Nature is the international weekly journal of science: a magazine style journal that publishes full-length research papers in all disciplines of science, as well as News and Views, reviews, news, features, commentaries, web focuses and more, covering all branches of science and how science impacts upon all aspects of society and life.
Vastly more salmon could be escaping from aquaculture farms (pictured) than is officially reported, say Ove Skilbrei and his colleagues at the Institute of Marine Research in Bergen, Norway.Farmed salmon that escape could mate with wild populations and make them less fit for survival.
A combination of antibodies and multiple virus-activating drugs can keep HIV from resurging in infected mice, even after treatment ends.During drug treatment, HIV enters a dormant state and stays hidden inside infected cells; afterwards, it bounces back. A team led by Michel Nussenzweig at
Soft, stretchy, Lego-style bricks offer a way to make three-dimensional (3D) prototypes of elastic structures, according to researchers at Harvard University in Cambridge, Massachusetts.'Click-e-bricks', which were developed by George Whitesides and his colleagues, can be used to build stretchy devices, such as hollow ones
Astronomers have captured three-dimensional images of organic compounds streaming from two comets.Comets contain some of the oldest materials in the Solar System. Using the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, Martin Cordiner of the NASA Goddard Space Flight Center in Greenbelt, Maryland, and
Two groups have shown how Salmonella bacteria can resist antibiotics.Dirk Bumann of the University of Basel in Switzerland and his colleagues infected mice with modified Salmonella strains that glow green when they divide. They found varying rates of division in different tissues,
Seven particles captured by NASA's Stardust spacecraft may be the first sample of dust from beyond the Solar System that has been brought back to Earth.Andrew Westphal at the University of California, Berkeley, and his colleagues — with the help of 30,714 citizen scientists
The illegal killing of elephants in Africa to supply the ivory trade has reached unsustainable rates.George Wittemyer at Colorado State University in Fort Collins and his colleagues used data from elephant carcass surveys in 45 sites across Africa to model broader trends in elephant
The Ebola virus might elude immune responses by stopping a key protein in infected cells from activating defence genes.Ebola, which kills up to 90% of people it infects, is known to disrupt the activity of interferon, a crucial antiviral protein. Gaya Amarasinghe at Washington
A thousand-strong army of coin-sized robots (pictured) can arrange itself into various configurations.Michael Rubenstein and his co-workers at Harvard University in Cambridge, Massachusetts, programmed 1,024 robots with a simple set of rules and an image of a shape to be formed. Four
Nature's roundup of the papers and issues gaining traction on social media.Ancient hominin bones made good fodder for debate on social media of late, when researchers suggested a theory about the identity of the Indonesian 'Hobbit'. Scientists also took note of a fast,
The Research Highlight 'Brain scans predict TV hits' (Nature512, 8;10.1038/512008c2014) notes that Jacek Dmochowski is at Stanford University; however, the research described was done at the City College of New York.
As a concept, sustainability is now near-ubiquitous. But is it a “buzzless buzzword”, as environmentalist Bill McKibben has opined? Historian Jeremy Caradonna writes that, on the contrary, this dynamic ethos has plenty of buzz. Predicated on joined-up thinking (such as the idea that society, economy
The UK government's proposed Infrastructure Bill for England and Wales gives new powers to control or eradicate invasive, non-native species (see go.nature.com/kbkvtt). However, what constitutes such a species needs careful definition to ensure that any use of these powers is beneficial for conservation.The
Microbial ecologists must coordinate to archive sample collections and genetic material. This will prevent valuable specimens from being lost to science and allow rigorous assessment of the effects of globally changing factors, disease and pollution on microbial communities.Archiving is particularly valuable for hard-to-obtain or
Sven Mecke and colleagues call for prior assessment of ecological risks that might be associated with eradication measures against the invasive Asian common toad Duttaphrynus melanostictus (Nature511, 534;10.1038/511534c2014). The Amphibian Specialist Group in Madagascar — part of
Good preclinical models of ageing are needed to discover the molecular mechanisms behind declining human physical performance (Nature511, 405–407;10.1038/511405a2014). The latest animal models of frailty are a step in the right direction.For example, a genetically
Translational biomedical research into ageing and longevity needs to include social science if it is to produce interventions for slowing physiological decline (Nature511, 405–407;10.1038/511405a2014).Promoting a healthy lifespan depends on social factors as well as on
The News Feature ‘Scientists and the social network’ (Nature512, 126–129; 2014) gave the wrong affiliation for Laura Warman, who is at the University of Hawaii at Hilo. And the News story ‘Health check for deep-sea mining’ (Nature512, 122–123;
