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  • 28751.
    Freidenvall, Lenita
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Political Science.
    Krook, Mona Lena
    Department of Political Science, Washington University in St. Louis, USA.
    Discursive Strategies for Institutional Reform: Gender Quotas in Sweden and France2010In: Gender, Politics, and Institutions: Towards a Feminist Institutionalism / [ed] Mona Lena Krook and Fiona Mackay, Basingstoke: Palgrave Macmillan, 2010, 1, p. 42-57Chapter in book (Refereed)
  • 28752.
    Freidenvall, Lenita
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Political Science.
    Micheletti, Michele
    Stockholm University, Faculty of Social Sciences, Department of Political Science.
    Our Colleague Drude: At home and abroad2012In: Comparisons, Quotas and Critical Change / [ed] Lenita Freidenvall and Michele Micheletti, Stockholm: Department of Political Science, Stockholm University , 2012, p. 7-19Chapter in book (Other academic)
  • 28753.
    Freidenvall, Lenita
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Political Science.
    Rönnbäck, Josefin
    Bortom rösträtten: kön, politik och medborgarskap i Norden2011Book (Other academic)
  • 28754.
    Freidenvall, Lenita
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Political Science.
    Rönnbäck, Josefin
    Inledning: Bortom rösträtten2011In: Bortom rösträtten: Kön, politik och medborgarskap i Norden / [ed] Lenita Freidenvall och Josefin Rönnbäck, Huddinge: Södertörns högskola , 2011, p. 7-34Chapter in book (Other academic)
  • 28755.
    Freidenvall, Lenita
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Political Science.
    Sawer, Marian
    Framing Women Politicians in Old Democracies2013In: Breaking male dominance in old democracies / [ed] Drude Dahlerup & Monique Leijenaar, Oxford: Oxford University Press, 2013, 1, p. 260-275Chapter in book (Refereed)
    Abstract [en]

    This chapter looks at the changing ways in which women politicians have been framed over time. The dominant attitude at the time when women got the vote was that women’s proper role was in the family and not in politics (maternal discourse). A more recent discourse, ‘no democracy without parity’, refers to a democratic deficit if women or minorities are not fully included in the political institutions. The most commonly used arguments for more women in politics were that women would bring specific knowledge and priorities to politics, that as equal citizens women should have equal rights to participate in the decision-making and that women would change the way politics was done. The most recent discourse is that women are needed in politics to clean up the mess caused by men.

  • 28756.
    Freidenvall, Lenita
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Political Science.
    Upmark, Gunilla
    Jämställt? Röster från riksdagen 2010: En uppföljningsrapport2012Report (Other academic)
  • 28757.
    Freider, Ellen
    Stockholm University, Faculty of Humanities, Department of Swedish Language and Multilingualism.
    EU och du: En diskursanalytisk undersökning av två informationsbroschyrer från EU-kommissionen2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    I denna uppsats undersöks EU-kommissionens kommunikation med allmänheten i två översatta informationsbroschyrer. Med avstamp i diskursanalytisk teori analyseras såväl texterna som deras kontext. Syftet med undersökningen är att beskriva vilken bild broschyrerna förmedlar av EU och EU- invånarna samt relationen dem emellan. En utgångpunkt är att texterna bär uttryck för auktoritet, som beror av de text-externa relationerna och som synliggörs genom olika språkliga strategier.

    Analysen visar att EU konstrueras på två olika sätt i texterna: dels som en stark och pålitlig aktör, dels som ett naturligt existerande geografiskt område. EU-invånaren i sin tur upptecknas som en del av en gemenskap, och som någon med skyldigheter men framförallt med rättigheter. Broschyrerna uttrycker auktoritet genom språkliga strategier som signalerar makt och solidaritet, men EU:s reella makt över invånarna är ofta nedtonad. Texterna reflekterar en värld där EU:s ställning inte är oomstridd, och broschyrerna verkar på flera sätt för att ge unionen existensberättigande.

    Undersökningen aktualiserar också frågor om hur översättningsaspekten inverkar på diskursen, och mynnar ut i konstaterandet att översättarna har en betydande roll i sammanhanget.

  • 28758.
    Freidlitz, Ulrika
    et al.
    Stockholm University, Faculty of Social Sciences, School of Business.
    Alvarez, Patricia
    Stockholm University, Faculty of Social Sciences, School of Business.
    "Det goda företaget" - En fallstudie på The Body Shop1999Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Denna uppsats är en fallstudie där vi undersöker begreppet "Det goda företaget" och huruvida The Body Shop är ett gott företag. Syftet är: att belysa begreppet "Det goda företaget" utifrån ett intresse för marknadskommunikation. Sammanfattningsvis anser vi att The Body Shop är ett etiskt företag, men att det finns brister som skulle kunna förbättras.

  • 28759. Freier, Ronny
    et al.
    Odendahl, Christian
    Stockholm University, Faculty of Social Sciences, Department of Economics.
    Do parties matter? Estimating the effect of political power in multi-party systems2015In: European Economic Review, ISSN 0014-2921, E-ISSN 1873-572X, Vol. 80, p. 310-328Article in journal (Refereed)
    Abstract [en]

    When there are more than two parties, policy outcomes are typically the result of a bargaining process. We investigate whether changes in political power for various parties have an effect on tax policies. We use an instrumental variable approach where close elections provide the exogenous variation in our variable of interest: voting power. In order to isolate close elections in a proportional election system, we develop a new simulation algorithm. Using data from German municipalities in the state of Bavaria, our estimation results suggest that political power does matter for policies. Somewhat surprisingly, the center-left party SPD is found to lower all three locally controlled taxes, whereas The Greens increase both property taxes considerably. These results remain robust across a range of specifications. Our partisan effect for the SPD is also confirmed by a simple regression discontinuity estimation using mayoral elections.

  • 28760.
    Freij, Lars W.
    Stockholm University, Faculty of Humanities.
    Türlosigkeit: Robert Musils Törless in Mikroanalysen mit Ausblicken auf andere Texte des Dichters1972Doctoral thesis, monograph (Other academic)
  • 28761.
    Freiman, Maria
    Stockholm University, Faculty of Social Sciences, Department of Special Education.
    Hur ska vi göra nu då?: Svensklärares förväntningar på speciallärarrollen.2013Independent thesis Advanced level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    År 2008 återinfördes speciallärarutbildningen efter att ha legat i träda under drygt tjugo år. I denna studie förs den nya speciallärarrollen in i ett historiskt sammanhang genom en återblick på hur svensk specialundervisningen växt fram från 1800-talet fram till idag. Även kopplingar mellan den specialpedagogiska- och den allmänna lärarutbildningen i svenska behandlas. Syftet med studien är att belysa verksamma svensklärares förväntningar på speciallärarrollen med inriktning språk-, läs- och skrivutveckling. I intervjuerna med de sju svensklärarna på mellan- och högstadiet, framträder fyra villkor: ”svaga” elever, styrdokument, kontrollbehov och arbetsbörda. Tillsammans formar dessa villkor svensklärarnas skolvardag och ligger till grund för deras förväntningar på speciallärarrollen. Lärarintervjuerna visar på många olika och till vissa delar motstridiga förväntningar på speciallärarrollen. Dessa förväntningar tillsammans med den skolpolitiska styrningen i form av till exempel examensordingen gör att speciallärarrollen kan sägas befinna sig i en legitimitetskonflikt.

  • 28762. Freimann, Krista
    et al.
    Arukuusk, Piret
    Kurrikoff, Kaido
    Pärnaste, Ly
    Raid, Raivo
    Piirsoo, Andres
    Pooga, Margus
    Langel, Ülo
    Stockholm University, Faculty of Science, Department of Neurochemistry. University of Tartu, Estonia.
    Formulation of Stable and Homogeneous Cell-Penetrating Peptide NF55 Nanoparticles for Efficient Gene Delivery In Vivo2018In: Molecular Therapy - Nucleic Acids, ISSN 2162-2531, E-ISSN 2162-2531, Vol. 10, p. 28-35Article in journal (Refereed)
    Abstract [en]

    Although advances in genomics and experimental gene therapy have opened new possibilities for treating otherwise incurable diseases, the transduction of nucleic acids into the cells and delivery in vivo remain challenging. The high molecular weight and anionic nature of nucleic acids require their packing into nanoparticles for the delivery. The efficacy of nanoparticle drugs necessitates the high bioactivity of constituents, but their distribution in organisms is mostly governed by the physical properties of nanoparticles, and therefore, generation of stable particles with strictly defined characteristics is highly essential. Using previously designed efficient cell-penetrating peptide NF55, we searched for strategies enabling control over the nanoparticle formation and properties to further improve transfection efficacy. The size of the NF55/pDNA nanoparticles correlates with the concentration of its constituents at the beginning of assembly, but characteristics of nanoparticles measured by DLS do not reliably predict the applicability of particles in in vivo studies. We introduce a new formulation approach called cryo-concentration, where we acquired stable and homogeneous nanoparticles for administration in vivo. The cryo-concentrated NF55/pDNA nanoparticles exhibit several advantages over standard formulation: They have long shelf-life and do not aggregate after reconstitution, have excellent stability against enzymatic degradation, and show significantly higher bioactivity in vivo.

