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  • 1.
    Abbas, Ghazanfar
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Raza, Rizwan
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Chaudhry, M. Ashraf
    Zhu, Bin
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Preparation and Characterization of Nanocomposite Calcium Doped Ceria Electrolyte With Alkali Carbonates (NK-CDC) for SOFC2011Ingår i: Journal of Fuel Cell Science and Technology, ISSN 1550-624X, Vol. 8, nr 4, s. 041013-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The entire world's challenge is to find out the renewable energy sources due to rapid depletion of fossil fuels because of their high consumption. Solid oxide fuel cells (SOFCs) are believed to be the best alternative source, which converts chemical energy into electricity without combustion. Nanostructure study is required to develop highly ionic conductive electrolytes for SOFCs. In this work, the calcium doped ceria (Ce0.8Ca0.2O1.9) coated with 20% molar ratio of two alkali carbonates (CDC-M: MCO3, where M = Na and K) electrolyte was prepared by coprecipitation method. Ni based electrode was used to fabricate the cell by dry pressing technique. The crystal structure and surface morphology were characterized by an X-ray diffractometer, scanning electron microscopy (SEM), and high resolution transmission electron microscopy (TEM). The particle size was calculated in the range 10-20 nm by Scherer's formula and compared with SEM and TEM results. The ionic conductivity was measured by using ac electrochemical impedance spectroscopy method. The activation energy was also evaluated. The performance of the cell was measured 0.567 W/cm(2) at temperature 550 degrees C with hydrogen as a fuel.

  • 2.
    Abbas, Ghazanfar
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi. COMSATS Institute of Information Technology, Pakistan.
    Raza, Rizwan
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi. COMSATS Institute of Information Technology, Pakistan.
    Khan, M. Ajmal
    Ahmad, Imran
    Chaudhry, M. Ashraf
    Sherazi, Tauqir A.
    Mohsin, Munazza
    Ahmad, Mukhtar
    Zhu, Bin
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Synthesize and characterization of nanocomposite anodes for low temperature solid oxide fuel cell2015Ingår i: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 40, nr 1, s. 891-897Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Solid oxide fuel cells have much capability to become an economical alternative energy conversion technology having appropriate materials that can be operated at comparatively low temperature in the range of 400-600 degrees C. The nano-scale engineering has been incorporated to improve the catalytic activity of anode materials for solid oxide fuel cells. Nanostructured Al0.10NixZn0.90-xO oxides were prepared by solid state reaction, which were then mixed with the prepared Gadolinium doped Ceria GDC electrolyte. The crystal structure and surface morphology were characterized by XRD and SEM. The particle size was evaluated by XRD data and found in the range of 20-50 nm, which was then ensured by SEM pictures. The pellets of 13 mm diameter were pressed by dry press technique and electrical conductivities (DC and AC) were determined by four probe techniques and the values have been found to be 10.84 and 4.88 S/cm, respectively at hydrogen atmosphere in the temperature range of 300-600 degrees C. The Electrochemical Impedance Spectroscopy (EIS) analysis exhibits the pure electronic behavior at hydrogen atmosphere. The maximum power density of ANZ-GDC composite anode based solid oxide fuel cell has been achieved 705 mW/cm(2) at 550 degrees C.

  • 3.
    Abtahi, Farhad
    et al.
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinska sensorer, signaler och system.
    Lu, Ke
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinska sensorer, signaler och system.
    Dizon, M
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinska sensorer, signaler och system.
    Johansson, M
    KTH-School of Technology and Health.
    Seoane, Fernando
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinska sensorer, signaler och system. Högskolan i Borås.
    Lindecrantz, Kaj
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Data- och elektroteknik. Högskolan i Borås, Akademin för vård, arbetsliv och välfärd.
    Evaluating Atrial Fibrillation Detection Algorithm based on Heart Rate Variability analysis2015Ingår i: Medicinteknikdagarna, Uppsala: Svensk förening för medicinsk teknik och fysik , 2015Konferensbidrag (Refereegranskat)
  • 4.
    Abtahi, Farhad
    et al.
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinska sensorer, signaler och system.
    Lu, Ke
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinska sensorer, signaler och system.
    Guangchao, Li
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinska sensorer, signaler och system.
    Rödby, Kristian
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    Seoane, Fernando
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinska sensorer, signaler och system. Högskolan i Borås.
    A Knitted Garment using Intarsia Technique for Heart Rate Variability Biofeedback: Evaluation of Initial Prototype.2015Konferensbidrag (Övrigt vetenskapligt)
  • 5. Acero, F.
    et al.
    Larsson, Stefan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Li, L.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zimmer, S.
    et al.,
    DEVELOPMENT of the MODEL of GALACTIC INTERSTELLAR EMISSION for STANDARD POINT-SOURCE ANALYSIS of FERMI LARGE AREA TELESCOPE DATA2016Ingår i: Astrophysical Journal Supplement Series, ISSN 0067-0049, E-ISSN 1538-4365, Vol. 223, nr 2, artikel-id 26Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Most of the celestial γ rays detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope originate from the interstellar medium when energetic cosmic rays interact with interstellar nucleons and photons. Conventional point-source and extended-source studies rely on the modeling of this diffuse emission for accurate characterization. Here, we describe the development of the Galactic Interstellar Emission Model (GIEM), which is the standard adopted by the LAT Collaboration and is publicly available. This model is based on a linear combination of maps for interstellar gas column density in Galactocentric annuli and for the inverse-Compton emission produced in the Galaxy. In the GIEM, we also include large-scale structures like Loop I and the Fermi bubbles. The measured gas emissivity spectra confirm that the cosmic-ray proton density decreases with Galactocentric distance beyond 5 kpc from the Galactic Center. The measurements also suggest a softening of the proton spectrum with Galactocentric distance. We observe that the Fermi bubbles have boundaries with a shape similar to a catenary at latitudes below 20°and we observe an enhanced emission toward their base extending in the north and south Galactic directions and located within ∼4°of the Galactic Center.

  • 6. Acero, F.
    et al.
    Larsson, Stefan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. AlbaNova, Oskar Klein Ctr Cosmoparticle Phys, Sweden.
    Li, L.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. AlbaNova, Oskar Klein Ctr Cosmoparticle Phys, Sweden.
    Zimmer, S.
    et al.,
    The first fermi lat supernova remnant catalog2016Ingår i: Astrophysical Journal Supplement Series, ISSN 0067-0049, E-ISSN 1538-4365, Vol. 224, nr 1, artikel-id 8Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To uniformly determine the properties of supernova remnants (SNRs) at high energies, we have developed the first systematic survey at energies from 1 to 100 GeV using data from the Fermi Large Area Telescope (LAT). Based on the spatial overlap of sources detected at GeV energies with SNRs known from radio surveys, we classify 30 sources as likely GeV SNRs. We also report 14 marginal associations and 245 flux upper limits. A mock catalog in which the positions of known remnants are scrambled in Galactic longitude allows us to determine an upper limit of 22% on the number of GeV candidates falsely identified as SNRs. We have also developed a method to estimate spectral and spatial systematic errors arising from the diffuse interstellar emission model, a key component of all Galactic Fermi LAT analyses. By studying remnants uniformly in aggregate, we measure the GeV properties common to these objects and provide a crucial context for the detailed modeling of individual SNRs. Combining our GeV results with multiwavelength (MW) data, including radio, X-ray, and TeV, we demonstrate the need for improvements to previously sufficient, simple models describing the GeV and radio emission from these objects. We model the GeV and MW emission from SNRs in aggregate to constrain their maximal contribution to observed Galactic cosmic rays.

  • 7. Ackermann, M.
    et al.
    Ajello, M.
    Albert, A.
    Anderson, B.
    Atwood, W. B.
    Baldini, L.
    Barbiellini, G.
    Bastieri, D.
    Bellazzini, R.
    Bissaldi, E.
    Blandford, R. D.
    Bloom, E. D.
    Bonino, R.
    Bottacini, E.
    Brandt, T. J.
    Bregeon, J.
    Bruel, P.
    Buehler, R.
    Buson, S.
    Caliandro, G. A.
    Cameron, R. A.
    Caputo, R.
    Caragiulo, M.
    Caraveo, P. A.
    Cecchi, C.
    Charles, E.
    Chekhtman, A.
    Chiang, J.
    Chiaro, G.
    Ciprini, S.
    Claus, R.
    Cohen-Tanugi, J.
    Conrad, J.
    Cuoco, A.
    Cutini, S.
    D'Ammando, F.
    de Angelis, A.
    de Palma, F.
    Desiante, R.
    Digel, S. W.
    Di Venere, L.
    Drell, P. S.
    Drlica-Wagner, A.
    Favuzzi, C.
    Fegan, S. J.
    Franckowiak, A.
    Fukazawa, Y.
    Funk, S.
    Fusco, P.
    Gargano, F.
    Gasparrini, D.
    Giglietto, N.
    Giordano, F.
    Giroletti, M.
    Godfrey, G.
    Gomez-Vargas, G. A.
    Grenier, I. A.
    Grove, J. E.
    Guiriec, S.
    Gustafsson, M.
    Hewitt, J. W.
    Hill, A. B.
    Horan, D.
    Johannesson, G.
    Johnson, R. P.
    Kuss, M.
    Larsson, S.
    Latronico, L.
    Li, J.
    Li, L.
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Longo, F.
    Loparco, F.
    Lovellette, M. N.
    Lubrano, P.
    Malyshev, D.
    Mayer, M.
    Mazziotta, M. N.
    McEnery, J. E.
    Michelson, P. F.
    Mizuno, T.
    Moiseev, A. A.
    Monzani, M. E.
    Morselli, A.
    Murgia, S.
    Nuss, E.
    Ohsugi, T.
    Orienti, M.
    Orlando, E.
    Ormes, J. F.
    Paneque, D.
    Pesce-Rollins, M.
    Piron, F.
    Pivato, G.
    Raino, S.
    Rando, R.
    Razzano, M.
    Reimer, A.
    Reposeur, T.
    Ritz, S.
    Sanchez-Conde, M.
    Schulz, A.
    Sgro, C.
    Siskind, E. J.
    Spada, F.
    Spandre, G.
    Spinelli, P.
    Tajima, H.
    Takahashi, H.
    Thayer, J. B.
    Tibaldo, L.
    Torres, D. F.
    Tosti, G.
    Troja, E.
    Vianello, G.
    Werner, M.
    Winer, B. L.
    Wood, K. S.
    Wood, M.
    Zaharijas, G.
    Zimmer, S.
    Updated search for spectral lines from Galactic dark matter interactions with pass 8 data from the Fermi Large Area Telescope2015Ingår i: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 91, nr 12, artikel-id 122002Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Dark matter in the Milky Way may annihilate directly into. rays, producing a monoenergetic spectral line. Therefore, detecting such a signature would be strong evidence for dark matter annihilation or decay. We search for spectral lines in the Fermi Large Area Telescope observations of the Milky Way halo in the energy range 200 MeV-500 GeV using analysis methods from our most recent line searches. The main improvements relative to previous works are our use of 5.8 years of data reprocessed with the Pass 8 event-level analysis and the additional data resulting from the modified observing strategy designed to increase exposure of the Galactic center region. We search in five sky regions selected to optimize sensitivity to different theoretically motivated dark matter scenarios and find no significant detections. In addition to presenting the results from our search for lines, we also investigate the previously reported tentative detection of a line at 133 GeV using the new Pass 8 data.

