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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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We developed models to predict the photoactivity of organic molecules for photocatalytic hydrogen evolution by integrating experiment, computation, and machine learning. This marks a step toward the data-driven discovery of molecular photocatalysts.
This protein–iron oxide hybrid biomaterial aims to integrate the drug encapsulating potential of a coiled-coil protein with peptide-driven iron oxide biomineralization to serve as drug-carrying, MRI-detectable mesofiber.
Metal–organic-based electrode materials are increasingly appealing because both metal and organic linker are capable of undergoing redox processes, thus offering a high specific capacity. High porosity which can be achieved by the rational design of these materials is generally perceived as one of the major criteria for high rate performance. However, while Li-ion transport may be possible, oftentimes the counteranions (e.g., PF 6 - ) and solvent molecules are co-inserted into the porous host lattice, potentially hindering Li-ion diffusion pathways. Here, in this study, we propose the concept of close-packed metal–organic cathode stabilized by multiple supramolecular interactions as a viable solution for exceptional electrochemical performance. This is illustrated in a modularly designed redox-active [CuL(Py) 2 ] n (LH 4 = 1,4-dicyano-2,3,5,6-tetrahydroxybenzene, Py = pyridine). The mechanistic studies and DFT calculations confirm that the supramolecular interactions between its close-packed chains are the key to the flexible host lattice which only allows desolvated Li + to intercalate, while these weak bonds also stabilize the inserted Li in the preferred hopping sites, creating optimal diffusion paths. The performance observed in this work is found to be among the best ever reported for metal–organic cathodes with a capacity as high as 255 mA h g -1 at 65 mA g -1 (0.25C) and a reversible capacity of 59 mA h g -1 at ~26 A g -1 (100C) corresponding to 81% retention after 1000 cycles. These findings reveal a potential new strategy towards metal–organic-based electrodes with high performance and enhanced cycling stability.
Covalent inhibitors of the papain-like protease (PLpro) from SARS-CoV-2 have great potential as antivirals, but their non-specific reactivity with thiols has limited their development. In this report, we performed an 8000 molecule electrophile screen against PLpro and identified an α-chloro amide fragment, termed compound 1, which inhibited SARS-CoV-2 replication in cells, and also had low non-specific reactivity with thiols. Compound 1 covalently reacts with the active site cysteine of PLpro, and had an IC50 of 18 μM for PLpro inhibition. Compound 1 also had low non-specific reactivity with thiols and reacted with glutathione 1–2 orders of magnitude slower than other commonly used electrophilic warheads. Finally, compound 1 had low toxicity in cells and mice and has a molecular weight of only 247 daltons and consequently has great potential for further optimization. Collectively, these results demonstrate that compound 1 is a promising lead fragment for future PLpro drug discovery campaigns.
Molecular cages with three-dimensional cavities have garnered significant interest due to their enhanced encapsulation abilities.
Estimating the probability of failure for complex real-world systems using high-fidelity computational models is often prohibitively expensive, especially when the probability is small. Exploiting low-fidelity models can make this process more feasible, but merging information from multiple low-fidelity and high-fidelity models poses several challenges. Here, this paper presents a robust multi-fidelity surrogate modeling strategy in which the multi-fidelity surrogate is assembled using an active learning strategy using an on-the-fly model adequacy assessment set within a subset simulation framework for efficient reliability analysis. The multi-fidelity surrogate is assembled by first applying a Gaussian process correction to each low-fidelity model and assigning a model probability based on the model's local predictive accuracy and cost. Three strategies are proposed to fuse these individual surrogates into an overall surrogate model based on model averaging and deterministic/stochastic model selection. The strategies also dictate which model evaluations are necessary. No assumptions are made about the relationships between low-fidelity models, while the high-fidelity model is assumed to be the most accurate and most computationally expensive model. Through two analytical and two numerical case studies, including a case study evaluating the failure probability of Tristructural isotropic-coated (TRISO) nuclear fuels, the algorithm is shown to be highly accurate while drastically reducing the number of high-fidelity model calls (and hence computational cost).
Unlike many superlattice structures, Ruddlesden–Popper phases have atomically abrupt interfaces useful for interrogating how periodic atomic layers affect thermal properties. Here, we measure the thermal conductivity in thin films of the n = 1–5 and 10 members of the (SrTiO 3 ) n SrO Ruddlesden–Popper superlattices grown by molecular-beam epitaxy and compare the results to a single crystal of the n = 1 Ruddlesden–Popper SrLaAlO 4 . The thermal conductivity cross-plane to the superlattice layering (k 33 ) is measured using time-domain thermoreflectance as a function of temperature and the results are compared to first-principles calculations. The thermal conductivity of this homologous series decreases with increasing interface density. Characterization by x-ray diffraction and scanning transmission electron microscopy confirms that these samples have a Ruddlesden–Popper superlattice structure.
