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  • 151.
    Almqvist, Nils
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Rubel, M.
    Physics Department - Frescati, Royal Institute of Technology, Association EURATOM-NFR.
    Fredriksson, Sverker
    Emmoth, B.
    Physics Department - Frescati, Royal Institute of Technology, Association EURATOM-NFR.
    Wienhold, P.
    Institute of Plasma Physics, Forschungszentrum Jülich, Association EURATOM-KFA.
    Ilyinsky, L.
    Institute of Electrical Engineering, St. Petersburg.
    AFM and STM characterization of surfaces exposed to high flux deuterium plasma1995In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 220-222, no 1-3, p. 917-921Article in journal (Refereed)
    Abstract [en]

    This paper reports the results of scanning tunneling (STM) and atomic force microscopy (AFM) studies of D+ irradiated graphite and graphite-silicon mixtures. The microscopes were used for studying surface topography and for measuring the surface roughness. The substrates were exposed at various temperatures (60 and 700°C) to different doses of deuterium ions in simulators of plasma - surface interactions and in the TEXTOR tokamak. Also nuclear reaction analysis (NRA) and Rutherford backscattering spectroscopy were applied for the qualitative and quantitative determination of surface composition. The initial stages of radiation damage, nanometer-sized bubbles/blisters, were found in plasma-eroded surfaces. These structures only appeared in the graphite phase on the multicomponent material. The microroughness of the surfaces was measured. We also used the AFM for probing the thickness of the plasma-modified layers. The results correlate with the presence of deuterium measured by NRA depth-profiling. Moreover, the AFM reveals the co-deposited layers formed on surfaces facing the tokamak plasma. The appearance of these layers is clearly correlated to the amount of co-deposited atoms.

  • 152.
    Almqvist, Nils
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Rubel, M.
    Nannetti, C.A.
    Franconi, E.
    Fredriksson, Sverker
    Emmoth, B.
    Scanning probe microscopy and thermo-mechanical characterization of silicon carbide composites1995In: Fourth Euro-Ceramics: the proceedings of the Fourth European Ceramic Society Conference / [ed] S. Meriani; V. Sergo, Gruppo Ed. Faenza Ed. , 1995, Vol. 3, p. 361-368Conference paper (Refereed)
    Abstract [en]

    series of SiC-based composites was obtained by sintering. Since such materials are considered for fusion applications, their thermal shock resistance and behaviour under deuterium irradiation are of primary interest. Extensive bulk and surface characterisation of pure and doped (AlN, TiB2, graphite) silicon carbides treated by a deuterium plasma was carried out. The change in surface structure following irradiation is addressed, and major factors influencing deuterium retention are discussed.

  • 153.
    Almqvist, Nils
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Rubel, M.
    Royal Institute of Technology, Physics Department-Frescati, Association EURATOM-NFR.
    Wienhold, P.
    Institute of Plasma Physics, Forschungszentrum Jülich, Association EURATOM-KFA.
    Fredriksson, Sverker
    Roughness determination of plasma-modified surface layers with atomic force microscopy1995In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 270, no 1-2, p. 426-430Article in journal (Refereed)
    Abstract [en]

    Graphite surfaces exposed to the deuterium plasma in the TEXTOR tokamak were characterized in detail by means of scanning probe microscopy, ion beam analysis and colorimetry methods. The aim is to study the composition and structure of thin layer deposits formed on surfaces subjected to the tokamak plasma. The surface roughness was measured and parametrized in terms of fractal dimension and scaling constant. Several different methods for the fractal analysis of plasma-exposed surfaces have been critically evaluated. The main emphasis of this paper is on the correlation between surface roughness (fractal parameters), the amount of deposited atoms and the layer thickness.

  • 154.
    Almqvist, Nils
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Thomson, Neil H.
    Smith, Bettye L.
    Stucky, Galen D.
    Morse, Daniel E.
    Hansma, Paul K.
    Methods for fabricating and characterizing a new generation of biomimetic materials1999In: Materials science & engineering. C, biomimetic materials, sensors and systems, ISSN 0928-4931, E-ISSN 1873-0191, Vol. 7, no 1, p. 37-43Article in journal (Refereed)
    Abstract [en]

    Bringing together current ideas in the fields of biomineralization and composite laminate materials, we have attempted to fabricate model materials that mimic abalone nacre through the rapid assembly of inorganic tablets, such as talc. Several physical methods were tested to aid the orientation of the talc tablets in fluid suspensions with a low percentage, 10% by dry weight, of organic binding material. The orientation of talc tablets in the synthesized composites was characterized by X-ray diffraction and scanning electron microscopy. The modulus of rupture of the materials was measured in a three-point bending test. We demonstrate that the alignment of tablets increases by the use of physical methods and from chemical surface treatment. Important factors to consider in making materials that mimic abalone nacre are discussed. Important factors to consider in making materials that mimic abalone nacre are discussed.

  • 155.
    Al-Mulla, Samir Yousif
    University of Borås, School of Engineering.
    Low-energy electron scattering from copper2006In: European Physical Journal D: Atomic, Molecular and Optical Physics, ISSN 1434-6060, E-ISSN 1434-6079, Vol. 42, no 1, p. 11-14Article in journal (Refereed)
  • 156.
    Al-Mulla, Samir Yousif
    University of Borås, School of Engineering.
    Low-Energy electron scattering from Lithium and Potassium2007Conference paper (Other academic)
  • 157.
    Alpat, B.
    et al.
    Ist Nazl Fis Nucl, Italy; Sabanci Univ, Turkey.
    Gulgun, M.A.
    Sabanci Univ, Turkey.
    Corapcioglu, G.
    Sabanci Univ, Turkey.
    Yildizhan Özyar, Melike
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Di Lazzaro, P.
    ENEA, Italy.
    Murra, D.
    ENEA, Italy.
    Kaplanoglu, T.
    Maprad Srl, Italy.
    Postolache, V
    Maprad Srl, Italy.
    Mengali, S.
    Consorzio CREO, Italy.
    Simeoni, M.
    Consorzio CREO, Italy.
    Urbani, A.
    Consorzio CREO, Italy.
    Testing of substrates for flexible optical solar reflectors: irradiations of nano-hybrid coatings of polyimide films with 20 keV electrons and with 200-400 nm ultraviolet radiation2019In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 14, article id T06003Article in journal (Refereed)
    Abstract [en]

    In the frame of a project aimed at developing a new type of optical solar reflectors we present the scientific and technological issues addressed during irradiations of nano-hybrid coatings on polyimide films by using 20 keV electron beam from a modified use of Scanning Electron Microscope (SEM) and with ultraviolet (UV) dose equal to 300 space-equivalent Sun hours. Details of a new approach to use SEM for low energy electron irradiations and of a new UV irradiation setup are given.

  • 158.
    Alves Vaccari, Paulo Roberto
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Near infrared and visible optical properties in electrochromic crystalline tungsten oxide thin films on ITO2010Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this project I have studied the optical properties of electrochromic crystalline tungsten oxide, WO3. The practical application could be for a window for desalination of sea water which requires a high absorption coefficient A(λ) for near infrared radiation (NIR), while at the same time a high transmittance T(λ) in the visible spectral range.

     

    An electrochromic (EC) material is a material that changes its optical properties when inserting or extracting ions by applying a voltage. The WO3 was prepared on a glass substrate coated by a transparent electrical conductor. The conductor used is tin doped indium oxide. In2O3:Sn, indium-tin-oxide (ITO). The preparation of the thin films has been carried out using DC magnetron reactive sputtering. The structure of unheated tungsten oxide is amorphous and once heated it is crystalline. Li+ ions were inserted into the tungsten oxide material with electrochemical methods to create the coloring effect. The optical properties were recorded in the 330 < λ < 2500 nm wavelength range by use of a Perkin-Elmer Lambda 9 spectrophotometer.

     

    The highest reflectance R(λ), approximately 50% in NIR and absorption coefficient

    A(λ) = 1,5 x 105 [cm-1], were measured for the sample that had been post annealed at 500 deg C. The crystalline tungsten oxide films provides for a good switching capability in the NIR spectral range wile at the same time maintaining a high transmittance T(λ) in the visible spectrum.

  • 159.
    Amann, Peter
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Degerman, David
    Stockholm University, Faculty of Science, Department of Physics.
    Lee, Ming-Tao
    Alexander, John D.
    Stockholm University, Faculty of Science, Department of Physics.
    Shipilin, Mikhail
    Stockholm University, Faculty of Science, Department of Physics.
    Wang, Hsin-Yi
    Stockholm University, Faculty of Science, Department of Physics.
    Cavalca, Filippo
    Weston, Matthew
    Stockholm University, Faculty of Science, Department of Physics.
    Gladh, Jörgen
    Stockholm University, Faculty of Science, Department of Physics.
    Blom, Mikael
    Stockholm University, Faculty of Science, Department of Physics.
    Björkhage, Mikael
    Stockholm University, Faculty of Science, Department of Physics.
    Löfgren, Patrik
    Stockholm University, Faculty of Science, Department of Physics.
    Schlueter, Christoph
    Drube, Wofgang
    Lömker, Patrick
    Ederer, Katrin
    Noei, Heshmat
    Zehetner, Johann
    Wentzel, Henrik
    Åhlund, John
    Nilsson, Anders
    Stockholm University, Faculty of Science, Department of Physics.
    A dedicated photoelectron spectroscopy instrument for studies of catalytic reactions at pressures exceeding 1 barManuscript (preprint) (Other academic)
    Abstract [en]

    Here, we present a new high-pressure x-ray photoelectron spectroscopy system dedicated to probing catalytic reactions under realistic conditions at pressures exceeding 1 bar. The instrument builds around the concept of a “virtual cell” in which a gasflow is directed onto the sample surface creating a local high pressure on top of the sample. This allows the instrument to maintain a low pressure of a few mbars in the main chamber, while simultaneously keeping a local pressure of around 1 bar. Synchrotron radiation based grazing incidence photoemission within ± 5° is used to enhance the surface sensitivity in the experiment. The aperture, separating the high-pressure region from the differential pumping of the electron spectrometer, consists of multiple, evenly spaced, mm sized holes matching the footprint of the x-ray beam on the sample surface. As the photo-emitted electrons are subject to strong scattering in the gas phase and the resulting signal is therefore highly dependent on the sample to aperture distance, the latter is controlled with high precision using a fully integrated manipulator that allows for sample movement with step sizes of 10 nm between 0 and –5 mm with very low vibrational amplitude. The instrumental features allows acquisition of metallic bulk spectra at He pressures up to 2.5 bar and also allows for following C1s spectra under realistic gas mixtures of CO + H2with various temperatures up to 500°C. This capability opens for studies of catalytic reactions in operandi.

