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  • 1. Abdo, A. A.
    et al.
    Ackermann, M.
    Ajello, M.
    Asano, K.
    Atwood, W. B.
    Axelsson, M.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Baldini, L.
    Ballet, J.
    Barbiellini, G.
    Baring, M. G.
    Bastieri, D.
    Bechtol, K.
    Bellazzini, R.
    Berenji, B.
    Bhat, P. N.
    Bissaldi, E.
    Bloom, E. D.
    Bonamente, E.
    Bonnell, J.
    Borgland, A. W.
    Bouvier, A.
    Bregeon, J.
    Brez, A.
    Briggs, M. S.
    Brigida, M.
    Bruel, P.
    Burgess, J. M.
    Burnett, T. H.
    Caliandro, G. A.
    Cameron, R. A.
    Caraveo, P. A.
    Casandjian, J. M.
    Cecchi, C.
    Çelik, Ö.
    Chaplin, V.
    Charles, E.
    Cheung, C. C.
    Chiang, J.
    Ciprini, S.
    Claus, R.
    Cohen-Tanugi, J.
    Cominsky, L. R.
    Connaughton, V.
    Conrad, J.
    Stockholm University, Faculty of Science, Department of Physics.
    Cutini, S.
    Dermer, C. D.
    de Angelis, A.
    de Palma, F.
    Digel, S. W.
    Dingus, B. L.
    Do Couto E Silva, E.
    Drell, P. S.
    Dubois, R.
    Dumora, D.
    Farnier, C.
    Favuzzi, C.
    Fegan, S. J.
    Finke, J.
    Fishman, G.
    Focke, W. B.
    Foschini, L.
    Fukazawa, Y.
    Funk, S.
    Fusco, P.
    Gargano, F.
    Gasparrini, D.
    Gehrels, N.
    Germani, S.
    Gibby, L.
    Giebels, B.
    Giglietto, N.
    Giordano, F.
    Glanzman, T.
    Godfrey, G.
    Granot, J.
    Greiner, J.
    Grenier, I. A.
    Grondin, M.-H.
    Grove, J. E.
    Grupe, D.
    Guillemot, L.
    Guiriec, S.
    Hanabata, Y.
    Harding, A. K.
    Hayashida, M.
    Hays, E.
    Hoversten, E. A.
    Hughes, R. E.
    Jóhannesson, G.
    Johnson, A. S.
    Johnson, R. P.
    Johnson, W. N.
    Kamae, T.
    Katagiri, H.
    Kataoka, J.
    Kawai, N.
    Kerr, M.
    Kippen, R. M.
    Knödlseder, J.
    Kocevski, D.
    Kouveliotou, C.
    Kuehn, F.
    Kuss, M.
    Lande, J.
    Latronico, L.
    Lemoine-Goumard, M.
    Longo, F.
    Loparco, F.
    Lott, B.
    Lovellette, M. N.
    Lubrano, P.
    Madejski, G. M.
    Makeev, A.
    Mazziotta, M. N.
    McBreen, S.
    McEnery, J. E.
    McGlynn, S.
    Mészáros, P.
    Meurer, C.
    Michelson, P. F.
    Mitthumsiri, W.
    Mizuno, T.
    Moiseev, A. A.
    Monte, C.
    Monzani, M. E.
    Moretti, E.
    Morselli, A.
    Moskalenko, I. V.
    Murgia, S.
    Nakamori, T.
    Nolan, P. L.
    Norris, J. P.
    Nuss, E.
    Ohno, M.
    Ohsugi, T.
    Omodei, N.
    Orlando, E.
    Ormes, J. F.
    Ozaki, M.
    Paciesas, W. S.
    Paneque, D.
    Panetta, J. H.
    Parent, D.
    Pelassa, V.
    Pepe, M.
    Pesce-Rollins, M.
    Petrosian, V.
    Piron, F.
    Porter, T. A.
    Preece, R.
    Rainò, S.
    Ramirez-Ruiz, E.
    Rando, R.
    Razzano, M.
    Razzaque, S.
    Reimer, A.
    Reimer, O.
    Reposeur, T.
    Ritz, S.
    Rochester, L. S.
    Rodriguez, A. Y.
    Roth, M.
    Ryde, F.
    Sadrozinski, H. F.-W.
    Sanchez, D.
    Sander, A.
    Saz Parkinson, P. M.
    Scargle, J. D.
    Schalk, T. L.
    Sgrò, C.
    Siskind, E. J.
    Smith, D. A.
    Smith, P. D.
    Spandre, G.
    Spinelli, P.
    Stamatikos, M.
    Stecker, F. W.
    Strickman, M. S.
    Suson, D. J.
    Tajima, H.
    Takahashi, H.
    Takahashi, T.
    Tanaka, T.
    Thayer, J. B.
    Thayer, J. G.
    Thompson, D. J.
    Tibaldo, L.
    Toma, K.
    Torres, D. F.
    Tosti, G.
    Troja, E.
    Uchiyama, Y.
    Uehara, T.
    Usher, T. L.
    van der Horst, A. J.
    Vasileiou, V.
    Vilchez, N.
    Vitale, V.
    von Kienlin, A.
    Waite, A. P.
    Wang, P.
    Wilson-Hodge, C.
    Winer, B. L.
    Wood, K. S.
    Wu, X. F.
    Yamazaki, R.
    Ylinen, T.
    Ziegler, M.
    the Fermi LAT Collaboration,
    A limit on the variation of the speed of light arising from quantum gravity effects2009In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 462, no 7271, p. 331-334Article in journal (Refereed)
    Abstract [en]

    A cornerstone of Einstein’s special relativity is Lorentz invariance—the postulate that all observers measure exactly the same speed of light in vacuum, independent of photon-energy. While special relativity assumes that there is no fundamental length-scale associated with such invariance, there is a fundamental scale (the Planck scale, lPlanck~1.62×10-33cm or EPlanck = MPlanckc2~1.22×1019GeV), at which quantum effects are expected to strongly affect the nature of space–time. There is great interest in the (not yet validated) idea that Lorentz invariance might break near the Planck scale. A key test of such violation of Lorentz invariance is a possible variation of photon speed with energy. Even a tiny variation in photon speed, when accumulated over cosmological light-travel times, may be revealed by observing sharp features in γ-ray burst (GRB) light-curves. Here we report the detection of emission up to ~31GeV from the distant and short GRB090510. We find no evidence for the violation of Lorentz invariance, and place a lower limit of 1.2EPlanck on the scale of a linear energy dependence (or an inverse wavelength dependence), subject to reasonable assumptions about the emission (equivalently we have an upper limit of lPlanck/1.2 on the length scale of the effect). Our results disfavour quantum-gravity theories in which the quantum nature of space–time on a very small scale linearly alters the speed of light.

  • 2. Abramowski, A.
    et al.
    Aharonian, F.
    Benkhali, F. Ait
    Akhperjanian, A. G.
    Anguener, E. O.
    Backes, M.
    Balzer, A.
    Becherini, Y.
    Tjus, J. Becker
    Berge, D.
    Bernhard, S.
    Bernloehr, K.
    Birsin, E.
    Blackwell, R.
    Boettcher, M.
    Boisson, C.
    Bolmont, J.
    Bordas, P.
    Bregeon, J.
    Brun, F.
    Brun, P.
    Bryan, M.
    Bulik, T.
    Carr, J.
    Casanova, S.
    Chakraborty, N.
    Chalme-Calvet, R.
    Chaves, R. C. G.
    Chen, A.
    Chretien, M.
    Colafrancesco, S.
    Cologna, G.
    Conrad, Jan
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Couturier, C.
    Cui, Y.
    Davids, I. D.
    Degrange, B.
    Deil, C.
    deWilt, P.
    Djannati-Ata, A.
    Domainko, W.
    Donath, A.
    Drury, L. O'C.
    Dubus, G.
    Dutson, K.
    Dyks, J.
    Dyrda, M.
    Edwards, T.
    Egberts, K.
    Eger, P.
    Ernenwein, J-P.
    Espigat, P.
    Farnier, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Fegan, S.
    Feinstein, F.
    Fernandes, M. V.
    Fernandez, D.
    Fiasson, A.
    Fontaine, G.
    Foerster, A.
    Fuessling, M.
    Gabici, S.
    Gajdus, M.
    Gallant, Y. A.
    Garrigoux, T.
    Giavitto, G.
    Giebels, B.
    Glicenstein, J. F.
    Gottschall, D.
    Goyal, A.
    Grondin, M-H.
    Grudzinska, M.
    Hadasch, D.
    Haeffner, S.
    Hahn, J.
    Hawkes, J.
    Heinzelmann, G.
    Henri, G.
    Hermann, G.
    Hervet, O.
    Hillert, A.
    Hinton, J. A.
    Hofmann, W.
    Hofverberg, P.
    Hoischen, C.
    Holler, M.
    Horns, D.
    Ivascenko, A.
    Jacholkowska, A.
    Jamrozy, M.
    Janiak, M.
    Jankowsky, F.
    Jung-Richardt, I.
    Kastendieck, M. A.
    Katarzynski, K.
    Katz, U.
    Kerszberg, D.
    Khelifi, B.
    Kieffer, M.
    Klepser, S.
    Klochkov, D.
    Kluzniak, W.
    Kolitzus, D.
    Komin, Nu.
    Kosack, K.
    Krakau, S.
    Krayzel, F.
    Krueger, P. P.
    Laffon, H.
    Lamanna, G.
    Lau, J.
    Lefaucheur, J.
    Lefranc, V.
    Lemiere, A.
    Lemoine-Goumard, M.
    Lenain, J-P.
    Lohse, T.
    Lopatin, A.
    Lu, C-C.
    Lui, R.
    Marandon, V.
    Marcowith, A.
    Mariaud, C.
    Marx, R.
    Maurin, G.
    Maxted, N.
    Mayer, M.
    Meintjes, P. J.
    Menzler, U.
    Meyer, Manuel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Mitchell, A. M. W.
    Moderski, R.
    Mohamed, M.
    Morå, Knut
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Moulin, E.
    Murach, T.
    de Naurois, M.
    Niemiec, J.
    Oakes, L.
    Odaka, H.
    Oettl, S.
    Ohm, S.
    Opitz, B.
    Ostrowski, M.
    Oya, I.
    Panter, M.
    Parsons, R. D.
    Arribas, M. Paz
    Pekeur, N. W.
    Pelletier, G.
    Petrucci, P-O.
    Peyaud, B.
    Pita, S.
    Poon, H.
    Prokoph, H.
    Puehlhofer, G.
    Punch, M.
    Quirrenbach, A.
    Raab, S.
    Reichardt, I.
    Reimer, A.
    Reimer, O.
    Renaud, M.
    de los Reyes, R.
    Rieger, F.
    Romoli, C.
    Rosier-Lees, S.
    Rowell, G.
    Rudak, B.
    Rulten, C. B.
    Sahakian, V.
    Salek, D.
    Sanchez, D. A.
    Santangelo, A.
    Sasaki, M.
    Schlickeiser, R.
    Schuessler, F.
    Schulz, A.
    Schwanke, U.
    Schwemmer, S.
    Seyffert, A. S.
    Simoni, R.
    Sol, H.
    Spanier, F.
    Spengler, Gerrit
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Spies, F.
    Stawarz, L.
    Steenkamp, R.
    Stegmann, C.
    Stinzing, F.
    Stycz, K.
    Sushch, I.
    Tavernet, J-P.
    Tavernier, T.
    Taylor, A. M.
    Terrier, R.
    Tluczykont, M.
    Trichard, C.
    Tuffs, R.
    Valerius, K.
    van der Walt, J.
    van Eldik, C.
    van Soelen, B.
    Vasileiadis, G.
    Veh, J.
    Venter, C.
    Viana, A.
    Vincent, P.
    Vink, J.
    Voisin, F.
    Voelk, H. J.
    Vuillaume, T.
    Wagner, S. J.
    Wagner, P.
    Wagner, Roger M.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Weidinger, M.
    Weitzel, Q.
    White, R.
    Wierzcholska, A.
    Willmann, P.
    Woernlein, A.
    Wouters, D.
    Yang, R.
    Zabalza, V.
    Zaborov, D.
    Zacharias, M.
    Zdziarski, A. A.
    Zech, A.
    Zefi, F.
    Zywucka, N.
    Acceleration of petaelectronvolt protons in the Galactic Centre2016In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 531, no 7595, p. 476-+Article in journal (Refereed)
    Abstract [en]

    Galactic cosmic rays reach energies of at least a few petaelectronvolts(1) (of the order of 1015 electronvolts). This implies that our Galaxy contains petaelectronvolt accelerators ('PeVatrons'), but all proposed models of Galactic cosmic-ray accelerators encounter difficulties at exactly these energies(2). Dozens of Galactic accelerators capable of accelerating particles to energies of tens of teraelectronvolts (of the order of 10(13) electronvolts) were inferred from recent gamma-ray observations(3). However, none of the currently known accelerators-not even the handful of shell-type supernova remnants commonly believed to supply most Galactic cosmic rays-has shown the characteristic tracers of petaelectronvolt particles, namely, power-law spectra of.-rays extending without a cut-off or a spectral break to tens of teraelectronvolts(4). Here we report deep.-ray observations with arcminute angular resolution of the region surrounding the Galactic Centre, which show the expected tracer of the presence of petaelectronvolt protons within the central 10 parsecs of the Galaxy. We propose that the supermassive black hole Sagittarius A* is linked to this PeVatron. Sagittarius A* went through active phases in the past, as demonstrated by X-ray outbursts(5) and an outflow from the Galactic Centre(6). Although its current rate of particle acceleration is not sufficient to provide a substantial contribution to Galactic cosmic rays, Sagittarius A* could have plausibly been more active over the last 10(6)-10(7) years, and therefore should be considered as a viable alternative to supernova remnants as a source of petaelectronvolt Galactic cosmic rays.

