclin-1, CD49b and Ki-67 were all analyzed. Our results showed that ST-OMVs significantly decreased tumor volume, significantly increased tumor growth inhibition rate, up-regulated the immunohistochemical expression of caspase-3, Beclin-1, and CD49b (enhanced recruitment of NK cells). Furthermore, ST-OMVs down-regulated the expression of Ki-67, increased Bax gene expression and decreased VEGF gene expression as detected by qRT-PCR analysis. Histologically, ST-OMVs promoted apoptosis, decreased tumor invasion and mitotic activities. Moreover, ST-OMVs showed a remarkable cytotoxic activity in various investigated in vitro cancer cell lines. Our findings demonstrate potential antitumor activity of ST-OMVs that might be used as a promising safe antitumor immunotherapy or an adjuvant to conventional chemotherapeutic drugs, resolving some of their problems.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2022

Supercurrent diode effect and finite-momentum superconductors

When both inversion and time-reversal symmetries are broken, the critical current of a superconductor can be nonreciprocal. In this work, we show that, in certain classes of two-dimensional superconductors with antisymmetric spin–orbit coupling, Cooper pairs acquire a finite momentum upon the application of an in-plane magnetic field, and, as a result, critical currents in the direction parallel and antiparallel to the Cooper pair momentum become unequal. This supercurrent diode effect is also manifested in the polarity dependence of in-plane critical fields induced by a supercurrent. These nonreciprocal effects may be found in polar SrTiO 3 film, few-layer MoTe 2 in the Td phase, and twisted bilayer graphene in which the valley degree of freedom plays a role analogous to spin.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Impact of Tiny Fermi Pockets with Extremely High Mobility on the Hall Anomaly in the Kagome Metal CsV 3 ⁢Sb 5

The kagome metal CsV 3 ⁢Sb 5 exhibits an unusual charge-density-wave (CDW) order, where the emergence of loop current order that breaks time-reversal symmetry (TRS) has been proposed. A key feature of this CDW phase is a nonmonotonic Hall effect at low fields, often attributed to TRS breaking. However, its origin remains unclear. Here, we conduct comprehensive magnetotransport measurements on CsV 3 ⁢Sb 5 and, through mobility spectrum analysis, identify the formation of tiny Fermi pockets with extremely high mobility below the CDW transition. Furthermore, electron irradiation experiments reveal that the nonmonotonic Hall effect is significantly suppressed in samples with reduced mobility, despite no substantial change in the electronic structure. In conclusion, these results indicate that the nonmonotonic Hall effect originates from these tiny Fermi pockets with high mobility carriers rather than anomalous Hall mechanisms, providing new insights into understanding the Hall anomaly in this kagome system.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Reversible ratchet effects in a narrow superconducting ring

We study the ratchet effect in a narrow pinning-free superconductive ring based on time-dependent GinzburgLandau (TDGL) equations. Voltage responses to external dc and ac currents at various magnetic fields are studied. Due to asymmetric barriers for flux penetration and flux exit in the ring-shaped superconductor, the critical current above which the flux-flow state is reached, as well as the critical current for the transition to the normal state, are different for the two directions of applied current. Furthermore, these effects cooperatively cause ratchet signal reversal at high magnetic fields, which has not been reported to date in a pinning-free system. The ratchet signal found here is larger than those induced by asymmetric pinning potentials. Our results also demonstrate the feasibility of using mesoscopic superconductors to employ a superconducting diode effect in versatile superconducting devices.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

New Modulation and Impact of Transformer Leakage Inductance on Current-Source Solid-State Transformer