  • 28763. Freimann, Krista
    et al.
    Arukuusk, Piret
    Kurrikoff, Kaido
    Vasconcelos, Luís Daniel Ferreira
    Stockholm University, Faculty of Science, Department of Neurochemistry.
    Veiman, Kadi-Liis
    Uusna, Julia
    Margus, Helerin
    Garcia-Sosa, Alfonso T.
    Pooga, Margus
    Langel, Ülo
    Stockholm University, Faculty of Science, Department of Neurochemistry. University of Tartu, Estonia.
    Optimization of in vivo DNA delivery with NickFect peptide vectors2016In: Journal of Controlled Release, ISSN 0168-3659, E-ISSN 1873-4995, Vol. 241, p. 135-143Article in journal (Refereed)
    Abstract [en]

    As the field of gene therapy progresses, an increasingly urgent need has arisen for efficient and non-toxic vectors for the in vivo delivery of nucleic acids. Cell-penetrating peptides (CPP) are very efficient transfection reagents in vitro, however, their application in vivo needs improvement. To enhance in vivo transfection we designed various CPPs based on previous knowledge of internalization studies and physiochemical properties of NickFect (NF) nanoparticles. We show that increment of the helicity of these Transportan10 analogues improves the transfection efficiency. We rationally design by modifying the net charge and the helicity of the CPP a novel amphipathic α-helical peptide NF55 for in vivo application. NF55 condenses DNA into stable nanoparticles that are resistant to protease degradation, promotes endosomal escape, and transfects the majority of cells in a large cell population. We demonstrate that NF55 mediates DNA delivery in vivo with gene induction efficiency that is comparable to commercial transfection reagents. In addition to gene induction in healthy mice, NF55/DNA nanoparticles showed promising tumor transfection in various mouse tumor models, including an intracranial glioblastoma model. The efficiency of NF55 to convey DNA specifically into tumor tissue increased even further after coupling a PEG2000 to the peptide via a disulphide-bond. Furthermore, a solid formulation of NF55/DNA displayed an excellent stability profile without additives or special storage conditions. Together, its high transfection efficacy and stability profile make NF55 an excellent vector for the delivery of DNA in vivo.

  • 28764. Freimann, Krista
    et al.
    Kurrikoff, Kaido
    Langel, Ülo
    Stockholm University, Faculty of Science, Department of Neurochemistry. University of Tartu, Estonia.
    Galanin receptors as a potential target for neurological disease2015In: Expert opinion on therapeutic targets, ISSN 1472-8222, E-ISSN 1744-7631, Vol. 19, no 12, p. 1665-1676Article in journal (Refereed)
    Abstract [en]

    INTRODUCTION: Galanin is a 29/30 amino acid long neuropeptide that is widely expressed in the brains of many mammals. Galanin exerts its biological activities through three different G protein-coupled receptors, GalR1, GalR2 and GalR3. The widespread distribution of galanin and its receptors in the CNS and the various physiological and pharmacological effects of galanin make the galanin receptors attractive drug targets.

    AREAS COVERED: This review provides an overview of the role of galanin and its receptors in the CNS, the involvement of the galaninergic system in various neurological diseases and the development of new galanin receptor-specific ligands.

    EXPERT OPINION: Recent advances and novel approaches in migrating the directions of subtype-selective ligand development and chemical modifications of the peptide backbone highlight the importance of the galanin neurochemical system as a potential target for drug development.

  • 28765.
    Freire, Francis
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Acoustic characterization of submarine geomorphological features in the Polar Oceans2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Marine glacial environments contain unique seafloor features resulting from the dynamic glacial processes. Studying these submarine geomorphological features can help us understand the glacial paleo-environments so that we can predict the likely responses of present day glaciers and ice sheets to future changes in the climate. This thesis details different approaches in understanding glacial seafloor features using acoustic systems. It focuses on the novel technique of automated mapping seafloor properties using the backscatter intensity collected by acoustic multibeam echosounder systems (MBES). The aim of this thesis is to assess the potential of this unexploited data source in characterizing different glacial landforms in the polar oceans. This is done by examining the voluminous backscatter data collected by Swedish icebreaker Oden from different cruises to the polar oceans and employing an automated backscatter processing technique, the ARA algorithm, to extract surficial sediment characteristics. The results from the sediment characterization are used together with outputs from other marine acoustical systems and sediment core data to understand formational processes of the glacial submarine features. Operational issues encountered in using this technology and its viability as a tool in characterization of glacial seafloor features are discussed and suggestions are given on the improvements needed to effectively implement the method in future studies. The final part of the manuscript is a paper, published in Geo-marine Letters, where I and my co-authors show a practical application of the acoustic systems ability to characterize geomorphological features of a mass-wasting event in the deepest part of the Arctic, the Molloy Hole. 

  • 28766.
    Freire, Francis Fletcher
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    High Arctic submarine glaciogenic landscapes: their formation and significance2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is focused on studies of glacial and slope morphology in the high Arctic of western Greenland shelf and the Molloy Hole seafloor spreading area, based on high-resolution acoustic methods and other geophysical data. The main purpose is to improve our understanding of glacial dynamics and associated processes in the marginal region of a large marine-terminating ice sheet. Newly acquired data, together with existing datasets have been compiled to create bathymetric models, which were used to study the seafloor landscape and its preserved record of glacial and sedimentary processes. The new bathymetric models were used with novel processing tools combined with seismic profiles, sub-bottom profiles and overlays of geological- and gravimetric maps to describe the observed landforms and interpret causal relationships. The main conclusions are:

    1)   The underlying geology is an important control on the cross-shelf trough (CST) dimensions in western Greenland. This is likely due to the influence of underlying geology to the frictional resistance of the ice flow over the basement rock. Our observations show that ice streaming in areas with basaltic bed-types cause minimal over-deepening of the main trunk of the trough, which also has weaker lateral boundaries allowing the ice stream to shift flow direction more easily. CSTs on the Cenozoic-Mesozoic sedimentary basins indicate a stronger eroding and more focused paleo-ice streams.

    2)   Bedrock lithology has an important part in controlling the location of the head-to-trough transition in CSTs of western Greenland. The areas where the head’s network of channels converges to form the main trunk of the trough are mostly located on the boundary from crystalline to sedimentary bedrock. These areas are also marked by distinct over-deepenings.

    3)   Preglacial conditions such as faults/fractures and lithological properties of the basement rocks in western Greenland served as an important control on the erosional potential of the glacial processes, particularly on a local scale. Faults and fractures have led to the topographic steering of the ice flow that causes further excavation and erosion of the bed, while uneven erosion patterns, based on differences in glacial morphological features, is observed between areas of adjacent bedrocks with different lithology.

    4)   The occurrence of trough mouth fans is suggested to be controlled mainly by the shelf width, which governs the glacial flow length along available sediment sources. It is also controlled by the continental slope steepness, which may be too steep for sediment fans to accumulate, or may cause slope failure which eventually transports the sediments to the deep basin.

    5)   The maximum ice extent in west Greenland extended towards the shelf edge. Geomorphological evidence of ice margin standstills and slow retreat (grounding zone wedges and transverse moraines) in some areas reveal a multi-stage deglaciation process.

    6)   The view of a highly dynamic paleo-Greenland ice sheet is supported by the presence of a large number of CSTs which hosted ice streams, and evidence of ice stream flow-switching throughout one or several glaciations.

    7)   The influence of glacial sedimentary processes extends into the deepest areas of the Arctic Ocean. A submarine landslide, here termed the Molloy Slide, has been described in the Molloy Hole in the Davis Strait between Greenland and Svalbard. This slide was likely caused by massive glacial sediment deposition along the west Svalbard margin.

  • 28767.
    Freire, Francis
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Gyllencreutz, Richard
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Greenwood, Sarah L.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Mayer, Larry
    Egilsson, Arnar
    Thorsteinsson, Tomas
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    High resolution mapping of offshore and onshore glaciogenic features in metamorphic bedrock terrain, Melville Bay, northwestern Greenland2015In: Geomorphology, ISSN 0169-555X, E-ISSN 1872-695X, Vol. 250, p. 29-40Article in journal (Refereed)
    Abstract [en]

    Geomorphological studies of previously glaciated landscapes are important to understand how ice sheets and glaciers respond to rapidly changing climate. Melville Bay, in northwestern Greenland, contains some of the most sensitive but least studied ice sheet sectors in the northern hemisphere, where the bathymetric knowledge previously was restricted to a few sparsely distributed single beam echo soundings. We present here the results of high-resolution, geomorphological mapping of the offshore and onshore landscapes in Melville Bay using multibeam sonar and satellite data, at 5- and 10-m resolutions respectively. The results show a similar areally-scoured bedrock-dominated landscape with a glacially modified cnoc-and-lochan morphology on the inner shelf (150-500 m depth) and on the nearby exposed coast. This is manifested by the presence of U-shaped troughs, moutonee-type elongated landforms, stoss-and-lee forms, and streamlined features. The submarine landscape shows features that are characteristic of bedrock in folded, faulted, and weathered metamorphic terrain, and, to a lesser extent, glacially molded bedforms; while coastal landforms exhibit higher relief, irregular-shaped basins, and more subdued fracture valleys. Although generally similar, the onshore and offshore landscapes contain examples of distinctly different landform patterns, which are interpreted to reflect a longer exposure to long-term deep weathering as well as to more recent periglacial weathering processes on land. The spatial variability in the distribution of landforms across the landscape in both study areas is mostly attributed to differences in lithological properties of the bedrock. The lack of sediment cover on the inner shelf is likely a result of a capacity for sediment erosion and removal by the West Greenland Current flowing northward over the area in combination with limited sediment supply from long sea ice-cover seasons. The distribution and orientation of the landforms in the offshore part indicate ice movement toward the NW, and suggests that this area acted as a tributary or onset region for the major paleo ice stream that formed the present day Melville Bay Trough.

