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  • 251. Andersson, Martin
    et al.
    Jönsson, Per
    Malmö högskola, School of Teacher Education (LUT), Nature-Environment-Society (NMS).
    Sabel, Hans
    Hyperfine induced interference effects in the 4s4d 3D2–4s4f 3F2,3 transitions in Ga II2006In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 39, no 20, p. 4239-4247Article in journal (Refereed)
    Abstract [en]

    We report relativistic multiconfiguration Dirac–Hartree–Fock calculations of transitions between the hyperfine levels of 4s4f 3F2,3 and 4s4d 3D2 in Ga II. The capacity of two newly developed programs connected to the graspVU package for generating synthetic spectra is explored. The obtained theoretical spectra are compared to Fourier transform spectra and good agreement is found. The importance of hyperfine induced interference effects for the 4s4d 3D2–4s4f 3F2 transitions is pointed out, and the gf values for all the hyperfine transitions are given.

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  • 252.
    Andersson, Mike
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    SiC based field effect sensors and sensor systems for combustion control applications2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

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

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

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

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

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

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

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

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

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  • 253.
    Andersson, O.
    et al.
    Department of Experimental Physics, Umeå University, S-90187 Umeå, Sweden.
    Soldatov, Alexander
    Department of Experimental Physics, Umeå University, S-90187 Umeå, Sweden.
    Sundqvist, B.
    Department of Experimental Physics, Umeå University, S-90187 Umeå, Sweden.
    Thermal conductivity of C60 at pressures up to 1 GPa and temperatures in the 50-300 K range1996In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 54, no 5, p. 3093-3100Article in journal (Refereed)
  • 254. Andersson, O.
    et al.
    Soldatov, Alexander
    Sundqvist, B.
    Thermal conductivity of C60 under high pressure1995In: Science and technology of fullerene materials: symposium held November 28 - December 2, 1994, Boston, Massachusetts, U.S.A / [ed] Patrick Bernier, Pittsburgh, Pa: Materials Research Society, 1995, p. 549-554Conference paper (Refereed)
  • 255. Andersson, O.
    et al.
    Soldatov, Alexander
    Sundqvist, Bertil
    Reorientational relaxation in C60 following a pressure induced change in the pentagon/hexagon equilibrium ratio1995In: Physics Letters A, ISSN 0375-9601, E-ISSN 1873-2429, Vol. 206, no 3-4, p. 260-264Article in journal (Refereed)
    Abstract [en]

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

  • 256.
    Andersson, Ole
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Badziąg, Piotr
    Stockholm University, Faculty of Science, Department of Physics.
    Dumitru, Irina
    Stockholm University, Faculty of Science, Department of Physics.
    Cabello, Adán
    Device-independent certification of two bits of randomness from one entangled bit and Gisin's elegant Bell inequality2018In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 97, no 1, article id 012314Article in journal (Refereed)
    Abstract [en]

    We prove that as conjectured by Acín et al. [Phys. Rev. A 93, 040102(R) (2016)], two bits of randomness can be certified in a device-independent way from one bit of entanglement using the maximal quantum violation of Gisin's elegant Bell inequality. This suggests a surprising connection between maximal entanglement, complete sets of mutually unbiased bases, and elements of symmetric informationally complete positive operator-valued measures, on one side, and the optimal way of certifying maximal randomness, on the other.

  • 257.
    Andersson, Ole
    et al.
    Dept. of Physics, Stockholm University, Sweden.
    Bengtsson, Ingemar
    Dept. of Physics, Stockholm University, Sweden.
    Ericsson, Marie
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Sjöqvist, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala universitet.
    Geometric phases for mixed states of the Kitaev chain2016In: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 374, no 2069, article id 20150231Article in journal (Refereed)
    Abstract [en]

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

  • 258.
    Andersson, Ole
    et al.
    Dept. of Physics, Stockholm University, Sweden.
    Bengtsson, Ingemar
    Dept. of Physics, Stockholm University, Sweden.
    Ericsson, Marie
    Uppsala universitet, Kvantkemi.
    Sjöqvist, Erik
    Uppsala universitet, Institutionen för fysik och astronomi.
    Geometric phases for mixed states of the Kitaev chain2016In: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 374, no 2069, article id 20150231Article in journal (Refereed)
    Abstract [en]

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

  • 259.
    Andersson, Olof
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Kemerink, Martijn
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering. Heidelberg Univ, Germany.
    Enhancing Open-Circuit Voltage in Gradient Organic Solar Cells by Rectifying Thermalization Losses2020In: Solar RRL, E-ISSN 2367-198X, Vol. 4, no 12, article id 2000400Article in journal (Refereed)
    Abstract [en]

    In virtually all solar cells, including optimized ones that operate close to the Shockley-Queisser (SQ) limit, thermalization losses are a major, efficiency-limiting factor. In typical bulk heterojunction organic solar cells, the loss of the excess energy of photocreated charge carriers in the disorder-broadened density of states is a relatively slow process that for commonly encountered disorder values takes longer than the charge extraction time. Herein, it is demonstrated by numerical modeling that this slow relaxation can be rectified by means of a linear gradient in the donor:acceptor ratio between anode and cathode. For experimentally relevant parameters, open-circuit voltage (VOC) enhancements up to approximate to 0.2 V in combination with significant enhancements in fill factor as compared to devices without gradient are found. The VOC enhancement can be understood in terms of a simple nonequilibrium effective temperature model. Implications for existing and future organic photovoltaics (OPV) devices are discussed.

