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Results for “mechanical activation”

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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

TMEM2 binds to CSNK2A3 to inhibit HBV infection via activation of the JAK/STAT pathway

To investigate mechanisms that TMEM2 activation inhibits hepatitis B virus (HBV) infection in hepatocarcinoma (HCC) cells, co-immunoprecipitation (Co-IP) and mass spectrometry were used in screening interacting proteins for TMEM2. Levels of casein kinase 2 subunit α3 (CSNK2A3) in HCC cells were found to be inhibited or overexpressed using siRNAs and pcDNA3.1-CSNK2A3, respectively. Effect of CSNK2A3 expression on cell proliferation was analyzed using MTS, while its effect on HBV infection was measured using ddPCR and IHC. Western blotting and JAK inhibitor ruxolitinib were also used to determine whether TMEM2-regulated CSNK2A3 expression and HBV infection were affected by JAK-STAT signaling. Co-IP and mass spectrometry results showed that CSNK2A3 interacts with TMEM2. Moreover, overexpression of CSNK2A3 significantly inhibited cell proliferation, while inhibition of CSNK2A3 promoted proliferation of HCC cells. In addition, overexpression of CSNK2A3 was observed to significantly enhance HBV infection, while siRNA knockdown of CSNK2A3 inhibited HBV infection. Notably, effect of CSNK2A3 overexpression on HBV infection was suppressed by TMEM2 overexpression. Further mechanistic analyses have revealed that TMEM2 could antagonize the effects of CSNK2A3 on cell proliferation and HBV infection via JAK-STAT pathway activation. In conclusion, TMEM2 has been determined to bind to CSNK2A3 to inhibit HBV infection via activation of the JAK-STAT pathway.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2026

Identification of Solid-Electrolyte Interphase Species by Joint Characterization of Li-Ion Battery Chemistry by Mass Spectrometry and Electrochemical Reaction Networks

The formation and stability of the solid-electrolyte interphase (SEI) play central roles in determining the long-term performance and safety of modern electrochemical energy storage systems. Despite decades of research, the SEI’s heterogeneous, dynamic, and multiphase nature has defied comprehensive molecular-level characterization, creating a critical knowledge gap that limits rational battery design. In this work, we introduce a computational−experimental framework that integrates high-throughput quantum chemistry calculations, data-driven electrochemical reaction networks (eCRNs), stochastic algorithms, and laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry (LDI-FTICR-MS) to unravel SEI formation in carbonatebased electrolytes without imposing predefined mechanisms. We constructed the most comprehensive eCRN to date, spanning over 10,000 species and 209 million reactions. Through stochastic network analysis, we successfully recovered 27 species that were previously reported in the literature and predicted 28 novel SEI species nearly doubling our scientific knowledge in this area. Each new species was rigorously confirmed through advanced mass spectral analysis of its distinct molecular and isotopic signatures. We kinetically refined the formation pathways for a select set of both previously reported and novel SEI products, revealing kinetically feasible elementary reaction mechanisms with activation barriers below 1 eV. This computational−experimental approach deepens our molecular-level understanding of SEI chemistry by resolving which species form and through which decomposition mechanisms they emerge. Such knowledge provides the foundation necessary to connect electrolyte composition to the resulting SEI components, a critical step toward a more informed electrolyte development in next-generation lithium-based batteries.

25 ENERGY STORAGE↗
DOE OSTI2024

CO oxidation over a ligand coordinated single site Rh catalyst: identification of the active complex

Single atom catalysis has evolved as a promising strategy to enhance atom utilization efficiency, lower reaction temperatures, and control reaction pathways in heterogeneous catalytic reactions. An important challenge using supported single atom catalysts is the stability of metal single atoms during reactions. Here, we present an approach to stabilize single rhodium atoms on a titania support via a metal–ligand coordination strategy. We explore the reaction activity and mechanism of CO oxidation, as well as the stability under oxidative reaction conditions. Kinetic studies suggest that, with an excess of oxygen in the feed gas, oxygen activation is more facile on defective titania surfaces than on pristine titania surfaces. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis shows that on the pristine titania surface, the 1,10-phenanthroline-5,6-dione (PDO) coordinated Rh catalyst (Rh–PDO/TiO 2 ) catalyzes CO oxidation via the formation of carbonate-like species, which is similar to what occurs on Rh nanoparticle catalysts. However, on the defective titania surface, no carbonate species form for Rh–PDO/def-TiO 2 . The supported Rh–ligand catalysts are also shown to be very stable in such a reaction environment at elevated temperatures, potentially allowing for wide applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Short-term warming increased soil heterotrophic respiration due to enhanced active microbial community

