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A sensitive electrometer based on a Rydberg atom in a Schrödinger-cat state

Nature - Wed, 07/13/2016 - 00:00

A sensitive electrometer based on a Rydberg atom in a Schrödinger-cat state

Nature 535, 7611 (2016). doi:10.1038/nature18327

Authors: Adrien Facon, Eva-Katharina Dietsche, Dorian Grosso, Serge Haroche, Jean-Michel Raimond, Michel Brune & Sébastien Gleyzes

Fundamental quantum fluctuations caused by the Heisenberg principle limit measurement precision. If the uncertainty is distributed equally between conjugate variables of the meter system, the measurement precision cannot exceed the standard quantum limit. When the meter is a large angular momentum, going beyond the standard quantum limit requires non-classical states such as squeezed states or Schrödinger-cat-like states. However, the metrological use of the latter has been so far restricted to meters with a relatively small total angular momentum because the experimental preparation of these non-classical states is very challenging. Here we report a measurement of an electric field based on an electrometer consisting of a large angular momentum (quantum number J ≈ 25) carried by a single atom in a high-energy Rydberg state. We show that the fundamental Heisenberg limit can be approached when the Rydberg atom undergoes a non-classical evolution through Schrödinger-cat states. Using this method, we reach a single-shot sensitivity of 1.2 millivolts per centimetre for a 100-nanosecond interaction time, corresponding to 30 microvolts per centimetre per square root hertz at our 3 kilohertz repetition rate. This highly sensitive, non-invasive space- and time-resolved field measurement extends the realm of electrometric techniques and could have important practical applications: detection of individual electrons in mesoscopic devices at a distance of about 100 micrometres with a megahertz bandwidth is within reach.

Categories: Literature

Self-assembly of graphene ribbons by spontaneous self-tearing and peeling from a substrate

Nature - Wed, 07/13/2016 - 00:00

Self-assembly of graphene ribbons by spontaneous self-tearing and peeling from a substrate

Nature 535, 7611 (2016). doi:10.1038/nature18304

Authors: James Annett & Graham L. W. Cross

Graphene and related two-dimensional materials have shown unusual and exceptional mechanical properties, with similarities to origami-like paper folding and kirigami-like cutting demonstrated. For paper analogues, a critical difference between macroscopic sheets and a two-dimensional solid is the molecular scale of the thin dimension of the latter, allowing the thermal activation of considerable out-of-plane motion. So far thermal activity has been shown to produce local wrinkles in a free graphene sheet that help in theoretically understanding its stability, for example, and give rise to unexpected long-range bending stiffness. Here we show that thermal activation can have a more marked effect on the behaviour of two-dimensional solids, leading to spontaneous and self-driven sliding, tearing and peeling from a substrate on scales approaching the macroscopic. We demonstrate that scalable nanoimprint-style contact techniques can nucleate and direct the parallel self-assembly of graphene ribbons of controlled shape in ambient conditions. We interpret our observations through a simple fracture-mechanics model that shows how thermodynamic forces drive the formation of the graphene–graphene interface in lieu of substrate contact with sufficient strength to peel and tear multilayer graphene sheets. Our results show how weak physical surface forces can be harnessed and focused by simple folded configurations of graphene to tear the strongest covalent bond. This effect may hold promise for the patterning and mechanical actuating of devices based on two-dimensional materials.

Categories: Literature

Cloche is a bHLH-PAS transcription factor that drives haemato-vascular specification

Nature - Wed, 07/13/2016 - 00:00

Cloche is a bHLH-PAS transcription factor that drives haemato-vascular specification

Nature 535, 7611 (2016). doi:10.1038/nature18614

Authors: Sven Reischauer, Oliver A. Stone, Alethia Villasenor, Neil Chi, Suk-Won Jin, Marcel Martin, Miler T. Lee, Nana Fukuda, Michele Marass, Alec Witty, Ian Fiddes, Taiyi Kuo, Won-Suk Chung, Sherveen Salek, Robert Lerrigo, Jessica Alsiö, Shujun Luo, Dominika Tworus, Sruthy M. Augustine, Sophie Mucenieks, Björn Nystedt, Antonio J. Giraldez, Gary P. Schroth, Olov Andersson & Didier Y. R. Stainier