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  • 260.
    Andersson, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Holcombe, Scott
    Halden Reactor Project.
    Tverberg, Terje
    Halden Reactor Project.
    Inspection of LOCA Test Rod IFA-650.15 Using Gamma Emission Tomography2016Report (Other academic)
  • 261.
    Andersson, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Sundén, E. Andersson
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Jacobsson Svärd, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Sjöstrand, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Correction for dynamic bias error in transmission measurements of void fraction2012In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 83, no 12, p. 125110-Article in journal (Refereed)
    Abstract [en]

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

  • 262.
    Andersson, Sabina
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Simulation challenges in robotic grasping2021Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Grasping and dexterous manipulation is a huge area in the current robotic research field. Traditionally in industrial environments, robots are customized for a certain task and work well with repetitive movements where the entire process is predetermined and deterministic. The possibility for a robot to adapt to its surroundings and manipulate objects with unknown properties is very limited and requires new models and methods. It is advantageous to explore and test new algorithms and models in a simulated environment before building physical systems. This thesis focuses on making the development, design and control of dexterous robot hands easier by exploring the benefits and challenges to use simulation in Algoryx's physics engine AGX Dynamics for experimentation and evaluation of design, motion planning, contact models, geometry, etc. The goal is to simulate complex grasping situations in AGX Dynamics and to build knowledge about contact mechanics to fully capture the dynamics of grasping in simulation. The work consists of validating the simulation library with regards to fundamental physics characteristics involved in grasping by a series of benchmark tests. The validation process aims to verify the models and numerical methods in AGX Dynamics to ensure sim2real transfer. The work has exposed friction as one of the biggest challenges in simulation. Developments of the current friction models that better represent the reality have been implemented and tested in AGX. They both show promising results for further development.

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  • 263.
    Andersson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Physics Didactics.
    A conference as examination: Meeting a professional scientist culture2008In: Presentation at the Scholarship of University Teaching and Learning National Workshop III - Teachers developing their practice using science education research, Göteborg, Sweden, 23-24 October, 2008Conference paper (Other academic)
  • 264.
    Andersson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Physics Didactics.
    Acquisition of a collection in context: A case study of the Uppsala Cabinet of Physics2006In: Proceedings of the XXV Scientific Instrument Symposium: East and West, The Common European Heritage / [ed] Ewa Wyka, Maciej Kluza, Anna Karolina Zawada, 2006Conference paper (Refereed)
  • 265.
    Andersson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Physics Didactics.
    Bitar av en lärarroll: "Jag är lite som ett utrotningshotat djur - jag är fysiklärare."2015In: LMNT-nytt, ISSN 1402-0041, no 1, p. 8-10Article in journal (Other (popular science, discussion, etc.))
  • 266.
    Andersson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics Didactics.
    Conference as examination: Meeting a professional scientist culture2008Conference paper (Other academic)
  • 267.
    Andersson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Physics Didactics.
    Experimentalfysiken - Motiven bakom 1700-talets förändrade fysikundervisning2007Other (Other (popular science, discussion, etc.))
  • 268.
    Andersson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Physics Didactics.
    'Fysikshow?' eller 'Varför måste fysik alltid vara så roligt?'2007In: Presentation at "Fysikdagarna 2007", Uppsala Universitet, 29-30 October., 2007Conference paper (Other (popular science, discussion, etc.))
  • 269.
    Andersson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Physics Didactics.
    Hur ger man civilingenjörsstudenter positiva upplevelser av utbildningens första termin?2008Conference paper (Other academic)
  • 270.
    Andersson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics Didactics.
    Hur tänker studenterna? Växelspelet mellan individer och utbildningsdiskursen.2008Other (Other academic)
  • 271.
    Andersson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Physics Didactics.
    Physics Education in Sweden: An Overview2008In: Presentation at the European Committee for Future Accelerators R-ECFA Meeting, Uppsala, Sweden, 9-10 May, 2008Conference paper (Other academic)
  • 272.
    Andersson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Physics Didactics.
    Undervisning och lärande ur ett identitetsperspektiv2008In: Presentation to the 'Mentorskollegiet', Uppsala University, 16 October, 2008Conference paper (Other academic)
  • 273.
    Andersson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Physics Didactics.
    Using Historical Collections when Teaching a Broadened Science Curriculum2008In: Rittenhouse - The Journal of the American Scientific Enterprise, Vol. 22, no 2, p. 114-131Article in journal (Refereed)
  • 274.
    Andersson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics Didactics. Fysikens didaktik.
    Using Historical Collections when Teaching a Broadened Science Curriculum.2007In: International Workshop on Historic Scientific Instrument Collections in the University, Oxford, Mississippi, 2007Conference paper (Refereed)
  • 275.
    Andersson, Staffan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Physics Didactics.
    Andersson Chronholm, Jannika
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Physics Didactics.
    Retentionsbefrämjande introduktionskurs till universitetsstudier.2010Conference paper (Other academic)
    Abstract [sv]

    Studenters första tid vid universitetet är mycket viktig, då forskningen betonar att grunden läggs för studenternas fortsatta lärande och deras retention inom högre utbildning. Samtidigt är det en period då många studenter avbryter sina studier. I Sverige har mer än 10 % av nybörjarna på utbildningsprogram försvunnit till den andra terminen (SCB, 2009).