  • 160. Ambrosio, M
    et al.
    Antolini, R
    Assiro, R
    Auriemma, G
    Bakari, D
    Baldini, A
    Barbarino, G C
    Barbarito, E
    Barish, B C
    Battistoni, G
    Becherini, Yvonne
    Università di Bologna.
    Bellotti, R
    Bemporad, C
    Bernardini, P
    Bilokon, H
    Bisi, V
    Bloise, C
    Bottazzi, E
    Bower, C
    Brigida, M
    Bussino, S
    Cafagna, F
    Calicchio, M
    Campana, D
    Candela, A
    Carboni, M
    Cecchini, S
    Cei, F
    Ceres, A
    Chiarella, V
    Choudhary, B C
    Coutu, S
    Cozzi, M
    Creti, P
    De Cataldo, G
    Degli Esposti, L
    Dekhissi, H
    De Marzo, C
    De Mitri, I
    Derkaoui, J
    De Vincenzi, M
    Di Credico, A
    Di Ferdinando, D
    Diotallevi, R
    Erriquez, O
    Favuzzi, C
    Forti, C
    Fusco, P
    Gebhard, M
    Giacomelli, G
    Giacomelli, R
    Giannini, G
    Giglietto, N
    Giorgini, M
    Giuliani, R
    Goretti, M
    Grassi, M
    Grau, H
    Gray, L
    Grillo, A
    Guarino, F
    Gustavino, C
    Habig, A
    Hanson, J
    Hanson, K
    Hawthorne, A
    Heinz, R
    Hong, J T
    Iarocci, E
    Katsavounidis, E
    Katsavounidis, I
    Kearns, E
    Kim, H
    Kyriazopoulou, S
    Lamanna, E
    Lane, C
    Leone, A
    Levin, D S
    Lipari, P
    Liu, G
    Liu, R
    Longley, N P
    Longo, M J
    Loparco, F
    Maaroufi, F
    Mancarella, G
    Mandrioli, G
    Manzoor, S
    Marrelli, V
    Margiotta, A
    Marini, A
    Martello, D
    Marzari-Chiesa, A
    Mazziotta, M N
    Michael, D G
    Mikheyev, S
    Miller, L
    Monacelli, P
    Mongelli, M
    Montaruli, T
    Monteno, M
    Mossbarger, L
    Mufson, S
    Musser, J
    Nicolo, D
    Nolty, R
    Okada, C
    Orsini, M
    Orth, C
    Osteria, G
    Ouchrif, M
    Palamara, O
    Parlati, S
    Patera, V
    Patrizii, L
    Pazzi, R
    Peck, C W
    Pellizzoni, G
    Perchiazzi, M
    Perrone, L
    Petrakis, J
    Petrera, S
    Pignatano, N
    Pinto, C
    Pistilli, P
    Popa, V
    Raino, A
    Reynoldson, J
    Ronga, F
    Rrhioua, A
    Sacchetti, A
    Saggese, P
    Satriano, C
    Satta, L
    Scapparone, E
    Scholberg, K
    Sciubba, A
    Serra, P
    Sioli, M
    Sirri, G
    Sitta, M
    Sondergaard, S
    Spinelli, P
    Spinetti, M
    Spurio, M
    Stalio, S
    Steinberg, R
    Stone, J L
    Sulak, L R
    Surdo, A
    Tarle, G
    Togo, V
    Vakili, M
    Valieri, C
    Walter, C W
    Webb, R
    Zaccheo, N
    The MACRO detector at Gran Sasso2002In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 486, no 3, p. 663-707Article in journal (Refereed)
    Abstract [en]

    MACRO was an experiment that ran in the Laboratori Nazionali del Gran Sasso from 1988 to 2000. Its principal goal was to observe magnetic monopoles or set significantly lower experimental flux limits than had been previously available in the velocity range from about beta = 10(-4) to unity. In addition it made a variety of other observations. Examples are: setting flux limits on other so far unobserved particles such as nuclearites and lightly ionizing particles, searching for WIMP annihilations in the Earth and the Sun and for neutrino bursts from stellar collapses in or near our Galaxy, and making measurements relevant to high energy muon and neutrino astronomy and of the flux of up-going muons as a function of nadir angle showing evidence for neutrino oscillations. The apparatus consisted of three principal types of detectors: liquid scintillator counters, limited streamer tubes, and nuclear track etch detectors. In addition, over part of its area it contained a transition radiation detector. The general design philosophy emphasized redundancy and complementarity. This paper describes the technical aspects of the complete MACRO detector, its operational performance, and the techniques used to calibrate it and verify its proper operation. It supplements a previously published paper which described the first portion of the detector that was built and operated. (C) 2002 Elsevier Science B.V. All rights reserved.

  • 161. Ambrosio, M
    et al.
    Antolini, R
    Auriemma, G
    Bakari, D
    Baldini, A
    Barbarino, G C
    Barish, B C
    Battistoni, G
    Becherini, Yvonne
    Università di Bologna .
    Bellotti, R
    Bemporad, C
    Bernardini, P
    Bilokon, H
    Bisi, V
    Bloise, C
    Bower, C
    Brigida, M
    Bussino, S
    Cafagna, F
    Calicchio, M
    Campana, D
    Carboni, M
    Caruso, R
    Cecchini, S
    Cei, F
    Chiarella, V
    Choudhary, B C
    Coutu, S
    De Cataldo, G
    Dekhissi, H
    De Marzo, C
    De Mitri, I
    Derkaoui, J
    De Vincenzi, M
    Di Credico, A
    Erriquez, O
    Favuzzi, C
    Forti, C
    Fusco, P
    Giacomelli, G
    Giannini, G
    Giglietto, N
    Giorgini, M
    Grassi, M
    Gray, L
    Grillo, A
    Guarino, F
    Gustavino, C
    Habig, A
    Hanson, K
    Heinz, R
    Iarocci, E
    Katsavounidis, E
    Katsavounidis, I
    Kearns, E
    Kim, H
    Kyriazopoulou, S
    Lamanna, E
    Lane, C
    Levin, D S
    Lipari, P
    Longley, N P
    Longo, M J
    Loparco, F
    Maaroufi, F
    Mancarella, G
    Mandrioli, G
    Margiotta, A
    Marini, A
    Martello, D
    Marzari-Chiesa, A
    Mazziotta, M N
    Michael, D G
    Mikheyev, S
    Miller, L
    Monacelli, P
    Montaruli, T
    Monteno, M
    Mufson, S
    Musser, J
    Nicolo, D
    Nolty, R
    Orth, C
    Osteria, G
    Palamara, O
    Patera, V
    Patrizii, L
    Pazzi, R
    Peck, C W
    Perrone, L
    Petrera, S
    Pistilli, P
    Popa, V
    Raino, A
    Reynoldson, J
    Ronga, F
    Rrhioua, A
    Satriano, C
    Scapparone, E
    Scholberg, K
    Sciubba, A
    Serra, P
    Sioli, M
    Sirri, G
    Sitta, M
    Spinelli, P
    Spinetti, M
    Spurio, M
    Steinberg, R
    Stone, J L
    Sulak, L R
    Surdo, A
    Tarle, G
    Togo, V
    Vakili, M
    Walter, C W
    Webb, R
    Matter effects in upward-going muons and sterile neutrino oscillations2001In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 517, no 1-2, p. 59-66Article in journal (Refereed)
    Abstract [en]

    The angular distribution of upward-going muons produced by atmospheric neutrinos in the rock below the MACRO detector shows anomalies in good agreement with two flavor nu (mu) --> nu (tau) oscillations with maximum mixing and Deltam(2) around 0.0024 eV(2). Exploiting the dependence of magnitude of the matter effect on oscillation channel, and using a set of 809 upward-going muons observed in MACRO, we show that the two flavor nu (mu) --> nu (s) oscillation is disfavored with 99% C.L. with respect to nu (mu) --> nu (tau). (C) 2001 Elsevier Science B.V. All rights reserved.

  • 162. Ambrosio, M
    et al.
    Antolini, R
    Auriemma, G
    Bakari, D
    Baldini, A
    Barbarino, G C
    Barish, B C
    Battistoni, G
    Becherini, Yvonne
    Università di Bologna .
    Bellotti, R
    Bemporad, C
    Bernardini, P
    Bilokon, H
    Bloise, C
    Bower, C
    Brigida, M
    Bussino, S
    Cafagna, F
    Calicchio, M
    Campana, D
    Candela, A
    Carboni, M
    Caruso, R
    Cassese, F
    Cecchini, S
    Cei, F
    Chiarella, V
    Choudhary, B C
    Coutu, S
    Cozzi, M
    De Cataldo, G
    De Deo, M
    Dekhissi, H
    De Marzo, C
    De Mitri, I
    Derkaoui, J
    De Vincenzi, M
    Di Credico, A
    Dincecco, M
    Erriquez, O
    Favuzzi, C
    Forti, C
    Fusco, P
    Giacomelli, G
    Giannini, G
    Giglietto, N
    Giorgini, M
    Grassi, M
    Gray, L
    Grillo, A
    Guarino, F
    Gustavino, C
    Habig, A
    Hanson, K
    Heinz, R
    Iarocci, E
    Katsavounidis, E
    Katsavounidis, I
    Kearns, E
    Kim, H
    Kyriazopoulou, S
    Lamanna, E
    Lane, C P
    Levin, D S
    Lindozzi, M
    Lipari, P
    Longley, N P
    Longo, M J
    Loparco, F
    Marroufi, F
    Mancarella, G
    Mandrioli, G
    Margiotta, A
    Marini, A
    Martello, D
    Marzari-Chiesa, A
    Mazziotta, M N
    Michael, D G
    Monacelli, P
    Montaruli, T
    Monteno, M
    Mufson, S
    Musser, J
    Nicolo, D
    Nolty, R
    Orth, C
    Osteria, G
    Palamara, O
    Patera, V
    Patrizii, L
    Pazzi, R
    Peck, C W
    Perrone, L
    Petrera, S
    Pistilli, P
    Popa, V
    Raino, A
    Reynoldson, J
    Ronga, F
    Rrhioua, A
    Satriano, C
    Scapparone, E
    Scholberg, K
    Sciubba, A
    Serra, P
    Sioli, M
    Sirri, G
    Sitta, M
    Spinelli, P
    Spinetti, M
    Spurio, M
    Steinberg, R
    Stone, J L
    Sulak, L R
    Surdo, A
    Tarle, G
    Tatananni, E
    Togo, V
    Vakili, M
    Walter, C W
    Webb, R
    Muon energy estimate through multiple scattering with the MACRO detector2002In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 492, no 3, p. 376-386Article in journal (Refereed)
    Abstract [en]