This article presents a novel modulation scheme for device voltage stress mitigation and comprehensive analysis of the impact of transformer leakage inductance in a current-source solid-state transformer (SST). Different from dual active bridge (DAB) SST, the operation of the current-source SST is similar to that of a flyback converter. The device bridge on only one side of the transformer is active to store energy into or release energy from the magnetizing inductance which acts as a current-source dc link. Such flyback operation with reverse-blocking switches can lead to additional device voltage stress and incomplete zero-voltage switching (ZVS) on the current-source soft-switching solid-state transformer (S4T) under conventional modulation. A new modulation scheme is proposed to address this issue. Moreover, different from the DAB, the leakage inductance of the medium-frequency transformer (MFT) in the S4T is a parasitic element similar to that in a matrix SST and can cause additional device voltage stress. Though the resonant capacitors, originally added to achieve ZVS, can absorb and recycle the leakage energy in the S4T, these capacitors need to be increased with larger leakage inductances to limit the voltage stress. However, large resonant capacitors can result in more lost duty cycles and reduced efficiency. The impact of such leakage inductance on device voltage stress is analyzed comprehensively, which is critical to guide future research and design of the S4T. Experimental results from S4T prototypes for DC-DC, multiport AC-DC, and AC-AC conversion with 1:1 and 4:1 MFT comprehensively verify the proposed concepts. Lastly, a case study of a three-phase AC-AC S4T over a power range from 1 kVA to 100 kVA each module reveals that the MFT leakage inductance should be less than 1% of the magnetizing inductance for safe operation.

14 SOLAR ENERGY↗
DOE OSTI2026

Magnus force induced magnetic diode effect in skyrmion systems

We show that skyrmions can exhibit a “magnetic diode effect,” where there is a nonreciprocal response in the transport when the magnetic field is reversed. This effect can be achieved for skyrmions moving in channels with a sawtooth potential on one side and a reversed sawtooth potential on the other side. We consider the cases of both spin-transfer torque (STT) and spin–orbit torque (SOT). When the magnetic field is held fixed, the velocity response of the skyrmion is the same for current applied in either direction for both torques, so there is no current diode effect. When the magnetic field is reversed, under STT driving the velocity of the skyrmion reverses and its absolute value changes. Under SOT driving, the velocity remains in the same direction but drops to a much lower value, resulting in negative differential conductivity. For a fixed current, we find a nonreciprocal skyrmion velocity as a function of the applied field’s sign, in analogy to the velocity–current curves observed in the usual diode effect. The nonreciprocity is generated by the Magnus force, which causes skyrmions to interact preferentially with one side of the channel. Since the channel sides have opposite asymmetry, a positive magnetic field can cause the skyrmion to interact with the “hard” asymmetry side of the channel, while a negative magnetic field causes the skyrmion to interact with the “easy” asymmetry side. This geometry could be used to create new kinds of magnetic-field-induced diode effects that can be harnessed in new types of skyrmion-based devices.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Shift photovoltaic current and magnetically induced bulk photocurrent in piezoelectric sillenite crystals

Recently, it has been shown how shift and ballistic currents in piezoelectric sillenite crystals Bi 12 GeO 20 and Bi 12 SiO 20 can be separated experimentally under the assumption that the shift component of the circular current is small. However, it has been claimed that the shift and ballistic currents cannot be quantified by this method, due to the magnetophotovoltaic effect caused either by the change of the crystal's spatial symmetry in the magnetic field or by the breaking of time-reversal symmetry. Presently, we report observations of photovoltaic currents in Bi 12 SiO 20 , excited by linearly and circularly polarized light under weak external magnetic field, as well as measurements of the corresponding photo-Hall signals. Further, we demonstrate that the magnetophotovoltaic current constitutes a significant fraction of the measured current in the Hall direction for Bi 12 SiO 20 under specific experimental conditions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Electrophysiological Signatures of Visual Recognition Memory across All Layers of Mouse V1