  • 28768.
    Freire, Francis
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Gyllencreutz, Richard
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Jafri, Rooh Ullah
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Acoustic evidence of a submarine slide in the deepest part of the Arctic, the Molloy Hole2014In: Geo-Marine Letters, ISSN 0276-0460, E-ISSN 1432-1157, Vol. 34, no 4, p. 315-325Article in journal (Refereed)
    Abstract [en]

    The western Svalbard continental margin contains thick sediment sequences with areas known to contain gas hydrates. Together with a dynamic tectonic environment, this makes the region prone to submarine slides. This paper presents results from geophysical mapping of the deepest part of the high Arctic environment, the Molloy Hole. The mapping includes multibeam bathymetry, acoustic backscatter and sub-bottom profiling. The geophysical data reveal seabed features indicative of sediment transport and larger-scale mass wasting. The large slide scar is here referred to as the Molloy Slide. It is located adjacent to the prominent Molloy Hole and Ridge system. The slide is estimated to have transported >65 km(3) of sediments over the deep axial valley of the Molloy Ridge, and further into the Molloy Hole. A unique feature of this slide is that, although its run-out distance is relatively short (<5 km), it extends over an enormous vertical depth (>2,000 m) as a result of its position in a complex bathymetric setting. The slide was most likely triggered by seismic activity caused by seafloor spreading processes along the adjacent Molloy Ridge. However, gas-hydrate destabilization may also have played a role in the ensuing slide event.

  • 28769.
    Freire, Francis
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Gyllencreutz, Richard
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Initial Results from Seafloor Characterization of Arctic and Antarctic Margins using Multibeam Backscatter2012In: Arctic Palaeoclimate and its Extremes: APEX VI / [ed] Ninna Immonen, Martin Jakobsson, Juha Pekka Lunkka, Kari Strand, Oulu: University of Oulu , 2012, p. 51-51Conference paper (Other academic)
    Abstract [en]

    The seafloor of high-latitude Polar margins is characterized by various submarine glacigenic landforms whose shape and texture were created, and subsequently modified, by ice. These glaciogenic landforms together with deposited seafloor sediments serve as a record of the past glacial history. The Multibeam Echo Sounder (MBES) technology provides a tool to map and study submarine glaciogenic landforms and seafloor texture. MBES bathymetric images have afforded scientists a way to understand many glacial processes such as iceberg movements, advance and retreat patterns of ice sheets, and polar underwater currents, among others. Aside from measuring the bathymetry, MBES systems also record the returned intensity, or backscatter, of the acoustic pulse. Recent developments have shown that the backscatter information can be used to distinguish/classify differences in the surface sediment types. Here we present the preliminary results of an analysis of backscatter data aimed to characterize sediment types at locations of the Arctic and Antarctic margins mapped with Swedish icebreaker Oden and the installed Kongsberg EM122, 12 kHz, deep water MBES. We apply the Angular Range Analysis (ARA) method that is included in the Geocoder Backscatter processing algorithm [Fonseca and Mayer, 2007]. The results are correlated with other geophysical data and core samples to ground-truth the resulting seafloor maps.

  • 28770.
    Freire, Francis
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Gyllencreutz, Richard
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Zingerlersen, Karl
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Paleo-ice stream behavior inferred from cross-shelf troughs and submarine glaciogenic debris flows along the west Greenland continental marginManuscript (preprint) (Other academic)
  • 28771. Freire, P. C. C.
    et al.
    Abdo, A. A.
    Ajello, M.
    Allafort, A.
    Ballet, J.
    Barbiellini, G.
    Bastieri, D.
    Bechtol, K.
    Bellazzini, R.
    Blandford, R. D.
    Bloom, E. D.
    Bonamente, E.
    Borgland, A. W.
    Brigida, M.
    Bruel, P.
    Buehler, R.
    Buson, S.
    Caliandro, G. A.
    Cameron, R. A.
    Camilo, F.
    Caraveo, P. A.
    Cecchi, C.
    Celik, O.
    Charles, E.
    Chekhtman, A.
    Cheung, C. C.
    Chiang, J.
    Ciprini, S.
    Claus, R.
    Cognard, I.
    Cohen-Tanugi, J.
    Cominsky, L. R.
    de Palma, F.
    Dermer, C. D.
    do Couto e Silva, E.
    Dormody, M.
    Drell, P. S.
    Dubois, R.
    Dumora, D.
    Espinoza, C. M.
    Favuzzi, C.
    Fegan, S. J.
    Ferrara, E. C.
    Focke, W. B.
    Fortin, P.
    Fukazawa, Y.
    Fusco, P.
    Gargano, F.
    Gasparrini, D.
    Gehrels, N.
    Germani, S.
    Giglietto, N.
    Giordano, F.
    Giroletti, M.
    Glanzman, T.
    Godfrey, G.
    Grenier, I. A.
    Grondin, M. -H
    Grove, J. E.
    Guillemot, L.
    Guiriec, S.
    Hadasch, D.
    Harding, A. K.
    Johannesson, G.
    Johnson, A. S.
    Johnson, T. J.
    Johnston, S.
    Katagiri, H.
    Kataoka, J.
    Keith, M.
    Kerr, M.
    Knoedlseder, J.
    Kramer, M.
    Kuss, M.
    Lande, J.
    Latronico, L.
    Lee, S. -H
    Lemoine-Goumard, M.
    Longo, F.
    Loparco, F.
    Lovellette, M. N.
    Lubrano, P.
    Lyne, A. G.
    Manchester, R. N.
    Marelli, M.
    Mazziotta, M. N.
    McEnery, J. E.
    Michelson, P. F.
    Mizuno, T.
    Moiseev, A. A.
    Monte, C.
    Monzani, M. E.
    Morselli, A.
    Moskalenko, I. V.
    Murgia, S.
    Nakamori, T.
    Nolan, P. L.
    Norris, J. P.
    Nuss, E.
    Ohsugi, T.
    Okumura, A.
    Omodei, N.
    Orlando, E.
    Ozaki, M.
    Paneque, D.
    Parent, D.
    Pesce-Rollins, M.
    Pierbattista, M.
    Piron, F.
    Porter, T. A.
    Raino, S.
    Ransom, S. M.
    Ray, P. S.
    Reimer, A.
    Reimer, O.
    Reposeur, T.
    Ritz, S.
    Romani, R. W.
    Roth, M.
    Sadrozinski, H. F. -W
    Parkinson, P. M. Saz
    Sgro, C.
    Shannon, R.
    Siskind, E. J.
    Smith, D. A.
    Smith, P. D.
    Spinelli, P.
    Stappers, B. W.
    Suson, D. J.
    Takahashi, H.
    Tanaka, T.
    Tauris, T. M.
    Thayer, J. B.
    Theureau, G.
    Thompson, D. J.
    Thorsett, S. E.
    Tibaldo, L.
    Torres, D. F.
    Tosti, G.
    Troja, E.
    Vandenbroucke, J.
    Van Etten, A.
    Vasileiou, V.
    Venter, C.
    Vianello, G.
    Vilchez, N.
    Vitale, V.
    Waite, A. P.
    Wang, P.
    Wood, K. S.
    Yang, Zhaoyu
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Ziegler, M.
    Zimmer, Stephan
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Fermi Detection of a Luminous gamma-Ray Pulsar in a Globular Cluster2011In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 334, no 6059, p. 1107-1110Article in journal (Refereed)
    Abstract [en]

    We report on the Fermi Large Area Telescope's detection of gamma-ray (>100 mega-electron volts) pulsations from pulsar J1823-3021A in the globular cluster NGC 6624 with high significance (similar to 7 sigma). Its gamma-ray luminosity, L(gamma) = (8.4 +/- 1.6) x 10(34) ergs per second, is the highest observed for any millisecond pulsar (MSP) to date, and it accounts for most of the cluster emission. The nondetection of the cluster in the off-pulse phase implies that it contains <32 gamma-ray MSPs, not similar to 100 as previously estimated. The gamma-ray luminosity indicates that the unusually large rate of change of its period is caused by its intrinsic spin-down. This implies that J1823-3021A has the largest magnetic field and is the youngest MSP ever detected and that such anomalous objects might be forming at rates comparable to those of the more normal MSPs.

  • 28772. Freitas, André
    et al.
    Peña, Carlos
    Stockholm University, Faculty of Science, Department of Zoology. Zoologisk ekologi.
    Description of genus Guaianaza for "Euptychia" pronophila (Lepidoptera: Nymphalidae: Satyrinae) with a description of the immature stages2006In: Zootaxa, ISSN 1175-5326, E-ISSN 1175-5334, Vol. 1163, p. 49-59Article in journal (Refereed)
    Abstract [en]

    The satyrine Euptychia pronophila Butler (Nymphalidae) was described in 1867 in the “catch-all” genus Euptychia, but was recently treated as incertae sedis. A DNA-based cladistic analysis confirms that it belongs to the Euptychiina, as sister to Forsterinaria and closely related to Taygetis, Posttaygetis, Parataygetis, Pseudodebis, and Harjesia. Although immature morphology also suggests that this species is closely related to Forsterinaria, none of the adult morphological synapomorphies for the genera in the aforementioned clade occur in E. pronophila, a highly autapomorphic species. Because we were unable to place it with confidence in an established genus, the monotypic satyrine genus Guaianaza Freitas & Peña New Genus is described, with Euptychia pronophila Butler as the type species

  • 28773. Freites, J Alfredo
    et al.
    Tobias, Douglas J
    von Heijne, Gunnar
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    White, Stephen H
    Interface connections of a transmembrane voltage sensor.2005In: Proc Natl Acad Sci U S A, ISSN 0027-8424, Vol. 102, no 42, p. 15059-64Article in journal (Refereed)
  • 28774.
    Frejd, Jonas
    Stockholm University, Faculty of Social Sciences, Department of Human Geography.
    Låt bilen stå!: Hur förmår vi Stockholmsbilister att välja kollektivtrafik?2011Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Efter decennier av trafikplanering influerad av den amerikanska staden där bilen står i centrum så har Stockholm blivit en utspridd stad där vägar och parkeringsplatser fungerar som geografiska och sociala barriärer, dessutom innebär biltrafikens koldioxidutsläpp en negativ ekologisk miljöpåverkan. Syftet med denna studie är att kunna presentera ett antal åtgärder som kan påverka människor att i större utsträckning välja kollektivtrafik före bil. Som underlag för studien gjordes en webbenkät riktad till personer boende i Stockholm med tillgång till bil och körkort. Med stöd av Fredrik Barths generativa modell och ett antal mikroekonomiska teorier så analyseras svaren av webbenkäten för att slutligen mynna ut i ett antal förslag på åtgärder. Dessa åtgärder passar väl in i tre åtgärdskategorier som Banverket tagit fram i rapporten ”kollektivtrafik som norm”.

