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Sergei Skripal and his daughter were poisoned with a Novichok nerve agent in Salisbury, UK, last year.Credit: Matt Cardy/Getty

The group of nerve agents known as Novichoks is to be added to the Organisation for the Prohibition of Chemical Weapons (OPCW) list of banned substances. The compounds were used in a high-profile assassination attempt on a former Russian military officer in the United Kingdom last year, which killed another person. Novichoks were already implicitly forbidden by the convention, which covers any chemical used as a weapon, but the explicit ban will help the OPCW keep tabs on these chemicals and their precursors.

Nature | 3 min read

Researchers who observed a two-body star system over two years realized that one companion could only be a black hole 68 times more massive than the Sun. The problem: such a thing shouldn’t exist. Heavyweight black holes have been spotted at the centres of galaxies, but current theory says that those that form in the aftermath of a supernova explosion should grow no bigger than around 55 solar masses. Astrophysicists note that extraordinary claims require extraordinary evidence. “I remain skeptical, but I’m just a theorist,” says astrophysicist Stan Woosley. “Observations rule.”

Sky & Telescope | 8 min read

Reference: Nature paper

Biochemists have found a compound that lowers the defences of drug-resistant strains of the bacterium Staphylococcus aureus — the leading cause of infections worldwide. Researchers screened around 45,000 candidates before alighting on MAC-545496, which shows promise against MRSA (methicillin-resistant S. aureus) in lab tests. Rather than acting as an antibiotic itself, MAC-545496 makes MRSA more vulnerable to attack by the immune system, and weakens its resistance to existing drugs.

Forbes | 5 min read

Reference: Nature Chemical Biology paper

Features & opinion

Long-term functional imaging of an entire Drosophila embryo, captured using light-sheet microscopy.Credit: Raghav Chhetri and Philipp Keller/HHMI, Janelia Research Campus

Microscopy has been a trade-off until now: the bigger the sample, the lower the resolution. But picking out cellular detail in whole mouse brains and more is becoming increasingly possible, thanks to the microscope makers putting ever-larger biological samples under the spotlight.

Nature | 11 min read

In terms of improving public health, vaccination is second only to providing clean drinking water. Yet vaccination rates are falling in high-income countries where the toll of disease is less visible — motivating some regions to impose mandatory vaccination. Public-health experts examine the evidence and find that investing in information campaigns and making access easier can inspire higher vaccination rates without compulsion.

Nature | 10 min read

This article is part of Nature Outlook: Vaccines, an editorially independent supplement produced with financial support from GSK.

Measles 90,000 The number of cases of measles in Europe during the first half of this year — more than 17 times the number reported in the whole of 2016.

The results of Nature’s 2019 PhD survey are in. Chief careers editor David Payne tells the Nature Podcast about the highs and lows reported by more than 6,000 graduate students from around the world. They tell a story of personal reward and resilience against a backdrop of stress, uncertainty and struggles with depression and anxiety.

Nature Podcast | 25 min listen

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Books & culture

Barbara Kiser’s pick of the top five science books to read this week includes the truth in Moby-Dick, what makes science trustworthy, and the board game that won a war.

Nature | 2 min read

Infographic of the week