In mouse primary visual cortex (V1), familiar stimuli evoke significantly altered responses when compared with novel stimuli. This stimulus-selective response plasticity (SRP) was described originally as an increase in the magnitude of visual evoked potentials (VEPs) elicited in layer 4 (L4) by familiar phase-reversing grating stimuli. SRP is dependent on NMDA receptors (NMDARs) and has been hypothesized to reflect potentiation of thalamocortical (TC) synapses in L4. However, recent evidence indicates that the synaptic modifications that manifest as SRP do not occur on L4 principal cells. To shed light on where and how SRP is induced and expressed in male and female mice, the present study had three related aims: (1) to confirm that NMDAR are required specifically in glutamatergic principal neurons of V1, (2) to investigate the consequences of deleting NMDAR specifically in L6, and (3) to use translaminar electrophysiological recordings to characterize SRP expression in different layers of V1. We find that knock-out (KO) of NMDAR in L6 principal neurons disrupts SRP. Current-source density (CSD) analysis of the VEP depth profile shows augmentation of short latency current sinks in layers 3, 4, and 6 in response to phase reversals of familiar stimuli. Multiunit recordings demonstrate that increased peak firing occurs in response to phase reversals of familiar stimuli across all layers, but that activity between phase reversals is suppressed. Together, these data reveal important aspects of the underlying phenomenology of SRP and generate new hypotheses for the expression of experience-dependent plasticity in V1. SIGNIFICANCE STATEMENT Repeated exposure to stimuli that portend neither reward nor punishment leads to behavioral habituation, enabling organisms to dedicate attention to novel or otherwise significant features of the environment. The neural basis of this process, which is so often dysregulated in neurologic and psychiatric disorders, remains poorly understood. Learning and memory of stimulus familiarity can be studied in mouse visual cortex by measuring electrophysiological responses to simple phase-reversing grating stimuli. The current study advances knowledge of this process by documenting changes in visual evoked potentials (VEPs), neuronal spiking activity, and oscillations in the local field potentials (LFPs) across all layers of mouse visual cortex. In addition, we identify a key contribution of a specific population of neurons in layer 6 (L6) of visual cortex.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

Investigations on the effect of current density on SiO/Si composite electrodes

An oxide layer on the surface of silicon particles is inevitable and is necessary for their application as anode materials for lithium ion batteries with high capacity and durability. However, a thick surficial oxide layer could significantly reduce the capacity of a Si anode. Here, Si nanoparticles with a thick surficial oxide layer of ~20 nm (Si@SiO x ) were fabricated through thermal oxidation and investigated electrochemically. The results revealed that very low current density is needed to activate Si@SiO x anodes during the first formation cycle. Once activated, the Si@SiO x anode can deliver reversible capacity as high as ~1000 mAh/g with low current density. Then, the Si@SiO x can be cycled at higher current densities of >700 mAh/g. Electrochemical impedance spectroscopy (EIS) shows that the lower current density results in lower charge-transfer resistance of the Si@SiO x anode, suggesting a higher degree of lithiation of the surficial oxide layer during low-current activation. EIS analysis also reveals that the lithiation of the surficial oxide is irreversible. We believe that the surface silicon oxide layer is lithiated and forms lithium silicate during the initial activation process. Lithium silicate has high conductivity and allows the lithiation/delithiation of Si core under the oxide layer during following charge and discharge.

25 ENERGY STORAGE↗
DOE OSTI2025

The Effect of Operational Temperature on the Performance and Durability of Solid Oxide Fuel Cells and Solid Oxide Electrolysis Cells

Solid oxide fuel cells (SOFC) and solid oxide electrolysis cells (SOEC) have received great interest due to their highly effective reversibility as power generation and H2 production system without releasing any greenhouse gases into environment. The LSCF electrode exhibits a higher structural and performance stability under both SOFC and SOEC operation due to its mixed ionic and electronic conductivity, and there is no immediate delamination taking place during the initial several hundred hours operation. However, the LSCF based air electrode still presents significant performance degradation (with the increased resistance) over the prolonged operation, such as over 1000 hours of operation under SOFC and SOEC. The influence factors for the cell’s performance and stability need to be optimized to improve the power generation for SOFC and H2 production for SOEC. The effects of operational temperature on the performance and durability for both SOFC and SOEC are electrochemical operation dependent. The performance and performance durability for the first 1500h were currently studied under optimized operational temperature for reversible SOFC/SOEC.

Fan, Yueying [NETL Site Support Contractor, Nation↗
DOE OSTI2024

Engineering and evaluation of FXa bypassing agents that restore hemostasis following Apixaban associated bleeding

Direct oral anticoagulants (DOACs) targeting activated factor Xa (FXa) are used to prevent or treat thromboembolic disorders. DOACs reversibly bind to FXa and inhibit its enzymatic activity. However, DOAC treatment carries the risk of anticoagulant-associated bleeding. Currently, only one specific agent, andexanet alfa, is approved to reverse the anticoagulant effects of FXa-targeting DOACs (FXaDOACs) and control life-threatening bleeding. However, because of its mechanism of action, andexanet alfa requires a cumbersome dosing schedule, and its use is associated with the risk of thrombosis. Here, we present the computational design, engineering, and evaluation of FXa-variants that exhibit anticoagulation reversal activity in the presence of FXaDOACs. Our designs demonstrate low DOAC binding affinity, retain FXa-enzymatic activity and reduce the DOAC-associated bleeding by restoring hemostasis in mice treated with apixaban. Importantly, the FXaDOACs reversal agents we designed, unlike andexanet alfa, do not inhibit TFPI, and consequently, may have a safer thrombogenic profile.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Asymmetric ether solvents for high-rate lithium metal batteries

