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7 results on '"K. Wiik"'

1. Multifrequency interferometer and radio continuum monitoring observations of CTA 102

Author

E. Valtaoja, K. Wiik, Lars B. Bååth, Fredrik T. Rantakyrö, and Merja Tornikoski

Subjects
Physics, Brightness, Spectral index, Proper motion, CTA102, Astronomy and Astrophysics, Astrophysics, CTA-102, Shock waves, Wavelength, Interferometry, Amplitude, Astronomi, astrofysik och kosmologi, Space and Planetary Science, Jets, Radiation mechanisms, Astronomy, Astrophysics and Cosmology, Quasars, Order of magnitude
Abstract

This paper represents the work of several years of observation of CTA 102 with both single dish telescopes and interferometric arrays, covering wavelengths from 1.2 cm to 1.3 mm. The resolution of the maps covers an order of magnitude from 0.5 mas to 50 μas. The images presented demonstrate the rapid structural changes in this source. These rapid structural changes correlates with the outbursts seen in the total flux, turnover frequency and in the spectral index. We have calculated the Brightness Temperatures of the components (TB ) directly from the determined component sizes and also using the logarithmic variability amplitudes and timescales to calculate the TB s. Both the methods yielded measurements of source frame T Bs no higher than ∼a few × 10 12 K. We find that the observed average proper motion is 0.4 0.07 mas/yr, which corresponds to an apparent transverse velocity of 11 ± 2 c. Copyright © 2003 EDP Sciences. This material is posted here with permission of EDP Sciences. Such permission of EDP Sciences does not in any way imply EDP Sciences endorsement of any of the University of Halmstads's products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from EDP Sciences. By choosing to view this document, you agree to all provisions of the copyright laws protecting it.

Published
2003
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2. 147 GHz VLBI observations: Detection of 3C 273 and 3C 279 on the 3100 km baseline Metsähovi – Pico Veleta

Author

Thomas P. Krichbaum, S. Urpo, S. Navarro, D. A. Graham, P. Könönen, J. A. Zensus, K. Wiik, Albert Greve, J. Peltonen, John Conway, Michael Grewing, P. Sjöman, Roy Booth, Ari Mujunen, Jouko Ritakari, M. Berton, F. Rantakyro, D. John, and E. Oinaskallio

Subjects
Physics, Space and Planetary Science, Baseline (sea), Brightness temperature, Very-long-baseline interferometry, Flux, Astronomy, Astronomy and Astrophysics, Astrophysics, Lower limit
Abstract

We report a successful VLBI observation at 147 GHz (2.1 mm) on the 3 100 km long baseline between the telescopes at Metsahovi (Finland) and Pico Veleta (Spain). The sources 3C 273B and 3C 279 were detected with a SNR of∼10. For these sources we estimate that 25-30% of the total flux is detectable as correlated flux on the 3 100 km baseline, which gives at 147 GHz a lower limit of the brightness temperature of the inner VLBI jet region of ∼1×10 1 0 K.

Published
2002
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3. Millimetre Continuum Variations, VLBI Structure and Gamma-rays: Investigating Shocked Jet Physics

Author

E. Valtaoja, Tuomas Savolainen, K. Wiik, and Anne Lähteenmäki

Subjects
Astroparticle physics, Physics, Active galactic nucleus, Astrophysics::High Energy Astrophysical Phenomena, Astronomy, Flux, Astronomy and Astrophysics, Cosmic ray, Quasar, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, law.invention, Space and Planetary Science, law, Very-long-baseline interferometry, Blazar, Astrophysics::Galaxy Astrophysics, Flare
Abstract

We compare the total flux density variations and the VLBI structural variations in a sample of 27 gamma-ray blazars. We find that all the radio variations are due to shocks; the flux of the underlying jet remains constant. A large fraction of the shocks grow and fade within the innermost 0.1 mas, appearing only as ‘core flares’. Comparisons with the EGRET data show that gamma-ray flares must come from the shocks, not from the jet. At the time of an EGRET flare, the shock is typically already over a parsec downstream from the radio core, beyond the accretion disk and/or the broad line region (BLR) photon fields. Thus, present models for gamma-ray production are inadequate, since they typically model the gamma-ray inverse Compton flux as coming from the jet, with significant disk or BLR external Compton components.

