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  • 201.
    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.

  • 202.
    Alpsten, Freja
    Stockholm University, Faculty of Science, Department of Physics.
    Investigation of a Collapsed Cone Superposition Algorithm for dosimetry in brachytherapy2021Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Background & Purpose: The current standard dosimetry in brachytherapy treatment planning, the TG-43 formalism, ignore the presence of non-water media and finite patient dimensions. This can cause clinically relevant errors in dose estimates. To over- come the limitations of the TG-43 formalism, Model-Based Dose Calculation Algorithms (MBDCAs) have evolved. One of the commercial available MBDCAs is the Advanced Collapsed cone Engine (ACE) by Elekta. In ACE, the total dose is divided into three components, the primary, the first-scattered and the multiple-scattered dose, where the two last mentioned are calculated by the means of the Collapsed Cone Algorithm.

    In this study the performance of ACE has been investigated. The study has been di- vided into 2 parts, where the aim of part 1 was to analyze the relationship between the so called discretization artifacts, caused by the collapsed cone approximation, and the number of dwell positions. The severeness of the artifact is thought to decrease as the number of dwell positions are increased. The second part focus on ACE’s behavior in cortical bone, with the aim to form a hypothesis (explanation and solution) to the previously observed dose underestimation of the dose to bone made by ACE.

    Materials and Methods: The generic 192Ir source, the Oncentra Brachy (OcB) treatment planning system (TPS) and the Monte Carlo (MC) platform ALGEBRA have been utilized. In the first part of the study, six source configurations, all with a different number of dwell positions, were created and placed in the center of large water phantoms, i.e. under TG-43 conditions in which the TG-43 formalism can be assumed to yield a high accuracy of the estimated dose. The accuracy of ACE has been judged by its’ deviation from TG-43.

    In the second part of the study, a cubic source configuration, of 27 dwell positions, was positioned at the center of a cubic water phantom. Three cases where constructed, with a small cortical bone heterogeneity positioned at different distances from the source configu- ration. The ACE calculated dose distribution has been divided into its’ three constituents. The accuracy of ACE and TG-43 has been judged by its’ deviation from MC.

    Results: Part 1 showed that increasing the number of dwell positions does not guar- antee an improved accuracy of ACE. Local dose difference ratios of > 2%, caused by the artifacts, were mainly located outside the 5% isodose line. A general dose underestima- tion was observed in ACE, with an increased magnitude as the dose level decreased. The majority of local dose difference ratios below -4% were found where the multi-resolution voxelization grid of ACE has a voxel size of ≥23 mm3, that is at a distance of ≥8 cm from the closest dwell position when using the ACE standard accuracy level.

    In part 2, ACE underestimated the dose to cortical bone, with an increased magnitude as the bone was positioned farther away from the source configuration. The TG-43 formalism gave slightly better estimates of the mean dose to bone than ACE, especially at higher dose levels. For a mean dose to the cortical bone heterogeneity equal to 45% of the prescribed dose, TG-43 and ACE underestimated the mean dose with 1% and 4%, respectively. The estimated mean dose to a volume located directly behind the heterogeneity agreed within 1% between ACE and MC. However, an increased amount of positive local dose difference ratios were observed in this volume.

    Conclusions: Increasing the number of dwell positions cause a ”blurring” effect of the artifact, but may also increase the fluence gradient. In such situations the severeness of the artifact may not be improved. In patient cases the dwell positions are usually added in a more random manner which may favor the ”blurring effect”.

    The underestimations observed in ACE are thought to be caused by both the multiple- resolution voxelization grid of ACE and the relationship between the dimensions of the phantom in which the multiple-scattered kernel has been generated and the current calcu- lation volume.

    ACE was unsuccessful to predict the dose to cortical bone, and should hence be used with caution when cortical bone is an organ at risk, as long as the problem remains. The results indicates that the error in ACE is located in the scatter dose calculations and that the heterogeneity cause ACE to displace the dose.