    På basårsutbildningen vid Uppsala universitet fortsatte omkring 80 % av nybörjarna till utbildningens andra termin (2002-2007). Förlusten av studenter förklarades först med att studenterna var ”svaga” och en kurs i studieteknik introducerades hösten 2007. Ingen skillnad sågs dock för studentretentionen till våren 2008.

    Höstterminen 2008 infördes därför en nyutvecklad delkurs – Introduktion till universitetsstudier. Kursen tar ett bredare grepp och baseras på forskning kring lärande och retention inom högre utbildning. Studenters beslut att avbryta sina studier har visat sig till stor del bero på växelspelet mellan dem och deras upplevelse av universitetsmiljön och yttre faktorer (se exempelvis Cabrera, Castaneda, Nora & Hengstler, 1992). De bakomliggande upplevelserna kan sägas vara av fyra olika slag (Yorke & Longden, 2004). Studenter som lämnat utbildningen har upplevt att de:

    1)      inte valt rätt utbildning. 2) inte klarar av utbildningen. 3) inte passar in på utbildningen. 4) måste lämna utbildningen på grund av yttre faktorer.

    Den tidigare kursen i studieteknik hade som utgångspunkt att studenterna hade problem att klara av utbildningen, vilket delvis berör andra punkten. I utformningen den nya kursen utgick vi från alla dessa punkter, men med en tonvikt på den andra och tredje.

    Introduktionskursens främsta mål blev att underlätta studenternas introduktion till universitetet, synliggöra aspekter av den universitetstypiska studiekulturen och få dem att känna tillhörighet. Studenterna arbetade också med uppläggningen för sina fortsatta studier samt studieteknik kopplad till andra delkurser.

    Den nya kursens mål, att öka studentretentionen, lyckades över förväntan. Av de nybörjare som deltog i introduk­tionskursen 2008 eller 2009 fortsatte 94 % till vårterminen. För de 117 nybörjare som valde att inte läsa kursen är mot­svarande siffra 78 %.

    I presentationen kommer vi att ge en kort översikt av bakomliggande forskning, presentera vårt kursupplägg och diskutera kursens effekter.

    Referenser

    Cabrera, A. F., Castaneda, M. B., Nora, A. & Hengstler, D. (1992). The Convergence between Two Theories of College Persistence. Journal of Higher Educ.,63(2), 143-164.

    SCB (2009) Utbildningsstatistisk årsbok 2010 Tabeller, Örebro:SCB

    Yorke, M. & Longden, B. (2004). Retention and Student Success in Higher Education. Glasgow: Open University Press.

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  • 276.
    Andersson, Staffan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Physics Didactics.
    Forsman, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Physics Didactics.
    Linder, Cedric
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Physics Didactics.
    ”Det löser sig under studiernas gång”2010Conference paper (Other academic)
    Abstract [sv]

    Studenters förhållningssätt till högre studier präglas allt mer av identitetsbekräftelse (Schreiner, 2006) och utbildningskon­sumtion (Friis Johannsen, 2007). För många är studierna ett medel för att utveckla eller manifestera en identitet. Schrei­ner (2006) sammanfattar: When young people choose an education or profession, they express at the same time key components of their identity.

    Andelen nybörjarstudenter som tagit civilingenjörsexamen efter fem år halverades från 38% i 1980-talets mitt till 19% vid 2000-talets början. Andelen som tagit examen efter sju år har däremot bara minskat från 60% till 55%. Idag tar alltså nästan lika många studenter en civilingenjörsexamen, men de tar längre tid på sig. Med resultat från olika studier vill vi illustrera hur det förändrade förhållningssättet bidrar till att det tar allt längre tid för civilingenjörsstudenter att nå sin examen. Att finna ett yrke har för många blivit något som ”löser sig under studiernas gång”.

    En enkätstudie för nybörjare på ett civilingenjörsprogram i teknisk fysik visade att 65 % hade som främsta mål att just gå utbildningen. Övriga hade mer långsiktiga mål, som exempelvis yrkesarbete.

    Flera studenter uttrycker en osäkerhet i att välja rätt i det stora utbildningsutbudet med fler än 65 olika civilingenjörs­program och otaliga andra utbildningar att välja på. Ett sätt att hanterar detta utbud är mobilitet mellan utbildningar.

    Analys av studiebanor för en kull på teknisk fysik från 2006 visade att 30 % av studenterna läst vid andra utbildnings-program tidigare och/eller lämnade programmet för att läsa ett annat.

    En intervjustudie visade att många av studenterna ansåg att det inledningsvis var minst lika viktigt att engagera sig i kår, studentliv och annat för att utveckla sig som person. Senare under studietiden kunde man fokusera sig, hitta en inriktning och avsluta studierna.

    Den inriktning som studenterna vill ha finns inte alltid inom civilingenjörsprogrammens struktur. Därför väljer de att bredda sig med andra kurser, exempelvis i ekonomi, språk, juridik och datavetenskap.

    Detta är några faktorer som bidrar till att tiden som studenterna behöver för att nå sin civilingenjörsexamen ökar. Dagens studenter läser allt oftare främst för att ”bli någon” och det är något som ofta tar både längre tid och andra vägar än vad de som planerat utbildningarna förväntat sig.

    Referenser

    Friis Johannsen, B. (2007). Attrition in University Physics. Uppsala University, Uppsala.