  • 3. Aharonian, Felix
    et al.
    Akamatsu, Hiroki
    Akimoto, Fumie
    Allen, Steven W.
    Angelini, Lorella
    Audard, Marc
    Awaki, Hisamitsu
    Axelsson, Magnus
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Bamba, Aya
    Bautz, Marshall W.
    Blandford, Roger
    Brenneman, Laura W.
    Brown, Gregory V.
    Bulbul, Esra
    Cackett, Edward M.
    Chernyakova, Maria
    Chiao, Meng P.
    Coppi, Paolo S.
    Costantini, Elisa
    De Plaa, Jelle
    den Herder, Jan-Willem
    Done, Chris
    Dotani, Tadayasu
    Ebisawa, Ken
    Eckart, Megan E.
    Enoto, Teruaki
    Ezoe, Yuichiro
    Fabian, Andrew C.
    Ferrigno, Carlo
    Foster, Adam R.
    Fujimoto, Ryuichi
    Fukazawa, Yasushi
    Furuzawa, Akihiro
    Galeazzi, Massimiliano
    Gallo, Luigi C.
    Gandhi, Poshak
    Giustini, Margherita
    Goldwurm, Andrea
    Gu, Liyi
    Guainazzi, Matteo
    Haba, Yoshito
    Hagino, Kouichi
    Hamaguchi, Kenji
    Harrus, Ilana M.
    Hatsukade, Isamu
    Hayashi, Katsuhiro
    Hayashi, Takayuki
    Hayashida, Kiyoshi
    Hiraga, Junko S.
    Hornschemeier, Ann
    Hoshino, Akio
    Hughes, John P.
    Ichinohe, Yuto
    Iizuka, Ryo
    Inoue, Hajime
    Inoue, Yoshiyuki
    Ishida, Manabu
    Ishikawa, Kumi
    Ishisaki, Yoshitaka
    Iwai, Masachika
    Kaastra, Jelle
    Kallman, Tim
    Kamae, Tsuneyoshi
    Kataoka, Jun
    Katsuda, Satoru
    Kawai, Nobuyuki
    Kelley, Richard L.
    Kilbourne, Caroline A.
    Kitaguchi, Takao
    Kitamoto, Shunji
    Kitayama, Tetsu
    Kohmura, Takayoshi
    Kokubun, Motohide
    Koyama, Katsuji
    Koyama, Shu
    Kretschmar, Peter
    Krimm, Hans A.
    Kubota, Aya
    Kunieda, Hideyo
    Laurent, Philippe
    Lee, Shiu-Hang
    Leutenegger, Maurice A.
    Limousine, Olivier
    Loewenstein, Michael
    Long, Knox S.
    Lumb, David
    Madejski, Greg
    Maeda, Yoshitomo
    Maier, Daniel
    Makishima, Kazuo
    Markevitch, Maxim
    Matsumoto, Hironori
    Matsushita, Kyoko
    McCammon, Dan
    McNamara, Brian R.
    Mehdipour, Missagh
    Miller, Eric D.
    Miller, Jon M.
    Mineshige, Shin
    Mitsuda, Kazuhisa
    Mitsuishi, Ikuyuki
    Miyazawa, Takuya
    Mizuno, Tsunefumi
    Mori, Hideyuki
    Mori, Koji
    Mukai, Koji
    Murakami, Hiroshi
    Mushotzky, Richard F.
    Nakagawa, Takao
    Nakajima, Hiroshi
    Nakamori, Takeshi
    Nakashima, Shinya
    Nakazawa, Kazuhiro
    Nobukawa, Kumiko K.
    Nobukawa, Masayoshi
    Noda, Hirofumi
    Odaka, Hirokazu
    Ohashi, Takaya
    Ohno, Masanori
    Okajima, Takashi
    Ota, Naomi
    Ozaki, Masanobu
    Paerels, Frits
    Paltani, StPhane
    Petre, Robert
    Pinto, Ciro
    Porter, Frederick S.
    Pottschmidt, Katja
    Reynolds, Christopher S.
    Safi-Harb, Samar
    Saito, Shinya
    Sakai, Kazuhiro
    Sasaki, Toru
    Sato, Goro
    Sato, Kosuke
    Sato, Rie
    Sawada, Makoto
    Schartel, Norbert
    Serlemitsos, Peter J.
    Seta, Hiromi
    Shidatsu, Megumi
    Simionescu, Aurora
    Smith, Randall K.
    Soong, Yang
    Stawarz, Lukasz
    Sugawara, Yasuharu
    Sugita, Satoshi
    Szymkowiak, Andrew
    Tajima, Hiroyasu
    Takahashi, Hiromitsu
    Takahashi, Tadayuki
    Takeda, Shin'ichiro
    Takei, Yoh
    Tamagawa, Toru
    Tamura, Takayuki
    Tanaka, Takaaki
    Tanaka, Yasuo
    Tanaka, Yasuyuki T.
    Tashiro, Makoto S.
    Tawara, Yuzuru
    Terada, Yukikatsu
    Terashima, Yuichi
    Tombesi, Francesco
    Tomida, Hiroshi
    Tsuboi, Yohko
    Tsujimoto, Masahiro
    Tsunemi, Hiroshi
    Tsuru, Takeshi Go
    Uchida, Hiroyuki
    Uchiyama, Hideki
    Uchiyama, Yasunobu
    Ueda, Shutaro
    Ueda, Yoshihiro
    Uno, Shin'ichiro
    Urry, C. Megan
    Ursino, Eugenio
    de Vries, Cor P.
    Watanabe, Shin
    Werner, Norbert
    Wik, Daniel R.
    Wilkins, Dan R.
    Williams, Brian J.
    Yamada, Shinya
    Yamaguchi, Hiroya
    Yamaoka, Kazutaka
    Yamasaki, Noriko Y.
    Yamauchi, Makoto
    Yamauchi, Shigeo
    Yaqoob, Tahir
    Yatsu, Yoichi
    Yonetoku, Daisuke
    Zhuravleva, Irina
    Zoghbi, Abderahmen
    Solar abundance ratios of the iron-peak elements in the Perseus cluster2017In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 551, no 7681, p. 478-+Article in journal (Refereed)
    Abstract [en]

    The metal abundance of the hot plasma that permeates galaxy clusters represents the accumulation of heavy elements produced by billions of supernovae(1). Therefore, X-ray spectroscopy of the intracluster medium provides an opportunity to investigate the nature of supernova explosions integrated over cosmic time. In particular, the abundance of the iron-peak elements (chromium, manganese, iron and nickel) is key to understanding how the progenitors of typical type Ia supernovae evolve and explode(2-6). Recent X-ray studies of the intracluster medium found that the abundance ratios of these elements differ substantially from those seen in the Sun(7-11), suggesting differences between the nature of type Ia supernovae in the clusters and in the Milky Way. However, because the K-shell transition lines of chromium and manganese are weak and those of iron and nickel are very close in photon energy, highresolution spectroscopy is required for an accurate determination of the abundances of these elements. Here we report observations of the Perseus cluster, with statistically significant detections of the resonance emission from chromium, manganese and nickel. Our measurements, combined with the latest atomic models, reveal that these elements have near-solar abundance ratios with respect to iron, in contrast to previous claims. Comparison between our results and modern nucleosynthesis calculations(12-14) disfavours the hypothesis that type Ia supernova progenitors are exclusively white dwarfs with masses well below the Chandrasekhar limit (about 1.4 times the mass of the Sun). The observed abundance pattern of the iron-peak elements can be explained by taking into account a combination of near-and sub-Chandrasekhar-mass type Ia supernova systems, adding to the mounting evidence that both progenitor types make a substantial contribution to cosmic chemical enrichment(5,15,16).

  • 4. Ahmadi, M.
    et al.
    Alves, B. X. R.
    Baker, C. J. .
    Bertsche, W.
    Butler, E.
    Capra, A.
    Carruth, C.
    Cesar, C. L.
    Charlton, M.
    Cohen, S.
    Collister, R.
    Eriksson, S.
    Evans, A.
    Evetts, N.
    Fajans, J.
    Friesen, T.
    Fujiwara, M. C.
    Gill, D. R.
    Gutierrez, A.
    Hangst, J. S.
    Hardy, W. N.
    Hayden, M. E.
    Isaac, C. A.
    Ishida, A.
    Ohnson, M. A. J.
    Ones, S. A. J.
    Jonsell, Svante
    Stockholm University, Faculty of Science, Department of Physics.
    Kurchaninov, L.
    Madsen, N.
    Mathers, M.
    Maxwell, D.
    McKenna, J. T. K.
    Menary, S.
    Michan, J. M.
    Momose, T.
    Munich, J. J. .
    Nolan, P.
    Olchanski, K.
    Olin, A.
    Pusa, P.
    Rasmussen, C. O.
    Robicheaux, F.
    Sacramento, R. L.
    Sameed, M.
    Sarid, E.
    Silveira, D. M.
    Stracka, S.
    Stutter, G.
    So, C.
    Tharp, T. D.
    Thompson, J. E.
    Thompson, R. I.
    van der Werf, D. P.
    Wurtele, J. S.
    Observation of the 1S-2S transition in trapped antihydrogen2017In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 541, no 7638, p. 506-510Article in journal (Refereed)
    Abstract [en]

    The spectrum of the hydrogen atom has played a central part in fundamental physics over the past 200 years. Historical examples of its importance include the wavelength measurements of absorption lines in the solar spectrum by Fraunhofer, the identification of transition lines by Balmer, Lyman and others, the empirical description of allowed wavelengths by Rydberg, the quantum model of Bohr, the capability of quantum electrodynamics to precisely predict transition frequencies, and modern measurements of the 1S-2S transition by Hansch1 to a precision of a few parts in 10(15). Recent technological advances have allowed us to focus on antihydrogen-the antimatter equivalent of hydrogen(2-4). The Standard Model predicts that there should have been equal amounts of matter and antimatter in the primordial Universe after the Big Bang, but today's Universe is observed to consist almost entirely of ordinary matter. This motivates the study of antimatter, to see if there is a small asymmetry in the laws of physics that govern the two types of matter. In particular, the CPT (charge conjugation, parity reversal and time reversal) theorem, a cornerstone of the Standard Model, requires that hydrogen and antihydrogen have the same spectrum. Here we report the observation of the 1S-2S transition in magnetically trapped atoms of antihydrogen. We determine that the frequency of the transition, which is driven by two photons from a laser at 243 nanometres, is consistent with that expected for hydrogen in the same environment. This laser excitation of a quantum state of an atom of antimatter represents the most precise measurement performed on an anti-atom. Our result is consistent with CPT invariance at a relative precision of about 2 x 10(-10).

  • 5. Ahmadi, M.
    et al.
    Alves, B. X. R.
    Baker, C. J.
    Bertsche, W.
    Butler, E.
    Capra, A.
    Carruth, C.
    Cesar, C. L.
    Charlton, M.
    Cohen, S.
    Collister, R.
    Eriksson, S.
    Evans, A.
    Evetts, N.
    Fajans, J.
    Friesen, T.
    Fujiwara, M. C.
    Gill, D. R.
    Gutierrez, A.
    Hangst, J. S.
    Hardy, W. N.
    Hayden, M. E.
    Isaac, C. A.
    Ishida, A.
    Johnson, M. A.
    Jones, S. A.
    Jonsell, Svante
    Stockholm University, Faculty of Science, Department of Physics.
    Kurchaninov, L.
    Madsen, N.
    Mathers, M.
    Maxwell, D.
    McKenna, J. T. K.
    Menary, S.
    Michan, J. M.
    Momose, T.
    Munich, J. J.
    Nolan, P.
    Olchanski, K.
    Olin, A.
    Pusa, P.
    Rasmussen, C. O.
    Robicheaux, F.
    Sacramento, R. L.
    Sameed, M.
    Sarid, E.
    Silveira, D. M.
    Stracka, S.
    Stutter, G.
    So, C.
    Tharp, T. D.
    Thompson, J. E.
    Thompson, R. I.
    Van der Werf, D. P.
    Wurtele, J. S.
    Observation of the hyperfine spectrum of antihydrogen2017In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 548, no 7665, p. 66-+Article in journal (Refereed)
    Abstract [en]

    The observation of hyperfine structure in atomic hydrogen by Rabi and co-workers(1-3) and the measurement(4) of the zero-field ground-state splitting at the level of seven parts in 10(13) are important achievements of mid-twentieth-century physics. The work that led to these achievements also provided the first evidence for the anomalous magnetic moment of the electron(5-8), inspired Schwinger's relativistic theory of quantum electrodynamics(9,10) and gave rise to the hydrogen maser(11), which is a critical component of modern navigation, geo-positioning and very-long-baseline interferometry systems. Research at the Antiproton Decelerator at CERN by the ALPHA collaboration extends these enquiries into the antimatter sector. Recently, tools have been developed that enable studies of the hyperfine structure of antihydrogen(12)-the antimatter counterpart of hydrogen. The goal of such studies is to search for any differences that might exist between this archetypal pair of atoms, and thereby to test the fundamental principles on which quantum field theory is constructed. Magnetic trapping of antihydrogen atoms(13,14) provides a means of studying them by combining electromagnetic interaction with detection techniques that are unique to antimatter(12,15). Here we report the results of a microwave spectroscopy experiment in which we probe the response of antihydrogen over a controlled range of frequencies. The data reveal clear and distinct signatures of two allowed transitions, from which we obtain a direct, magnetic-field-independent measurement of the hyperfine splitting. From a set of trials involving 194 detected atoms, we determine a splitting of 1,420.4 +/- 0.5 megahertz, consistent with expectations for atomic hydrogen at the level of four parts in 10(4). This observation of the detailed behaviour of a quantum transition in an atom of antihydrogen exemplifies tests of fundamental symmetries such as charge-parity-time in antimatter, and the techniques developed here will enable more-precise such tests.

  • 6. Ahmadi, M.
    et al.
    Alves, B. X. R.
    Baker, C. J.
    Bertsche, W.
    Capra, A.
    Carruth, C.
    Cesar, C. L.
    Charlton, M.
    Cohen, S.
    Collister, R.
    Eriksson, S.
    Evans, A.
    Evetts, N.
    Fajans, J.
    Friesen, T.
    Fujiwara, M. C.
    Gill, D. R.
    Granum, P.
    Hangst, J. S.
    Hardy, W. N.
    Hayden, M. E.
    Hunter, E. D.
    Isaac, C. A.
    Johnson, M. A.
    Jones, J. M.
    Jones, S. A.
    Jonsell, Svante
    Stockholm University, Faculty of Science, Department of Physics.
    Khramov, A.
    Knapp, P.
    Kurchaninov, L.
    Madsen, N.
    Maxwell, D.
    McKenna, J. T. K.
    Menary, S.
    Michan, J. M.
    Momose, T.
    Munich, J. J.
    Olchanski, K.
    Olin, A.
    Pusa, P.
    Rasmussen, C. Ø.
    Robicheaux, F.
    Sacramento, R. L.
    Sameed, M.
    Sarid, E.
    Silveira, D. M.
    So, C.
    Starko, D. M.
    Stutter, G.
    Tharp, T. D.
    Thompson, R. I.
    van der Werf, D. P.
    Wurtele, J. S.
    Investigation of the fine structure of antihydrogen2020In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 578, no 7795, p. 375-380Article in journal (Refereed)
    Abstract [en]

    At the historic Shelter Island Conference on the Foundations of Quantum Mechanics in 1947, Willis Lamb reported an unexpected feature in the fine structure of atomic hydrogen: a separation of the 2S(1/2) and 2P(1/2) states(1). The observation of this separation, now known as the Lamb shift, marked an important event in the evolution of modern physics, inspiring others to develop the theory of quantum electrodynamics(2-5). Quantum electrodynamics also describes antimatter, but it has only recently become possible to synthesize and trap atomic antimatter to probe its structure. Mirroring the historical development of quantum atomic physics in the twentieth century, modern measurements on anti-atoms represent a unique approach for testing quantum electrodynamics and the foundational symmetries of the standard model. Here we report measurements of the fine structure in the n = 2 states of antihydrogen, the antimatter counterpart of the hydrogen atom. Using optical excitation of the 1S-2P Lyman-alpha transitions in antihydrogen(6), we determine their frequencies in a magnetic field of 1 tesla to a precision of 16 parts per billion. Assuming the standard Zeeman and hyperfine interactions, we infer the zero-field fine-structure splitting (2P(1/2)-2P(3/2)) in antihydrogen. The resulting value is consistent with the predictions of quantum electrodynamics to a precision of 2 per cent. Using our previously measured value of the 1S-2S transition frequency(6,7), we find that the classic Lamb shift in antihydrogen (2S(1/2)-2P(1/2) splitting at zero field) is consistent with theory at a level of 11 per cent. Our observations represent an important step towards precision measurements of the fine structure and the Lamb shift in the antihydrogen spectrum as tests of the charge-parity-time symmetry(8) and towards the determination of other fundamental quantities, such as the antiproton charge radius(9,10), in this antimatter system. Precision measurements of the 1S-2P transition in antihydrogen that take into account the standard Zeeman and hyperfine effects confirm the predictions of quantum electrodynamics.