  • 28775.
    Frejd, Viveca
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Education.
    Christensen Eklund, Eva
    Stockholm University, Faculty of Social Sciences, Department of Education.
    Kvinnor 50+: Högskoleutbildning som framtidsstrategi2011Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The purpose of this research report is to examine how women, 50 years old or more, use their university education in establishing their future strategy. To answer our research question both quantitative and qualitative surveys were made. The qualitative method consisted of a questionnaire sent out to 30 women at Linköping university. The qualitative method consisted of three interviews with randomly selected women from the formerly mentioned group of responders. The conclusions are based upon the results from the questionnaries and the interviews, as well as the literature chosen for this research report. The literature deals with concepts such as lifelong learning. Being closely related to both work and education, lifelong learning became a key role for this study as a whole. The results show that the urge for development, both regarding professional competence and that of a personal level, has been an important factor in the process to start studying. The women´s views on the objectives and possibilities are about fostering personal growth, where new challenges or the alternative way of working can enchance life quality. Another conclusion is that by studying at the university the number of work options is increased. Thus the women strengthen their position in the labour market.

  • 28776.
    Frejka, Tomas
    et al.
    Independent researcher, International.
    Sobotka, Tomas
    Vienna Institute of Demography, Austrian Academy of Sciences, Austria.
    Hoem, Jan M.
    Stockholm University, Faculty of Social Sciences, Department of Sociology.
    Toulemon, Laurent
    Institut national d´études démographiques (INED), France.
    Summary and general conclusions: Childbearing Trends and Policies in Europe2008In: Demographic Research, ISSN 1435-9871, Vol. 19, no 2, p. 5-14Article in journal (Refereed)
    Abstract [en]

    European fertility early in the 21st century was at its lowest level since the Second World War. This study explores contemporary childbearing trends and policies in Europe, and gives detailed attention to the past two or three decades. We felt motivated to undertake this project because in many European countries, as well as for the European Union as a whole, the overall fertility level and its consequences are of grave concern and draw attention on the political stage. Our account focuses somewhat more on the previously state socialist countries of Central and Eastern Europe, where available knowledge about the impact on childbearing of the momentous political and economic transition that started in 1989 remains relatively scarce. As family formation and childbearing behaviour are inherent components of societal life, they were influenced and modified by the various political, economic, and social changes that took place in Europe during the past 60 years. There were also profound changes in norms, values, beliefs, and attitudes regarding family and childbearing, and these exerted additional effects on fertility and family trends. To identify such effects, this study pays much attention to the influence of social and family policies on fertility, to the influence of political and economic changes on fertility and family trends, and to the diverse ways changes in values, norms, and attitudes relate to the transformation in family-related behaviour in Europe. In the present chapter, we outline main issues discussed in the subsequent overview chapters, and summarise the main findings of the entire study.

  • 28777.
    Fremling, Christoffer
    Stockholm University, Faculty of Science, Department of Astronomy.
    PTF12os and iPTF13bvn: Two stripped-envelope supernovae discovered by the Palomar Transient Factory2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is based on research made by the intermediate Palomar Transient Factory [(i)PTF], and it is particularly closely tied to the still ongoing research on the stripped-envelope (SE) supernova (SN), iPTF13bvn (Type Ib), that occurred in the nearby galaxy NGC 5806. This SN was initially thought to have been the explosion of a very massive Wolf-Rayet (WR) star, but I have shown that this is very likely not the case. I suggest instead that the most likely scenario is that iPTF13bvn originated from a binary system where the envelope was stripped off from the SN progenitor by tidal forces from a companion star, in a similar way as for the very well studied Type IIb SN 2011dh. I have also investigated another SE SN, PTF12os (Type IIb), that occurred in the same galaxy as iPTF13bvn, with the conclusion that PTF12os and iPTF13bvn are very similar amongst themselves, and that both of them are also remarkably similar to SN 2011dh, in terms of all of the available observations (light-curves, spectra). Hydrodynamical models have been used to constrain the explosion parameters of iPTF13bvn, PTF12os and SN 2011dh; finding 56Ni masses in the range 0.063 − 0.075 M⊙, ejecta masses in the range 1.85 − 1.91 M⊙. Using the 56Ni-masses derived from our hydrodynamical modeling in combination with nebular models and late-time spectroscopy we were able to constrain the Zero-Age Main Sequence (ZAMS) mass to ∼ 12 M⊙ for iPTF13bvn and ≲ 15 M⊙ for PTF12os. In current stellar evolution models, stars with these masses on the ZAMS cannot lose their hydrogen envelopes and become SE SNe without binary interactions.

  • 28778.
    Fremling, Christoffer
    Stockholm University, Faculty of Science, Department of Astronomy.
    Stripped-envelope supernovae discovered by the Palomar Transient Factory2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is based on research made by the intermediate Palomar Transient Factory [(i)PTF]. The focus is on stripped-envelope (SE) supernovae (SNe) discovered by (i)PTF, and it is closely tied to the research on the SE SN iPTF13bvn, that occurred in the nearby galaxy NGC 5806. This SN was initially thought to have been the explosion of a very massive Wolf-Rayet star, but we have shown that this is very likely not the case. We suggest instead that iPTF13bvn originated from a binary system where the envelope was stripped off from the SN progenitor by tidal forces from a companion (Paper I). PTF12os exploded in the same galaxy as iPTF13bvn, and our analysis shows that PTF12os and  iPTF13bvn were very similar, and that both were also remarkably similar to the Type IIb SN 2011dh, in terms of their light-curves and spectra. In Paper II, hydrodynamical models were used to constrain the explosion parameters of iPTF13bvn, PTF12os and SN 2011dh; finding 56Ni masses in the range 0.063-0.075 solar masses (Ms), ejecta masses in the range 1.85-1.91 Ms, and kinetic energies in the range 0.54-0.94 x 1051 erg. Furthermore, using nebular models and late-time spectroscopy we were able to constrain the Zero-Age Main Sequence (ZAMS) mass to ~ 12 Ms, for iPTF13bvn and ≤ 15 Ms for PTF12os. In current stellar evolution models, stars with these masses on the ZAMS cannot lose their envelopes and become SE SNe without binary interactions. In Paper III we investigate a peculiar SE SN, iPTF15dtg; this SN lacks both hydrogen and helium and shows a double-peaked LC with a broad main LC peak. Using hydrodynamical modeling we show that iPTF15dtg had a very large ejecta mass (~ 10 Ms), resulting from an explosion of a very massive star (~ 35 Ms). The initial peak in the LC can be explained by the presence of extended material around the star, likely due to an episode of strong mass-loss experienced by the progenitor prior to the explosion. In Paper IV we perform a statistical study of the spectra of all 176 SE SNe (Type IIb, Ib and Ic) discovered by (i)PTF. The spectra of Type Ic SNe show O absorption features that are both stronger and broader (indicating faster expansion velocities) compared to Type IIb and Type Ib SNe. These findings along with very weak He absorption support the traditional picture with Type Ic SNe being heavily stripped of their He envelopes prior to the explosions, and argue against alternative explanations, such as differences in explosive mixing of 56Ni among the SE SN subtypes.

  • 28779.
    Fremling, Christoffer
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Sollerman, Jesper
    Stockholm University, Faculty of Science, Department of Astronomy.
    Oxygen and helium in stripped-envelope supernovaeManuscript (preprint) (Other academic)
    Abstract [en]

    We present a spectral analysis of 513 spectra of 176 stripped-envelope (SE) supernovae (SNe) discovered by the untargeted Palomar Transient Factory (PTF) and intermediate PTF (iPTF) surveys. Our sample contains 44 Type Ib SNe, 55 Type IIb SNe, 59 Type Ic SNe and 18 Type Ib/c SNe. We aim to identify differences among the SE SN subtypes in order to put constraints on their progenitors via measurements of the pseudo equivalent widths (pEWs) and velocities of the He I λλ5876,7065, and O I λ7774 lines. 

    We find that Type Ic SNe show higher pEWs and velocities in their O I λ7774 absorption signatures compared to Type IIb and Type Ib SNe. The pEWs of the He I λλ5876,7065 absorption lines are similar in Type Ib and Type IIb SNe, with a few Type Ib SNe showing stronger absorptions prior to maximum light in the He I λ5876 line. The He I λλ5876,7065 velocities at maximum light are higher.