Published
2002
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4. The geometry of the universe from high resolution VLBI data of AGN shocks

Author

E. Valtaoja and K. Wiik

Subjects
Travel time, Physics, Space and Planetary Science, Astrophysics::High Energy Astrophysical Phenomena, Monitoring data, Very-long-baseline interferometry, High resolution, Astronomy and Astrophysics, Small sample, Geometry, Astrophysics, Omega
Abstract

VSOPシンポジウム(2000年1月19日-21日. 宇宙科学研究所(ISAS)）, 相模原市, 神奈川県, VSOP Symposium (January 19-21, 2000. Institute of Space and Astronautical Science(ISAS)), Sagamihara, Kanagawa Japan, 資料番号: SA6000155050

Published
2001
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5. Total Flux Density Variations in Extragalactic Radio Sources. II. Determining the Limiting Brightness Temperature for Synchrotron Sources

Author

E. Valtaoja, K. Wiik, and Anne Lähteenmäki

Subjects
Physics, Brightness, Astrophysics::High Energy Astrophysical Phenomena, Inverse, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Synchrotron, law.invention, symbols.namesake, Intrinsic brightness, Space and Planetary Science, law, Brightness temperature, Very-long-baseline interferometry, symbols, Doppler effect, Equipartition theorem
Abstract

The maximum intrinsic brightness temperature Tb, lim for powerful synchrotron-emitting radio sources is usually assumed to be ≈1012 K, limited by the inverse Compton catastrophe. A lower value of ≈5×1010 K, based on the equipartition brightness temperature, has been suggested by Readhead on the basis of Tb, obs distributions derived from VLBI observations. We present two new methods for estimating Tb, lim in extragalactic radio sources by using total flux density variations. A reasonable estimate of the value of Tb, lim for a source can be obtained by comparing the Doppler boosting factors derived from total flux density variations at 22 and 37 GHz with traditional estimates based on the radio and synchrotron self-Compton (SSC) X-ray fluxes. Another independent estimate of Tb, lim is obtained by comparing the brightness temperatures derived from variability data with the values calculated from VLBI observations. Using several data sets, we find that both methods yield a value of ≤1011 K, in accordance with the equipartition brightness temperature limit proposed by Readhead.

Published
1999
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6. Multifrequency VLBA study of the blazar S5 0716+714 during the active state in 2004 II. Large-scale jet kinematics and the comparison of the different methods of VLBI data imaging as applied to kinematic studies of AGN

Author

Yliya N. Vetukhnovskaya, Leo O. Takalo, Elizaveta A. Rastorgueva, A. T. Bajkova, K. Wiik, Esko Valtaoja, and Mehreen Mahmud

Subjects
Physics, Jet (fluid), Brightness, Line-of-sight, Cosmology and Nongalactic Astrophysics (astro-ph.CO), Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astronomy and Astrophysics, Kinematics, Astrophysics, Space and Planetary Science, Very-long-baseline interferometry, Deconvolution, Blazar, Astrophysics::Galaxy Astrophysics, Astrophysics - Cosmology and Nongalactic Astrophysics, Data reduction
Abstract