Soil microbes, particularly active microbes, play a crucial role in conserving soil carbon under climate change, especially in forest ecosystems, constituting over 50% of global soil organic carbon. Nevertheless, the response mechanisms of active microbial community to climate warming and their subsequent impacts on soil heterotrophic respiration (Rh) remain insufficiently understood. To resolve this mechanistic uncertainty, we implemented a 3-year soil translocation experiment to investigate soil warming effects on active microbial community and Rh. We used 16S rRNA gene amplicon sequencing, Metatranscriptomics sequencing, coupled with correlation analyses to explore the linkages between warming-induced shifts in Rh and the active microbial community. Our results demonstrated that warming of soil induced a 55% enhancement in Rh. Concurrently, the Shannon index and Richness of active microbial community increased by 20% and 117%, respectively. Warming significantly altered active microbial community composition, inducing a compositional shift characterized by 0.5-to 2-fold increases in the abundances of Proteobacteria, Chloroflexi, and Actinobacteria. Our study also revealed 92–100% increases in the abundance of C-degradation functional genes encoding starch, cellulose, and lignin decomposition pathways within active microbial community under warming. Statistical analyses identified significant positive correlations between Rh and the abundance of Proteobacteria and Actinobacteria, as well as expression levels of functional genes associated with lignin and cellulose decomposition pathways. Furthermore, our results suggested that short-term warming increased Rh through altering diversity, species composition, and C degradation functional genes of active microbial community providing insights into the influence of microbial communities on soil C-climate feedbacks under climate warming.

Active microbial community↗
NASA NTRS1984

Thigmomorphogenesis: the relationship of mechanical perturbation to elicitor-like activity and ethylene production

An extracellular solution obtained from bean (Phaseolus vulgaris L. cv. Resistant Cherokee Wax) stems induced phytoalexin-like substance and ethylene production in a soybean [Glycine max (L.) Merr. cv. Wayne] cotyledon bioassay. The elicitor-like activity for phytoalexin formation and ethylene production was increased by mechanical perturbation of bean stems. Moreover, the application of extracted or known elicitors to bean plants mimicked the effect of mechanical perturbation (i.e., inhibition of stem elongation and enhancement of radial growth). The effects of extract when applied exogenously, on elicitor-like activity in the bioassay as well as stem thickening were decreased by aminoethoxyvinylglycine, an inhibitor of ethylene biosynthesis. These results suggest that elicitor-like substances which are formed in response to mechanical perturbation contribute to the thigmomorphogenesis.

Plants, Medicinal↗
NASA NTRS1994

The Influence of SiC on the Ablation Response of Advanced Refractory Composite Materials

In continuing our studies of advanced refractory composite materials we have recently completed an arc-jet test series of a diverse group of ceramics and ceramic matrix composites. The compositions range from continuous fiber reinforced ceramics to monoliths. Many of these materials contain SiC and one objective of this test series was to identify the influence of SiC oxidation mechanisms on material performance. Hence the arc heater was operated at two conditions; one in which the passive oxidation of SiC would be dominant and the other where the active oxidation of SiC would be dominant. It is shown here that the active oxidation mechanism of SiC does not dominate material performance when it is present at levels equal to or below 20 volume percent.

