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DOE OSTI2015

Structural changes and self-activated photoluminescence in reductively annealed Sr{sub 3}AlO{sub 4}F

White light emission of self-activated photoluminescence (PL) in Sr{sub 3}AlO{sub 4}F under 254 nm light is only observed after annealing in a reducing atmosphere of 5%H{sub 2}/95%Ar. High-resolution neutron powder diffraction reveals that the FSr{sub 6} octahedrons and AlO{sub 4} tetrahedrons in this anti-perovskite structure are closer packed in reduced than in air-annealed samples which show no PL. Careful analysis of temperature-dependent neutron powder diffraction data establishes smaller isotropic displacement parameters for Sr(1) and O in Sr{sub 3}AlO{sub 4}F annealed in a reducing atmosphere indicating that the denser packing of the polyhedral sub-units leads to a slightly deeper potential for the Sr(1) and O atoms. Both the air- and reductively-annealed samples have identical thermal expansion within the temperature range between 3 and 350 K. The Debye temperatures were calculated using the atomic displacement parameters and show no significant differences between the air and reductively annealed samples making the Debye temperature a bad proxy for self-activated PL. - Graphical abstract: Annealing Sr{sub 3}AlO{sub 4}F under reducing conditions results in an intense self-activated photoluminescence which is correlated with a denser packing of FSr{sub 6} and AlO{sub 4} polyhedra. - Highlights: • Sr{sub 3}AlO{sub 4}F made in air does not show self-activated photoluminescence. • Only when annealing Sr{sub 3}AlO{sub 4}F in a reducing gas is photoluminescence observed. • FSr{sub 6} and AlO{sub 4} polyhedra in reduced Sr{sub 3}AlO{sub 4}F structure are packed more efficient. • Smaller displacement parameters are found for under-bonded Sr(1) and O sites.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2016

Monitoring of CoS 2 reactions using high-temperature XRD coupled with gas chromatography (GC)

High-temperature X-ray diffraction with concurrent gas chromatography (GC) was used to study cobalt disulfide cathode pellets disassembled from thermal batteries. When CoS 2 cathode materials were analyzed in an air environment, oxidation of the K(Br, Cl) salt phase in the cathode led to the formation of K 2 SO 4 that subsequently reacted with the pyrite-type CoS 2 phase leading to cathode decomposition between ~260 and 450 °C. Here, independent thermal analysis experiments, i.e. simultaneous thermogravimetric analysis/differential scanning calorimetry/mass spectrometry (MS), augmented the diffraction results and support the overall picture of CoS 2 decomposition. Both gas analysis measurements (i.e. GC and MS) from the independent experiments confirmed the formation of SO 2 off-gas species during breakdown of the CoS 2 . In contrast, characterization of the same cathode material under inert conditions showed the presence of CoS 2 throughout the entire temperature range of analysis.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2019

Oxidative Cross-Esterification and Related Pathways of Co-Adsorbed Oxygen and Ethanol on Pd–Au

Ethanol is one of the most important industrial chemicals considering its wide range of uses. From ultrahigh vacuum (UHV) experiments, we were able to effectively produce acetaldehyde and ethyl acetate on a Pd–Au model catalyst. The presence of oxygen at the Pd–Au interface sites was found to be highly reactive for ethanol dehydrogenation, significantly increasing acetaldehyde production and promoting cross-esterification to produce ethyl acetate. Density functional theory calculations show that compared to the bare PdAu(111) surface, the presence of preadsorbed oxygen and the subsequently formed hydroxyl group leads to highly active and selective initial ethanol dehydrogenation at the O–H and α–C-H position, which was corroborated by isotope-labeling experiments. Specifically, using temperature-programmed desorption with the isotope CD 3 CH2OH, we identified C–C bond breakage through methane production. Furthermore, the simultaneous desorption of D2 with ethyl acetate from the oxidation of CD 3 CD 2 OD suggests that the abstraction of hydrogen from acetaldehyde and/or ethanol is a relevant step in ethyl acetate production, which is supported by our theoretical predictions. These results shed light on the mechanistic pathways of having oxygen and ethanol coadsorbed on Pd–Au surfaces, which has significant implications for industrial applications such as fuel cells where catalytic design plays a major role in the efficiency of power production.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2024

