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Type Ia supernovae are thought to occur in binaries containing a white dwarf and a companion that is a red giant, subgiant, main-sequence star or another white dwarf. In the last of these options, the double-degenerate� case, the two white dwarfs would merge before the explosion and no companion would be left. In a single-degenerate system the former companion star would survive. Previous searches for remnant companions have revealed one contested case for the Tycho Brahe supernova SN 1572. More recently, observations have restricted surviving companions to small, main-sequence stars, ruling out giant companions. Jonay González Hernández et al. report the result of a search for surviving companions to the progenitor of SN 1006 and find no sign of a former companion. Together with previous results, this suggests that fewer than 20% of type Ia supernovae occur through the single-degenerate channel, the slow accumulation of mass from a large star. The more common trigger, it seems, is the rapid break-up of a smaller orbiting white dwarf. The cover shows a composite image of the SN 1006 supernova remnant. A twisting ribbon of light seen by the Hubble Space Telescope reveals where the expanding blast wave is sweeping into the tenuous surrounding gas. (Cover: NASA/CXC/Rutgers/G. Cassam-Chena�, J. Hughes et al.; Radio: NRAO/AUI/NSF/GBT/VLA/Dyer, Maddalena & Cornwell; Optical: Middlebury College/F. Winkler, NOAO/AURA/NSF/CTIO Schmidt & DSS.)
A lack of leadership has hampered progress against global warming. If Barack Obama earns a second term as US president, will he have the energy to tackle climate?
An experiment studying bacterial populations over thousands of generations shows that a novel trait can evolve through rearrangement and amplification of a few pre-existing genes. See Article p.513
Silicon devices form the backbone of modern computers. It turns out that they might also be a natural hardware platform for a new era of computing technology that uses the principles of quantum physics. See Letter p.541
The concept of preferential attachment is behind the hubs and power laws seen in many networks. New results fuel an old debate about its origin, and beg the question of whether it is based on randomness or optimization. See Letter p.537
Simply grabbing an African spiny mouse can cause it to lose up to 60% of the skin on its back. Analysis of the mouse's astounding shedding and healing capacity provides insight into the biomechanics of tissue regeneration. See Letter p.561
Ion gels are composites of ionic liquids and polymers. Free-standing forms of ion gels have now been made that can be neatly cut with a razor blade and stuck onto semiconductor materials to make transistors.
A tightly regulated enzyme balances energy production and the synthesis of macromolecules from glucose in cancer cells. Upsetting this balance by stimulating the enzyme's activity can suppress tumour growth in mice.
By combining full-genome sequencing and ‘evolutionary replay’ experiments to dissect the origin of aerobic citrate use in an experimental Escherichia coli population over 40,000 generations and 2 decades, the authors unveil a 3-step process in which potentiation makes a trait possible, actualization makes the trait manifest and refinement makes it effective.
Comprehensive analyses of 178 lung squamous cell carcinomas by The Cancer Genome Atlas project show that the tumour type is characterized by complex genomic alterations, with statistically recurrent mutations in 11 genes, including TP53 in nearly all samples; a potential therapeutic target is identified in most of the samples studied.
The crystal structure of an influenza antibody that recognizes a small, conserved site in the variable receptor-binding domain of HA is described; this antibody shows broad neutralization across multiple subtypes of influenza A virus through an antibody–antigen interaction dominated by a single heavy-chain complementarity-determining region 3 loop.
A search for a surviving companion star of the progenitor of type Ia supernova 1006 indicates that fewer than 20 per cent of such supernovae result from the accretion onto the progenitor star of material from a companion that survives the process rather than being destroyed.
A framework is developed in which new connections to a growing network optimize geometric trade-offs between popularity and similarity, instead of simply preferring popular nodes; this approach accurately describes the large-scale evolution of various networks.
The coherent manipulation of an individual electron spin qubit bound to a single phosphorus donor atom in natural silicon provides an excellent platform on which to build a scalable quantum computer.
Data are presented that support the idea of an oxygenation event in the immediate aftermath of the Marinoan glaciation, pre-dating previous estimates for post-Marinoan oxygenation by more than 50 million years.
A numerical model of salt marsh evolution shows that competition between mineral sediment deposition and organic matter accumulation determines the net impact of climate change on carbon accumulation in intertidal wetlands.
Delay in the hibernation emergence date of female Columbian ground squirrels in Canada over 20 years is related to climatic conditions other than increasing temperature, and as years of later emergence are associated with decreased individual fitness, plastic responses to climate change may be associated with declines in population viability.
Analyses of strontium elemental and isotopic ratios in fossil teeth show that Australopithecus africanus—the presumed ancestor of early Homo and Paranthropus robustus—had a much more varied diet than Homo and Paranthropus; this sheds light on the diet and home ranges of fossil hominins.
African spiny mice (Acomys) are shown to be capable of regenerating hair follicles, adipose tissue and cartilage, and they can heal deep lesions of skin, with little scarring, suggesting that these mice could prove useful as a model system for studying tissue regeneration in mammals.
The events leading to the generation of broadly neutralizing antibodies to influenza viruses, which may hold the key to developing a universal flu vaccine, are elucidated.
The function of haematopoietic stem and progenitor cells is impaired by damaged DNA; here, endogenously generated aldehydes are found to be one source of such damage, which is repaired by the Fanconi anaemia pathway.
Nucleolytic degradation of 5′ strands at DNA double-strand breaks in yeast is shown to be facilitated by the nucleosome remodeller Fun30, particularly within chromatin bound by the checkpoint adaptor protein known to inhibit resection, Rad9.
Fun30 and SMARCAD1 are identified as chromatin remodellers that promote DNA end resection during DNA repair and preserve genome stability in yeast and humans, respectively.
A survey of 1,590 putative integral, peripheral and lipid-anchored membrane proteins from Saccharomyces cerevisiae reveals unexpected physical associations underlying the membrane biology of eukaryotes and delineates the global topological landscape of the membrane interactome.
COPD is one of the world's biggest killers, but awareness is low, diagnosis is often missed, and in many countries the extent of the problem is not even well-documented.
Researchers are counting on drugs that activate a master switch for antioxidant genes to protect lung tissue of COPD patients from an onslaught of free radicals.
The first symptoms of COPD can be subtle, so the disease often goes undiagnosed. Researchers are searching for ways to detect the disease and to identify those most at risk.
Many COPD patients are deficient in vitamin D, a condition that can lead to bone problems as well as difficulty breathing. Can dietary supplements be of help?
The donor lungs of the future — built from collagen or silicone rubber or engineered from donor organs stripped of their original cells — might give a new lease of life to COPD patients.
Air pollution and smoking have made COPD a major problem in China, now compounded by outdated diagnostics and treatments — and experts say it's bound to get worse.
Chronic obstructive pulmonary disease (COPD) robs tens of millions of people of the ability to easily draw in the air they need to live a normal life. Although this incurable, progressive condition is difficult to diagnose, a bevy of new treatment options — including drug combinations, artificial lungs and dietary supplements — could give COPD patients a breath of fresh air.