#1 Mapping tree density at a global scale Link logo

Crowther, T. W.; Glick, H. B.; Covey, K. R.; Bettigole, C.; Maynard, D. S.; Thomas, S. M.; Smith, J. R.; Hintler, G.; Duguid, M. C.; Amatulli, G.; Tuanmu, M. -N.; Jetz, W.; Salas, C.; Stam, C.; Piotto, D.; Tavani, R.; Green, S.; Bruce, G.; Williams, S. J.

Nature Volume 525, Issue 7568, Pages 201–205

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The global extent and distribution of forest trees is central to our understanding of the terrestrial biosphere. We provide the first spatially continuous map of forest tree density at a global scale. This map reveals that the global number of trees is approximately 3.04 trillion, an order of magnitude higher than the previous estimate. Of these trees, approximately 1.39 trillion exist in tropical and subtropical forests, with 0.74 trillion in boreal regions and 0.61 trillion in temperate regions. Biome-level trends in tree density demonstrate the importance of climate and topography in controlling local tree densities at finer scales, as well as the overwhelming effect of humans across most of the world. Based on our projected tree densities, we estimate that over 15 billion trees are cut down each year, and the global number of trees has fallen by approximately 46% since the start of human civilization.

#2 Combined Measurement of the Higgs Boson Mass in pp Collisions at root s=7 and 8 TeV with the ATLAS and CMS Experiments PDF logo

Aad G. et al. (ATLAS Collaboration;CMS Collaboration);Abbott B. Abdallah J. Abdinov O. Aben R. Abolins M. AbouZeid O. S. Abramowicz H. Abreu H. Abreu R. Abulaiti Y. Acharya B. S. Adamczyk L. Adams D. L. Adelman J. Adomeit S. Adye T. Affolder A. A. Agatonovic-Jovin T.

Physical Review Letters Volume 114, Issue 19

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A measurement of the Higgs boson mass is presented based on the combined data samples of the ATLAS and CMS experiments at the CERN LHC in the H→γγ and H→ZZ→4ℓ decay channels. The results are obtained from a simultaneous fit to the reconstructed invariant mass peaks in the two channels and for the two experiments. The measured masses from the individual channels and the two experiments are found to be consistent among themselves. The combined measured mass of the Higgs boson is m_{H}=125.09±0.21 (stat)±0.11 (syst) GeV.

#3 Joint Analysis of BICEP2/Keck Array and Planck Data Link logo PDF logo

Ade, P. A. R.; Aghanim, N.; Ahmed, Z.; Aikin, R. W.; Alexander, K. D.; Arnaud, M.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barkats, D.; Barreiro, R. B.; Bartlett, J. G.; Bartolo, N.; Battaner, E.; Benabed, K.; Benoit, A.; Benoit-Levy, A.; Benton, S. J

Physical Review Letters Volume 114, Issue 10

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We report the results of a joint analysis of data from BICEP2/Keck Array and Planck. BICEP2 and Keck Array have observed the same approximately 400  deg^{2} patch of sky centered on RA 0 h, Dec. -57.5°. The combined maps reach a depth of 57 nK deg in Stokes Q and U in a band centered at 150 GHz. Planck has observed the full sky in polarization at seven frequencies from 30 to 353 GHz, but much less deeply in any given region (1.2  μK deg in Q and U at 143 GHz). We detect 150×353 cross-correlation in B modes at high significance. We fit the single- and cross-frequency power spectra at frequencies ≥150  GHz to a lensed-ΛCDM model that includes dust and a possible contribution from inflationary gravitational waves (as parametrized by the tensor-to-scalar ratio r), using a prior on the frequency spectral behavior of polarized dust emission from previous Planck analysis of other regions of the sky. We find strong evidence for dust and no statistically significant evidence for tensor modes. We probe various model variations and extensions, including adding a synchrotron component in combination with lower frequency data, and find that these make little difference to the r constraint. Finally, we present an alternative analysis which is similar to a map-based cleaning of the dust contribution, and show that this gives similar constraints. The final result is expressed as a likelihood curve for r, and yields an upper limit r_{0.05}<0.12 at 95% confidence. Marginalizing over dust and r, lensing B modes are detected at 7.0σ significance.

#4 Rapid and highly variable warming of lake surface waters around the globe Open access logo Link logo PDF logo

O'Reilly Catherine M., Sharma Sapna, Gray Derek K., Hampton Stephanie E., Read Jordan S., Rowley Rex J., Schneider Philipp, Lenters John D., McIntyre Peter B., Kraemer Benjamin M., Weyhenmeyer Gesa A., Straile Dietmar, Dong Bo, Adrian Rita, Allan Mathew G., Anneville Orlane, Arvola Lauri, Austin Jay, Bailey John L., Baron Jill S. et.al.

