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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 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Evidence for Modification of $b$ Quark Hadronization in High-Multiplicity $pp$ Collisions at $\sqrt{s}$ = 13 TeV

The production rate of $B^{0}_{s}$ mesons relative to $B^0$ mesons is measured by the LHCb experiment in $pp$ collisions at a center-of-mass energy $\sqrt{s}$ = 13 TeV over the forward rapidity interval 2 < $y$ < 4.5 as a function of the charged particle multiplicity measured in the event. Evidence at the 3.4$σ$ level is found for an increase of the ratio of $B^{0}_{s}$ to $B^0$ cross sections with multiplicity at transverse momenta below 6 GeV /$c$, with no significant multiplicity dependence at higher transverse momentum. Comparison with data from $e^+$ $e^–$ collisions implies that the density of the hadronic medium may affect the production rates of $B$ mesons. This is qualitatively consistent with the emergence of quark coalescence as an additional hadronization mechanism in high-multiplicity collisions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Modification of Quark-Gluon Distributions in Nuclei by Correlated Nucleon Pairs

We extend the QCD Parton Model analysis using a factorized nuclear structure model incorporating individual nucleons and pairs of correlated nucleons. Our analysis of high-energy data from lepton deep-inelastic scattering, Drell-Yan, and W and Z boson production simultaneously extracts the universal effective distribution of quarks and gluons inside correlated nucleon pairs, and their nucleus-specific fractions. Such successful extraction of these universal distributions marks a significant advance in our understanding of nuclear structure properties connecting nucleon- and parton-level quantities. Published by the American Physical Society 2024

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Erratum: Centrality-Dependent Modification of Jet-Production Rates in Deuteron-Gold Collisions at $\sqrt{𝑠_{𝑁⁢𝑁}}$ = 200 GeV [Phys. Rev. Lett. 116, 122301 (2016)]

We previously reported jet-production rates in 𝑝 + 𝑝 and 𝑑 + Au collisions at $\sqrt{𝑠_{𝑁⁢𝑁}}$ = 200 GeV recorded in 2008 with the PHENIX detector at the Relativistic Heavy Ion Collider. Subsequently, we found that electronic noise in the electromagnetic calorimeter was not completely removed by the tower-timing cuts used in the analysis. We have conducted an independent re-analysis of the data that eliminated noisy towers by removing them completely from the analysis. These cuts remove any contributions from instrumental noise, but reduce the overall acceptance for electromagnetic clusters by ≈16% and hence the overall statistical power of the data. Finally, this re-analysis found that instrumental noise in the electromagnetic calorimeter led to an artificial increase in the jet yield for both the 𝑝 + 𝑝 and 𝑑 + Au collisions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Measurement of In-Medium Jet Modification Using Direct Photon + Jet and 𝜋 0 + Jet Correlations in 𝑝 + 𝑝 and Central Au + Au Collisions at $\sqrt{s_{NN}}$ = 200 GeV

The STAR Collaboration presents measurements of the semi-inclusive distribution of charged-particle jets recoiling from energetic direct-photon (𝛾 dir ) and neutral-pion (𝜋 0 ) triggers in 𝑝 + 𝑝 and central Au + Au collisions at $\sqrt{s_{NN}}$ =2 00 GeV over a broad kinematic range, for jet resolution parameters 𝑅 = 0.2 and 0.5. Medium-induced jet yield suppression is observed to be larger for 𝑅 = 0.2 than for 0.5, reflecting the angular range of jet energy redistribution due to quenching. The predictions of model calculations incorporating jet quenching are not fully consistent with the observations. Furthermore, these results provide new insight into the physical origins of jet quenching.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Suggested Modifications for Bifacial Capacity Testing

Capacity tests such as those described in ASTM 2848 and IEC 61724-2 are widely used during the contracting and acceptance testing of photovoltaic systems. With the increasing deployment of bifacial photovoltaic modules, there is a need to develop a standardized approach to capacity test these systems. Although variability and bias error were inherently higher for the measured capacity of bifacial systems, they could be reduced to a level consistent with the monofacial reference system by appropriate incorporation of rear irradiance—either measured or modeled. Three field installations provided bifacial system capacity that was measured with a mean bias error and standard deviation within 1% over the 2–10-month observation period. Capacity test accuracy could be improved further by using the measured back-of-module temperature and the IEC 61724-2 test method for well curated systems.

41 EE - Solar Energy Technologies Office (EE-4S)↗
DOE OSTI2022

SNF1-related protein kinase 1 represses Arabidopsis growth through post-translational modification of E2Fa in response to energy stress

Cellular sugar starvation and/or energy deprivation serves as an important signaling cue for the live cells to trigger the necessary stress adaptation response. When exposed to cellular energy stress (ES) conditions, the plants reconfigure metabolic pathways and rebalance energy status while restricting vegetative organ growth. Despite the vital importance of this ES-induced growth restriction, the regulatory mechanism underlying the response remains largely elusive in plants.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

CALCIUM‐DEPENDENT PROTEIN KINASE32 regulates cellulose biosynthesis through post‐translational modification of cellulose synthase