  • 8. Ackermann, M.
    et al.
    Ajello, M.
    Albert, A.
    Atwood, W. B.
    Baldini, L.
    Barbiellini, G.
    Bastieri, D.
    Bellazzini, R.
    Bissaldi, E.
    Blandford, R. D.
    Bonino, R.
    Bottacini, E.
    Bregeon, J.
    Bruel, P.
    Buehler, R.
    Caliandro, G. A.
    Cameron, R. A.
    Caragiulo, M.
    Caraveo, P. A.
    Cavazzuti, E.
    Cecchi, C.
    Chekhtman, A.
    Chiang, J.
    Chiaro, G.
    Ciprini, S.
    Claus, R.
    Cohen-Tanugi, J.
    Costanza, F.
    Cuoco, A.
    Cutini, S.
    D'Ammando, F.
    de Angelis, A.
    de Palma, F.
    Desiante, R.
    Digel, S. W.
    Di Venere, L.
    Drell, P. S.
    Favuzzi, C.
    Fegan, S. J.
    Focke, W. B.
    Franckowiak, A.
    Funk, S.
    Fusco, P.
    Gargano, F.
    Gasparrini, D.
    Giglietto, N.
    Giordano, F.
    Giroletti, M.
    Glanzman, T.
    Godfrey, G.
    Grenier, I. A.
    Grove, J. E.
    Guiriec, S.
    Harding, A. K.
    Hewitt, J. W.
    Horan, D.
    Hou, X.
    Iafrate, G.
    Johannesson, G.
    Kamae, T.
    Kuss, M.
    Larsson, S.
    Latronico, L.
    Li, J.
    Li, L.
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Longo, F.
    Loparco, F.
    Lovellette, M. N.
    Lubrano, P.
    Magill, J.
    Maldera, S.
    Manfreda, A.
    Mayer, M.
    Mazziotta, M. N.
    Michelson, P. F.
    Mitthumsiri, W.
    Mizuno, T.
    Monzani, M. E.
    Morselli, A.
    Murgia, S.
    Nuss, E.
    Omodei, N.
    Orlando, E.
    Ormes, J. F.
    Paneque, D.
    Perkins, J. S.
    Pesce-Rollins, M.
    Petrosian, V.
    Piron, F.
    Pivato, G.
    Raino, S.
    Rando, R.
    Razzano, M.
    Reimer, A.
    Reimer, O.
    Reposeur, T.
    Sgro, C.
    Siskind, E. J.
    Spada, F.
    Spandre, G.
    Spinelli, P.
    Takahashi, H.
    Thayer, J. B.
    Thompson, D. J.
    Tibaldo, L.
    Torres, D. F.
    Tosti, G.
    Troja, E.
    Vianello, G.
    Winer, B. L.
    Wood, K. S.
    Yassine, M.
    Measurement of the high-energy gamma-ray emission from the Moon with the Fermi Large Area Telescope2016Ingår i: PHYSICAL REVIEW D, ISSN 2470-0010, Vol. 93, nr 8, artikel-id 082001Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have measured the gamma-ray emission spectrum of the Moon using the data collected by the Large Area Telescope onboard the Fermi satellite during its first seven years of operation, in the energy range from 30 MeV up to a few GeV. We have also studied the time evolution of the flux, finding a correlation with the solar activity. We have developed a full Monte Carlo simulation describing the interactions of cosmic rays with the lunar surface. The results of the present analysis can be explained in the framework of this model, where the production of gamma rays is due to the interactions of cosmic-ray proton and helium nuclei with the surface of the Moon. Finally, we have used our simulation to derive the cosmic-ray proton and helium spectra near Earth from the Moon gamma-ray data.

  • 9. Ackermann, M.
    et al.
    Ajello, M.
    Atwood, W. B.
    Baldini, L.
    Ballet, J.
    Barbiellini, G.
    Bastieri, D.
    Gonzalez, J. Becerra
    Bellazzini, R.
    Bialdi, E.
    Blandford, R. D.
    Bloom, E. D.
    Bnino, R.
    Bottagini, E.
    Brandt, T. J.
    Bregeon, J.
    Britto, R. J.
    Bruel, P.
    Buehler, R.
    Buson, S.
    Caliandro, G. A.
    Cameron, R. A.
    Caragiulo, M.
    Caraveo, P. A.
    Careenter, B.
    Casandjian, J. M.
    Cavazzuti, E.
    Cecchi, C.
    Charles, E.
    Chekhtman, A.
    Cheung, C. C.
    Chiang, J.
    Chiaro, G.
    Ciprini, S.
    Claus, R.
    Cohen-Tanugi, J.
    Cominsky, L. R.
    Conrad, J.
    Cutini, S.
    D'Abrusco, R.
    D'Ammando, F.
    de Angelis, A.
    Desiante, R.
    Digel, S. W.
    Di Venere, L.
    Drell, P. S.
    FAvuzzi, C.
    Fegan, S. J.
    Ferrara, E. C.
    Finke, J.
    Focke, W. B.
    Franckowiak, A.
    Fuhrmann, L.
    Fukazawa, Y.
    Furniss, A. K.
    Fusco, P.
    Gargano, E.
    Gasparrini, D.
    Giglietto, N.
    Giommi, P.
    Giordano, E.
    Giroletti, M.
    Glanzman, T.
    Godfrey, G.
    Grenier, I. A.
    Grove, J. E.
    Guiriec, S.
    Hewitt, J. W.
    Hill, A. B.
    Horan, D.
    Itoh, R.
    Johannesson, G.
    Johnson, A. S.
    Johnson, W. N.
    Kataoka, J.
    Kawano, T.
    Krauss, F.
    Kuss, M.
    La Mura, G.
    Larsson, S.
    Latronico, L.
    Leto, C.
    Li, J.
    Li, Liang
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. Oskar Klein Centre for Cosmoparticle Physics, Sweden.
    Longo, F.
    Loparco, F.
    Lott, B.
    Lovellette, M. N.
    Lubrano, P.
    Madejski, G. M.
    Mayer, M.
    Mazziotta, M. N.
    McEnery, J. E.
    Michelson, P. F.
    Mizuno, T.
    Moiseev, A. A.
    Monzani, M. E.
    Morselli, A.
    Moskalenko, I. V.
    Murgia, S.
    Nuss, E.
    Ohno, M.
    Oxsugi, T.
    Ojha, R.
    Omdei, N.
    Orienti, M.
    Orlando, E.
    Paggi, A.
    Paneque, D.
    Perkins, J. S.
    Pesce-Rollins, M.
    Piron, F.
    Pivato, G.
    Porter, T. A.
    Raino, S.
    Rando, R.
    Razzano, M.
    Razzaque, S.
    Reimer, A.
    Reimer, O.
    Romani, R. W.
    Salvetti, D.
    Schaal, M.
    Schinzel, F. K.
    Schulz, A.
    Sgro, C.
    Siskind, E. J.
    Sokolovsky, K. V.
    Spada, F.
    Spandre, G.
    Spinelli, P.
    Stawarz, L.
    Suson, D. J.
    Takahashi, H.
    Takahashi, T.
    Tanaka, Y.
    Thayer, J. G.
    Thayer, J. B.
    Tibaldo, L.
    Torres, D. F.
    Torresi, E.
    Tosti, G.
    Troja, E.
    Uchiyama, Y.
    Vianello, G.
    Winer, B. L.
    Wood, K. S.
    Zimmer, S.
    THE THIRD CATALOG OF ACTIVE GALACTIC NUCLEI DETECTED BY THE FERMI LARGE AREA TELESCOPE2015Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 810, nr 1, artikel-id 14Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The third catalog of active galactic nuclei (AGNs) detected by the Fermi-LAT (3LAC) is presented. It is based on the third Fermi-LAT catalog (3FGL) of sources detected between 100 MeV and 300 GeV with a Test Statistic greater than 25, between 2008 August 4 and 2012 July 31. The 3LAC includes 1591 AGNs located at high Galactic latitudes (vertical bar b vertical bar > 10 degrees), a 71% increase over the second catalog based on 2 years of data. There are 28 duplicate associations, thus 1563 of the 2192 high-latitude gamma-ray sources of the 3FGL catalog are AGNs. Most of them (98%) are blazars. About half of the newly detected blazars are of unknown type, i.e., they lack spectroscopic information of sufficient quality to determine the strength of their emission lines. Based on their gamma-ray spectral properties, these sources are evenly split between flat-spectrum radio quasars (FSRQs) and BL Lacs. The most abundant detected BL Lacs are of the high-synchrotron-peaked (HSP) type. About 50% of the BL Lacs have no measured redshifts. A few new rare outliers (HSP-FSRQs and high-luminosity HSP BL Lacs) are reported. The general properties of the 3LAC sample confirm previous findings from earlier catalogs. The fraction of 3LAC blazars in the total population of blazars listed in BZCAT remains non-negligible even at the faint ends of the BZCAT-blazar radio, optical, and X-ray flux distributions, which hints that even the faintest known blazars could eventually shine in gamma-rays at LAT-detection levels. The energy-flux distributions of the different blazar populations are in good agreement with extrapolation from earlier catalogs.