    Muon energy measurement represents an important issue for any experiment addressing neutrino-induced up-going muon studies. Since the neutrino oscillation probability depends on the neutrino energy, a measurement of the muon energy adds an important piece of information concerning the neutrino system. We show in this paper how the MACRO limited streamer tube system can be operated in drift mode by using the TDCs included in the QTPs, an electronics designed for magnetic monopole search. An improvement of the space resolution is obtained, through an analysis of the multiple scattering of muon tracks as they pass through our detector. This information can be used further to obtain an estimate of the energy of muons crossing the detector. Here we present the results of two dedicated tests, performed at CERN PS-T9 and SPS-X7 beam lines, to provide a full check of the electronics and to exploit the feasibility of such a multiple scattering analysis. We show that by using a neural network approach, we are able to reconstruct the muon energy for E-mu < 40 GeV. The test beam data provide an absolute energy calibration, which allows us to apply this method to MACRO data. (C) 2002 Elsevier Science B.V. All rights reserved.

  • 163. Ambrosio, M
    et al.
    Antolini, R
    Bakari, D
    Baldini, A
    Barbarino, G C
    Barish, B C
    Battistoni, G
    Becherini, Yvonne
    Università di Bologna.
    Bellotti, R
    Bemporad, C
    Bernardini, P
    Bilokon, H
    Bloise, C
    Bower, C
    Brigida, M
    Bussino, S
    Cafagna, E
    Calicchio, M
    Campana, D
    Carboni, M
    Caruso, R
    Cecchini, S
    Cei, F
    Chiarella, V
    Chiarusi, T
    Choudhary, B C
    Coutu, S
    Cozzi, M
    De Cataldo, G
    Dekhissi, H
    De Marzo, C
    De Mitri, I
    Derkaoui, J
    De Vincenzi, M
    Di Credico, A
    Favuzzi, C
    Forti, C
    Fusco, P
    Giacomelli, G
    Giannini, G
    Giglietto, N
    Giorgini, M
    Grassi, M
    Grillo, A
    Gustavino, C
    Habig, A
    Hanson, K
    Heinz, R
    Iarocci, E
    Katsavounidis, E
    Katsavounidis, I
    Kearns, E
    Kim, H
    Kumar, A
    Kyriazopoulou, S
    Lamanna, E
    Lane, C
    Levin, D S
    Lipari, P
    Longo, M J
    Loparco, F
    Maaroufi, F
    Mancarella, G
    Mandrioli, G
    Manzoor, S
    Margiotta, A
    Marini, A
    Martello, D
    Marzari-Chiesa, A
    Mazziotta, M N
    Michael, D G
    Mikheyev, S
    Monacelli, P
    Montaruli, T
    Monteno, M
    Mufson, S
    Musser, J
    Nicolo, D
    Nolty, R
    Orth, C
    Osteria, G
    Palamara, O
    Patera, V
    Patrizii, L
    Pazzi, R
    Peck, C W
    Perrone, L
    Petrera, S
    Popa, V
    Raino, A
    Reynoldson, J
    Ronga, F
    Rrhioua, A
    Satriano, C
    Scapparone, E
    Scholberg, K
    Sciubba, A
    Serra, P
    Sioli, M
    Sirri, G
    Sitta, M
    Spinelli, P
    Spinetti, M
    Spurio, M
    Steinberg, R
    Stone, J L
    Sulak, L R
    Surdo, A
    Tarle, G
    Togo, V
    Vakili, M
    Walter, C W
    Webb, R
    Atmospheric neutrino oscillations from upward throughgoing muon multiple scattering in MACRO2003In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 566, no 1-2, p. 35-44Article in journal (Refereed)
    Abstract [en]

    The energy of atmospheric neutrinos detected by MACRO was estimated using multiple Coulomb scattering of upward throughgoing muons. This analysis allows a test of atmospheric neutrino oscillations, relying on the distortion of the muon energy distribution. These results have been combined with those coming from the upward throughgoing muon angular distribution only. Both analyses are independent of the neutrino flux normalization and provide strong evidence, above the for level, in favour of neutrino oscillations. (C) 2003 Published by Elsevier B.V.

  • 164. Ambrosio, M
    et al.
    Antolini, R
    Bakari, D
    Baldini, A
    Barbarino, G C
    Barish, B C
    Battistoni, G
    Becherini, Yvonne
    Università di Bologna.
    Bellotti, R
    Bemporad, C
    Bernardini, P
    Bilokon, H
    Bloise, C
    Bower, C
    Brigida, M
    Cafagna, F
    Campana, D
    Carboni, M
    Cecchini, S
    Cei, F
    Chiarella, V
    Choudhary, B C
    Cosson, D
    Coutu, S
    De Cataldo, G
    Dekhissi, H
    De Marzo, C
    De Mitri, I
    Denni, U
    Derkauoi, J
    De Vincenzi, M
    Di Credico, A
    Favuzzi, C
    Forti, C
    Frani, A
    Fusco, P
    Giacomelli, G
    Giannini, G
    Giglietto, N
    Giorgini, M
    Grassi, M
    Grillo, A
    Guarino, F
    Gustavino, C
    Habig, A
    Hanson, K
    Heinz, R
    Iarocci, E
    Katsavounidis, E
    Katsavounidis, I
    Kearns, E
    Kim, H
    Kyriazopoulou, S
    Lamanna, E
    Lane, C
    Levin, D S
    Lipari, P
    Longo, M J
    Loparco, F
    Maaroufi, F
    Mancarella, G
    Mandrioli, G
    Manzoor, S
    Margiotta, A
    Marini, A
    Martello, D
    Marzari-Chiesa, A
    Mazziotta, M N
    Mengucci, A
    Michael, D G
    Mikheyev, S
    Monacelli, P
    Montaruli, T
    Monteno, M
    Mufson, S
    Musser, J
    Nicolo, D
    Nolty, R
    Orth, C
    Osteria, G
    Palamara, O
    Patera, V
    Patrizii, L
    Pazzi, R
    Peck, C W
    Perrone, L
    Petrera, S
    Popa, V
    Raino, A
    Reynoldson, J
    Ronga, F
    Satriano, C
    Scholberg, K
    Sciubba, A
    Sioli, M
    Sitta, M
    Spinelli, P
    Spinetti, M
    Spurio, M
    Steinberg, R
    Stone, J L
    Sulak, L R
    Surdo, A
    Tarle, G
    Togo, V
    Vakili, M
    Walter, C W
    Webb, R
    Measurements of atmospheric muon neutrino oscillations, global analysis of the data collected with MACRO detector2004In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 36, no 3, p. 323-339Article in journal (Refereed)
    Abstract [en]

    The final analysis of atmospheric neutrino events collected with the MACRO detector is presented. Three different classes of events, generated by neutrinos in different energy ranges, are studied looking at rates, angular distributions and estimated energies. The results are consistent for all the subsamples and indicate a flux deficit that depends on energy and path - length of neutrinos. The no - oscillation hypothesis is excluded at similar to 5sigma, while the hypothesis of nu(mu) --> nu(tau) oscillation gives a satisfactory description of all data. The parameters with highest probability in a two flavor scenario are sin(2) 2theta(m) = 1 and Deltam(2) = 0.0023 eV(2). This result is independent of the absolute normalization of the atmospheric neutrino fluxes. The data can also be used to put experimental constrain on this normalization.

  • 165.
    Amin, Sidra
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. National Centre of Excellence in Analytical Chemistry, University of Sindh, Jamshoro, Pakistan.Department of Chemistry, Shaheed Benazir Bhutto University, Shaheed Benazirabad, Pakistan.
    Tahira, Aneela
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Solangi, Amber
    National Centre of Excellence in Analytical Chemistry, University of Sindh, Jamshoro, Pakistan.
    Beni, Valerio
    RISE Acreo, Research Institute of Sweden, Norrköping, Sweden.
    Morante, J.R
    Catalonia Institute for Energy Research (IREC), Barcelona, Spain.
    Liu, Xianjie
    Department of Physics, Chemistry and Biology, Surface Physics and Chemistry, Linköping University, Faculty of Science & Engineering, Sweden.
    Falhman, Mats
    Department of Physics, Chemistry and Biology, Surface Physics and Chemistry, Linköping University, Faculty of Science & Engineering, Sweden.
    Mazzaro, Raffaello
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Ibupoto, Zafar
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Institute of Chemistry, University of Sindh, Jamshoro, Pakistan.
    Vomiero, Alberto
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    A practical non-enzymatic urea sensor based on NiCo2O4 nanoneedles2019In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 9, no 25, p. 14443-14451Article in journal (Refereed)
    Abstract [en]

    We propose a new facile electrochemical sensing platform for determination of urea, based on a glassy carbon electrode (GCE) modified with nickel cobalt oxide (NiCo2O4) nanoneedles. These nanoneedles are used for the first time for highly sensitive determination of urea with the lowest detection limit (1 μM) ever reported for the non-enzymatic approach. The nanoneedles were grown through a simple and low-temperature aqueous chemical method. We characterized the structural and morphological properties of the NiCo2O4 nanoneedles by TEM, SEM, XPS and XRD. The bimetallic nickel cobalt oxide exhibits nanoneedle morphology, which results from the self-assembly of nanoparticles. The NiCo2O4 nanoneedles are exclusively composed of Ni, Co, and O and exhibit a cubic crystalline phase. Cyclic voltammetry was used to study the enhanced electrochemical properties of a NiCo2O4 nanoneedle-modified GCE by overcoming the typical poor conductivity of bare NiO and Co3O4. The GCE-modified electrode is highly sensitive towards urea, with a linear response (R2 = 0.99) over the concentration range 0.01–5 mM and with a detection limit of 1.0 μM. The proposed non-enzymatic urea sensor is highly selective even in the presence of common interferents such as glucose, uric acid, and ascorbic acid. This new urea sensor has good viability for urea analysis in urine samples and can represent a significant advancement in the field, owing to the simple and cost-effective fabrication of electrodes, which can be used as a promising analytical tool for urea estimation.

