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1. The Habitat of the Nascent Chicxulub Crater

   https://doi.org/10.1029/2020AV000208  

   Bralower, T. J.; Cosmidis, J.; Fantle, M. S.; Lowery, C. M.; Passey, B. H.; Gulick, S. P. S.; Morgan, J. V.; Vajda, V.; Whalen, M. T.; Wittmann, A.; et al (November 2020, AGU Advances)

   Abstract An expanded sedimentary section provides an opportunity to elucidate conditions in the nascent Chicxulub crater during the hours to millennia after the Cretaceous‐Paleogene (K‐Pg) boundary impact. The sediments were deposited by tsunami followed by seiche waves as energy in the crater declined, culminating in a thin hemipelagic marlstone unit that contains atmospheric fallout. Seiche deposits are predominantly composed of calcite formed by decarbonation of the target limestone during impact followed by carbonation in the water column. Temperatures recorded by clumped isotopes of these carbonates are in excess of 70°C, with heat likely derived from the central impact melt pool. Yet, despite the turbidity and heat, waters within the nascent crater basin soon became a viable habitat for a remarkably diverse cross section of the food chain. The earliest seiche layers deposited with days or weeks of the impact contain earliest Danian nannoplankton and dinocyst survivors. The hemipelagic marlstone representing the subsequent years to a few millennia contains a nearly monogeneric calcareous dinoflagellate resting cyst assemblage suggesting deteriorating environmental conditions, with one interpretation involving low light levels in the impact aftermath. At the same horizon, microbial fossils indicate a thriving bacterial community and unique phosphatic fossils including appendages of pelagic crustaceans, coprolites and bacteria‐tunneled fish bone, suggesting that this rapid recovery of the base of the food chain may have supported the survival of larger, higher trophic‐level organisms. The extraordinarily diverse fossil assemblage indicates that the crater was a unique habitat in the immediate impact aftermath, possibly as a result of heat and nutrients supplied by hydrothermal activity. 

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2. The Dual Graph Shift Operator: Identifying the Support of the Frequency Domain

   https://doi.org/10.1007/s00041-021-09850-1  

   Leus, Geert; Segarra, Santiago; Ribeiro, Alejandro; Marques, Antonio G. (June 2021, Journal of Fourier Analysis and Applications)

   null (Ed.)

   Abstract Contemporary data is often supported by an irregular structure, which can be conveniently captured by a graph. Accounting for this graph support is crucial to analyze the data, leading to an area known as graph signal processing (GSP). The two most important tools in GSP are the graph shift operator (GSO), which is a sparse matrix accounting for the topology of the graph, and the graph Fourier transform (GFT), which maps graph signals into a frequency domain spanned by a number of graph-related Fourier-like basis vectors. This alternative representation of a graph signal is denominated the graph frequency signal. Several attempts have been undertaken in order to interpret the support of this graph frequency signal, but they all resulted in a one-dimensional interpretation. However, if the support of the original signal is captured by a graph, why would the graph frequency signal have a simple one-dimensional support? Departing from existing work, we propose an irregular support for the graph frequency signal, which we coin dual graph. A dual GSO leads to a better interpretation of the graph frequency signal and its domain, helps to understand how the different graph frequencies are related and clustered, enables the development of better graph filters and filter banks, and facilitates the generalization of classical SP results to the graph domain. 

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3. The neuroecology of the water-to-land transition and the evolution of the vertebrate brain

   https://doi.org/10.1098/rstb.2020.0523  

   MacIver, Malcolm A.; Finlay, Barbara L. (February 2022, Philosophical Transactions of the Royal Society B: Biological Sciences)