  • 10. Ackermann, M.
    et al.
    Albert, A.
    Atwood, W. B.
    Baldini, L.
    Ballet, J.
    Barbiellini, G.
    Bastieri, D.
    Bellazzini, R.
    Bissaldi, E.
    Bloom, E. D.
    Bonino, R.
    Brandt, T. J.
    Bregeon, J.
    Bruel, P.
    Buehler, R.
    Caliandro, G. A.
    Cameron, R. A.
    Caragiulo, M.
    Caraveo, P. A.
    Cavazzuti, E.
    Cecchi, C.
    Charles, E.
    Chekhtman, A.
    Chiang, J.
    Chiaro, G.
    Ciprini, S.
    Cohen-Tanugi, J.
    Cutini, S.
    D'Ammando, F.
    de Angelis, A.
    de Palma, F.
    Desiante, R.
    Digel, S. W.
    Drell, P. S.
    Favuzzi, C.
    Ferrara, E. C.
    Focke, W. B.
    Franckowiak, A.
    Fusco, P.
    Gargano, F.
    Gasparrini, D.
    Giglietto, N.
    Giordano, F.
    Godfrey, G.
    Grenier, I. A.
    Grondin, M. -H
    Guillemot, L.
    Guiriec, S.
    Harding, A. K.
    Hill, A. B.
    Horan, D.
    Johannesson, G.
    Knoedlseder, J.
    Kuss, M.
    Larsson, Stefan
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik. Oskar Klein Centre for Cosmoparticle Physics, Alba Nova, Sweden.
    Latronico, L.
    Li, J.
    Li, Liang
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik. Oskar Klein Centre for Cosmoparticle Physics, Alba Nova, Sweden.
    Longo, F.
    Loparco, F.
    Lubrano, P.
    Maldera, S.
    Martin, P.
    Mayer, M.
    Mazziotta, M. N.
    Michelson, P. F.
    Mizuno, T.
    Monzani, M. E.
    Morselli, A.
    Murgia, S.
    Nuss, E.
    Ohsugi, T.
    Orienti, M.
    Orlando, E.
    Ormes, J. F.
    Paneque, D.
    Pesce-Rollins, M.
    Piron, F.
    Pivato, G.
    Porter, T. A.
    Raino, S.
    Rando, R.
    Razzano, M.
    Reimer, A.
    Reimer, O.
    Romani, R. W.
    Sanchez-Conde, M.
    Schulz, A.
    Sgro, C.
    Siskind, E. J.
    Smith, D. A.
    Spada, F.
    Spandre, G.
    Spinelli, P.
    Suson, D. J.
    Takahashi, H.
    Thayer, J. B.
    Tibaldo, L.
    Torres, D. F.
    Tosti, G.
    Troja, E.
    Vianello, G.
    Wood, M.
    Zimmer, S.
    Deep view of the Large Magellanic Cloud with six years of Fermi-LAT observations2016Ingår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 586, artikel-id A71Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Context. The nearby Large Magellanic Cloud (LMC) provides a rare opportunity of a spatially resolved view of an external star-forming galaxy in gamma-rays. The LMC was detected at 0.1-100 GeV as an extended source with CGRO/EGRET and using early observations with the Fermi-LAT. The emission was found to correlate with massive star-forming regions and to be particularly bright towards 30 Doradus. Aims. Studies of the origin and transport of cosmic rays (CRs) in the Milky Way are frequently hampered by line-of-sight confusion and poor distance determination. The LMC offers a complementary way to address these questions by revealing whether and how the gamma-ray emission is connected to specific objects, populations of objects, and structures in the galaxy. Methods. We revisited the gamma-ray emission from the LMC using about 73 months of Fermi-LAT P7REP data in the 0.2-100 GeV range. We developed a complete spatial and spectral model of the LMC emission, for which we tested several approaches: a simple geometrical description, template-fitting, and a physically driven model for CR-induced interstellar emission. Results. In addition to identifying PSR J0540-6919 through its pulsations, we find two hard sources positionally coincident with plerion N 157B and supernova remnant N 132D, which were also detected at TeV energies with H.E.S.S. We detect an additional soft source that is currently unidentified. Extended emission dominates the total flux from the LMC. It consists of an extended component of about the size of the galaxy and additional emission from three to four regions with degree-scale sizes. If it is interpreted as CRs interacting with interstellar gas, the large-scale emission implies a large-scale population of similar to 1-100 GeV CRs with a density of similar to 30% of the local Galactic value. On top of that, the three to four small-scale emission regions would correspond to enhancements of the CR density by factors 2 to 6 or higher, possibly more energetic and younger populations of CRs compared to the large-scale population. An alternative explanation is that this is emission from an unresolved population of at least two dozen objects, such as pulsars and their nebulae or supernova remnants. This small-scale extended emission has a spatial distribution that does not clearly correlate with known components of the LMC, except for a possible relation to cavities and supergiant shells. Conclusions. The Fermi-LAT GeV observations allowed us to detect individual sources in the LMC. Three of the newly discovered sources are associated with rare and extreme objects. The 30 Doradus region is prominent in GeV gamma-rays because PSR J0540-6919 and N 157B are strong emitters. The extended emission from the galaxy has an unexpected spatial distribution, and observations at higher energies and in radio may help to clarify its origin.

  • 11. Ackermann, M.
    et al.
    Arcavi, I.
    Baldini, L.
    Ballet, J.
    Barbiellini, G.
    Bastieri, D.
    Bellazzini, R.
    Bissaldi, E.
    Blandford, R. D.
    Bonino, R.
    Bottacini, E.
    Brandt, T. J.
    Bregeon, J.
    Bruel, P.
    Buehler, R.
    Buson, S.
    Caliandro, G. A.
    Cameron, R. A.
    Caragiulo, M.
    Caraveo, P. A.
    Cavazzuti, E.
    Cecchi, C.
    Charles, E.
    Chekhtman, A.
    Chiang, J.
    Chiaro, G.
    Ciprini, S.
    Claus, R.
    Cohen-Tanugi, J.
    Cutini, S.
    D'Ammando, F.
    de Angelis, A.
    de Palma, F.
    Desiante, R.
    Di Venere, L.
    Drell, P. S.
    Favuzzi, C.
    Fegan, S. J.
    Franckowiak, A.
    Funk, S.
    Fusco, P.
    Gal-Yam, A.
    Gargano, F.
    Gasparrini, D.
    Giglietto, N.
    Giordano, F.
    Giroletti, M.
    Glanzman, T.
    Godfrey, G.
    Grenier, I. A.
    Grove, J. E.
    Guiriec, S.
    Harding, A. K.
    Hayashi, K.
    Hewitt, J. W.
    Hill, A. B.
    Horan, D.
    Jogler, T.
    Johannesson, G.
    Kocevski, D.
    Kuss, M.
    Larsson, S.
    Lashner, J.
    Latronico, L.
    Li, J.
    Li, Liang
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. Oskar Klein Centre for Cosmoparticle Physics, Sweden.
    Longo, F.
    Loparco, F.
    Lovellette, M. N.
    Lubrano, P.
    Malyshev, D.
    Mayer, M.
    Mazziotta, M. N.
    McEnery, J. E.
    Michelson, P. F.
    Mizuno, T.
    Monzani, M. E.
    Morselli, A.
    Murase, K.
    Nugent, P.
    Nuss, E.
    Ofek, E.
    Ohsugi, T.
    Orienti, M.
    Orlando, E.
    Ormes, J. F.
    Paneque, D.
    Pesce-Rollins, M.
    Piron, F.
    Pivato, G.
    Raino, S.
    Rando, R.
    Razzano, M.
    Reimer, A.
    Reimer, O.
    Schulz, A.
    Sgro, C.
    Siskind, E. J.
    Spada, F.
    Spandre, G.
    Spinelli, P.
    Suson, D. J.
    Takahashi, H.
    Thayer, J. B.
    Tibaldo, L.
    Torres, D. F.
    Troja, E.
    Vianello, G.
    Werner, M.
    Wood, K. S.
    Wood, M.
    SEARCH FOR EARLY GAMMA-RAY PRODUCTION IN SUPERNOVAE LOCATED IN A DENSE CIRCUMSTELLAR MEDIUM WITH THE FERMI LAT2015Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 807, nr 2, artikel-id 169Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Supernovae (SNe) exploding in a dense circumstellar medium (CSM) are hypothesized to accelerate cosmic rays in collisionless shocks and emit GeV gamma-rays and TeV neutrinos on a timescale of several months. We perform the first systematic search for gamma-ray emission in Fermi Large Area Telescope data in the energy range from 100 MeV to 300 GeV from the ensemble of 147 SNe Type IIn exploding in a dense CSM. We search for a gamma-ray excess at each SNe location in a one-year time window. In order to enhance a possible weak signal, we simultaneously study the closest and optically brightest sources of our sample in a joint-likelihood analysis in three different time windows (1 year, 6 months, and 3 months). For the most promising source of the sample, SN 2010jl (PTF 10aaxf), we repeat the analysis with an extended time window lasting 4.5 years. We do not find a significant excess in gamma-rays for any individual source nor for the combined sources and provide model-independent flux upper limits for both cases. In addition, we derive limits on the gamma-ray luminosity and the ratio of gamma-ray-to-optical luminosity ratio as a function of the index of the proton injection spectrum assuming a generic gamma-ray production model. Furthermore, we present detailed flux predictions based on multi-wavelength observations and the corresponding flux upper limit at a 95% confidence level (CL) for the source SN 2010jl (PTF 10aaxf).

  • 12. Ackermann, M
    et al.
    Larsson, Stefan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. AlbaNova, Sweden.
    Li, L.
    KTH, Skolan för teknikvetenskap (SCI), Fysik. AlbaNova, Sweden.
    Rephaeli, Y.
    et al.,
    SEARCH FOR GAMMA-RAY EMISSION FROM THE COMA CLUSTER WITH SIX YEARS OF FERMI-LAT DATA2016Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 819, nr 2, artikel-id 149Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present results from gamma-ray observations of the Coma cluster incorporating six years of Fermi-LAT data and the newly released "Pass 8" event-level analysis. Our analysis of the region reveals low-significance residual structures within the virial radius of the cluster that are too faint for a detailed investigation with the current data. Using a likelihood approach that is free of assumptions on the spectral shape we derive upper limits on the gamma-ray flux that is expected from energetic particle interactions in the cluster. We also consider a benchmark spatial and spectral template motivated by models in which the observed radio halo is mostly emission by secondary electrons. In this case, the median expected and observed upper limits for the flux above 100MeV are 1.7 x 10(-9) ph cm(-2) s(-1) and 5.2 x 10(-9) ph cm(-2) s(-1) respectively (the latter corresponds to residual emission at the level of 1.8 sigma). These bounds are comparable to or higher than predicted levels of hadronic gamma-ray emission in cosmic-ray (CR) models with or without reacceleration of secondary electrons, although direct comparisons are sensitive to assumptions regarding the origin and propagation mode of CRs and magnetic field properties. The minimal expected.-ray flux from radio and star-forming galaxies within the Coma cluster is roughly an order of magnitude below the median sensitivity of our analysis.

  • 13. Ackermann, M.
    et al.
    Larsson, Stefan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. Oskar Klein Centre for Cosmoparticle Physics, Sweden.
    Li, L.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. Oskar Klein Centre for Cosmoparticle Physics, Sweden.
    Zimmer, S.
    et al.,
    Resolving the extragalactic γ-ray background above 50 GeV with the fermi large area telescope2016Ingår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 116, nr 15, artikel-id 151105Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Fermi Large Area Telescope (LAT) Collaboration has recently released a catalog of 360 sources detected above 50 GeV (2FHL). This catalog was obtained using 80 months of data re-processed with Pass 8, the newest event-level analysis, which significantly improves the acceptance and angular resolution of the instrument. Most of the 2FHL sources at high Galactic latitude are blazars. Using detailed Monte Carlo simulations, we measure, for the first time, the source count distribution, dN/dS, of extragalactic γ-ray sources at E>50 GeV and find that it is compatible with a Euclidean distribution down to the lowest measured source flux in the 2FHL (∼8×10-12 ph cm-2 s-1). We employ a one-point photon fluctuation analysis to constrain the behavior of dN/dS below the source detection threshold. Overall, the source count distribution is constrained over three decades in flux and found compatible with a broken power law with a break flux, Sb, in the range [8×10-12,1.5×10-11] ph cm-2 s-1 and power-law indices below and above the break of α2[1.60,1.75] and α1=2.49±0.12, respectively. Integration of dN/dS shows that point sources account for at least 86-14+16% of the total extragalactic γ-ray background. The simple form of the derived source count distribution is consistent with a single population (i.e., blazars) dominating the source counts to the minimum flux explored by this analysis. We estimate the density of sources detectable in blind surveys that will be performed in the coming years by the Cherenkov Telescope Array.