  • 166.
    Amin, Sidra
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. National Centre of Excellence in Analytical Chemistry, University of Sindh, Jamshoro, Pakistan. Department of Chemistry, Shaheed Benazir Bhutto University, Shaheed Benazirabad, Pakistan.
    Tahira, Aneela
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Solangi, Amber
    National Centre of Excellence in Analytical Chemistry, University of Sindh, Jamshoro, Pakistan.
    Mazzaro, Raffaello
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Ibupoto, Zafar
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Department of Chemistry, Shaheed Benazir Bhutto University, Shaheed Benazirabad, Pakistan.
    Vomiero, Alberto
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    A sensitive enzyme-free lactic acid sensor based on NiO nanoparticles for practical applications2019In: Analytical Methods, ISSN 1759-9660, E-ISSN 1759-9679, Vol. 11, p. 3578-3583Article in journal (Refereed)
    Abstract [en]

    A facile and efficient electrochemical sensing platform has been successfully exploited for the first time for the determination of lactic acid using a nickel oxide (NiO) nanoparticle-modified glassy carbon electrode (GCE). Nickel oxide nanoparticles were prepared by a chemical growth method using different quantities of arginine as a soft template. The structural and morphological properties of NiO nanoparticles were characterized by Raman spectroscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD). Cyclic voltammetry (CV) was used to study the electrochemical properties of various samples. The modified electrode is highly sensitive and presents a linear response over a wide range (0.005–5 mM) of lactic acid concentrations in 0.1 M NaOH. The detection limit for the sensor was found to be 5.7 μM, and it exhibits good stability. Furthermore, the sensor shows excellent selectivity in the presence of common interfering species. The lactic acid sensor showed good viability for lactic acid analysis in real samples (milk, yogurt and red wine) and demonstrated significant advancement in sensor technology for practical applications.

  • 167.
    Anand, Srinivasan
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Semiconductor Materials, HMA (Closed 20120101).
    Shahid, Naeem
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Semiconductor Materials, HMA (Closed 20120101).
    Naureen, Shagufta
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Semiconductor Materials, HMA (Closed 20120101).
    Li, Mingyu
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Semiconductor Materials, HMA (Closed 20120101). Zhejiang University, Hangzhou, China.
    Swillo, Marcin
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Semiconductor Materials, HMA (Closed 20120101).
    InP-based photonic crystal waveguide filters2010In: 2010 Asia Communications and Photonics Conference and Exhibition, ACP 2010, 2010, p. 104-105Conference paper (Refereed)
  • 168.
    Anderson, D.
    et al.
    Chalmers University of Technology.
    Desaix, Mats
    University of Borås, Faculty of Textiles, Engineering and Business.
    Nyqvist, R.
    Chalmers University of Technology.
    The least uncomfortable journey from A to B2016In: American Journal of Physics, ISSN 0002-9505, E-ISSN 1943-2909, Vol. 84, no 9, p. 690-695Article in journal (Refereed)
    Abstract [en]

    A short introduction is given about direct variational methods and their relation to Galerkin and moment methods, all flexible and powerful approaches for finding approximate solutions to difficult physicalequations. An application of these methods is given in the form of the variational problem of minimizing the discomfort experienced during different journeys, between two fixed horizontal points while keeping the travel time constant. The analysis is shown to provide simple, yet accurate, approximate solutions of the problem and illustrates the usefulness and the power of direct variational and moment methods. It also demonstrates the problem of a priori assessing the accuracy of the approximate solutions and illustrates that the variational solution does not necessarily provide a more accurate solution than that obtained by moment methods.

  • 169. Anderson, Louise
    et al.
    Zarembo, Konstantin
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA. Stockholm University, Stockholm, Sweden; Uppsala University, Uppsala, Sweden; ITEPMoscow, Russian Federation .
    Quantum phase transitions in mass-deformed ABJM matrix model2014In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 9, p. 021-Article in journal (Refereed)
    Abstract [en]

    When mass-deformed ABJM theory is considered on S-3, the partition function of the theory localises, and is given by a matrix model. At large N, we solve this model in the decompactification limit, where the radius of the three-sphere is taken to infinity. In this limit, the theory exhibits a rich phase structure with an infinite number of third-order quantum phase transitions, accumulating at strong coupling.

  • 170.
    Andersson, Anders
    Växjö University, Faculty of Mathematics/Science/Technology, School of Mathematics and Systems Engineering. Matematik.
    Using a Zipper Algorithm to find a Conformal Map for a Channel with Smooth Boundary2006In: AIP Conference Proceedings: Second Conference on Mathematical Modeling of Wave Phenomena, American Institute of Physics, New York , 2006, p. 378-Conference paper (Refereed)
    Abstract [en]

    The so called geodesic algorithm, which is one of the zipper algorithms for conformal mappings, is combined with a Schwarz–Christoffel mapping, in its original or in a modified form, to produce a conformal mapping function between the upper half-plane and an arbitrary channel with smooth boundary and parallel walls at the end.

  • 171.
    Andersson, Anders
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Mathematics and Systems Engineering.
    Nilsson, Börje
    Växjö University, Faculty of Mathematics/Science/Technology, School of Mathematics and Systems Engineering.
    Acoustic Transmission in Ducts of Various Shapes with an Impedance Condition2008In: International Conference on Numerical Analysis and Applied Mathematics 2008, AIP, Melville, USA , 2008, p. 33-36Conference paper (Refereed)
    Abstract [en]

    Propagation of acoustic waves in a two-dimensional duct with an impedance condition at the boundary, is studied. The duct is assumed to have two ends at infinity being asymptotically straight, but otherwise to be arbitrarily shaped.The so called Building Block Method allows us to synthesize propagation properties for ducts with complicated geometries from results for simpler ducts. Conformal mappings can be used to transform these simple ducts to straight ducts with constant cross-sections.By using recently developed techniques for numerical conformal mappings, it is possible to construct a transformation between an infinite strip and an arbitrarily shaped duct with smooth or piecewise smooth boundary, keeping both smoothness and the well controlled boundary direction towards infinity that the above mentioned method requires.To accomplish a stable formulation of the problem, we express it in terms of scattering operators. The resulting differential equation is solved using wave splitting and invariant embedding techniques. We expand the involved functions in Fourier series, and hence, it is possible to give the operators a matrix representation. Numerical results are produced using truncated matrices.

  • 172.
    Andersson, Anders
    et al.
    Jönköping University, School of Engineering, JTH, Mathematics.
    Nilsson, Börje
    International Centre for Mathematical Modelling, Växjö University.
    Electro-Magnetic Scattering in Variously Shaped Waveguides with an Impedance Condition2009In: AIP Conference Proceedings: Third Conference on Mathematical Modeling of Wave Phenomena: Växjö, Sweden, 9-13 June, 2008, American Institute of Physics , 2009, p. 36-45Conference paper (Refereed)
    Abstract [en]

    Electro-magnetic scattering is studied in a waveguide with varying shape and crosssection. Furthermore, an impedance or admittance condition is applied to two of the waveguide walls. Under the condition that variations in geometry or impedance take place in only one plane at the time, the problem can be solved as a two-dimensional wave-scattering problems. By using newly developed numerical conformal mapping techniques, the problem is transformedinto a wave-scattering problem in a straight two-dimensional channel. A numerically stable formulation is reached in terms of transmission and reflection operators. Numerical results are given for a slowly varying waveguide with a bend and for one more complex geometry.

  • 173.
    Andersson, Axel
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Real-Time Feedback for Agility Training: Tracking of reflective markers using a time-of-flight camera2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 174.
    Andersson Chronholm, Jannika
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Physics Didactics.
    Andersson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Physics Didactics.
    Bilder av människans inre: Förförståelse och studentaktivitet2010Conference paper (Other academic)
    Abstract [sv]

    Vi har infört ett inledande undervisningsmoment på en grundläggande biologikurs med syfte att utforska studenternas förståelse av mänsklig anatomi. En central slutsats från ämnesdidaktisk forskning är att studenterna som kommer till våra kurser har med sig en förförståelse sedan tidigare. För att bidra till ett konstruktivt lärande måste vi som lärare både vara medvetna om deras uppfattningar och utforma lärandeaktiviteter som hjälper dem att utveckla sin förståelse (Scott, Asoko & Leach, 2007).

    Momentet utgick från en uppgift där grupper med två till fyra studenter under femton minuter fick rita en förklarande bild av människokroppens inre och hur olika delar hänger ihop. Därefter genomfördes diskussioner i grupp och gemen­samt kring bilderna. Vi valde att arbeta med bilder för deras användbarhet både som diagnosverktyg och som hjälpme­del för fortsatt lärande (White & Gunstone, 1994). Dessutom fanns en modell för tolkning och klassning av studenters bilder sedan tidigare (Reiss & Tunnicliffe, 2001).