    The error is thought to be located in the multiple-scattered dose component, which was also shown by Terribilni et al.. A hypothesis is that the problem is caused by the neglected effect of media dependent absorption coefficients in the multiple-scattered dose calculation. A suggested solution, left to be proven, is to use effective attenuation scaling factors.

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    fulltext
  • 203.
    Al-Soubaihi, Rola
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Saoud, K. M.
    Virginia Commonwealth University in Qatar, Libral Arts and Sciences Program, P.O. Box 8095, Doha, Qatar.
    Fei, Ye
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Zar Myint, M. T.
    Department of Physics, College of Science, Sultan Qaboos University, P.O. Box 36, Muscat, PC 123, Oman.
    Saeed, S.
    Department of Chemistry, Paksitan Institute of Engineering and Applied Sciences (PIEAS), PO Nilore, Islamabad, 45650, Pakistan.
    Dutta, Joydeep
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Synthesis of hierarchically porous silica aerogel supported Palladium catalyst for low-temperature CO oxidation under ignition/extinction conditions2020In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 292, article id 109758Article in journal (Refereed)
    Abstract [en]

    Synthesis of well-dispersed palladium nanoparticles within silica aerogel pores with controlled size was carried out using sol-gel synthesis under supercritical ethanol drying. The high concentration of silanol groups on silica (SiO2) surface facilitated a superior palladium (Pd) loading up to 10 wt %. The synthesized Pd/SiO2 nanocomposite aerogels were characterized by X-ray diffraction (XRD), N2 adsorption-desorption, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopic methods. The silica aerogel supported catalysts were found to have a wide pore size distribution. TEM investigations confirmed that Pd nanocrystals were located within the SiO2 microspores and mesopores. The catalyst was evaluated for carbon monoxide (CO) oxidation reaction under ignition/extinction conditions. The synthesized catalyst demonstrated a high catalytic activity at low operating temperatures (<200 °C) compared to unsupported Pd nanoparticles or bare SiO2 aerogels. This enhancement in CO oxidation activity with Pd/SiO2 aerogel catalysts are attributed to the small Pd particles, Pd interaction with the surface of the underlying SiO2 and the better dispersion of Pd particles within the SiO2 pores. Porosity played a more important role during the extinction cycle as a result of the slow dissipation of the heat leading to hysteresis. We demonstrate the influence of porosity of catalyst supports on the size, dispersion, and catalytic activity of Pd nanoparticles.

  • 204.
    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.

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    WO3rapportFinal
  • 205.
    Alvi, Sajid Ali
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Ghamgosar, Pedram
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Rigoni, Federica
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Vomiero, Alberto
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Akhtar, Farid
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Adaptive nanolaminate coating by atomic layer deposition2019In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 692, article id 137631Article in journal (Refereed)
    Abstract [en]

    Atomic layer deposition (ALD) was used to deposit ZnO/Al2O3/V2O5 nanolaminate coatings to demonstrate a coating system with temperature adaptive frictional behaviour. The nanolaminate coating exhibited excellent conformity and crack-free coating of thickness 110 nm over Inconel 718 substrate. The ALD trilayer coating showed a hardness and elastic modulus of 12 GPa and 193 GPa, respectively. High-temperature tribology of the nanolaminate trilayer was tested against steel ball in dry sliding condition at 25 °C (room temperature, RT), 200 °C, 300 °C, and 400 °C. It was found that the nanolaminate coating showed a low coefficient of friction (COF) and wear rate at RT and 300 °C. The trilayer coating was found intact and stable at all temperatures during the friction tests. The adaptability of nanolaminate coating with the temperature was verified by performing the cyclic friction test at 300 °C and RT. The low COF and wear rate had been attributed to the (100) and (002) basal plane sliding of ZnO top layer, and the interlayer sliding of weakly bonded planes parallel to (001) plane in V2O5 bottom layer. Furthermore, even after the removal of ZnO coating during the tribotest, the bottom V2O5 layer coating stabilized the COF and wear rate at RT and 300 °C.