    Schreiner, C. (2006) EXPLORING A ROSE-GARDEN Norwegian youth’s orientations towards science – seen as signs of late modern identities. Oslo University, Oslo.

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  • 277.
    Andersson, Staffan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Physics Didactics.
    Linder, Cedric
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Physics Didactics.
    Motives and achievements of first year students in the masters programme in Engineering Physics at Uppsala University2008In: Paper presented at the Engineering Education Development Conference, Royal Institute of Technology, Stockholm, Sweden, 26-27 November., 2008Conference paper (Refereed)
  • 278.
    Andersson, Staffan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Physics Didactics.
    Linder, Cedric
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Physics Didactics.
    Relations between motives, academic achievement and retention in the first year of a master programme in Engineering Physics2009In: Paper presented at the ESERA (European Science Education Research Association) Conference, Istanbul, Turkey, 31 August - 4 September, 2009Conference paper (Refereed)
  • 279.
    Andersson, Staffan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Physics Didactics.
    Linder, Cedric
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Physics Didactics.
    Relations between motives, academic achievement and retention in the first year of a master programme in Engineering Physics.2010In: Contemporary Science Education Research: Learning and Assessment. / [ed] G. Çakmakci & M. F. Tasar, Ankara: Pegem Akademi. , 2010, p. 123-128Chapter in book (Other academic)
  • 280.
    Andersson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Physics Didactics.
    Problemkällor i optikundervisning och dess lösningar på Uppsala Universitet2022Independent thesis Advanced level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Bristande kompetensnivå när studenterna når mer avancerade kurser inom optik tyder på att universitetet har ett problem i upplägget av detta ämne. Denna studie djupdyker in i den första optikkursen som ges på Uppsala Universitet, “Vågor och Optik” för Fysikkandidater och Civilingenjörer i vissa program.

    Genom att delta på laborationer, analysera kursutvärderingar och uppgifter som ges under kursens gång kan tydliga problem identifieras och bland annat ge en insikt i studenternas eget perspektiv på kursen. 

    För att sedan åtgärda dessa problem undersöks ett antal alternativa sätt att bedriva undervisningen med ett speciellt intresse av digitala hjälpmedel då denna studie bidrar med en vetenskaplig grund till ett parallellt projekt att utveckla en pedagogisk app för att ytterligare förbättra utbildningen.

    Studien avslutas sedan med sju steg för att förbättra kursen genom att åtgärda de problem som identifierats i kursen.

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  • 281.
    Andisheh, Bahram
    Stockholm University, Faculty of Science, Department of Physics.
    Improving the therapeutic ratio of stereotactic radiosurgery and radiotherapy2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    New methods of high dose delivery, such as intensity modulated radiation therapy (IMRT), stereotactic radiation therapy (SRT) or stereotactic radiosurgery (SRS), hadron therapy, tomotherapy, etc., all make use of a few large fractions. To improve these treatments, there are three main directions: (i) improving physical dose distribution, (ii) optimizing radiosurgery dose-time scheme and (iii) modifying dose response of tumors or normal tissues.

    Different radiation modalities and systems have been developed to deliver the best possible physical dose to the target while keeping radiation to normal tissue minimum. Although applications of radiobiological findings to clinical practice are still at an early stage, many studies have shown that   sublethal radiation damage repair kinetics plays an important role in tissue response to radiation.

    The purpose of the present thesis is to show how the above-mentioned directions could be used to improve treatment outcomes with special interest in radiation modalities and dose-time scheme, as well as radiobiological modeling. Also for arteriovenous malformations (AVM), the possible impact of AVM network angiostructure in radiation response was studied.

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    fulltext
  • 282.
    Andresen, Juan Carlos
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Condensed Matter Theory. Theoretische Physik, ETH Zurich, Zurich, Switzerland.
    Pramudya, Yohanes
    Katzgraber, Helmut G.
    Thomas, Creighton K.
    Zimanyi, Gergely T.
    Dobrosavljevic, V.
    Charge avalanches and depinning in the Coulomb glass: The role of long-range interactions2016In: Physical Review B, ISSN 2469-9950, Vol. 93, no 9, article id 094429Article in journal (Refereed)
    Abstract [en]

    We explore the stability of far-from-equilibrium metastable states of a three-dimensional Coulomb glass at zero temperature by studying charge avalanches triggered by a slowly varying external electric field. Surprisingly, we identify a sharply defined dynamical ("depinning") phase transition from stationary to nonstationary charge displacement at a critical value of the external electric field. Using particle-conserving dynamics, scale-free system-spanning avalanches are observed only at the critical field. We show that the qualitative features of this depinning transition are completely different for an equivalent short-range model, highlighting the key importance of long-range interactions for nonequilibrium dynamics of Coulomb glasses.