We study the jet kinematics of the blazar S5 0716+714 during its active state in 2003-2004 with multi-epoch VLBI observations. Aims. We present a kinematic analysis of the large-scale (0-12 mas) jet of 0716+714, based on the results of six epochs of VLBA monitoring at 5 GHz. Additionally, we compare kinematic results obtained with two imaging methods based on different deconvolution algorithms. The blazar 0716+714 has a diffuse large-scale jet and a very faint bright compact core. Experiments with simulated data showed that the conventional data reduction procedure based on the CLEAN deconvolution algorithm does not perform well in restoring this type of structure. This might be the reason why previous kinematic studies of this source yielded ambiguous results. In order to obtain accurate kinematics of this source, we independently applied two imaging techniques to the raw data: the conventional method, based on difference mapping, which uses CLEAN deconvolution, and the generalized maximum entropy method (GMEM) realized in the VLBImager package developed at the Pulkovo Observatory in Russia. The results of both methods give us a consistent kinematic scenario: the large-scale jet of 0716+714 is diffuse and stationary. Differences between the inner (0-1 mas) and outer (1-12 mas) regions of the jet in brightness and velocity of the components could be explained by the bending of the jet, which causes the angle between the jet direction and the line of sight to change from ~5 deg to ~11 deg. For the source 0716+714 both methods worked at the limit of their capability., Comment: 13 pages, 7 figures. Accepted for publication in A&A, 2011

Published
2011
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7. Isotopic Composition of Light Nuclei in Cosmic Rays: Results from AMS-01