  • 14. Ackermann, M
    et al.
    Larsson, Stefan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Li, L.
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Zimmer, S.
    et al.,
    Searching for Dark Matter Annihilation from Milky Way Dwarf Spheroidal Galaxies with Six Years of Fermi Large Area Telescope Data2015Ingår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 115, nr 23, artikel-id 231301Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The dwarf spheroidal satellite galaxies (dSphs) of the Milky Way are some of the most dark matter (DM) dominated objects known. We report on gamma-ray observations of Milky Way dSphs based on six years of Fermi Large Area Telescope data processed with the new PASS8 event-level analysis. None of the dSphs are significantly detected in gamma rays, and we present upper limits on the DM annihilation cross section from a combined analysis of 15 dSphs. These constraints are among the strongest and most robust to date and lie below the canonical thermal relic cross section for DM of mass less than or similar to 100 GeV annihilating via quark and tau-lepton channels.

  • 15.
    Adamopoulos, Othon
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Björkman, Eva
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Zhang, Yu
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Bog, Tassilo
    Mussmann, Lothar
    Lox, Egbert
    A nanophase oxygen storage material: Alumina-coated metal-based ceria2009Ingår i: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 29, nr 4, s. 677-689Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nanoparticles of Ce1-xMxO2-delta (M = Ca or Zr) coated with Al2O3 with average crystallite size of 10 nm have been synthesised via solution chemistry approach under controlled chemical and hydrodynamic conditions. Their synthesis has been accomplished in three major steps: (1) simultaneous co-precipitation of cations, (2) sequential precipitation of Al(OH)(3) over the former particles and (3) calcination of the precipitated precursors to the corresponding oxides. Several compositions have been synthesised and their physicochemical properties are compared with commercial state-of-the-art material. The Al2O3-coating hinders the particles growth at high temperatures, resulting in materials with a large specific surface area and a restrain in the decrease of their oxygen storage capacity.

  • 16. Ajello, M.
    et al.
    Albert, A.
    Atwood, W. B.
    Barbiellini, G.
    Bastieri, D.
    Bechtol, K.
    Bellazzini, R.
    Bissaldi, E.
    Blandford, R. D.
    Bloom, E. D.
    Bonino, R.
    Bottacini, E.
    Brandt, T. J.
    Bregeon, J.
    Bruel, P.
    Buehler, R.
    Buson, S.
    Caliandro, G. A.
    Cameron, R. A.
    Caputo, R.
    Caragiulo, M.
    Carave, P. A.
    Cecchi, C.
    Chekhtman, A.
    Chiang, J.
    Chiaro, G.
    Ciprini, S.
    Cohen-Tanugi, J.
    Cominsky, L. R.
    Conrad, J.
    Cutini, S.
    D'Ammando, F.
    de Angelis, A.
    de Palma, F.
    Desiante, R.
    Di Venere, L.
    Drell, P. S.
    Favuzzi, C.
    Ferrara, E. C.
    Fusco, P.
    Gargano, F.
    Gasparrini, D.
    Giglietto, N.
    Giommi, P.
    Giordano, F.
    Giroletti, M.
    Glanzman, T.
    Godfrey, G.
    Gomez-Vargas, G. A.
    Grenier, I. A.
    Guiriec, S.
    Gustafsson, M.
    Harding, A. K.
    Hewitt, J. W.
    Hill, A. B.
    Horan, D.
    Jogler, T.
    Johannesson, G.
    Johnson, A. S.
    Kamae, T.
    Karwin, C.
    Knoedlseder, J.
    Kuss, M.
    Larsson, Stefan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Latronico, L.
    Li, J.
    Li, L.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Longo, F.
    Loparco, F.
    Lovellette, M. N.
    Lubrano, P.
    Magill, J.
    Maldera, S.
    Malyshev, D.
    Manfreda, A.
    Mayer, M.
    Mazziotta, M. N.
    Michelson, P. F.
    Mitthumsiri, W.
    Mizuno, T.
    Moiseev, A. A.
    Monzani, M. E.
    Morselli, A.
    Moskalenko, I. V.
    Murgia, S.
    Nuss, E.
    Ohno, M.
    Ohsugi, T.
    Omodei, N.
    Orlando, E.
    Ormes, J. F.
    Paneque, D.
    Pesce-Rollins, M.
    Piron, F.
    Pivato, G.
    Porter, T. A.
    Raino, S.
    Rando, R.
    Razzano, M.
    Reimer, A.
    Reimer, O.
    Ritz, S.
    Sanchez-Conde, M.
    Parkinson, P. M. Saz
    Sgro, C.
    Siskind, E. J.
    Smith, D. A.
    Spada, F.
    Spandre, G.
    Spinelli, P.
    Suson, D. J.
    Tajima, H.
    Takahashi, H.
    Thayer, J. B.
    Torres, D. F.
    Tosti, G.
    Troja, E.
    Uchiyama, Y.
    Vianello, G.
    Winer, B. L.
    Wood, K. S.
    Zaharijas, G.
    Zimmer, S.
    FERMI-LAT OBSERVATIONS OF HIGH-ENERGY gamma-RAY EMISSION TOWARD THE GALACTIC CENTER2016Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 819, nr 1, artikel-id 44Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Fermi Large Area Telescope (LAT) has provided the most detailed view to date of the emission toward the Galactic center (GC) in high-energy gamma-rays. This paper describes the analysis of data taken during the first 62 months of the mission in the energy range 1-100 GeV from a 15 degrees x 15 degrees region about the direction of the GC. Specialized interstellar emission models (IEMs) are constructed to enable the separation of the.-ray emissions produced by cosmic ray particles interacting with the interstellar gas and radiation fields in the Milky Way into that from the inner similar to 1 kpc surrounding the GC, and that from the rest of the Galaxy. A catalog of point sources for the 15 degrees x 15 degrees region is self-consistently constructed using these IEMs: the First Fermi-LAT Inner Galaxy Point Source Catalog (1FIG). The spatial locations, fluxes, and spectral properties of the 1FIG sources are presented, and compared with gamma-ray point sources over the same region taken from existing catalogs. After subtracting the interstellar emission and point-source contributions a residual is found. If templates that peak toward the GC are used to model the positive residual the agreement with the data improves, but none of the additional templates tried account for all of its spatial structure. The spectrum of the positive residual modeled with these templates has a strong dependence on the choice of IEM.

  • 17. Ajello, M
    et al.
    Larsson, Stefan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. AlbaNova, Sweden.
    Li, L.
    KTH, Skolan för teknikvetenskap (SCI), Fysik. AlbaNova, Sweden.
    Yassine, M.
    et al.,
    DEEP MORPHOLOGICAL AND SPECTRAL STUDY OF THE SNR RCW 86 WITH FERMI-LAT2016Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 819, nr 2, artikel-id 98Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    RCW 86 is a young supernova remnant (SNR) showing a shell-type structure at several wavelengths and is thought to be an efficient cosmic-ray (CR) accelerator. Earlier Fermi Large Area Telescope results reported the detection of.-ray emission coincident with the position of RCW 86 but its origin (leptonic or hadronic) remained unclear due to the poor statistics. Thanks to 6.5 years of data acquired by the Fermi-LAT and the new event reconstruction Pass 8, we report the significant detection of spatially extended emission coming from RCW 86. The spectrum is described by a power-law function with a very hard photon index (Gamma= 1.42 +/- 0.1(stat) +/- 0.06(syst)) in the 0.1-500 GeV range and an energy flux above 100 MeV of (2.91. 0.8(stat). 0.12(syst)) 10-11 erg cm(-2) s(-1). Gathering all the available multiwavelength (MWL) data, we perform a broadband modeling of the nonthermal emission of RCW 86 to constrain parameters of the nearby medium and bring new hints about the origin of the gamma-ray emission. For the whole SNR, the modeling favors a leptonic scenario in the framework of a two-zone model with an average magnetic field of 10.2 +/- 0.7 mu G and a limit on the maximum energy injected into protons of 2. x. 10(49) erg for a density of 1 cm(-3). In addition, parameter values are derived for the north-east and south-west (SW) regions of RCW 86, providing the first indication of a higher magnetic field in the SW region.

  • 18. Ajello, M.
    et al.
    Larsson, Stefan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. Oskar Klein Centre for Cosmoparticle Physics, Sweden.
    Li, L.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. Oskar Klein Centre for Cosmoparticle Physics, Sweden.
    Zimmer, S.
    et al.,
    Search for Spectral Irregularities due to Photon-Axionlike-Particle Oscillations with the Fermi Large Area Telescope2016Ingår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 116, nr 16, artikel-id 161101Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on the search for spectral irregularities induced by oscillations between photons and axionlike-particles (ALPs) in the γ-ray spectrum of NGC 1275, the central galaxy of the Perseus cluster. Using 6 years of Fermi Large Area Telescope data, we find no evidence for ALPs and exclude couplings above 5×10-12 GeV-1 for ALP masses 0.5ma5 neV at 95% confidence. The limits are competitive with the sensitivity of planned laboratory experiments, and, together with other bounds, strongly constrain the possibility that ALPs can reduce the γ-ray opacity of the Universe.

  • 19.
    Andersson, Annika
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Andersson, Margareta A.T.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär G
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    A study of some elemental distributions between slag and hot metal during tapping of the blast furnace2004Ingår i: Steel research, ISSN 0177-4832, Vol. 75, nr 5, s. 294-301Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper investigates the distribution of elements between slag and hot metal from a blast furnace through calculation of distribution coefficients from actual production data. First, samples of slag and hot metal tapped from a commercial blast furnace were taken continually at 10-minute intervals for a production period of 68 hours. Distribution coefficients of manganese, silicon, sulphur and vanadium were then calculated from the results of the sample analyses. A major conclusion drawn from examination of the results was that the behaviour of the studied elements was as could be expected when approaching the equilibrium reactions from thermodynamic theory. The distributions of the elements in the slag-metal system showed clear tendencies which did not appear to be influenced by the operational conditions of the furnace. For example, for manganese, vanadium and sulphur, it was found that a higher basicity led to a decreased distribution coefficient L-Mn and L-V, but an increased L-S, which is according to theory. Another observed relationship was that slag basicity increased with an increased carbon content in the hot metal, which indicated that SiO2 was reduced to [Si] when the oxygen potential decreased. Furthermore, it was found that sulphur and silica behaviour likened that of acidic slag components, while the manganese oxide and vanadium oxide behaviour was similar to that of basic slag components.