  • 283. Andreyev, A. N.
    et al.
    Huyse, M.
    Van Duppen, P.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Liotta, Roberto J.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Antalic, S.
    Ackermann, D.
    Franchoo, S.
    Heßberger, F. P.
    Hofmann, S.
    Kojouharov, I.
    Kindler, B.
    Kuusiniemi, P.
    Lesher, S. R.
    Lommel, B.
    Mann, R.
    Nishio, K.
    Page, R. D.
    Streicher, B.
    Šáro, Š.
    Sulignano, B.
    Wiseman, D.
    Wyss, Ramon A .
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Signatures of the Z=82 shell closure in alpha-decay process2013In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 110, no 24, article id 242502Article in journal (Refereed)
    Abstract [en]

    In recent experiments at the velocity filter Separator for Heavy Ion reaction Products (SHIP) (GSI, Darmstadt), an extended and improved set of α-decay data for more than 20 of the most neutron-deficient isotopes in the region from lead to thorium was obtained. The combined analysis of this newly available α-decay data, of which the Po186 decay is reported here, allowed us for the first time to clearly show that crossing the Z=82 shell to higher proton numbers strongly accelerates the α decay. From the experimental data, the α-particle formation probabilities are deduced following the Universal Decay Law approach. The formation probabilities are discussed in the framework of the pairing force acting among the protons and the neutrons forming the α particle. A striking resemblance between the phenomenological pairing gap deduced from experimental binding energies and the formation probabilities is noted. These findings support the conjecture that both the N=126 and Z=82 shell closures strongly influence the α-formation probability.

  • 284. Andreyev, A. N.
    et al.
    Huyse, M.
    Van Duppen, P.
    Weissman, L.
    Ackermann, D.
    Gerl, J.
    Hessberger, F. P.
    Hofmann, S.
    Kleinbohl, A.
    Munzenberg, G.
    Reschitko, S.
    Schlegel, C.
    Schaffner, H.
    Cagarda, P.
    Matos, M.
    Saro, S.
    Keenan, A.
    Moore, C. J.
    O'Leary, C. D.
    Page, R. D.
    Taylor, M. J.
    Kettunen, H.
    Leino, M.
    Lavrentiev, A.
    Wyss, Ramon
    KTH, Superseded Departments (pre-2005), Physics. Department of Technology, Kalmar University, Box 905, 391 29 Kalmar, Sweden.
    Heyde, K.
    The discovery of a prolate-oblate-spherical shape triple of spin 0(+) states in the atomic nucleus Pb-1862001In: Nuclear Physics A, ISSN 0375-9474, E-ISSN 1873-1554, Vol. 682, p. 482C-486CArticle in journal (Refereed)
    Abstract [en]

    Two excited J(pi)=0(+) states in Pb-186 populated in the a-decay of Po-190 have been identified through alpha -particle/conversion electron coincidences in an experiment at the velocity filter SHIP. The parent Po-190 nuclei have been produced in the Nd-142(Cr-52,4n)Po-190 complete fusion reaction, alpha -particle energies and branching ratios have been measured and hindrance factors were deduced. The observed states have been interpreted as the band heads of the known prolate and (yet unobserved) oblate rotational bands in Pb-186.

  • 285. Andrievsky, Alexander
    et al.
    Brandenburg, Axel
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA. Department of Astronomy, Stockholm University, AlbaNova University Center, Stockholm, Sweden.
    Noullez, Alain
    Zheligovsky, Vladislav
    Negative magnetic eddy diffusivities from the test-field method and multiscale stability theory2015In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 811, no 2, article id 135Article in journal (Refereed)
    Abstract [en]

    The generation of a large-scale magnetic field in the kinematic regime in the absence of an alpha-effect is investigated by following two different approaches: the test-field method and the multiscale stability theory relying on the homogenization technique. Our computations of the magnetic eddy diffusivity tensor of the parity-invariant flow IV of G. O. Roberts and the modified Taylor-Green flow confirm the findings of previous studies. and also explain some of their apparent contradictions. The two flows have large symmetry groups; this is used to considerably simplify the eddy diffusivity tensor. Finally, a new analytic result is presented: upon expressing the eddy diffusivity tensor in terms of solutions to auxiliary problems for the adjoint operator, we derive relations between the magnetic eddy diffusivity tensors that arise for mutually reverse small-scale flows v(x) and - v(x).

  • 286.
    Angelopoulou, Michailia
    et al.
    NCSR Demokritos, Inst Nucl & Radiol Sci & Technol Energy & Safety, Aghia Paraskevi 15341, Greece..
    Makarona, Eleni
    NCSR Demokritos, Inst Nanosci & Nanotechnol, Aghia Paraskevi 15341, Greece..
    Salapatas, Alexandros
    NCSR Demokritos, Inst Nanosci & Nanotechnol, Aghia Paraskevi 15341, Greece..
    Misiakos, Konstantinos
    NCSR Demokritos, Inst Nanosci & Nanotechnol, Aghia Paraskevi 15341, Greece..
    Synolaki, Evgenia
    Biomed Res Fdn Acad Athens, Ctr Clin Expt Surg & Translat Res, Athens 11527, Greece..
    Ioannidis, Anastasios
    Univ Peloponnese, Fac Hlth Sci, Dept Nursing, Tripoli 22100, Greece..
    Chatzipanagiotou, Stylianos
    Ritvos, Mikael A.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH). Natl & Kapodistrian Univ Athens, Aeginit Hosp, Med Sch, Dept Med Biopathol & Clin Microbiol, Athens 11528, Greece.;Univ Helsinki, Fac Med, Dept Physiol, Helsinki 00014, Finland.;Nord SARS Response AB, S-19455 Stockholm, Sweden..
    Pasternack, Arja
    Natl & Kapodistrian Univ Athens, Aeginit Hosp, Med Sch, Dept Med Biopathol & Clin Microbiol, Athens 11528, Greece..
    Ritvos, Olli
    Natl & Kapodistrian Univ Athens, Aeginit Hosp, Med Sch, Dept Med Biopathol & Clin Microbiol, Athens 11528, Greece..
    Petrou, Panagiota S.
    NCSR Demokritos, Inst Nucl & Radiol Sci & Technol Energy & Safety, Aghia Paraskevi 15341, Greece.;NCSR Demokritos, INRASTES, Res Immunoassays Immunosensors Lab, Aghia Paraskevi 15341, Greece..
    Kakabakos, Sotirios E.
    Directly immersible silicon photonic probes: Application to rapid SARS-CoV-2 serological testing br2022In: Biosensors & bioelectronics, ISSN 0956-5663, E-ISSN 1873-4235, Vol. 215, article id 114570Article in journal (Refereed)
    Abstract [en]

