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A possible direct exposure of the Earth to the cold dense interstellar medium 2–3 Myr ago

Cold, dense clouds in the interstellar medium of our Galaxy are 4–5 orders of magnitude denser than their diffuse counterparts. Our Solar System has most likely encountered at least one of these dense clouds during its lifetime. However, evidence for such an encounter has not been studied in detail yet. Here we derive the velocity field of the Local Ribbon of Cold Clouds (LRCC) by modelling the 21 cm data from the HI4PI survey, finding that the Solar System may have passed through the LRCC in the constellation Lynx 2–3 million years ago. Using a state-of-the-art simulation of the heliosphere, we show that during the passage, the heliosphere shrinks to a scale of 0.22 au, smaller than the Earth’s orbit around the Sun. This would have put the Earth in direct contact with the dense interstellar medium for a period of time and exposed it to a neutral hydrogen density above 3,000 cm−3. Such a scenario agrees with geological evidence from 60Fe

3D Printing News Briefs, May 25, 2024: 3D Printed Medical Models, Sensors, Engines, & More - 3DPrint.com | The Voice of 3D Printing / Additive Manufacturing

Mapping model units to visual neurons reveals population code for social behaviour

The rich variety of behaviours observed in animals arises through the interplay between sensory processing and motor control. To understand these sensorimotor transformations, it is useful to build models that predict not only neural responses to sensory input1–5 but also how each neuron causally contributes to behaviour6,7. Here we demonstrate a novel modelling approach to identify a one-to-one mapping between internal units in a deep neural network and real neurons by predicting the behavioural changes that arise from systematic perturbations of more than a dozen neuronal cell types. A key ingredient that we introduce is ‘knockout training’, which involves perturbing the network during training to match the perturbations of the real neurons during behavioural experiments. We apply this approach to model the sensorimotor transformations of Drosophila melanogaster males during a complex, visually guided social behaviour8–11. The visual projection neurons at the

Life-cycle-coupled evolution of mitosis in close relatives of animals

Eukaryotes have evolved towards one of two extremes along a spectrum of strategies for remodelling the nuclear envelope during cell division: disassembling the nuclear envelope in an open mitosis or constructing an intranuclear spindle in a closed mitosis1,2. Both classes of mitotic remodelling involve key differences in the core division machinery but the evolutionary reasons for adopting a specific mechanism are unclear. Here we use an integrated comparative genomics and ultrastructural imaging approach to investigate mitotic strategies in Ichthyosporea, close relatives of animals and fungi. We show that species in this clade have diverged towards either a fungal-like closed mitosis or an animal-like open mitosis, probably to support distinct multinucleated or uninucleated states. Our results indicate that multinucleated life cycles favour the evolution of closed mitosis. We analyse cell division in ichthyosporeans and find that multinucleated life cycles favour the evolution of clos

Arresting failure propagation in buildings through collapse isolation