Author

H. T. Liu, J. Ulbricht, P. Extermann, H. Hofer, G. Ambrosi, U. Becker, E. Perrin, C. Sbarra, W. J. Burger, F. J. Eppling, P. H. Fisher, S. M. Ting, M. Kraeber, Rui Miguel Faisca Rodrigues Pereira, Veronica Bindi, T. Kirn, M. Paniccia, C. dela Guia, A. Klimentov, Adrian Biland, M.W. Lee, M. Pimenta, Jouko Ritakari, Hui Zhang, S. Schael, I. D'Antone, D. Rapin, Sadakazu Haino, J. Casaus, Massimo Gervasi, Jungwook Shin, V. Plyaskin, P. Azzarello, F. Mayet, A. Schultz von Dratzig, D. Grandi, Andrea Contin, J.V. Allaby, L. Djambazov, Andrei Kounine, P. G. Rancoita, M. Pohl, B. Bertucci, Xiao-Dong Tang, J. P. Vialle, W.Z. Zhu, M. Capell, R. Siedling, Shih-Chang Lee, H. Park, L. Ao, J. Engelberg, M. Jongmanns, R. Kossakowski, H. von Gunten, D. Crespo, J. D. Burger, K. Lübelsmeyer, J. Alcaraz, K. Karlamaa, Yun-Young Choi, S. X. Wu, Eun-Suk Seo, T. S. Dai, S. Xu, Dawei Zhao, Federico Cindolo, Z.R. Dong, V. Shoutko, Joachim Trümper, Maria Ionica, Guohuai Zhu, V. Commichau, Z.P. Zhang, E. Shoumilov, E. Riihonen, A. Mihul, G.P. Barreira, M. J. Boschini, M. Ribordy, Tengfei Song, H. Anderhub, M. Duranti, U. Roeser, T. Siedenburg, H.F. Chen, M. Steuer, C. Delgado, Mao-Zhi Yang, Zhenghao Xu, A. Lebedev, Dong-Chul Son, H. Suter, G.S. Sun, A. Bartoloni, V. Koutsenko, Eino Valtonen, W. Wallraff, P.C. Xia, F. Spada, P. Saouter, J. Favier, Z. L. Ren, Waclaw Karpinski, X. D. Cai, Changgen Yang, I. Vetlitsky, W.H. Park, E. Cortina-Gil, G. Bruni, F. Palmonari, A. Pevsner, D. Vité, M. Buénerd, Tzihong Chiueh, S. R. Ro, S. Natale, G. Laurenti, S. Waldmeier Wicki, E. P. Velikhov, B. Zimmermann, R. Becker, Y. Galaktionov, Roald Z. Sagdeev, Ciaran Williams, Merja Tornikoski, J.L. Yan, Markus Cristinziani, J. J. Torsti, Antonino Zichichi, L. Bellagamba, K.S. Kim, A. Arefiev, F. Barao, R. R. McNeil, Jing Wang, G. Sartorelli, Nicola Tomassetti, P. Cannarsa, Y. H. Chang, T. Eronen, G. Kenney, M. Aguilar, Felicitas Pauss, V. Hermel, Werner Lustermann, Behcet Alpat, M. Basile, Z.G. Chen, G. Flügge, G. N. Kim, F. Spinella, M. Bourquin, H. L. Zhuang, J. Yang, You Zhou, Nicolas Produit, D. Luckey, F. Vezzu, G. Lu, C. Maña, C.H. Lin, Samuel C.C. Ting, Fabrizio Giulio Luca Pilo, G. Castellini, J. Vandenhirtz, D. Casadei, G. Laborie, P. Giusti, S. Di Falco, O. Grimm, Paolo Zuccon, A. Hasan, Mauro Menichelli, F. Giovacchini, G. Schwering, Daijin Kim, W.Q. Gu, F. Zhou, N. Fouque, I. Cernuda, E. Fiandrini, H. S. Chen, D. Santos, S. Urpo, G. Viertel, Luísa Arruda, G. Lamanna, K. Hangarter, Lucio Quadrani, B. Verlaat, P. Berges, Ari Mujunen, K. Wiik, J. Berdugo, G. Boella, N.A. Chernoplekov, Anselmo Margotti, W. Hungerford, Timo Laitinen, M. Pauluzzi, D. Ren, Giuseppe Levi, Lu Yuzhang, LinLi Yan, A.I. Oliva, V. Pojidaev, C. Lechanoine-Leluc, S.W. Ye, Roberto Battiston, Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Institut Polytechnique de Grenoble - Grenoble Institute of Technology-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Annecy de Physique des Particules (LAPP), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), AMS, AGUILAR M., ALCARAZ J., ALLABY J., ALPAT B., AMBROSI G., ANDERHUB H., AO L., AREFIEV A., ARRUDA L., AZZARELLO P., BASILE M., BARAO F., BARREIRA G., BARTOLONI A., BATTISTON R., BECKER R., BECKER U., BELLAGAMBA L., BERDUGO J., BERGES P., BERTUCCI B., BILAND A., BINDI V., BOELLA G., BOSCHINI M., BOURQUIN M., BRUNI G., BUENERD M., BURGER JD., BURGER WJ., CAI XD., CANNARSA P., CAPELL M., CASADEI D., CASAUS J., CASTELLINI G., CERNUDA I., CHANG YH., CHEN HF., CHEN HS., CHEN ZG., CHERNOPLEKOV NA., CHIUEH TH., CHOI YY., CINDOLO F., COMMICHAU V., CONTIN A., CORTINA-GIL E., CRESPO D., CRISTINZIANI M., DAI TS., DELA GUIA C., DELGADO C., DI FALCO S., DJAMBAZOV L., D'ANTONE I., DONG ZR., DURANTI M., ENGELBERG J., EPPLING FJ., ERONEN T., EXTERMANN P., FAVIER J., FIANDRINI E., FISHER PH., FLUGGE G., FOUQUE N., GALAKTIONOV Y., GERVASI M., GIOVACCHINI F., GIUSTI P., GRANDI D., GRIMM O., GU WQ., HAINO S., HANGARTER K., HASAN A., HERMEL V., HOFER H., HUNGERFORD W., IONICA M., JONGMANNS M., KARLAMAA K., KARPINSKI W., KENNEY G., KIM DH., KIM GN., KIM KS., KIRN T., KLIMENTOV A., KOSSAKOWSKI