    Analysen av studenternas svar visade att hälften av grupperna redovisade en förhållandevis god kunskap av den mänskliga anatomin, med minst två sammanhängande organsystem utritade. De organsystem som studenterna hade bäst förståelse för var matsmältningssystemet och andningssystemet. Samtidigt uppvisade analysen en del märklighe­ter som tydligt visar att metoden inte förbehållningslöst kan användas för att få en korrekt bild av studenters förförstå­else, vilket också har diskuterats tidigare (Prokop & Fanèovièová, 2006).

    Som lärandemoment fungerade momentet mycket väl. I diskussionerna som följde efter övningen reflekterade studenterna kring sin nuvarande förståelse av människokroppen och motiverades inför den efterföljande kursen.

    Vi kommer att presentera resultat från analyserna av studenternas bilder samt diskutera hur undervisningsmomentet fungerade i praktiken med erfarenheter från både lärare, som fick en fördjupad insikt av just dessa studenters förförstå­else i området, och studenter, som började fundera kring både styrkor och svagheter i sin egen förståelse.

    Referenser

    Scott, P., Asoko, H. & Leach, J. (2007). Students’ Conceptions and Conceptual Learning in Science. In S. K. Abell & N. G. Lederman (Eds.), Handbook of Research on Science Education. Abingdon: Routledge.

    Prokop, P. & Fanèovièová, J. (2006) Student’s ideas about the human body: Do they really draw what they know? Jour­nal of Baltic Science Education 2(10): 86-95.

    Reiss, M.J. and Tunnicliffe, S.D. (2001) Students’ Understandings of Human Organs and Organ Systems Research in Science Education 31: 383–399.

    White, R. T., & Gunstone R. F. (1994) Probing understanding. London, UK: Falmer Press.

  • 175.
    Andersson Chronholm, Jannika
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Physics Didactics.
    Andersson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Physics Didactics.
    Föränderliga atomer och oklar energi - Att utforska studenters förförståelse: Poster presented at the NU2010 Dialog för Lärande Conference, Stockholm, 13-15 October.2010Other (Other academic)
    Abstract [sv]

    Som universitetslärare behöver vi utforska och förstå de uppfattningar som studenterna har om våra ämnen när de kommer till kurserna (se exempelvis Scott, Asoko & Leach, 2007) för att utforma vår undervisning och göra andra prioriteringar. Ett verktyg för detta är konceptinventeringar - enkätstudier som kartlägger studenters förförståelse.

    De första konceptinventeringarna inom naturvetenskaperna genomfördes inom fysiken, men utvecklingsarbete pågår numera även inom andra ämnesområden.

    Inom biologin tog arbetet fart i början av 2000-talet. Tidigt konstaterades att arbetet inom biologin delvis skiljer sig från det i fysik, men att det också finns likheter (Klymkowsky, Garvin-Doxas & Zeilik, 2003). Nu har olika grupper av biologer börjat samverka för att testa och utforma olika verktyg för konceptinventering (D’Avanzo, 2008).

    Som en del av utformningsarbetet av en grundläggande biologikurs, men också som en del av det internationella utvecklingsarbetet, genomför vi försök med en konceptinventering om bland annat respiration och matspjälkningen. Den konceptinventering vi utvecklat bygger på relevanta delar från Biology Concept Inventory (Klymkowsky, & Garvin-Doxas, 2008) och material från projektet Thinking lika a Biologist (www.biodqc.org). Urvalet gjordes utifrån innehållet på kursen och diskuterades med kollegor.

    Analyserna av de första försöken ger intressanta upplysningar om studenternas förförståelse, som delvis skiljer sig från den hos amerikanska studenter på vilka verktygen prövats tidigare. I vissa fall visar dock våra studenter precis samma brister i förförståelse som observerats för andra grupper. Bland annat har mer än 50 % av studenterna (som läst minst gymnasieskolans Kemi A) uppfattningen att ett atomslag enkelt kan omvandlas till ett annat. En fråga om energi visar också att de allra flesta (som läst minst gymnasieskolans Fysik A) har en oklar bild av vad energi egentligen är.

    Med denna posterpresentation vill vi öppna upp för diskussioner kring den förförståelse studenter tar med sig till våra kurser, hur vi kan utforska den förförståelsen samt hur vi som universitetslärare praktiskt kan arbeta utifrån detta.

    Referenser

    D’Avanco, C (2008) Biology Concept Inventories: Overview, Status, and Next Steps Bioscience 58(11):1079-1085.

    Klymkowsky, M.W., Garvin-Doxas, K. & Zeilik, M. (2003) Bioliteracy and Teaching Efficacy: What Biologists Can Learn from Physicists Cell Biology Education 2:155–161.

    Klymkowsky, M.W. & Garvin-Doxas, K. (2008) Recognizing Student Misconceptions through Ed’s Tool and the Biology Concept Inventory. PLoS Biology, 6:e3 (1-14).

    Scott, P., Asoko, H. & Leach, J. (2007). Student Conceptions and Conceptual Learning in Science. In S. K. Abell & N. G. Lederman (Eds.), Handbook of Research on Science Education. Abingdon: Routledge.

  • 176.
    Andersson Chronholm, Jannika
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Physics Didactics.
    Larsson, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Physics Didactics.
    Andersson, Gabriella
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Förstaårsstudenters och lärares förhållningssätt till laborationer i fysik2014Conference paper (Refereed)
    Abstract [sv]

    Laborationer används som ett närmast självklart inslag på naturvetenskapliga utbildningar. Mål och syften med laborationer kan skifta mellan olika kurser och är inte alltid uppenbara för studenterna (Hart et al., 2000; Russell & Weaver, 2008). Ofta förväntas de lära sig hantering av utrustning, tolkning av data och rapportskrivning, samtidigt som de ska få bättre förståelse för teorin genom att se

    Johan Larsson undersökte 2012 hur hans studenter på tekniskt-naturvetenskapligt basår (högskoleförberedande) värderade olika undervisningsformer. Laborationer fick då sämst betyg. För att undersöka möjliga orsaker till detta tog vi initiativ till en fenomenografisk studie (Marton, 1981) av attityder till fysiklaborationer. Skriftliga enkätsvar samlades in från 38 förstaårsstudenter på kandidatprogrammet i fysik vid Uppsala universitet. Den öppna enkätfrågan inspirerades av en amerikansk studie

    besvarades även av 18 anonyma lärare på Institutionen för fysik och astronomi. Både lärare och studenter har skrivit långa svar som vi kategoriserat fenomenografiskt, det vill säga vi har kartlagt förekomsten av attityder.

    Det finns tydliga nivåer av progression; från ett distanserat, ointresserat förhållningssätt till en nivå där man har en uppfattning om framtida behov. Studien visar inte på några större skillnader mellan lärarnas och studenternas syn. Laborationer förväntas koppla teori till praktik samt ge tillfälle att träna på instrumenthantering och vetenskapligt arbetssätt. Några nämner också att laborationer ökar deras förståelse och lärande, ger social träning och förbereder dem för ett kommande arbetsliv.

    Vår avsikt är att använda resultaten för att öka laborationernas upplevda värde, genom att uppmärksamma kollegor på de förekommande förhållningssätten och tillsammans förbereda oss för att bemöta dem. Frågor som vi vill diskutera är t.ex.: Vill vi att studenterna ska tycka så här?

    Hur speglar våra laborationsinstruktioner det vi vill att studenterna ska lära sig? Hur kommunicerar vi mål och syften med varje laboration på bästa sätt?

    Hart C., Mulhall, P., Berry, A., Loughran, J., & Gunstone, R. (2000). What is the purpose of this experiment? Or can students learn something from doing experiments? Journal of Research in Science Teaching, 37(7), 655-675. Marton, F. (1981). Phenomenography Describing conceptions of the world around us. Instructional Science, 10, 177-200.

    Russell, C. B., & Weaver, G. C. (2008). Student Perceptions of the Purpose and Function of the Laboratory in Science: A Grounded Theory Study. International Journal for the Scholarship of Teaching and Learning, 2(2), 1-14.

  • 177.
    Andersson Chronholm, Jannika
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Physics Didactics.
    Larsson, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Physics Didactics.
    Andersson, Gabriella
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Förstaårsstudenters och lärares syn på laborationer i fysik2013Conference paper (Refereed)
    Abstract [sv]

    Bakgrund

    Då institutionen för fysik och astronomi under 2013 identifierat laborationerna som ett problemområde har vi gjort en fenomenografisk studie som undersökte studenters och lärares syn på laborationer.

     

    Datainsamling och analys

    Vi har samlat in skriftliga enkätsvar från 18 lärare och 38 förstaårsstudenter på kandidatprogrammet i fysik.

    Den öppna enkätfrågan var : - Varför har vissa kurser laborationer?

    Svaren visar på många olika uppfattningar och vi har kategoriserat dessa fenomenografiskt.

     

    Resultat

    Vi ser tydliga nivåer av progression i svaren; från ett distanserat och ointresserat förhållningssätt, till en uppfattning om lärande och framtida yrkesliv.

    Studien visar att lärare och studenterna har mycket lika syn på laborationer.

    Uppfattningar som fördes fram var att kurser har laborationer för att :

     

    l   det är obligatoriskt

    l   koppla teori till praktik

    l   öva instrumenthantering

    l   träna vetenskapligt arbetssätt

    l   öka förståelsen och lärandet

    l   ge social träning

    l   utgöra förberedelse för arbetsliv

     

     

    Referenser

    Marton, F. (1981) Phenomenography – Describing conceptions of the world around us. Instructional Science, 10, 177-200.

    Russell, C. B. and Weaver, G. C. (2008) Student Perceptions of the Purpose and Function of the Laboratory in Science: A Grounded Theory Study. International Journal for the Scholarship of Teaching and Learning 2(2).

                 

  • 178.
    Andersson, Conny
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Design of the Modelica Library VehProLib with Non-ideal Gas Models in Engines2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis covers the reconstruction and the redesign of the modeling library VehProLib,which is constructed in the modeling language Modelica with help of the modeling toolWolfram SystemModeler. The design choices are discussed and implemented. This thesisalso includes the implementation of a turbocharger package and an initial study of the justificationof the ideal gas law in vehicle modeling. The study is made with help of Van derWaals equation of states as a reference of non-ideal gas model. It will be shown that for themean-value-engine-model, the usage of ideal gas law is justified.

