Sandia National Laboratories California

The 2022 Russian attacks on the Chernobyl and Zaporizhzhia nuclear facilities in Ukraine shocked the international community. Claims that the attacks constituted war crimes immediately entered the public consciousness, and a flurry of opinions were set forth on the international humanitarian law (“IHL”) protections afforded to nuclear plants, focusing on Article 56 of Additional Protocol I of the Geneva Conventions, which provides special protection to nuclear electrical generating stations. These opinions primarily focused on the immediate applicability and shortcomings of Article 56 on the attacks at hand, often operating on the presumption that a massively consequential environmental and humanitarian disaster would occur should hostilities continue. Now almost four years on, with no end to Russian-Ukrainian hostilities in sight, there still exists a glaring shortcoming of IHL with respect to Article 56: the consequences of the most significant radiological disasters in history have difficulty in meeting the criteria Article 56 has in place to hold a warring state accountable for causing a radiological incident. Undertaking an in-depth examination of the consequences of nuclear accidents, the IHL provisions in place that may be relevant to a nuclear incident, and how those provisions may actually apply to real-life consequences, this article finds the current IHL frameworks protecting nuclear installations to be inadequate, suggesting that affording nuclear facilities protection in times of war is best done via a technology-neutral classification scheme, rather than existing technology-specific doctrines.

This experimental and numerical study evaluates how ducted fuel injection (DFI) and pilot injections interact to impact soot formation and the premixed heat release pressure spike in diesel combustion. Experiments showed that pilot injections reduced the premixed heat release spike of a free spray by approximately 70%, while DFI configurations only experienced a decrease of approximately 25%. Similarly, pilot injections reduced the initial lift-off length (LOL) of the main injection of a free-spray by approximately 30%, while DFI’s initial LOL had little to no change when pilot injections were utilized. Regardless of whether a standalone-main or pilot-main strategy was used, DFI was able to reduce the spatially integrated natural luminosity (SINL) of the flame relative to a free spray, indicating a likely reduction in soot formation. Both duct configurations studied produced steady SINL signals which were approximately 30% and 70% of the free-spray’s, respectively. For DFI, pilot injections further reduced the peak SINL compared to a standalone main by approximately 16%. The decrease in peak SINL correlated with increased spray head penetration rates. The numerical study revealed that pilot injections led to leaner mixtures near the tip of the penetrating spray for all configurations. Thus, unaffected LOLs, leaner penetrating spray tips, and a reduced time for soot formation possibly led to less soot in the head of the transient penetrating spray when DFI is used in conjunction with pilot injections.

Abstract Bacteriophages are ubiquitous in nature, but relatively few have been isolated and characterized compared to the number of bacterial strains. Phage biotechnology applications benefit from a diverse library of isolated phages to kill or transfer genetic material to a bacterium of interest. However, scaling phage discovery for diverse bacterial hosts can be time consuming and costly. We developed an approach to capture novel phages for multiple bacteria strains in parallel from an environmental sample using commercially available 0.2-micron filter plates. Using this H igh- t hroughput P hage Isolation P latform (HtPIP), we isolated twelve novel phages spanning nine diverse bacterial host genera. Eleven of the isolated phages define new phage species with nine also defining new genera. We show the HtPIP can discover both DNA and RNA phages; including a Tectiviridae infecting Pseudomonas putida mt-2 and a Leviviricetes infecting a Microbacterium isolate, which represents the first cultured RNA phage infecting a host outside of proteobacteria. Using a metagenomic approach, we demonstrate that the HtPIP captures a higher proportion of novel phages compared to traditional low-throughput methods.

Abstract Permafrost coastlines are experiencing significant erosion as polar amplification has enhanced the effects of climate change in the Arctic. Warmer temperatures are increasing thermo‐denudation and more energetic oceans are increasing thermo‐abrasion in unlithified, ice‐bonded permafrost coastlines which comprise at least 40% of the circum‐Arctic coastline. Here we present developments to and calibration of the Arctic Coastal Erosion (ACE) model, which couples oceanographic and atmospheric conditions at storm‐resolving time steps with a finite element multi‐physics terrestrial permafrost model. This ice‐bonded unlithified permafrost model unites 3D thermal and mechanical governing equations by allowing heat conduction with solid‐liquid phase change to drive ice saturation, which governs evolution of mechanical stress‐strain fields. Developments to the ACE terrestrial model, including introduction of novel erosion criteria to remove failed elements, reformulation of the mechanical material model, and wave pressure boundary conditions, enable simulation of both slowly advancing thermo‐denudation with permafrost sloughing from the face and highly episodic thermo‐abrasion with niche formation and rapidly advancing block failure. A 2018 summer field campaign at Drew Point, Alaska with observations of thermo‐denudation and thermo‐abrasion, including niche geometry before block failure, enable calibration of the terrestrial model. Detailed compositional and geomechanical characterization of the ice‐bonded sediments enabled advances in the material model representation and calibrated model parameters. We demonstrate a daily root‐mean square error of 0.12 m for thermo‐denudation over the summer and achieve block failure within 2 hr of the observed. The calibrated ACE model is the first step towards simulation of other ice‐bonded unlithified circum‐Arctic coastlines for various applications.

We present an algebraic hp-multigrid method for high-order matrix-free methods. Algebraic multigrid methods often require information about matrix entries, which are not available in a matrix-free setting; however, when rediscretization for geometric multigrid is not available for a matrix-free method, coarsening must be constructed using information from the mesh. Leveraging only mesh adjacency information, this algorithm constructs an algebraic multigrid hierarchy without requiring geometric coarsening or explicit matrix assembly, making it well-suited for GPU‑accelerated architectures. This paper presents the implementation of the matrix-free method in the high-fidelity computational fluid dynamics framework Neko, which utilizes spectral element methods with an implicit-explicit scheme to solve the incompressible Navier-Stokes equations. We utilize an hp-multigrid approach, where the problem is first coarsened from high-order polynomials to low-order polynomials, and then the low-order system is further coarsened spatially in an matrix-free fashion using mesh adjacency information. Finally, we present numerical results from the Dardel and LUMI supercomputers that demonstrate the performance and scalability of our method as well as its applicability to real-world applications.