    Silicon photonic probes based on broad-band Mach-Zehnder interferometry are explored for the first time as directly immersible immunosensors alleviating the need for microfluidics and pumps. Each probe includes two U- shaped waveguides allowing light in- and out-coupling from the same chip side through a bifurcated fiber and a mechanical coupler. At the opposite chip side, two Mach-Zehnder interferometers (MZI) are located enabling real-time monitoring of binding reactions by immersion of this chip side into a sample. The sensing arm windows of the two MZIs have different length resulting in two distinct peaks in the Fourier domain, the phase shift of which can be monitored independently through Fast Fourier Transform of the output spectrum. The photonic probes analytical potential was demonstrated through detection of antibodies against SARS-CoV-2 in human serum samples. For this, one MZI was functionalized with the Receptor Binding Domain (RBD) of SARS-CoV-2 Spike 1 protein, and the other with bovine serum albumin to serve as reference. The biofunctionalized probes were immersed for 10 min in human serum sample and then for 5 min in goat anti-human IgG Fc specific antibody solution. Using a humanized rat antibody against SARS-CoV-2 RBD, a detection limit of 20 ng/mL was determined. Analysis of human serum samples indicated that the proposed sensor discriminated completely non- infected/non-vaccinated from vaccinated individuals, and the antibodies levels determined correlated well with those determined in the same samples by ELISA. These results demonstrated the potential of the proposed sensor to serve as an efficient tool for expeditious point-of-care testing

  • 287.
    Anghel, Ionut Gheorghe
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Reactor Technology.
    Anglart, Henryk
    KTH, School of Engineering Sciences (SCI), Physics, Reactor Technology.
    Post-dryout heat transfer to high-pressure water flowing upward in vertical channels with various flow obstacles2012In: International Journal of Heat and Mass Transfer, ISSN 0017-9310, E-ISSN 1879-2189, Vol. 55, no 25-26, p. 8020-8031Article in journal (Refereed)
    Abstract [en]

    Post-dryout heat transfer to high pressure water was investigated experimentally in vertical tubes and annuli containing various flow obstacles. The operational conditions during the experiments were as follows: mass flux from 500 to 1750 kg/m(2) s. pressure from 5 to 9 MPa, inlet subcooling from 10 to 40K and heat flux up to 1.5 MW/m(2). Five different test sections were used in experiments: three annular test sections with inner diameter 12.7 mm and outer diameter 24.3 mm, containing cylindrical and grid flow obstacles in the upper part, and two tubular test sections with inner diameter 24.3 mm with and without pin flow obstacles. The heated length in all test sections was 3650 mm. The wall temperature was measured with 88 thermocouples located along the inner rod and the outer tube surfaces. Due to the presence of flow obstacles, only developing post-dryout heat transfer was observed. Selected post-dryout heat transfer correlations were compared to the experimental data. It has been concluded that all tested correlations predict significantly higher wall temperatures than those obtained in the present experiment. A simple correction function to the Saha model has been suggested which significantly improves the agreement between the correlation and the present data.

  • 288.
    Anglart, Henryk
    KTH, School of Engineering Sciences (SCI), Physics, Reactor Technology.
    Numerical analysis of the onset of heat transfer deterioration to supercritical water2010In: International Congress on Advances in Nuclear Power Plants 2010, ICAPP 2010: Volume 3, 2010, p. 1689-1695Conference paper (Refereed)
    Abstract [en]

    In this paper the mechanism of the onset of heat transfer deterioration to supercritical water is elucidated with detailed numerical predictions of flow and heat transfer in the boundary layer. It is shown that for low mass flow rates the buoyancy effects are dominant and the deterioration of heat transfer is caused by the turbulence damping in the vicinity of the heated wall. For high mass flow rates the mechanism of deterioration changes and the triggering factor is the decrease of the thermal conductivity of fluid in the viscous sub-layer. A numerical prediction of this phenomenon requires application of a low Reynolds number turbulence model with y+ less than 1.

