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At least 613 records · Page 34

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DOE OSTI2021

FMX – the Frontier Microfocusing Macromolecular Crystallography Beamline at the National Synchrotron Light Source II

Two new macromolecular crystallography (MX) beamlines at the National Synchrotron Light Source II, FMX and AMX, opened for general user operation in February 2017 [Schneider et al. (2013). J. Phys. Conf. Ser. 425 , 012003; Fuchs et al. (2014). J. Phys. Conf. Ser. 493 , 012021; Fuchs et al. (2016). AIP Conf. Proc. SRI2015 , 1741 , 030006]. FMX, the micro-focusing Frontier MX beamline in sector 17-ID-2 at NSLS-II, covers a 5–30 keV photon energy range and delivers a flux of 4.0 × 10 12 photons s −1 at 1 Å into a 1 µm × 1.5 µm to 10 µm × 10 µm (V × H) variable focus, expected to reach 5 × 10 12 photons s −1 at final storage-ring current. This flux density surpasses most MX beamlines by nearly two orders of magnitude. The high brightness and microbeam capability of FMX are focused on solving difficult crystallographic challenges. The beamline's flexible design supports a wide range of structure determination methods – serial crystallography on micrometre-sized crystals, raster optimization of diffraction from inhomogeneous crystals, high-resolution data collection from large-unit-cell crystals, room-temperature data collection for crystals that are difficult to freeze and for studying conformational dynamics, and fully automated data collection for sample-screening and ligand-binding studies. FMX's high dose rate reduces data collection times for applications like serial crystallography to minutes rather than hours. With associated sample lifetimes as short as a few milliseconds, new rapid sample-delivery methods have been implemented, such as an ultra-high-speed high-precision piezo scanner goniometer [Gao et al. (2018). J. Synchrotron Rad. 25 , 1362–1370], new microcrystal-optimized micromesh well sample holders [Guo et al. (2018). IUCrJ , 5 , 238–246] and highly viscous media injectors [Weierstall et al. (2014). Nat. Commun. 5 , 3309]. The new beamline pushes the frontier of synchrotron crystallography and enables users to determine structures from difficult-to-crystallize targets like membrane proteins, using previously intractable crystals of a few micrometres in size, and to obtain quality structures from irregular larger crystals.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2021

Effect of Branch Length on the Structural and Separation Properties of Hyperbranched Poly(1,3-dioxolane)

Polymers containing poly(ethylene oxide) (PEO) demonstrate superior membrane CO 2 /N 2 separation properties owing to their polar ether oxygen groups exhibiting strong affinity toward CO2. Poly(1,3-dioxolane) (PDXL) shows an ether oxygen content higher than PEO and is expected to have higher CO 2 /N 2 solubility selectivity. However, similar to PEO, the high crystallinity of PDXL greatly reduces its gas permeability. Herein, amorphous PDXL-based hyperbranched polymers were synthesized by ring opening of 1,3-dioxolane (DXL) to form poly(1,3-dioxolane) acrylate (DXLAn) followed by photopolymerization. The repeating unit of DXL (n) or branch length was systematically varied from 4 to 12 to yield amorphous polymers. The chemical and physical properties of the obtained polymers (PDXLAn) were thoroughly evaluated and used to interpret pure- and mixed-gas transport characteristics. The polymers exhibit attractive CO 2 /N 2 and CO 2 /CH 4 separation properties. For example, PDXLA8 exhibits a CO 2 permeability of 220 Barrer and CO 2 /N 2 selectivity of 56 at 35 °C, surpassing Robeson’s 2008 upper bound, and it shows robust separation performance when evaluated with simulated flue gas at 60 °C. This study demonstrates that hyperbranched structures are an effective route to construct amorphous yet highly polar polymers and that chain end groups are instrumental in determining the structural and gas transport characteristics.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2022

Atomically dispersed Ag on δ-MnO 2 via cation vacancy trapping for toluene catalytic oxidation