Bull, Jeffrey D.↗
DOE OSTI2021

Regulation of muscle hypertrophy: Involvement of the Akt-independent pathway and satellite cells in muscle hypertrophy

Highlights: • Involvement of Akt-independent mTOR activation in early mechanical overload. • Re-recognized critical roles of MuSCs in mechanical load-dependent muscle hypertrophy. • mTOR and MuSCs are involved in sarcopenia. Skeletal muscles are composed of multinuclear cells called myofibers and have unique abilities, one of which is plasticity. In response to the mechanical load induced by physical activity, skeletal muscle exerts several local adaptations, including an increase in myofiber size and myonuclear number, known as muscle hypertrophy. Protein synthesis and muscle satellite cells (MuSCs) are mainly responsible for these adaptations. However, the upstream signaling pathways that promote protein synthesis remain controversial. Further, the necessity of MuSCs in muscle hypertrophy is also a highly debated issue. In this review, we summarized the insulin-like growth factor 1 (IGF-1)/Akt-independent activation of mammalian target of rapamycin (mTOR) signaling in muscle hypertrophy and the involvement of mTOR signaling in age-related loss of skeletal muscle function and mass and in sarcopenia. The roles and behaviors of MuSCs, characteristics of new myonuclei in muscle hypertrophy, and their relevance to sarcopenia have also been updated in this review.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2023

The mechanics of plant morphogenesis

Understanding the mechanism by which patterned gene activity leads to mechanical deformation of cells and tissues to create complex forms is a major challenge for developmental biology. Plants offer advantages for addressing this problem because their cells do not migrate or rearrange during morphogenesis, which simplifies analysis. We synthesize results from experimental analysis and computational modeling to show how mechanical interactions between cellulose fibers translate through wall, cell, and tissue levels to generate complex plant tissue shapes. Genes can modify mechanical properties and stresses at each level, though the values and pattern of stresses differ from one level to the next. Here, the dynamic cellulose network provides elastic resistance to deformation while allowing growth through fiber sliding, which enables morphogenesis while maintaining mechanical strength.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1986

Yielding and deformation behavior of the single crystal nickel-base superalloy PWA 1480

Interrupted tensile tests were conducted to fixed plastic strain levels in 100 ordered single crystals of the nickel based superalloy PWA 1480. Testing was done in the range of 20 to 1093 C, at strain rate of 0.5 and 50%/min. The yield strength was constant from 20 to 760 C, above which the strength dropped rapidly and became a stong function of strain rate. The high temperature data were represented very well by an Arrhenius type equation, which resulted in three distinct temperature regimes. The deformation substructures were grouped in the same three regimes, indicating that there was a fundamental relationship between the deformation mechanisms and activation energies. Models of the yielding process were considered, and it was found that no currently available model was fully applicable to this alloy. It was also demonstrated that the initial deformation mechanism (during yielding) was frequently different from that which would be inferred by examining specimens which were tested to failure.

Milligan, W. W., Jr.↗
NASA NTRS1987

Yielding and deformation behavior of the single crystal superalloy PWA 1480

Interrupted tensile tests were conducted to fixed plastic strain levels in 100 ordered single crystals of the nickel based superalloy PWA 1480. Testing was done in the range of 20 to 1093 C, at strain rate of 0.5 and 50 percent/min. The yield strength was constant from 20 to 760 C, above which the strength dropped rapidly and became a strong function of strain rate. The high temperature data were represented very well by an Arrhenius type equation, which resulted in three distinct temperature regimes. The deformation substructures were grouped in the same three regimes, indicating that there was a fundamental relationship between the deformation mechanisms and activation energies. Models of the yielding process were considered, and it was found that no currently available model was fully applicable to this alloy. It was also demonstrated that the initial deformation mechanism (during yielding) was frequently different from that which would be inferred by examining specimens which were tested to failure.

Milligan, Walter W.↗
NASA NTRS1991

Tele-existence and/or cybernetic interface studies in Japan

Tele-existence aims at a natural and efficient remote control of robots by providing the operator with a real time sensation of presence. It is an advaced type of teleoperation system which enables a human operator at the controls to perform remote manipulation tasks dexterously with the feeling that he or she exists in one of the remote anthropomorphic robots in the remote environment, e.g., in a hostile environment such as those of nuclear radiation, high temperature, and deep space. In order to study the use of the tele-existence system in the artificially constructed environment, the visual tele-existence simulator has been designed, a pseudo-real-time binocular solid model robot simulator has been made, and its feasibility has been experimentally evaluated. An anthropomorphic robot mechanism with an arm having seven degrees of freedom has been designed and developed as a slave robot for feasibility experiments of teleoperation using the tele-existence method. An impedance controlled active display mechanism and a head mounted display have also been designed and developed as the display subsystem for the master. The robot's structural dimensions are set very close to those of humans.