  • 206.
    Alvi, Sajid
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Jarzabek, Dariusz M.
    Department of Mechanics of Materials (ZMM), Institute of Fundamental Technological Research, Polish Academy of Sciences, 02-106 Warsaw, Poland.
    Gilzad Kohan, Mojtaba
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Hedman, Daniel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Jenczyk, Piotr
    Department of Mechanics of Materials (ZMM), Institute of Fundamental Technological Research, Polish Academy of Sciences, 02-106 Warsaw, Poland.
    Natile, Marta Maria
    CNR—Institute of Condensed Matter Chemistry and Technologies for Energy (ICMATE), I-16149 Genoa, Italy. Department of Chemical Sciences, University of Padova, 35131 Padova, Italy.
    Vomiero, Alberto
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Akhtar, Farid
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Synthesis and Mechanical Characterization of a CuMoTaWV High-Entropy Film by Magnetron Sputtering2020In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 12, no 18, p. 21070-21079Article in journal (Refereed)
    Abstract [en]

    Development of high-entropy alloy (HEA) films is a promising and cost-effective way to incorporate these materials of superior properties in harsh environments. In this work, a refractory high-entropy alloy (RHEA) film of equimolar CuMoTaWV was deposited on silicon and 304 stainless-steel substrates using DC-magnetron sputtering. A sputtering target was developed by partial sintering of an equimolar powder mixture of Cu, Mo, Ta, W, and V using spark plasma sintering. The target was used to sputter a nanocrystalline RHEA film with a thickness of ∼900 nm and an average grain size of 18 nm. X-ray diffraction of the film revealed a body-centered cubic solid solution with preferred orientation in the (110) directional plane. The nanocrystalline nature of the RHEA film resulted in a hardness of 19 ± 2.3 GPa and an elastic modulus of 259 ± 19.2 GPa. A high compressive strength of 10 ± 0.8 GPa was obtained in nanopillar compression due to solid solution hardening and grain boundary strengthening. The adhesion between the RHEA film and 304 stainless-steel substrates was increased on annealing. For the wear test against the E52100 alloy steel (Grade 25, 700–880 HV) at 1 N load, the RHEA film showed an average coefficient of friction (COF) and wear rate of 0.25 (RT) and 1.5 (300 °C), and 6.4 × 10–6 mm3/N m (RT) and 2.5 × 10–5 mm3/N m (300 °C), respectively. The COF was found to be 2 times lower at RT and wear rate 102 times lower at RT and 300 °C than those of 304 stainless steel. This study may lead to the processing of high-entropy alloy films for large-scale industrial applications.

  • 207.
    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.

  • 208.
    Amano, Taiju
    et al.
    Tokyo Metropolitan Univ, Dept Phys, Hachioji, Tokyo 1920397, Japan.;Tokyo Inst Technol, Dept Phys, Meguro Ku, Ookayama, Tokyo 1528551, Japan..
    Jido, Daisuke
    Tokyo Metropolitan Univ, Dept Phys, Hachioji, Tokyo 1920397, Japan.;Tokyo Inst Technol, Dept Phys, Meguro Ku, Ookayama, Tokyo 1528551, Japan..
    Leupold, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Nuclear Physics.
    Sum rule for the partial decay rates of bottom hadrons based on the dynamical supersymmetry of the (s)over-bar quark and the ud diquark2022In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 105, no 5, article id L051504Article in journal (Refereed)
    Abstract [en]

    We investigate the weak decays of (B) over bar (0)(s) and Lambda(b) to charm hadrons based on the dynamical supersymmetry between the (s) over bar quark and the ud diquark. We derive a new sum rule relating the decay rates of the processes (B) over bar (0)(s) -> Ds+P-, (B) over bar (0)(s) -> Ds*+P-, and Lambda(b) -> Lambda P-c(-) where P- is a negatively charged meson, such as pi(-) and K-. It is found that the observed decay rates satisfy the sum rule very well. This implies that the supersymmetry between the (s) over bar quark and the ud diquark is also seen in the wave functions of the heavy hadrons and suggests that the ud diquark can be regarded as a valid effective constituent for heavy hadrons.