The regulation of metal–support interaction (MSI) and the improvement of noble metal utilization are the frontiers of volatile organic compound (VOC) catalytic oxidation. Here, we report a H 2 O 2 -assisted synthesis process for trapping Ag + onto the engineered Mn vacancies of δ-MnO 2 for the catalytic oxidation of toluene. Due to the strong MSI between Ag and δ-MnO 2 , the monoatomic Ag + anchored on cation vacancies forms longer and weakened Ag–O bonds compared with Ag 2 O, which can extra promote the formation of oxygen vacancies and the activation of adjacent lattice oxygen in Ag–O–Mn units compared with regular nanoparticle counterparts. It is beneficial to the steps of methyl dehydrogenation, demethylation, and benzene ring cleavage. The catalyst yields excellent toluene oxidation activity, enhanced turnover frequency in terms of Ag, and good stability. Finally, we propose in this study a facile design strategy for fabricating stably atomically dispersed metal sites, as well as clarify the structure–activity relationships during toluene catalytic oxidation, especially the important effect of single-atom Ag on the adjacent local structure.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2024

Generation of superposed orbital angular momentum beams using a free-electron laser oscillator

With wavelength tunability, free-electron lasers (FELs) are well-suited for generating orbital angular momentum (OAM) beams in a wide photon energy range. We report here the first experimental demonstration of OAM beam generation using an oscillator FEL with the tens of picosecond pulse duration. Lasing around 458 nm, we have produced the four lowest orders of superposed Laguerre-Gaussian beams using a very long FEL resonator of 53.73 m. The produced beams have good beam quality, excellent stability, and substantial average power. We have also developed a pulsed operation mode for these beams with a highly reproducible temporal structure for a range of repetition rate of 1–30 Hz. This development can be extended to short wavelengths, for example to x-rays using a future x-ray FEL oscillator. The OAM operation of such a storage-ring FEL also paves the way for the generation of OAM gamma-ray beams via inverse Compton scattering.

47 OTHER INSTRUMENTATION↗

DOE OSTI2025

Single-Bunch Instabilities at the Fermilab Recycler Ring

Understanding and characterizing collective instabilities is critical for high-intensity operation at the Fermilab Recycler Ring. This work presents an application of the the Nested Head-Tail (NHT) formalism for modeling single-bunch transverse instabilities, incorporating analytical solutions to the resistive wall impedances in the absence of space charge. Predicted growth rates and mode structures are benchmarked against PyHEADTAIL simulations and ongoing experimental measurements. The experimental program includes studies of bare-machine instabilities at different machine parameters. These results support the understanding of naturally-occurring instabilities in the Recycler and contribute to the development of predictive tools for beam stability in future high-intensity configurations.

Gonzalez-Ortiz, C. [Fermilab]↗

DOE OSTI2025

Single-Bunch Instabilities at the Fermilab Recycler Ring

Gonzalez-Ortiz, Cristhian [Fermilab]↗

DOE OSTI2025

Topological phase transition to a hidden charge density wave liquid

Charge density waves (CDWs), electronic crystals that form within a host solid, have long been speculated to melt into a spatially textured electronic liquid. Though they have not been previously detected, liquid CDWs may nonetheless be fundamental to the phase diagrams of many correlated electron systems, including high temperature superconductors and quantum Hall states. In one of the most promising candidate materials capable of hosting a liquid CDW, 1T-TaS2, a structural phase transition impedes its observation. Here, by irradiating the material with a femtosecond light pulse, we circumvent the structural phase transition to reveal how topological defect dynamics govern the otherwise invisible CDW correlations. Upon photoexcitation, the CDW diffraction peaks broaden azimuthally, initially revealing a hexatic state. At higher temperatures, photoexcitation completely destroys translational and orientational order and only a ring of diffuse scattering is observed, a key signature of a liquid CDW. Our work provides compelling evidence for a defect-unbinding transition to a CDW liquid and presents a protocol for uncovering states that are hidden by other transitions in thermal equilibrium.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2023

