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In high-performance computing (HPC), modern supercomputers typically provide exclusive computing resources to user applications. Nevertheless, the interconnect network is a shared resource for both inter-node communication and across-node I/O access, among co-running workloads, leading to inevitable network interference. In this study, we develop MFNetSim, a multi-fidelity modeling framework that enables simulation of multi-traffic simultaneously over the interconnect network, including inter-process communication and I/O traffic. By combining different levels of abstraction, MFNetSim can efficiently co-model the communication and I/O traffic occurring on HPC systems equipped with flash-based storage. We conduct simulation studies of hybrid workloads composed of traditional HPC applications and emerging ML applications on a 1,056-node Dragonfly system with various configurations. Our analysis provides various observations regarding how network interference affects communication and I/O traffic. 

Abstract Increasing fine root carbon (FRC) inputs into soils has been proposed as a solution to increasing soil organic carbon (SOC). However, FRC inputs can also enhance SOC loss through priming. Here, we tested the broad-scale relationships between SOC and FRC at 43 sites across the US National Ecological Observatory Network. We found that SOC and FRC stocks were positively related with an across-ecosystem slope of 7 ± 3 kg SOC m⁻²per kg FRC m⁻², but this relationship was driven by grasslands. Grasslands had double the across-ecosystem slope while forest FRC and SOC were unrelated. Furthermore, deep grassland soils primarily showed net SOC accrual relative to FRC input. Conversely, forests had high variability in whether FRC inputs were related to net SOC priming or accrual. We conclude that while FRC increases could lead to increased SOC in grasslands, especially at depth, the FRC-SOC relationship remains difficult to characterize in forests. 

The field of ichnology has been a branch of paleontology since the mid 19th century. Vertebrate tracks are a vast dataset compared to vertebrate body fossils: an individual organism will leave only one body, but will leave many tracks and only one body to potentially be preserved. Tracks are direct records of organismal behavior and can be used as proxies for biodiversity and paleoecology. The use of anatomy-consistent morphology in ichnotaxonomy incorporates trackmaker identity by correlating the morphology of the track with that of available track-maker(s). Standard practice is to interpret ichnotaxa to a family level for trackmakers, but the Linnaean rank and cladistic status of trackmaker taxa actually varies greatly. Our work aims to harmonize the ichnological and body fossil records of early Carboniferous tetrapods to better ground trackmaker inferences. For example, the Pennsylvanian-Permian ichnogenus Limnopus is referred to eryopid temnospondyls. However, large ichnospecies (e.g., L. littoralis, L. waynesburgensis) are 200% larger than small ichnospecies (e.g., L. vagus). It has been suggested that the different ichnospecies of Limnopus represent distinct ontogenetic stages of the trackmaker, including the similar but smaller ichnogenus Batrachichnus. Of the few Carboniferous temnospondyls for which the manus and pes are both known in detail, the morphology of the large Limnopus morph is consistent with that of Eryops, but edopid trackmakers cannot be discounted. This has minimal implications for reconstructing ecosystems, given the similarities between eryopids and edopids. However, this uncertainty in the identity of the trackmaker makes the use of Limnopus as a biostratigraphic appearance datum for Eryopidae problematic. The recent consolidation of Limnopus species into the type (L. heterodactylopus) ensures greater ichnotaxonomic consistency, but weakens the track-trackmaker link. Interpretation of Carboniferous pentadactyl tracks must account for the presence of pentadactyly among multiple stem tetrapod families by the late Mississippian. Trackways and skeletal remains — specifically autopodia — are scant in the earlier Mississippian, but both hint at a reduction of pedal digit number to five by this time. The timing of manual digit reduction remains uncertain, but coexistence of a probably hexadactyl manus (Pederpes, Whatcheeriidae) with pendatactyl and tetradactyl manual prints highlights the earliest Carboniferous as a time of diversity and dynamism in early tetrapod morphology. 

Motivated by previous work on kinetic energy cascades in the ocean, atmosphere, plasmas, and other fluids, we develop a spatiotemporal spectral transfer tool that can be used to study scales of variability in generalized dynamical systems. In particular, we use generalized time-frequency methods from signal analysis to broaden the applicability of frequency transfers from theoretical to practical fluids applications such as the study of observational data or simulation output. We also show that triad interactions in wavenumber used to study kinetic energy and enstrophy cascades can be generalized to study triad interactions in frequency or wavenumber frequency. We study the effects of sweeping on the locality of frequency transfers and frequency triad interactions to better understand the locality of spatiotemporal frequency transfers. As an illustrative example, we use the spatiotemporal spectral transfer tool to study the results of a simulation of two-dimensional homogeneous isotropic turbulence. This simulated fluid is forced at a well-defined wavenumber and frequency with dissipation occurring at both large and small scales, making this one of the first studies of “modulated turbulence” in two dimensions. Our results show that the spatiotemporal transfers we develop in this paper are robust to potential practical problems such as low sampling rates or nonstationarity in time series of interest. We anticipate that this method will be a useful tool in studying scales of spatiotemporal variability in a wide range of fluids applications as higher resolution observations and simulations of fluids become more widely available. Published by the American Physical Society2025