  • 179.
    Andersson, David
    Stockholm University, Faculty of Science, Department of Physics.
    On the Evolving Friction of Layered Materials and the Prospect of Their Image Reconstruction2019Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The scope of this licentiate thesis is twofold: 1. Investigate the frictional properties of systems with layered materials; 2. Employing image recognition algorithms to find the substrates in AFM experiments. As of today, there is a clear dichotomy separating these projects, however, it is the long term goal that they should coalesce in a not too distance future. The friction in layered materials projects is already finished, in this project we expanded the venerated Prandtl-Tomlison model to incorporate atomically thin layered materials such as graphene. This project has proved successful beyond our expectations, and a score of experimental results and conflicts in the field can be explained and resolved using our model. The image reconstruction project however, is still on a basic level. So far we have compared a standard model – Histogram Analysis Method– for image reconstruction on the nano-level with a popular image reconstruction algorithm –Lucy Richardson Deconvolution – from astronomy and shown that the latter is more suitable for these kind of systems. However, this project is far from finished, and the results in this part should be regarded as both partial and preliminary.

  • 180. Andersson, John
    et al.
    Shahgholian, Henrik
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Mathematics (Div.).
    Weiss, Georg S.
    Uniform Regularity Close to Cross Singularities in an Unstable Free Boundary Problem2010In: Communications in Mathematical Physics, ISSN 0010-3616, E-ISSN 1432-0916, Vol. 296, no 1, p. 251-270Article in journal (Refereed)
    Abstract [en]

    We introduce a new method for the analysis of singularities in the unstable problem Delta u = chi{u> 0}, which arises in solid combustion as well as in the composite membrane problem. Our study is confined to points of "supercharacteristic" growth of the solution, i.e. points at which the solution grows faster than the characteristic/invariant scaling of the equation would suggest. At such points the classical theory is doomed to fail, due to incompatibility of the invariant scaling of the equation and the scaling of the solution. In the case of two dimensions our result shows that in a neighborhood of the set at which the second derivatives of u are unbounded, the level set {u = 0} consists of two C-1-curves meeting at right angles. It is important that our result is not confined to the minimal solution of the equation but holds for all solutions.

  • 181.
    Andersson, Jonas
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Ion recombination in liquid ionization chambers: development of an experimental method to quantify general recombination2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    An experimental method (the two-dose-rate method) for the correction of general recombination losses in liquid ionization chambers has been developed and employed in experiments with different liquids and radiation qualities. The method is based on a disassociation of initial and general recombination, since an ionized liquid is simultaneously affected by both of these processes.

    The two-dose-rate method has been compared to an existing method for general recombination correction for liquid ionization chambers, and has been found to be the most robust method presently available.

    The soundness of modelling general recombination in liquids on existing theory for gases has been evaluated, and experiments indicate that the process of general recombination is similar in a gas and a liquid. It is thus reasonable to employ theory for gases in the two-dose-rate method to achieve experimental corrections for general recombination in liquids. There are uncertainties in the disassociation of initial and general recombination in the two-dose-rate method for low applied voltages, where initial recombination has been found to cause deviating results for different liquids and radiation qualities.

    Sensitivity to ambient electric fields has been identified in the microLion liquid ionization chamber (PTW, Germany). Experimental data may thus be perturbed if measurements are conducted in the presence of ambient electric fields, and the sensitivity has been found to increase with an increase in the applied voltage. This can prove to be experimentally limiting since general recombination may be too severe for accurate corrections if the applied voltage is low.

  • 182.
    Andersson, Jonas
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Radiation Dosimetry for CBCT – Quality Control and Applied Dosimetry2015Conference paper (Refereed)
    Abstract [en]

    The use of Cone Beam CT (CBCT) devices in health care has increased in recent years. Unfortunately, this trend has not been followed by a standardization of dose metrics for Quality Control (QC), or a necessary evolution of applied dosimetry for assessment of patient dose.

    The European Federation of Organisations in Medical Physics (EFOMP) has drafted a report on the property of QC for CBCT devices. The report contains objective, practical and unifying methodology for QC of CBCT used in oral radiology, radiotherapy, interventional radiology and guided surgery. The dose metrics discussed include the Computed Tomography Dose Index (CTDI), Kerma-Area Product (KAP) and detector incident air kerma. The report concludes that KAP-meters are preferable for QC as long as they can be mounted on the X-ray tube housing. Otherwise measurements of detector incident kerma seem to offer a practical solution for QC.

    The European Radiation Dosimetry Group (EURADOS) are preparing a literature review on patient dose from various applications of CBCT, which will in part be included in the EFOMP report. Most studies on patient dose from CBCT examinations and interventional procedures are based on thermoluminescent dosimeter (TLD) measurements in Rando phantoms. While helpful to the community, these studies yield substantial uncertainty when applied in the clinical reality of medical physicists working with justification and optimization. Applied dosimetry for CBCT needs to evolve and adopt recent theoretical advances to allow robust estimates of patient dose.

  • 183.
    Andersson, Jonas
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Granberg, Christoffer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Riklund, Katrine
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology.
    A novel system for quality assurance of radiology equipment2018In: Eurosafe Imaging 2018, 2018Conference paper (Refereed)
  • 184.
    Andersson, Jonas
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Johansson, Erik
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Tölli, Heikki
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    On the property of measurements with the PTW microLion chamber in continuous beam2012In: Medical physics (Lancaster), ISSN 0094-2405, Vol. 39, no 8, p. 4775-4787Article in journal (Refereed)
    Abstract [en]

    Purpose: The performance of liquid ionization chambers, which may prove to be useful tools in the field of radiation dosimetry, is based on several chamber and liquid specific characteristics. The present work investigates the performance of the PTW microLion liquid ionization chamber with respect to recombination losses and perturbations from ambient electric fields at various dose rates in continuous beams.

    Methods: In the investigation, experiments were performed using two microLion chambers, containing isooctane (C8H18) and tetramethylsilane (Si(CH3)4) as the sensitive media, and a NACP-02 monitor chamber. An initial activity of approximately 250 GBq 18F was employed as the radiation source in the experiments. The initial dose rate in each measurement series was estimated to 1.0 Gy min-1 by Monte Carlo simulations and the measurements were carried out during the decay of the radioactive source. In the investigation of general recombination losses, employing the two-dose-rate method for continuous beams, the liquid ionization chambers were operated at polarizing voltages 25, 50, 100, 150, 200 and 300 V. Furthermore, measurements were also performed at 500 V polarizing voltage in the investigation of the sensitivity of the microLion chamber to ambient electric fields.

    Results: The measurement results from the liquid ionization chambers, corrected for general recombination losses according to the two-dose-rate method for continuous beams, had a good agreement with the signal to dose linearity from the NACP-02 monitor chamber for general collection efficiencies above 70%. The results also displayed an agreement with the theoretical collection efficiencies according to the Greening theory, except for the liquid ionization chamber containing isooctane operated at 25 V. At lower dose rates, perturbations from ambient electric fields were found in the microLion chamber measurement results. Due to the perturbations, measurement results below an estimated dose rate of 0.2 Gy min-1 were excluded from the present investigation of the general collection efficiency. The perturbations were found to be more pronounced when the chamber polarizing voltage was increased.

    Conclusions: By using the two-dose-rate method for continuous beams, comparable corrected ionization currents from experiments in low- and medium energy photon beams can be achieved. However, the valid range of general collection efficiencies has been found to vary in a comparison between experiments performed in continuous beams of 120 kVp x-ray, and the present investigation of 511 keV annihilation photons. At very high dose rates in continuous beams, there are presently no methods that can be used to correct for general recombination losses and at low dose rates the microLion chamber may be perturbed by ambient electric fields. Increasing the chamber polarizing voltage, which diminishes the general recombination effect, was found to increase the microLion chamber sensitivity to ambient electric fields. Prudence is thus advised when employing the microLion chamber in radiation dosimetry, as ambient electric fields of the strength observed in the present work may be found in many common situations. Due to uncertainties in the theoretical basis for recombination losses in liquids, further studies on the underlying theories for the initial and general recombination effect are needed if liquid ionization chambers are to become a viable option in high precision radiation dosimetry.

  • 185.
    Andersson, Jonas
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Kaiser, Franz-Joachim
    Gómez, Faustino
    Jäkel, Oliver
    Pardo-Montero, Juan
    Tölli, Heikki
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    A comparison of different experimental methods for general recombination correction for liquid ionization chambers2012In: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 57, no 21, p. 7161-7175Article in journal (Refereed)
    Abstract [en]

    Radiation dosimetry of highly modulated dose distributions requires a detector with a high spatial resolution. Liquid filled ionization chambers (LICs) have the potential to become a valuable tool for the characterization of such radiation fields. However, the effect of an increased recombination of the charge carriers, as compared to using air as the sensitive medium has to be corrected for. Due to the presence of initial recombination in LICs, the correction for general recombination losses is more complicated than for air-filled ionization chambers. In the present work, recently published experimental methods for general recombination correction for LICs are compared and investigated for both pulsed and continuous beams. The experimental methods are all based on one of two approaches, either measurements at two different dose rates (two-dose-rate methods), or measurements at three different LIC polarizing voltages (three-voltage methods). In a comparison with the two-dose-rate methods, the three-voltage methods fail to achieve accurate corrections in several instances, predominantly at low polarizing voltages and dose rates. However, for continuous beams in the range of polarizing voltages recommended by the manufacturer of the LICs used, the agreement between the different methods is generally within the experimental uncertainties. For pulsed beams, the agreement between the methods is poor. The inaccuracies found in the results from the three-voltage methods are associated with numerical difficulties in solving the resulting equation systems, which also make these methods sensitive to small variations in the experimental data. These issues are more pronounced for the case of pulsed beams. Furthermore, the results suggest that the theoretical modelling of initial recombination used in the three-voltage methods may be a contributing factor to the deviating results observed.