Measurement of e + e − → ωπ+π− cross section at $\sqrt{s}$ = 2.000 to 3.080 GeV

A partial wave analysis on the process e⁺e⁻ → ωπ⁺π⁻ is performed using 647 pb -1 of data sample collected by using the BESIII detector operating at the BEPCII storage ring at center-of-mass (c.m.) energies from 2.000 GeV to 3.080 GeV. The Born cross section of the e⁺e⁻ → ωπ⁺π⁻ process is measured, with precision improved by a factor of 3 compared to that of previous studies. A structure near 2.25 GeV is observed in the energy-dependent cross sections of e⁺e⁻ → ωπ⁺π⁻ and ωπ 0 π 0 with a statistical significance of 7.6σ, and its determined mass and width are 2232 ± 19 ± 27 MeV/c 2 and 93 ± 53 ± 20 MeV, respectively, where the first and second uncertainties are statistical and systematic, respectively. By analyzing the cross sections of subprocesses e⁺e⁻ → ωf 0 (500), ωf 0 (980), ωf 0 (1370), ωf 2 (1270), and b1(1235)π, a structure, with mass M = 2200 ± 11 ± 17 MeV/c 2 and width Γ = 74 ± 20 ± 24 MeV, is observed with a combined statistical significance of 7.9σ. The measured resonance parameters will help to reveal the nature of vector states around 2.25 GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2025

Improved damage tolerance of SiC-based nuclear fuel cladding with novel multi-layered SiC coating design at 1200 °C

Continuous SiC fibre reinforced SiC matrix composites (SiC f -SiC m ) with monolithic SiC outer coatings are considered as a damage-tolerant cladding design for loss of coolant accident (LOCA) conditions in light water reactors. However, monolithic SiC coatings are brittle and prone to catastrophic failure. In this study, a SiC f -SiC m cladding with a novel multi-layer SiC outer coating (11 sub-layers, ∼260 µm in total thickness) was investigated under C-ring compression at room temperature and 1200 °C in argon environment. Real-time synchrotron X-ray computed tomography (XCT) was employed to capture crack initiation and propagation processes. Compared to conventional monolithic SiC outer coatings, the multi-layer coating structure facilitated crack deflection and bifurcation enhancing its damage tolerance at both temperatures. Despite pre-existing surface cracks, claddings exhibited stable mechanical-performance at both temperatures. These initial cracks did not critically affect the failure processes as they were not aligned with the maximum stress direction. Furthermore, the microstructure, distribution of residual stresses, and local properties of individual components in the material were thoroughly characterized, and compared with open literature on conventional claddings with monolithic outer coatings. These results provide new insights into the failure mechanisms of multi-layer SiC coatings and offer guidance for the future design of accident-tolerant nuclear fuel claddings.

36 - MATERIALS SCIENCE↗

DOE OSTI2025

Automated tuning of a ring-assisted MZI-based interleaver for Kerr frequency combs

We demonstrate a compact ring-assisted Mach–Zehnder interferometer (RAMZI)-based silicon photonic interleaver with a 400 GHz free spectral range (FSR), featuring flat passbands exceeding a spectral range of 50 nm. Additionally, we introduce a novel, to the best of our knowledge, add-on structure and tuning method enabling automated compensation for fabrication imperfections, precise shaping of the RAMZI flat-top passbands, and alignment with Kerr comb lines. Experimental results have shown successful interleaving of eight channels of distributed-feedback (DFB) lasers as well as a 200 GHz Kerr comb, both achieving an extinction ratio of approximately 20 dB.

Wang, Songli (ORCID:0009000626380795)↗

DOE OSTI2024

Experimental verification of integrability in a Danilov-Nagaitsev lattice using machine learning

In non-linear optics, achieving integrability can enhance the dynamic aperture in storage rings. We analyze turn-by-turn phase-space data from our Danilov-Nagaitsev lattice implementation at Fermilab's Integrable Optics Test Accelerator using machine learning. AI Poincaré estimates conserved quantities from experimental data without prior knowledge of the invariant structure, showing qualitative agreement with theoretical predictions. Additionally, one of the two learned invariants exhibits comparable or better conservation compared to known theoretical expressions.

43 PARTICLE ACCELERATORS↗

DOE OSTI2025

Integral Field Probe for Mapping of Curved Magnets

The Single Stretched Wire (SSW) method allows highly precise integral field measurements by recording voltage across a tensioned wire mounted to 2-axis linear stages at either end of the magnet aperture. However, traditional SSW probes are not well suited for curved accelerator magnets, which are essential for steering charged particles along arced trajectories in storage rings or beamlines. The tension required to eliminate sag demands a purely straight path, making them incompatible with non-linear magnet geometries. To address this limitation for curved magnets, a modified approach was developed using a segmented, 3D-printed support structure that incorporates a pre-shaped anti-sag curve. Under its own weight and that of the wire bundle, the structure deforms to lie flat while conforming to the curvature of the magnet in the horizontal plane. The optimal geometry of the probe was derived using an iterative process combining FEA simulations in Ansys Mechanical with testing of various carbon fiber-reinforced filaments. The printed and assembled probe was successfully used to measure the SDD-059 magnet at Fermilab, yielding promising results.