The anomalous Hall, Nernst, and thermal Hall coefficients of the itinerant ferromagnet Fe3−xGeTe2 display anomalies upon cooling that are consistent with a topological transition that could induce deviations with respect to the Wiedemann–Franz (WF) law. This law has not yet been validated for the anomalous transport variables, with recent experimental studies yielding material-dependent results. Nevertheless, the anomalous Hall and thermal Hall coefficients of Fe3−xGeTe2 are found, within our experimental accuracy, to satisfy the WF law for magnetic fields μ0H applied along its c axis. Remarkably, large anomalous transport is also observed for μ0H||a axis with the field aligned along the gradient of the chemical potential generated by thermal gradients or electrical currents, a configuration that should not lead to their observation. These anomalous planar quantities are found to not scale with the component of the planar magnetization (M||), showing instead a sharp decrease beyond μ0H||= 4 T or the field required to align the magnetic moments along μ0H||. We argue that chiral spin structures associated with Bloch domain walls lead to a field-dependent spin chirality that produces a novel type of topological transport in the absence of interaction between the magnetic field and electrical or thermal currents. Locally chiral spin structures are captured by our Monte Carlo simulations incorporating small Dzyaloshinskii–Moriya and biquadratic exchange interactions. These observations reveal not only a new way to detect and expose topological excitations, but also a new configuration for heat conversion that expands the current technological horizon for thermoelectric energy applications.
Traditional Kinetic Monte Carlo (KMC) approaches, rooted in Gillespie’s stochastic simulation algorithm, become computationally demanding in systems with a large range of timescales. The goal of this work is to propose and study new adaptive lattice-KMC time integration strategies for spatially non-uniform systems. To that end, two novel adaptive tau-leaping methods and their corresponding time integration strategies are developed based on the idea of the “n-fold” direct KMC method. These strategies allow for the simultaneous execution of multiple reactions, advancing time by adaptively selected coarse increments. We present numerical experiments comparing the proposed methods with existing approaches in a catalytic surface kinetics application involving ammonia decomposition.
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Here, we report point-contact spectroscopy measurements on heavy fermion cousins CeCoIn 5 , Ce 2 PdIn 8 and Ce 3 PdIn 11 to systematically study the hybridization between f and conduction electrons. Below a temperature T *, the spectrum of each compound exhibits an evolving Fano-like conductance shape, superimposed on a sloping background, that suggests the development of hybridization between local f and itinerant conduction electrons in the coherent heavy fermion state below T *. We present a quantitative analysis of the conductance curves with a two-channel model to compare the tunneling process between normal metallic silver particles in our soft point-contact and heavy-fermion single crystals CeCoIn 5 , Ce 2 PdIn 8 and Ce 3 PdIn 11 .
The interior of a static Schwarzschild metric can be written in terms of two functions, similar to some models of anisotropic cosmology. With a suitable choice of canonical variables, we solve the Wheeler-DeWitt equation (WDW) inside the horizon of a Schwarzschild black hole. By imposing classicality near the horizon, and requiring boundedness of the wave function, we get a rather generic solution of the WDW equation, whose steepest-descent solution, i.e., the ridge of the wave function, coincides nicely with the classical trajectory. However, there is an ambiguity in defining the arrow of time which leads to two possible interpretations—(i) if there is only one arrow of time, one can infer that the steepest-descent of the wave function follows the classical trajectory throughout: coming from the event horizon and going all the way down to the singularity, while (ii) if there are two different arrows of time in two separate regimes, it can be inferred that the steepest-descent of the wave function comes inwards from the event horizon in one region while it moves outwards from the singularity in the other region, and there exists an annihilation process of these two parts of the wave function inside the horizon. Additionally, adopting the second interpretation could shed light on the information loss paradox: as time goes on, probabilities for histories that include black holes and singularities decay to zero and eventually only trivial geometries dominate.
Motivated by the lack of rotating solutions sourced by matter in General Relativity as well as in modified gravity theories, in this work we extend a recently discovered exact rotating solution of the minimal Einstein-scalar theory to its counterpart in Eddington-inspired Born-Infeld gravity coupled to a Born-Infeld scalar field. This is accomplished with the implementation of a well-developed mapping between solutions of Ricci-Based Palatini theories of gravity and General Relativity. The new solution is parametrized by the scalar charge and the Born-Infeld coupling constant apart from the mass and spin of the compact object. Compared to the spacetime prior to the mapping, we find that the high-energy modifications at the Born-Infeld scale are able to suppress but not remove the curvature divergence of the original naked null singularity. Depending on the sign of the Born-Infeld coupling constant, these modifications may even give rise to an additional timelike singularity exterior to the null one. In spite of that, both of the naked singularities before and after the mapping are capable of casting shadows, and as a consequence of the mapping relation, their shadows turn out to be identical as seen by a distant observer on the equatorial plane. Even though the scalar field induces a peculiar oblateness to the appearance of the shadow with its left and right endpoints held fixed, the closedness condition for the shadow contour sets a small upper bound on the absolute value of the scalar charge, which leads to observational features of the shadow closely resembling those of a Kerr black hole.
