Beijing 2022: Olympics will make water scarcity worse

Nature 525, 7570 (2015). doi:10.1038/525455e

Authors: Hong Yang, Julian R. Thompson & Roger J. Flower

The 2022 Winter Olympics in Beijing threaten to seriously exacerbate water shortages in the area, where the available water per person is already only about 3% of the world's average (see also Nature524, 278–279;10.1038/nature.2015.181742015).The Winter Olympics

Creative writing: A world of pure imagination

Nature 525, 7570 (2015). doi:10.1038/nj7570-553a

Author: Roberta Kwok

The creative process of writing science-inspired fiction can be rewarding — and the untapped niche is rich in opportunities for originality.

Trade talk: Medical liaison

Nature 525, 7570 (2015). doi:10.1038/nj7570-555a

Author: Monya Baker

David Crosby describes how he moved from basic research to doing outreach to healthcare providers.

Coin-operated dancer

Nature 525, 7570 (2015). doi:10.1038/525558a

Author: James Reinebold

The show must go on.

Cannabis

Nature. doi:10.1038/525S1a

Author: Michelle Grayson

The cannabis crop

Nature. doi:10.1038/525S2a

Author: Julie Gould

Cannabis is one of humanity's oldest cultivated crops. But despite its long history and many uses, hard facts on its evolution and impact on the human body are in short supply. By Julie Gould.

Botany: The cultivation of weed

Nature. doi:10.1038/525S4a

Author: Lucas Laursen

Researchers are getting closer to answering the centuries-old question of how to label cannabis varieties — a necessary step to bring the plant into mainstream agriculture.

Drug development: The treasure chest

Nature. doi:10.1038/525S6a

Author: Brian Owens

Pharmaceutical research into the chemicals found in cannabis has so far supplied only one licensed medicine. But scientists think there could be hundreds more.

Perspective: Close the knowledge gap

Nature. doi:10.1038/525S9a

Authors: Jonathan Page & Mark Ware

Nations with cannabis programmes should respond to a lack of research. Canada can be a leader, say Jonathan Page and Mark Ware.

A potted history

Nature. doi:10.1038/525S10a

Author: Stephanie Pain

For thousands of years cannabis has been valued as a versatile herbal medicine. In the twentieth century, prescription gave way to proscription. Might this ancient remedy be about to regain its healing reputation? By Stephanie Pain

Israel: Research without prejudice

Nature. doi:10.1038/525S12a

Author: Emily Sohn

How one Mediterranean country is pushing the frontiers of medical cannabis knowledge.

Perspective: Be clear about the real risks

Nature. doi:10.1038/525S14a

Author: Matthew Hill

The assertion that cannabis use can cause schizophrenia is not borne out by the evidence, says Matthew Hill.

Medical marijuana: Showdown at the cannabis corral

Nature. doi:10.1038/525S15a

Author: Michael Eisenstein

Researchers are gathering clinical data for medical marijuana against a backdrop of deregulation and opportunism.

Cannabis: 4 big questions

Nature. doi:10.1038/525S18a

Author: Julie Gould

As restrictions around cannabis research ease, scientists are exploring how the plant could be medically useful. Here are four of the hardest questions they face.

Marine science: Storms bring ocean nutrients to light

Nature 525, 7570 (2015). doi:10.1038/525460a

Authors: Jaime Palter

Ships and ocean-observing robots have been used to quantify the amount of nutrients that a storm brings up from the Stygian ocean depths to the sunlit surface — a first step in assessing how storms affect oceanic biomass production.

Nuclear physics: Neutrons with a twist

Nature 525, 7570 (2015). doi:10.1038/525462a

Authors: Robert W. Boyd

Neutrons do not normally have orbital angular momentum. But the demonstration that a beam of neutrons can acquire this property, 23 years after it was shown in photons, offers the promise of improved imaging technologies. See Letter p.504

Evolutionary biology: Infection elevates diversity

Nature 525, 7570 (2015). doi:10.1038/525464a

Authors: Aneil F. Agrawal

Chromosomal shuffling in parental eggs or sperm can create new characteristics in the next generation. In fruit flies, it seems that mothers with a parasitic infection produce more such recombinant offspring than uninfected mothers.

Computational astrophysics: Monstrous galaxies unmasked

Nature 525, 7570 (2015). doi:10.1038/525465a

Authors: Romeel Davé

The enigma of how the most luminous galaxies arise is closer to being solved. New simulations show that these are long-lived massive galaxies powered by prodigious gas infall and the recycling of supernova-driven outflows. See Letter p.496

Hallmarks of pluripotency

Nature 525, 7570 (2015). doi:10.1038/nature15515

Authors: Alejandro De Los Angeles, Francesco Ferrari, Ruibin Xi, Yuko Fujiwara, Nissim Benvenisty, Hongkui Deng, Konrad Hochedlinger, Rudolf Jaenisch, Soohyun Lee, Harry G. Leitch, M. William Lensch, Ernesto Lujan, Duanqing Pei, Janet Rossant, Marius Wernig, Peter J. Park & George Q. Daley

Stem cells self-renew and generate specialized progeny through differentiation, but vary in the range of cells and tissues they generate, a property called developmental potency. Pluripotent stem cells produce all cells of an organism, while multipotent or unipotent stem cells regenerate only specific lineages or tissues. Defining stem-cell potency relies upon functional assays and diagnostic transcriptional, epigenetic and metabolic states. Here we describe functional and molecular hallmarks of pluripotent stem cells, propose a checklist for their evaluation, and illustrate how forensic genomics can validate their provenance.

The formation of submillimetre-bright galaxies from gas infall over a billion years

Nature 525, 7570 (2015). doi:10.1038/nature15383

Authors: Desika Narayanan, Matthew Turk, Robert Feldmann, Thomas Robitaille, Philip Hopkins, Robert Thompson, Christopher Hayward, David Ball, Claude-André Faucher-Giguère & Dušan Kereš

Submillimetre-bright galaxies at high redshift are the most luminous, heavily star-forming galaxies in the Universe and are characterized by prodigious emission in the far-infrared, with a flux of at least five millijanskys at a wavelength of 850 micrometres. They reside in haloes with masses about 1013 times that of the Sun, have low gas fractions compared to main-sequence disks at a comparable redshift, trace complex environments and are not easily observable at optical wavelengths. Their physical origin remains unclear. Simulations have been able to form galaxies with the requisite luminosities, but have otherwise been unable to simultaneously match the stellar masses, star formation rates, gas fractions and environments. Here we report a cosmological hydrodynamic galaxy formation simulation that is able to form a submillimetre galaxy that simultaneously satisfies the broad range of observed physical constraints. We find that groups of galaxies residing in massive dark matter haloes have increasing rates of star formation that peak at collective rates of about 500–1,000 solar masses per year at redshifts of two to three, by which time the interstellar medium is sufficiently enriched with metals that the region may be observed as a submillimetre-selected system. The intense star formation rates are fuelled in part by the infall of a reservoir gas supply enabled by stellar feedback at earlier times, not through major mergers. With a lifetime of nearly a billion years, our simulations show that the submillimetre-bright phase of high-redshift galaxies is prolonged and associated with significant mass buildup in early-Universe proto-clusters, and that many submillimetre-bright galaxies are composed of numerous unresolved components (for which there is some observational evidence).