    We have also identified an anti-correlation between He I λ7065 pEW and O I λ7774 velocity among Type IIb and Type Ib SNe. If both Type Ib and Type Ic SNe had similar amounts of He, and if low mixing was responsible for hiding He in Type Ic SNe, systematically lower velocities and lower oxygen line strengths are predicted for Type Ic SNe. This is contrary to what we have observed. If He is not hidden, it must have been lost in Type Ic SNe. The anti-correlation for Type Ib and Type IIb SNe then suggests that varying amounts of He can be present the time of explosion. The observed difference in the average O I λ7774 velocity around maximum light of Type Ic (~9800 km s-1) and Type Ib SNe (~7900 km s-1) can be explained by the removal of ~0.9 solar masses from the envelope, on average, if the other explosion parameters are assumed to be unchanged between the subtypes.

  • 28780.
    Fremling, Christoffer
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). California Institute of Technology, USA.
    Sollerman, Jesper
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Kasliwal, M. M.
    Kulkarni, S. R.
    Barbarino, Cristina
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Ergon, Mattias
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Karamehmetoglu, Emir
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Taddia, Francesco
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Arcavi, I
    Cenko, S. B.
    Clubb, K.
    De Cia, A.
    Duggan, G.
    Filippenko, A.
    Gal-Yam, A.
    Graham, M. L.
    Horesh, A.
    Hosseinzadeh, G.
    Howell, D. A.
    Kuesters, D.
    Lunnan, Ragnhild
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). California Institute of Technology, USA.
    Matheson, T.
    Nugent, P. E.
    Perley, D. A.
    Quimby, R. M.
    Saunders, C.
    Oxygen and helium in stripped-envelope supernovae2018In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 618, article id A37Article in journal (Refereed)
    Abstract [en]

    We present an analysis of 507 spectra of 173 stripped-envelope (SE) supernovae (SNe) discovered by the untargeted Palomar Transient Factory (PTF) and intermediate PTF (iPTF) surveys. Our sample contains 55 Type IIb SNe (SNe 45 Type Ib SNe (SNe IIb), 56 Type Ic SNe (SNe Ic), and 17 Type Ib/c SNe (SNe Ib/c). We have compared the SE SN subtypes via measurements of the pseudo-equivalent widths (pEWs) and velocities of the He I lambda lambda 5876, 7065 and O I lambda 7774 absorption lines. Consistent with previous work, we find that SNe Ic show higher pEWs and velocities in O I lambda 7774 compared to SNe IIb and Ib. The pEWs of the He I lambda lambda 5876, 7065 lines are similar in SNe Ib and IIb after maximum light. The He I lambda lambda 5876, 7065 velocities at maximum light are higher in SNe Ib compared to SNe IIb. We identify an anticorrelation between the He I lambda 7065 pEW and O I lambda 7774 velocity among SNe IIb and Ib. This can be interpreted as a continuum in the amount of He present at the time of explosion. It has been suggested that SNe Ib and Ic have similar amounts of He, and that lower mixing could be responsible for hiding He in SNe Ic. However, our data contradict this mixing hypothesis. The observed difference in the expansion rate of the ejecta around maximum light of SNe Ic (V-m root 2E(k)/M-ej approximate to 15 000 km s(-1)) and SNe Ib (V-m approximate to 9000 km s(-1)) would imply an average He mass difference of similar to 1.4 M-circle dot, if the other explosion parameters are assumed to be unchanged between the SE SN subtypes. We conclude that SNe Ic do not hide He but lose He due to envelope stripping.

  • 28781.
    Fremling, Christoffer
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Sollerman, Jesper
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Taddia, Francesco
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Ergon, Mattias
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Fraser, M.
    Karamehmetoglu, Emir
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Valenti, S.
    Jerkstrand, A.
    Arcavi, I.
    Bufano, F.
    Elias Rosa, N.
    Filippenko, A. V.
    Fox, D.
    Gal-Yam, A.
    Howell, D. A.
    Kotak, R.
    Mazzali, P.
    Milisavljevic, D.
    Nugent, P. E.
    Nyholm, Anders
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Pian, E.
    Smartt, S.
    PTF12os and iPTF13bvn. Two stripped-envelope supernovae from low-mass progenitors in NGC 58062016In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 593, article id A68Article in journal (Refereed)
    Abstract [en]

    Context. We investigate two stripped-envelope supernovae (SNe) discovered in the nearby galaxy NGC 5806 by the (intermediate) Palomar Transient Factory [(i)PTF]. These SNe, designated PTF12os/SN 2012P and iPTF13bvn, exploded within ~520 days of one another at a similar distance from the host-galaxy center. We classify PTF12os as a Type IIb SN based on our spectral sequence; iPTF13bvn has previously been classified as Type Ib having a likely progenitor with zero age main sequence (ZAMS) mass below ~17 M. Because of the shared and nearby host, we are presented with a unique opportunity to compare these two SNe.

    Aims. Our main objective is to constrain the explosion parameters of iPTF12os and iPTF13bvn, and to put constraints on the SN progenitors. We also aim to spatially map the metallicity in the host galaxy, and to investigate the presence of hydrogen in early-time spectra of both SNe.

    Methods. We present comprehensive datasets collected on PTF12os and iPTF13bvn, and introduce a new automatic reference-subtraction photometry pipeline (FPipe) currently in use by the iPTF. We perform a detailed study of the light curves (LCs) and spectral evolution of the SNe. The bolometric LCs are modeled using the hydrodynamical code hyde. We analyze early spectra of both SNe to investigate the presence of hydrogen; for iPTF13bvn we also investigate the regions of the Paschen lines in infrared spectra. We perform spectral line analysis of helium and iron lines to map the ejecta structure of both SNe. We use nebular models and late-time spectroscopy to constrain the ZAMS mass of the progenitors. We also perform image registration of ground-based images of PTF12os to archival HST images of NGC 5806 to identify a potential progenitor candidate.

    Results. We find that our nebular spectroscopy of iPTF13bvn remains consistent with a low-mass progenitor, likely having a ZAMS mass of ~12M. Our late-time spectroscopy of PTF12os is consistent with a ZAMS mass of ~15M. We successfully identify a source in pre-explosion HST images coincident with PTF12os. The colors and absolute magnitude of this object are consistent between pre-explosion and late-time HST images, implying it is a cluster of massive stars. Our hydrodynamical modeling suggests that the progenitor of PTF12os had a compact He core with a mass of 3.25+ 0.77-0.56M at the time of the explosion, which had a total kinetic energy of 0.54+ 0.41-0.25 × 1051 erg and synthesized 0.063+ 0.020-0.011M of strongly mixed  56Ni. Spectral comparisons to the Type IIb SN 2011dh indicate that the progenitor of PTF12os was surrounded by a thin hydrogen envelope with a mass lower than 0.02M. We also find tentative evidence that the progenitor of iPTF13bvn could have been surrounded by a small amount of hydrogen prior to the explosion. This result is supported by possible weak signals of hydrogen in both optical and infrared spectra.

  • 28782.
    Fremling, Christoffer
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Sollerman, Jesper
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Taddia, Francesco
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Ergon, Mattias
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Valenti, S.
    Arcavi, I.
    Ben-Ami, S.
    Cao, Y.
    Cenko, S. B.
    Filippenko, A. V.
    Gal-Yam, A.
    Howell, D. A.
    The rise and fall of the Type Ib supernova iPTF13bvn Not a massive Wolf-Rayet star2014In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 565, article id A114Article in journal (Refereed)
    Abstract [en]

    Context. We investigate iPTF13bvn, a core-collapse (CC) supernova (SN) in the nearby spiral galaxy NGC 5806. This object was discovered by the intermediate Palomar Transient Factory (iPTF) very close to the estimated explosion date and was classified as a stripped-envelope CC SN, likely of Type Ib. Furthermore, a possible progenitor detection in pre-explosion Hubble Space Telescope (HST) images was reported, making this the only SN Ib with such an identification. Based on the luminosity and color of the progenitor candidate, as well as on early-time spectra and photometry of the SN, it was argued that the progenitor candidate is consistent with a single, massive Wolf-Rayet (WR) star. Aims. We aim to confirm the progenitor detection, to robustly classify the SN using additional spectroscopy, and to investigate if our follow-up photometric and spectroscopic data on iPTF13bvn are consistent with a single-star WR progenitor scenario. Methods. We present a large set of observational data, consisting of multi-band light curves (UBVRI, g' r' i' z') and optical spectra. We perform standard spectral line analysis to track the evolution of the SN ejecta. We also construct a bolometric light curve and perform hydrodynamical calculations to model this light curve to constrain the synthesized radioactive nickel mass and the total ejecta mass of the SN. Late-time photometry is analyzed to constrain the amount of oxygen. Furthermore, image registration of pre- and post-explosion HST images is performed. Results. Our HST astrometry confirms the location of the progenitor candidate of iPTF13bvn, and follow-up spectra securely classify this as a SN Ib. We use our hydrodynamical model to fit the observed bolometric light curve, estimating the total ejecta mass to be 1.9 M-circle dot and the radioactive nickel mass to be 0.05 M-circle dot. The model fit requires the nickel synthesized in the explosion to be highly mixed out in the ejecta. We also find that the late-time nebular r'-band luminosity is not consistent with predictions based on the expected oxygen nucleosynthesis in very massive stars. Conclusions. We find that our bolometric light curve of iPTF13bvn is not consistent with the previously proposed single massive WR-star progenitor scenario. The total ejecta mass and, in particular, the late-time oxygen emission are both significantly lower than what would be expected from a single WR progenitor with a main-sequence mass of at least 30 M-circle dot.