  • 7. Ahmadi, M.
    et al.
    Alves, B. X. R.
    Baker, C. J.
    Bertsche, W.
    Capra, A.
    Carruth, C.
    Cesar, C. L.
    Charlton, M.
    Cohen, S.
    Collister, R.
    Eriksson, S.
    Evans, A.
    Evetts, N.
    Fajans, J.
    Friesen, T.
    Fujiwara, M. C.
    Gill, D. R.
    Hangst, J. S.
    Hardy, W. N.
    Hayden, M. E.
    Hunter, E. D.
    Isaac, C. A.
    Johnson, M. A.
    Jones, J. M.
    Jones, S. A.
    Jonsell, Svante
    Stockholm University, Faculty of Science, Department of Physics.
    Khramov, A.
    Knapp, P.
    Kurchaninov, L.
    Madsen, N.
    Maxwell, D.
    McKenna, J. T. K.
    Menary, S.
    Michan, J. M.
    Momose, T.
    Munich, J. J.
    Olchanski, K.
    Olin, A.
    Pusa, P.
    Rasmussen, C. O.
    Robicheaux, F.
    Sacramento, R. L.
    Sameed, M.
    Sarid, E.
    Silveira, D. M.
    Starko, D. M.
    Stutter, G.
    So, C.
    Tharp, T. D.
    Thompson, R. I.
    van der Werf, D. P.
    Wurtele, J. S.
    Observation of the 1S-2P Lyman-alpha transition in antihydrogen2018In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 561, no 7722, p. 211-217Article in journal (Refereed)
    Abstract [en]

    In 1906, Theodore Lyman discovered his eponymous series of transitions in the extreme-ultraviolet region of the atomic hydrogen spectrum(1,2). The patterns in the hydrogen spectrum helped to establish the emerging theory of quantum mechanics, which we now know governs the world at the atomic scale. Since then, studies involving the Lyman-alpha line-the 1S-2P transition at a wavelength of 121.6 nanometres-have played an important part in physics and astronomy, as one of the most fundamental atomic transitions in the Universe. For example, this transition has long been used by astronomers studying the intergalactic medium and testing cosmological models via the so-called 'Lyman-alpha forest('3) of absorption lines at different redshifts. Here we report the observation of the Lyman-alpha transition in the antihydrogen atom, the antimatter counterpart of hydrogen. Using narrow-line-width, nanosecond-pulsed laser radiation, the 1S-2P transition was excited in magnetically trapped antihydrogen. The transition frequency at a field of 1.033 tesla was determined to be 2,466,051.7 +/- 0.12 gigahertz (1 sigma uncertainty) and agrees with the prediction for hydrogen to a precision of 5 x 10(-8). Comparisons of the properties of antihydrogen with those of its well-studied matter equivalent allow precision tests of fundamental symmetries between matter ;and antimatter. Alongside the ground-state hyperfine(4,5) and 1S-2S transitions(6,7) recently observed in antihydrogen, the Lyman-alpha transition will permit laser cooling of antihydrogen(8,9), thus providing a cold and dense sample of anti-atoms for precision spectroscopy and gravity measurements(10). In addition to the observation of this fundamental transition, this work represents both a decisive technological step towards laser cooling of antihydrogen, and the extension of antimatter spectroscopy to quantum states possessing orbital angular momentum.

  • 8. Ahmadi, M.
    et al.
    Alves, B. X. R.
    Baker, C. J.
    Bertsche, W.
    Capra, A.
    Carruth, C.
    Cesar, C. L.
    Charlton, M.
    Cohen, S.
    Collister, R.
    Eriksson, S.
    Evans, A.
    Evetts, N.
    Fajans, J.
    Friesen, T.
    Fujiwara, M. C.
    Gill, D. R.
    Hangst, J. S.
    Hardy, W. N.
    Hayden, M. E.
    Isaac, C. A.
    Johnson, M. A.
    Jones, J. M.
    Jones, S. A.
    Jonsell, Svante
    Stockholm University, Faculty of Science, Department of Physics.
    Khramov, A.
    Knapp, P.
    Kurchaninov, L.
    Madsen, N.
    Maxwell, D.
    McKenna, J. T. K.
    Menary, S.
    Momose, T.
    Munich, J. J.
    Olchanski, K.
    Olin, A.
    Pusa, P.
    Rasmussen, C. O.
    Robicheaux, F.
    Sacramento, R. L.
    Sameed, M.
    Sarid, E.
    Silveira, D. M.
    Stutter, G.
    So, C.
    Tharp, T. D.
    Thompson, R. I.
    van der Werf, D. P.
    Wurtele, J. S.
    Characterization of the 1S-2S transition in antihydrogen2018In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 557, no 7703, p. 71-+Article in journal (Refereed)
    Abstract [en]

    In 1928, Dirac published an equation(1) that combined quantum mechanics and special relativity. Negative-energy solutions to this equation, rather than being unphysical as initially thought, represented a class of hitherto unobserved and unimagined particles-antimatter. The existence of particles of antimatter was confirmed with the discovery of the positron(2) (or anti-electron) by Anderson in 1932, but it is still unknown why matter, rather than antimatter, survived after the Big Bang. As a result, experimental studies of antimatter(3-7), including tests of fundamental symmetries such as charge-parity and charge-parity-time, and searches for evidence of primordial antimatter, such as antihelium nuclei, have high priority in contemporary physics research. The fundamental role of the hydrogen atom in the evolution of the Universe and in the historical development of our understanding of quantum physics makes its antimatter counterpart-the antihydrogen atom-of particular interest. Current standard-model physics requires that hydrogen and antihydrogen have the same energy levels and spectral lines. The laser-driven 1S-2S transition was recently observed(8) in antihydrogen. Here we characterize one of the hyperfine components of this transition using magnetically trapped atoms of antihydrogen and compare it to model calculations for hydrogen in our apparatus. We find that the shape of the spectral line agrees very well with that expected for hydrogen and that the resonance frequency agrees with that in hydrogen to about 5 kilohertz out of 2.5 x 10(15) hertz. This is consistent with charge-parity-time invariance at a relative precision of 2 x 10(-12)-two orders of magnitude more precise than the previous determination(8)-corresponding to an absolute energy sensitivity of 2 x 10(-20) GeV.

  • 9. Ahmadi, M.
    et al.
    Baquero-Ruiz, M.
    Bertsche, W.
    Butler, E.
    Capra, A.
    Carruth, C.
    Cesar, C. L.
    Charlton, M.
    Charman, A. E.
    Eriksson, S.
    Evans, L. T.
    Evetts, N.
    Fajans, J.
    Friesen, T.
    Fujiwara, M. C.
    Gill, D. R.
    Gutierrez, A.
    Hangst, J. S.
    Hardy, W. N.
    Hayden, M. E.
    Isaac, C. A.
    Ishida, A.
    Jones, S. A.
    Jonsell, Svante
    Stockholm University, Faculty of Science, Department of Physics.
    Kurchaninov, L.
    Madsen, N.
    Maxwell, D.
    McKenna, J. T. K.
    Menary, S.
    Michan, J. M.
    Momose, T.
    Munich, J. J.
    Nolan, P.
    Olchanski, K.
    Olin, A.
    Povilus, A.
    Pusa, P.
    Rasmussen, C. O.
    Robicheaux, F.
    Sacramento, R. L.
    Sameed, M.
    Sarid, E.
    Silveira, D. M.
    So, C.
    Tharp, T. D.
    Thompson, R. I.
    van der Werf, D. P.
    Wurtele, J. S.
    Zhmoginov, A. I.
    An improved limit on the charge of antihydrogen from stochastic acceleration2016In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 529, no 7586, p. 373-+Article in journal (Refereed)
    Abstract [en]

    Antimatter continues to intrigue physicists because of its apparent absence in the observable Universe. Current theory requires that matter and antimatter appeared in equal quantities after the Big Bang, but the Standard Model of particle physics offers no quantitative explanation for the apparent disappearance of half the Universe. It has recently become possible to study trapped atoms(1-4) of antihydrogen to search for possible, as yet unobserved, differences in the physical behaviour of matter and antimatter. Here we consider the charge neutrality of the antihydrogen atom. By applying stochastic acceleration to trapped antihydrogen atoms, we determine an experimental bound on the antihydrogen charge, Qe, of vertical bar Q vertical bar < 0.71 parts per billion (one standard deviation), in which e is the elementary charge. This bound is a factor of 20 less than that determined from the best previous measurement(5) of the antihydrogen charge. The electrical charge of atoms and molecules of normal matter is known(6) to be no greater than about 10(-21)e for a diverse range of species including H-2, He and SF6. Charge-parity-time symmetry and quantum anomaly cancellation(7) demand that the charge of antihydrogen be similarly small. Thus, our measurement constitutes an improved limit and a test of fundamental aspects of the Standard Model. If we assume charge superposition and use the best measured value of the antiproton charge(8), then we can place a new limit on the positron charge anomaly (the relative difference between the positron and elementary charge) of about one part per billion (one standard deviation), a 25-fold reduction compared to the current best measurement(8),(9).

  • 10.
    Ahrens, Maryon
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Bohm, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Deoskar, Kunal
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Finley, Chad
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hultqvist, Klas
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Jansson, Matti
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Walck, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Detection of a particle shower at the Glashow resonance with IceCube2021In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 591, no 7849, p. 220-224Article in journal (Refereed)
    Abstract [en]

    The Glashow resonance describes the resonant formation of a W- boson during the interaction of a high-energy electron antineutrino with an electron(1), peaking at an antineutrino energy of 6.3 petaelectronvolts (PeV) in the rest frame of the electron. Whereas this energy scale is out of reach for currently operating and future planned particle accelerators, natural astrophysical phenomena are expected to produce antineutrinos with energies beyond the PeV scale. Here we report the detection by the IceCube neutrino observatory of a cascade of high-energy particles (a particle shower) consistent with being created at the Glashow resonance. A shower with an energy of 6.05 +/- 0.72 PeV (determined from Cherenkov radiation in the Antarctic Ice Sheet) was measured. Features consistent with the production of secondary muons in the particle shower indicate the hadronic decay of a resonant W- boson, confirm that the source is astrophysical and provide improved directional localization. The evidence of the Glashow resonance suggests the presence of electron antineutrinos in the astrophysical flux, while also providing further validation of the standard model of particle physics. Its unique signature indicates a method of distinguishing neutrinos from antineutrinos, thus providing a way to identify astronomical accelerators that produce neutrinos via hadronuclear or photohadronic interactions, with or without strong magnetic fields. As such, knowledge of both the flavour (that is, electron, muon or tau neutrinos) and charge (neutrino or antineutrino) will facilitate the advancement of neutrino astronomy.

  • 11.
    Ahrens, Maryon
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Bohm, Christian
    Stockholm University, Faculty of Science, Department of Physics.
    Dumm, Jonathan P.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Finley, Chad
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Flis, Samuel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hultqvist, Klas
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Walck, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Zoll, Marcel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Measurement of the multi-TeV neutrino interaction cross-section with IceCube using Earth absorption2017In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 551, no 7682, p. 596-+Article in journal (Refereed)
    Abstract [en]

    Neutrinos interact only very weakly, so they are extremely penetrating. The theoretical neutrino-nucleon interaction cross-section, however, increases with increasing neutrino energy, and neutrinos with energies above 40 teraelectronvolts (TeV) are expected to be absorbed as they pass through the Earth. Experimentally, the cross-section has been determined only at the relatively low energies (below 0.4 TeV) that are available at neutrino beams fromaccelerators(1,2). Here we report a measurement of neutrino absorption by the Earth using a sample of 10,784 energetic upward-going neutrino-induced muons. The flux of high-energy neutrinos transiting long paths through the Earth is attenuated compared to a reference sample that follows shorter trajectories. Using a fit to the two-dimensional distribution of muon energy and zenith angle, we determine the neutrino-nucleon interaction cross-section for neutrino energies 6.3-980 TeV, more than an order of magnitude higher than previous measurements. The measured cross-section is about 1.3 times the prediction of the standard model(3), consistent with the expectations for charged-and neutral-current interactions. We do not observe a large increase in the crosssection with neutrino energy, in contrast with the predictions of some theoretical models, including those invoking more compact spatial dimensions(4) or the production of leptoquarks(5). This cross-section measurement can be used to set limits on the existence of some hypothesized beyond-standard-model particles, including leptoquarks.

  • 12. Almeida, Joao
    et al.
    Schobesberger, Siegfried
    Kuerten, Andreas
    Ortega, Ismael K.
    Kupiainen-Maatta, Oona
    Praplan, Arnaud P.
    Adamov, Alexey
    Amorim, Antonio
    Bianchi, Federico
    Breitenlechner, Martin
    David, Andre
    Dommen, Josef
    Donahue, Neil M.
    Downard, Andrew
    Dunne, Eimear
    Duplissy, Jonathan
    Ehrhart, Sebastian
    Flagan, Richard C.
    Franchin, Alessandro
    Guida, Roberto
    Hakala, Jani
    Hansel, Armin
    Heinritzi, Martin
    Henschel, Henning
    Jokinen, Tuija
    Junninen, Heikki
    Kajos, Maija
    Kangasluoma, Juha
    Keskinen, Helmi
    Kupc, Agnieszka
    Kurten, Theo
    Kvashin, Alexander N.
    Laaksonen, Ari
    Lehtipalo, Katrianne
    Leiminger, Markus
    Leppa, Johannes
    Loukonen, Ville
    Makhmutov, Vladimir
    Mathot, Serge
    McGrath, Matthew J.
    Nieminen, Tuomo
    Olenius, Tinja
    Onnela, Antti
    Petaja, Tuukka
    Riccobono, Francesco
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Rissanen, Matti
    Rondo, Linda
    Ruuskanen, Taina
    Santos, Filipe D.
    Sarnela, Nina
    Schallhart, Simon
    Schnitzhofer, Ralf
    Seinfeld, John H.
    Simon, Mario
    Sipila, Mikko
    Stozhkov, Yuri
    Stratmann, Frank
    Tome, Antonio
    Troestl, Jasmin
    Tsagkogeorgas, Georgios
    Vaattovaara, Petri
    Viisanen, Yrjo
    Virtanen, Annele
    Vrtala, Aron
    Wagner, Paul E.
    Weingartner, Ernest
    Wex, Heike
    Williamson, Christina
    Wimmer, Daniela
    Ye, Penglin
    Yli-Juuti, Taina
    Carslaw, Kenneth S.
    Kulmala, Markku
    Curtius, Joachim
    Baltensperger, Urs
    Worsnop, Douglas R.
    Vehkamaki, Hanna
    Kirkby, Jasper
    Molecular understanding of sulphuric acid-amine particle nucleation in the atmosphere2013In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 502, no 7471, p. 359-+Article in journal (Refereed)
    Abstract [en]

    Nucleation of aerosol particles from trace atmospheric vapours is thought to provide up to half of global cloud condensation nuclei(1). Aerosols can cause a net cooling of climate by scattering sunlight and by leading to smaller but more numerous cloud droplets, which makes clouds brighter and extends their lifetimes(2). Atmospheric aerosols derived from human activities are thought to have compensated for a large fraction of the warming caused by greenhouse gases(2). However, despite its importance for climate, atmospheric nucleation is poorly understood. Recently, it has been shown that sulphuric acid and ammonia cannot explain particle formation rates observed in the lower atmosphere(3). It is thought that amines may enhance nucleation(4-16), but until now there has been no direct evidence for amine ternary nucleation under atmospheric conditions. Here we use the CLOUD (Cosmics Leaving OUtdoor Droplets) chamber at CERN and find that dimethylamine above three parts per trillion by volume can enhance particle formation rates more than 1,000-fold compared with ammonia, sufficient to account for the particle formation rates observed in the atmosphere. Molecular analysis of the clusters reveals that the faster nucleation is explained by a base-stabilization mechanism involving acid-amine pairs, which strongly decrease evaporation. The ion-induced contribution is generally small, reflecting the high stability of sulphuric acid-dimethylamine clusters and indicating that galactic cosmic rays exert only a small influence on their formation, except at low overall formation rates. Our experimental measurements are well reproduced by a dynamical model based on quantum chemical calculations of binding energies of molecular clusters, without any fitted parameters. These results show that, in regions of the atmosphere near amine sources, both amines and sulphur dioxide should be considered when assessing the impact of anthropogenic activities on particle formation.