R., KOUNINE A., KOUTSENKO V., KRAEBER M., LABORIE G., LAITINEN T., LAMANNA G., LAURENTI G., LEBEDEV A., LECHANOINE-LELUC C., LEE MW., LEE SC., LEVI G., LIN CH., LIU HT., LU G., LU YS., LUBELSMEYER K., LUCKEY D., LUSTERMANN W., MANA C., MARGOTTI A., MAYET F., MCNEIL RR., MENICHELLI M., MIHUL A., MUJUNEN A., NATALE S., OLIVA A., PALMONARI F., PANICCIA M., PARK HB., PARK WH., PAULUZZI M., PAUSS F., PEREIRA R., PERRIN E., PEVSNER A., PILO F., PIMENTA M., PLYASKIN V., POJIDAEV V., POHL M., PRODUIT N., QUADRANI L., RANCOITA PG., RAPIN D., REN D., REN Z., RIBORDY M., RIIHONEN E., RITAKARI J., RO S., ROESER U., SAGDEEV R., SANTOS D., SARTORELLI G., SAOUTER P., SBARRA C., SCHAEL S., VON DRATZIG AS., SCHWERING G., SEO ES., SHIN JW., SHOUMILOV E., SHOUTKO V., SIEDENBURG T., SIEDLING R., SON D., SONG T., SPADA FR., SPINELLA F., STEUER M., SUN GS., SUTER H., TANG XW., TING SCC., TING SM., TOMASSETTI N., TORNIKOSKI M., TORSTI J., TRUMPER J., ULBRICHT J., URPO S., VALTONEN E., VANDENHIRTZ J., VELIKHOV E., VERLAAT B., VETLITSKY I., VEZZU F., VIALLE JP., VIERTEL G., VITE D., VON GUNTEN H., WICKI SW., WALLRAFF W., WANG JZ., WIIK K., WILLIAMS C., WU SX., XIA PC., XU S., XU ZZ., YAN JL., YAN LG., YANG CG., YANG J., YANG M., YE SW., ZHANG HY., ZHANG ZP., ZHAO DX., ZHOU F., ZHOU Y., ZHU GY., ZHU WZ., ZHUANG HL., ZICHICHI A., ZIMMERMANN B., ZUCCON P, Aguilar, M, Alcaraz, J, Allaby, J, Alpat, B, Ambrosi, G, Anderhub, H, Ao, L, Arefiev, A, Arruda, L, Azzarello, P, Basile, M, Barao, F, Barreira, G, Bartoloni, A, Battiston, R, Becker, R, Becker, U, Bellagamba, L, Berdugo, J, Berges, P, Bertucci, B, Biland, A, Bindi, V, Boella, G, Boschini, M, Bourquin, M, Bruni, G, Buénerd, M, Burger, J, Burger, W, Cai, X, Cannarsa, P, Capell, M, Casadei, D, Casaus, J, Castellini, G, Cernuda, I, Chang, Y, Chen, H, Chen, Z, Chernoplekov, N, Chiueh, T, Choi, Y, Cindolo, F, Commichau, V, Contin, A, Cortina Gil, E, Crespo, D, Cristinziani, M, Dai, T, dela Guia, C, Delgado, C, Di Falco, S, Djambazov, L, D’Antone, I, Dong, Z, Duranti, M, Engelberg, J, Eppling, F, Eronen, T, Extermann, P, Favier, J, Fiandrini, E, Fisher, P, Flügge, G, Fouque, N, Galaktionov, Y, Gervasi, M, Giovacchini, F, Giusti, P, Grandi, D, Grimm, O, Gu, W, Haino, S, Hangarter, K, Hasan, A, Hermel, V, Hofer, H, Hungerford, W, Ionica, M, Jongmanns, M, Karlamaa, K, Karpinski, W, Kenney, G, Kim, D, Kim, G, Kim, K, Kirn, T, Klimentov, A, Kossakowski, R, Kounine, A, Koutsenko, V, Kraeber, M, Laborie, G, Laitinen, T, Lamanna, G, Laurenti, G, Lebedev, A, Lechanoine Leluc, C, Lee, M, Lee, S, Levi, G, Lin, C, Liu, H, Lu, G, Lu, Y, Lübelsmeyer, K, Luckey, D, Lustermann, W, Maña, C, Margotti, A, Mayet, F, Mcneil, R, Menichelli, M, Mihul, A, Mujunen, A, Natale, S, Oliva, A, Palmonari, F, Paniccia, M, Park, H, Park, W, Pauluzzi, M, Pauss, F, Pereira, R, Perrin, E, Pevsner, A, Pilo, F, Pimenta, M, Plyaskin, V, Pojidaev, V, Pohl, M, Produit, N, Quadrani, L, Rancoita, P, Rapin, D, Ren, D, Ren, Z, Ribordy, M, Riihonen, E, Ritakari, J, Ro, S, Roeser, U, Sagdeev, R, Santos, D, Sartorelli, G, Saouter, P, Sbarra, C, Schael, S, von Dratzig, A, Schwering, G, Seo, E, Shin, J, Shoumilov, E, Shoutko, V, Siedenburg, T, Siedling, R, Son, D, Song, T, Spada, F, Spinella, F, Steuer, M, Sun, G, Suter, H, Tang, X, Ting, S, Tomassetti, N, Tornikoski, M, Torsti, J, Trümper, J, Ulbricht, J, Urpo, S, Valtonen, E, Vandenhirtz, J, Velikhov, E, Verlaat, B, Vetlitsky, I, Vezzu, F, Vialle, J, Viertel, G, Vité, D, Von Gunten, H, Wicki, S, Wallraff, W, Wang, J, Wiik, K, Williams, C, Wu, S, Xia, P, Xu, S, Xu, Z, Yan, J, Yan, L, Yang, C, Yang, J, Yang, M, Ye, S, Zhang, H, Zhang, Z, Zhao, D, Zhou, F, Zhou, Y, Zhu, G, Zhu, W, Zhuang, H, Zichichi, A, Zimmermann, B, Zuccon, P, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Laboratory for Nuclear Science, Becker, R., Becker, Ulrich J., Berges, P., Burger, Joseph D., Cai, Xudong, Capell, Michael H., Dai, T. S., Eppling, Frederic J., Fisher, Peter H., Klimentov, A., Kounine, Andrei, Koutsenko, Vladimir, Lebedev, Alexei, Luckey, P. David, Jr., Shoutko, V., Siedenburg, T., Steuer, M., Ting, Samuel C. C., Wu. S. X., Xu, S., and Zhou, F.