Jakopin, Alexander [Northern Illinois U.]↗

DOE OSTI2020

Cyclic Topology Enhancing Structural Ordering and Stability of Comb-Shaped Polypeptoid Thin Films against Melt-Induced Dewetting

We investigated the effect of cyclic chain topology on the molecular ordering and thermal stability of comb-shaped polypeptoid thin films on silicon (Si) substrates. Cyclic and linear poly(N-decylglycine) (PNDG) bearing long n-decyl side chains were synthesized by ring-opening polymerization of N-decylglycine-derived N-carboxyanhydrides. When the spin-coated thin films were subjected to thermal annealing at temperatures above the melting temperature (T > T m ), the cyclic PNDG films exhibited significantly enhanced stability against melt-induced dewetting than the linear counterparts (l-PNDG). When recrystallized at temperatures below the crystallization temperature (T < T c ), the homogeneous c-PNDG films exhibit enhanced crystalline ordering relative to the macroscopically dewetted l-PNDG films. Both cyclic and linear PNDG molecules adopt cis-amide conformations in the crystalline film, which transition into trans-amide conformations upon melting. A top-down solvent leaching treatment of both l/c-PNDG films revealed the formation of an irreversibly physisorbed monolayer with similar thickness (ca. 3 nm) on the Si substrate. The physisorbed monolayers are more disordered relative to the respective thicker crystalline films for both cyclic and linear PNDGs. Upon heating above T m , the adsorbed c-PNDG chains adopt trans-amide backbone conformation identical with the free c-PNDG molecules in the molten film. By contrast, the backbone conformations of l-PNDG chains in the adsorbed layers are notably different from those of the free chains in the molten film. We postulate that the conformational disparity between the chains in the physically adsorbed layers versus the free chains in the molten film is an important factor to account for the difference in the thermal stability of PNDG thin films. These findings highlight the use of cyclic chain topology to suppress the melt-induced dewetting in polymer thin films.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Distance-Selected Topochemical Dehydro-Diels–Alder Reaction of 1,4-Diphenylbutadiyne toward Crystalline Graphitic Nanoribbons

Solid-state topochemical polymerization (SSTP) is a promising method to construct functional crystalline polymeric mate-rials, but contrast to various reactions happened in solution, only very limited types of SSTP reactions are reported. Diels-Alder (DA) and dehydro-DA (DDA) reaction are textbook reactions for preparing six-membered rings in solution, but scarcely seen in solid-state synthesis. Here, using multiple cutting-edge techniques, we demonstrate that the solid 1,4-diphenylbutadiyne (DPB) undergoes a DDA reaction under 10-20 GPa with the phenyl as the dienophile. The crystal structure at the critical pressure shows this reaction is “distance selected”. The distance of 3.2 Å between the phenyl and the phenylethynyl facilitates the DDA reaction, while the distances for other DDA and 1, 4-addition reactions are too large to allow the bonding. The obtained products are crystalline armchair graphitic nanoribbons, and hence our studies open a new route to construct the crystalline carbon materials with atomic-scale control.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2026

Microcanonical Kinetics of Water-Mediated Proton Transfer in 4ABAH + ·(H 2 O) n = 4–6 Clusters (ABA = Aminobenzoic Acid): A Model System for Size-Dependent Relaxation to Ergodic Behavior