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    FULLTEXT01
  • 209.
    Amariti, Antonio
    et al.
    Ist Nazl Fis Nucl, Sez Milano, Via Celoria 16, I-20133 Milan, Italy.
    Cassia, Luca
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Physics.
    Garozzo, Ivan
    Ist Nazl Fis Nucl, Sez Milano Bicocca, Piazza Sci 3, I-20126 Milan, Italy;Univ Milano Bicocca, Dipartimento Fis, Piazza Sci 3, I-20126 Milan, Italy.
    Mekareeya, Noppadol
    Ist Nazl Fis Nucl, Sez Milano Bicocca, Piazza Sci 3, I-20126 Milan, Italy;Chulalongkorn Univ, Fac Sci, Dept Phys, Phayathai Rd, Bangkok 10330, Thailand.
    Branes, partition functions, and quadratic monopole superpotentials2019In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 100, no 4, article id 046001Article in journal (Refereed)
    Abstract [en]

    We obtain the brane setup describing 3d N = 2 dualities for USp(2N(c)) and U(Nc) SQCD with monopole superpotentials. This classification follows from a complete analysis of affine and twisted affine compactifications from 4d. The analysis leads to a new duality for the unitary case that has previously been overlooked in the literature. We check this by matching the three-sphere partition function of the two sides of this new duality and find a perfect agreement. Furthermore, we use the partition function to predict new 3d N = 2 dualities for SQCD with monopole superpotentials and tensorial matter.

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    FULLTEXT01
  • 210. Amarouch, Mohamed-Yassine
    et al.
    Kurt, Han
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Delemotte, Lucie
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biophysics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Abriel, Hugues
    Biophysical Characterization of Epigallocatechin-3-Gallate Effect on the Cardiac Sodium Channel Na(v)1.52020In: Molecules, ISSN 1431-5157, E-ISSN 1420-3049, Vol. 25, no 4, article id 902Article in journal (Refereed)
    Abstract [en]

    Epigallocatechin-3-Gallate (EGCG) has been extensively studied for its protective effect against cardiovascular disorders. This effect has been attributed to its action on multiple molecular pathways and transmembrane proteins, including the cardiac Na(v)1.5 channels, which are inhibited in a dose-dependent manner. However, the molecular mechanism underlying this effect remains to be unveiled. To this aim, we have characterized the EGCG effect on Na(v)1.5 using electrophysiology and molecular dynamics (MD) simulations. EGCG superfusion induced a dose-dependent inhibition of Na(v)1.5 expressed in tsA201 cells, negatively shifted the steady-state inactivation curve, slowed the inactivation kinetics, and delayed the recovery from fast inactivation. However, EGCG had no effect on the voltage-dependence of activation and showed little use-dependent block on Na(v)1.5. Finally, MD simulations suggested that EGCG does not preferentially stay in the center of the bilayer, but that it spontaneously relocates to the membrane headgroup region. Moreover, no sign of spontaneous crossing from one leaflet to the other was observed, indicating a relatively large free energy barrier associated with EGCG transport across the membrane. These results indicate that EGCG may exert its biophysical effect via access to its binding site through the cell membrane or via a bilayer-mediated mechanism.

  • 211. 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.

  • 212. 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.

  • 213. 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.

  • 214. 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.

  • 215. 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.

  • 216.
    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, 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.

  • 217.
    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.