  • 13. Amole, C.
    et al.
    Ashkezari, M. D.
    Baquero-Ruiz, M.
    Bertsche, W.
    Bowe, P. D.
    Butler, E.
    Capra, A.
    Cesar, C. L.
    Charlton, M.
    Deller, A.
    Donnan, P. H.
    Eriksson, S.
    Fajans, J.
    Friesen, T.
    Fujiwara, M. C.
    Gill, D. R.
    Gutierrez, A.
    Hangst, J. S.
    Hardy, W. N.
    Hayden, M. E.
    Humphries, A. J.
    Isaac, C. A.
    Jonsell, Svante
    Stockholm University, Faculty of Science, Department of Physics.
    Kurchaninov, L.
    Little, A.
    Madsen, N.
    McKenna, J. T. K.
    Menary, S.
    Napoli, S. C.
    Nolan, P.
    Olchanski, K.
    Olin, A.
    Pusa, P.
    Rasmussen, C. O.
    Robicheaux, F.
    Sarid, E.
    Shields, C. R.
    Silveira, D. M.
    Stracka, S.
    So, C.
    Thompson, R. I.
    van der Werf, D. P.
    Wurtele, J. S.
    Resonant quantum transitions in trapped antihydrogen atoms2012In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 483, no 7390, p. 439-U86Article in journal (Refereed)
    Abstract [en]

    The hydrogen atom is one of the most important and influential model systems in modern physics. Attempts to understand its spectrum are inextricably linked to the early history and development of quantum mechanics. The hydrogen atom's stature lies in its simplicity and in the accuracy with which its spectrum can be measured(1) and compared to theory. Today its spectrum remains a valuable tool for determining the values of fundamental constants and for challenging the limits of modern physics, including the validity of quantum electrodynamics and-by comparison with measurements on its antimatter counterpart, antihydrogen-the validity of CPT (charge conjugation, parity and time reversal) symmetry. Here we report spectroscopy of a pure antimatter atom, demonstrating resonant quantum transitions in antihydrogen. We have manipulated the internal spin state(2,3) of antihydrogen atoms so as to induce magnetic resonance transitions between hyperfine levels of the positronic ground state. We used resonant microwave radiation to flip the spin of the positron in antihydrogen atoms that were magnetically trapped(4-6) in the ALPHA apparatus. The spin flip causes trapped anti-atoms to be ejected from the trap. We look for evidence of resonant interaction by comparing the survival rate of trapped atoms irradiated with microwaves on-resonance to that of atoms subjected to microwaves that are off-resonance. In one variant of the experiment, we detect 23 atoms that survive in 110 trapping attempts with microwaves off-resonance (0.21 per attempt), and only two atoms that survive in 103 attempts with microwaves on-resonance (0.02 per attempt). We also describe the direct detection of the annihilation of antihydrogen atoms ejected by the microwaves.

  • 14. Anderson, E. K.
    et al.
    Bertsche, W.
    Fajans, J.
    Hangst, J. S.
    Jonsell, Svante
    Stockholm University, Faculty of Science, Department of Physics.
    Wurtele, J. S.
    Observation of the effect of gravity on the motion of antimatter2023In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 621, no 7980, p. 716-722Article in journal (Refereed)
    Abstract [en]

    Einstein’s general theory of relativity from 1915 remains the most successful description of gravitation. From the 1919 solar eclipse to the observation of gravitational waves, the theory has passed many crucial experimental tests. However, the evolving concepts of dark matter and dark energy illustrate that there is much to be learned about the gravitating content of the universe. Singularities in the general theory of relativity and the lack of a quantum theory of gravity suggest that our picture is incomplete. It is thus prudent to explore gravity in exotic physical systems. Antimatter was unknown to Einstein in 1915. Dirac’s theory appeared in 1928; the positron was observed in 1932. There has since been much speculation about gravity and antimatter. The theoretical consensus is that any laboratory mass must be attracted by the Earth, although some authors have considered the cosmological consequences if antimatter should be repelled by matter. In the general theory of relativity, the weak equivalence principle (WEP) requires that all masses react identically to gravity, independent of their internal structure. Here we show that antihydrogen atoms, released from magnetic confinement in the ALPHA-g apparatus, behave in a way consistent with gravitational attraction to the Earth. Repulsive ‘antigravity’ is ruled out in this case. This experiment paves the way for precision studies of the magnitude of the gravitational acceleration between anti-atoms and the Earth to test the WEP.

  • 15. Andresen, G. B.
    et al.
    Ashkezari, M. D.
    Baquero-Ruiz, M.
    Bertsche, W.
    Bowe, P. D.
    Butler, E.
    Cesar, C. L.
    Chapman, S.
    Charlton, M.
    Deller, A.
    Eriksson, S.
    Fajans, J.
    Friesen, T.
    Fujiwara, M. C.
    Gill, D. R.
    Gutierrez, A.
    Hangst, J. S.
    Hardy, W. N.
    Hayden, M. E.
    Humphries, A. J.
    Hydomako, R.
    Jenkins, M. J.
    Jonsell, Svante
    Stockholm University, Faculty of Science, Department of Physics.
    Jorgensen, L. V.
    Kurchaninov, L.
    Madsen, N.
    Menary, S.
    Nolan, P.
    Olchanski, K.
    Olin, A.
    Povilus, A.
    Pusa, P.
    Robicheaux, F.
    Sarid, E.
    Nasr, S. Seif el
    Silveira, D. M.
    So, C.
    Storey, J. W.
    Thompson, R. I.
    van der Werf, D. P.
    Wurtele, J. S.
    Yamazaki, Y.
    Trapped antihydrogen2010In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 468, no 7324, p. 673-676Article in journal (Refereed)
    Abstract [en]

    Antimatter was first predicted1 in 1931, by Dirac. Work with high-energy antiparticles is now commonplace, and anti-electrons are used regularly in the medical technique of positron emission tomography scanning. Antihydrogen, the bound state of an antiproton and a positron, has been produced2, 3 at low energies at CERN (the European Organization for Nuclear Research) since 2002. Antihydrogen is of interest for use in a precision test of nature’s fundamental symmetries. The charge conjugation/parity/time reversal (CPT) theorem, a crucial part of the foundation of the standard model of elementary particles and interactions, demands that hydrogen and antihydrogen have the same spectrum. Given the current experimental precision of measurements on the hydrogen atom (about two parts in 1014 for the frequency of the 1s-to-2s transition4), subjecting antihydrogen to rigorous spectroscopic examination would constitute a compelling, model-independent test of CPT. Antihydrogen could also be used to study the gravitational behaviour of antimatter5. However, so far experiments have produced antihydrogen that is not confined, precluding detailed study of its structure. Here we demonstrate trapping of antihydrogen atoms. From the interaction of about 107 antiprotons and 7 × 108 positrons, we observed 38 annihilation events consistent with the controlled release of trapped antihydrogen from our magnetic trap; the measured background is 1.4 ± 1.4 events. This result opens the door to precision measurements on anti-atoms, which can soon be subjected to the same techniques as developed for hydrogen.

  • 16. Aprile, E.
    et al.
    Aalbers, Jelle
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Nikhef and the University of Amsterdam, The Netherlands.
    Agostini, F.
    Alfonsi, M.
    Althueser, L.
    Amaro, F. D.
    Anthony, M.
    Antochi, Vasile Cristian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Arneodo, F.
    Baudis, L.
    Bauermeister, Boris
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Benabderrahmane, L.
    Berger, T.
    Breur, P. A.
    Brown, A.
    Brown, A.
    Brown, E.
    Bruenner, S.
    Bruno, G.
    Budnik, R.
    Capelli, C.
    Cardoso, J. M. R.
    Cichon, D.
    Coderre, D.
    Colijn, A. P.
    Conrad, Jan
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Cussonneau, J. P.
    Decowski, M. P.
    de Perio, P.
    Di Gangi, P.
    Di Giovanni, A.
    Diglio, S.
    Elykov, A.
    Eurin, G.
    Fei, J.
    Ferella, Alfredo D.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Fieguth, A.
    Fulgione, W.
    Rosso, A. Gallo
    Galloway, M.
    Gao, F.
    Garbini, M.
    Grandi, L.
    Greene, Z.
    Hasterok, C.
    Hogenbirk, E.
    Howlett, J.
    Iacovacci, M.
    Itay, R.
    Joerg, F.
    Kaminsky, B.
    Kazama, S.
    Kish, A.
    Koltman, G.
    Kopec, A.
    Landsman, H.
    Lang, R. F.
    Levinson, L.
    Lin, Q.
    Lindemann, S.
    Lindner, M.
    Lombardi, F.
    Lopes, J. A. M.
    Fune, E. Lopez
    Macolino, C.
    Mahlstedt, Jörn
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Manfredini, A.
    Marignetti, F.
    Undagoitia, T. Marrodan
    Masbou, J.
    Masson, D.
    Mastroianni, S.
    Messina, M.
    Micheneau, K.
    Miller, K.
    Molinario, A.
    Morå, Knut
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Murra, M.
    Naganoma, J.
    Ni, K.
    Oberlack, U.
    Odgers, K.
    Pelssers, Bart
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Peres, R.
    Piastra, F.
    Pienaar, J.
    Pizzella, V.
    Plante, G.
    Podviianiuk, R.
    Priel, N.
    Qiu, H.
    Garcia, D. Ramirez
    Reichard, S.
    Riedel, B.
    Rizzo, A.
    Rocchetti, A.
    Rupp, N.
    dos Santos, J. M. F.
    Sartorelli, G.
    Sarcevic, N.
    Scheibelhut, M.
    Schindler, S.
    Schreiner, J.
    Schulte, D.
    Schumann, M.
    Lavina, L. Scotto
    Selvi, M.
    Shagin, P.
    Shockley, E.
    Silva, M.
    Simgen, H.
    Therreau, C.
    Thers, D.
    Toschi, F.
    Trinchero, G.
    Tunnell, C.
    Upole, N.
    Vargas, M.
    Wack, O.
    Wang, H.
    Wang, Z.
    Wei, Y.
    Weinheimer, C.
    Wenz, D.
    Wittweg, C.
    Wulf, J.
    Ye, J.
    Zhang, Y.
    Zhu, T.
    Zopounidis, J. P.
    Observation of two-neutrino double electron capture in 124Xe with XENON1T2019In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 568, no 7753, p. 532-535Article in journal (Refereed)
    Abstract [en]

    Two-neutrino double electron capture (2νECEC) is a second-order weak-interaction process with a predicted half-life that surpasses the age of the Universe by many orders of magnitude. Until now, indications of 2νECEC decays have only been seen for two isotopes, 78Kr and 130Ba, and instruments with very low background levels are needed to detect them directly with high statistical significance. The 2νECEC half-life is an important observable for nuclear structure models and its measurement represents a meaningful step in the search for neutrinoless double electron capture—the detection of which would establish the Majorana nature of the neutrino and would give access to the absolute neutrino mass. Here we report the direct observation of 2νECEC in 124Xe with the XENON1T dark-matter detector. The significance of the signal is 4.4 standard deviations and the corresponding half-life of 1.8 × 1022 years (statistical uncertainty, 0.5 × 1022 years; systematic uncertainty, 0.1 × 1022 years) is the longest measured directly so far. This study demonstrates that the low background and large target mass of xenon-based dark-matter detectors make them well suited for measuring rare processes and highlights the broad physics reach of larger next-generation experiments. 

  • 17. Arcavi, Iair
    et al.
    Howell, D. Andrew
    Kasen, Daniel
    Bildsten, Lars
    Hosseinzadeh, Griffin
    McCully, Curtis
    Wong, Zheng Chuen
    Katz, Sarah Rebekah
    Gal-Yam, Avishay
    Sollerman, Jesper
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Taddia, Francesco
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Leloudas, Giorgos
    Fremling, Christoffer
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Nugent, Peter E.
    Horesh, Assaf
    Mooley, Kunal
    Rumsey, Clare
    Cenko, S. B. Radley
    Graham, Melissa L.
    Perley, Daniel A.
    Nakar, Ehud
    Shaviv, Nir J.
    Bromberg, Omer
    Shen, Ken J.
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Ofek, Eran O.
    Cao, Yi
    Wang, Xiaofeng
    Huang, Fang
    Rui, Liming
    Zhang, Tianmeng
    Li, Wenxiong
    Li, Zhitong
    Zhang, Jujia
    Valenti, Stefano
    Guevel, David
    Shappee, Benjamin
    Kochanek, Christopher S.
    Holoien, Thomas W. -S.
    Filippenko, Alexei V.
    Fender, Rob
    Nyholm, Anders
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Yaron, Ofer
    Kasliwal, Mansi M. .
    Sullivan, Mark
    Lagorodnova, Nadja B.
    Walters, Richard S.
    Lunnan, Ragnhild
    Khazov, Danny
    Andreoni, Igor
    Laher, Russ R.
    Konidaris, Nick
    Wozniak, Przemek
    Bue, Brian
    Energetic eruptions leading to a peculiar hydrogen-rich explosion of a massive star2017In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 551, no 7679, p. 210-213Article in journal (Refereed)
    Abstract [en]

    Every supernova so far observed has been considered to be the terminal explosion of a star. Moreover, all supernovae with absorption lines in their spectra show those lines decreasing in velocity over time, as the ejecta expand and thin, revealing slower-moving material that was previously hidden. In addition, every supernova that exhibits the absorption lines of hydrogen has one main light-curve peak, or a plateau in luminosity, lasting approximately 100 days before declining(1). Here we report observations of iPTF14hls, an event that has spectra identical to a hydrogen-rich core-collapse supernova, but characteristics that differ extensively from those of known supernovae. The light curve has at least five peaks and remains bright for more than 600 days; the absorption lines show little to no decrease in velocity; and the radius of the line-forming region is more than an order of magnitude bigger than the radius of the photosphere derived from the continuum emission. These characteristics are consistent with a shell of several tens of solar masses ejected by the progenitor star at supernova-level energies a few hundred days before a terminal explosion. Another possible eruption was recorded at the same position in 1954. Multiple energetic pre-supernova eruptions are expected to occur in stars of 95 to 130 solar masses, which experience the pulsational pair instability(2-5). That model, however, does not account for the continued presence of hydrogen, or the energetics observed here. Another mechanism for the violent ejection of mass in massive stars may be required.

  • 18. Asami, Jinta
    et al.
    Kimura, Kanako Terakado
    Fujita-Fujiharu, Yoko
    Ishida, Hanako
    Zhang, Zhikuan
    Nomura, Yayoi
    Liu, Kehong
    Uemura, Tomoko
    Sato, Yumi
    Ono, Masatsugu
    Yamamoto, Masaki
    Noda, Takeshi
    Shigematsu, Hideki
    Drew, David
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Iwata, So
    Shimizu, Toshiyuki
    Nomura, Norimichi
    Ohto, Umeharu
    Structure of the bile acid transporter and HBV receptor NTCP2022In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 606, no 7916, p. 1021-1026Article in journal (Refereed)
    Abstract [en]

    Chronic infection with hepatitis B virus (HBV) affects more than 290 million people worldwide, is a major cause of cirrhosis and hepatocellular carcinoma, and results in an estimated 820,000 deaths annually. For HBV infection to be established, a molecular interaction is required between the large glycoproteins of the virus envelope (known as LHBs) and the host entry receptor sodium taurocholate co-transporting polypeptide (NTCP), a sodium-dependent bile acid transporter from the blood to hepatocytes. However, the molecular basis for the virus–transporter interaction is poorly understood. Here we report the cryo-electron microscopy structures of human, bovine and rat NTCPs in the apo state, which reveal the presence of a tunnel across the membrane and a possible transport route for the substrate. Moreover, the cryo-electron microscopy structure of human NTCP in the presence of the myristoylated preS1 domain of LHBs, together with mutation and transport assays, suggest a binding mode in which preS1 and the substrate compete for the extracellular opening of the tunnel in NTCP. Our preS1 domain interaction analysis enables a mechanistic interpretation of naturally occurring HBV-insusceptible mutations in human NTCP. Together, our findings provide a structural framework for HBV recognition and a mechanistic understanding of sodium-dependent bile acid translocation by mammalian NTCPs. 