Identification of triacylglycerol remodeling mechanism to synthesize unusual fatty acid containing oils

Abstract Typical plant membranes and storage lipids are comprised of five common fatty acids yet over 450 unusual fatty acids accumulate in seed oils of various plant species. Plant oils are important human and animal nutrients, while some unusual fatty acids such as hydroxylated fatty acids (HFA) are used in the chemical industry (lubricants, paints, polymers, cosmetics, etc.). Most unusual fatty acids are extracted from non-agronomic crops leading to high production costs. Attempts to engineer HFA into crops are unsuccessful due to bottlenecks in the overlapping pathways of oil and membrane lipid synthesis where HFA are not compatible. Physaria fendleri naturally overcomes these bottlenecks through a triacylglycerol (TAG) remodeling mechanism where HFA are incorporated into TAG after initial synthesis. TAG remodeling involves a unique TAG lipase and two diacylglycerol acyltransferases (DGAT) that are selective for different stereochemical and acyl-containing species of diacylglycerol within a synthesis, partial degradation, and resynthesis cycle. The TAG lipase interacts with DGAT1, localizes to the endoplasmic reticulum (with the DGATs) and to puncta around the lipid droplet, likely forming a TAG remodeling metabolon near the lipid droplet-ER junction. Each characterized DGAT and TAG lipase can increase HFA accumulation in engineered seed oils.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2023

Ultrafast enhancement of electron-phonon coupling via dynamic quantum well states

Abstract The density of states at the Fermi surface controls many material properties by influencing the low-energy interactions of conductive electrons. Typically, external tuning knobs generate only small perturbations to the density of states in crystals, since their band structure depends strongly on the lattice potential. In contrast, quantum well states are contingent on a localized potential extrinsic to the crystal lattice and can be easily modified leading to changes in the density of states at the Fermi level. Here, we are able to control the quantum well potential on the surface of Bi 2 Se 3 with light, driving a density of states singularity below E F at ultrafast timescales, thereby triggering a reversible Lifshitz transition. We reveal a substantial ultrafast enhancement of the electron-phonon coupling with repercussions on the relaxation dynamics in the system. We argue that the relaxation dynamics are governed largely by the interplay of the dynamic density of states of the quantum wells with c -axis scattering from the $${A}_{{{{{{{{\rm{1g}}}}}}}}}^{2}$$ A 1g 2 optical phonon mode. These results demonstrate a powerful way to enhance electron-boson interaction on ultrafast timescales providing new avenues for controlling material properties and driving novel quantum phases of matter.

Ciocys, Samuel T.↗

DOE OSTI2016

Design and construction of a cascading pressure reactor prototype for solar-thermochemical hydrogen production

Recent work regarding the efficiency maximization for solar thermochemical fuel production in two step cycles has led to the design of a new type of reactor—the cascading pressure reactor—in which the thermal reduction step of the cycle is completed in multiple stages, at successively lower pressures. This approach enables lower thermal reduction pressures than in single-staged reactors, and decreases required pump work, leading to increased solar to fuel efficiencies. In this work we report on the design and construction of a prototype cascading pressure reactor and testing of some of the key components. We specifically focus on the technical challenges particular to the design, and their solutions.

14 SOLAR ENERGY↗

DOE OSTI2023

Finite-time correlations boost large voltage angle fluctuations in electric power grids

Abstract Decarbonization in the energy sector has been accompanied by an increased penetration of new renewable energy sources in electric power systems. Such sources differ from traditional productions in that, first, they induce larger, undispatchable fluctuations in power generation and second, they lack inertia. Recent measurements have indeed reported long, non-Gaussian tails in the distribution of local voltage frequency data. Large frequency deviations may induce grid instabilities, leading in worst-case scenarios to cascading failures and large-scale blackouts. In this article, we investigate how correlated noise disturbances, characterized by the cumulants of their distribution, propagate through meshed, high-voltage power grids. For a single source of fluctuations, we show that long noise correlation times boost non-Gaussian voltage angle fluctuations so that they propagate similarly to Gaussian fluctuations over the entire network. However, they vanish faster, over short distances if the noise fluctuates rapidly. We furthermore demonstrate that a Berry–Esseen theorem leads to the vanishing of non-Gaussianities as the number of uncorrelated noise sources increases. Our predictions are corroborated by numerical simulations on realistic models of power grids.