Vascular and haematopoietic cells organize into specialized tissues during early embryogenesis to supply essential nutrients to all organs and thus play critical roles in development and disease. At the top of the haemato-vascular specification cascade lies cloche, a gene that when mutated in zebrafish leads to the striking phenotype of loss of most endothelial and haematopoietic cells and a significant increase in cardiomyocyte numbers. Although this mutant has been analysed extensively to investigate mesoderm diversification and differentiation and continues to be broadly used as a unique avascular model, the isolation of the cloche gene has been challenging due to its telomeric location. Here we used a deletion allele of cloche to identify several new cloche candidate genes within this genomic region, and systematically genome-edited each candidate. Through this comprehensive interrogation, we succeeded in isolating the cloche gene and discovered that it encodes a PAS-domain-containing bHLH transcription factor, and that it is expressed in a highly specific spatiotemporal pattern starting during late gastrulation. Gain-of-function experiments show that it can potently induce endothelial gene expression. Epistasis experiments reveal that it functions upstream of etv2 and tal1, the earliest expressed endothelial and haematopoietic transcription factor genes identified to date. A mammalian cloche orthologue can also rescue blood vessel formation in zebrafish cloche mutants, indicating a highly conserved role in vertebrate vasculogenesis and haematopoiesis. The identification of this master regulator of endothelial and haematopoietic fate enhances our understanding of early mesoderm diversification and may lead to improved protocols for the generation of endothelial and haematopoietic cells in vivo and in vitro.

Categories: Literature

Early myeloid lineage choice is not initiated by random PU.1 to GATA1 protein ratios

Nature - Wed, 07/13/2016 - 00:00

Early myeloid lineage choice is not initiated by random PU.1 to GATA1 protein ratios

Nature 535, 7611 (2016). doi:10.1038/nature18320

Authors: Philipp S. Hoppe, Michael Schwarzfischer, Dirk Loeffler, Konstantinos D. Kokkaliaris, Oliver Hilsenbeck, Nadine Moritz, Max Endele, Adam Filipczyk, Adriana Gambardella, Nouraiz Ahmed, Martin Etzrodt, Daniel L. Coutu, Michael A. Rieger, Carsten Marr, Michael K. Strasser, Bernhard Schauberger, Ingo Burtscher, Olga Ermakova, Antje Bürger, Heiko Lickert, Claus Nerlov, Fabian J. Theis & Timm Schroeder

The mechanisms underlying haematopoietic lineage decisions remain disputed. Lineage-affiliated transcription factors with the capacity for lineage reprogramming, positive auto-regulation and mutual inhibition have been described as being expressed in uncommitted cell populations. This led to the assumption that lineage choice is cell-intrinsically initiated and determined by stochastic switches of randomly fluctuating cross-antagonistic transcription factors. However, this hypothesis was developed on the basis of RNA expression data from snapshot and/or population-averaged analyses. Alternative models of lineage choice therefore cannot be excluded. Here we use novel reporter mouse lines and live imaging for continuous single-cell long-term quantification of the transcription factors GATA1 and PU.1 (also known as SPI1). We analyse individual haematopoietic stem cells throughout differentiation into megakaryocytic–erythroid and granulocytic–monocytic lineages. The observed expression dynamics are incompatible with the assumption that stochastic switching between PU.1 and GATA1 precedes and initiates megakaryocytic–erythroid versus granulocytic–monocytic lineage decision-making. Rather, our findings suggest that these transcription factors are only executing and reinforcing lineage choice once made. These results challenge the current prevailing model of early myeloid lineage choice.

Categories: Literature

Climate Change Has Shifted The World’s Cloud Cover Over Past 30 Years

Yale Environment 360 - Tue, 07/12/2016 - 10:16

Warming global temperatures have altered the distribution of clouds across the Earth in recent decades, according to new research published in the journal Nature.

Global cloud cover. Mid-latitude storm clouds have shifted polewards, dry subtropical zones have expanded in size, and the tops of clouds have gotten higher as a result of a warmer troposphere and cooler stratosphere, according to the study, which relied on satellite images taken between 1983 and 2009. Researchers said these shifts in cloud cover could further exacerbate climate change. As cloud systems shift toward the poles, where there’s less solar radiation, more sunlight will reach the Earth’s surface near the equator, boosting temperatures. Also, taller, thicker clouds trap more heat. “We now have a thicker blanket, which is also a warming effect,” said Joel Norris, a climate scientist at the Scripps Institution of Oceanography in San Diego who helped lead the study.