   The water-to-land transition in vertebrate evolution offers an unusual opportunity to consider computational affordances of a new ecology for the brain. All sensory modalities are changed, particularly a greatly enlarged visual sensorium owing to air versus water as a medium, and expanded by mobile eyes and neck. The multiplication of limbs, as evolved to exploit aspects of life on land, is a comparable computational challenge. As the total mass of living organisms on land is a hundredfold larger than the mass underwater, computational improvements promise great rewards. In water, the midbrain tectum coordinates approach/avoid decisions, contextualized by water flow and by the animal’s body state and learning. On land, the relative motions of sensory surfaces and effectors must be resolved, adding on computational architectures from the dorsal pallium, such as the parietal cortex. For the large-brained and long-living denizens of land, making the right decision when the wrong one means death may be the basis of planning, which allows animals to learn from hypothetical experience before enactment. Integration of value-weighted, memorized panoramas in basal ganglia/frontal cortex circuitry, with allocentric cognitive maps of the hippocampus and its associated cortices becomes a cognitive habit-to-plan transition as substantial as the change in ecology. This article is part of the theme issue ‘Systems neuroscience through the lens of evolutionary theory’. 

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4. The CAFO in the Bioreactor

   https://doi.org/10.1215/22011919-9481440  

   Guthman, Julie (March 2022, Environmental Humanities)

   Abstract A 2020 report published by the think tank RethinkX predicts the “second domestication of plants and animals, the disruption of the cow, and the collapse of industrial livestock farming” by 2035. Although typical of promissory discourses about the future of food, the report gives unusual emphasis to the gains of efficiency and near limitless growth that will come by eradicating confined livestock and aquaculture operations and replacing them with protein engineered at a molecular level and fermented in bioreactors. While there are many reasons to disrupt industrialized livestock production, lack of efficiency is not one of them. This article examines to what extent this so-called second domestication departs from the radical transformations of animal biologies and living conditions to which it responds. Drawing on canonical texts in agrarian political economy, it parses animal bio-industrialization into sets of practices that accelerate productivity, standardize animal life and infrastructures, and reduce risk to maximize efficiency. It shows these practices at work through recent ethnographic accounts of salmon aquaculture and pork production to illustrate how efforts to override temporalities and contain species in unfamiliar habitats, in the name of efficiency, may be the source of vulnerability in such production systems rather than their strength. 

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5. The first day of the Cenozoic

   https://doi.org/10.1073/pnas.1909479116  

   Gulick, Sean P.; Bralower, Timothy J.; Ormö, Jens; Hall, Brendon; Grice, Kliti; Schaefer, Bettina; Lyons, Shelby; Freeman, Katherine H.; Morgan, Joanna V.; Artemieva, Natalia; et al (September 2019, Proceedings of the National Academy of Sciences)

   Highly expanded Cretaceous–Paleogene (K-Pg) boundary section from the Chicxulub peak ring, recovered by International Ocean Discovery Program (IODP)–International Continental Scientific Drilling Program (ICDP) Expedition 364, provides an unprecedented window into the immediate aftermath of the impact. Site M0077 includes ∼130 m of impact melt rock and suevite deposited the first day of the Cenozoic covered by <1 m of micrite-rich carbonate deposited over subsequent weeks to years. We present an interpreted series of events based on analyses of these drill cores. Within minutes of the impact, centrally uplifted basement rock collapsed outward to form a peak ring capped in melt rock. Within tens of minutes, the peak ring was covered in ∼40 m of brecciated impact melt rock and coarse-grained suevite, including clasts possibly generated by melt–water interactions during ocean resurge. Within an hour, resurge crested the peak ring, depositing a 10-m-thick layer of suevite with increased particle roundness and sorting. Within hours, the full resurge deposit formed through settling and seiches, resulting in an 80-m-thick fining-upward, sorted suevite in the flooded crater. Within a day, the reflected rim-wave tsunami reached the crater, depositing a cross-bedded sand-to-fine gravel layer enriched in polycyclic aromatic hydrocarbons overlain by charcoal fragments. Generation of a deep crater open to the ocean allowed rapid flooding and sediment accumulation rates among the highest known in the geologic record. The high-resolution section provides insight into the impact environmental effects, including charcoal as evidence for impact-induced wildfires and a paucity of sulfur-rich evaporites from the target supporting rapid global cooling and darkness as extinction mechanisms. 

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