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The heat wave that struck Greenland in July 2012 melted surface ice across virtually the entire ice sheet, causing extensive flooding. Ice core data suggest that such events occur only about once every 150 years on average, with the last one in 1889. Ralf Bennartz and colleagues have examined the physical mechanisms behind the 2012 event. At high elevations thin liquid-bearing clouds had an important role in enhancing surface warming, as they were optically thick enough and low enough to significantly enhance the downwelling infrared flux at the surface. At the same time they were thin enough to allow sufficient solar radiation through to raise surface temperatures above the melting point. The cover shows formations known as fog bows, or cloud bows, over the NSF mobile laboratory at Summit Station, Greenland. Fog bows are similar to rainbows but less colourful as they are caused by smaller liquid water droplets. Cover photo by Dr. Brant Miller, University of Idaho, taken in July 2012.
Japan’s major science-funding agency has a clean record when it comes to research fraud. Now is the time for it to step up and resolve a long-running case of alleged scientific misconduct.
The week in science: Canada leaves UN desertification treaty, China reports first human deaths from H7N9 bird flu, and UK open-access policies take effect.
Biosynthesis of the antibiotic fosfomycin ends with the formation of an 'epoxide' ring structure. The epoxide is suggested to form from a cationic intermediate, rather than from a free radical. See Letter p.114
The tectonic history of western North America is a puzzle in which many of the pieces are mashed up or missing. Seismic images of the deep Earth reveal features that alter our reconstruction of this puzzle in space and time. See Article p.50
A clever combination of existing techniques has produced three-dimensional atomic images of individual platinum nanoparticles, disclosing the atomic structure of crystal defects within them. See Letter p.74
Mutations in the enzyme isocitrate dehydrogenase lead to the accumulation of a metabolite that seems to promote cancer by influencing the epigenetic status of cells. But the effects are reversible, hinting at therapeutic targets.
Moving beyond mimicry, biologically inspired artificial materials can be simpler in design yet more powerful in function than their natural analogues. A tropical fruit seed serves as a guide to making new photonic elements.
It emerges that the sirtuin enzyme SIRT6 preferentially removes long-chain fatty-acyl, rather than acetyl, protein modifications. This activity regulates secretion of the inflammation-associated protein TNF-α. See Letter p.110
A synthesis of geochemical proxy records of sea surface temperature shows that the early Pliocene climate was little different from today in terms of maximum ocean temperatures but had substantially lower meridional and zonal temperature gradients.
A new explanation for the origin of the accreted terranes that form the mountainous Cordillera of western North America is proposed and tested: stationary, intra-oceanic subduction deposited massive slab walls in the mantle and grew volcanic archipelagos at the surface, which were overridden by and accreted to North America during Cretaceous times.
Genome sequences of human-infective tapeworm species reveal extreme losses of genes and pathways that are ubiquitous in other animals, species-specific expansions of non-canonical heat shock proteins and families of known antigens, specialized detoxification pathways, and metabolism that relies on host nutrients; this information is used to identify new potential drug targets.
Crystal structures of mammalian CRY2, one of the cryptochrome flavoproteins that have light-independent functions at the core of the circadian clock, show that it binds FAD dynamically and that the F-box protein FBXL3 captures CRY2 by occupying its FAD-binding pocket and burying its PER-binding interface.
Magnetic order in a manganite can be switched during femtosecond photo-excitation via coherent superpositions of quantum states; this is analogous to processes in femtosecond chemistry where photoproducts of chemical and biochemical reactions can be influenced by creating suitable superpositions of molecular states.
A new combination of established techniques is used to produce three-dimensional (3D) images and a video of almost all the atoms in a platinum nanoparticle, revealing the 3D core structure of edge and screw dislocations and 3D twin boundaries in the nanoparticle at atomic resolution.
Aluminium catalyst is trapped during growth of a silicon nanowire from vapour phase at concentrations vastly beyond equilibrium solid solubility, but is homogeneously distributed as atoms and not found as clusters or precipitates; this is a potential route to tailoring the composition and properties of nanowires.
In July 2012, a heat wave swept across Greenland, resulting in extensive melting of surface ice and flooding; this is shown to have been enhanced by liquid clouds forming in such a way that sufficient incoming shortwave radiation could penetrate to the surface while downwelling longwave radiation increased.
The genome sequence and its analysis of the diploid wild wheat Triticum urartu (progenitor of the wheat A genome) represent a tool for studying the complex, polyploid wheat genomes and should be a valuable resource for the genetic improvement of wheat.
Sequencing and analysing the diploid genome and transcriptome of Aegilops tauschii provide new insights into the role of this genome in enabling the adaptation of bread wheat and are a step towards understanding the very large and complicated hexaploid genomes of wheat species.
A study of mouse visual cortex relating patterns of excitatory synaptic connectivity to visual response properties of neighbouring neurons shows that, after eye opening, local connectivity reorganizes extensively: more connections form selectively between neurons with similar visual responses and connections are eliminated between visually unresponsive neurons, but the overall connectivity rate does not change.
Pancreatic cancers use a novel glutamine metabolism pathway, regulated by oncogenic KRAS, to maintain redox balance; these findings add to the understanding of the mechanisms by which oncogenic alterations reprogram cellular metabolism to promote tumour growth.
An irreversible mechanism of protein demyristoylation catalysed by invasion plasmid antigen J (IpaJ), a Shigella flexneri type III effector protein with cysteine protease activity, is described.
The sirtuin family of enzymes are known as NAD-dependent deacetylases, although some of them have very weak deacetylase activity; here human SIRT6, an enzyme important for DNA repair and transcription, is shown to remove long-chain fatty acyl groups from protein lysine residues, and to have a function in promoting tumour necrosis factor alpha secretion.
The non-haem-iron-dependent enzyme HppE catalyses the final step in the biosynthesis of fosfomycin, a broad-spectrum, clinically useful antibiotic; here it is shown that HppE can also catalyse a 1,2-phosphono-migration reaction, previously undocumented for any enzyme.
During chromosome replication, coupled polymerases introduce topological changes that cause lower processivity and transient lagging-strand polymerase dissociation from DNA.
Structures of a newly characterized three-domain haem-c-Cu nitrite reductase are reported at 1.01 Å resolution, indicating how electron transfer may occur in protein–protein complexes.