Volume 460 Issue 7257, 13 August 2009

Twenty years on, the success of the Montreal Protocol can help inform plans to mitigate climate change.

There is every reason to be optimistic about the Obama administration's attitude towards science.

But particle physicists will have to scale back the energies of their experiments for years.

Climate change and energy are high on the agenda for Obama's panel.

Fresh freezers needed to preserve ancient gas, scientists say.

Dispute over ownership raises concerns among flu scientists.

Growing demands for access to information swamp scientist.

European investment could see knock-out rats catching up with mutant mice in medical research.

Groundwater depletion raises spectre of shortages.

When nations made plans to save the ozone layer, they didn't factor in global warming. Quirin Schiermeier reports on how two environmental problems complicate each other.

An influential book accuses Europe of keeping genetically modified crops out of Africa, but, by polarizing the debate, it undermines efforts to improve the continent's agriculture, warn Ian Scoones and Dominic Glover.

How can identical particles be crammed together as densely as possible? A combination of theory and computer simulations shows how the answer to this intricate problem depends on the shape of the particles.

The ability of embryonic stem cells to give rise to any cell type relies on a remodelling protein that maintains open chromatin. But the chromatin landscape of these cells may be more complex than previously thought.

The identification of a general connection between biogeochemistry and the structure of food webs would constitute a considerable advance in understanding ecosystems. Ecologists are on the case.

A gene that is found to be mutated in a type of blood cancer exhibits properties of both a growth-suppressing tumour suppressor and a growth-promoting oncogene.

Candida albicans is notorious as an opportunistic microbe that causes thrush and serious systemic disease. For geneticists, however, it offers continuing revelations into the wondrously varied sex lives of fungi.

Hydrogen is hailed as a non-polluting synthetic fuel that could replace oil, especially for transport applications. The technology to make this a reality — particularly hydrogen-storage materials — has been a long time coming, but the first commercial vehicles might now be only a few years away.

A hallmark of stem cells is an open chromatin largely devoid of heterochromatin, but which molecules are required to maintain it is unknown, as well as whether an open chromatin is necessary for the differentiation potential of stem cells. Here, the chromatin remodelling factor Chd1 is shown to be required to maintain the open chromatin state of pluripotent mouse embryonic stem cells and to be essential for the pluripotency of these cells.

The near uniformity of the light curves of type Ia supernovae makes them good 'standard candles' for measuring cosmic expansion, but a correction must be applied to account for the fact that the brighter ones have broader light curves. Here, multi-dimensional modelling of the explosion physics and radioactive transfer reveals that failing to correct for an effect on the slope and normalization of the width–luminosity relation could lead to systematic overestimates of up to 2% of the distance to remote supernovae.

The presence of small-scale channels and dry riverbeds at latitudes thought incapable of supporting convection on Saturn's moon Titan has therefore been suggested to be due to mechanisms unrelated to precipitation. Here, however, the presence of bright, transient, tropospheric clouds in tropical latitudes is reported. It is thought that convective pulses at one latitude can trigger short-term convection at other latitudes, resulting in methane rain.

Kepler's conjecture gives the densest possible packing for spherical particles but, until now, there has not been an analogous system for determining dense polyhedral packings. Using a variety of multiparticle initial configurations it has now been possible to determine the densest known packings for the Platonic solids and to conjecture that those of Platonic and Archimedean solids with central symmetry are given by their corresponding densest lattice packings.

Tropical cyclone activity in the Atlantic, as measured by annual storm counts, reached unusually high levels over the past decade. This recent activity is now placed in a longer-term context by comparing two independent estimates of hurricane activity over the past 1,500 years; there is evidence of a peak in Atlantic tropical cyclone activity during medieval times (around AD 1000) that rivals or exceeds recent levels of activity.

There are indications that the general height of mountain ranges is directly influenced by the extent of glaciation through an efficient denudation mechanism known as the glacial buzzsaw. Here, a global analysis of topography shows that variations in maximum mountain height correlate closely with climate-controlled gradients in snowline altitude rather than with tectonic activity. Further, the use of a numerical model self-consistently produces the hypsometric signature of the glacial buzzsaw.

The placoderms are a large group of primitive armoured fishes, which, although now extinct, could shed light on the evolution of jawed vertebrates. Recent fossil finds have been discovered with embryos, illustrating that fertilization was internal, but direct evidence for this was missing. Here, the discovery of a completely ossified pelvic clasper in a male Incisoscutum ritchiei confirms internal fertilization in arthrodires, a large and important placoderm group.

Until recently, the human pathogenic yeast Candida albicans was thought to be strictly asexual, existing only as an obligate diploid. However, here it is shown that under specific conditions — in the absence of the secreted protease Bar1 — efficient same-sex mating can take place.

Genomic diversity is difficult to generate in the laboratory in an efficient way. Here, multiplex automated genome engineering (MAGE) is described for large-scale programming and evolution of cells. It is an automated and efficient approach that expedites the design and evolution of organisms with new and improved properties.

It has recently become apparent that rods and cones are not the only photoreceptors in mammals. A third class, known as intrinsically photosensitive retinal ganglion cells, use the photopigment melanopsin and mediate non-image-forming visual functions such as circadian photoentrainment. In teleost fish, a subset of horizontal cells is now shown to be photosensitive; the photopigment responsible for this seems to be melanopsin.

Acquired uniparental disomy (aUPD), a common feature of cancer genomes, is associated with gain-of-function mutations of proto-oncogenes as well as with loss-of-function mutations of tumour suppressor genes. Here, gain-of-function mutations of the C-CBL tumour suppressor are shown to be tightly associated with aUPD of the 11q arm in certain myeloid neoplasms.

In order to investigate the earliest molecular mechanisms of germ cell specification, mouse embryonic stem cells were differentiated into putative primordial germ cells (PGCs) in vitro. The use of inhibitory RNAs to then screen candidate genes for effects on the development of these cells demonstrates a genetic pathway for PGC specification involving Lin28, a negative regulator of let-7 microRNA processing.

The ends of linear eukaryotic chromosomes are capped by sequences known as telomeres. Although telomeres are essentially one half of a DNA double-strand break, which is a pathogenic lesion that must be repaired, telomeres do not normally activate DNA damage repair pathways. Here, the three-member MRN complex is shown to serve two roles at the telomere: it protects newly synthesized telomeric ends from repair factors and it promotes a type of fusion repair when the telomere is not functioning properly.

British Columbia aims to become a leader in clean-energy technology. Virginia Gewin tracks progress.

Happy landings.

Metalloproteins — proteins containing metal atoms or clusters — are involved in a wide range of important biological processes. Recent advances in our understanding of metalloproteins include how enzymes containing complex metal clusters metabolize small gaseous molecules, how proteins containing iron—sulphur clusters are assembled, and how enzymes containing a single metal ion catalyse the halogenation of small organic molecules.