  • 19. Baker, C. J.
    et al.
    Bertsche, W.
    Capra, A.
    Carruth, C.
    Cesar, C. L.
    Charlton, M.
    Christensen, A.
    Collister, R.
    Cridland Mathad, A.
    Eriksson, S.
    Evans, A.
    Evetts, N.
    Fajans, J.
    Friesen, T.
    Fujiwara, M. C.
    Gill, D. R.
    Grandemange, P.
    Granum, P.
    Hangst, J. S.
    Hardy, W. N.
    Hayden, M. E.
    Hodgkinson, D.
    Hunter, E.
    Isaac, C. A.
    Johnson, M. A.
    Jones, J. M.
    Jones, S. A.
    Jonsell, Svante
    Stockholm University, Faculty of Science, Department of Physics.
    Khramov, A.
    Knapp, P.
    Kurchaninov, L.
    Madsen, N.
    Maxwell, D.
    McKenna, J. T. K.
    Menary, S.
    Michan, J. M.
    Momose, T.
    Mullan, P. S.
    Munich, J. J.
    Olchanski, K.
    Olin, A.
    Peszka, J.
    Powell, A.
    Pusa, P.
    Rasmussen, C. Ø.
    Robicheaux, F.
    Sacramento, R. L.
    Sameed, M.
    Sarid, E.
    Silveira, D. M.
    Starko, D. M.
    So, C.
    Stutter, G.
    Tharp, T. D.
    Thibeault, A.
    Thompson, R. I.
    van der Werf, D. P.
    Wurtele, J. S.
    Laser cooling of antihydrogen atoms2021In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 592, no 7852, p. 35-42Article in journal (Refereed)
    Abstract [en]

    The photon-the quantum excitation of the electromagnetic field-is massless but carries momentum. A photon can therefore exert a force on an object upon collision(1). Slowing the translational motion of atoms and ions by application of such a force(2,3), known as laser cooling, was first demonstrated 40 years ago(4,5). It revolutionized atomic physics over the following decades(6-8), and it is now a workhorse in many fields, including studies on quantum degenerate gases, quantum information, atomic clocks and tests of fundamental physics. However, this technique has not yet been applied to antimatter. Here we demonstrate laser cooling of antihydrogen(9), the antimatter atom consisting of an antiproton and a positron. By exciting the 1S-2P transition in antihydrogen with pulsed, narrow-linewidth, Lyman-alpha laser radiation(10,11), we Doppler-cool a sample of magnetically trapped antihydrogen. Although we apply laser cooling in only one dimension, the trap couples the longitudinal and transverse motions of the anti-atoms, leading to cooling in all three dimensions. We observe a reduction in the median transverse energy by more than an order of magnitude-with a substantial fraction of the anti-atoms attaining submicroelectronvolt transverse kinetic energies. We also report the observation of the laser-driven 1S-2S transition in samples of laser-cooled antihydrogen atoms. The observed spectral line is approximately four times narrower than that obtained without laser cooling. The demonstration of laser cooling and its immediate application has far-reaching implications for antimatter studies. A more localized, denser and colder sample of antihydrogen will drastically improve spectroscopic(11-13) and gravitational(14) studies of antihydrogen in ongoing experiments. Furthermore, the demonstrated ability to manipulate the motion of antimatter atoms by laser light will potentially provide ground-breaking opportunities for future experiments, such as anti-atomic fountains, anti-atom interferometry and the creation of antimatter molecules.

  • 20. Baronti, Lorenzo
    et al.
    Guzzetti, Ileana
    Ebrahimi, Parisa
    Friebe Sandoz, Sarah
    Steiner, Emilie
    Schlagnitweit, Judith
    Fromm, Bastian
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Silva, Luis
    Fontana, Carolina
    Chen, Alan A.
    Petzold, Katja
    Base-pair conformational switch modulates miR-34a targeting of Sirt1 mRNA2020In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 583, no 7814, p. 139-144Article in journal (Refereed)
    Abstract [en]

    MicroRNAs (miRNAs) regulate the levels of translation of messenger RNAs (mRNAs). At present, the major parameter that can explain the selection of the target mRNA and the efficiency of translation repression is the base pairing between the 'seed' region of the miRNA and its counterpart mRNA(1). Here we use R-1 rho relaxation-dispersion nuclear magnetic resonance(2) and molecular simulations(3) to reveal a dynamic switch-based on the rearrangement of a single base pair in the miRNA-mRNA duplex-that elongates a weak five-base-pair seed to a complete seven-base-pair seed. This switch also causes coaxial stacking of the seed and supplementary helix fitting into human Argonaute 2 protein (Ago2), reminiscent of an active state in prokaryotic Ago(4,5). Stabilizing this transient state leads to enhanced repression of the target mRNA in cells, revealing the importance of this miRNA-mRNA structure. Our observations tie together previous findings regarding the stepwise miRNA targeting process from an initial 'screening' state to an 'active' state, and unveil the role of the RNA duplex beyond the seed in Ago2. Repression of a messenger RNA by a cognate microRNA depends not only on complementary base pairing, but also on the rearrangement of a single base pair, producing a conformation that fits better within the human Ago2 protein.

  • 21. Bergström, Anders
    et al.
    Stanton, David W. G.
    Taron, Ulrike H.
    Frantz, Laurent
    Sinding, Mikkel-Holger S.
    Ersmark, Erik
    Pfrengle, Saskia
    Cassatt-Johnstone, Molly
    Lebrasseur, Ophélie
    Girdland-Flink, Linus
    Fernandes, Daniel M.
    Ollivier, Morgane
    Speidel, Leo
    Gopalakrishnan, Shyam
    Westbury, Michael V.
    Ramos-Madrigal, Jazmin
    Feuerborn, Tatiana R.
    Reiter, Ella
    Gretzinger, Joscha
    Münzel, Susanne C.
    Swali, Pooja
    Conard, Nicholas J.
    Carøe, Christian
    Haile, James
    Linderholm, Anna
    Stockholm University, Faculty of Science, Department of Geological Sciences. Centre for Palaeogenetics, Sweden; University of Oxford, UK; Texas A&M University, USA.
    Androsov, Semyon
    Barnes, Ian
    Baumann, Chris
    Benecke, Norbert
    Bocherens, Hervé
    Brace, Selina
    Carden, Ruth F.
    Drucker, Dorothée G.
    Fedorov, Sergey
    Gasparik, Mihály
    Germonpré, Mietje
    Grigoriev, Semyon
    Groves, Pam
    Hertwig, Stefan T.
    Ivanova, Varvara V.
    Janssens, Luc
    Jennings, Richard P.
    Kasparov, Aleksei K.
    Kirillova, Irina V.
    Kurmaniyazov, Islam
    Kuzmin, Yaroslav V.
    Kosintsev, Pavel A.
    Lázničková-Galetová, Martina
    Leduc, Charlotte
    Nikolskiy, Pavel
    Nussbaumer, Marc
    O'Drisceoil, Cóilín
    Orlando, Ludovic
    Outram, Alan
    Pavlova, Elena Y.
    Perri, Angela R.
    Pilot, Małgorzata
    Pitulko, Vladimir V.
    Plotnikov, Valerii V.
    Protopopov, Albert V.
    Rehazek, André
    Sablin, Mikhail
    Seguin-Orlando, Andaine
    Storå, Jan
    Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies.
    Verjux, Christian
    Zaibert, Victor F.
    Zazula, Grant
    Crombé, Philippe
    Hansen, Anders J.
    Willerslev, Eske
    Leonard, Jennifer A.
    Götherström, Anders
    Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies. Centre for Palaeogenetics, Sweden.
    Pinhasi, Ron
    Schuenemann, Verena J.
    Hofreiter, Michael
    Gilbert, M. Thomas P.
    Shapiro, Beth
    Larson, Greger
    Krause, Johannes
    Dalén, Love
    Skoglund, Pontus
    Grey wolf genomic history reveals a dual ancestry of dogs2022In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 607, no 7918, p. 313-320Article in journal (Refereed)
    Abstract [en]

    The grey wolf (Canis lupus) was the first species to give rise to a domestic population, and they remained widespread throughout the last Ice Age when many other large mammal species went extinct. Little is known, however, about the history and possible extinction of past wolf populations or when and where the wolf progenitors of the present-day dog lineage (Canis familiaris) lived. Here we analysed 72 ancient wolf genomes spanning the last 100,000 years from Europe, Siberia and North America. We found that wolf populations were highly connected throughout the Late Pleistocene, with levels of differentiation an order of magnitude lower than they are today. This population connectivity allowed us to detect natural selection across the time series, including rapid fixation of mutations in the gene IFT88 40,000–30,000 years ago. We show that dogs are overall more closely related to ancient wolves from eastern Eurasia than to those from western Eurasia, suggesting a domestication process in the east. However, we also found that dogs in the Near East and Africa derive up to half of their ancestry from a distinct population related to modern southwest Eurasian wolves, reflecting either an independent domestication process or admixture from local wolves. None of the analysed ancient wolf genomes is a direct match for either of these dog ancestries, meaning that the exact progenitor populations remain to be located.

  • 22. Björklund, Jesper
    et al.
    Seftigen, Kristina
    Stoffel, Markus
    Fonti, Marina V.
    Kottlow, Sven
    Frank, David C.
    Esper, Jan
    Fonti, Patrick
    Goosse, Hugues
    Grudd, Håkan
    Gunnarson, Björn E.
    Stockholm University, Faculty of Science, Department of Physical Geography. Stockholm University, Faculty of Science, The Bolin Centre for Climate Research (together with KTH & SMHI).
    Nievergelt, Daniel
    Pellizzari, Elena
    Carrer, Marco
    von Arx, Georg
    Fennoscandian tree-ring anatomy shows a warmer modern than medieval climate2023In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 620, no 7972, p. 97-103Article in journal (Refereed)
    Abstract [en]

    Earth system models and various climate proxy sources indicate global warming is unprecedented during at least the Common Era. However, tree-ring proxies often estimate temperatures during the Medieval Climate Anomaly (950–1250 CE) that are similar to, or exceed, those recorded for the past century, in contrast to simulation experiments at regional scales. This not only calls into question the reliability of models and proxies but also contributes to uncertainty in future climate projections. Here we show that the current climate of the Fennoscandian Peninsula is substantially warmer than that of the medieval period. This highlights the dominant role of anthropogenic forcing in climate warming even at the regional scale, thereby reconciling inconsistencies between reconstructions and model simulations. We used an annually resolved 1,170-year-long tree-ring record that relies exclusively on tracheid anatomical measurements from Pinus sylvestris trees, providing high-fidelity measurements of instrumental temperature variability during the warm season. We therefore call for the construction of more such millennia-long records to further improve our understanding and reduce uncertainties around historical and future climate change at inter-regional and eventually global scales. 

  • 23. Blöschl, Günter
    et al.
    Kiss, Andrea
    Viglione, Alberto
    Barriendos, Mariano
    Böhm, Oliver
    Brázdil, Rudolf
    Coeur, Denis
    Demarée, Gaston
    Llasat, Maria Carmen
    Macdonald, Neil
    Retsö, Dag
    Stockholm University, Faculty of Social Sciences, Department of Economic History and International Relations.
    Roald, Lars
    Schmocker-Fackel, Petra
    Amorim, Inês
    Bělínová, Monika
    Benito, Gerardo
    Bertolin, Chiara
    Camuffo, Dario
    Cornel, Daniel
    Doktor, Radosław
    Elleder, Líbor
    Enzi, Silvia
    Garcia, João Carlos
    Glaser, Rüdiger
    Hall, Julia
    Haslinger, Klaus
    Hofstätter, Michael
    Komma, Jürgen
    Limanówka, Danuta
    Lun, David
    Panin, Andrei
    Parajka, Juraj
    Petrić, Hrvoje
    Rodrigo, Fernando S.
    Rohr, Christian
    Schönbein, Johannes
    Schulte, Lothar
    Silva, Luís Pedro
    Toonen, Willem H. J.
    Valent, Peter
    Waser, Jürgen
    Wetter, Oliver
    Current European flood-rich period exceptional compared with past 500 years2020In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 583, no 7817, p. 560-566Article in journal (Refereed)
    Abstract [en]

    There are concerns that recent climate change is altering the frequency and magnitude of river floods in an unprecedented way(1). Historical studies have identified flood-rich periods in the past half millennium in various regions of Europe(2). However, because of the low temporal resolution of existing datasets and the relatively low number of series, it has remained unclear whether Europe is currently in a flood-rich period from a long-term perspective. Here we analyse how recent decades compare with the flood history of Europe, using a new database composed of more than 100 high-resolution (sub-annual) historical flood series based on documentary evidence covering all major regions of Europe. We show that the past three decades were among the most flood-rich periods in Europe in the past 500 years, and that this period differs from other flood-rich periods in terms of its extent, air temperatures and flood seasonality. We identified nine flood-rich periods and associated regions. Among the periods richest in floods are 1560-1580 (western and central Europe), 1760-1800 (most of Europe), 1840-1870 (western and southern Europe) and 1990-2016 (western and central Europe). In most parts of Europe, previous flood-rich periods occurred during cooler-than-usual phases, but the current flood-rich period has been much warmer. Flood seasonality is also more pronounced in the recent period. For example, during previous flood and interflood periods, 41 per cent and 42 per cent of central European floods occurred in summer, respectively, compared with 55 per cent of floods in the recent period. The exceptional nature of the present-day flood-rich period calls for process-based tools for flood-risk assessment that capture the physical mechanisms involved, and management strategies that can incorporate the recent changes in risk. Analysis of thousands of historical documents recording floods in Europe shows that flooding characteristics in recent decades are unlike those of previous centuries.

  • 24. Boccaletti, Anthony
    et al.
    Thalmann, Christian
    Lagrange, Anne-Marie
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy. Max Planck Society, Germany.
    Augereau, Jean-Charles
    Schneider, Glenn
    Milli, Julien
    Grady, Carol
    Debes, John
    Langlois, Maud
    Mouillet, David
    Henning, Thomas
    Dominik, Carsten
    Maire, Anne-Lise
    Beuzit, Jean-Luc
    Carson, Joseph
    Dohlen, Kjetil
    Engler, Natalia
    Feldt, Markus
    Fusco, Thierry
    Ginski, Christian
    Girard, Julien H.
    Hines, Dean
    Kasper, Markus
    Mawet, Dimitri
    Menard, Franois
    Meyer, Michael R.
    Moutou, Claire
    Olofsson, Johan
    Rodigas, Timothy
    Sauvage, Jean-Francois
    Schlieder, Joshua
    Schmid, Hans Martin
    Turatto, Massimo
    Udry, Stephane
    Vakili, Farrokh
    Vigan, Arthur
    Wahhaj, Zahed
    Wisniewski, John
    Fast-moving features in the debris disk around AU Microscopii2015In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 526, no 7572, p. 230-+Article in journal (Refereed)
    Abstract [en]

    In the 1980s, excess infrared emission was discovered around main-sequence stars; subsequent direct-imaging observations revealed orbiting disks of cold dust to be the source(1). These 'debris disks' were thought to be by-products of planet formation because they often exhibited morphological and brightness asymmetries that may result from gravitational perturbation by planets. This was proved to be true for the beta Pictoris system, in which the known planet generates an observable warp in the disk(2-5). The nearby, young, unusually active late-type star AU Microscopii hosts a well-studied edge-on debris disk; earlier observations in the visible and near-infrared found asymmetric localized structures in the form of intensity variations along the midplane of the disk beyond a distance of 20 astronomical units(6-9). Here we report high-contrast imaging that reveals a series of five large-scale features in the southeast side of the disk, at projected separations of 10-60 astronomical units, persisting over intervals of 1-4 years. All these features appear to move away from the star at projected speeds of 4-10 kilometres per second, suggesting highly eccentric or unbound trajectories if they are associated with physical entities. The origin, localization, morphology and rapid evolution of these features are difficult to reconcile with current theories.

  • 25.
    Bohm, Christian
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Danninger, Matthias
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Finley, Chad
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Flis, Samuel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hulth, Per-Olof
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hultqvist, Klas
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Johansson, Henrik
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Seo, Seon Hee
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Walck, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Wolf, Martin
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Zoll, Marcel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    An absence of neutrinos associated with cosmic-ray acceleration in gamma-ray bursts2012In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 484, no 7394, p. 351-354Article in journal (Refereed)
    Abstract [en]

    Very energetic astrophysical events are required to accelerate cosmic rays to above 10(18) electronvolts. GRBs (c-ray bursts) have been proposed as possible candidate sources(1-3). In the GRB 'fireball' model, cosmic-ray acceleration should be accompanied by neutrinos produced in the decay of charged pions created in interactions between the high-energy cosmic-ray protons and gamma-rays(4). Previous searches for such neutrinos found none, but the constraints were weak because the sensitivity was at best approximately equal to the predicted flux(5-7). Here we report an upper limit on the flux of energetic neutrinos associated with GRBs that is at least a factor of 3.7 below the predictions(4,8-10). This implies either that GRBs are not the only sources of cosmic rays with energies exceeding 10(18) electronvolts or that the efficiency of neutrino production is much lower than has been predicted.

