Research articles

Human-induced climate change is usually assumed to be responsible for the dramatic thawing of glaciers since the mid 1990s in Greenland and northeastern Canada; approximately half of the observed warming in this region during this period is now found to be attributable to atmospheric circulation changes that may be of natural origin.

Femtosecond resolution X-ray fluorescence spectroscopy is shown to track the charge and spin dynamics triggered when an iron coordination complex is excited by light, and establishes the critical role of intermediate spin states in the de-excitation process.

The largest assemblage so far of published data shows that C₃ crops have decreased zinc and iron levels under CO₂ conditions predicted for the middle of this century, with worldwide nutritional implications.

The transition between ‘static’ and ‘dynamic’ friction in a model system is found to be quantitatively captured by the same theoretical framework as is used to describe brittle fracture, but deviations from this correspondence are observed as the rupture velocity approaches the speed at which sound waves propagate along the interface.

Triphosphates of hydrophobic nucleotides d5SICS and dNaM are imported into Escherichia coli by an exogenous algal nucleotide triphosphate transporter and then used by an endogenous polymerase to replicate, and faithfully maintain over many generations of growth, a plasmid containing the d5SICS–dNaM unnatural base pair.

A simulation that starts 12 million years after the Big Bang and traces 13 billion years of cosmic evolution yields a reasonable population of elliptical and spiral galaxies, reproduces the observed distribution of galaxies in clusters and the characteristics of hydrogen on large scales, and at the same time matches the ‘metal’ and hydrogen content of galaxies on small scales.

Field experiments across aquatic and terrestrial ecosystems show that biodiversity positively affects carbon and nitrogen cycling in leaf litter decomposition, indicating that reduced decomposition caused by biodiversity loss would modify the global carbon cycle and limit the nitrogen supply to the organisms at the base of the food chain.

The molecular basis for mating-type determination in the ciliate Paramecium has been elucidated, revealing a novel function for a class of small RNAs — these scnRNAs are typically involved in reprogramming the Paramecium genome during sexual reproduction by recognizing and excising transposable elements, but they are now found to be co-opted to switch off expression of the newly identified mating-type gene mtA by excising its promoter, and to mediate epigenetic inheritance of mating types across sexual generations.

For the first time under reproducible and fully double-blinded conditions, it is shown that anthropogenic electromagnetic noise below the WHO limits affects a biological system: night-migrating birds lose the ability to use the Earth’s magnetic field for orientation when exposed to anthropogenic electromagnetic noise at strengths routinely produced by commonly used electronic devices.

Precipitation is expected to increase far more over the twenty-first century in the Arctic than the global average; climate models show that this is driven mainly by increased local evaporation and sea-ice retreat, rather than by increased moisture transport from lower latitudes.

Whether or not endogenous c-kit⁺cells residing within the heart contribute cardiomyocytes during physiological ageing or after injury remains unknown; here, using an inducible lineage tracing system, the c-kit⁺lineage is shown to generate cardiomyocytes at very low levels, and, by contrast, contributes substantially to cardiac endothelial cell generation.

Clonal expansion and hypermutation of B cells in the germinal centre are regulated by the amount of antigen that the B cells present to follicular helper T cells.

Inhibitory neuron activity is found to be relatively stable during motor learning whereas excitatory neuron activity is much more dynamic — the results indicate that a large number of neurons exhibit activity changes early on during motor learning, but this population is refined with subsequent practice.

A mouse model of T-cell leukaemia is used to test whether PTEN loss is required for tumour maintenance as well as initiation; although it had little effect on tumour load in haematopoietic organs, PTEN reactivation reduced the CCR9-dependent tumour dissemination to the intestine that was amplified on PTEN loss, exposing the importance of tumour microenvironment in PTEN-deficient settings.

This study shows how the yeast Ctf4 protein couples the DNA helicase, Cdc45–MCM–GINS, to DNA polymerase α — the GINS subunit of the helicase and the polymerase use a similar interaction to bind Ctf4, suggesting that, as Ctf4 is a trimer, two polymerases could be simultaneously coupled to a single helicase during lagging-strand synthesis.

A metabolomics quantification of NADPH production and consumption fluxes in proliferating mammalian cells reveals that, in addition to canonical pathways such as the oxidative pentose phosphate pathway, NADPH can also be produced by a folate metabolism pathway, a discovery providing new insights into the metabolism of cell growth.

Motion detection by the retina is thought to rely largely on the biophysics of starburst amacrine cell dendrites; here machine learning is used with gamified crowdsourcing to draw the wiring diagram involving amacrine and bipolar cells to identify a plausible circuit mechanism for direction selectivity; the model suggests similarities between mammalian and insect vision.

Near-infrared spectroscopic observations of the young extrasolar planet β Pictoris b indicate that it spins significantly faster than any planet in the Solar System, in line with the extrapolation of the known trend in spin velocity with planet mass.

Single organic dye molecules have high-flux, narrow-bandwidth single-photon emission and can be spectrally matched to the transitions of atoms acting as a quantum memory, making them promising for use in quantum information and communication schemes.

Regeneration of the heart muscle after myocardial infarction with cardiomyocytes derived from human embryonic stem cells is demonstrated in non-human primates, with the grafts showing evidence of electromechanical coupling, although they were also associated with non-fatal arrhythmias.