The first description of the microorganisms inhabiting a subglacial lake deep below the Antarctic ice sheet reveals some of the complex interactive metabolic processes that sustain these microbial communities. See Letter p.310
Blood stem cells derive at least in part from an embryonic vessel called the dorsal aorta. It emerges that a flanking tissue called the somite contributes cells and signals to this process. See Letters p.314 & p.319
An earthquake off Chile in 2014 occurred in a region where a great seismic event was expected. Two studies reveal that months of foreshocks and slow slip on the associated plate-boundary fault preceded the event. See Letters p.295 & p.299
The application of improved radiocarbon-dating techniques to samples from archaeological sites ranging from Russia to Spain has redefined the timing of the final disappearance of Neanderthals from Europe. See Letter p.306
Devices known as magneto-optical traps have long been used to cool and confine atoms, but not molecules — until now. This new ability should enable many studies and applications of the physics of ultracold molecules. See Letter p.286
Programmed −1 ribosomal frameshift (−1 PRF) signals redirect translating ribosomes to slip back one base on messenger RNAs. Although well characterized in viruses, how these elements may regulate cellular gene expression is not understood. Here we describe a −1 PRF signal in the human mRNA
Type-A γ-aminobutyric acid receptors (GABAARs) are the principal mediators of rapid inhibitory synaptic transmission in the human brain. A decline in GABAAR signalling triggers hyperactive neurological disorders such as insomnia, anxiety and epilepsy. Here we present the first three-dimensional structure of
Neurotransmitter-gated ion channels of the Cys-loop receptor family mediate fast neurotransmission throughout the nervous system. The molecular processes of neurotransmitter binding, subsequent opening of the ion channel and ion permeation remain poorly understood. Here we present the X-ray structure of a mammalian Cys-loop receptor, the
Betelgeuse, a nearby red supergiant, is a fast-moving star with a powerful stellar wind that drives a bow shock into its surroundings. This picture has been challenged by the discovery of a dense and almost static shell that is three times closer to the star than the bow shock and has been decelerated by some external force. The two physically distinct structures cannot both be formed by the hydrodynamic interaction of the wind with the interstellar medium. Here we report that a model in which Betelgeuse’s wind is photoionized by radiation from external sources can explain the static shell without requiring a new understanding of the bow shock. Pressure from the photoionized wind generates a standing shock in the neutral part of the wind and forms an almost static, photoionization-confined shell. Other red supergiants should have much more massive shells than Betelgeuse, because the photoionization-confined shell traps up to 35 per cent of all mass lost during the red supergiant phase, confining this gas close to the star until it explodes. After the supernova explosion, massive shells dramatically affect the supernova light curve, providing a natural explanation for the many supernovae that have signatures of circumstellar interaction.
Laser cooling and trapping are central to modern atomic physics. The most used technique in cold-atom physics is the magneto-optical trap (MOT), which combines laser cooling with a restoring force from radiation pressure. For a variety of atomic species, MOTs can capture and cool large numbers of particles to ultracold temperatures (less than ∼1 millikelvin); this has enabled advances in areas that range from optical clocks to the study of ultracold collisions, while also serving as the ubiquitous starting point for further cooling into the regime of quantum degeneracy. Magneto-optical trapping of molecules could provide a similarly powerful starting point for the study and manipulation of ultracold molecular gases. The additional degrees of freedom associated with the vibration and rotation of molecules, particularly their permanent electric dipole moments, allow a broad array of applications not possible with ultracold atoms. Spurred by these ideas, a variety of methods has been developed to create ultracold molecules. Temperatures below 1 microkelvin have been demonstrated for diatomic molecules assembled from pre-cooled alkali atoms, but for the wider range of species amenable to direct cooling and trapping, only recently have temperatures below 100 millikelvin been achieved. The complex internal structure of molecules complicates magneto-optical trapping. However, ideas and methods necessary for creating a molecular MOT have been developed recently. Here we demonstrate three-dimensional magneto-optical trapping of a diatomic molecule, strontium monofluoride (SrF), at a temperature of approximately 2.5 millikelvin, the lowest yet achieved by direct cooling of a molecule. This method is a straightforward extension of atomic techniques and is expected to be viable for a significant number of diatomic species. With further development, we anticipate that this technique may be employed in any number of existing and proposed molecular experiments, in applications ranging from precision measurement to quantum simulation and quantum information to ultracold chemistry.