  • 26. Botvinik-Nezer, Rotem
    et al.
    Holzmeister, Felix
    Camerer, Colin F.
    Dreber, Anna
    Huber, Juergen
    Johannesson, Magnus
    Kirchler, Michael
    Iwanir, Roni
    Mumford, Jeanette A.
    Adcock, R. Alison
    Avesani, Paolo
    Baczkowski, Blazej M.
    Bajracharya, Aahana
    Bakst, Leah
    Ball, Sheryl
    Barilari, Marco
    Bault, Nadege
    Beaton, Derek
    Beitner, Julia
    Benoit, Roland G.
    Berkers, Ruud M. W. J.
    Bhanji, Jamil P.
    Biswal, Bharat B.
    Bobadilla-Suarez, Sebastian
    Bortolini, Tiago
    Bottenhorn, Katherine L.
    Bowring, Alexander
    Braem, Senne
    Brooks, Hayley R.
    Brudner, Emily G.
    Calderon, Cristian B.
    Camilleri, Julia A.
    Castrellon, Jaime J.
    Cecchetti, Luca
    Cieslik, Edna C.
    Cole, Zachary J.
    Collignon, Olivier
    Cox, Robert W.
    Cunningham, William A.
    Czoschke, Stefan
    Dadi, Kamalaker
    Davis, Charles P.
    Luca, Alberto De
    Delgado, Mauricio R.
    Demetriou, Lysia
    Dennison, Jeffrey B.
    Di, Xin
    Dickie, Erin W.
    Dobryakova, Ekaterina
    Donnat, Claire L.
    Dukart, Juergen
    Duncan, Niall W.
    Durnez, Joke
    Eed, Amr
    Eickhoff, Simon B.
    Erhart, Andrew
    Fontanesi, Laura
    Fricke, G. Matthew
    Fu, Shiguang
    Galvan, Adriana
    Gau, Remi
    Genon, Sarah
    Glatard, Tristan
    Glerean, Enrico
    Goeman, Jelle J.
    Golowin, Sergej A. E.
    Gonzalez-Garcia, Carlos
    Gorgolewski, Krzysztof J.
    Grady, Cheryl L.
    Green, Mikella A.
    Guassi Moreira, Joao F.
    Guest, Olivia
    Hakimi, Shabnam
    Hamilton, J. Paul
    Hancock, Roeland
    Handjaras, Giacomo
    Harry, Bronson B.
    Hawco, Colin
    Herholz, Peer
    Herman, Gabrielle
    Heunis, Stephan
    Hoffstaedter, Felix
    Hogeveen, Jeremy
    Holmes, Susan
    Hu, Chuan-Peng
    Huettel, Scott A.
    Hughes, Matthew E.
    Iacovella, Vittorio
    Iordan, Alexandru D.
    Isager, Peder M.
    Isik, Ayse I.
    Jahn, Andrew
    Johnson, Matthew R.
    Johnstone, Tom
    Joseph, Michael J. E.
    Juliano, Anthony C.
    Kable, Joseph W.
    Kassinopoulos, Michalis
    Koba, Cemal
    Kong, Xiang-Zhen
    Koscik, Timothy R.
    Kucukboyaci, Nuri Erkut
    Kuhl, Brice A.
    Kupek, Sebastian
    Laird, Angela R.
    Lamm, Claus
    Langner, Robert
    Lauharatanahirun, Nina
    Lee, Hongmi
    Lee, Sangil
    Leemans, Alexander
    Leo, Andrea
    Lesage, Elise
    Li, Flora
    Li, Monica Y. C.
    Lim, Phui Cheng
    Lintz, Evan N.
    Liphardt, Schuyler W.
    Losecaat Vermeer, Annabel B.
    Love, Bradley C.
    Mack, Michael L.
    Malpica, Norberto
    Marins, Theo
    Maumet, Camille
    McDonald, Kelsey
    McGuire, Joseph T.
    Melero, Helena
    Mendez Leal, Adriana S.
    Meyer, Benjamin
    Meyer, Kristin N.
    Mihai, Glad
    Mitsis, Georgios D.
    Moll, Jorge
    Nielson, Dylan M.
    Nilsonne, Gustav
    Stockholm University, Faculty of Social Sciences, Department of Psychology, Biological psychology. Karolinska Institutet, Sweden.
    Notter, Michael P.
    Olivetti, Emanuele
    Onicas, Adrian I.
    Papale, Paolo
    Patil, Kaustubh R.
    Peelle, Jonathan E.
    Perez, Alexandre
    Pischedda, Doris
    Poline, Jean-Baptiste
    Prystauka, Yanina
    Ray, Shruti
    Reuter-Lorenz, Patricia A.
    Reynolds, Richard C.
    Ricciardi, Emiliano
    Rieck, Jenny R.
    Rodriguez-Thompson, Anais M.
    Romyn, Anthony
    Salo, Taylor
    Samanez-Larkin, Gregory R.
    Sanz-Morales, Emilio
    Schlichting, Margaret L.
    Schultz, Douglas H.
    Shen, Qiang
    Sheridan, Margaret A.
    Silvers, Jennifer A.
    Skagerlund, Kenny
    Smith, Alec
    Smith, David V.
    Sokol-Hessner, Peter
    Steinkamp, Simon R.
    Tashjian, Sarah M.
    Thirion, Bertrand
    Thorp, John N.
    Tinghog, Gustav
    Tisdall, Loreen
    Tompson, Steven H.
    Toro-Serey, Claudio
    Torre Tresols, Juan Jesus
    Tozzi, Leonardo
    Truong, Vuong
    Turella, Luca
    van 't Veer, Anna E.
    Verguts, Tom
    Vettel, Jean M.
    Vijayarajah, Sagana
    Vo, Khoi
    Wall, Matthew B.
    Weeda, Wouter D.
    Weis, Susanne
    White, David J.
    Wisniewski, David
    Xifra-Porxas, Alba
    Yearling, Emily A.
    Yoon, Sangsuk
    Yuan, Rui
    Yuen, Kenneth S. L.
    Zhang, Lei
    Zhang, Xu
    Zosky, Joshua E.
    Nichols, Thomas E.
    Poldrack, Russell A.
    Schonberg, Tom
    Variability in the analysis of a single neuroimaging dataset by many teams2020In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 582, p. 84-88Article in journal (Refereed)
    Abstract [en]

    Data analysis workflows in many scientific domains have become increasingly complex and flexible. Here we assess the effect of this flexibility on the results of functional magnetic resonance imaging by asking 70 independent teams to analyse the same dataset, testing the same 9 ex-ante hypotheses(1). The flexibility of analytical approaches is exemplified by the fact that no two teams chose identical workflows to analyse the data. This flexibility resulted in sizeable variation in the results of hypothesis tests, even for teams whose statistical maps were highly correlated at intermediate stages of the analysis pipeline. Variation in reported results was related to several aspects of analysis methodology. Notably, a meta-analytical approach that aggregated information across teams yielded a significant consensus in activated regions. Furthermore, prediction markets of researchers in the field revealed an overestimation of the likelihood of significant findings, even by researchers with direct knowledge of the dataset(2-5). Our findings show that analytical flexibility can have substantial effects on scientific conclusions, and identify factors that may be related to variability in the analysis of functional magnetic resonance imaging. The results emphasize the importance of validating and sharing complex analysis workflows, and demonstrate the need for performing and reporting multiple analyses of the same data. Potential approaches that could be used to mitigate issues related to analytical variability are discussed. The results obtained by seventy different teams analysing the same functional magnetic resonance imaging dataset show substantial variation, highlighting the influence of analytical choices and the importance of sharing workflows publicly and performing multiple analyses.

  • 27. Burdge, Kevin B.
    et al.
    Marsh, Thomas R.
    Fuller, Jim
    Bellm, Eric C.
    Caiazzo, Ilaria
    Chakrabarty, Deepto
    Coughlin, Michael W.
    De, Kishalay
    Dhillon, V. S.
    Graham, Matthew J.
    Rodríguez-Gil, Pablo
    Jaodand, Amruta D.
    Kaplan, David L.
    Kara, Erin
    Kong, Albert K. H.
    Kulkarni, S. R.
    Li, Kwan-Lok
    Littlefair, S. P.
    Majid, Walid A.
    Mróz, Przemek
    Pearlman, Aaron B.
    Phinney, E. S.
    van Roestel, Jan
    Simcoe, Robert A.
    Andreoni, Igor
    Drake, Andrew J.
    Dekany, Richard G.
    Duev, Dmitry A.
    Kool, Erik C.
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Mahabal, Ashish A.
    Medford, Michael S.
    Riddle, Reed
    Prince, Thomas A.
    A 62-minute orbital period black widow binary in a wide hierarchical triple2022In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 605, no 7908, p. 41-45Article in journal (Refereed)
    Abstract [en]

    Over a dozen millisecond pulsars are ablating low-mass companions in close binary systems. In the original 'black widow', the eight-hour orbital period eclipsing pulsar PSR J1959+2048 (PSR B1957+20)(1), high-energy emission originating from the pulsar2 is irradiating and may eventually destroy(3) a low-mass companion. These systems are not only physical laboratories that reveal the interesting results of exposing a close companion star to the relativistic energy output of a pulsar, but are also believed to harbour some of the most massive neutron stars(4), allowing for robust tests of the neutron star equation of state. Here we report observations of ZTF J1406+1222, a wide hierarchical triple hosting a 62-minute orbital period black widow candidate, the optical flux of which varies by a factor of more than ten. ZTF J1406+1222 pushes the boundaries of evolutionary models(5), falling below the 80-minute minimum orbital period of hydrogen-rich systems. The wide tertiary companion is a rare low-metallicity cool subdwarf star, and the system has a Galactic halo orbit consistent with passing near the Galactic Centre, making it a probe of formation channels, neutron star kick physics(6) and binary evolution.

  • 28.
    Cabello, Adán
    Stockholm University, Faculty of Science, Department of Physics.
    Quantum physics: Correlations without parts2011In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 474, no 7352, p. 456-458Article in journal (Refereed)
  • 29. Cabral, Rita A.
    et al.
    Jackson, Matthew G.
    Rose-Koga, Estelle F.
    Koga, Kenneth T.
    Whitehouse, Martin J.
    Stockholm University, Faculty of Science, Department of Geological Sciences. Swedish Museum of Natural History, Sweden.
    Antonelli, Michael A.
    Farquhar, James
    Day, James M. D.
    Hauri, Erik H.
    Anomalous sulphur isotopes in plume lavas reveal deep mantle storage of Archaean crust2013In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 496, no 7446, p. 490-494Article in journal (Refereed)
    Abstract [en]

    Basaltic lavas erupted at some oceanic intraplate hotspot volcanoes are thought to sample ancient subducted crustal materials(1,2). However, the residence time of these subducted materials in the mantle is uncertain and model-dependent(3), and compelling evidence for their return to the surface in regions of mantle upwelling beneath hotspots is lacking. Here we report anomalous sulphur isotope signatures indicating mass-independent fractionation (MIF) in olivine-hosted sulphides from 20-million-year-old ocean island basalts from Mangaia, Cook Islands (Polynesia), which have been suggested to sample recycled oceanic crust(3,4). Terrestrial MIF sulphur isotope signatures (in which the amount of fractionation does not scale in proportion with the difference in the masses of the isotopes) were generated exclusively through atmospheric photochemical reactions until about 2.45 billion years ago(5-7). Therefore, the discovery of MIF sulphur in these young plume lavas suggests that sulphur-probably derived from hydrothermally altered oceanic crust-was subducted into the mantle before 2.45 billion years ago and recycled into the mantle source of Mangaia lavas. These new data provide evidence for ancient materials, with negative Delta S-33 values, in the mantle source for Mangaia lavas. Our data also complement evidence for recycling of the sulphur content of ancient sedimentary materials to the subcontinental lithospheric mantle that has been identified in diamond-hosted sulphide inclusions(8,9). This Archaean age for recycled oceanic crust also provides key constraints on the length of time that subducted crustal material can survive in the mantle, and on the timescales of mantle convection from subduction to upwelling beneath hotspots.

  • 30.
    Cannon, Barbara
    et al.
    Stockholm University, Faculty of Science, The Wenner-Gren Institute.
    Nedergaard, Jan
    Stockholm University, Faculty of Science, The Wenner-Gren Institute.
    Neither brown nor white2012In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 488, no 7411, p. 286-287Article in journal (Other academic)
    Abstract [en]

    Fat cells are usually thought of as being either energy-storing white fat cells or food-burning brown fat cells. The identification of a third type of fat cell in mice and humans might open up new avenues for combating obesity.

  • 31. Cao, Yi
    et al.
    Kulkarni, S. R.
    Howell, D. Andrew
    Gal-Yam, Avishay
    Kasliwal, Mansi M.
    Valenti, Stefano
    Johansson, Joel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Amanullah, Rahman
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Sollerman, Jesper
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Taddia, Francesco
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Horesh, Assaf
    Sagiv, Ilan
    Cenko, S. Bradley
    Nugent, Peter E.
    Arcavi, Iair
    Surace, Jason
    Wozniak, P. R.
    Moody, Daniela I.
    Rebbapragada, Umaa D.
    Bue, Brian D.
    Gehrels, Neil
    A strong ultraviolet pulse from a newborn type Ia supernova2015In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 521, no 7552, p. 328-+Article in journal (Refereed)
    Abstract [en]

    Type Ia supernovae(1) are destructive explosions of carbon-oxygen white dwarfs(2,3). Although they are used empirically to measure cosmological distances(4-6), the nature of their progenitors remains mysterious(3). One of the leading progenitor models, called the single degenerate channel, hypothesizes that a white dwarf accretes matter from a companion star and the resulting increase in its central pressure and temperature ignites thermonuclear explosion(3,7,8). Here we report observations with the Swift Space Telescope of strong but declining ultraviolet emission from a type Ia supernova within four days of its explosion. This emission is consistent with theoretical expectations of collision between material ejected by the supernova and a companion star(9), and therefore provides evidence that some type Ia supernovae arise from the single degenerate channel.

  • 32. Cappellini, Enrico
    et al.
    Welker, Frido
    Pandolfi, Luca
    Ramos-Madrigal, Jazmín
    Samodova, Diana
    Rüther, Patrick L.
    Fotakis, Anna K.
    Lyon, David
    Moreno-Mayar, J. Víctor
    Bukhsianidze, Maia
    Rakownikow Jersie-Christensen, Rosa
    Mackie, Meaghan
    Ginolhac, Aurélien
    Ferring, Reid
    Tappen, Martha
    Palkopoulou, Eleftheria
    Dickinson, Marc R.
    Stafford, Thomas W.
    Chan, Yvonne L.
    Götherström, Anders
    Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies.
    Nathan, Senthilvel K. S. S.
    Heintzman, Peter D.
    Kapp, Joshua D.
    Kirillova, Irina
    Moodley, Yoshan
    Agusti, Jordi
    Kahlke, Ralf-Dietrich
    Kiladze, Gocha
    Martínez-Navarro, Bienvenido
    Liu, Shanlin
    Sandoval Velasco, Marcela
    Sinding, Mikkel-Holger S.
    Kelstrup, Christian D.
    Allentoft, Morten E.
    Orlando, Ludovic
    Penkman, Kirsty
    Shapiro, Beth
    Rook, Lorenzo
    Dalén, Love
    Gilbert, M. Thomas P.
    Olsen, Jesper V.
    Lordkipanidze, David
    Willerslev, Eske
    Early Pleistocene enamel proteome from Dmanisi resolves Stephanorhinus phylogeny2019In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 574, no 7776, p. 103-107Article in journal (Refereed)
    Abstract [en]

    The sequencing of ancient DNA has enabled the reconstruction of speciation, migration and admixture events for extinct taxa(1). However, the irreversible post-mortem degradation(2) of ancient DNA has so far limited its recovery-outside permafrost areasto specimens that are not older than approximately 0.5 million years (Myr)(3). By contrast, tandem mass spectrometry has enabled the sequencing of approximately 1.5-Myr-old collagen type I-4. and suggested the presence of protein residues in fossils of the Cretaceous period(5)-although with limited phylogenetic use(6). In the absence of molecular evidence, the speciation of several extinct species of the Early and Middle Pleistocene epoch remains contentious. Here we address the phylogenetic relationships of the Eurasian Rhinocerotidae of the Pleistocene epoch(7-9), using the proteome of dental enamel from a Stephanorhinus tooth that is approximately 1.77-Myr old, recovered from the archaeological site of Dmanisi (South Caucasus, Georgia)(10). Molecular phylogenetic analyses place this Stephanorhinus as a sister group to the Glade formed by the woolly rhinoceros (Coelodonta antiquitatis) and Merck's rhinoceros (Stephanorhinus kirchbergensis). We show that Coelodonta evolved from an early Stephanorhinus lineage, and that this latter genus includes at least two distinct evolutionary lines. The genus Stephanorhinus is therefore currently paraphyletic, and its systematic revision is needed. We demonstrate that sequencing the proteome of Early Pleistocene dental enamel overcomes the limitations of phylogenetic inference based on ancient collagen or DNA. Our approach also provides additional information about the sex and taxonomic assignment of other specimens from Dmanisi. Our findings reveal that proteomic investigation of ancient dental enamel-which is the hardest tissue in vertebrates(11), and is highly abundant in the fossil record-can push the reconstruction of molecular evolution further back into the Early Pleistocene epoch, beyond the currently known limits of ancient DNA preservation.

