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    Brain states behind exploring and hunting revealed

    Internal brain states modulate how we perceive, feel about and respond to the stimuli around us. The neurons and networks that encode these various states remain mysterious, owing to the brain’s enormous complexity. As a result, researchers have only a vague sense of how animals, including humans, use recent experience and context to select appropriate behaviours. Writing in Nature, Marques et al.1 perform a first-of-its-kind exploration of brain-wide activity in zebrafish larvae as the animals encounter a classic state-driven behavioural choice: whether to explore their environment or to exploit resources in the local area. By monitoring individual neurons across the brain as these decisions play out, the authors open a…

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    Long-term predator–prey cycles finally achieved in the lab

    A key question in ecology is what allows species to persist over time — particularly when there are pairs of species in which one is an exploiter and the other its victim. A long-standing theory attempts to answer this question by explaining how relative numbers of predators and their prey can cycle continuously1. First, prey numbers would increase, giving the predator more food. The subsequent increase in predators would lead to a decline in prey. Predator numbers would then decline owing to a lack of food, restarting the cycle. However, it has proved unexpectedly challenging to demonstrate this type of persistent predator–prey cycle in simple controlled systems in the laboratory.…

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    Magnetic and topological order united in a crystal

    An ordered arrangement of magnetic moments in a material normally prevents the formation of another kind of electronic order associated with an exotic state of matter known as a topological insulator. But Otrokov et al.1 and Rienks et al.2 report in Nature that manganese bismuth telluride integrates these two types of electronic behaviour. The complex layered structure of alternating magnetic and topologically non-trivial regions in this material leads to an intriguing and potentially technologically useful interplay between magnetic and topological order.

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    Daily briefing: Why is ice so slippery?

    It’s time for the hotly anticipated Nature’s 10 — our annual list of ten people who mattered in science this year. They might have achieved amazing discoveries, brought attention to crucial issues or even gained notoriety for controversial actions. This year’s selection includes Brazil’s science defender, a quantum-computer builder and a fossil hunter who revealed the face of an ancient human relative.

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    The science news events that shaped 2019

    This year, astronomers glimpsed the blackness of a black hole for the first time ever. In April, the international Event Horizon Telescope collaboration unveiled perhaps the most memorable picture of 2019: the first direct image of a black hole and its event horizon. To produce it, researchers coaxed a network of radio telescopes to take simultaneous readings from around Earth.

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    The scientific events that shaped the 2010s

    Scientific and technological innovation has always created social and economic transformation. But the past decade showed, as few others have, the speed and scale at which such change can happen. If it continues at the present rate, the shape of the next ten years — from information technologies to applied bioscience, energy and environment — looks ever more contingent on the discoveries made in that time.

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    We need a science of the night

    This week, as the Northern Hemisphere has its longest night, my thoughts turn to the 4,300 dark hours in a year. My interest in cities after hours began a decade ago with a project on the economy of waste that saw me riding in rubbish lorries in London, Singapore and Sydney, Australia, often between 11 p.m. and 5 a.m. After being steeped in ‘global city’ research, spending time with refuse collectors showed me a new world of office cleaners, health-care workers, mammoth restricted-hour lorries, sex workers and homeless people.