24 POWER TRANSMISSION AND DISTRIBUTION↗

DOE OSTI2022

Burden of bacterial bloodstream infections and recent advances for diagnosis

Abstract Bloodstream infections (BSIs) and subsequent organ dysfunction (sepsis and septic shock) are conditions that rank among the top reasons for human mortality and have a great impact on healthcare systems. Their treatment mainly relies on the administration of broad-spectrum antimicrobials since the standard blood culture-based diagnostic methods remain time-consuming for the pathogen's identification. Consequently, the routine use of these antibiotics may lead to downstream antimicrobial resistance and failure in treatment outcomes. Recently, significant advances have been made in improving several methodologies for the identification of pathogens directly in whole blood especially regarding specificity and time to detection. Nevertheless, for the widespread implementation of these novel methods in healthcare facilities, further improvements are still needed concerning the sensitivity and cost-effectiveness to allow a faster and more appropriate antimicrobial therapy. This review is focused on the problem of BSIs and sepsis addressing several aspects like their origin, challenges, and causative agents. Also, it highlights current and emerging diagnostics technologies, discussing their strengths and weaknesses.

Costa, Susana P.↗

DOE OSTI2021

Projecting the likely importance of weak-interaction-driven bulk viscosity in neutron star mergers

ABSTRACT In this work, we estimate how much bulk viscosity driven by Urca processes is likely to affect the gravitational wave signal of a neutron star coalescence. In the late inspiral, we show that bulk viscosity affects the binding energy at fourth post-Newtonian order. Even though this effect is enhanced by the square of the gravitational compactness, the coefficient of bulk viscosity is likely too small to lead to observable effects in the waveform during the late inspiral, when only considering the orbital motion itself. In the post-merger, however, the characteristic time-scales and spatial scales are different, potentially leading to the opposite conclusion. We post-process data from a state-of-the-art equal-mass binary neutron star merger simulation to estimate the effects of bulk viscosity (which was not included in the simulation itself). In that scenario, we find that bulk viscosity can reach high values in regions of the merger. We compute several estimates of how much it might directly affect the global dynamics of the considered merger scenario, and find that it could become significant. Even larger effects could arise in different merger scenarios or in simulations that include non-linear effects. This assessment is reinforced by a quantitative comparison with relativistic heavy-ion collisions where such effects have been explored extensively.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2024

Structural reforms and income distribution: new evidence for OECD countries

Abstract This article examines the impact of labour market and product market reforms on income inequality for 25 OECD countries between 1970 and 2020, using the local projections approach and an updated narrative-based dataset of the reform indicators. Our results suggest that both types of (endogenized) market-oriented reforms increase income inequality, but the effects are small. Consistent with this finding is that counter-reforms lead to less income inequality. Our results also indicate that the inequality-increasing effect of market-oriented reforms is mostly a result of more income going to the top of the income distribution.

Wiese, Rasmus↗

NASA NTRS2001

Aspect-Oriented Programming

Computer science has experienced an evolution in programming languages and systems from the crude assembly and machine codes of the earliest computers through concepts such as formula translation, procedural programming, structured programming, functional programming, logic programming, and programming with abstract data types. Each of these steps in programming technology has advanced our ability to achieve clear separation of concerns at the source code level. Currently, the dominant programming paradigm is object-oriented programming - the idea that one builds a software system by decomposing a problem into objects and then writing the code of those objects. Such objects abstract together behavior and data into a single conceptual and physical entity. Object-orientation is reflected in the entire spectrum of current software development methodologies and tools - we have OO methodologies, analysis and design tools, and OO programming languages. Writing complex applications such as graphical user interfaces, operating systems, and distributed applications while maintaining comprehensible source code has been made possible with OOP. Success at developing simpler systems leads to aspirations for greater complexity. Object orientation is a clever idea, but has certain limitations. We are now seeing that many requirements do not decompose neatly into behavior centered on a single locus. Object technology has difficulty localizing concerns invoking global constraints and pandemic behaviors, appropriately segregating concerns, and applying domain-specific knowledge. Post-object programming (POP) mechanisms that look to increase the expressiveness of the OO paradigm are a fertile arena for current research. Examples of POP technologies include domain-specific languages, generative programming, generic programming, constraint languages, reflection and metaprogramming, feature-oriented development, views/viewpoints, and asynchronous message brokering. (Czarneclu and Eisenecker s book includes a good survey of many of these technologies).