  • 186.
    Andersson, Jonas
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Pavlicek, William
    Patient organ dose with computed tomography - a review of present methodology and DICOM information: executive summary of the joint report of AAPM task group 246 and EFOMP2016In: ECR 2016 Book of Abstracts, 2016, Vol. 7, no 1, article id B0303Conference paper (Refereed)
    Abstract [en]

    Purpose: The justification and optimisation of medical imaging employing ionizing radiation have been intensely discussed in recent years, particularly for computed tomography (CT). A key point in this discussion is the estimation of patient dose, which commonly employs radiation output metrics developed for quality assurance and no patient specific information. Such patient dose estimates are of limited value, and more refined methods needs to be promoted and provided to the community.

    Methods and Materials: AAPM Task Group 246 was formed in 2013, and in a joint venture with EFOMP charged with summarizing present methodology and DICOM information available for estimating patient dose with computed tomography.

    Results: The Joint Report of AAPM Task Group 246 and EFOMP is a comprehensive resource for the clinical medical physicist. The possibilities of patient specific dosimetry from the Computed Tomography Dose Index (CTDIvol), to the Size-Specific Dose Estimates (SSDE) and advanced Monte Carlo methods are discussed together with available DICOM information, as well as practical examples on how patient dose estimates can be achieved. The report also summarizes important factors contributing to the uncertainty in patient dose estimates and gives examples of achievable confidence intervals.

    Conclusion: The SSDE and Monte Carlo methods can together with detailed scanner, examination and patient specific DICOM information offer refined estimates of patient dose for justification and optimisation of CT examinations. Given the present robustness of available methods AAPM Task Group 246 and EFOMP recommend that all reports of patient dose should be accompanied by estimates of the associated uncertainty.

  • 187.
    Andersson, Jonas
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Tölli, Heikki
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Modeling ion recombination in liquid ionization chambers: Improvement and analysis of the two-dose-rate method2017In: Medical physics (Lancaster), ISSN 0094-2405, Vol. 44, no 11, p. 5977-5987Article in journal (Refereed)
    Abstract [en]

    Purpose: The use of liquid ionization chambers can provide useful information to endeavors with radiation dosimetry for highly modulated beams. Liquid ionization chambers may be particularly suitable for computed tomography applications where conventional ionization chambers do not present a high enough sensitivity for the spatial resolution required to characterize common X-ray beams. Due to the sensitivity, which leads to high charge densities, liquid ionization chambers can suffer from large recombination losses leading to degradation in signal to dose rate linearity. To solve this problem, a two-dose-rate method for general recombination correction has been proposed for liquid ionization chambers. However, the valid range of recombination losses that the method can accurately account for has been found to vary depending on radiation quality. The present work provides an in-depth analysis of the performance of the two-dose-rate method. Furthermore, the soundness of applying gas theory to liquids is investigated by using the two-dose-rate method.

    Methods: In the present work, the two-dose-rate method for general recombination correction of liquid ionization chambers used in continuous beams is studied by employing theory for gas-filled ionization chambers. An approximate relation for the general collection efficiency containing a material-specific parameter that is traceable to liquids has been derived for theoretical and experimental investigation alongside existing theory. Furthermore, the disassociation between initial and general recombination in the method is analyzed both theoretically and experimentally.

    Results: The results indicate that liquids and gases share general recombination characteristics, where the liquids investigated (isooctane and tetramethylsilane) to a large extent mimic the behavior theoretically expected in gases. Furthermore, it is shown that the disassociation between initial and general recombination in the two-dose-rate method is an approximation that depends on the relation between initial recombination and the collecting electric field strength at the dose rates used.

    Conclusions: Due to the approximation used to separate initial and general recombination the valid range of collection efficiencies for the two-dose-rate method will not only depend on the model used to describe general recombination but also on the type of liquid and radiation beam quality. As there is no robust theory for initial recombination in liquids to apply, the valid range of general collection efficiencies for the two-dose-rate method should be experimentally evaluated for each radiation dosimetry application.

  • 188.
    Andersson, Jonas
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Tölli, Heikki
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    The Use of Liquid Ionization Chambers in Radiation Dosimetry2012In: World Congress on Medical Physics and Biomedical Engineering May 26-31, 2012 Beijing, China / [ed] Mian Long, Springer, 2012Conference paper (Refereed)
    Abstract [en]

    Liquid ionization chambers (LICs) have found applications in many fields in radiation dosimetry, e.g. IMRT, hadron therapy, brachytherapy and computed tomography. The wide range of applications is made possible due to the high sensitivity of LICs, allowing them to be manufactured with small physical dimensions of the chamber body and the effective measurement volume. Furthermore, the commonly used liquids (such as isooctane) have radiation absorption characteristics similar to water, introducing only small fluence perturbation effects as compared to conventional dosimeters. The small dimension of the effective measurement volume is beneficial for the quantification of radiation beams with steep gradients, while retaining a high measurement signal with good statistical properties. However, the interpretation of measurement results is not straight-forward due to several factors influencing their performance. Here, the main problems are recombination effects and particle type- and energy dependence, which may cause severe non-linear effects. The loss of measurement signal in LICs is due to both initial and general recombination. In the present work it is shown that the general recombination effect can be treated with in a similar manner as for air-filled ionization chambers, while there are currently no theories that adequately describe the initial recombination effect for LICs. Furthermore, the relationship between energy dependence and recombination losses in LICs are evaluated at different radiation qualities. Recently developed methods for the correction of general recombination losses in LICs are discussed and their validity evaluated.

  • 189.
    Andersson, L.C.
    et al.
    Luleå tekniska universitet.
    Hauska, Hans
    Luleå tekniska universitet.
    Lineament mapping in Northern Sweden from Landsat images using orthogonal image transforms1980In: Sixth Annual Symposium Machine Processing of Remotely Sensed Data and Soil Information Systems and Remote Sensing and Soil Survey, June 3 - 6, 1980, Purdue Univ., Laboratory for Applications of Remote Sensing, West Lafayette, Ind / [ed] P.G. Burroff, New York: IEEE Communications Society, 1980, p. 147-157Conference paper (Refereed)
    Abstract [en]

    The emphasis of this paper is put on mapping of geological linear structures, and in particular the correlation between these structures orientation and geological or geophysical data. It is also the intention of the authors to present a method to map these structures more objectively than up to now

  • 190.
    Andersson, L.C.
    et al.
    Luleå tekniska universitet.
    Hauska, Hans
    Luleå tekniska universitet.
    Lineaments analysis using global and local Fourier transforms1983In: Proceedings of the fourth international conference on basement tectonics, Oslo, Norway, August 10-14, 1981 / [ed] Roy H. Gabrielsen, Salt Lake City: International Basement Tectonics Association , 1983, p. 63-69Conference paper (Refereed)
  • 191.
    Andersson, M
    et al.
    Chalmers University of Technology.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ljungstrom, S
    Chalmers University of Technology.
    Palmqvist, A E C
    Chalmers University of Technology.
    Preparation of nanosize anatase and rutile TiO2 by hydrothermal treatment of microemulsions and their activity for photocatalytic wet oxidation of phenol2002In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 106, no 41, p. 10674-10679Article in journal (Refereed)
    Abstract [en]

    Titanium dioxide (TiO2) nanoparticles of both anatase and rutile phases were synthesized by hydrothermal treatment of microemulsions, and their photocatalytic activity for wet oxidation of phenol was studied. The only difference between the two syntheses used was that different acids were added to the microemulsions, making direct comparison of the catalytic activity of the two polymorphs possible. If hydrochloric acid was used, the rutile structure formed, and if nitric acid was used, anatase formed. The phase stability of the microemulsion was studied and according to conductivity and turbidity measurements the idea of a direct template effect could be discarded during the hydrothermal treatment. However, an initial size-templating phenomenon is possible during the mixing step. The particles, which were in the size range of a few nanometers were characterized with N-2-adsorption; XRD, SEM, and XPS. The activity of the two polymorphs for the photocatalytic oxidation of phenol in water was examined. It was shown that the rutile phase initially decomposed phenol much faster and follows a first-order process reasonably well (k = 4 x 10(-5) s(-1)). The photodecomposition process using the anatase phase led, however, to a much more rapid overall degradation following an initial slower rate of phenol oxidation. The results indicate that the observed difference of the photodecomposition process for the two TiO2 phases is due to the formation of different intermediates.

  • 192.
    Andersson, Magnus
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Fällman, Erik
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Uhlin, Bernt Eric
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Axner, Ove
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Force measuring optical tweezers system for long time measurements of P pili stability2006In: Imaging, Manipulation, and Analysis of Biomolecules, Cells, and Tissues IV / [ed] Farkas, DL, Nicolau, DV, Leif, RC, 2006, Vol. 6088, p. 608810-Conference paper (Refereed)
    Abstract [en]

    A force-measuring optical tweezers instrumentation and long time measurements of the elongation and retraction of bacterial fimbriae from Uropathogenic E. coli (UPEC) under strain are presented. The instrumentation is presented in some detail. Special emphasis is given to measures taken to reduce the influence of noise and drifts in the system and from the surrounding, which makes long term force measurements possible. Individual P pili from UPEC bacteria were used as a biological model system for repetitive unfolding and refolding cycles of bacterial fimbriae under equilibrium conditions. P pili have evolved into a three-dimensional helix-like structure, the PapA rod, that can be successively and significantly elongated and/or unfolded when exposed to external forces. The instrumentation is used for characterization of the force-vs.-elongation response of the PapA rod of individual P pili, with emphasis on the long time stability of the forced unfolding and refolding of the helical structure of the PapA rod. The results show that the PapA rod is capable of withstanding extensive strain, leading to a complete unfolding of the helical structure, repetitive times during the life cycle of a bacterium without any noticeable alteration of the mechanical properties of the P pili. This function is believed to be importance for UPEC bacteria in vivo since it provides a close contact to a host cell (which is an initial step of invasion) despite urine cleaning attempts.