Geophysical Research Letters Volume 42, Issue 24, Pages 10,773–10,781

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#5 Observation of the rare B<sub>s</sub><sup>0</sup> →µ<sup>+</sup>µ<sup>−</sup>  decay from the combined analysis of CMS and LHCb data Link logo PDF logo

Khatchatryan, V.; Eerola, P.; Fedi, G.; Voutilainen, Mikko; Härkönen, J.; Karimäki, V.; Kinnunen, Ritva; Kortelainen, M. J.; Lampén, Pekka Tapio; Lassila-Perini, K.; Lehti, Sami; Lindén, T.; Luukka, P.; Mäenpää, Teppo; Peltola, Timo; Tuominen, Eija; Tuomi

Nature Volume 522, Issue 7554, Pages 68–72

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The standard model of particle physics describes the fundamental particles and their interactions via the strong, electromagnetic and weak forces. It provides precise predictions for measurable quantities that can be tested experimentally. The probabilities, or branching fractions, of the strange B meson () and the B(0) meson decaying into two oppositely charged muons (μ(+) and μ(-)) are especially interesting because of their sensitivity to theories that extend the standard model. The standard model predicts that the and decays are very rare, with about four of the former occurring for every billion mesons produced, and one of the latter occurring for every ten billion B(0) mesons. A difference in the observed branching fractions with respect to the predictions of the standard model would provide a direction in which the standard model should be extended. Before the Large Hadron Collider (LHC) at CERN started operating, no evidence for either decay mode had been found. Upper limits on the branching fractions were an order of magnitude above the standard model predictions. The CMS (Compact Muon Solenoid) and LHCb (Large Hadron Collider beauty) collaborations have performed a joint analysis of the data from proton-proton collisions that they collected in 2011 at a centre-of-mass energy of seven teraelectronvolts and in 2012 at eight teraelectronvolts. Here we report the first observation of the µ(+)µ(-) decay, with a statistical significance exceeding six standard deviations, and the best measurement so far of its branching fraction. Furthermore, we obtained evidence for the µ(+)µ(-) decay with a statistical significance of three standard deviations. Both measurements are statistically compatible with standard model predictions and allow stringent constraints to be placed on theories beyond the standard model. The LHC experiments will resume taking data in 2015, recording proton-proton collisions at a centre-of-mass energy of 13 teraelectronvolts, which will approximately double the production rates of and B(0) mesons and lead to further improvements in the precision of these crucial tests of the standard model.

#6 Planck intermediate results. XIX. An overview of the polarized thermal emission from Galactic dust Link logo PDF logo

Ade, P. A. R.; Aghanim, N.; Alina, D.; Alves, M. I. R.; Armitage-Caplan, C.; Amaue, M.; Arzoumanian, D.; Ashdown, M.; Atrio-Barandela, F.; Aumont, J.; Baccigalupi, C.; Banda, A. J.; Barreiro, R. B.; Battaner, E.; Benabed, K.; Benoit-Levy, A.; Bernard, J.


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#7 DNA rendering of polyhedral meshes at the nanoscale Link logo

Benson, Erik; Mohammed, Abdulmelik; Gardell, Johan; Masich, Sergej; Czeizler, Eugen; Orponen, Pekka; Högberg, Björn

Nature Volume 523, Issue 7561, Pages 441–444

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It was suggested more than thirty years ago that Watson-Crick base pairing might be used for the rational design of nanometre-scale structures from nucleic acids. Since then, and especially since the introduction of the origami technique, DNA nanotechnology has enabled increasingly more complex structures. But although general approaches for creating DNA origami polygonal meshes and design software are available, there are still important constraints arising from DNA geometry and sense/antisense pairing, necessitating some manual adjustment during the design process. Here we present a general method of folding arbitrary polygonal digital meshes in DNA that readily produces structures that would be very difficult to realize using previous approaches. The design process is highly automated, using a routeing algorithm based on graph theory and a relaxation simulation that traces scaffold strands through the target structures. Moreover, unlike conventional origami designs built from close-packed helices, our structures have a more open conformation with one helix per edge and are therefore stable under the ionic conditions usually used in biological assays.

#8 Holocene shifts in the assembly of plant and animal communities implicate human impacts

Lyons, S.K.; Amatangelo, K.L; Behrensmeyer, A.K.; Bercovici, A.; Blois, J.L.; Davis, M.; DiMichele, W.A.; Du, A.; Eronen, Jussi Tuomas; Faith, J.T.; Graves, G.R.; Jud, N.; Labandeira, C.; Looy, C.V.; McGill, B.; Miller, J.H.; Patterson, D.; Pineda-Munoz,