Recent electrolyte solvent design based on weakening lithium-ion solvation have shown promise in enhancing cycling performance of Li-metal batteries. However, they often face slow redox kinetics and poor cycling reversibility at high rate. Here we report using asymmetric solvent molecules substantially accelerates Li redox kinetics. Asymmetric ethers (1-ethoxy-2-methoxyethane, 1-methoxy-2-propoxyethane) showed higher exchange current densities and enhanced high-rate Li 0 plating/stripping reversibility compared to symmetric ethers. Adjusting fluorination levels further improved oxidative stability and Li 0 reversibility. The asymmetric 1-(2,2,2-trifluoro)-ethoxy-2-methoxyethane, with 2 M lithium bis(fluorosulfonyl)imide, exhibited high exchange current density, oxidative stability, compact solid–electrolyte interphase (~10 nm). This electrolyte exhibited superior performance among state-of-the-art electrolytes, enabling over 220 cycles in high-rate Li (50 μm)||LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811, 4.9 mAh cm −2 ) cells and for the first time over 600 cycles in anode-free Cu | |Ni95 pouch cells (200 mAh) under electric vertical take-off and landing cycling protocols. Our findings on asymmetric molecular design strategy points to a new pathway towards achieving fast redox kinetics for high-power Li-metal batteries.

batteries↗
DOE OSTI2026

Current ramp-up studies for NSTX-U in support of the development of non-inductive current ramp-up scenarios in STs

The Spherical Tokamak (ST) is a low-aspect-ratio tokamak projected to enable simultaneous operation at high normalized toroidal beta and high bootstrap current fraction. However, a compact ST reactor cannot be built with a full-sized solenoid. The remaining current required for sustained operation must be ramped up non-inductively. Sustained 100% non-inductive current drive at the MA level has not yet been demonstrated on an ST. Non-inductive current ramp-up is therefore a more challenging objective that the NSTX-U research program aims to address. In support of this development, free-boundary TRANSP simulations have been used to develop a current ramp-up scenario in which a significant fraction of the current is driven non-inductively by a combination of neutral-beam and bootstrap current drive. The resulting discharge has properties favorable for non-inductive current drive, such as a low normalized internal plasma inductance of approximately 0.45, a minimum safety factor exceeding 2, and a slightly reversed-shear q-profile. In these discharges, the plasma current ramps to 900 kA within 250 ms in an L-mode configuration, with varying electron density and density profiles. These discharges should be suitable for next-step NSTX-U experiments aimed at generating a robust L-mode fiducial scenario with low central solenoid flux consumption, which could be progressively improved as new NSTX-U experimental discharges are developed.

Raman, Roger [Univ. of Washington, Seattle, WA (Un↗
DOE OSTI2022

Atomically Dispersed Pentacoordinated‐Zirconium Catalyst with Axial Oxygen Ligand for Oxygen Reduction Reaction

Single-atom catalysts (SACs), as promising alternatives to Pt-based catalysts, suffer from the limited choice of center metals and low single-atom loading. Here, we report a pentacoordinated Zr-based SAC with nontrivial axial O ligands (denoted O-Zr-N-C) for oxygen reduction reaction (ORR). The O ligand downshifts the d-band center of Zr and confers Zr sites with stable local structure and proper adsorption capability for intermediates. Consequently, the ORR performance of O-Zr-N-C prominently surpasses that of commercial Pt/C, achieving a half-wave potential of 0.91 V vs. reversible hydrogen electrode and outstanding durability (92% current retention after 130-hour operation). Moreover, the Zr site shows good resistance towards aggregation, enabling the synthesis of Zr-based SAC with high loading (9.1 wt%). With the high-loading catalyst, the zinc-air battery (ZAB) delivers a record-high power density of 324 mW cm -2 among those of SAC-based ZABs.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Coal-derived graphene foam and micron-sized silicon composite anodes for lithium-ion batteries