  • 20.
    Andersson, Birger
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Data- och systemvetenskap, DSV.
    Bergholtz, Maria
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Data- och systemvetenskap, DSV.
    Edirisuriya, Ananda
    Ilayperuma, Tharaka
    Johannesson, Paul
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Data- och systemvetenskap, DSV.
    A declarative foundation of process models2005Ingår i: ADVANCED INFORMATION SYSTEMS ENGINEERING, PROCEEDINGS / [ed] Pastor, O; Chunha, JFE, 2005, Vol. 3520, s. 233-247Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, a declarative foundation for process models is proposed. Three issues in process management and modeling are identified: business orientation, traceability, and flexibility. It is shown how these issues can be addressed by basing process models on business models, where a business model focuses on the transfer of value between agents. As a bridge between business models and process models, the notion of activity dependency model is introduced, which identifies, classifies, and relates activities needed for executing and coordinating value transfers.

  • 21.
    Andersson, Birger
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Data- och systemvetenskap, DSV.
    Bergholtz, Maria
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Data- och systemvetenskap, DSV.
    Edirisuriya, Ananda
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Data- och systemvetenskap, DSV.
    Ilayperuma, Tharaka
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Data- och systemvetenskap, DSV.
    Johannesson, Paul
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Data- och systemvetenskap, DSV.
    Gordijn, Jaap
    Gregoire, Bertrand
    Schmitt, Michael
    Dubois, Eric
    Abels, Sven
    Hahn, Axel
    Wangler, Benkt
    Weigand, Hans
    Towards a reference ontology for business models2006Ingår i: Conceptual Modeling - ER 2006, Proceedings / [ed] Embley, DW; Olive, A; Ram, S, 2006, Vol. 4215, s. 482-496Konferensbidrag (Refereegranskat)
    Abstract [en]

    Ontologies are viewed as increasingly important tools for structuring domains of interests. In this paper we propose a reference ontology of business models using concepts from three established business model ontologies; the REA, BMO, and e3-value. The basic concepts in the reference ontology concern actors, resources, and the transfer of resources between actors. Most of the concepts in the reference ontology are taken from one of the original ontologies, but we have also introduced a number of additional concepts, primarily related to resource transfers between business actors. The purpose of the proposed ontology is to increase the understanding of the original ontologies as well as the relationships between them, and also to seek opportunities to complement and improve on them.

  • 22.
    Andersson, Emma
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Sichen, Du
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    The Effect of CaF2 in the Slag in Ladle Refining2009Ingår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 80, nr 8, s. 544-551Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Industrial experiments were conducted in ladle treatment at SSAB Oxelosund aiming at a reduction and even elimination of CaF2 as a component in synthetic slag formers. The effects of the presence of CaF2 on sulphur refining, lining wear as well as types and amount of inclusions were examined. The results of the plant trials indicated that the new slag without CaF2 had enough capacity for sulphur removal. On the other hand, the presence of CaF2 as a flux in the slag resulted in profound lining wear. It was also found that both the number and the types of non-metallic inclusions were not affected by the elimination of CaF2 from synthetic slag. The origins of different types of inclusions were also analysed on the basis of the experimental results. The analysis supported the finding that the presence of CaF2 had little effect on inclusions.

  • 23.
    Andersson, Henrik
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transporter och samhällsekonomi.
    Perception of Own Death Risk: A Reassessment of Road-Traffic Mortality Risk2008Rapport (Övrigt vetenskapligt)
    Abstract [en]

    This study examines individuals' perception of their own road-mortality risk. Swedish data on respondents' subjective risk beliefs is used and compared with objective risk estimates. The objective risk is defined as the risk of the respondent's own age and gender group, and it is found that low and high risk groups over- and underassess their risk levels, respectively. This study replicates the analysis used by Andersson and Lundborg (2007) and the pattern of over- and underassessment found confirms their findings. As in their study, risk beliefs are updated in line with the Bayesian learning model, a relationship not statistically significant in this study, though. Regarding results of individual characteristics and risk beliefs in both studies, whereas, e.g., gender effects are robust, other results suggest a weak relationship between the perception of own road-mortality risk and individual characteristics.

  • 24.
    Andersson, Henrik
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transporter och samhällsekonomi.
    Private and Public WTP for Safety: A Validity Test2007Rapport (Övrigt vetenskapligt)
    Abstract [en]

    To elicit an affected population's preferences for, e.g., better health or environment stated preference (SP) methods are often used. SP methods are based on hypothetical market settings which necessitates validity tests of the results. This study describes a validity test on the basis of theoretical predictions and empirical findings for private and public safety measures. According to the test, public willingness to pay (WTP) should exceed private WTP.

  • 25.
    Andersson, J. Christer
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Jord- och bergmekanik.
    Rock Mass Response to Coupled Mechanical Thermal Loading: Äspö Pillar Stability Experiment, Sweden2007Doktorsavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    The geological disposal of nuclear waste, in underground openings and the long-term performance of these openings demand a detailed understanding of fundamental rock mechanics. A full scale field experiment: Äspö Pillar Stability Experiment was conducted at a depth of 450 m in sparsely fractured granitic rock to examine the rock mass response between two deposition holes. An oval shaped tunnel was excavated parallel to the σ3 direction to provide access to the experiment and also provide elevated stress magnitudes in the floor. In the tunnel floor two 1.75-m diameter 6-m deep boreholes were excavated so that a 1-m thick pillar was created between them. In one of the holes a confinement pressure of 700 kPa was applied and in the other displacement transducers were installed. The pillar volume was monitored by an Acoustic Emission System. Spatially distributed thermocouples were used to monitor the temperature development as the pillar was heated by electrical heaters. The excavation-induced stress together with the thermal-induced stress was sufficient to cause the wall of the open borehole to yield. The temperature-induced stress was increased slowly to enable detailed studies of the rock mass yielding process. Once the rock mass loading response was observed, the rock mass was unloaded using a de-stress slotting technique.

    This thesis focuses on the in-situ study of the rock mass response to coupled mechanical thermal loading and thermal-mechanical unloading. The experiment, its design, monitoring and observations are thoroughly described. An estimate of the yielding strength of the rock mass is presented and compared with laboratory test and results from other rock mass conditions reported elsewhere in the open literature. General conclusions about the effect of the confining pressure and the observations from the unloading of the pillar are also presented.

    Important findings are that the yielding strength of the rock mass has been successfully determined, low confinement pressures significantly affects the onset of yielding, the primary mode of fracture initiation and propagation is extensional, no significant time dependency of the yielding process was observed. The unloading studies also indicated that what appeared to be shear bands likely was a propagating zone of extensile failure that weakened the rock so that displacements in the shear direction could occur.

    Ladda ner fulltext (pdf)
    FULLTEXT01
  • 26. Andersson, J.
    et al.
    Raza, S.
    KTH.
    Eliasson, Anders
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Surreddi, K. B.
    Solidification of alloy 718, ati 718Plus® and waspaloy2014Ingår i: 8th International Symposium on Superalloy 718 and Derivatives 2014, 2014, s. 181-192Konferensbidrag (Refereegranskat)
    Abstract [en]

    Alloy 718, ATI 718Plus® and Waspaloy have been investigated in terms of what their respective solidification process reveals. Differential thermal analysis was used to approach the task together with secondary electron and back scattered electron detectors equipped with an energy dispersive X-ray spectroscopy detector. These experimental methods were used to construct pseudo binary phase diagrams that could aid in explaining solidification as well as liquation mechanisms in processes such as welding and casting. Furthermore, it was seen that Waspaloy has the smallest solidification range, followed by Alloy 718, and finally ATI 718Plus® possessing the largest solidification interval in comparison.

  • 27.
    Andersson, Johan
    et al.
    KTH, Tidigare Institutioner (före 2005), Kemi.
    Borg-Karlson, Anna-Karin
    KTH, Tidigare Institutioner (före 2005), Kemi.
    Wiklund, C.
    Sexual conflict and anti-aphrodisiac titre in a polyandrous butterfly: male ejaculate tailoring and absence of female control2004Ingår i: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 271, nr 1550, s. 1765-1770Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Males of the green-veined butterfly Pieris napi synthesize and transfer the volatile methyl salicylate (MeS) to females at mating, a substance that is emitted by non-virgin females when courted by males, curtailing courtship and decreasing the likelihood of female re-mating. The volatile is released when females display the 'mate-refusal' posture with spread wings and elevated abdomen, when courted by conspecific males. Here, we assess how the amount of MeS released by courted females changes over time since mating, and whether it is influenced by the frequency with which females display the mate-refusal posture. We also assess whether males tailor the anti-aphrodisiac content of ejaculates with respect to the expected degree of sperm competition, by comparing how males allocate MeS proportionately to first and second ejaculates in relation to ejaculate mass. The results show that females housed for 5 days in individual cages where they were able to fly and oviposit normally, released similar amounts of MeS. However, females housed together for the same period of time, causing them to frequently display the mate-refusal posture, released significantly lower levels of MeS than the individually housed females. This indicates that female display of the mate-refusal posture depletes their anti-aphrodisiac stores, and suggests that females are unable to voluntarily control their release of the anti-aphrodisiac. A comparison of relative proportion of MeS transferred by males in their first and second ejaculates showed that proportionately more MeS was allocated to the first ejaculate, in accordance with the idea that these are tailored to delay female re-mating.

  • 28.
    Andersson, Karl E.
    et al.
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Madejski, G M
    Complex structure of galaxy cluster A1689: Evidence for a merger from X-ray data?2004Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 607, nr 1, s. 190-201Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A1689 is a galaxy cluster at z = 0.183 for which previous measurements of its mass by using various techniques gave discrepant results. We present a new detailed measurement of the mass with the data based on X-ray observations with the European Photon Imaging Camera aboard the XMM-Newton Observatory, determined by using an unparameterized deprojection technique. Fitting the total mass profile to a Navarro-Frenk-White model yields halo concentration c = 7.2(-2.4)(+1.6) and r(200) = 1.13 +/- 0.21 h(-1) Mpc, corresponding to a mass that is less than half of that found from gravitational lensing. Adding to the evidence of substructure from optical observations, X-ray analysis shows a highly asymmetric temperature profile and a nonuniform redshift distribution, implying large-scale relative motion of the gas. A lower than expected gas mass fraction f(gas) = 0.072 +/- 0: 008 (for a flat LambdaCDM cosmology) suggests a complex spatial and/or dynamical structure. We also find no sign of any additional absorbing component previously reported on the basis of the Chandra data, confirming the XMM-Newton low-energy response by using data from ROSAT.

  • 29.
    Andersson, Lars
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.). Max Planck Institute for Gravitational Physics, United Kingdom.
    Blue, P.
    Hidden symmetries and decay for the wave equation on the Kerr spacetime2015Ingår i: Annals of Mathematics, ISSN 0003-486X, E-ISSN 1939-8980, Vol. 182, nr 3, s. 787-853Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Energy and decay estimates for the wave equation on the exterior region of slowly rotating Kerr spacetimes are proved. The method used is a generalisation of the vector-field method that allows the use of higher-order symmetry operators. In particular, our method makes use of the second-order Carter operator, which is a hidden symmetry in the sense that it does not correspond to a Killing symmetry of the spacetime.