  • 33. Carvalhais, Nuno
    et al.
    Forkel, Matthias
    Khomik, Myroslava
    Bellarby, Jessica
    Jung, Martin
    Migliavacca, Mirco
    Mu, Mingquan
    Saatchi, Sassan
    Santoro, Maurizio
    Thurner, Martin
    Weber, Ulrich
    Ahrens, Bernhard
    Beer, Christian
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM). Max Planck Society, Germany.
    Cescatti, Alessandro
    Randerson, James T.
    Reichstein, Markus
    Global covariation of carbon turnover times with climate in terrestrial ecosystems2014In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 514, no 7521, p. 213-+Article in journal (Refereed)
    Abstract [en]

    The response of the terrestrial carbon cycle to climate change is among the largest uncertainties affecting future climate change projections(1,2). The feedback between the terrestrial carbon cycle and climate is partly determined by changes in the turnover time of carbon in land ecosystems, which in turn is an ecosystem property that emerges from the interplay between climate, soil and vegetation type(3-6). Here we present a global, spatially explicit and observation-based assessment of whole-ecosystem carbon turnover times that combines new estimates of vegetation and soil organic carbon stocks and fluxes. We find that the overall mean global carbon turnover time is 23(4)(+7) years (95 per cent confidence interval). Onaverage, carbon resides in the vegetation and soil near the Equator for a shorter time than at latitudes north of 75 degrees north (mean turnover times of 15 and 255 years, respectively). We identify a clear dependence of the turnover time on temperature, as expected from our present understanding of temperature controls on ecosystem dynamics. Surprisingly, our analysis also reveals a similarly strong association between turnover time and precipitation. Moreover, we find that the ecosystem carbon turnover times simulated by state-of-the-art coupled climate/carbon-cycle models vary widely and that numerical simulations, on average, tend to underestimate the global carbon turnover time by 36 per cent. The models show stronger spatial relationships with temperature than do observation-based estimates, but generally do not reproduce the strong relationships with precipitation and predict faster carbon turnover in many semiarid regions. Our findings suggest that future climate/carbon-cycle feedbacks may depend more strongly on changes in the hydrological cycle than is expected at present and is considered in Earth system models.

  • 34.
    Charpentier Ljungqvist, Fredrik
    et al.
    Stockholm University, Faculty of Humanities, Department of History.
    Krusic, Paul J.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Sundqvist, Hanna S.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Zorita, Eduardo
    Brattström, Gudrun
    Stockholm University, Faculty of Science, Department of Mathematics.
    Frank, David
    Northern Hemisphere hydroclimate variability over the past twelve centuries2016In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 532, no 7597, p. 94-98Article in journal (Refereed)
    Abstract [en]

    Accurate modelling and prediction of the local to continental-scale hydroclimate response to global warming is essential given the strong impact of hydroclimate on ecosystem functioning, crop yields, water resources, and economic security. However, uncertainty in hydroclimate projections remains large, in part due to the short length of instrumental measurements available with which to assess climate models. Here we present a spatial reconstruction of hydroclimate variability over the past twelve centuries across the Northern Hemisphere derived from a network of 196 at least millennium-long proxy records. We use this reconstruction to place recent hydrological changes and future precipitation scenarios in a long-term context of spatially resolved and temporally persistent hydroclimate patterns. We find a larger percentage of land area with relatively wetter conditions in the ninth to eleventh and the twentieth centuries, whereas drier conditions are more widespread between the twelfth and nineteenth centuries. Our reconstruction reveals that prominent seesaw patterns of alternating moisture regimes observed in instrumental data across the Mediterranean, western USA, and China have operated consistently over the past twelve centuries. Using an updated compilation of 128 temperature proxy records, we assess the relationship between the reconstructed centennial-scale Northern Hemisphere hydroclimate and temperature variability. Even though dry and wet conditions occurred over extensive areas under both warm and cold climate regimes, a statistically significant co-variability of hydroclimate and temperature is evident for particular regions. We compare the reconstructed hydroclimate anomalies with coupled atmosphere-ocean general circulation model simulations and find reasonable agreement during pre-industrial times. However, the intensification of the twentieth-century-mean hydroclimate anomalies in the simulations, as compared to previous centuries, is not supported by our new multi-proxy reconstruction. This finding suggests that much work remains before we can model hydroclimate variability accurately, and highlights the importance of using palaeoclimate data to place recent and predicted hydroclimate changes in a millennium-long context.

  • 35. Cho, Hae Sung
    et al.
    Deng, Hexiang
    Miyasaka, Keiichi
    Dong, Zhiyue
    Cho, Minhyung
    Neimark, Alexander V.
    Kang, Jeung Ku
    Yaghi, Omar M.
    Terasaki, Osamu
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Graduate School of Energy, Environment, Water and Sustainability, South Korea.
    Extra adsorption and adsorbate superlattice formation in metal-organic frameworks2015In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 527, no 7579, p. 503-U193Article in journal (Refereed)
    Abstract [en]

    Metal-organic frameworks (MOFs) have a high internal surface area and widely tunable composition(1,2), which make them useful for applications involving adsorption, such as hydrogen, methane or carbon dioxide storage(3-9). The selectivity and uptake capacity of the adsorption process are determined by interactions involving the adsorbates and their porous host materials. But, although the interactions of adsorbate molecules with the internal MOF surface(10-17) and also amongst themselves within individual pores(18-22) have been extensively studied, adsorbate-adsorbate interactions across pore walls have not been explored. Here we show that local strain in the MOF, induced by pore filling, can give rise to collective and long-range adsorbate-adsorbate interactions and the formation of adsorbate superlattices that extend beyond an original MOF unit cell. Specifically, we use in situ small-angle X-ray scattering to track and map the distribution and ordering of adsorbate molecules in five members of the mesoporous MOF-74 series along entire adsorption-desorption isotherms. We find in all cases that the capillary condensation that fills the pores gives rise to the formation of 'extra adsorption domains'-that is, domains spanning several neighbouring pores, which have a higher adsorbate density than non-domain pores. In the case of one MOF, IRMOF-74-V-hex, these domains form a superlattice structure that is difficult to reconcile with the prevailing view of pore-filling as a stochastic process. The visualization of the adsorption process provided by our data, with clear evidence for initial adsorbate aggregation in distinct domains and ordering before an even distribution is finally reached, should help to improve our understanding of this process and may thereby improve our ability to exploit it practically.

  • 36. Choi, Minkee
    et al.
    Na, Kyungsu
    Kim, Jeongnam
    Sakamoto, Yasuhiro
    Terasaki, Osamu
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Ryoo, Ryong
    Stable single-unit-cell nanosheets of zeolite MFI as active and long-lived catalysts2009In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 461, no 7261, p. 246-249Article in journal (Refereed)
    Abstract [en]

    Zeolites-microporous crystalline aluminosilicates-are widely used in petrochemistry and fine-chemical synthesis(1-3) because strong acid sites within their uniform micropores enable size- and shape-selective catalysis. But the very presence of the micropores, with aperture diameters below 1 nm, often goes hand-in-hand with diffusion limitations(3-5) that adversely affect catalytic activity. The problem can be overcome by reducing the thickness of the zeolite crystals, which reduces diffusion path lengths and thus improves molecular diffusion(4,5). This has been realized by synthesizing zeolite nanocrystals(6), by exfoliating layered zeolites(7-9), and by introducing mesopores in the microporous material through templating strategies(10-17) or demetallation processes(18-22). But except for the exfoliation, none of these strategies has produced 'ultrathin' zeolites with thicknesses below 5 nm. Here we show that appropriately designed bifunctional surfactants can direct the formation of zeolite structures on themesoporous and microporous length scales simultaneously and thus yield MFI (ZSM-5, one of the most important catalysts in the petrochemical industry) zeolite nanosheets that are only 2 nm thick, which corresponds to the b-axis dimension of a single MFI unit cell. The large number of acid sites on the external surface of these zeolites renders them highly active for the catalytic conversion of large organic molecules, and the reduced crystal thickness facilitates diffusion and thereby dramatically suppresses catalyst deactivation through coke deposition during methanol-to-gasoline conversion. We expect that our synthesis approach could be applied to other zeolites to improve their performance in a range of important catalytic applications.

     

  • 37. Contreras, F.-Xabier
    et al.
    Ernst, Andreas M.
    Haberkant, Per
    Björkholm, Patrik
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Lindahl, Erik
    Gönen, Basak
    Tischer, Christian
    Elofsson, Arne
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    von Heijne, Gunnar
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Thiele, Christoph
    Pepperkok, Rainer
    Wieland, Felix
    Brügger, Britta
    Molecular recognition of a single sphingolipid species by a protein’s transmembrane domain2012In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 481, no 7382, p. 525-529Article in journal (Refereed)
    Abstract [en]

    Functioning and processing of membrane proteins critically depend on the way their transmembrane segments are embedded in the membrane. Sphingolipids are structural components of membranes and can also act as intracellular second messengers. Not much is known of sphingolipids binding to transmembrane domains (TMDs) of proteins within the hydrophobic bilayer, and how this could affect protein function. Here we show a direct and highly specific interaction of exclusively one sphingomyelin species, SM 18, with the TMD of the COPI machinery protein p24 (ref. 2). Strikingly, the interaction depends on both the headgroup and the backbone of the sphingolipid, and on a signature sequence (VXXTLXXIY) within the TMD. Molecular dynamics simulations show a close interaction of SM 18 with the TMD. We suggest a role of SM 18 in regulating the equilibrium between an inactive monomeric and an active oligomeric state of the p24 protein, which in turn regulates COPI-dependent transport. Bioinformatic analyses predict that the signature sequence represents a conserved sphingolipid-binding cavity in a variety of mammalian membrane proteins. Thus, in addition to a function as second messengers, sphingolipids can act as cofactors to regulate the function of transmembrane proteins. Our discovery of an unprecedented specificity of interaction of a TMD with an individual sphingolipid species adds to our understanding of why biological membranes are assembled from such a large variety of different lipids.

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  • 38. Craig, O. E.
    et al.
    Saul, H.
    Lucquin, A.
    Nishida, Y.
    Taché, K.
    Clarke, L.
    Thompson, A.
    Altoft, D. T.
    Uchiyama, J.
    Ajimoto, M.
    Gibbs, K.
    Isaksson, Sven
    Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies, Archaeological Research Laboratory. Stockholm University, Faculty of Humanities, Centre for Cultural Evolution.
    Heron, C. P.
    Jordan, P.
    Earliest evidence for the use of pottery2013In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 496, no 7445, p. 351-354Article in journal (Refereed)
    Abstract [en]

    Pottery was a hunter-gatherer innovation that first emerged in East Asia between 20,000 and 12,000 calibrated years before present(1,2) (cal BP), towards the end of the Late Pleistocene epoch, a period of time when humans were adjusting to changing climates and new environments. Ceramic container technologies were one of a range of late glacial adaptations that were pivotal to structuring subsequent cultural trajectories in different regions of the world, but the reasons for their emergence and widespread uptake are poorly understood. The first ceramic containers must have provided prehistoric hunter-gatherers with attractive new strategies for processing and consuming foodstuffs, but virtually nothing is known of how early pots were used. Here we report the chemical analysis of food residues associated with Late Pleistocene pottery, focusing on one of the best-studied prehistoric ceramic sequences in the world, the Japanese Jomon. We demonstrate that lipids can be recovered reliably from charred surface deposits adhering to pottery dating from about 15,000 to 11,800 cal BP (the Incipient Jomon period), the oldest pottery so far investigated, and that in most cases these organic compounds are unequivocally derived from processing freshwater and marine organisms. Stable isotope data support the lipid evidence and suggest that most of the 101 charred deposits analysed, from across the major islands of Japan, were derived from high-trophic-level aquatic food. Productive aquatic ecotones were heavily exploited by late glacial foragers(3), perhaps providing an initial impetus for investment in ceramic container technology, and paving the way for further intensification of pottery use by hunter-gatherers in the early Holocene epoch. Now that we have shown that it is possible to analyse organic residues from some of the world's earliest ceramic vessels, the subsequent development of this critical technology can be clarified through further widespread testing of hunter-gatherer pottery from later periods.

  • 39.
    Crona, Beatrice
    et al.
    Stockholm University, Faculty of Science, Stockholm Resilience Centre. Royal Swedish Academy of Science, Sweden.
    Wassénius, Emmy
    Stockholm University, Faculty of Science, Stockholm Resilience Centre. Royal Swedish Academy of Science, Sweden.
    Jonell, Malin
    Stockholm University, Faculty of Science, Stockholm Resilience Centre. Royal Swedish Academy of Science, Sweden.
    Koehn, J. Zachary
    Short, Rebecca
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Tigchelaar, Michelle
    Daw, Tim M.
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Golden, Christopher D.
    Gephart, Jessica A.
    Allison, Edward H.
    Bush, Simon R.
    Cao, Ling
    Cheung, William W. L.
    DeClerck, Fabrice
    Fanzo, Jessica
    Gelcich, Stefan
    Kishore, Avinash
    Halpern, Benjamin S.
    Hicks, Christina C.
    Leape, James P.
    Little, David C.
    Micheli, Fiorenza
    Naylor, Rosamond L.
    Phillips, Michael
    Selig, Elizabeth R.
    Springmann, Marco
    Sumaila, U. Rashid
    Troell, Max
    Thilsted, Shakuntala H.
    Wabnitz, Colette C. C.
    Four ways blue foods can help achieve food system ambitions across nations2023In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 616, no 7955, p. 104-112Article in journal (Refereed)
    Abstract [en]

    Blue foods, sourced in aquatic environments, are important for the economies, livelihoods, nutritional security and cultures of people in many nations. They are often nutrient rich1, generate lower emissions and impacts on land and water than many terrestrial meats2, and contribute to the health3, wellbeing and livelihoods of many rural communities4. The Blue Food Assessment recently evaluated nutritional, environmental, economic and justice dimensions of blue foods globally. Here we integrate these findings and translate them into four policy objectives to help realize the contributions that blue foods can make to national food systems around the world: ensuring supplies of critical nutrients, providing healthy alternatives to terrestrial meat, reducing dietary environmental footprints and safeguarding blue food contributions to nutrition, just economies and livelihoods under a changing climate. To account for how context-specific environmental, socio-economic and cultural aspects affect this contribution, we assess the relevance of each policy objective for individual countries, and examine associated co-benefits and trade-offs at national and international scales. We find that in many African and South American nations, facilitating consumption of culturally relevant blue food, especially among nutritionally vulnerable population segments, could address vitamin B12 and omega-3 deficiencies. Meanwhile, in many global North nations, cardiovascular disease rates and large greenhouse gas footprints from ruminant meat intake could be lowered through moderate consumption of seafood with low environmental impact. The analytical framework we provide also identifies countries with high future risk, for whom climate adaptation of blue food systems will be particularly important. Overall the framework helps decision makers to assess the blue food policy objectives most relevant to their geographies, and to compare and contrast the benefits and trade-offs associated with pursuing these objectives.