  • 289. Angyal, G.
    et al.
    Csepura, G.
    Balkay, L.
    Galuska, L.
    Molnár, J.
    Valastyán, I.
    PET examination in intracranial tumor diagnosis of a cat2008In: AIP Conference Proceedings, 2008, p. 199-203Conference paper (Refereed)
    Abstract [en]

    This paper shows the significance of the Positron Emission Tomography (PET) in the veterinary medication through a case study of a cat brain tumor. A castrated male cat with bilateral mydriasis and blindness arrived at the veterinary clinic. After physical, laboratory and neurological investigations other sickness was ruled out and the inkling of the intracranial lesion had come to light. Brain tumor seemed the most likely to cause the illness because other symptoms appeared (for example: anorexia, depression) and they progrediated fast. PET examination, using 18F-FDG isotope, was performed to confirm the possible causes of the cat's symptoms

  • 290.
    Annala, E.
    et al.
    Department of Physics, Helsinki Institute of Physics, University of Helsinki, P.O. Box 64, FI-00014, Finland.
    Gorda, T.
    Department of Physics, University of Virginia, Charlottesville, 22904-4714, VA, United States.
    Kurkela, A.
    Faculty of Science and Technology, University of Stavanger, Stavanger, 4036, Norway.
    Nättilä, Joonas
    Nordita SU .
    Vuorinen, A.
    Department of Physics, Helsinki Institute of Physics, University of Helsinki, P.O. Box 64, FI-00014, Finland.
    Constraining the properties of neutron-star matter with observations2019In: Memorie della Societa Astronomica Italiana - Journal of the Italian Astronomical Society, Societa Astronomica Italiana , 2019, no 1-2, p. 81-86Conference paper (Refereed)
    Abstract [en]

    In this conference-proceedings contribution, we review recent advances in placing model-independent constraints on the properties of cold and dense QCD matter inside neutron stars. In addition to introducing new bounds for the Equation of State, we explain how these results may be used to make robust statements about the physical phase of strongly interacting matter in the centers of neutron stars of different masses. Our findings indicate that the existence of quark-matter cores inside massive neutron stars appears to be a very common feature of the allowed Equations of State, and should not be considered an exotic or unlikely scenario.

  • 291. Anoushirvani, B.
    et al.
    Enström, Daniel
    Fredriksson, Sverker
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Hansson, Johan
    Ökvist, P.
    Nicolaidis, A.
    Ekelin, Svante
    Kungliga tekniska högskolan, KTH.
    Gamma-ray bursts from primordial quark objects in space1997In: Proceedings of the Joint Meeting of the Networks 'The Fundamental Structure of Matter' and 'Tests of the Electroweak Symmetry Breaking', Ouranoupolis, Greece, May 1997, 1997Conference paper (Refereed)
    Abstract [en]

    We investigate the possibility that gamma-ray bursts originate in a concentric spherical shell with a given average redshift and find that this is indeed compatible with the data from the third BATSE (3B) catalog. It is also shown that there is enough freedom in the choice of unknown burst properties to allow even for extremely large distances to the majority of bursts. Therefore, we speculate about an early, and very energetic, origin of bursts, and suggest that they come from phase transitions in massive objects of pure quark matter, left over from the Big Bang.

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  • 292.
    Ansari, Nazanin
    et al.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Khartsev, Sergiy
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Grishin, Alexander
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Multicolor filter all-garnet magneto-optical photonic crystals2012In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 37, no 17, p. 3552-3554Article in journal (Refereed)
    Abstract [en]

    We demonstrate a multicolor optical filter and isolator based on a double-cavity magneto-optical (MO) photonic crystal. Being grown as a heteroepitaxial all-garnet multilayer, it compromises a strong MO response and high optical transmittance. Low-loss, high Faraday rotation passbands as well as strong light rejection within the stop band were achieved by optimization of distance between cavities and repetition number of distributed Bragg reflectors.

  • 293.
    Anselmino, M.
    et al.
    Dipertemento di Fisica Teoria, Universita di Torino and INFS.
    Boglione, M.
    Department of Physics and Astronomy, Vrije Universitet Amsterdam.
    Hansson, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Murgia, F.
    Institute Nazionale Fisica Nucleare, Seizone di Cagliari.
    Predictions for single spin asymmetries in ℓ parrow -> π X and γ * parrow -> π X2000In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 13, no 3, p. 519-526Article in journal (Refereed)
    Abstract [en]

    Predictions for the single transverse spin asymmetry AN in semi-inclusive DIS processes are given; non-negligible values of AN may arise from spin effects in the fragmentation of a polarized quark into a final hadron with a transverse momentum ěc k⊥ with respect to the jet axis, the so-called Collins effect. The elementary single spin asymmetry of the fragmenting quark has been fixed in a previous paper, by fitting data on parrow p -> π X, and by assuming that the QCD factorization theorem holds also when transverse momenta are taken into account. The predictions given here are based on the assumption that the Collins effect is the only cause of the observed single spin asymmetries in parrow p -> π X. Eventual spin and ěc k⊥ dependences in the quark distribution functions, the so-called Sivers effect, are also discussed.

  • 294. Anselmino, M.
    et al.
    Boglione, Mariaelena
    Hansson, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Burgia, F.
    Inclusive production of hadrons in lepton (polarized) p (polarized) ---> h (polarized) X and spin measurements1996In: Proceedings of International Workshop on Deep Inelastic Scattering and Related Phenomena, DIS 96, 1996, p. 583-589Conference paper (Refereed)
    Abstract [en]

    We discuss the production of polarized hadrons in polarized lepton nucleon interactions and show that the helicity density matrix of the hadron, when measurable, can give information on the spin structure of the nucleon and the spin dependence of the quark fragmentation process. Single spin asymmetries in the $\ell N^\uparrow \to hX$ process are also briefly discussed.