Elrad, Tzilla↗

DOE OSTI2022

Double Paddle‐Wheel Enhanced Sodium Ion Conduction in an Antiperovskite Solid Electrolyte

Abstract Antiperovskite structure compounds (X 3 AB, where X is an alkali cation and A and B are anions) have the potential for highly correlated motion between the cation and a cluster anion on the A or B site. This so‐called “paddle‐wheel” mechanism may be the basis for enhanced cation mobility in solid electrolytes. Through combined experiments and modeling, the first instance of a double paddle‐wheel mechanism, leading to fast sodium ion conduction in the antiperovskite Na 3− x O 1− x (NH 2 ) x (BH 4 ), is shown. As the concentration of amide (NH 2 − ) cluster anions is increased, large positive deviations in ionic conductivity above that predicted from a vacancy diffusion model are observed. Using electrochemical impedance spectroscopy, powder X‐ray diffraction, synchrotron X‐ray diffraction, neutron diffraction, ab initio molecular dynamics simulations, and NMR, the cluster anion rotational dynamics are characterized and it is found that cation mobility is influenced by the rotation of both NH 2 − and BH 4 − species, resulting in sodium ion conductivity a factor of 10 2 higher at x = 1 than expected for the vacancy mechanism alone. Generalization of this phenomenon to other compounds could accelerate fast ion conductor exploration and design.

25 ENERGY STORAGE↗

DOE OSTI2020

Isoreticular Linker Substitution in Conductive Metal–Organic Frameworks with Through‐Space Transport Pathways

Abstract The extension of reticular chemistry concepts to electrically conductive three‐dimensional metal–organic frameworks (MOFs) has been challenging, particularly for cases in which strong interactions between electroactive linkers create the charge transport pathways. Here, we report the successful replacement of tetrathiafulvalene (TTF) with a nickel glyoximate core in a family of isostructural conductive MOFs with Mn 2+ , Zn 2+ , and Cd 2+ . Different coordination environments of the framework metals lead to variations in the linker stacking geometries and optical properties. Single‐crystal conductivity data are consistent with charge transport along the linker stacking direction, with conductivity values only slightly lower than those reported for the analogous TTF materials. These results serve as a case study demonstrating how reticular chemistry design principles can be extended to conductive frameworks with significant intermolecular contacts.

Xie, Lilia S.↗

DOE OSTI2023

Investigating the Role of Vacancies on the Thermoelectric Properties of EuCuSb‐Eu 2 ZnSb 2 Alloys

Abstract AMX compounds with the ZrBeSi structure tolerate a vacancy concentration of up to 50 % on the M ‐site in the planar MX ‐layers. Here, we investigate the impact of vacancies on the thermal and electronic properties across the full EuCu 1− x Zn 0.5 x Sb solid solution. The transition from a fully‐occupied honeycomb layer (EuCuSb) to one with a quarter of the atoms missing (EuZn 0.5 Sb) leads to non‐linear bond expansion in the honeycomb layer, increasing atomic displacement parameters on the M and Sb‐sites, and significant lattice softening. This, combined with a rapid increase in point defect scattering, causes the lattice thermal conductivity to decrease from 3 to 0.5 W mK −1 at 300 K. The effect of vacancies on the electronic properties is more nuanced; we see a small increase in effective mass, large increase in band gap, and decrease in carrier concentration. Ultimately, the maximum zT increases from 0.09 to 0.7 as we go from EuCuSb to EuZn 0.5 Sb.