Here, we leverage the unique properties of the 4ABAH + · (H 2 O) n clusters (ABA = 4-aminobenzoic acid, n = 4−6) to quantitatively address how a finite, isolated system evolves into an ergodic condition starting from localized arrangements in configuration space. This system adopts two distinct structural isomers in which water molecules cluster around the cationic centers of its two protomers with widely separated positive charge centers. These isomers arise from excess proton attachment to either the acid (O) or amino (N) group on opposite sides of the benzene ring. Both forms are captured and kinetically trapped using cryogenic ion methods and then selectively vibrationally excited through their mutually exclusive IR bands involving NH and OH stretching fundamentals. Because the IR excitation lies below the water binding energy, the system can evolve to explore slow, rare events that lead to the interconversion between the two isomers. The rates of these intracluster reactions are determined by using a pump−probe scheme involving ∼5 ns IR pump and UV probe lasers. The rates occur on the microsecond time scale, leading to steady state populations of the isomers, thus revealing the cluster size-dependent fractionation between the two species at microcanonical equilibrium. The steady state distributions are correlated with the expected trend in the cluster size-dependent reaction energetics, which are in turn consistent with changes in the relative densities of states of the two species. These results thus provide an unusually clear example in which complex, protic-solvent-mediated chemical transformations are captured within a finite system at a precisely determined internal energy.

Rana, Abhijit [Yale Univ., New Haven, CT (United S↗

DOE OSTI2022

Active conformation of the p97-p47 unfoldase complex

The p97 AAA+ATPase is an essential and abundant regulator of protein homeostasis that plays a central role in unfolding ubiquitylated substrates. Here we report two cryo-EM structures of human p97 in complex with its p47 adaptor. One of the conformations is six-fold symmetric, corresponds to previously reported structures of p97, and lacks bound substrate. The other structure adopts a helical conformation, displays substrate running in an extended conformation through the pore of the p97 hexamer, and resembles structures reported for other AAA unfoldases. These findings support the model that p97 utilizes a “hand-over-hand” mechanism in which two residues of the substrate are translocated for hydrolysis of two ATPs, one in each of the two p97 AAA ATPase rings. Proteomics analysis supports the model that one p97 complex can bind multiple substrate adaptors or binding partners, and can process substrates with multiple types of ubiquitin modification.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2025

Enzyme-mediated aminoglycoside resistance without target mimicry

Abstract The primary mode of resistance to aminoglycoside antibiotics is through chemical modification catalyzed by aminoglycoside-modifying enzymes. Numerous structural studies of these enzymes have invariably shown that they bind aminoglycosides in the same lowest-energy conformation as the intended target for these antibiotics, the A site of the bacterial ribosome. Presumably, the binding mode mimicry enables these enzymes to compete successfully with the target, thus conferring effective resistance. Here we present the first structural and functional studies of two aminoglycoside-modifying enzymes that do not use target mimicry, AAC(3)-Ia and AAC(3)-XIa. X-ray diffraction studies reveal that these enzymes bind aminoglycoside antibiotics in a conformation where the central 2-deoxystreptamine ring is in boat conformation. The effect of this non-canonical binding mode on the enzymes’ ability to modify antibiotics is assessed in silico and in vitro, and its impact for conferring resistance is assessed in vivo. Overall, the results show that target mimicry, while advantageous, is not an essential strategy for aminoglycoside-modifying enzymes to be effective in conferring resistance.

Chemistry↗

DOE OSTI2022

Ultrafast perturbation of magnetic domains by optical pumping in a ferromagnetic multilayer

Ultrafast optical pumping of spatially nonuniform magnetic textures is known to induce far-from-equilibrium spin transport effects. Here, we use ultrafast x-ray diffraction with unprecedented dynamic range to study the laser-induced dynamics of labyrinth domain networks in ferromagnetic CoFe/Ni multilayers. We detected azimuthally isotropic, odd order, magnetic diffraction rings up to fifth order. The amplitudes of all three diffraction rings quench to different degrees within 1.6 ps. In addition, all three of the detected diffraction rings both broaden by 15% and radially contract by 6% during the quench process. We are able to rigorously quantify a 31% ultrafast broadening of the domain walls via Fourier analysis of the order-dependent quenching of the three detected diffraction rings. Here, the broadening of the diffraction rings is interpreted as a reduction in the domain coherence length, but the shift in the ring radius, while unambiguous in its occurrence, remains unexplained. In particular, we demonstrate that a radial shift explained by domain-wall broadening can be ruled out. With the unprecedented dynamic range of our data, our results provide convincing evidence that labyrinth domain structures are spatially perturbed at ultrafast speeds under far-from-equilibrium conditions, albeit the mechanism inducing the perturbations remains yet to be clarified.

36 MATERIALS SCIENCE↗