  • 30.
    Andersson, Lars Erik
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.). Albert Einstein Institute, Germany.
    Bäckdahl, T.
    Blue, P.
    Decay of solutions to the Maxwell equation on the Schwarzschild background2016Ingår i: Classical and quantum gravity, ISSN 0264-9381, E-ISSN 1361-6382, Vol. 33, nr 8, artikel-id 085010Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new Morawetz or integrated local energy decay estimate for Maxwell test fields on the exterior of a Schwarzschild black hole spacetime is proved. The proof makes use of a new superenergy tensor Hab defined in terms of the Maxwell field and its first derivatives. The superenergy tensor, although not conserved, yields a conserved higher order energy current Hab (∂t)b. The tensor Hab vanishes for the static Coulomb field, and the Morawetz estimate proved here therefore yields integrated decay for the Maxwell field to the Coulomb solution on the Schwarzschild exterior.

  • 31.
    Andersson, Martin
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Centra, Centrum för studier inom vetenskap och innovation, CESIS.
    Grasjo, Urban
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Centra, Centrum för studier inom vetenskap och innovation, CESIS.
    Spatial dependence and the representation of space in empirical models2009Ingår i: The annals of regional science, ISSN 0570-1864, E-ISSN 1432-0592, Vol. 43, nr 1, s. 159-180Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A well-formed spatial model should most likely not produce spatial autocorrelation at all. From this perspective spatial autocorrelation is not (pure) statistical nuisance but a sign of that a model lacks a representation of an important economic phenomenon. In a Knowledge Production Function (KPF) context, this paper shows that a representation of space reflecting the potential of physical interaction between localities by means of accessibility variables on the "right-hand-side"aEuro"a simple alternative to spatial lag and spatial error which can be estimated by OLS-captures substantive spatial dependence. Results are verified with Monte Carlo simulations based on Anselin's (Int Reg Sci Rev 26(2):153-166, 2003) taxonomy of modelled and unmodelled effects. The analysis demonstrates that an accessibility representation of explanatory variables depict the network nature of spatial interaction, such that spatial dependence is actually modelled.

  • 32.
    Andersson, Martin
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Centra, Centrum för studier inom vetenskap och innovation, CESIS.
    Johansson, Börje
    KTH, Skolan för industriell teknik och management (ITM), Industriell ekonomi och organisation (Inst.), Samhällsekonomi. KTH, Skolan för industriell teknik och management (ITM), Centra, Centrum för studier inom vetenskap och innovation, CESIS.
    Heterogeneous Distributions of Firms Sustained by Innovation Dynamics-A Model with Empirical Illustrations and Analysis2012Ingår i: Journal of Industry, Competition and Trade, ISSN 1566-1679, E-ISSN 1573-7012, Vol. 12, nr 2, s. 239-263Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper develops a framework of innovation dynamics to appreciate observed heterogeneity of firm size distributions, in which dynamics refer to exit and entry of product varieties and variety markets of individual firms. The analysis is based on a model of variety-triplets where every such triplet in the economy is identified by a unique combination of a variety, destination and firm. New variety triplets are introduced by innovating firms in a quasi-temporal setting of monopolistic competition. Ideas for variety-triplets arrive to firms according to a firm-specific and state dependent Poisson process, whereas variety triplets exit according to a destination-specific Poisson process. The empirical analysis employs a detailed firm-level data base which provides information about all variety triplets. Firm size is measured by a firm's number of variety triplets. The empirical results are compatible with the model predictions of (i) a persistent distribution of firm sizes, (ii) frequent events of exit and entry, and (iii) state dependent entry, where a state may be given by each firm's composition of triplets and/or other firm attributes.

  • 33.
    Andersson, Rasmus
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Evaluation of two hydrocyclone designs for pulp fractionation2010Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The process conditions and fractionation efficiency of two hydrocyclone designs, a novel and a conventional conical design, were evaluated. The novel design comprised a modified inlet section, where the pulp suspension had to pass a narrow ring-shaped opening, and a very compact fractionation zone. The influence of feed concentration and fine fraction mass ratio was studied. The trials were performed with never-dried, unrefined bleached chemical softwood pulp. Fractionation efficiency was evaluated in terms of change of surface roughness of handsheets made out of the fractions and the feed pulp respectively.

    The fractionation efficiency increased considerably with decreasing fine fraction mass ratio, especially at higher feed concentrations. This finding prompted a hypothesis on the existence of a radial gradient in the composition of the suspension inside the novel hydrocyclone. Using the novel hydrocyclone in a feed-forward fractionation system would therefore prove to be more favourable as a larger total fine fraction of better properties can be obtained. A three-stage feed-forward fractionation system was evaluated in laboratory scale. Here, it was indeed possible to extract fine fractions with improved surface properties in each of the three consecutive stages. All three fine fractions had about the same surface roughness.

    The fractionation performance of the novel design was benchmarked against that of a conventional, best available technology (BAT) design. In terms of fractionation efficiency, the BAT design performed better. However, the fractions produced with the novel hydrocyclone had a much smaller difference in concentration, implying a much less pronounced enrichment of fines in the fine fraction. It is unclear, to what extent the lower share of latewood fibres and the increased fines content, respectively, contributed to the improved surface roughness of the fine fractions. However, it is clear that the lower enrichment of fines in the novel hydrocyclone makes it easier to install it in industrial applications without a need for auxiliary equipment to redistribute large water flows.

     

    Ladda ner fulltext (pdf)
    FULLTEXT02
  • 34.
    Andersson, Samir
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Zou, Dapeng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Zhang, Rong
    KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Sun, Shiguo
    KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Åkermark, Björn
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Selective Positioning of CB 8 on Two Linked Viologens and Electrochemically Driven Movement of the Host Molecule2009Ingår i: European Journal of Organic Chemistry, ISSN 1434-193X, E-ISSN 1099-0690, nr 8, s. 1163-1172Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The binding interactions between cucurbit[8]uril (CB[8]) and a dicationic guest N,N-dimethyl-3,3'-dimethyl-4,4'-bipyridinium (DMV2+) have been investigated by various experimental techniques including NMR, ESI-MS, and UV/Vis and fluorescence spectroscopy. In a three-component system consisting of CB[81, N,N-dimethyl-4,4'-bipyridinium (MV2+) and DMV2+, CB[8] was found to exhibit a higher binding affinity to DMV2+ than to MV2+, When DMV2+ was connected to MV2+ by an alkyl chain, the first equiv. of CB[8] could be selectively positioned on the DMV2+ moiety, and then a second equiv. of CB[8] was positioned on the MV2+ moiety. Spectroelectrochemical studies showed that upon the reduction of this system at -0.6 V vs. AgCl, the CB[8] could move from the DMV2+ moiety to the MV+center dot radical, which formed a dimer inside the CB[8] cavity. Molecular oxygen quenched the dimer, and the CB[8] moved back to the DMV2+ moiety, indicating it molecular movement driven by electrochemistry. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

  • 35. Andro, B.
    et al.
    Chaigne, S.
    Schmitt, T.
    Shah, Asif L.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Vibrationsövervakning. KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Simplified integral energy method: Application to pass by noise2006Ingår i: Int. Congr. Sound Vib., ICSV, 2006, s. 2919-2926Konferensbidrag (Refereegranskat)
    Abstract [en]

    The pass-by noise measurements defined in a standard procedure constitute a legal test for every new vehicle. Nowadays, the improvements of the engineering process allow automotive manufacturers to reduce the vehicle development cycles. Consequently, the acoustic optimization of the vehicle applied to reduction of the exterior noise needs to be considered as soon as possible to avoid repeated road tests depending strongly on the environmental conditions. At the early stage of the development process, Renault would like therefore to use an accurate tool which predicts the engine compartment contribution to pass-by noise. This model will give indications to answer technical issues like: The influence of acoustical materials or height of the vehicle on pass-by noise in the high frequency range. In medium and high frequency domains, classical numerical methods such as the Finite Element Method (FEM) or the Boundary Element Method (BEM) are not well suited to predict the engine contribution because of the prohibitive computation time and memory occupation. Some energy methods such as statistical energy Analysis (SEA) will only give global values in each substructure and are not suited to outside airborne noise propagation. In this paper, a simplified integral energy method is developed to predict the noise induced by the engine sources during the pass-by noise test in the medium and high frequency range. We will consider a local energy balance and solve an integral equation to predict the noise emitted by the engine in a short computation time. One of the main contributions of this paper is the calculation of the visibilities between elements to take into account the presence of the engine. Standard pass-by noise measurements done on a test track are compared with those obtained by the simplified energy method.

  • 36.
    Araujo, C. Moysés
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Teknisk materialfysik.
    Kapilashrami, Mukes
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Teknisk materialfysik.
    Jun, Xu
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Teknisk materialfysik.
    Jayakumar, Onattu D.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Teknisk materialfysik.
    Nagar, Sandeep
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Teknisk materialfysik.
    Wu, Yan
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Teknisk materialfysik.
    Århammar, Cecilia
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Johansson, Börje
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Belova, Lyubov
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Teknisk materialfysik.
    Ahuja, Rajeev
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Gehring, Gillian A.
    Rao, K. Venkat
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Teknisk materialfysik.
    Room temperature ferromagnetism in pristine MgO thin films2010Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 96, nr 23Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Robust ferromagnetic ordering at, and well above room temperature is observed in pure transparent MgO thin films (<170 nm thick) deposited by three different techniques. Careful study of the wide scan x-ray photoelectron spectroscopy rule out the possible presence of any magnetic contaminants. In the magnetron sputtered films, we observe magnetic phase transitions as a function of film thickness. The maximum saturation magnetization of 5.7 emu/cm(3) is measured on a 170 nm thick film. The films above 500 nm are found to be diamagnetic. Ab initio calculations suggest that the ferromagnetism is mediated by cation vacancies.

  • 37.
    Arnell, Fredrik
    et al.
    KTH, Skolan för datavetenskap och kommunikation (CSC), Datorseende och robotik, CVAP.
    Petersson, Lars
    KTH, Skolan för datavetenskap och kommunikation (CSC), Datorseende och robotik, CVAP.
    Fast object segmentation from a moving camera2005Ingår i: 2005 IEEE Intelligent Vehicles Symposium Proceedings, NEW YORK, NY: IEEE , 2005, s. 136-141Konferensbidrag (Refereegranskat)
    Abstract [en]

    Segmentation of the scene is a fundamental component in computer vision to find regions of interest. Most systems that aspire to run in real-time use a fast segmentation stage that considers the whole image, and then a more costly stage for classification. In this paper we present a novel approach to segment moving objects from images taken with a moving camera. The segmentation algorithm is based on a special representation of optical flow, on which u-disparity is applied. The u-disparity is used to indirectly find and mask out the background flow in the image, by approximating it with a quadratic function. Robustness in the optical flow calculation is achieved by contrast content filtering. The algorithm successfully segments moving pedestrians from a moving vehicle with few false positive segments. Most false positive segments are due to poles and organic structures, such as trees. Such false positives are, however, easily rejected in a classification stage. The presented segmentation algorithm is intended to be used as a component in a detection/classification framework.