  • 218.
    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, Sindh Pakistan.
    Tahira, Aneela
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Solangi, Amber R.
    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. Institute for Microelectronics and Microsystems, National Research Council, Bologna, Italy.
    Ibupoto, Zafar Hussain
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Institute of Chemistry, University of Sindh, Jamshoro, Sindh Pakistan.
    Fatima, Almas
    National Centre of Excellence in Analytical Chemistry, University of Sindh, Jamshoro, Pakistan.
    Vomiero, Alberto
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Department of Molecular Sciences and Nanosystems, Ca' Foscari University of Venice, Via Torino 155, 30172 Venezia Mestre, Italy.
    Functional Nickel Oxide Nanostructures for Ethanol Oxidation in Alkaline Media2020In: Electroanalysis, ISSN 1040-0397, E-ISSN 1521-4109, Vol. 32, no 5, p. 1052-1059Article in journal (Refereed)
    Abstract [en]

    Nickel oxide (NiO) nanostructures are employed in the basic medium for the oxidation of ethanol. A variety of NiO nanostructures are synthesized by wet chemical growth method, using different hydroxide (OH−) ion sources, particularly from ammonia, hexamethylenetetramine, urea and sodium hydroxide. The use of urea as (OH−) ion source results in flower‐like NiO structures composed by extremely thin nanowalls (thickness lower than 10 nm,), which demonstrated to be the most active for ethanol oxidation. All the samples exhibit NiO cubic phase, and no other impurity was detected. The cyclic voltammetry (CV) curves of NiO nanostructures were found linear over the concentration range 0.1–3.5 mM (R2=0.99) of ethanol, with the limit of detection estimated to be 0.013 mM for ethanol. The NiO nanostructures exhibit a selective signal towards ethanol oxidation in the presence of different members of alcohol family. The proposed NiO nanostructures showed a significant practicality for the reproducible and sensitive determination of ethanol from brandy, whisky, mixture of brandy and rum, and vodka samples. The nanomaterial was used as a surface modifying agent for the glassy carbon electrode and it showed a stable electro‐oxidation activity for the ethanol for 16 days. These findings indicate that the presented NiO nanomaterial can be applied in place of noble metals for ethanol sensing and other environmental applications (like fuel cells).

  • 219.
    Amselem, Elias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular Systems Biology.
    Broadwater, Bo
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Haevermark, Tora
    Uppsala University, Science for Life Laboratory, SciLifeLab. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology.
    Johansson, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular Systems Biology.
    Elf, Johan
    Uppsala University, Science for Life Laboratory, SciLifeLab. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular Systems Biology.
    Real-time single-molecule 3D tracking in E. coli based on cross-entropy minimization2023In: Nature Communications, E-ISSN 2041-1723, Vol. 14, no 1, article id 1336Article in journal (Refereed)
    Abstract [en]

    Reaching sub-millisecond 3D tracking of individual molecules in living cells would enable direct measurements of diffusion-limited macromolecular interactions under physiological conditions. Here, we present a 3D tracking principle that approaches the relevant regime. The method is based on the true excitation point spread function and cross-entropy minimization for position localization of moving fluorescent reporters. Tests on beads moving on a stage reaches 67 nm lateral and 109 nm axial precision with a time resolution of 0.84 ms at a photon count rate of 60 kHz; the measurements agree with the theoretical and simulated predictions. Our implementation also features a method for microsecond 3D PSF positioning and an estimator for diffusion analysis of tracking data. Finally, we successfully apply these methods to track the Trigger Factor protein in living bacterial cells. Overall, our results show that while it is possible to reach sub-millisecond live-cell single-molecule tracking, it is still hard to resolve state transitions based on diffusivity at this time scale.

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  • 220.
    Anand, Srinivasan
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
    Shahid, Naeem
    KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
    Naureen, Shagufta
    KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
    Li, Mingyu
    KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA. Zhejiang University, Hangzhou, China.
    Swillo, Marcin
    KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
    InP-based photonic crystal waveguide filters2010In: 2010 Asia Communications and Photonics Conference and Exhibition, ACP 2010, 2010, p. 104-105Conference paper (Refereed)
  • 221.
    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.