  • 28783.
    Fremling, Mikael
    Stockholm University, Faculty of Science, Department of Physics.
    Analytical Fock coefficients of the Laughlin state on the torusManuscript (preprint) (Other academic)
  • 28784.
    Fremling, Mikael
    Stockholm University, Faculty of Science, Department of Physics.
    Coherent state wave functions on a torus with a constant magnetic field2013In: Journal of Physics A: Mathematical and Theoretical, ISSN 1751-8113, E-ISSN 1751-8121, Vol. 46, no 27, article id 275302Article in journal (Refereed)
    Abstract [en]

    We study two alternative definitions of localized states in the lowest Landau level (LLL) on a torus. One definition is to construct localized states, as the projection of the coordinate delta function onto the LLL. Another definition, proposed by Haldane, is to consider the set of functions which have all their zeros at a single point. Since a LLL wave function on a torus, supporting N-phi magnetic flux quanta, is uniquely defined by the position of its N-phi zeros, this defines a set of functions that are expected to be localized around the point maximally far away from the zeros. These two families of localized states have many properties in common with the coherent states on the plane and on the sphere, viz a resolution of unity and a self-reproducing kernel. However, we show that only the projected delta function is maximally localized. Additionally, we show how to project onto the LLL, functions that contain holomorphic derivatives and/or anti-holomorphic polynomials, and apply our methods in the description of hierarchical quantum Hall liquids.

  • 28785.
    Fremling, Mikael
    Stockholm University, Faculty of Science, Department of Physics.
    Coherent State Wave Functions on the Torus2013Licentiate thesis, monograph (Other academic)
    Abstract [en]

    In the study of the quantum Hall effect there are still many unresolved problems. One of these is how to generate representative wave functions for ground states on other geometries than the planar and spherical. We study one such geometry, the toroidal one, where the periodic boundary conditions must be properly taken into account.

    As a tool to study the torus we investigate the properties of various types of localized states, similar to the coherent states of the harmonic oscillator, which are maximally localized in phase space. We consider two alternative definitions of localized states in the lowest Landau level (LLL) on a torus. One is the projection of the coordinate delta function onto the LLL. Another definition, proposed by Haldane & Rezayi, is to consider the set of functions which have all their zeros at a single point. Since all LLL wave functions on a torus, are uniquely defined by the position of their zeros, this defines a set of functions that are expected to be localized around the point maximally far away from the zeros. These two families of localized states have many properties in common with the coherent states on the plane and on the sphere, e.g. a simple resolution of unity and a simple self-reproducing kernel. However, we show that only the projected delta function is maximally localized.

    We find that because of modular covariance, there are severe restrictions on which wave functions that are acceptable on the torus. As a result, we can write down a trial wave function for the  state, that respects the modular covariance, and has good numerical overlap with the exact coulomb ground state.

    Finally we present preliminary calculations of the antisymmetric component of the viscosity tensor for the proposed, modular covariant, state, and find that it is in agreement with theoretical predictions.

  • 28786.
    Fremling, Mikael
    Stockholm University, Faculty of Science, Department of Physics.
    Quantum Hall Wave Functions on the Torus2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The fractional quantum Hall effect (FQHE), now entering it's fourth decade, continues to draw attention from the condensed matter community. New experiments in recent years are raising hopes that it will be possible to observe quasi-particles with non-abelian anyonic statistics. These particles could form the building blocks of a quantum computer.

    The quantum Hall states have topologically protected energy gaps to the low-lying set of excitations. This topological order is not a locally measurable quantity but rather a non-local object, and it is one of the keys to it's stability. From an early stage understanding of the FQHE has been facilitate by constructing trial wave functions. The topological classification of these wave functions have given further insight to the nature of the FQHE.

    An early, and successful, wave function construction for filling fractions ν=p/(2p+1) was that of composite fermions on planar and spherical geometries. Recently, new developments using conformal field theory have made it possible to also construct the full Haldane-Halperin hierarchy wave functions on planar and spherical geometries. In this thesis we extend this construction to a toroidal geometry, i.e. a flat surface with periodic boundary conditions.

    One of the defining features of topological states of matter in two dimensions is that the ground state is not unique on surfaces with non trivial topology, such as a torus. The archetypical example is the fractional quantum Hall effect, where a state at filling fraction ν=p/q, has at least a q-fold degeneracy on a torus. This has been shown explicitly for a few cases, such as the Laughlin states and the the Moore-Read states, by explicit construction of candidate electron wave functions with good overlap with numerically found states. In this thesis, we construct explicit torus wave functions for a large class of experimentally important quantum liquids, namely the chiral hierarchy states in the lowest Landau level. These states, which includes the prominently observed positive Jain sequence at filling fractions ν=p/(2p+1), are characterized by having boundary modes with only one chirality.

    Our construction relies heavily on previous work that expressed the hierarchy wave functions on a plane or a sphere in terms of correlation functions in a conformal field theory. This construction can be taken over to the torus when care is taken to ensure correct behaviour under the modular transformations that leave the geometry of the torus unchanged. Our construction solves the long standing problem of engineering torus wave functions for multi-component many-body states. Since the resulting expressions are rather complicated, we have carefully compared the simplest example, that of ν=2/5, with numerically found wave functions. We have found an extremely good overlap for arbitrary values of the modular parameter τ, that describes the geometry of the torus.

    Having explicit torus wave functions allows us to use the methods developed by Read and Read \& Rezayi to numerically compute the quantum Hall viscosity. Hall viscosity is conjectured to be a topologically protected macroscopic transport coefficient characterizing the quantum Hall state. It is related to the shift of the same QH-fluid when it is put on a sphere. The good agreement with the theoretical prediction for the 2/5 state strongly suggests that our wave functions encodes all relevant topologically information.

    We also consider the Hall viscosity in the limit of a very thin torus. There we find that the viscosity changes as we approach the thin torus limit. Because of this we study the Laughlin state in that limit and see how the change in viscosity arises from a change in the Hamiltonian hopping elements. Finally we conclude that there are both qualitative and quantitative difference between the thin and the square torus. Thus, one has to be careful when interpreting results in the thin torus limit.

  • 28787.
    Fremling, Mikael
    Stockholm University, Faculty of Science, Department of Physics. National University of Ireland, Ireland.
    Success and failure of the plasma analogy for Laughlin states on a torus2017In: Journal of Physics A: Mathematical and Theoretical, ISSN 1751-8113, E-ISSN 1751-8121, Vol. 50, no 1, article id 015201Article in journal (Refereed)
    Abstract [en]

    We investigate the nature of the plasma analogy for the Laughlin wave function on a torus describing the quantum Hall plateau at nu = 1/q. We first establish, as expected, that the plasma is screening if there are no short nontrivial paths around the torus. We also find that when one of the handles has a short circumference-i.e. the thin-torus limit-the plasma no longer screens. To quantify this we compute the normalization of the Laughlin state, both numerically and analytically. In the thin torus limit, the analytical form of the normalization simplify and we can reconstruct the normalization and analytically extend it back into the 2D regime. We find that there are geometry dependent corrections to the normalization, and this in turn implies that the plasma in the plasma analogy is not screening when in the thin torus limit. Despite the breaking of the plasma analogy in this limit, the analytical approximation is still a good description of the normalization for all tori, and also allows us to compute hall viscosity at intermediate thickness.

  • 28788.
    Fremling, Mikael
    et al.
    Stockholm University, Faculty of Science, Department of Physics. National University of Ireland, Ireland.
    Fulsebakke, J.
    Moran, N.
    Slingerland, J. K.
    Energy projection and modified Laughlin states2016In: Physical Review B, ISSN 2469-9950, Vol. 93, no 23, article id 235149Article in journal (Refereed)
    Abstract [en]

    We develop a method to efficiently calculate trial wave functions for quantum Hall systems which involve projection onto the lowest Landau level. The method essentially replaces the lowest Landau level projection by projection onto the M lowest eigenstates of a suitably chosen Hamiltonian acting within the lowest Landau level. The resulting energy projection is a controlled approximation to the exact lowest Landau level projection which improves with increasing M. It allows us to study the projected trial wave functions for system sizes close to the maximal sizes that can be reached by exact diagonalization and can be straightforwardly applied in any geometry. As a first application and test case, we study a class of trial wave functions first proposed by Girvin and Jach [Girvin and Jach, Phys. Rev. B 29, 5617 (1984)], which are modifications of the Laughlin states involving a single real parameter. While these modified Laughlin states probably represent the same universality class exemplified by the Laughlin wave functions, we show by extensive numerical work for systems on the sphere and torus that they provide a significant improvement of the variational energy, overlap with the exact wave function and properties of the entanglement spectrum.

  • 28789.
    Fremling, Mikael
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Hansson, Thors Hans
    Stockholm University, Faculty of Science, Department of Physics.
    Suorsa, Juha
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Hall viscosity of hierarchical quantum Hall states2014In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 89, no 12, article id 125303Article in journal (Refereed)
    Abstract [en]

    Using methods based on conformal field theory, we construct model wave functions on a torus with arbitrary flat metric for all chiral states in the abelian quantum Hall hierarchy. These functions have no variational parameters, and they transform under the modular group in the same way as the multicomponent generalizations of the Laughlin wave functions. Assuming the absence of Berry phases upon adiabatic variations of the modular parameter tau, we calculate the quantum Hall viscosity and find it to be in agreement with the formula, given by Read, which relates the viscosity to the average orbital spin of the electrons. For the filling factor nu = 2/5 Jain state, which is at the second level in the hierarchy, we compare our model wave function with the numerically obtained ground state of the Coulomb interaction Hamiltonian in the lowest Landau level, and find very good agreement in a large region of the complex t plane. For the same example, we also numerically compute the Hall viscosity and find good agreement with the analytical result for both the model wave function and the numerically obtained Coulomb wave function. We argue that this supports the notion of a generalized plasma analogy that would ensure that wave functions obtained using the conformal field theory methods do not acquire Berry phases upon adiabatic evolution.