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  • 295. Anselmino, M.
    et al.
    Boglione, Mariaelena
    Hansson, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Murgia, F.
    Spin measurements in l p ---> h X deep inelastic scattering1997In: SPIN 96: proceedings; September 10-14, 1996, Amsterdam, the Netherlands, Singapore: World Scientific Publishing Co Pte Ltd , 1997, p. 346-348Conference paper (Refereed)
    Abstract [en]

    The production of hadrons in polarized lepton-nucleon deep inelastic scattering is discussed. The helicity density matrix of the hadron is computed within the QCD hard scattering formalism and its elements are shown to yield information on the spin structure of the nucleon and the spin dependence of the quark fragmentation process. The case of $\rho$ vector mesons is considered in more detail and estimates are given.

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    FULLTEXT01
  • 296.
    Anselmino, Mauro
    Luleå University of Technology.
    Diquarks1992Report (Other academic)
  • 297.
    Anselmino, Mauro
    et al.
    Dipartimento di Fisica Teorica, Università di Torino and Istituto Nazionale di Fisica Nucleare, Sezione di Torino.
    Boglione, Maria
    Dipartimento di Fisica Teorica, Università di Torino and Istituto Nazionale di Fisica Nucleare, Sezione di Torino.
    Hansson, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Murgia, Francesco
    Istituto Nazionale di Fisica Nucleare, Sezione di Cagliari.
    Polarized inclusive leptoproduction, lN→hX, and the hadron helicity density matrix ρ(h): Possible measurements and predictions1996In: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 54, no 1, p. 828-837Article in journal (Refereed)
    Abstract [en]

    We discuss the production of hadrons in polarized lepton-nucleon interactions and in the current jet fragmentation region; using the QCD hard scattering formalism we compute the helicity density matrix of the hadron and show how its elements, when measurable, can give information on the spin structure of the nucleon and the spin dependence of the quark fragmentation process. The cases of ρ vector mesons and Λ baryons are considered in more detail and, within simplifying assumptions, some estimates are given

  • 298.
    Anselmino, Mauro
    et al.
    Dipartimento di Fisica Teorica, Università di Torino and Istituto Nazionale di Fisica Nucleare, Sezione di Torino.
    Predazzi, Enrico
    Dipartimento di Fisica Teorica, Università di Torino and Istituto Nazionale di Fisica Nucleare, Sezione di Torino.
    Ekelin, Svante
    Kungliga tekniska högskolan, KTH.
    Fredriksson, Sverker
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Lichtenberg, D.B.
    Department of Physics, Indiana University.
    Diquarks1993In: Reviews of Modern Physics, ISSN 0034-6861, E-ISSN 1539-0756, Vol. 65, no 4, p. 1199-1233Article in journal (Refereed)
    Abstract [en]

    It is becoming increasingly clear that the concept of a diquark (a two-quark system) is important for understanding hadron structure and high-energy particle reactions. According to our present knowledge of quantum chromodynamics (QCD), diquark correlations arise in part from spin-dependent interactions between two quarks, from quark radial or orbital excitations, and from quark mass differences. Diquark substructures affect the static properties of baryons and the mechanisms of baryon decay. Diquarks also play a role in hadron production in hadron-initiated reactions, deep-inelastic lepton scattering by hadrons, and in e+e- reactions. Diquarks are important in the formation and properties of baryonium and mesonlike semistable states. Many spin effects observed in high-energy exclusive reactions pose severe problems for the pure quark picture of baryons and might be explained by the introduction of diquarks as hadronic constituents. There is considerable controversy, not about the existence of diquarks in hadrons, but about their properties and their effects. In this work a broad selection of the main ideas about diquarks is reviewed.

  • 299.
    Anthony, Tim
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Evaluating machine learning models for predicting glioma from single nucleotide polymorphism data2020Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Early detection of cancer is necessary to minimize mental and physical distress. Therefore, this report investigated the possibilities of using machine learning methods to detect glioma in an early stage. This by looking at genetic data from real patients. This data consists of more than 14 million genetic features called SNP:s, and is therefore considered highly dimensional. However, the question is if these genetic data can be used for prediction of glioma? 

     The approach used was to first reduce the dimension by methods such as weighted cosine similarities, PCA, undercomplete autoencoder, t-SNE and sum pooling. To make prediction, k-means, naive bayes, kNN and neural networks were used.

     The results of this study show that the methods mentioned above can be difficult to use in determining the risk of cancer. However, this may depend on the hyperparameters used in the models as these play a major role in performance. Some important hyperparameters were the number of nodes and layers in the undercomplete autoencoder and the neural network. Using too many nodes or layers may cause these models to overfit. Contrary, using too few nodes or layers may instead cause them to underfit. The perplexity in the t-SNE and the number of blocks in the sum pooling were also key parameters, these two hyperparameters were hard to tune well since the grid search was very costly time-wise.

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    fulltext
  • 300.
    Antipov, Sergey V.
    et al.
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    Gustafsson, Magnus
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    Nyman, Gunnar
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    Isotope effect in the formation of carbon monoxide by radiative association2013In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 430, no 2, p. 946-950Article in journal (Refereed)
    Abstract [en]

    Rate coefficients for the formation of 12CO and 13CO isotopologues of carbon monoxide by radiative association for T = 10–20 000 K are calculated using a quantum mechanical approach. It is shown that the presence of the potential barrier on the A1Π electronic state of CO leads to different formation channels for the isotopologues at low temperatures. The corresponding rate coefficients are fitted to an analytic formula.

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