Tachi, Susumu↗
DOE OSTI2022

Oxygen Evolution Reaction in Alkaline Environment: Material Challenges and Solutions

Abstract The oxygen evolution reaction (OER) generally exists in electrochemistry‐enabled applications that are coupled with cathodic reactions like hydrogen evolution, carbon dioxide reduction, ammonia synthesis, and electrocatalytic hydrogenation. The OER heavily impacts the overall energy efficiency of these devices because the sluggish OER kinetics result in a huge overpotential, thus, a large amount of efficient catalysts are needed. The benchmark iridium and ruthenium (Ir/Ru)‐based materials (mostly used in acid media) are, however, significantly limited by their scarcity. Non‐precious metal‐based catalysts (NPMCs) have emerged as the most promising alternatives; however, they tend to degrade quickly under the harsh operating conditions of typical OER devices. Another challenge is the unsatisfying performance of OER catalysts when integrated in real‐world devices. Herein, the OER active sites for three mainstream types of NPMCs including non‐precious transition metal oxides/(oxy)hydroxides, metal‐free carbon materials, and hybrid non‐precious metal and carbon composites are reviewed. In addition, possible degradation mechanisms for active sites and mitigation strategies are discussed in detail. This review also provides insights into the gaps between R&D of NPMCs for the OER and their applications in practical devices.

Xie, Xiaohong↗
NASA NTRS1974

On the nature of plasma arcs in solar active regions

A mechanism is proposed explaining the structures consisting of plasma arcs, as observed in X-ray photographs of solar active regions. It is suggested that the width of the arcs corresponds to the cut-off wavelength of a Rayleigh-Taylor instability which develops due to a difference in density between the plasma in the arcs and the plasma in the surrounding region. The transverse component of the magnetic field necessary to stabilize the instability at a wavelength corresponding to the width of the arcs is estimated to be of the order of 0.1 gauss.

Gajewski, R.↗
DOE OSTI2021

The electronic structure and deexcitation pathways of an isolated metalloporphyrin ion resolved by metal L-edge spectroscopy

The local electronic structure of the metal-active site and the deexcitation pathways of metalloporphyrins are crucial for numerous applications but difficult to access by commonly employed techniques. Here, we applied near-edge X-ray absorption mass spectrometry and quantum-mechanical restricted active space calculations to investigate the electronic structure of the metal-active site of the isolated cobalt(III) protoporphyrin IX cation (CoPPIX+) and its deexcitation pathways upon resonant absorption at the cobalt L-edge. The experiments were carried out in the gas phase, thus allowing for control over the chemical state and molecular environment of the metalloporphyrin. The obtained mass spectra reveal that resonant excitations of CoPPIX+ at the cobalt L3-edge lead predominantly to the formation of the intact radical dication and doubly charged fragments through losses of charged and neutral side chains from the macrocycle. The comparison between experiment and theory shows that CoPPIX + is in a 3 A 2g triplet ground state and that competing excitations to metal-centred non-bonding and antibonding σ* molecular orbitals lead to distinct deexcitation pathways.

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

Post-irradiation Examination of Eurofer-97 Steel Irradiated to 20 dpa at 200–400°C in HFIR under the EUROfusion (ORNL-KIT) Collaboration Program