  • 38. Arslanov, Temirlan R.
    et al.
    Mollaev, Akhmedbek Yu.
    Kamilov, Ibragimkhan K.
    Arslanov, Rasul K.
    Kilanski, Lukasz
    Minikaev, Roman
    Reszka, Anna
    Lopez-Moreno, Sinhue
    Romero, Aldo H.
    Ramzan, Muhammad
    Panigrahi, Puspamitra
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Ahuja, Rajeev
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Trukhan, Vladimir M.
    Chatterji, Tapan
    Marenkin, Sergey F.
    Shoukavaya, Tatyana V.
    Pressure control of magnetic clusters in strongly inhomogeneous ferromagnetic chalcopyrites2015Ingår i: Scientific Reports, E-ISSN 2045-2322, Vol. 5, s. 7720-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Room-temperature ferromagnetism in Mn-doped chalcopyrites is a desire aspect when applying those materials to spin electronics. However, dominance of high Curie-temperatures due to cluster formation or inhomogeneities limited their consideration. Here we report how an external perturbation such as applied hydrostatic pressure in CdGeP2:Mn induces a two serial magnetic transitions from ferromagnet to non-magnet state at room temperature. This effect is related to the unconventional properties of created MnP magnetic clusters within the host material. Such behavior is also discussed in connection with ab initio density functional calculations, where the structural properties of MnP indicate magnetic transitions as function of pressure as observed experimentally. Our results point out new ways to obtain controlled response of embedded magnetic clusters.

  • 39.
    Ashitani, Tatsuya
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. Yamagata University, Japan.
    Garboui, S. S.
    Schubert, Fredrik
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Vongsombath, Chanda
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. National University of Laos (NOUL), Laos.
    Liblikas, I.
    Pålsson, Katinka
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Borg-Karlson, Anna-Karin
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. Institute of Technology, Estonia.
    Activity studies of sesquiterpene oxides and sulfides from the plant Hyptis suaveolens (Lamiaceae) and its repellency on Ixodes ricinus (Acari: Ixodidae)2015Ingår i: Experimental & applied acarology, ISSN 0168-8162, E-ISSN 1572-9702Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hyptis suaveolens (Lamiaceae), a plant traditionally used as a mosquito repellent, has been investigated for repellent properties against nymphs of the tick Ixodesricinus. Essential oils and volatile compounds of fresh and dried leaves, from plants originating from Laos and Guinea-Bissau, were identified by GC–MS and tested in a tick repellency bioassay. All the essential oils were strongly repellent against the ticks, even though the main volatile constituents differed in their proportions of potentially tick repellent chemicals. (+)/(−)-sabinene were present in high amounts in all preparations, and dominated the emission from dry and fresh leaves together with 1,8-cineol and α-phellandrene. 1,8-Cineol and sabinene were major compounds in the essential oils from H. suaveolens from Laos. Main compounds in H. suaveolens from Guinea-Bissau were (−)-sabinene, limonene and terpinolene. Among the sesquiterpene hydrocarbons identified, α-humulene exhibited strong tick repellency (96.8 %). Structure activity studies of oxidation or sulfidation products of germacrene D, α-humulene and β-caryophyllene, showed increased tick repellent activity: of mint sulfide (59.4 %), humulene-6,7-oxide (94.5 %) and caryophyllene-6,7-oxide (96.9 %). The substitution of oxygen with sulfur slightly lowered the repellency. The effects of the constituents in the oils can then be regarded as a trade off between the subsequently lower volatility of the sesquiterpene derivatives compared to the monoterpenes and may thus increase their potential usefulness as tick repellents.

  • 40. Ashley, S. F.
    et al.
    Linnemann, A.
    Jolie, J.
    Regan, P. H.
    Andgren, Karin
    KTH, Skolan för teknikvetenskap (SCI), Fysik. University of Surrey, United Kingdom .
    Dewald, A.
    McCutchan, E. A.
    Melon, B.
    Moeller, O.
    Zamfir, N. V.
    Amon, L.
    Boelaert, N.
    Cakirli, R. B.
    Casten, R. F.
    Clark, R. M.
    Fransen, C.
    Gelletly, W.
    Gurdal, G.
    Heidemann, M.
    Keyes, K. L.
    Erduran, M. N.
    Meyer, D. A.
    Papenberg, A.
    Plettner, C.
    Rainovski, G.
    Ribas, R. V.
    Thomas, Nathaniel J.
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Vinson, J.
    Warner, D. D.
    Werner, V.
    Williams, E.
    Zell, K. O.
    Lifetime determination of excited states in Cd-1062007Ingår i: Acta Physica Polonica B, ISSN 0587-4254, E-ISSN 1509-5770, Vol. 38, nr 4, s. 1385-1388Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two separate experiments using the Differential Decay Curve Method have been performed to extract mean lifetimes of excited states in 106 Cd. The inedium-spin states of interest were populated by the Mo-98(C-12, 4n) Cd-106 reaction performed at the Wright Nuclear Structure Lab., Yale University. From this experiment, two isomeric state mean lifetimes have been deduced. The low-lying states were populated by the Mo-96(C-13, 3n)Cd-106 reaction performed at the Institut fur Kernphysik, Universitat zu Koln. The mean lifetime of the I-pi = 2(1)(+) state was deduced, tentatively, as 16.4(9) ps. This value differs from the previously accepted literature value from Coulomb excitation of 10.43(9) ps.

  • 41.
    Asplund, G
    et al.
    KTH, Tidigare Institutioner (före 2005), Pappers- och massateknik.
    Norman, Bo
    KTH, Tidigare Institutioner (före 2005), Pappers- och massateknik.
    Fibre orientation anisotropy profile over the thickness of a headbox jet2004Ingår i: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 30, nr 8, s. 217-221Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The fibre orientation anisotropy at various levels of the jet from a model headbox has been investigated. Stiff nylon fibres, 3 mm long, were added at extremely low concentrations to make it possible to observe also the centre of the jet. This meant that fibre interactions, such as floc forming, could not take place. Transparent, parallel walls enclosed the jet where fibre orientation was measured. A thin laser sheet illuminated the jet from the side and a video camera captured the light reflected perpendicularly from the fibres. Using image analysis, the orientation of the fibres was evaluated. A central vane was mounted in the headbox nozzle so the effects of the vane wake could be studied. The results show that the effect a the boundary layers, at the walls of a headbox and at the surface of a vane, was to locally reduce fibre orientation anisotropy. Depending on the vane tip shape, fibre orientation anisotropy could be additionally decreased. Overall, the fibre orientation anisotropy was weakly affected by changes inflow rate and strongly dependent on the contraction ratio in the nozzle; low speed and large contractions produced more anisotropic orientations.

  • 42.
    Azeem, Muhammad
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. Department of Chemistry, COMSATS Institute of Information Technology, Abbottabad, Pakistan.
    Terenius, Olle
    Rajarao, Gunaratna Kuttuva
    KTH, Skolan för bioteknologi (BIO), Industriell bioteknologi.
    Nagahama, Kazuhiro
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. Sojo University, Faculty of Biotechnology and Life Science, Department of Applied Microbial Technology, 4-22-1 Ikeda, Nishi-ku, Kumamoto, Japan.
    Nordenhem, Henrik
    Nordlander, Goran
    Borg-Karlson, Anna-Karin
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. Tartu University, Institute of Technology, Division of Organic Chemistry, Tartu, Estonia.
    Chemodiversity and biodiversity of fungi associated with the pine weevil Hylobius abietis2015Ingår i: Fungal Biology, ISSN 1878-6146, E-ISSN 1878-6162, Vol. 119, nr 8, s. 738-46Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The pine weevil Hylobius abietis is a severe pest of conifer seedlings in reforestation areas. Weevils lay eggs in the root bark or in the soil near roots of recently dead trees and cover the eggs with frass (feces combined with chewed bark), possibly to avoid conspecific egg predation. The aim of the present investigation focused on isolation, identification, and volatile production of fungi from pine-weevil feces and frass. Fungi were isolated from weevil frass and feces separately, followed by identification based on ITS sequencing. Fifty-nine isolates belonging to the genera Penicillium, Ophiostoma, Mucor, Leptographium, Eucasphaeria, Rhizosphaera, Debaryomyces, and Candida were identified. Volatile organic compounds (VOCs) produced by the fungal community and fungal isolates cultured on weevil-frass broth were identified by SPME-GCMS. Major VOCs emitted from the fungal community and pure isolates were species- and strain specific and included isopentylalcohol, styrene, 3-octanone, 6-protoilludene, methyl salicylate, 3-methylanisole, 2-methoxyphenol, and phenol. Some of these are known to influence the orientation of pine weevils when tested among highly attractive newly planted conifer seedlings.

  • 43.
    Bagampadde, Umaru
    et al.
    Makerere University, Kampala.
    Karlsson, R.
    KTH.
    Laboratory studies on stripping at bitumen/substrate interfaces using FTIR-ATR2007Ingår i: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 42, nr 9, s. 3197-3206Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A technique based on Fourier Transform Infrared Spectroscopy-Attenuated Total Reflectance (FTIR-ATR) was developed and used to study movement of water into bitumen/substrate interfaces, as well as to characterize stripping. Bitumens from different sources were used and applied on various substrates (silicon, germanium and zinc selenide) as thin films. The influence of bitumen type, substrate type, temperature, film thickness and modification with amines, on water damage was studied. The technique gave information on water flow into interfaces and how stripping possibly occurs. It distinguished between stripping and non-stripping bitumens. At least one of three processes occurred, namely water diffusion, film fracture, and bitumen displacement by water, respectively. The diffusion of water did not obey Fick's law. Stripping was influenced by bitumen source when silicon and germanium substrates were used. Notching the films made the process of water entry almost occur immediately. Additives significantly reduced stripping in the moisture-sensitive bitumen on silicon and germanium substrates, even after film notching. Although, good agreement was observed between tests for the bitumens that did not strip, the tests on stripping bitumens showed poor agreement.

  • 44.
    Bakari, Jabiri Kuwe
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Data- och systemvetenskap, DSV.
    Tarimo, Charles N.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Data- och systemvetenskap, DSV.
    Magnusson, Christer
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Data- och systemvetenskap, DSV.
    Yngstrom, Louise
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Data- och systemvetenskap, DSV.
    Bridging the gap between general management and technicians - A case study in ICT security2006Ingår i: Security and Privacy in Dynamic Environments / [ed] FischerHubner, S; Rannenberg, K; Yngstrom, L; Lindskog, S, NEW YORK, NY: SPRINGER , 2006, Vol. 201, s. 442-447Konferensbidrag (Refereegranskat)
    Abstract [en]

    The lack of planning, business re-engineering, and coordination in the whole process of computerisation, is the most pronounced problem facing organisations in developing countries. These problems often lead to a discontinuous link between. technology. and the business processes. As a result, the introduced technology poses some critical risks to the organisations due to the different perceptions of the management and technical staff in viewing the ICT security problem. Ibis paper discusses a practical experience of bridging the gap between the general management and ICT technicians.