Chanakian, Sevan↗

DOE OSTI2023

Investigating the Role of Vacancies on the Thermoelectric Properties of EuCuSb‐Eu 2 ZnSb 2 Alloys

36 MATERIALS SCIENCE↗

DOE OSTI2024

Even-point multi-loop unitarity and its applications: exponentiation, anomalies and evanescence

Abstract We identify novel structure in newly computed multi-loop amplitudes and quantum actions for even-point effective field theories, including both the nonlinear sigma model (NLSM) and double-copy gauge theories such as Born-Infeld and its supersymmetric generalizations. We exploit special properties of all even-point theories towards establishing an efficient unitarity based amplitude construction. In doing so, we find evidence that the leading IR divergence of NLSM amplitudes exponentiates when the target space is$$ \mathbbm{CP} $$ CP 1 ≅ SU(2)/U(1). We then systematically compute the two-loop anomalous behavior of Born-Infeld, and find that the counterterms needed to restore U(1) invariant behavior at loop-level can be constructed via a symmetric-structure double-copy. We also demonstrate that the divergent part of the one-minus (−+++) two-loop anomaly vanishes upon introducing an evanescent operator. In addition to these purely photonic counterterms, we verify through explicit calculation that the anomalous matrix elements that violate U(1) duality invariance can be alternatively cancelled by summing over internal$$ \mathcal{N} $$ N = 4 DBIVA superfields. Finally we find that$$ \mathcal{N} $$ N = 4 Dirac-Born-Infeld-Volkov-Akulov (DBIVA) amplitudes admit double-copy construction through two-loop order by reproducing our unitarity based result with a double copy between color-dual$$ \mathcal{N} $$ N = 4 super-Yang-Mills and our two-loop NLSM amplitudes. This result supports the possibility of color-dual representations for NLSM beyond one-loop. We conclude with an overview of howD-dimensional four-photon counterterms can be constructed in generality with the symmetric-structure double-copy, and outline a convenient way of counting evanescent operators using Hilbert series as generating functions.

Physics↗

DOE OSTI2025

Optimization of Species-Selective Reversible Proteasome Inhibitors for the Treatment of Malaria

Abstract Malaria remains a critical global health challenge, with increasing resistance to frontline therapies necessitating novel drug targets. The proteasome has emerged as a promising target for antimalarial drug discovery. This study describes efforts to optimize a series of species-selective reversible inhibitors targeting the Plasmodium falciparum 20S proteasome. Starting from the carboxypiperidine scaffold identified through a high-throughput viability screen, we conducted iterative structure–activity relationship studies, leading to the development of highly potent and selective inhibitors with good oral bioavailability. Lead compounds demonstrated nanomolar potency against P. falciparum blood-stage parasites and selective inhibition of the parasite proteasome over the human counterpart. Cryo-EM structural studies confirmed binding at the β5 subunit, while in vivo pharmacokinetic studies identified promising candidates for further development. These findings support proteasome inhibition as a viable strategy for novel antimalarial drug development.

Gahalawat, Suraksha [UT Southwestern Medical Cente↗

DOE OSTI2021

Magneto-transport evidence for strong topological insulator phase in ZrTe5

Abstract The identification of a non-trivial band topology usually relies on directly probing the protected surface/edge states. But, it is difficult to achieve electronically in narrow-gap topological materials due to the small (meV) energy scales. Here, we demonstrate that band inversion, a crucial ingredient of the non-trivial band topology, can serve as an alternative, experimentally accessible indicator. We show that an inverted band can lead to a four-fold splitting of the non-zero Landau levels, contrasting the two-fold splitting (spin splitting only) in the normal band. We confirm our predictions in magneto-transport experiments on a narrow-gap strong topological insulator, zirconium pentatelluride (ZrTe 5 ), with the observation of additional splittings in the quantum oscillations and also an anomalous peak in the extreme quantum limit. Our work establishes an effective strategy for identifying the band inversion as well as the associated topological phases for future topological materials research.

36 MATERIALS SCIENCE↗