Silicon-based materials demonstrate significant potential as lithium-ion batteries (LIBs) anode, but their expansion and degradation present engineering design challenges for commercial application. In this study, a porous three-dimensional (3D) graphene and micron-sized silicon composite anode (Si@G foam) was synthesized using humic acid (HA) derived from coal as a graphene precursor. In-situ formation of graphene structure through reducing HA was confirmed by Raman spectra. The reduced HA (rHA) shows similar electrical conductivity compared to the commercial conductive carbon. SEM images depict a 3D skeleton of coal-derived graphene, with silicon particles distributed on the 3D graphene foam's internal surface. The Si@G composite-anode displays a good reversible capacity of ~656 mAh/g at a current density of 50 mA/g, as well as a high-rate capability of ~433 mAh/g at a current density of 800 mA/g, and outstanding cycling stability –89.8% capacity retention after 300 cycles, which is significantly higher than that of other foam structures. During lithiation and de-lithiation, the graphene foam serves as a matrix of electrical conductors and a volume expansion support for silicon. This 3D graphene network will be beneficial for developing advanced silicon-based anodes for high-performance LIBs.

25 ENERGY STORAGE↗
DOE OSTI2025

Electrochemical Phase Engineering of γ′-V 2 O 5 Thin Films for Sodium-Ion Storage Electrodes

V 2 O 5 is a promising sodium-ion cathode material due to its high theoretical capacity (147 mAh/g) and working voltage (3.3 V vs Na/Na + ). Among its various crystal phases, γ′-V 2 O 5 has a large interlayer spacing, ensuring the reversible insertion–extraction of sodium ions. However, current synthesis methods for γ′-V2O5 require high temperatures (>600 °C) and toxic chemicals (NO 2 BF 4 ), which make the preparation demanding. Herein, we put forward an electrochemical phase engineering method combining thermal annealing and electrochemistry to easily prepare thin-film γ′-V 2 O 5 . Electrochemical characterization shows near-ideal performance as a thin-film cathode material for sodium-ion batteries. It shows a measured initial capacity of 152 mAh/g, a high working voltage (3.3 V vs Na + /Na), and an exceptional Coulombic efficiency of 98%, significantly surpassing previously reported values (∼50% CE). Cyclic voltammogram and galvanostatic capacity curves confirm the sodium insertion–deinsertion, which remains stable at 2 C. The γ′-V 2 O 5 thin film has electrochemical performance similar to γ′-V 2 O 5 powder, indicating another workable morphology of γ′-V 2 O 5 for sodium-ion batteries.

batteries↗
DOE OSTI2024

Synthesizing Highly Crystalline Graphite Powder from Bulk Polyethylene Waste for Lithium-Ion Battery Anodes

Upcycling plastic waste into graphite can potentially be used, in conjunction with other methods, to manage existing waste materials and diversify graphite supply chains. However, synthesizing large quantities of crystalline graphite powder from plastic waste, particularly polyethylene (PE), remains a challenge because PE decomposes into light gases during thermal processing and simple methods do not exist at any appreciable size scale to address this challenge. In this work, a method is developed for air processing bulk forms of PE waste to create stable carbon char that does not readily decompose during high-temperature processing. This method employs solid additives in the form of salts, which are combined with the PE melt during air processing to increase the effective surface area of the melt and improve the oxygen-driven chemistry that stabilizes PE for high-temperature processing. After removal of the solid salt additives from the PE-derived char, it is converted into a highly crystalline bulk graphite powder using an Fe-based catalytic process. The PE-derived graphite anode in a lithium-ion coin cell showed a specific capacity of 345 mAh/g at 0.05C with an initial Coulombic efficiency of 87% and reversible capacity retention of ~100% at different current rates. It also showed a specific capacity of up to 313 mAh/g at 0.5 discharge/charge cycles per hour (0.5C) and Coulombic efficiency of 99.9% after 250 cycles, indicating excellent electrochemical performance as an anode material for lithium-ion batteries. This method illustrates that there are opportunities for upcycling large quantities of PE waste to produce graphite powders suitable for use in LIBs.

25 ENERGY STORAGE↗