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  • 222.
    Anderson, D.
    et al.
    Chalmers University of Technology, Sweden.
    Lisak, M.
    Chalmers University of Technology, Sweden.
    Anders, Berntson
    Ericsson Telcom AB, Sweden.
    A variational approach to nonlinear evolution equations in optics2001In: Pramana (Bangalore), ISSN 0304-4289, E-ISSN 0973-7111, Vol. 57, no 5-6, p. 917-936Article in journal (Refereed)
    Abstract [en]

    The use of direct variational methods based on Rayleigh-Ritz optimization for finding approximate solutions to various nonlinear evolution equations was presented. The main advantage of the approach is that it provides simple and explicit expressions for physically relevant quantities where exact analytical solutions are not available. It is found that the given method is flexible and can be applied to stationary and dynamical problems.

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

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

  • 224.
    Anderson, Lara B.
    et al.
    Virginia Tech, Dept Phys, Robeson Hall, Blacksburg, VA 24061 USA..
    Gray, James
    Virginia Tech, Dept Phys, Robeson Hall, Blacksburg, VA 24061 USA..
    Karkheiran, Mohsen
    Ctr Theoret Phys Universe, Inst Basic Sci, Daejeon 34051, South Korea..
    Oehlmann, Paul-Konstantin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Physics.
    Raghuram, Nikhil
    Virginia Tech, Dept Phys, Robeson Hall, Blacksburg, VA 24061 USA..
    P-1-fibrations in F-theory and string dualities2022In: Pure and Applied Mathematics Quarterly, ISSN 1558-8599, E-ISSN 1558-8602, Vol. 18, no 4, p. 1264-1354Article in journal (Refereed)
    Abstract [en]

    In this work, we study F-theory compactifications on manifolds. Such geometries, which we study in both 4- and 6dimensions, are both ubiquitous within the set of Calabi-Yau manifolds and play a crucial role in heterotic/F-theory duality. We discuss the most general formulation of P1-bundles of this type, as well as fibrations which degenerate at higher codimension loci. In the course of this study, we find a number of new phenomena. For example, in both 4- and 6-dimensions we find transitions whereby the base of a P1-bundle can change nature, or "jump ", at certain loci in complex structure moduli space. We discuss the implications of this jumping for the associated heterotic duals. We argue that P1-bundles with only rational sections lead to heterotic duals where the Calabi-Yau manifold is elliptically fibered over the section of the P1 bundle, and not its base. As expected, we see that degenerations of the P1 fibration of the F-theory base correspond to 5-branes in the dual heterotic physics, with the exception of cases in which the fiber degenerations exhibit monodromy. Along the way, we discuss a set of useful formulae and tools for describing F-theory compactifications on this class of Calabi-Yau manifolds.

  • 225. 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.

  • 226.
    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.

  • 227.
    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.

  • 228.
    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.

  • 229.
    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
  • 230.
    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.

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  • 231.
    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.

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  • 232.
    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.

  • 233.
    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).

                 

  • 234.
    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.

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    Design_of_the_Modelica_Library_VehProLib_with_Non-ideal_Gas_Models_in_Engines
  • 235.
    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.

    Download (pdf)
    abstract
  • 236.
    Andersson, Ida
    Jönköping University, School of Education and Communication.
    Energibegreppet i geografiämnet sett ur en naturvetares perspektiv2022Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This study deals with the energy concept in the school subject of geography. The energy concept is complex, not least because it is treated in different contexts with different meanings. As a science teacher, you want to understand the students' learning about science concepts, also such learning that is outside their subject. The aim of the qualitative study is therefore to investigate how the energy concept is treated in the subject of geography in order to gain a deeper understanding of how science teaching and geography teaching can complement each other. Six social science teachers in middle school were interviewed about their use of the energy concept. Their statements were thematized and compared with the four key ideas about the energy concept that Duit highlights as central from a scientific perspective. Three key ideas could be identified in the teachers' descriptions of how they treat the energy concept in the subject of geography. Three themes could also be distinguished in the data. The study indicates that the energy concept is treated in the subject of geography with some base in energy transformation and energy transfer. That makes it possible to work interdisciplinary regarding the energy concept.   