  • 28790. Fremont, Vincent
    et al.
    Jonathan, Gideon Mekonnen
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences.
    Can Blockchain Technology Solve Trust Issues in Industrial Networks?2018In: BIR Short Papers, Workshops and Doctoral Consortium: Proceedings / [ed] Jelena Zdravkovic, Jānis Grabis, Selmin Nurcan, Janis Stirna, CEUR-WS.org , 2018, p. 399-404, article id 40Conference paper (Refereed)
    Abstract [en]

    Since its inception about a decade ago, practitioners and researchers alike have been drawn to the blockchain technology vibe. Advocates of blockchain argue that the technology is taking us to truly ‘trust-free’ transactions. A long list of applications of blockchain has also been proposed in a relatively short period of time. However, a closer look into the literature reveals two shortcomings. To start with, the substantial proportion of the research on blockchain has focused on addressing the technical aspects of blockchain—design and features— as well as legal issues. However, there is a lack of knowledge on how blockchain technology can be used to solve practical problems faced by organizations in different sectors and industries—measurement and value, trust, management and organization. The state-of-the-art also shows that there is a dominance of conceptual and design-oriented research paradigms. To address this gap and respond to the calls for further research, this paper presents a research plan for a longitudinal case study to investigate whether blockchain technology can affect the way organizations conduct their business relationships.

  • 28791.
    Frenkel, Jacob A.
    et al.
    University of Chicago.
    Razin, Assaf
    Department of Economics, Tel Aviv University.
    Aspects of Dual Exchange-Rate Regimes1985Report (Other academic)
  • 28792.
    Frennesson, Felicia
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Sociology.
    Karim, Noor
    Stockholm University, Faculty of Social Sciences, Department of Sociology.
    Berusad i Europa: En kvantitativ studie om européers alkoholvanor2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Alkohol är en källa till glädje men är också orsaken till många människors lidande och död. Värst drabbade är de som redan är missgynnade i samhället och den världsdel där alkohol konsumeras som mest är Europa. Alkoholen är integrerad i det sociala livet människor emellan och är något som är förknippat med mat och fest. Människor påverkas av de sociala nätverk som de befinner sig i, där vanor överförs och anammas. Därför är det viktigt i studiet av alkoholvanor att inkludera indikatorer på sociala faktorer. Syftet med studien var att undersöka alkoholvanor i relation till socioekonomisk status och kön. Tidigare forskning om alkoholvanor i Europa bildar en bas för en ökad förståelse för hur alkohol konsumeras i de olika regionerna och länderna. Trots skillnader mellan länder avseende alkoholkonsumtion så finns det fortfarande landspecifika mönster som denna studie ämnar undersöka. Dessa mönster omfattar frekvens, intensivkonsumtion och riskfyllt drickande.

    Datamaterialet som använts är från omgång 7 av European Social Survey, ESS, år 2014. Data för studien omfattar 37 623 respondenter från 20 europeiska länder. För att mäta socioekonomisk status användes utbildningsnivå och föräldrars utbildningsnivå. Alkoholvanor mättes med frekvens, intensivkonsumtion och riskfyllt drickande genom AUDIT-C.

    För att analysera samband mellan socioekonomisk status och alkoholvanor användes bivariat analys samt linjära regressionsanalyser. Resultaten visar att lågutbildade dels konsumerar alkohol mest frekvent och intensivkonsumerar i större utsträckning än högutbildade och att män i högre grad än kvinnor har riskfyllda alkoholvanor. Alkoholvanorna skiljde sig mellan olika europeiska regioner, vilket stöds av resultat från tidigare forskning.

    Sammanfattningsvis visar studien att sociala faktorer har betydelse för alkoholvanor och är något som bör beaktas i framtida forskning. Studien visar även att det fortfarande finns regionala skillnader i Europa gällande alkoholvanor.

  • 28793.
    Frenning, Linda
    Stockholm University. Stockholm University, Faculty of Social Sciences, Department of Education.
    Vad gör skolrummet med oss som lärande subjekt?: En studie kring minnen av klassrumsmiljöer och elevers subjektskapande2010Independent thesis Advanced level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Jag har i den här uppsatsen undersökt hur själva klassrummet som både materiellt och diskursivt rum är delaktigt i den subjektsskapande processen. I detta har jag använt mig av olika inspirationskällor. Dels har jag inspirerats av fysikern Karen Barards onto-epistemoligiska teori i vilken det materiella tillskrivs en påverkansmöjlighet i hur vi förstår oss själva och vad som händer med oss och dels Gilles Deleuze idéer kring flöden och tillblivelser för att försöka förstå hur ett klassrum kan skapa olika möjligheter och begränsningar. Dessutom har jag använt Michel Foucaults tankar om hur rummet kan förstås som en diskursiv kontrollmekanism, tankar som han utvecklat i texten ”Fogliga kroppar”. Min undersökning har även en poststrukturalistiskt feministisk utgångspunkt. Metodologiskt använder jag mig av det som brukar benämnas ”kollektivt minnesarbete”. Detta innebär att jag har använt mig av mina egna och en annan lärares nedtecknade minnen för att undersöka den subjektskapande processen. Jag har prövat hur det går att förstå klassrummets utformning, bänkarnas placering, stolarnas tilltal, svarta tavlans roll, papper och färger som används med mera i formandet av oss som subjekt. Min ambition är att, genom att tillämpa olika teorier, skapa andra, olika och nya sätt att betrakta det pedagogiska rummet. Detta innebär en strävan bort från en subjektssyn som menar att vi formas som lärande subjekt enbart diskursivt, oavsett materialitet. Istället vill jag försöka förstå den roll det fysiska klassrummet och dess material spelar i denna process.

  • 28794.
    Frenning, Peter
    Stockholm University, Faculty of Social Sciences, School of Business.
    Real Estate Investment Trust (REITs) - ett bra diversifieringsalternativ?2005Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Jag har i min studie undersökt huruvida amerikanska REITs är ett bra alternativ för investerare som önskar diversifiera sin portfölj. Jag har även studerat hur mycket REITs avkastning präglas av aktiemarknaden i allmänhet respektive av fastighetsmarknaden i synnerlighet

  • 28795.
    Fresk, Henrik
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Sociology.
    Övelius, Martin
    Stockholm University, Faculty of Social Sciences, Department of Sociology.
    Folkhälsa i förändring: En komparativ studie av hälsoutvecklingen i de postkommunistiska staterna Tjeckien, Polen, Estland och Ryssland2005Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Denna uppsats avser att utreda om och i så fall varför folkhälsan i de postkommunistiska staterna Ryssland, Polen, Tjeckien och Estland har utvecklats olika sedan Sovjetunionens sammanbrott. Huvudsyftet med uppsatsen är att undersöka och förklara skillnaden i hälsoläget efter den så kallade rubelkrisen 1998. Skillnader i hälsoutveckling ställs mot å ena sidan ekonomiska - och å andra sidan sociala faktorer. Tänkbara samband mellan bland annat förväntad livslängd och bruttonationalprodukten (BNP) per capita samt inkomstfördelning prövas. Dödlighet och förväntad livslängd undersöks i respektive land för perioden 1989-2002. Mortalitetens eventuella samband med sjukdomen levercirros samt alkoholkonsumtion över samma tidsperiod analyseras. Datamaterialet är sekundärdata och en kvantitativ komparativ metod används för analysen. Data är konstruerad främst som medelvärden för ett specifikt årtal för respektive land. Materialet består således av ett populationsurval.

    Två olika teoretiska utgångspunkter gör anspråk på att försöka förklara problematiken med transformationen från kommunism till demokrati. Det är den nyliberala - samt den mer socialorienterade ekonomiska teorin. Dessa ställs mot varandra i början av denna uppsats. Tidigare forskningsresultat tyder på en kraftig försämring av folkhälsan efter 1989 i främst Ryssland och Estland medan Tjeckien och Polen uppvisat en positiv hälsoutveckling. Våra resultat visar att det troligtvis är sociala och psykosociala faktorer, såsom hur en familje- och arbetssituation exempelvis kan påverka en persons hälsotillstånd, som verkar vara avgörande för förståelsen av ökad ohälsa. Analysen visar vidare att en ojämn ekonomisk fördelningspolitik tillsammans med en svag institutionell infrastruktur har en stark inverkan på ovannämnda faktorer. Ryssland presenterar ett avvikande resultat i jämförelse med de tre övriga länderna för flertalet av undersökta variabler. Vi har funnit att Tjeckien och Polen står för den mest hoppingivande förändringen beträffande dödlighet och förväntad livslängd. Estland har dragits med svårigheter att komma tillrätta med landets hälsoproblematik, men har under senare år uppvisat mer positiva siffror. Ryssland representerar däremot fortsatt negativ hälsoutveckling trots en liknande ekonomisk tillväxt. Att landet så sent som år 2002 redovisar en mycket hög dödlighetsfrekvens och låg förväntad livslängd ser vi som anmärkningsvärt. Skillnader i dödlighet och förväntad livslängd mellan könen och mellan de olika länderna visade sig vara mycket stora. Det bör noteras att denna uppsats endast är inriktad på att belysa den skillnad i förväntad livslängd och dödlighet som uppkommit sedan sammanbrottet 1989 fram till 2002.