Subjects
Nuclear reaction, Astrophysics and Astronomy, [PHYS.ASTR.HE]Physics [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE], genetic structures, Cosmic ray, Isotopes of boron, 01 natural sciences, High Energy Physics - Experiment, Nuclear physics, ACCELERATION OF PARTICLES, ABUNDANCES, Nucleosynthesis, 0103 physical sciences, Alpha Magnetic Spectrometer, [PHYS.HEXP]Physics [physics]/High Energy Physics - Experiment [hep-ex], acceleration of particles, cosmic rays, nuclear reactions, nucleosynthesis, abundances, 010303 astronomy & astrophysics, Cosmic ray spallation, Physics, NUCLEAR REACTIONS, NUCLEOSYNTHESIS, 010308 nuclear & particles physics, [SDU.ASTR.HE]Sciences of the Universe [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE], Astronomy and Astrophysics, COSMIC RAYS, FIS/01 - FISICA SPERIMENTALE, Space and Planetary Science, Isotopes of beryllium, Astrophysics - High Energy Astrophysical Phenomena, Heliosphere
Abstract

The variety of isotopes in cosmic rays allows us to study different aspects of the processes that cosmic rays undergo between the time they are produced and the time of their arrival in the heliosphere. In this paper, we present measurements of the isotopic ratios [superscript 2]H/[superscript 4]He, [superscript 3]He/[superscript 4]He, [superscript 6]Li/[superscript 7]Li, [superscript 7]Be/([superscript 9]Be+[superscript 10]Be), and [superscript 10]B/[superscript 11]B in the range 0.2-1.4 GeV of kinetic energy per nucleon. The measurements are based on the data collected by the Alpha Magnetic Spectrometer, AMS-01, during the STS-91 flight in 1998 June., United States. Dept. of Energy, Massachusetts Institute of Technology

Published
2011
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