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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 883 records · Page 49
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Disruption of histone acetylation homeostasis reveals multilayered chromatin regulation for transcriptional resiliency

Background Epigenetic modifications, nucleosome occupancy, and three-dimensional chromatin architecture collectively create a multi-layered, highly interactive regulatory system for controlling genomic functionality. Dysregulation of epigenetic processes leads to a plethora of abnormalities including disease states. Therapies focused on epigenetic modulation can alter gene expression to correct dysfunction, though the perpetuation of these states and the relationships among chromatin regulatory layers is not well understood. Results Here, we investigated global and local chromatin structural and functional responses after acute histone deacetylase inhibitor treatment (suberoylanilide hydroxamic acid) in lung cancer cells across time. Treatment substantially increased global histone acetylation resulting in a pervasive but not distinctive signature. The spread of acetylation did not significantly impact global chromatin accessibility, and nucleosome remodeling largely occurred at finer scales in functionally relevant genomic regions. Indeed, both H 3 K 4 trimethylation, a mark of active transcription, and gene expression changes were altered in a controlled locus-specific manner, suggesting aberrant acetylation indirectly leads to balanced and bidirectional gene expression profiles from tighter regulation of other chromatin features. HDACi treatment induced (13%) genomic rearrangement in chromatin compartmentalization and moderate weakening of topologically associating domains. Conclusions Continuous wavelet analysis of these features demonstrates that scale-dependent, locus-specific factors influence the relationship between chromatin architecture and functional output, suggesting that regulation of transcription and nucleosome remodeling is not entirely (nor linearly) dependent upon large scale compartment exchange. Structural and functional responses are most pronounced early after treatment with partial persistence of differential local chromatin features and expression later in time; this highlights the plasticity of chromatin regulation, which may have implications for the efficacy of epigenetic treatments. These results demonstrate the effectiveness of multi-layered regulation of transcription: in resilient systems, disruption of one chromatin feature does not distort the regulation of other features in supporting a transcriptional program that allows for survival.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Three-dimensional modeling of electric-field enhancement in multilayer dielectric gratings arising from inadvertent flaws

Pulse-compression gratings for high-power, short-pulse laser systems are exposed to high electric fields that are further enhanced locally due to their 2D nanostructured surface. This makes them vulnerable to laser-induced damage. The present work considers the effect on electric-field modulation caused by an array of commonly found inadvertent flaws in gratings including fabrication defects, contamination particles, and laser-induced–damage initiation. These defects affect the laser-damage performance characteristics of the grating. To understand the local field-enhancement distribution due these imperfections, 3D modeling of the electric-field distribution is performed with a sufficiently high resolution of 1/74 of the laser wavelength ( λ ) while considering a volume of ≈489 λ 3 . The results provide estimates for the ensuing electric-field intensification and projected reduction of the laser-damage thresholds, as well as the anticipated pattern of damage growth initiation.

47 OTHER INSTRUMENTATION↗
DOE OSTI2020

High Dynamic Voltage Range Studies of Piezoelectric Multilayer Actuators at Low Temperatures

Piezo actuators are used for resonance control in superconducting linacs. In high accelerating gradients linacs, such as those operated in a pulsed mode, the piezos require a large operating voltage. This is due to the Lorentz forced detuning which causes a large frequency shift and is compensated with an active piezo-tuning system. In this high dynamic voltage range the piezo is expected to warm up drastically due to it being in an insulated vacuum. This study characterizes the dielectric properties (capacitance, dielectric losses), the piezo stroke (from geophone), and thermal properties such as heating. Results obtained in the temperature range of 20K to 300K will be presented and discussed.

43 PARTICLE ACCELERATORS↗
DOE OSTI2019

NEUP Final Report: Multilayer Composite Fuel Cladding and Core Internals for LWR Performance Enhancement and Severe Accident Tolerance

Accident tolerance of LWR fuels and structures is of paramount importance, as highlighted by the accident at the Fukushima Daiichi nuclear power station. The ability of fuel cladding and core internals to resist runaway oxidation during a beyond design basis accident (BDBA), as well as to minimize corrosion during steady state operation and design basis accidents (DBAs), determines its degree of accident tolerance. A gap was identified in the accident tolerant fuel (ATF) concepts under consideration, as most consisted either of coatings which may not hold their integrity under prolonged operation, or different materials altogether which incur significant neutronic penalties. A compromise was therefore sought – by minimizing the amount of coating material while ensuring a strong microstructural bond, it was thought that a Zircaloy-steel layered composite would achieve the best of both approaches.The goal of this NEUP project was to develop a multi-metallic layered composite (MMLC) tailored to addressing accident tolerance of LWR fuel cladding and core internal structures using an innovative fabrication technology. The MMLC developed in this program is expected to enhance the accident tolerance of LWRs, thereby reducing the cost by recovering lost operating margins and/or increasing operating windows of peak cladding temperature, peak linear power, reducing steady-state corrosion, and enhancing severe accident tolerance.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2019

Silicon Carbide Multilayer Piping for 900°C Supercritical CO 2 Brayton Cycle: Chemical Compatibility in CO 2

The US Department of Energy's Office of Nuclear Energy is interested in developing supercritical carbon dioxide (sCO 2 ) power cycles that can achieve higher cycle efficiencies and lower costs than the traditional steam Rankine cycles. For the application of an sCO2 energy conversion system with a Very High Temperature Gas Reactor (VHTGR), turbine inlet temperatures over 850°C may be required. Consequently, it is necessary to demonstrate structural materials, including turbine inlet piping, that can be code certified at operating temperatures up to 900°C at sCO 2 pressures up to 42 MPa (6100 psi). There are very few metal alloys that retain their strength at these high temperatures, and that are chemically compatible with sCO 2 .

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2021

Exploring Fabrication of Ultra-low Absorption, Multilayer, Hafnium High Reflectors

Ultra-low absorption, high damage threshold coatings are critical for the advancement of the high power CW laser technologies, and in most cases, are a limiting factor for the output power. Since high power CW laser systems enable extremely high power irradiances, when the light is incident on an HR mirror, part of the energy is absorbed and converted into heat, which can have many detrimental side effects. The worst-case scenarios are optical distortion and laser-induced damage. These optics must operate reliably with irradiances of 100's kW/cm 2 to MW/cm 2 . The highest pulsed laser damage threshold high reflectors are consistently fabricated with hafnia material. However, hafnia is not the material of choice for high power CW laser systems because of very high absorption and scatter properties, factors of >100x higher than tantala-silica, due to its poly crystalline nature. This study focuses on CW laser use applications, where the coatings’ laser damage resistance is largely limited by the inherent absorption of the coating materials. The goal is to study the feasibility of utilizing a “composite” hafnium-silica and a “doped” hafnia-silica target materials to prohibit crystallization. The results from the study were extremely successful. Hafnia high reflectors coatings generated from this study exhibited one micron absorption values of approximately 1 ppm, which are the lowest reported values to date.

36 MATERIALS SCIENCE↗