  • 40. Dahl-Jensen, D.
    et al.
    Albert, M. R.
    Aldahan, A.
    Azuma, N.
    Balslev-Clausen, D.
    Baumgartner, M.
    Berggren, A. -M
    Bigler, M.
    Binder, T.
    Blunier, T.
    Bourgeois, J. C.
    Brook, E. J.
    Buchardt, S. L.
    Buizert, C.
    Capron, E.
    Chappellaz, J.
    Chung, J.
    Clausen, H. B.
    Cvijanovic, I.
    Davies, S. M.
    Ditlevsen, P.
    Eicher, O.
    Fischer, H.
    Fisher, D. A.
    Fleet, L. G.
    Gfeller, G.
    Gkinis, V.
    Gogineni, S.
    Goto-Azuma, K.
    Grinsted, A.
    Gudlaugsdottir, H.
    Guillevic, M.
    Hansen, S. B.
    Hansson, Margareta
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Hirabayashi, M.
    Hong, S.
    Hur, S. D.
    Huybrechts, P.
    Hvidberg, C. S.
    Iizuka, Yoshinori
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology. Hokkaido University, Japan.
    Jenk, T.
    Johnsen, S. J.
    Jones, T. R.
    Jouzel, J.
    Karlsson, N. B.
    Kawamura, K.
    Keegan, K.
    Kettner, E.
    Kipfstuhl, S.
    Kjaer, H. A.
    Koutnik, M.
    Kuramoto, T.
    Koehler, P.
    Laepple, T.
    Landais, A.
    Langen, P. L.
    Larsen, L. B.
    Leuenberger, D.
    Leuenberger, M.
    Leuschen, C.
    Li, J.
    Lipenkov, V.
    Martinerie, P.
    Maselli, O. J.
    Masson-Delmotte, V.
    McConnell, J. R.
    Miller, H.
    Mini, O.
    Miyamoto, A.
    Montagnat-Rentier, M.
    Mulvaney, R.
    Muscheler, R.
    Orsi, A. J.
    Paden, J.
    Panton, C.
    Pattyn, F.
    Petit, J. -R
    Pol, K.
    Popp, T.
    Possnert, G.
    Prie, F.
    Prokopiou, M.
    Quiquet, A.
    Rasmussen, S. O.
    Raynaud, D.
    Ren, J.
    Reutenauer, C.
    Ritz, C.
    Rockmann, T.
    Rosen, J. L.
    Rubino, M.
    Rybak, O.
    Samyn, D.
    Sapart, C. J.
    Schilt, A.
    Schmidt, A. M. Z.
    Schwander, J.
    Schuepbach, S.
    Seierstad, I.
    Severinghaus, J. P.
    Sheldon, S.
    Simonsen, S. B.
    Sjolte, J.
    Solgaard, A. M.
    Sowers, T.
    Sperlich, P.
    Steen-Larsen, H. C.
    Steffen, K.
    Steffensen, J. P.
    Steinhage, D.
    Stocker, T. F.
    Stowasser, C.
    Sturevik, A. S.
    Sturges, W. T.
    Sveinbjornsdottir, A.
    Svensson, A.
    Tison, J. -L
    Uetake, J.
    Vallelonga, P.
    van de Wal, R. S. W.
    van der Wel, G.
    Vaughn, B. H.
    Vinther, B.
    Waddington, E.
    Wegner, A.
    Weikusat, I.
    White, J. W. C.
    Wilhelms, F.
    Winstrup, M.
    Witrant, E.
    Wolff, E. W.
    Xiao, C.
    Zheng, J.
    Eemian interglacial reconstructed from a Greenland folded ice core2013In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 493, no 7433, p. 489-494Article in journal (Refereed)
    Abstract [en]

    Efforts to extract a Greenland ice core with a complete record of the Eemian interglacial (130,000 to 115,000 years ago) have until now been unsuccessful. The response of the Greenland ice sheet to the warmer-than-present climate of the Eemian has thus remained unclear. Here we present the new North Greenland Eemian Ice Drilling ('NEEM') ice core and show only a modest ice-sheet response to the strong warming in the early Eemian. We reconstructed the Eemian record from folded ice using globally homogeneous parameters known from dated Greenland and Antarctic ice-core records. On the basis of water stable isotopes, NEEM surface temperatures after the onset of the Eemian (126,000 years ago) peaked at 8 +/- 4 degrees Celsius above the mean of the past millennium, followed by a gradual cooling that was probably driven by the decreasing summer insolation. Between 128,000 and 122,000 years ago, the thickness of the northwest Greenland ice sheet decreased by 400 +/- 250 metres, reaching surface elevations 122,000 years ago of 130 +/- 300 metres lower than the present. Extensive surface melt occurred at the NEEM site during the Eemian, a phenomenon witnessed when melt layers formed again at NEEM during the exceptional heat of July 2012. With additional warming, surface melt might become more common in the future.

  • 41.
    Dawid, Richard
    Stockholm University, Faculty of Humanities, Department of Philosophy.
    Theoretical physics: The emperor's new physics: Fashion, Faith, and Fantasy in the New Physics of the Universe, by Roger Penrose2016In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 538, no 7623, p. 36-37Article in journal (Other academic)
  • 42. de lavergne, C.
    et al.
    Madec, G.
    Roquet, Fabien
    Stockholm University, Faculty of Science, Department of Meteorology .
    Holmes, R. M.
    McDougall, T. J.
    Abyssal ocean overturning shaped by seafloor distribution2017In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 551, no 7679, p. 181-186Article in journal (Refereed)
    Abstract [en]

    The abyssal ocean is broadly characterized by northward flow of the densest waters and southward flow of less-dense waters above them. Understanding what controls the strength and structure of these interhemispheric flows-referred to as the abyssal overturning circulation-is key to quantifying the ocean's ability to store carbon and heat on timescales exceeding a century. Here we show that, north of 32 degrees S, the depth distribution of the seafloor compels dense southernorigin waters to flow northward below a depth of about 4 kilometres and to return southward predominantly at depths greater than 2.5 kilometres. Unless ventilated from the north, the overlying mid-depths (1 to 2.5 kilometres deep) host comparatively weak mean meridional flow. Backed by analysis of historical radiocarbon measurements, the findings imply that the geometry of the Pacific, Indian and Atlantic basins places a major external constraint on the overturning structure.

  • 43. de Vries, B. L.
    et al.
    Acke, B.
    Blommaert, J. A. D. L.
    Waelkens, C.
    Waters, L. B. F. M.
    Vandenbussche, B.
    Min, M.
    Olofsson, Göran
    Stockholm University, Faculty of Science, Department of Astronomy.
    Dominik, C.
    Decin, L.
    Barlow, M. J.
    Brandeker, Alexis
    Stockholm University, Faculty of Science, Department of Astronomy.
    Di Francesco, J.
    Glauser, A. M.
    Greaves, J.
    Harvey, P. M.
    Holland, W. S.
    Ivison, R. J.
    Liseau, R.
    Pantin, E. E.
    Pilbratt, G. L.
    Royer, P.
    Sibthorpe, B.
    Comet-like mineralogy of olivine crystals in an extrasolar proto-Kuiper belt2012In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 490, no 7418, p. 74-76Article in journal (Refereed)
    Abstract [en]

    Some planetary systems harbour debris disks containing planetesimals such as asteroids and comets(1). Collisions between such bodies produce small dust particles(2), the spectral features of which reveal their composition and, hence, that of their parent bodies. A measurement of the composition of olivine crystals (Mg2-2xFe2xSiO4) has been done for the protoplanetary disk HD 100546 (refs 3, 4) and for olivine crystals in the warm inner parts of planetary systems. The latter compares well with the iron-rich olivine in asteroids(5,6) (x approximate to 0.29). In the cold outskirts of the beta Pictoris system, an analogue to the young Solar System, olivine crystals were detected(7) but their composition remained undetermined, leaving unknown how the composition of the bulk of Solar System cometary olivine grains compares with that of extrasolar comets(8,9). Here we report the detection of the 69-micrometre-wavelength band of olivine crystals in the spectrum of beta Pictoris. Because the disk is optically thin, we can associate the crystals with an extrasolar proto-Kuiper belt a distance of 15-45 astronomical units from the star (one astronomical unit is the Sun-Earth distance), determine their magnesium-rich composition (x = 0.01 +/- 0.001) and show that they make up 3.6 +/- 1.0 per cent of the total dust mass. These values are strikingly similar to those for the dust emitted by the most primitive comets in the Solar System(8-10), even though beta Pictoris is more massive and more luminous and has a different planetary system architecture.

  • 44. Decin, L.
    et al.
    Agundez, M.
    Barlow, M. J.
    Daniel, F.
    Cernicharo, J.
    Lombaert, R.
    De Beck, E.
    Royer, P.
    Vandenbussche, B.
    Wesson, R.
    Polehampton, E. T.
    Blommaert, J. A. D. L.
    De Meester, W.
    Exter, K.
    Feuchtgruber, H.
    Gear, W. K.
    Gomez, H. L.
    Groenewegen, M. A. T.
    Guelin, M.
    Hargrave, P. C.
    Huygen, R.
    Imhof, P.
    Ivison, R. J.
    Jean, C.
    Kahane, C.
    Kerschbaum, F.
    Leeks, S. J.
    Lim, T.
    Matsuura, M.
    Olofsson, Göran
    Stockholm University, Faculty of Science, Department of Astronomy.
    Posch, T.
    Regibo, S.
    Savini, G.
    Sibthorpe, B.
    Swinyard, B. M.
    Yates, J. A.
    Waelkens, C.
    Warm water vapour in the sooty outflow from a luminous carbon star2010In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 467, no 7311, p. 64-67Article in journal (Refereed)
    Abstract [en]

    The detection(1) of circumstellar water vapour around the ageing carbon star IRC + 10216 challenged the current understanding of chemistry in old stars, because water was predicted(2) to be almost absent in carbon-rich stars. Several explanations for the water were postulated, including the vaporization of icy bodies (comets or dwarf planets) in orbit around the star(1), grain surface reactions(3), and photochemistry in the outer circumstellar envelope(4). With a single water line detected so far from this one carbon-rich evolved star, it is difficult to discriminate between the different mechanisms proposed. Here we report the detection of dozens of water vapour lines in the far-infrared and sub-millimetre spectrum of IRC + 10216 using the Herschel satellite(5). This includes some high-excitation lines with energies corresponding to similar to 1,000 K, which can be explained only if water is present in the warm inner sooty region of the envelope. A plausible explanation for the warm water appears to be the penetration of ultraviolet photons deep into a clumpy circumstellar envelope. This mechanism also triggers the formation of other molecules, such as ammonia, whose observed abundances(6) are much higher than hitherto predicted(7).

  • 45. Edgar, Graham J.
    et al.
    Stuart-Smith, Rick D.
    Willis, Trevor J.
    Kininmonth, Stuart
    Stockholm University, Faculty of Science, Stockholm Resilience Centre. University of Tasmania, Australia.
    Baker, Susan C.
    Banks, Stuart
    Barrett, Neville S.
    Becerro, Mikel A.
    Bernard, Anthony T. F.
    Berkhout, Just
    Buxton, Colin D.
    Campbell, Stuart J.
    Cooper, Antonia T.
    Davey, Marlene
    Edgar, Sophie C.
    Foersterra, Guenter
    Galvan, David E.
    Irigoyen, Alejo J.
    Kushner, David J.
    Moura, Rodrigo
    Parnell, P. Ed
    Shears, Nick T.
    Soler, German
    Strain, Elisabeth M. A.
    Thomson, Russell J.
    Global conservation outcomes depend on marine protected areas with five key features2014In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 506, no 7487, p. 216-+Article in journal (Refereed)
    Abstract [en]

    In line with global targets agreed under the Convention on Biological Diversity, the number of marine protected areas (MPAs) is increasing rapidly, yet socio-economic benefits generated by MPAs remain difficult to predict and under debate(1,2). MPAs often fail to reach their full potential as a consequence of factors such as illegal harvesting, regulations that legally allow detrimental harvesting, or emigration of animals outside boundaries because of continuous habitat or inadequate size of reserve(3-5). Here we show that the conservation benefits of 87 MPAs investigated worldwide increase exponentially with the accumulation of five key features: no take, well enforced, old (>10 years), large (>100 km(2)), and isolated by deep water or sand. Using effective MPAs with four or five key features as an unfished standard, comparisons of underwater survey data from effective MPAs with predictions based on survey data from fished coasts indicate that total fish biomass has declined about two-thirds from historical baselines as a result of fishing. Effective MPAs also had twice as many large (>250 mm total length) fish species per transect, five times more large fish biomass, and fourteen times more shark biomass than fished areas. Most (59%) of the MPAs studied had only one or two key features and were not ecologically distinguishable from fished sites. Our results show that global conservation targets based on area alone will not optimize protection of marine biodiversity. More emphasis is needed on better MPA design, durable management and compliance to ensure that MPAs achieve their desired conservation value.

  • 46. El Albani, Abderrazak
    et al.
    Bengtson, Stefan
    Canfield, Donald E.
    Bekker, Andrey
    Macchiarelli, Roberto
    Mazurier, Arnaud
    Hammarlund, Emma U.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Boulvais, Philippe
    Dupuy, Jean-Jacques
    Fontaine, Claude
    Fuersich, Franz T.
    Gauthier-Lafaye, Francois
    Janvier, Philippe
    Javaux, Emmanuelle
    Ossa, Frantz Ossa
    Pierson-Wickmann, Anne-Catherine
    Riboulleau, Armelle
    Sardini, Paul
    Vachard, Daniel
    Whitehouse, Martin
    Meunier, Alain
    Large colonial organisms with coordinated growth in oxygenated environments 2.1 Gyr ago2010In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 466, no 7302, p. 100-104Article in journal (Refereed)
    Abstract [en]

    The evidence for macroscopic life during the Palaeoproterozoic era (2.5-1.6 Gyr ago) is controversial(1-5). Except for the nearly 2-Gyr-old coil-shaped fossil Grypania spiralis(6,7), which may have been eukaryotic, evidence for morphological and taxonomic bio-diversification of macroorganisms only occurs towards the beginning of the Mesoproterozoic era (1.6-1.0 Gyr)(8). Here we report the discovery of centimetre-sized structures from the 2.1-Gyr-old black shales of the Palaeoproterozoic Francevillian B Formation in Gabon, which we interpret as highly organized and spatially discrete populations of colonial organisms. The structures are up to 12 cm in size and have characteristic shapes, with a simple but distinct ground pattern of flexible sheets and, usually, a permeating radial fabric. Geochemical analyses suggest that the sediments were deposited under an oxygenated water column. Carbon and sulphur isotopic data indicate that the structures were distinct biogenic objects, fossilized by pyritization early in the formation of the rock. The growth patterns deduced from the fossil morphologies suggest that the organisms showed cell-to-cell signalling and coordinated responses, as is commonly associated with multicellular organization(9). The Gabon fossils, occurring after the 2.45-2.32-Gyr increase in atmospheric oxygen concentration(10), may be seen as ancient representatives of multicellular life, which expanded so rapidly 1.5 Gyr later, in the Cambrian explosion.

  • 47.
    Elmgren, Ragnar
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Political backing to save the Baltic sea2012In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 487, no 7408, p. 432-432Article in journal (Other academic)
  • 48.
    Elmqvist, Thomas
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Sustainability and resilience differ2017In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 546, no 7658, p. 352-352Article in journal (Other academic)
  • 49.
    Emerson, B. C.
    et al.
    University of East Anglia, UK.
    Kolm, Niclas
    University of East Anglia, UK; University of Edinburgh, UK.
    Ecology: Is speciation driven by species diversity? Reply.2005In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 438, no 7064, p. E2-Article in journal (Refereed)
  • 50.
    Emerson, B. C.
    et al.
    University of East Anglia, UK.
    Kolm, Niclas
    University of East Anglia, UK; University of Edinburgh, UK.
    Species diversity can drive speciation2005In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 434, no 7036, p. 1015-1017Article in journal (Refereed)
    Abstract [en]

    A fundamental question in evolutionary ecology and conservation biology is: why do some areas contain greater species diversity than others? Island biogeographic theory has identified the roles of immigration and extinction in relation to area size and proximity to source areas(1,2), and the role of speciation is also recognized as an important factor(3-6). However, one as yet unexplored possibility is that species diversity itself might help to promote speciation, and indeed the central tenets of island biogeographic theory support such a prediction. Here we use data for plants and arthropods of the volcanic archipelagos of the Canary and Hawaiian Islands to address whether there is a positive relationship between species diversity and rate of diversification. Our index of diversification for each island is the proportion of species that are endemic, and we test our prediction that this increases with increasing species number. We show that even after controlling for several important physical features of islands, diversification is strongly related to species number.

1234 1 - 50 of 162
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