Cultura Bit

Attributing physical and biological impacts to anthropogenic climate change

Nature 453, 353 (2008). doi:10.1038/nature06937

Authors: Cynthia Rosenzweig, David Karoly, Marta Vicarelli, Peter Neofotis, Qigang Wu, Gino Casassa, Annette Menzel, Terry L. Root, Nicole Estrella, Bernard Seguin, Piotr Tryjanowski, Chunzhen Liu, Samuel Rawlins & Anton Imeson

Significant changes in physical and biological systems are occurring on all continents and in most oceans, with a concentration of available data in Europe and North America. Most of these changes are in the direction expected with warming temperature. Here we show that these changes

Crystal structure of squid rhodopsin

Nature 453, 363 (2008). doi:10.1038/nature06925

Authors: Midori Murakami & Tsutomu Kouyama

Invertebrate phototransduction uses an inositol-1,4,5-trisphosphate signalling cascade in which photoactivated rhodopsin stimulates a Gq-type G protein, that is, a class of G protein that stimulates membrane-bound phospholipase Cβ. The same cascade is used by many G-protein-coupled receptors, indicating that invertebrate rhodopsin is a

True polar wander on Europa from global-scale small-circle depressions

Nature 453, 368 (2008). doi:10.1038/nature06911

Authors: Paul Schenk, Isamu Matsuyama & Francis Nimmo

The tectonic patterns and stress history of Europa are exceedingly complex and many large-scale features remain unexplained. True polar wander, involving reorientation of Europa’s floating outer ice shell about the tidal axis with Jupiter, has been proposed as a possible explanation for some of the features. This mechanism is possible if the icy shell is latitudinally variable in thickness and decoupled from the rocky interior. It would impose high stress levels on the shell, leading to predictable fracture patterns. No satisfactory match to global-scale features has hitherto been found for polar wander stress patterns. Here we describe broad arcuate troughs and depressions on Europa that do not fit other proposed stress mechanisms in their current position. Using imaging from three spacecraft, we have mapped two global-scale organized concentric antipodal sets of arcuate troughs up to hundreds of kilometres long and 300 m to ∼1.5 km deep. An excellent match to these features is found with stresses caused by an episode of ∼80° true polar wander. These depressions also appear to be geographically related to other large-scale bright and dark lineaments, suggesting that many of Europa’s tectonic patterns may also be related to true polar wander.

A GaAs polariton light-emitting diode operating near room temperature

Nature 453, 372 (2008). doi:10.1038/nature06979

Authors: S. I. Tsintzos, N. T. Pelekanos, G. Konstantinidis, Z. Hatzopoulos & P. G. Savvidis

The increasing ability to control light–matter interactions at the nanometre scale has improved the performance of semiconductor lasers in the past decade. The ultimate optimization is realized in semiconductor microcavities, in which strong coupling between quantum-well excitons and cavity photons gives rise to hybrid half-light/half-matter polariton quasiparticles. The unique properties of polaritons—such as stimulated scattering, parametric amplification, lasing, condensation and superfluidity—are believed to provide the basis for a new generation of polariton emitters and semiconductor lasers. Until now, polariton lasing and nonlinearities have only been demonstrated in optical experiments, which have shown the potential to reduce lasing thresholds by two orders of magnitude compared to conventional semiconductor lasers. Here we report an experimental realization of an electrically pumped semiconductor polariton light-emitting device, which emits directly from polariton states at a temperature of 235 K. Polariton electroluminescence data reveal characteristic anticrossing between exciton and cavity modes, a clear signature of the strong coupling regime. These findings represent a substantial step towards the realization of ultra-efficient polaritonic devices with unprecedented characteristics.

High-resolution carbon dioxide concentration record 650,000–800,000 years before present

Nature 453, 379 (2008). doi:10.1038/nature06949

Authors: Dieter Lüthi, Martine Le Floch, Bernhard Bereiter, Thomas Blunier, Jean-Marc Barnola, Urs Siegenthaler, Dominique Raynaud, Jean Jouzel, Hubertus Fischer, Kenji Kawamura & Thomas F. Stocker

Changes in past atmospheric carbon dioxide concentrations can be determined by measuring the composition of air trapped in ice cores from Antarctica. So far, the Antarctic Vostok and EPICA Dome C ice cores have provided a composite record of atmospheric carbon dioxide levels over the past 650,000 years. Here we present results of the lowest 200 m of the Dome C ice core, extending the record of atmospheric carbon dioxide concentration by two complete glacial cycles to 800,000 yr before present. From previously published data and the present work, we find that atmospheric carbon dioxide is strongly correlated with Antarctic temperature throughout eight glacial cycles but with significantly lower concentrations between 650,000 and 750,000 yr before present. Carbon dioxide levels are below 180 parts per million by volume (p.p.m.v.) for a period of 3,000 yr during Marine Isotope Stage 16, possibly reflecting more pronounced oceanic carbon storage. We report the lowest carbon dioxide concentration measured in an ice core, which extends the pre-industrial range of carbon dioxide concentrations during the late Quaternary by about 10 p.p.m.v. to 172–300 p.p.m.v.