Nature Volume 529, Issue 7584, Pages 80–83

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Understanding how ecological communities are organized and how they change through time is critical to predicting the effects of climate change. Recent work documenting the co-occurrence structure of modern communities found that most significant species pairs co-occur less frequently than would be expected by chance. However, little is known about how co-occurrence structure changes through time. Here we evaluate changes in plant and animal community organization over geological time by quantifying the co-occurrence structure of 359,896 unique taxon pairs in 80 assemblages spanning the past 300 million years. Co-occurrences of most taxon pairs were statistically random, but a significant fraction were spatially aggregated or segregated. Aggregated pairs dominated from the Carboniferous period (307 million years ago) to the early Holocene epoch (11,700 years before present), when there was a pronounced shift to more segregated pairs, a trend that continues in modern assemblages. The shift began during the Holocene and coincided with increasing human population size and the spread of agriculture in North America. Before the shift, an average of 64% of significant pairs were aggregated; after the shift, the average dropped to 37%. The organization of modern and late Holocene plant and animal assemblages differs fundamentally from that of assemblages over the past 300 million years that predate the large-scale impacts of humans. Our results suggest that the rules governing the assembly of communities have recently been changed by human activity.

#9 A new extant family of primitive moths from Kangaroo Island, Australia, and its significance for understanding early Lepidoptera evolution PDF logo

Niels P. Kristensen, Douglas J. Hilton, Axel Kallies, Liz Milla, Jadranka Rota, Niklas Wahlberg, Stephen A. Wilcox, Richard V. Glatz, David A. Young, Glenn Cocking, Ted Edwards, George W. Gibbs, Mike Halsey

Systematic Entomology Volume 40, Issue 1, Pages 5–16

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#10 Palaeomagnetic field intensity variations suggest Mesoproterozoic inner-core nucleation Link logo

Biggin, Andrew John; Piispa, Elisa; Pesonen, Lauri Juhani; Holme, Richard; Paterson, Greig; Veikkolainen, Toni Henri Kristian; Tauxe, Lisa

Nature Volume 526, Issue 7572, Pages 245–248

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The Earth's inner core grows by the freezing of liquid iron at its surface. The point in history at which this process initiated marks a step-change in the thermal evolution of the planet. Recent computational and experimental studies have presented radically differing estimates of the thermal conductivity of the Earth's core, resulting in estimates of the timing of inner-core nucleation ranging from less than half a billion to nearly two billion years ago. Recent inner-core nucleation (high thermal conductivity) requires high outer-core temperatures in the early Earth that complicate models of thermal evolution. The nucleation of the core leads to a different convective regime and potentially different magnetic field structures that produce an observable signal in the palaeomagnetic record and allow the date of inner-core nucleation to be estimated directly. Previous studies searching for this signature have been hampered by the paucity of palaeomagnetic intensity measurements, by the lack of an effective means of assessing their reliability, and by shorter-timescale geomagnetic variations. Here we examine results from an expanded Precambrian database of palaeomagnetic intensity measurements selected using a new set of reliability criteria. Our analysis provides intensity-based support for the dominant dipolarity of the time-averaged Precambrian field, a crucial requirement for palaeomagnetic reconstructions of continents. We also present firm evidence for the existence of very long-term variations in geomagnetic strength. The most prominent and robust transition in the record is an increase in both average field strength and variability that is observed to occur between a billion and 1.5 billion years ago. This observation is most readily explained by the nucleation of the inner core occurring during this interval; the timing would tend to favour a modest value of core thermal conductivity and supports a simple thermal evolution model for the Earth.

#11 Birth of a comet magnetosphere:A spring of water ions Link logo PDF logo

Nilsson, Hans; Wieser, Gabriella Stenberg; Behar, Etienne; Wedlund, Cyril Simon; Gunell, Herbert; Yamauchi, Masatoshi; Lundin, Rickard; Barabash, Stas; Wieser, Martin; Carr, Chris; Cupido, Emanuele; Burch, James L.; Fedorov, Andrei; Sauvaud, Jean-Andre; K

Science Volume 347, Issue 6220

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The Rosetta mission shall accompany comet 67P/Churyumov-Gerasimenko from a heliocentric distance of >3.6 astronomical units through perihelion passage at 1.25 astronomical units, spanning low and maximum activity levels. Initially, the solar wind permeates the thin comet atmosphere formed from sublimation, until the size and plasma pressure of the ionized atmosphere define its boundaries: A magnetosphere is born. Using the Rosetta Plasma Consortium ion composition analyzer, we trace the evolution from the first detection of water ions to when the atmosphere begins repelling the solar wind (~3.3 astronomical units), and we report the spatial structure of this early interaction. The near-comet water population comprises accelerated ions (<800 electron volts), produced upstream of Rosetta, and lower energy locally produced ions; we estimate the fluxes of both ion species and energetic neutral atoms.

#12 Precision measurement of the mass difference between light nuclei and anti-nuclei Open access logo Link logo PDF logo

ALICE Collaboration;Chang, BeomSu;Kim, Dong Jo;Kral, Jiri;Rak, Jan;Räsänen, Sami;Slupecki, Maciej;Snellman, Tomas;Trzaska, Wladyslaw;Vargyas, Márton;Viinikainen, Jussi

Nature Physics Volume 11, Issue 10, Pages 811–814

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