  • 45.
    Bandmann, Nina
    KTH, Skolan för bioteknologi (BIO).
    Rational and combinatorial genetic engineering approaches for improved recombinant protein production and purification2007Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The bacterium Escherichia coli (E. coli) is in many situations an ideal host for production of recombinant proteins, since it generally provides a rapid and economical means to achieve sufficiently high product quantities. However, there are several factors that may limit this host’s ability to produce large amounts of heterologous proteins in a soluble and native form. For many applications a high purity of the recombinant protein is demanded, which implies a purification strategy where the product efficiently can be isolated from the complex milieu of host cell contaminants. In this thesis, different strategies based on both rational and combinatorial genetic engineering principles have been investigated, aiming at improving and facilitating recombinant E. coli protein production and purification.

    One objective was to improve the PEG/salt aqueous two-phase system (ATPS) purification process of the lipase cutinase, by increasing the selectivity of the protein for the system top-phase. Peptide tags, with varying properties, were designed and genetically fused to the C-terminal end of ZZ-cutinase. Greatly increased partitioning values were observed for purified protein variants fused to tryptophan containing peptide tags, particularly a (WP)4 peptide. The partitioning properties of the ZZ-cutinase-(WP)4 protein were also retained when added to the ATPS directly from an E. coli total cell disintegrate, emphasizing the applicability of this genetic engineering strategy for primary protein purification in ATPSs.

    Further on, a combinatorial library approach using phage display technology was investigated as a tool for identification of peptide tags capable of improving partitioning properties of ZZ-cutinase in an ATPS. Repeated ATPS-based partitioning-selection cycles of a large phagemid (pVIII) peptide library, resulted in isolation of phage particles preferentially decorated with peptides rich in tyrosine and proline residues. Both a peptide corresponding to a phage library derived peptide sequence as well as peptides designed based on information of amino acid appearance frequencies in later selection rounds, were shown to improve partitioning several-fold when genetically fused to the C-terminal end of ZZ-cutinase. From the two- to four–fold increased production yields observed for these fusion proteins compared to ZZ-cutinase-(WP)4, it was concluded that the selection system used allowed for selection of desired peptide properties related to both partitioning and E. coli protein production parameters.

    Bacterial protein production is affected by several different mRNA and protein sequence-related features. Attempts to address single parameters in this respect are difficult due to the inter-dependence of many features, for example between codon optimization and mRNA secondary structure effects. Two combinatorial expression vector libraries (ExLib1 and ExLib2) were constructed using a randomization strategy that potentially could lead to variations in many of these sequence-related features and which would allow a pragmatic search of vector variants showing positive net effects on the level of soluble protein production. ExLib1 was constructed to encode all possible synonymous codons of an eight amino acid N-terminal extension of protein Z, fused to the N-terminal of an enhanced green fluorescent reporter protein (EGFP). In ExLib2, the same eight positions were randomized using an (NNG/T) degeneracy code, which could lead to various effects on both the nucleotide and protein level, through the introduction of nucleotide sequences functional as e.g. alternative ribosome binding or translation initiation sites or as translated codons for an Nterminal extension of the target protein by a peptide sequence. Flow cytometric analyses and sorting of library cell cultures resulted in isolation of clones displaying several-fold increases in whole cell fluorescence compared to a reference clone. SDS-PAGE and western blot analyses verified that this was a result of increases (up to 24-fold) in soluble intracellular ZEGFP product protein content. Both position specific codon bias effects and the appearance of new ribosomal binding sites in the library sequences were concluded to have influenced the protein production.

    To explore the possibility of applying the same combinatorial library strategy for improving soluble intracellular production of heterologous proteins proven difficult to express in E. coli, three proteins with either bacterial (a transcriptional regulator (DntR)) or human (progesterone receptor ligand binding domain (PRLBD) and 11-β Hydroxysteroid dehydrogenase type I (11-β)) origin, were cloned into the ExLib2 library. Flow cytometric sorting of libraries resulted in isolation of DntR library clones showing increased soluble protein production levels and PR-LBD library clones with up to ten-fold increases in whole cell fluorescence, although the product under these conditions co-separated with the insoluble cell material.

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  • 46.
    Bandmann, Nina
    et al.
    KTH, Skolan för bioteknologi (BIO), Molekylär Bioteknologi.
    Nygren, Per-Åke
    KTH, Skolan för bioteknologi (BIO), Molekylär Bioteknologi.
    Combinatorial expression vector engineering for tuning of recombinant protein production in Escherichi coli2007Ingår i: Nucleic Acids Research, ISSN 0305-1048, E-ISSN 1362-4962, Vol. 35, nr 5Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The complex and integrated nature of both genetic and protein level factors influencing recombinant protein production in Escherichia coli makes it difficult to predict the optimal expression strategy for a given protein. Here, two combinatorial library strategies were evaluated for their capability of tuning recombinant protein production in the cytoplasm of E. coli. Large expression vector libraries were constructed through either conservative (ExLib1) or free (ExLib2) randomization of a seven-amino-acid window strategically located between a degenerated start codon and a sequence encoding a fluorescently tagged target protein. Flow cytometric sorting and analyses of libraries, subpopulations or individual clones were followed by SDS-PAGE, western blotting, mass spectrometry and DNA sequencing analyses. For ExLib1, intracellular accumulation of soluble protein was shown to be affected by codon specific effects at some positions of the common N-terminal extension. Interestingly, for ExLib2 where the same sequence window was randomized via seven consecutive NN(G/T) tri-nucleotide repeats, high product levels (up to 24-fold higher than a reference clone) were associated with a preferential appearance of novel SID-like sequences. Possible mechanisms behind the observed effects are discussed.

  • 47. Banwart, Steven A.
    et al.
    Berg, Astrid
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Beerling, David J.
    Process-based modeling of silicate mineral weathering responses to increasing atmospheric CO2 and climate change2009Ingår i: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 23, s. GB4013-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A mathematical model describes silicate mineral weathering processes in modern soils located in the boreal coniferous region of northern Europe. The process model results demonstrate a stabilizing biological feedback mechanism between atmospheric CO2 levels and silicate weathering rates as is generally postulated for atmospheric evolution. The process model feedback response agrees within a factor of 2 of that calculated by a weathering feedback function of the type generally employed in global geochemical carbon cycle models of the Earth's Phanerozoic CO2 history. Sensitivity analysis of parameter values in the process model provides insight into the key mechanisms that influence the strength of the biological feedback to weathering. First, the process model accounts for the alkalinity released by weathering, whereby its acceleration stabilizes pH at values that are higher than expected. Although the process model yields faster weathering with increasing temperature, because of activation energy effects on mineral dissolution kinetics at warmer temperature, the mineral dissolution rate laws utilized in the process model also result in lower dissolution rates at higher pH values. Hence, as dissolution rates increase under warmer conditions, more alkalinity is released by the weathering reaction, helping maintain higher pH values thus stabilizing the weathering rate. Second, the process model yields a relatively low sensitivity of soil pH to increasing plant productivity. This is due to more rapid decomposition of dissolved organic carbon (DOC) under warmer conditions. Because DOC fluxes strongly influence the soil water proton balance and pH, this increased decomposition rate dampens the feedback between productivity and weathering. The process model is most sensitive to parameters reflecting soil structure; depth, porosity, and water content. This suggests that the role of biota to influence these characteristics of the weathering profile is as important, if not more important, than the role of biota to influence mineral dissolution rates through changes in soil water chemistry. This process-modeling approach to quantify the biological weathering feedback to atmospheric CO2 demonstrates the potential for a far more mechanistic description of weathering feedback in simulations of the global geochemical carbon cycle.

  • 48. Baryshnikov, G. V.
    et al.
    Minaev, Boris F.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Minaeva, V. A.
    Ning, Zhijun
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Zhang, Qiong
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Structure and Spectral Properties of Truxene Dye S52012Ingår i: Optics and Spectroscopy, ISSN 0030-400X, E-ISSN 1562-6911, Vol. 112, nr 2, s. 168-174Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    On the ground of functional theory with the B3LYP and BMK functionals, we have studied the structure and optical properties of a truxene dye sensitizer S5 for photoelectric transducers. Based on the calculations of the vertical excitations energy of the dye molecule and accounting the influence of the solvent, we have revealed a positive solvatochromic effect that is weak compared to results obtained in the vacuum approximation. We have studied new features describing stabilization of the planar structure of the cyanothiophene-acrylic fragment of the S5 dye.

  • 49.
    Baryshnikov, Gleb V.
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi. Bogdan Khmelnitsky Natl Univ.
    Valiev, Rashid R.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi. Tomsk State Univ; Tomsk Polytech Univ.
    Karaush, Nataliya N.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Minaeva, Valentina A.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Sinelnikov, Alexandr N.
    Pedersen, Stephan K.
    Pittelkow, Michael
    Minaev, Boris F.
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Benzoannelated aza-, oxa- and azaoxa[8]circulenes as promising blue organic emitters2016Ingår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, nr 40, s. 28040-28051Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the present work, we studied the synergetic effect of benzoannelation and NH/O-substitution for enhancing the absorption intensity in a series of novel designed benzoannelated aza- and oxa[8]circulenes. Semi-empirical estimations of the fluorescence rate constants allowed us to determine the most promising fluorophores among all the possible benzoannelated aza-, oxa- and mixed azaoza[8]circulenes. Among them, para-dibenzoannelated [8]circulenes demonstrated the most intense light absorption and emission due to the prevailing role of the linear acene chromophore. Calculated phi(fl) values are in complete agreement with experimental data for a number of already synthesized circulenes. Thus, we believe that the most promising circulenes designed in this study can demonstrate an intensive fluorescence in the case of their successful synthesis, which in turn could be extremely useful for the fabrication of future blue OLEDs. Special attention is devoted to the aromaticity features and peculiarities of the absorption spectra for the two highly-symmetrical (D-4h ground state symmetry) pi-isoelectronic species as well as the so-called tetrabenzotetraaza[8]circulene and tetrabenzotetraoxa[8]circulene molecules. Both of them are characterized by rich electronic spectra, which can be assigned only by taking into account the vibronic coarse structure of the first electronic absorption band; the 0-1 and 0-2 transitions were found to be active in the absorption spectrum in complete agreement with experimental data obtained for both energy and intensity. The corresponding promotive vibrational modes have been determined and their vibronic activity estimated using the Franck-Condon approximation.

  • 50.
    Basylko, S. A.
    et al.
    KTH, Tidigare Institutioner (före 2005), Fysik.
    Onischouk, V. A.
    Rosengren, Anders
    KTH, Tidigare Institutioner (före 2005), Fysik.
    ac conductivity of a Coulomb glass from computer simulations2004Ingår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 70, nr 2, s. 024201-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A method for calculating the photon-induced hopping ac conductivity of a Coulomb glass by computer simulation is proposed. Results obtained by using an effective relaxation algorithm for two three-dimensional models of a Coulomb glass are reported. ac conductance data clearly demonstrate the transition from super-linear to a sub-quadratic power law. We argue that the same qualitative behavior should be expected for compensated semiconductors. It is shown that the transition is driven by the Coulomb energy of sites forming resonant pairs and not by the width of the Coulomb gap.

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