Articles in 2011

It has been suggested that the Cambrian ocean was oxygen deficient, but physical evidence for widespread anoxia has been lacking. Now, sulphur isotope data from Cambrian rocks at six different locations around the world is presented, with the finding of a positive sulphur isotope excursion in phase with a large excursion in the marine carbon isotope record, which is thought to be indicative of a global carbon cycle perturbation at the time. With the help of a box model, these isotope shifts support the idea of large-scale anoxic and sulphidic conditions in the later Cambrian ocean.

In the past two decades, the green-chemistry movement has helped industry become much cleaner. But mindsets change slowly, and the revolution still has a long way to go.

Researchers have spent 25 years exploring the remarkable properties of fullerenes, carbon nanotubes and graphene. But commercializing them is neither quick nor easy.

More than ever before, new techniques show the bond to be a convenient fiction, albeit one that holds the field of chemistry together, finds Philip Ball.

Müllerian mimics have convergently evolved similar warning colouration because of the advantage of strength in numbers. However, it is not clear if this effect is sufficient to maintain coexistence when competitive exclusion would be expected to favour one mimic at the expense of the others. Here, Müllerian mimicry in catfish is characterized, and it is shown through morphometric and stable isotope analysis that mimics do not occupy identical niches, so are not in direct competition, thus explaining their coexistence.

Single-atom-thick graphene sheets can be produced at metre scales, bringing large-area applications in electronics and photovoltaics closer. However, such large pieces can be expected to be polycrystalline, so that it is important to determine the nature and size of grains in large-area graphene. This paper uses a combination of old and new transmission electron microscope techniques to carry out atomic-resolution imaging at grain boundaries as well as mapping of the location, orientation and shape of several hundred grains and boundaries with diffraction-filtered imaging. By correlating grain imaging with scanned probe and transport measurements, it is shown that the grain boundaries dramatically weaken the mechanical strength of graphene membranes, but do not as dramatically alter their electrical properties.

Nitrogen-fixing rhizobia use lipochitooligosaccharide (LCO) signal molecules to initiate a symbiotic relationship with plant roots. Although it has been suggested that mycorrhizal fungi also secrete chemical signals for this process, the identity of these molecules was unknown. It is now shown that like rhizobia, mycorrhizal fungi produce LCOs and that these molecules are important for the establishment of the symbiotic relationship between plant root and fungus.

A string of new laws and a presidential power grab unsettle researchers in Venezuela.

Spending cuts and political battles loom on the horizon.

Undermining belief in a fair world may mean that climate warnings go unheeded.

Bart Gordon reflects on his career at the sharp end of science politics.

Tunicates are the closest living relatives of the vertebrates. Many aspects of their lives and development are, however, poorly understood. It is generally thought that among ascidian tunicates such as Ciona, the superficially vertebrate-like central nervous system of the motile 'tadpole' larva degenerates and is completely replaced by an adult nervous system that develops from scratch. Here, state-of-the-art transgenesis and imaging techniques are used to show that this is not the case. There is continuity between the larval and adult nervous systems, with the adult nervous system developing from stem-cell-like ependymal cells found in the larva.

During mitosis, adherent cells change from a flattened to a rounded morphology, and this is thought to be necessary for the geometric requirements of cell division. Here, the forces that drive this shape change are studied. Mitotic rounding force depends both on the actomyosin cytoskeleton and the cell's ability to regulate osmolarity. The rounding force is generated by osmotic pressure and the actomyosin cortex maintains this rounding pressure against external forces. These results support the idea that in animal cells, the actomyosin cortex behaves like an internal cell wall that directs osmotic expansion to control cell shape.

The kinase JNK is known to stimulate c-Jun transcriptional activity, but the molecular mechanism has been unclear. Here, N-terminal phosphorylation of c-Jun is shown to antagonize the interaction of c-Jun with Mbd3, a component of the repressor complex NuRD. The interaction between c-Jun and Mbd3 is shown to be important in regulating the proliferation of intestinal progenitor cells in mice.

Face recognition in golden paper wasps may be an adaptation to their social environment.