During glacial periods of the Late Pleistocene, an abundance of proxy data demonstrates the existence of large and repeated millennial-scale warming episodes, known as Dansgaard–Oeschger (DO) events. This ubiquitous feature of rapid glacial climate change can be extended back as far as 800,000 years before present (bp) in the ice core record, and has drawn broad attention within the science and policy-making communities alike. Many studies have been dedicated to investigating the underlying causes of these changes, but no coherent mechanism has yet been identified. Here we show, by using a comprehensive fully coupled model, that gradual changes in the height of the Northern Hemisphere ice sheets (NHISs) can alter the coupled atmosphere–ocean system and cause rapid glacial climate shifts closely resembling DO events. The simulated global climate responses—including abrupt warming in the North Atlantic, a northward shift of the tropical rainbelts, and Southern Hemisphere cooling related to the bipolar seesaw—are generally consistent with empirical evidence. As a result of the coexistence of two glacial ocean circulation states at intermediate heights of the ice sheets, minor changes in the height of the NHISs and the amount of atmospheric CO2 can trigger the rapid climate transitions via a local positive atmosphere–ocean–sea-ice feedback in the North Atlantic. Our results, although based on a single model, thus provide a coherent concept for understanding the recorded millennial-scale variability and abrupt climate changes in the coupled atmosphere–ocean system, as well as their linkages to the volume of the intermediate ice sheets during glacials.
The seismic gap theory identifies regions of elevated hazard based on a lack of recent seismicity in comparison with other portions of a fault. It has successfully explained past earthquakes (see, for example, ref. 2) and is useful for qualitatively describing where large earthquakes might occur. A large earthquake had been expected in the subduction zone adjacent to northern Chile, which had not ruptured in a megathrust earthquake since a M ∼8.8 event in 1877. On 1 April 2014 a M 8.2 earthquake occurred within this seismic gap. Here we present an assessment of the seismotectonics of the March–April 2014 Iquique sequence, including analyses of earthquake relocations, moment tensors, finite fault models, moment deficit calculations and cumulative Coulomb stress transfer. This ensemble of information allows us to place the sequence within the context of regional seismicity and to identify areas of remaining and/or elevated hazard. Our results constrain the size and spatial extent of rupture, and indicate that this was not the earthquake that had been anticipated. Significant sections of the northern Chile subduction zone have not ruptured in almost 150 years, so it is likely that future megathrust earthquakes will occur to the south and potentially to the north of the 2014 Iquique sequence.
On 1 April 2014, Northern Chile was struck by a magnitude 8.1 earthquake following a protracted series of foreshocks. The Integrated Plate Boundary Observatory Chile monitored the entire sequence of events, providing unprecedented resolution of the build-up to the main event and its rupture evolution. Here we show that the Iquique earthquake broke a central fraction of the so-called northern Chile seismic gap, the last major segment of the South American plate boundary that had not ruptured in the past century. Since July 2013 three seismic clusters, each lasting a few weeks, hit this part of the plate boundary with earthquakes of increasing peak magnitudes. Starting with the second cluster, geodetic observations show surface displacements that can be associated with slip on the plate interface. These seismic clusters and their slip transients occupied a part of the plate interface that was transitional between a fully locked and a creeping portion. Leading up to this earthquake, the b value of the foreshocks gradually decreased during the years before the earthquake, reversing its trend a few days before the Iquique earthquake. The mainshock finally nucleated at the northern end of the foreshock area, which skirted a locked patch, and ruptured mainly downdip towards higher locking. Peak slip was attained immediately downdip of the foreshock region and at the margin of the locked patch. We conclude that gradual weakening of the central part of the seismic gap accentuated by the foreshock activity in a zone of intermediate seismic coupling was instrumental in causing final failure, distinguishing the Iquique earthquake from most great earthquakes. Finally, only one-third of the gap was broken and the remaining locked segments now pose a significant, increased seismic hazard with the potential to host an earthquake with a magnitude of >8.5.
The origin and radiation of mammals are key events in the history of life, with fossils placing the origin at 220 million years ago, in the Late Triassic period. The earliest mammals, representing the first 50 million years of their evolution and including the most basal taxa, are widely considered to be generalized insectivores. This implies that the first phase of the mammalian radiation—associated with the appearance in the fossil record of important innovations such as heterodont dentition, diphyodonty and the dentary–squamosal jaw joint—was decoupled from ecomorphological diversification. Finds of exceptionally complete specimens of later Mesozoic mammals have revealed greater ecomorphological diversity than previously suspected, including adaptations for swimming, burrowing, digging and even gliding, but such well-preserved fossils of earlier mammals do not exist, and robust analysis of their ecomorphological diversity has previously been lacking. Here we present the results of an integrated analysis, using synchrotron X-ray tomography and analyses of biomechanics, finite element models and tooth microwear textures. We find significant differences in function and dietary ecology between two of the earliest mammaliaform taxa, Morganucodon and Kuehneotherium—taxa that are central to the debate on mammalian evolution. Morganucodon possessed comparatively more forceful and robust jaws and consumed ‘harder’ prey, comparable to extant small-bodied mammals that eat considerable amounts of coleopterans. Kuehneotherium ingested a diet comparable to extant mixed feeders and specialists on ‘soft’ prey such as lepidopterans. Our results reveal previously hidden trophic specialization at the base of the mammalian radiation; hence even the earliest mammaliaforms were beginning to diversify—morphologically, functionally and ecologically. In contrast to the prevailing view, this pattern suggests that lineage splitting during the earliest stages of mammalian evolution was associated with ecomorphological specialization and niche partitioning.