Orbital and millennial-scale features of atmospheric CH4 over the past 800,000 years

Nature 453, 383 (2008). doi:10.1038/nature06950

Authors: Laetitia Loulergue, Adrian Schilt, Renato Spahni, Valérie Masson-Delmotte, Thomas Blunier, Bénédicte Lemieux, Jean-Marc Barnola, Dominique Raynaud, Thomas F. Stocker & Jérôme Chappellaz

Atmospheric methane is an important greenhouse gas and a sensitive indicator of climate change and millennial-scale temperature variability. Its concentrations over the past 650,000 years have varied between ∼350 and ∼800 parts per 109 by volume (p.p.b.v.) during glacial and interglacial periods, respectively. In comparison, present-day methane levels of ∼1,770 p.p.b.v. have been reported. Insights into the external forcing factors and internal feedbacks controlling atmospheric methane are essential for predicting the methane budget in a warmer world. Here we present a detailed atmospheric methane record from the EPICA Dome C ice core that extends the history of this greenhouse gas to 800,000 yr before present. The average time resolution of the new data is ∼380 yr and permits the identification of orbital and millennial-scale features. Spectral analyses indicate that the long-term variability in atmospheric methane levels is dominated by ∼100,000 yr glacial–interglacial cycles up to ∼400,000 yr ago with an increasing contribution of the precessional component during the four more recent climatic cycles. We suggest that changes in the strength of tropical methane sources and sinks (wetlands, atmospheric oxidation), possibly influenced by changes in monsoon systems and the position of the intertropical convergence zone, controlled the atmospheric methane budget, with an additional source input during major terminations as the retreat of the northern ice sheet allowed higher methane emissions from extending periglacial wetlands. Millennial-scale changes in methane levels identified in our record as being associated with Antarctic isotope maxima events are indicative of ubiquitous millennial-scale temperature variability during the past eight glacial cycles.

Making the paper: Paul Elliott

Nature 453, xiv (2008). doi:10.1038/7193xiva

Thousands of urine samples point to the causes of high blood pressure.

Making the paper: Paul Elliott

Nature 453, xiv (2008). doi:10.1038/7193xiva

Thousands of urine samples point to the causes of high blood pressure.

Abstractions

Nature 453, xiv (2008). doi:10.1038/7193xivb

Last authorThe 'progress zone' model of limb development posits that the embryonic cells that become limbs are specified in a progressive manner: first, the upper part; then the middle; and last, hand or foot. Despite there being no direct evidence for this, the model

From the blogosphere

Nature 453, xiv (2008). doi:10.1038/7193xivc

Scientific informatics programmes require massive financial investment, so it is difficult for governments to decide which ones to support. One programme that has been successful in securing funding is the iPlant Collaborative (http://iplantcollaborative.org/) — a 'cyberinfrastructure' collaborative for the plant sciences. Recently set

The next big climate challenge

Nature 453, 257 (2008). doi:10.1038/453257a

Governments should work together to build the supercomputers needed for future predictions that can capture the detail required to inform policy.

Stuck in the mud

Nature 453, 258 (2008). doi:10.1038/453258a

The Environmental Protection Agency must gather data on the toxicity of spreading sewage sludge.

Negative results

Nature 453, 258 (2008). doi:10.1038/453258b

Retracted papers require a thorough explanation of what went wrong in the experiments.

Marine ecology: Deep-sea cheetahs

Nature 453, 260 (2008). doi:10.1038/453260a

J. Anim. Ecol. doi:10.1111/j.1365-2656.2008.01393.x (2008)At first glance, pilot whales and cheetahs seem unlikely to have much in common, but researchers have found at least one similarity: a tendency to sprint after prey, sacrificing energy for speed. This is the

Neuroscience: Hearing what and where

Nature 453, 260 (2008). doi:10.1038/453260b

Nature Neurosci.11, 609–616 (2008) doi:10.1038/nn.2108Neuroscientists have long thought that the brain uses different regions to locate sounds and to analyse them, as is known to be true for vision. Stephen Lomber of the University of Western

Palaeoclimate: Methane didn't act alone

Nature 453, 260 (2008). doi:10.1038/453260c

Geology36, 315–318 (2008) doi:10.1130/G24474A.1Methane outbursts from seafloor deposits are unlikely to have been the sole cause of an extreme episode of global warming around the time of the Palaeocene–Eocene Thermal Maximum some 55 million years ago.

Geoscience: The dust settles

Nature 453, 260 (2008). doi:10.1038/453260d

Global Biogeochem. Cycles22, GB2006 (2008) doi:10.1029/2007GB002984Iron-rich dust, blown from arid lands and dropped into the oceans, is an important nutrient for phytoplankton. But according to Thibaut Wagener at the Oceanographic Laboratory of France's National Centre for Scientific Research

Quantum optics: Open the box

Nature 453, 260 (2008). doi:10.1038/453260e

Europhys. Lett.82, 30002 (2008) doi:10.1209/0295-5075/82/30002How can online gamblers be sure that the casino isn't cheating? They can't — but the quantum gambling machine devised by Yi-Sheng Zhang and colleagues at the University of Science and Technology of China

Neurobiology: The heart in the head

Nature 453, 260 (2008). doi:10.1038/453260f

Science doi:10.1126/science.1153651 (2008) Do humans care more about distributing goods efficiently or fairly? Is this decision rational or emotional? Steven Quartz of the California Institute of Technology in Pasadena and his colleagues used functional magnetic resonance imaging to investigate.The

Astronomy: A galaxy far, far away

Nature 453, 261 (2008). doi:10.1038/453261a

Asrophys. J.678, 647–654 (2008) doi:10.1086/533519Astronomers have spotted what seems to be the most distant galaxy ever observed.The galaxy dates to 13 billion years ago, when the Universe was less than a billion years old. Larry