Summary Cellulose is an essential component of plant cell walls and an economically important source of food, paper, textiles, and biofuel. Despite its economic and biological significance, the regulation of cellulose biosynthesis is poorly understood. Phosphorylation and dephosphorylation of cellulose synthases (CESAs) were shown to impact the direction and velocity of cellulose synthase complexes (CSCs). However, the protein kinases that phosphorylate CESAs are largely unknown. We conducted research in Arabidopsis thaliana to reveal protein kinases that phosphorylate CESAs. In this study, we used yeast two‐hybrid, protein biochemistry, genetics, and live‐cell imaging to reveal the role of calcium‐dependent protein kinase32 (CPK32) in the regulation of cellulose biosynthesis in A. thaliana . We identified CPK32 using CESA3 as a bait in a yeast two‐hybrid assay. We showed that CPK32 phosphorylates CESA3 while it interacts with both CESA1 and CESA3. Overexpressing functionally defective CPK32 variant and phospho‐dead mutation of CESA3 led to decreased motility of CSCs and reduced crystalline cellulose content in etiolated seedlings. Deregulation of CPKs impacted the stability of CSCs. We uncovered a new function of CPKs that regulates cellulose biosynthesis and a novel mechanism by which phosphorylation regulates the stability of CSCs.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Cell wall ester modifications and volatile emission signatures of plant response to abiotic stress

Abstract Growth suppression and defence signalling are simultaneous strategies that plants invoke to respond to abiotic stress. Here, we show that the drought stress response of poplar trees ( Populus trichocarpa ) is initiated by a suppression in cell wall derived methanol (MeOH) emissions and activation of acetic acid (AA) fermentation defences. Temperature sensitive emissions dominated by MeOH (AA/MeOH <30%) were observed from physiologically active leaves, branches, detached stems, leaf cell wall isolations and whole ecosystems. In contrast, drought treatment resulted in a suppression of MeOH emissions and strong enhancement in AA emissions together with volatiles acetaldehyde, ethanol, and acetone. These drought‐induced changes coincided with a reduction in stomatal conductance, photosynthesis, transpiration, and leaf water potential. The strong enhancement in AA/MeOH emission ratios during drought (400%–3500%) was associated with an increase in acetate content of whole leaf cell walls, which became significantly 13 C 2 ‐labelled following the delivery of 13 C 2 ‐acetate via the transpiration stream. The results are consistent with both enzymatic and nonenzymatic MeOH and AA production at high temperature in hydrated tissues associated with accelerated primary cell wall growth processes, which are downregulated during drought. While the metabolic source(s) require further investigation, the observations are consistent with drought‐induced activation of aerobic fermentation driving high rates of foliar AA emissions and enhancements in leaf cell wall O ‐acetylation. We suggest that atmospheric AA/MeOH emission ratios could be useful as a highly sensitive signal in studies investigating environmental and biological factors influencing growth‐defence trade‐offs in plants and ecosystems.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Improving Structural Integrity of Direct Laser-Deposited Ni – Co – Cr – Al – Y Superalloys by Alloy Modification

Abstract Ni- and Co-based M–Cr–Al–Y (M = Ni and/or Co), dual phase β and γ/γ′, β—Ni–Al, γ—Ni(Co, Cr), and γ′—Ni3–Al superalloys exhibit several beneficial high-temperature (>1000 °C) (2012 °F) strength and corrosion resistance properties. Our study investigates the feasibility of fabricating a commercially available Ni–Co–Cr–AlY alloy (tradename “Amdry 386”) using laser directed energy deposition (laser-DED). A significant challenge for laser fabrication of bulk Amdry 386 (A386) structures stems from the presence of relatively higher amounts of the β phase than γ/γ′ phases. While prior studies report laser fabrication of these materials in coating and cladding configurations, bulk structures have not been realized. To investigate these challenges, this study was developed to systematically evaluate the effects of modifying the A386 alloy by adding 10, 20, and 30% by weight of a Ni–20%Cr (Ni–Cr) alloy (mainly γ/γ′). Laser-DED-fabricated A386 coupons exhibited a metastable, rapidly solidified β-rich microstructure typical to laser processes. The A386 + Ni–Cr mixtures were processed using laser-DED, and small coupons from each composition were evaluated using SEM, XRD, and microhardness to characterize the as-processed microstructure. Thermodynamic modeling was performed to determine the phase evolution as a function of the alloy composition. The dominating phase switches from β to γ/γ’ between the A386 and A386 + 10% Ni–Cr mixtures, but the increase in structural integrity is not observed until the Ni–Cr additions reach a minimum of 20%. Our results show that the alloy chemistry can be successfully modified to improve the structural integrity of laser-processed structures.

Engineering↗
DOE OSTI2023

Systematic modification of functionality in disordered elastic networks through free energy surface tailoring

A combined machine learning–physics–based approach is explored for molecular and materials engineering. Specifically, collective variables, akin to those used in enhanced sampled simulations, are constructed using a machine learning model trained on data gathered from a single system. Through the constructed collective variables, it becomes possible to identify critical molecular interactions in the considered system, the modulation of which enables a systematic tailoring of the system’s free energy landscape. To explore the efficacy of the proposed approach, we use it to engineer allosteric regulation and uniaxial strain fluctuations in a complex disordered elastic network. Its successful application in these two cases provides insights regarding how functionality is governed in systems characterized by extensive connectivity and points to its potential for design of complex molecular systems.

42 ENGINEERING↗