Categories: Environmental News

How Growing Sea Plants Can Help Slow Ocean Acidification

Yale Environment 360 - Tue, 07/12/2016 - 07:17

Researchers are finding that kelp, eelgrass, and other vegetation can effectively absorb CO2 and reduce acidity in the ocean. Growing these plants in local waters, scientists say, could help mitigate the damaging impacts of acidification on marine life. BY NICOLA JONES

Categories: Environmental News

How China is rewriting the book on human origins

Nature - Tue, 07/12/2016 - 00:00

How China is rewriting the book on human origins

Nature 535, 7611 (2016). http://www.nature.com/doifinder/10.1038/535218a

Author: Jane Qiu

Fossil finds in China are challenging ideas about the evolution of modern humans and our closest relatives.

Categories: Literature

Watch out for cheats in citation game

Nature - Tue, 07/12/2016 - 00:00

Watch out for cheats in citation game

Nature 535, 7611 (2016). http://www.nature.com/doifinder/10.1038/535201a

Author: Mario Biagioli

The focus on impact of published research has created new opportunities for misconduct and fraudsters, says Mario Biagioli.

Categories: Literature

Mobile-phone expansion could disrupt key weather satellites

Nature - Tue, 07/12/2016 - 00:00

Mobile-phone expansion could disrupt key weather satellites

Nature 535, 7611 (2016). http://www.nature.com/doifinder/10.1038/535208a

Author: Alexandra Witze

The US government is considering a plan to allow wireless firms to share radio frequencies used in weather forecasts.

Categories: Literature

Policy: Five cornerstones of a global bioeconomy

Nature - Tue, 07/12/2016 - 00:00

Policy: Five cornerstones of a global bioeconomy

Nature 535, 7611 (2016). doi:10.1038/535221a

Authors: Beate El-Chichakli, Joachim von Braun, Christine Lang, Daniel Barben & Jim Philp

Beate El-Chichakli and colleagues outline principles for coordinating bio-based industries to achieve many of the sustainable development goals.

Categories: Literature

Tax Credits Double ProjectionsOf Solar Growth in One U.S. Market

Yale Environment 360 - Mon, 07/11/2016 - 00:10

A new market report estimates that U.S. rooftop solar in the Mid-Atlantic region will likely increase exponentially over the next five years thanks to extended federal tax credits. The Business Energy Investment Tax Credit that Congress unexpectedly renewed last December gives homeowners and developers 30 percent back on solar panel installations and other renewable energy investments through 2019. The program could help solar installation growth in the Mid-Atlantic reach over 9,000 megawatts by 2021, doubling previous projections, according to the report, which was conducted by market research firm CreditSights. Such a jump would alleviate the need for U.S. power companies to subsidize electric needs with nuclear, natural gas, or coal during peak energy consumption periods. “If rooftop solar grows more than 30 percent, there’s no reason we couldn’t see electricity demand growth go negative in the coming years,” Greg Jones, a New York-based analyst with CreditSights, told Bloomberg News.

Categories: Environmental News

Engineering and mapping nanocavity emission via precision placement of DNA origami

Nature - Mon, 07/11/2016 - 00:00

Engineering and mapping nanocavity emission via precision placement of DNA origami

Nature 535, 7612 (2016). doi:10.1038/nature18287

Authors: Ashwin Gopinath, Evan Miyazono, Andrei Faraon & Paul W. K. Rothemund

Many hybrid devices integrate functional molecular or nanoparticle components with microstructures, as exemplified by the nanophotonic devices that couple emitters to optical resonators for potential use in single-molecule detection, precision magnetometry, low threshold lasing and quantum information processing. These systems also illustrate a common difficulty for hybrid devices: although many proof-of-principle devices exist, practical applications face the challenge of how to incorporate large numbers of chemically diverse functional components into microfabricated resonators at precise locations. Here we show that the directed self-assembly of DNA origami onto lithographically patterned binding sites allows reliable and controllable coupling of molecular emitters to photonic crystal cavities (PCCs). The precision of this method is sufficient to enable us to visualize the local density of states within PCCs by simple wide-field microscopy and to resolve the antinodes of the cavity mode at a resolution of about one-tenth of a wavelength. By simply changing the number of binding sites, we program the delivery of up to seven DNA origami onto distinct antinodes within a single cavity and thereby digitally vary the intensity of the cavity emission. To demonstrate the scalability of our technique, we fabricate 65,536 independently programmed PCCs on a single chip. These features, in combination with the widely used modularity of DNA origami, suggest that our method is well suited for the rapid prototyping of a broad array of hybrid nanophotonic devices.