The TAROGE-M radio observatory is a self-triggered antenna array on top of the ∼2700 m high Mt. Melbourne in Antarctica, designed to detect impulsive geomagnetic emission from extensive air showers induced by ultra-high energy (UHE) particles beyond 1017 eV, including cosmic rays, Earth-skimming tau neutrinos, and particularly, the “ANITA anomalous events” (AAE) from near and below the horizon. The six AAE discovered by the ANITA experiment have signal features similar to tau neutrinos but that hypothesis is in tension either with the interaction length predicted by Standard Model or with the flux limits set by other experiments. Their origin remains uncertain, requiring more experimental inputs for clarification.
Abstract We argue that the difference in the yield ratio measured in Au+Au collisions at = 200 GeV and in Pb-Pb collisions at = 2.76 TeV is mainly owing to the different treatment of the weak decay contribution to the proton yield in the Au+Au collisions at = 200 GeV. We then use the coalescence model to extract from measured the information about the and nucleon density fluctuations at the kinetic freeze-out of heavy-ion collisions. We also show, using available experimental data, that the yield ratio is a more promising observable than for probing the local baryon-strangeness correlation in the produced medium.
Using electron-positron annihilation data samples corresponding to an integrated luminosity of 4.5 fb -1 , collected by the BESIII detector in the energy region between $4599.53$ $MeV$ and $4698.82$ $MeV$ we report the first observations of the Cabibbo-suppressed decays $Λ^{+}_{c}$ → $\mathcal{n}$$π$ + $π$ 0 , $Λ^{+}_{c}$ → $\mathcal{n}$$π$ + $π$ - $π$ + , and the Cabibbo-favored decay $Λ^{+}_{c}$ → $\mathcal{n}$$K$ - $π$ + $π$ + with statistical significances of $7.9σ$, $7.8σ$, and Misplaced &, respectively. The branching fractions of these decays are measured to be $\mathcal{B}$($Λ^{+}_{c}$ → $\mathcal{n}$$π$ + $π$ 0 ) = ($0.64 ± 0.09 ± 0.02$)%, $\mathcal{B}$($Λ^{+}_{c}$ → $\mathcal{n}$$π$ + $π$ - $π$ + ) = ($0.45 ± 0.07 ± 0.03$)%, and $\mathcal{B}$ $Λ^{+}_{c}$ → $\mathcal{n}$$K$ - $π$ + $π$ + ) = ($1.90 ± 0.08 ± 0.09$)% where the first uncertainties are statistical and the second are systematic. We find that the branching fraction of the decay $Λ^{+}_{c}$ → $\mathcal{n}$$π$ + $π$ 0 is about one order of magnitude higher than that of $Λ^{+}_{c}$ → $\mathcal{n}$ $π$ + .
We report a search for a heavier partner of the recently observed Z cs (3985) - state, denoted as $Z^{'-}_{cs}$, in the process e + e - → $K$ + $D^{*}_{s}$ - $D$ *0 + c.c., based on e + e - collision data collected at the center-of-mass energies of $\sqrt{s}$ = 4.661, 4.682 and 4.699 GeV with the BESIII detector. The $Z^{'-}_{cs}$ is of interest as it is expected to be a candidate for a hidden-charm and open-strange tetraquark. A partial-reconstruction technique is used to isolate K + recoil-mass spectra, which are probed for a potential contribution from $Z^{'-}_{cs}$ → $D^{*}_{s}$ - $D$ *0 + (c.c.). We find an excess of $Z^{'-}_{cs}$ → $D^{*}_{s}$ - $D$ *0 + (c.c.) candidates with a significance of 2.1σ, after considering systematic uncertainties, at a mass of 4123.5 ± 0.7 stat. ± 4.7 syst. ) MeV/c 2 . As the data set is limited in size, the upper limits are evaluated at the 90% confidence level on the product of the Born cross sections (σ BORN ) and the branching fraction ($\mathcal{B}$) of $Z^{'-}_{cs}$ → $D^{*}_{s}$ - $D$ *0 , under different assumptions of the $Z^{'-}_{cs}$ mass from 4.120 to 4.140 MeV and of the width from 10 to 50 MeV at the three center-of-mass energies. The upper limits of σ BORN ∙ $\mathcal{B}$ are found to be at the level of $\mathcal{O}$(1) pb at each energy. Larger data samples are needed to confirm the $Z^{'-}_{cs}$ state and clarify its nature in the coming years.
Abstract Usingannihilation data corresponding to an integrated luminosity of 2.93taken at the center-of-mass energyGeV with the BESIII detector, a joint amplitude analysis is performed on the decaysand(non-η). The fit fractions of individual components are obtained, and large interferences among the dominant components of the decays,,, andare observed in both channels. With the obtained amplitude model, the-even fractions ofand(non-η) are determined to be% and%, respectively. The branching fractions ofand(non-η) are measured to be% and%, respectively. The amplitude analysis provides an important model for the binning strategy in measuring the strong phase parameters ofwhen used to determine the CKM anglevia thedecay.