  • 193.
    Andersson, Magnus
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Svantesson, Mats
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Björnham, Oscar
    Swedish Defence Research Agency (FOI), SE-906 21 Umeå, Sweden.
    Badahdah, Arwa
    Department of Oral Biology, Boston University School of Dental Medicine.
    Uhlin, Bernt Eric
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Bullitt, Esther
    Department of Physiology and Biophysics, Boston University School of Medicine.
    A structural basis for sustained bacterial adhesion: Biomechanical properties of CFA/I Pili2012In: Journal of Molecular Biology, ISSN 0022-2836, E-ISSN 1089-8638, Vol. 415, no 5, p. 918-928Article in journal (Refereed)
    Abstract [en]

    Enterotoxigenic Escherichia coli (ETEC) are a major cause of diarrheal disease worldwide. Adhesion pili (or fimbriae), such as the CFA/I (colonization factor antigen I) organelles that enable ETEC to attach efficiently to the host intestinal tract epithelium, are critical virulence factors for initiation of infection. We characterized at single organelle level the intrinsic biomechanical properties and kinetics of individual CFA/I pili, demonstrating that weak external forces (7.5 pN) are sufficient to unwind the intact helical filament of this prototypical ETEC pilus and that it quickly regains its original structure when the force is removed. While the general relationship between exertion of force and an increase in the filament length for CFA/I pili associated with diarrheal disease is analogous to that of P-pili and type 1 pili, associated with urinary tract and other infections, the biomechanical properties of these different pili differ in key quantitative details. Unique features of CFA/I pili, including the significantly lower force required for unwinding, the higher extension speed at which the pili enter a dynamic range of unwinding, and the appearance of sudden force drops during unwinding can be attributed to morphological features of CFA/I pili including weak layer-to-layer interactions between subunits on adjacent turns of the helix, and the approximately horizontal orientation of pilin subunits with respect to the filament axis. Our results indicate that ETEC CFA/I pili are flexible organelles optimized to withstand harsh motion without breaking, resulting in continued attachment to the intestinal epithelium by the pathogenic bacteria that express these pili.

  • 194.
    Andersson, Mike
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    SiC based field effect sensors and sensor systems for combustion control applications2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Increasing oil prices and concerns about global warming have reinforced the interest in biofuels for domestic and district heating, most commonly through combustion of solid biomass like wood logs, hog fuel and pellets. Combustion at non-optimal conditions can, however, lead to substantial emissions of noxious compounds like unburned hydrocarbons, carbon monoxide, and nitrogen oxides as well as the generation of soot.

    Depending on the rate of combustion more or less air is needed per unit time to completely oxidize the fuel; deficiency of air leading to emissions of unburned matter and too much of excess air to slow combustion kinetics and emissions of mainly carbon monoxide. The rate of combustion is influenced by parameters like fuel quality – moisture and ash content etc. – and in what phase the combustion takes place (in the gas phase through combustion of evaporated substances or on the surface of char coal particles), none of which is constant over time.

    The key to boiler operation, both from an environmental as well as a power to fuel economy point of view, is thus the careful adjustment of the air supply throughout the combustion process. So far, no control schemes have been applied to small-scale combustors, though, mainly due to the lack of cheap and simple means to measure basic flue gas parameters like oxygen, total hydrocarbon, and carbon monoxide concentrations.

    This thesis reports about investigations on and characterization of silicon carbide (SiC) based Metal Insulator Semiconductor (MIS) field effect gas sensors regarding their utility in emissions monitoring and combustion control applications as well as the final development of a sensor based control system for wood fired domestic heating systems.

    From the main sensitivity profiles of such sensor devices, with platinum (Pt) and iridium (Ir) as the catalytic metal contacts (providing the gas sensing ability), towards some typical flue gas constituents as well as ammonia (NH3), a system comprising four individual sensors operated at different temperatures was developed, which through the application of Partial Least Squares (PLS) regression, showed good performance regarding simultaneous monitoring of propene (a model hydrocarbon) and ammonia concentrations in synthetic flue gases of varying content. The sensitivity to CO was, however, negligible. The sensor system also performed well regarding ammonia slip monitoring when tested in real flue gases in a 5.6 MW boiler running SNCR (Selective Non-Catalytic reduction of nitrogen oxides with ammonia).

    When applied to a 200 kW wood pellet fuelled boiler a similar sensor system was, however, not able to follow the flue gas hydrocarbon concentration in all encountered situations. A PCA (Principal Components Analysis) based scheme for the manipulation of sensor and flue gas temperature data, enabling monitoring of the state of combustion (deficiency or too much of excess air), was however possible to develop. The discrepancy between laboratory and field test results was suspected and later on shown to depend on the larger variation in CO and oxygen concentrations in the flue gases as compared to the laboratory tests.

    Detailed studies of the CO response characteristics for Pt gate MISiC sensors revealed a highly non-linear sensitivity towards CO, a large response only encountered at high CO/O2 ratios or low temperatures. The response exhibits a sharp switch between a small and a large value when crossing a certain CO/O2 ratio at constant operating temperature, correlated to the transition from an oxygen dominated to an almost fully CO covered Pt surface, originating from the difference in adsorption kinetics between CO and O2. Indications were also given pointing towards an increased sensitivity to background hydrogen as being the mediator of at least part of the CO response. Some general characteristics regarding the response mechanism of field effect sensors with differently structured metal contacts were also indicated.

    The CO response mechanism of Pt metal MISiC sensors could also be utilized in developing a combustion control system based on two sensors and a thermocouple, which when tested in a 40 kW wood fired boiler exhibited a good performance for fuels with extremely low to normal moisture content, substantially decreasing emissions of unburned matter.

  • 195. Andersson, O.
    et al.
    Soldatov, Alexander
    Sundqvist, B.
    Thermal conductivity of C60 at pressures up to 1 GPa and temperatures in the 50-300 K range1996In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 54, no 5, p. 3093-3100Article in journal (Refereed)
    Abstract [en]

    The thermal conductivity λ of C60 shows anomalies near 260 K and 90 K which are associated with the well-established phase transition and glass transition, respectively. Both transition temperatures increase with pressure, at the rates 120 K GPa-1 and 62 K GPa-1, respectively. With increasing temperature, λ of the simple cubic (sc) phase increased below 170 K (glasslike behavior) but decreased above. The glasslike behavior of λ is probably due to a substantial amount of lattice defects. Possible reasons for the change of sign of dλ/dT near 170 K are discussed. In the face centered cubic (fcc) phase (T≳260 K at atmospheric pressure) λ was almost independent of temperature, a behavior which is far from that of an ordered crystal (λ∝T-1 for T≳Debye temperature). This result can be attributed to the molecular orientational disorder of the fcc phase. The relaxation behavior associated with the glassy state and its unusually strong dependence on thermal history are discussed briefly, and data which support a previously reported relaxation model are presented. At room temperature, the density dependencies of λ, (∂ lnλ/∂ lnρ)T, were 5.5 and 9.5 for the fcc and sc phases, which are values typical for an orientationally disordered phase and a normal crystal phase, respectively.

  • 196. Andersson, O.
    et al.
    Soldatov, Alexander
    Sundqvist, B.
    Thermal conductivity of C60 under high pressure1995In: Science and technology of fullerene materials: symposium held November 28 - December 2, 1994, Boston, Massachusetts, U.S.A / [ed] Patrick Bernier, Pittsburgh, Pa: Materials Research Society, 1995, p. 549-554Conference paper (Refereed)
  • 197. Andersson, O.
    et al.
    Soldatov, Alexander
    Sundqvist, Bertil
    Reorientational relaxation in C60 following a pressure induced change in the pentagon/hexagon equilibrium ratio1995In: Physics Letters A, ISSN 0375-9601, E-ISSN 1873-2429, Vol. 206, no 3-4, p. 260-264Article in journal (Refereed)
    Abstract [en]

    The orientational structure of C60 depends on pressure and temperature. Pressurization below the glass transition temperature Tg can freeze in non-equilibrium orientational structures. The relaxation of such structures on heating through Tg has been studied through thermal conductivity measurements and the effects observed are explained in a simple model.

  • 198.
    Andersson, Ole
    et al.
    Dept. of Physics, Stockholm University, Sweden.
    Bengtsson, Ingemar
    Dept. of Physics, Stockholm University, Sweden.
    Ericsson, Marie
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Sjöqvist, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala universitet.
    Geometric phases for mixed states of the Kitaev chain2016In: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 374, no 2069, article id 20150231Article in journal (Refereed)
    Abstract [en]

    The Berry phase has found applications in building topological order parameters for certain condensed matter systems. The question whether some geometric phase for mixed states can serve the same purpose has been raised, and proposals are on the table. We analyze the intricate behaviour of Uhlmann’s geometric phase in the Kitaev chain at finite temperature, and then argue that it captures quite different physics from that intended. We also analyze the behaviour of a geometric phase introduced in the context of interferometry. For the Kitaev chain, this phase closely mirrors that of the Berry phase, and we argue that it merits further investigation. 

  • 199.
    Andersson, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Holcombe, Scott
    Halden Reactor Project.
    Tverberg, Terje
    Halden Reactor Project.
    Inspection of LOCA Test Rod IFA-650.15 Using Gamma Emission Tomography2016Report (Other academic)
  • 200.
    Andersson, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Sundén, E. Andersson
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Jacobsson Svärd, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Sjöstrand, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Correction for dynamic bias error in transmission measurements of void fraction2012In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 83, no 12, p. 125110-Article in journal (Refereed)
    Abstract [en]

    Dynamic bias errors occur in transmission measurements, such as X-ray, gamma, or neutron radiography or tomography. This is observed when the properties of the object are not stationary in time and its average properties are assessed. The nonlinear measurement response to changes in transmission within the time scale of the measurement implies a bias, which can be difficult to correct for. A typical example is the tomographic or radiographic mapping of void content in dynamic two-phase flow systems. In this work, the dynamic bias error is described and a method to make a first-order correction is derived. A prerequisite for this method is variance estimates of the system dynamics, which can be obtained using high-speed, time-resolved data acquisition. However, in the absence of such acquisition, a priori knowledge might be used to substitute the time resolved data. Using synthetic data, a void fraction measurement case study has been simulated to demonstrate the performance of the suggested method. The transmission length of the radiation in the object under study and the type of fluctuation of the void fraction have been varied. Significant decreases in the dynamic bias error were achieved to the expense of marginal decreases in precision.

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