The Oak Ridge National Laboratory/Karlsruhe Institute of Technology (ORNL/KIT) collaboration focuses on research involving irradiation experiments and post-irradiation examinations (PIE) of isotopically modified Eurofer-97 steels for fusion reactor applications. This collaboration capitalizes on ORNL’s expertise in radiation effects on materials and its capabilities in irradiation and PIE. The research aims to qualify Fe-9Cr-based Eurofer-97 steel under simulated fusion conditions, which include high doses and high transmutation rates. A unique isotopic modification technique is utilized in the research, wherein high-transmutation isotopes such as Fe-54 and Ni-58 are alloyed into the Eurofer steel to align with the expected helium production rates in fusion reactor conditions. This report presents the results of post-irradiation mechanical testing activities for the EUROFER-97/2 specimens after irradiation to ~20 dpa at various irradiation temperatures. The irradiation doses and temperatures for the ES capsules ranged from 18.4–20.4 dpa and 202–256°C, respectively. The mechanical property datasets, obtained through baseline testing and PIE of the tensile and fracture specimens, include microhardness data from 93 irradiated and non-irradiated tensile specimens and 28 irradiated bend bar specimens, uniaxial tensile property data from 45 irradiated and non-irradiated tensile specimens, and fracture toughness data from the bend bar specimens. Further data analyses provide statistical information on the microhardness values and tensile properties, as well as the reference ductile-brittle transition temperature (T 0 ) data.

36 MATERIALS SCIENCE↗
NASA NTRS1985

Wave phenomena in a high Reynolds number compressible boundary layer

Growth of unstable disturbances in a high Reynolds number compressible boundary layer is numerically simulated. Localized periodic surface heating and cooling as a means of active control of these disturbances is studied. It is shown that compressibility in itself stabilizes the flow but at a lower Mach number, significant nonlinear distortions are produced. Phase cancellation is shown to be an effective mechanism for active boundary layer control.

Bayliss, A.↗
DOE OSTI2023

Deciphering the evolution of flavin-dependent monooxygenase stereoselectivity using ancestral sequence reconstruction

Controlling the selectivity of a reaction is critical for target-oriented synthesis. Accessing complementary selectivity profiles enables divergent synthetic strategies, but is challenging to achieve in biocatalytic reactions given enzymes’ innate preferences of a single selectivity. Thus, it is critical to understand the structural features that control selectivity in biocatalytic reactions to achieve tunable selectivity. Here, we investigate the structural features that control the stereoselectivity in an oxidative dearomatization reaction that is key to making azaphilone natural products. Crystal structures of enantiocomplementary biocatalysts guided the development of multiple hypotheses centered on the structural features that control the stereochemical outcome of the reaction; however, in many cases, direct substitutions of active site residues in natural proteins led to inactive enzymes. Ancestral sequence reconstruction (ASR) and resurrection were employed as an alternative strategy to probe the impact of each residue on the stereochemical outcome of the dearomatization reaction. These studies suggest that two mechanisms are active in controlling the stereochemical outcome of the oxidative dearomatization reaction: one involving multiple active site residues in AzaH and the other dominated by a single Phe to Tyr switch in TropB and AfoD. Moreover, this study suggests that the flavin-dependent monooxygenases (FDMOs) adopt simple and flexible strategies to control stereoselectivity, which has led to stereocomplementary azaphilone natural products produced by fungi. This paradigm of combining ASR and resurrection with mutational and computational studies showcases sets of tools for understanding enzyme mechanisms and provides a solid foundation for future protein engineering efforts.

Science & Technology - Other Topics↗
NASA NTRS1996

Latency and activation in the control of TGF-beta

The biological activity of the transforming growth factor-beta's (TGF-beta)3 is tightly controlled by their persistence in the extracellular compartment as latent complexes. Each of the three mammalian isoform genes encodes a product that is cleaved intracellularly to form two polypeptides, each of which dimerizes. Mature TGF-beta, a 24 kD homodimer, is noncovalently associated with the 80 kD latency-associated peptide (LAP). LAP is a fundamental component of TGF-beta that is required for its efficient secretion, prevents it from binding to ubiquitous cell surface receptors, and maintains its availability in a large extracellular reservoir that is readily accessed by activation. This latent TGF-beta complex (LTGF-beta) is secreted by all cells and is abundant both in circulating forms and bound to the extracellular matrix. Activation describes the collective events leading to the release of TGF-beta. Despite the importance of TGF-beta regulation of growth and differentiation in physiological and malignant tissue processes, remarkably little is known about the mechanisms of activation in situ. Recent studies of irradiated mammary gland reveal certain features of TGF-beta 1 activation that may shed light on its regulation and potential roles in the normal and neoplastic mammary gland.

Non-NASA Center↗