  • 28796. Fretwell, P.
    et al.
    Pritchard, H. D.
    Vaughan, D. G.
    Bamber, J. L.
    Barrand, N. E.
    Bell, R.
    Bianchi, C.
    Bingham, R. G.
    Blankenship, D. D.
    Casassa, G.
    Catania, G.
    Callens, D.
    Conway, H.
    Cook, A. J.
    Corr, H. F. J.
    Damaske, D.
    Damm, V.
    Ferraccioli, F.
    Forsberg, R.
    Fujita, S.
    Gim, Y.
    Gogineni, P.
    Griggs, J. A.
    Hindmarsh, R. C. A.
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Holt, J. W.
    Jacobel, R. W.
    Jenkins, A.
    Jokat, W.
    Jordan, T.
    King, E. C.
    Kohler, J.
    Krabill, W.
    Riger-Kusk, M.
    Langley, K. A.
    Leitchenkov, G.
    Leuschen, C.
    Luyendyk, B. P.
    Matsuoka, K.
    Mouginot, J.
    Nitsche, F. O.
    Nogi, Y.
    Nost, O. A.
    Popov, S. V.
    Rignot, E.
    Rippin, D. M.
    Rivera, A.
    Roberts, J.
    Ross, N.
    Siegert, M. J.
    Smith, A. M.
    Steinhage, D.
    Studinger, M.
    Sun, B.
    Tinto, B. K.
    Welch, B. C.
    Wilson, D.
    Young, D. A.
    Xiangbin, C.
    Zirizzotti, A.
    Bedmap2: improved ice bed, surface and thickness datasets for Antarctica2013In: The Cryosphere, ISSN 1994-0416, E-ISSN 1994-0424, Vol. 7, no 1, p. 375-393Article in journal (Refereed)
    Abstract [en]

    We present Bedmap2, a new suite of gridded products describing surface elevation, ice-thickness and the seafloor and subglacial bed elevation of the Antarctic south of 60 degrees S. We derived these products using data from a variety of sources, including many substantial surveys completed since the original Bedmap compilation (Bedmap1) in 2001. In particular, the Bedmap2 ice thickness grid is made from 25 million measurements, over two orders of magnitude more than were used in Bedmap1. In most parts of Antarctica the subglacial landscape is visible in much greater detail than was previously available and the improved data-coverage has in many areas revealed the full scale of mountain ranges, valleys, basins and troughs, only fragments of which were previously indicated in local surveys. The derived statistics for Bedmap2 show that the volume of ice contained in the Antarctic ice sheet (27 million km(3)) and its potential contribution to sea-level rise (58 m) are similar to those of Bedmap1, but the mean thickness of the ice sheet is 4.6% greater, the mean depth of the bed beneath the grounded ice sheet is 72m lower and the area of ice sheet grounded on bed below sea level is increased by 10 %. The Bedmap2 compilation highlights several areas beneath the ice sheet where the bed elevation is substantially lower than the deepest bed indicated by Bedmap1. These products, along with grids of data coverage and uncertainty, provide new opportunities for detailed modelling of the past and future evolution of the Antarctic ice sheets.

  • 28797.
    Freud, E.
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Rosenfeld, D.
    Andreae, M. O.
    Costa, A. A.
    Artaxo, P.
    Robust relations between CCN and the vertical evolution of cloud drop size distribution in deep convective clouds2008In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 8, no 6, p. 1661-1675Article in journal (Refereed)
    Abstract [en]

    In-situ measurements in convective clouds (up to the freezing level) over the Amazon basin show that smoke from deforestation fires prevents clouds from precipitating until they acquire a vertical development of at least 4 km, compared to only 1-2 km in clean clouds. The average cloud depth required for the onset of warm rain increased by similar to 350 m for each additional 100 cloud condensation nuclei per cm(3) at a super-saturation of 0.5% (CCN0.5%). In polluted clouds, the diameter of modal liquid water content grows much slower with cloud depth (at least by a factor of similar to 2), due to the large number of droplets that compete for available water and to the suppressed coalescence processes. Contrary to what other studies have suggested, we did not observe this effect to reach saturation at 3000 or more accumulation mode particles per cm(3). The CCN0.5% concentration was found to be a very good predictor for the cloud depth required for the onset of warm precipitation and other microphysical factors, leaving only a secondary role for the updraft velocities in determining the cloud drop size distributions. The effective radius of the cloud droplets (r(e)) was found to be a quite robust parameter for a given environment and cloud depth, showing only a small effect of partial droplet evaporation from the cloud's mixing with its drier environment. This supports one of the basic assumptions of satellite analysis of cloud microphysical processes: the ability to look at different cloud top heights in the same region and regard their r(e) as if they had been measured inside one well developed cloud. The dependence of r(e) on the adiabatic fraction decreased higher in the clouds, especially for cleaner conditions, and disappeared at r(e)>=similar to 10 mu m. We propose that droplet coalescence, which is at its peak when warm rain is formed in the cloud at r(e)=similar to 10 mu m, continues to be significant during the cloud's mixing with the entrained air, cancelling out the decrease in r(e) due to evaporation.

  • 28798.
    Freud, E.
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Strom, J.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Rosenfeld, D.
    Tunved, Peter
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Swietlicki, E.
    Anthropogenic aerosol effects on convective cloud microphysical properties in southern Sweden2008In: Tellus. Series B, Chemical and physical meteorology, ISSN 0280-6509, E-ISSN 1600-0889, Vol. 60, no 2, p. 286-297Article in journal (Refereed)
    Abstract [en]

    In this study, we look for anthropogenic aerosol effects in southern Scandinavia's clouds under the influence of moderate levels of pollution and relatively weak dynamic forcing. This was done by comparing surface aerosol measurements with convective cloud microphysical profiles produced from satellite image analyses. The results show that the clouds associated with the anthropogenic-affected air with high PM0.5, had to acquire a vertical development of similar to 3.5 km before forming precipitation-sized particles, compared to less than 1 km for the clouds associated with low PM0.5 air-masses. Additionally, a comparison of profiles with precipitation was done with regard to different potentially important parameters. For precipitating clouds the variability of the cloud thickness needed to produce the precipitation (Delta h(14)) is directly related to PM0.5 concentrations, even without considering atmospheric stability, the specific aerosol size distribution or the aerosols' chemical composition. Each additional 1 mu g m(-3) of PM0.5 was found to increase Delta h(14) by similar to 200-250 m. Our conclusion is that it is indeed possible to detect the effects of anthropogenic aerosol on the convective clouds in southern Scandinavia despite modest aerosol masses. It also emphasizes the importance of including aerosol processes in climate-radiation models and in numerical weather prediction models.

  • 28799. Freud, E.
    et al.
    Ström, Johan
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Rosenfeld, D.
    Tunved,
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Swietlicki, E.
    Anthropogenic aerosol effects on convective cloud microphysical properties in southern Sweden2007In: Tellus BArticle in journal (Refereed)
  • 28800.
    Freud, Eyal
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Krejci, Radovan
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Tunved, Peter
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Leaitch, Richard
    Nguyen, Quynh T.
    Massling, Andreas
    Skov, Henrik
    Barrie, Leonard
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Pan-Arctic aerosol number size distributions: seasonality and transport patterns2017In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 17, no 13, p. 8101-8128Article in journal (Refereed)
    Abstract [en]

    The Arctic environment has an amplified response to global climatic change. It is sensitive to human activities that mostly take place elsewhere. For this study, a multi-year set of observed aerosol number size distributions in the diameter range of 10 to 500 nm from five sites around the Arctic Ocean (Alert, Villum Research Station - Station Nord, Zeppelin, Tiksi and Barrow) was assembled and analysed. A cluster analysis of the aerosol number size distributions revealed four distinct distributions. Together with Lagrangian air parcel back-trajectories, they were used to link the observed aerosol number size distributions with a variety of transport regimes. This analysis yields insight into aerosol dynamics, transport and removal processes, on both an intra- and an inter-monthly scale. For instance, the relative occurrence of aerosol number size distributions that indicate new particle formation (NPF) event is near zero during the dark months, increases gradually to similar to 40% from spring to summer, and then collapses in autumn. Also, the likelihood of Arctic haze aerosols is minimal in summer and peaks in April at all sites. The residence time of accumulation-mode particles in the Arctic troposphere is typically long enough to allow tracking them back to their source regions. Air flow that passes at low altitude over central Siberia and western Russia is associated with relatively high concentrations of accumulation-mode particles (N-acc) at all five sites - often above 150 cm(-3). There are also indications of air descending into the Arctic boundary layer after transport from lower latitudes. The analysis of the back-trajectories together with the meteorological fields along them indicates that the main driver of the Arctic annual cycle of N-acc, on the larger scale, is when atmospheric transport covers the source regions for these particles in the 10-day period preceding the observations in the Arctic. The scavenging of these particles by precipitation is shown to be important on a regional scale and it is most active in summer. Cloud processing is an additional factor that enhances the N-acc annual cycle. There are some consistent differences between the sites that are beyond the year-to-year variability. They are the result of differences in the proximity to the aerosol source regions and to the Arctic Ocean sea-ice edge, as well as in the exposure to free-tropospheric air and in precipitation patterns - to mention a few. Hence, for most purposes, aerosol observations from a single Arctic site cannot represent the entire Arctic region. Therefore, the results presented here are a powerful observational benchmark for evaluation of detailed climate and air chemistry modelling studies of aerosols throughout the vast Arctic region.

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