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    fulltext
  • 237. 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.

  • 238.
    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.

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    Ion recombination in liquid ionization chambers (kappa)
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    Ion recombination in liquid ionization chambers (omslag)
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    Ion recombination in liquid ionization chambers (spikblad)
  • 239.
    Andersson, Jonas
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Radiation Dosimetry for CBCT – Quality Control and Applied Dosimetry2015Conference paper (Other academic)
    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.

  • 240.
    Andersson, Jonas
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology.
    Granberg, Christoffer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology.
    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 / ESI-0064, EuroSafe Imaging , 2018Conference paper (Refereed)
  • 241.
    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.

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  • 242.
    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.

  • 243.
    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.

  • 244.
    Andersson, Jonas
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Pavlicek, William
    Al-Senan, Rani
    Bolch, Wesley
    Bosmans, Hilde
    Cody, Dianna
    Dixon, Robert
    Colombo, Paola
    Dong, Frank
    Edyvean, Sue
    Jansen, Jan
    Kanal, Kalpana
    Leng, Shuai
    Liang, Qing
    McCullough, Cynthia
    McDonagh, Ed
    McNitt-Gray, Michael
    Paden, Robert
    Rehani, Madan
    Samei, Ehsan
    Sechopoulos, Ioannis
    Supanich, Mark
    Theodorakou, Christine
    Tian, Xiaoyu
    Torresin, Alberto
    Trianni, Annalisa
    Zamora, David
    Zanca, Federica
    Estimating Patient Organ Dosewith Computed Tomography: A Review of Present Methodologyand Required DICOM Information: A Joint Report ofAAPM Task Group 246 and the European Federationof Organizations for Medical Physics (EFOMP)2019Report (Refereed)
    Abstract [en]

    The purpose of this report is (1) to summarize the current state of the art in estimating organ doses from CT examinations and (2) to outline a road map for standardized reporting of essential parameters necessary for estimation of organ doses from CT imaging in the DICOM standard. To address these purposes, the report includes a comprehensive discussion of (1) the various metrics, concepts, and methods that may be used to achieve estimates of patient organ dose and (2) the DICOM standard for CT.

    This Joint Report of the American Association of Physicists in Medicine (AAPM) Task Group 246 and the European Federation of Organizations for Medical Physics (EFOMP) contains three major sections and an appendix. Section 2 (with additional material in the appendix) provides a review of basic CT dosimetry metrics, their uses and limitations in the context of organ dosimetry, and the DICOM information currently associated with parameters that affect CT dose metrics and, consequently, organ dose estimates. Section 3 provides an overview of present and emerging organ dose estimation methods reported in the literature, e.g., for the lens of the eye, breast tissue, colon, and skin. Finally, the report concludes with section 4, which provides a discussion on the sources and magnitudes of uncertainty for different organ dose estimation methods.

    Ongoing efforts to facilitate routine standardized estimation of patient organ doses from CT are dependent, in large part, on the availability of the DICOM Radiation Dose Structured Report (RDSR), which provides a host of information pertinent to radiation dose calculations. This report, therefore, includes detailed information on DICOM header content in CT images and how it can be used in organ dose estimation. The RDSR markedly expands the abilities of the clinical medical physicist to estimate doses at the patient, device, and protocol level

  • 245.
    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.

  • 246.
    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.

  • 247.
    Andersson, L.C.
    et al.
    Luleå University of Technology.
    Hauska, Hans
    Luleå University of Technology.
    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

  • 248.
    Andersson, L.C.
    et al.
    Luleå University of Technology.
    Hauska, Hans
    Luleå University of Technology.
    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)
  • 249.
    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.

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  • 250.
    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.

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