Categories: Literature

Identification of proliferative and mature β-cells in the islets of Langerhans

Nature - Mon, 07/11/2016 - 00:00

Identification of proliferative and mature β-cells in the islets of Langerhans

Nature 535, 7612 (2016). doi:10.1038/nature18624

Authors: Erik Bader, Adriana Migliorini, Moritz Gegg, Noah Moruzzi, Jantje Gerdes, Sara S. Roscioni, Mostafa Bakhti, Elisabeth Brandl, Martin Irmler, Johannes Beckers, Michaela Aichler, Annette Feuchtinger, Christin Leitzinger, Hans Zischka, Rui Wang-Sattler, Martin Jastroch, Matthias Tschöp, Fausto Machicao, Harald Staiger, Hans-Ulrich Häring, Helena Chmelova, Julie A. Chouinard, Nikolay Oskolkov, Olle Korsgren, Stephan Speier & Heiko Lickert

Insulin-dependent diabetes is a complex multifactorial disorder characterized by loss or dysfunction of β-cells. Pancreatic β-cells differ in size, glucose responsiveness, insulin secretion and precursor cell potential; understanding the mechanisms that underlie this functional heterogeneity might make it possible to develop new regenerative approaches. Here we show that Fltp (also known as Flattop and Cfap126), a Wnt/planar cell polarity (PCP) effector and reporter gene, acts as a marker gene that subdivides endocrine cells into two subpopulations and distinguishes proliferation-competent from mature β-cells with distinct molecular, physiological and ultrastructural features. Genetic lineage tracing revealed that endocrine subpopulations from Fltp-negative and -positive lineages react differently to physiological and pathological changes. The expression of Fltp increases when endocrine cells cluster together to form polarized and mature 3D islet mini-organs. We show that 3D architecture and Wnt/PCP ligands are sufficient to trigger β-cell maturation. By contrast, the Wnt/PCP effector Fltp is not necessary for β-cell development, proliferation or maturation. We conclude that 3D architecture and Wnt/PCP signalling underlie functional β-cell heterogeneity and induce β-cell maturation. The identification of Fltp as a marker for endocrine subpopulations sheds light on the molecular underpinnings of islet cell heterogeneity and plasticity and might enable targeting of endocrine subpopulations for the regeneration of functional β-cell mass in diabetic patients.

Categories: Literature

Hundreds of Deaths in 2003 Heat Wave Linked to Climate Change

Yale Environment 360 - Fri, 07/08/2016 - 01:16

A new study suggests that human-caused climate change could be responsible for a significant portion of the 70,000 deaths that occurred during the record-breaking 2003 European heat wave. The research, published in the journal Environmental Research Letters, combined climate modeling with health data for hundreds of fatalities that summer. Climate change, the study found, increased the likelihood of heat-related losses by nearly 70 percent in Paris and 20 percent in London. Out of 735 heat-related deaths in Paris, 506 were attributable to global warming, as were 64 out of 315 deaths in London. "Until recently, whenever we talked about climate change we talked about the globally averaged increase in temperature of 1 degree and people just don't really know or frankly care about that," lead study author and Oxford University scientist Daniel Mitchell told InsideClimate News. "But now… people can really start to understand that these are impacts we're seeing now, not in the future."

Categories: Environmental News

Beat it, impact factor! Publishing elite turns against controversial metric

Nature - Fri, 07/08/2016 - 00:00

Beat it, impact factor! Publishing elite turns against controversial metric

Nature 535, 7611 (2016). http://www.nature.com/doifinder/10.1038/nature.2016.20224

Author: Ewen Callaway

Senior staff at leading journals want to end inappropriate use of the measure.

Categories: Literature

California’s Redwood Trees Are Best in the World at Storing CO2

Yale Environment 360 - Thu, 07/07/2016 - 11:42

California’s ancient redwood trees store more carbon dioxide per acre than any other forest in the world, including tropical rain forests like the Amazon, according to new research published in the journal Forest Ecology and Management.

