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Many systems respond impulsively to slowly increasing external stresses. Normally smooth processes of stress release can be disrupted intermittently by large random events (or avalanches), such that a system undergoes abrupt structural changes. Using a combination of theory and experiment in a model system consisting of nickel microcrystals under compression, Stefanos Papanikolaou and colleagues investigate an intermediate regime in which the smooth background processes occur at similar rates to the external driving stresses, leading to the unusual observation of themselves. This finding is, in principle, applicable to all intermittent phenomena with coexisting slow relaxations that compete to minimize the local internal stress. This description would include complex networks � such as the brain � during relaxation, disordered/jammed solids and earthquake faults, forcing a re-interpretation of experimental and simulation data. The cover shows a nickel microcrystal array with an overlay outline of the San Andreas Fault, where the forces observed in the microcrystals act on a larger scale. (Array by Dennis M. Dimiduk/ fault by D K Lynch/ USGS)
Moves towards a global water commodities market must be stopped. It will push the price of food far beyond the peaks of the past five years, warns Frederick Kaufman.
The identification of a signalling protein that regulates the accumulation of fat and connective tissue in breasts may help to explain why high mammographic density is linked to breast-cancer risk. It may also provide a marker for predicting this risk.
The finding that pools of gas hydrates — compounds that trap natural gas emissions — in ocean sediments are deeper than expected implies that the hydrates are destabilizing, and might release gigatonnes of methane. See Letter p.527
Developing therapeutic drugs that target peptide receptors is challenging. The structure of one of these G-protein-coupled receptors, NTS1, activated and bound to a peptide, provides an excellent starting point. See Article p.508
A quantitative analysis shows that epistasis — the fact that genetic background determines whether a mutation is beneficial, deleterious or inconsequential — is the main factor regulating evolution at the level of proteins. See Letter p.535
An explanation has been proposed for the observed excess of cosmic light at infrared wavelengths. It invokes stars that are cast into the dark-matter haloes of their parent galaxies during powerful galaxy collisions. See Letter p.514
Whole-genome sequences of wild rice and cultivated rice varieties are used to produce a map of rice genome variation, and show that rice was probably first domesticated in southern China.
The roles of BATF transcription factors in dendritic cell differentiation are studied, providing evidence for molecular compensation by related family members; compensation is based on the interaction of the BATF leucine zipper domains with IRF factors to mediate cooperative gene activation.
The X-ray crystal structure of a rat neurotensin receptor in complex with the C-terminal portion of neurotensin is presented; this is the first structure of a member of the β group of class A G-protein-coupled receptors.
Measurements of the anisotropy power spectrum of the cosmic near-infrared background radiation show the clustering amplitude to be larger than existing model predictions involving distant primordial galaxies or nearby faint galaxies: the fluctuations are proposed to originate from intrahalo stars of all galaxies with dark-matter haloes of 109 to 1012 solar masses at redshifts of about 1 to 4.
A crystalline material is investigated that responds to a slowly increasing external stress by exhibiting impulsive ‘avalanche’ behaviour as well as smooth stress release that is approximately as slow as the external stress rate; unusual oscillatory behaviour in the avalanche time series is reported.
The synthesis of an all-carbon quaternary stereocentre in an acyclic system is reported; the chemical transformation involves the formation of two new stereogenic centres—including the challenging all-carbon quaternary one in an aldol adduct—via a combined carbometalation–oxidation reaction, giving a stereodefined trisubstituted enolate.
Seismic data and modelling are used to reveal clathrate destabilization along the eastern margin of the United States; the destabilization is probably linked to warming, or a slight shift, in the Gulf Stream.
The solubility of argon in lower mantle minerals is shown to be much higher than for xenon, so that the depletion of xenon relative to argon in Earth’s atmosphere can be explained by mantle degassing.
A comparison of more than 1,000 orthologues of diverse proteins shows that the rate of amino-acid substitution in recent evolution is an order of magnitude lower than that expected in the absence of epistasis, indicating that epistasis is pervasive throughout protein evolution.
The pleiotropic transcription factor IRF4 is shown to regulate CD4+ T-cell differentiation and TH17 function through cooperative binding interactions with BATF and JUN family proteins via AP1–IRF4 composite elements (AICEs).
In a Drosophila imaginal epithelial disc system, mutations that lead to mitochondrial dysfunction can also promote tumorigenic growth of neighbouring cells expressing an activated Ras oncogene.
A new class of peptides, mambalgins, is isolated from the African snake the black mamba, which can abolish pain through inhibition of particular subtypes of acid-sensing ion channels expressed either in central or peripheral neurons.
Protein–protein interactions, essential for understanding how a cell functions, are predicted using a new method that combines protein structure with other computationally and experimentally derived clues.
Immunoglobulin genes are expressed from either the maternal or paternal chromosome; it is now shown that in early haematopoietic stem cells, an individual cell can choose either of the two alleles, but as they develop they become committed to only one.
Biochemical and structural analysis of the drug transporter P-glycoprotein in Caenorhabditis elegans at a resolution of 3.4 angstroms is used to generate a homology model of the human protein and supports a picture in which P-glycoprotein uses the energy from ATP hydrolysis to expel lipophilic molecules from the inner leaflet of the cell membrane.