The timing of Neanderthal disappearance and the extent to which they overlapped with the earliest incoming anatomically modern humans (AMHs) in Eurasia are key questions in palaeoanthropology. Determining the spatiotemporal relationship between the two populations is crucial if we are to understand the processes, timing and reasons leading to the disappearance of Neanderthals and the likelihood of cultural and genetic exchange. Serious technical challenges, however, have hindered reliable dating of the period, as the radiocarbon method reaches its limit at ∼50,000 years ago. Here we apply improved accelerator mass spectrometry 14C techniques to construct robust chronologies from 40 key Mousterian and Neanderthal archaeological sites, ranging from Russia to Spain. Bayesian age modelling was used to generate probability distribution functions to determine the latest appearance date. We show that the Mousterian ended by 41,030–39,260 calibrated years bp (at 95.4% probability) across Europe. We also demonstrate that succeeding ‘transitional’ archaeological industries, one of which has been linked with Neanderthals (Châtelperronian), end at a similar time. Our data indicate that the disappearance of Neanderthals occurred at different times in different regions. Comparing the data with results obtained from the earliest dated AMH sites in Europe, associated with the Uluzzian technocomplex, allows us to quantify the temporal overlap between the two human groups. The results reveal a significant overlap of 2,600–5,400 years (at 95.4% probability). This has important implications for models seeking to explain the cultural, technological and biological elements involved in the replacement of Neanderthals by AMHs. A mosaic of populations in Europe during the Middle to Upper Palaeolithic transition suggests that there was ample time for the transmission of cultural and symbolic behaviours, as well as possible genetic exchanges, between the two groups.
Liquid water has been known to occur beneath the Antarctic ice sheet for more than 40 years, but only recently have these subglacial aqueous environments been recognized as microbial ecosystems that may influence biogeochemical transformations on a global scale. Here we present the first geomicrobiological description of water and surficial sediments obtained from direct sampling of a subglacial Antarctic lake. Subglacial Lake Whillans (SLW) lies beneath approximately 800 m of ice on the lower portion of the Whillans Ice Stream (WIS) in West Antarctica and is part of an extensive and evolving subglacial drainage network. The water column of SLW contained metabolically active microorganisms and was derived primarily from glacial ice melt with solute sources from lithogenic weathering and a minor seawater component. Heterotrophic and autotrophic production data together with small subunit ribosomal RNA gene sequencing and biogeochemical data indicate that SLW is a chemosynthetically driven ecosystem inhabited by a diverse assemblage of bacteria and archaea. Our results confirm that aquatic environments beneath the Antarctic ice sheet support viable microbial ecosystems, corroborating previous reports suggesting that they contain globally relevant pools of carbon and microbes that can mobilize elements from the lithosphere and influence Southern Ocean geochemical and biological systems.
Haematopoietic stem cells (HSCs) are self-renewing stem cells capable of replenishing all blood lineages. In all vertebrate embryos that have been studied, definitive HSCs are generated initially within the dorsal aorta (DA) of the embryonic vasculature by a series of poorly understood inductive events. Previous studies have identified that signalling relayed from adjacent somites coordinates HSC induction, but the nature of this signal has remained elusive. Here we reveal that somite specification of HSCs occurs via the deployment of a specific endothelial precursor population, which arises within a sub-compartment of the zebrafish somite that we have defined as the endotome. Endothelial cells of the endotome are specified within the nascent somite by the activity of the homeobox gene meox1. Specified endotomal cells consequently migrate and colonize the DA, where they induce HSC formation through the deployment of chemokine signalling activated in these cells during endotome formation. Loss of meox1 activity expands the endotome at the expense of a second somitic cell type, the muscle precursors of the dermomyotomal equivalent in zebrafish, the external cell layer. The resulting increase in endotome-derived cells that migrate to colonize the DA generates a dramatic increase in chemokine-dependent HSC induction. This study reveals the molecular basis for a novel somite lineage restriction mechanism and defines a new paradigm in induction of definitive HSCs.