California redwood trees. The findings are the result of a seven-year study by scientists at Humboldt University and the University of Washington. Redwoods store 2,600 metric tons of carbon per hectare (2.4 acres), more than double the absorption rate of the Pacific Northwest’s conifer trees or Australia’s eucalyptus forests, the study found. The main reason redwoods surpass all others in CO2 storage is their longevity, the scientists said. "The story of carbon is huge," Robert Van Pelt, a scientist at Humboldt State University and co-author of the research, told The Mercury News. "The carbon part of a redwood may be more important than the lumber part in the coming decades."

Categories: Environmental News

Vanishing Act: What’s Causing Sharp Decline in Insects and Why It Matters

Yale Environment 360 - Wed, 07/06/2016 - 07:38

Insect populations are declining dramatically in many parts of the world, recent studies show. Researchers say various factors, from monoculture farming to habitat loss, are to blame for the plight of insects, which are essential to agriculture and ecosystems. BY CHRISTIAN SCHWäGERL

Categories: Environmental News

As Oceans Become More Acidic,Mussels Could Lose Ability to Hang On

Yale Environment 360 - Wed, 07/06/2016 - 01:06

Rising carbon dioxide emissions have caused the world’s oceans to become 30 percent more acidic since the Industrial Revolution, affecting everything from marine life’s ability to build shells

Trossulus byssus mussels. to the pH level of fishes’ blood. Now, scientists have discovered that more acidic water also prevents mussels from attaching to rocks and other surfaces, which could have ramifications on the global food chain, the economy, and ecosystem health. Oceans today have a pH of about 8.1. When the pH drops below 7.6, the adhesive plaque that cements mussels to hard surfaces becomes weaker, according to the new research by scientists at the University of Washington. Unattached mussels are easy prey for predators like crabs, fish, and sea stars. Mussels play an important role in filtering pollutants from waterways. They are also a critical food source for coastal communities, with the industry worth an estimated $1.4 billion.

Categories: Environmental News

Molecular biology: A surprise beginning for RNA

Nature - Wed, 07/06/2016 - 00:00

Molecular biology: A surprise beginning for RNA

Nature 535, 7612 (2016). doi:10.1038/nature18908

Authors: Katharina Höfer & Andres Jäschke

Organic molecules called coenzymes are central to metabolism, but have also been found to act as components of RNA in bacteria. A study reveals how coenzymes are incorporated into RNA. See Letter p.444

Categories: Literature

The mechanism of RNA 5′ capping with NAD+, NADH and desphospho-CoA

Nature - Wed, 07/06/2016 - 00:00

The mechanism of RNA 5′ capping with NAD+, NADH and desphospho-CoA

Nature 535, 7612 (2016). doi:10.1038/nature18622

Authors: Jeremy G. Bird, Yu Zhang, Yuan Tian, Natalya Panova, Ivan Barvík, Landon Greene, Min Liu, Brian Buckley, Libor Krásný, Jeehiun K. Lee, Craig D. Kaplan, Richard H. Ebright & Bryce E. Nickels

The chemical nature of the 5′ end of RNA is a key determinant of RNA stability, processing, localization and translation efficiency, and has been proposed to provide a layer of ‘epitranscriptomic’ gene regulation. Recently it has been shown that some bacterial RNA species carry a 5′-end structure reminiscent of the 5′ 7-methylguanylate ‘cap’ in eukaryotic RNA. In particular, RNA species containing a 5′-end nicotinamide adenine dinucleotide (NAD+) or 3′-desphospho-coenzyme A (dpCoA) have been identified in both Gram-negative and Gram-positive bacteria. It has been proposed that NAD+, reduced NAD+ (NADH) and dpCoA caps are added to RNA after transcription initiation, in a manner analogous to the addition of 7-methylguanylate caps. Here we show instead that NAD+, NADH and dpCoA are incorporated into RNA during transcription initiation, by serving as non-canonical initiating nucleotides (NCINs) for de novo transcription initiation by cellular RNA polymerase (RNAP). We further show that both bacterial RNAP and eukaryotic RNAP II incorporate NCIN caps, that promoter DNA sequences at and upstream of the transcription start site determine the efficiency of NCIN capping, that NCIN capping occurs in vivo, and that NCIN capping has functional consequences. We report crystal structures of transcription initiation complexes containing NCIN-capped RNA products. Our results define the mechanism and structural basis of NCIN capping, and suggest that NCIN-mediated ‘ab initio capping’ may occur in all organisms.

Categories: Literature

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