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A search of a data set of light curves for 247,000 known, spectroscopically confirmed quasars with a temporal baseline of about 9 years reveals a strong, smooth periodic signal in the optical variability of quasar PG 1302−102 with a mean observed period of 1,884 ± 88 days, indicating a possible supermassive black-hole binary.
Alexander D. Gitlin and Michel C. Nussenzweig reflect on the discovery of two lineages of adaptive immune cells, and how it influenced vaccination, cancer therapy and the development of a class of antibody-based drugs.
Traditionally, the vertebral column of snakes was thought to have lost regionalization; Hox regionalization is now shown to be maintained in snakes, suggesting that gradational vertebral column regionalization is primitive to amniotes.
Meiotic recombination is initiated by a fairly uniform distribution of hundreds of DNA double-strand breaks catalysed by the Spo11 protein; here, Tel1 (orthologue of human ATM) is shown to be required for the localized inhibition that prevents double-strand breaks from forming close to one another.
Defined skin commensal bacteria elicit a dermal dendritic-cell-dependent, long-lasting, commensal-specific CD8+ T-cell response that promotes protection against pathogens while preserving tissue homeostasis.
The measurement of the rotational periods of 30 cool stars in the 2.5-billion-year-old cluster NGC 6819 allows the calibration of gyrochronology — the determination of a star’s age on the basis of its rotation period — over a much broader age range than hitherto, meaning that it might be possible to determine the ages of many cool stars in the Galactic field with a precision of roughly 10 per cent.