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  • 1.
    Forshult, Stig E.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap.
    Magnetic Resonance Imaging – MRI – An Overview2007Rapport (Annet vitenskapelig)
    Abstract [en]

    Magnetic Resonance Imaging or MRI is a modern diagnostic tool for acquiring information from the interior of a human body. MRI can create three-dimensional images of a human organ without hurting the organ in any way and without using any ionizing radiation.

    The body must be placed in a strong magnetic field; more than ten thousand times the magnetic field of earth. A radio signal is sent into the body, where it is absorbed by hydrogen atoms. The hydrogens in the body respond by sending back a signal to a detector. The strength of this signal mirrors the amount of hydrogen in various parts of the body.

    When creating an image of an organ, the signal must be acquired from every part of the organ point by point by a scanning procedure. To accomplish this, the magnetic field is rapidly varied with gradients in three dimensions. The monitored signal is the sum of signals from every unique volume element within the body. The instrument receives a large number of data from which the signal magnitude of every volume element can be calculated.

    Most parts of the body have a roughly equal concentration of hydrogen. However, signals from hydrogen atoms decay with unequal speeds depending on their various environments. Therefore the magnitude of the induced radio signal is monitored some time after the end of the initializing puls. Now various tissues show different signal strengths, from which it is possible to build an image with desired contrast. This is often excellent, even for soft tissues. It is of special interest that the signal from hydrogen in lesions and tumors often decay slower than surrounding tissues and therefore can be detected in the image.

    The contrast of the image is created by the experimental procedure and is not inherent in the imaged body. Thus different experimental routines will result in unequal images – not pictures – of the same object. Therefore it is crucial that the experimenter learns how to use different RF-pulse sequences and how to interpret the result.

  • 2. Haider, Miran
    Geometric Phases In Quantum Systems Of Pure And Mixed State2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Note that equations and expressions has been omitted here and is instead presented in the work. 

    This thesis focuses on the geometric phase in pure and mixed quantum states. For the case of a pure quantum state, Berry's adiabatic approach (4.1.10) and Aharonov & Anandan's non-adiabatic generalization of Berry's approach (4.2.8) are included in this work. Mixed quantum state involves Uhlmanns approach (5.1.42), which is used extensively in Section 7 and Sjöqvist's et al. approach (5.2.22), used extensively in Section 6. Sjöqvist's approach states that the Uhlmann phase is an observable and provides the experimental groundworkusing an interferometer.􀀀This was later proven, by Du et al.[45] to reproduce experimental data (Figure 19) on page 56.

    The Uhlmann phase can be used to observe the behaviour of topological kinks. This was tested on 3 models, the Creutz-ladder, the Majorana chain andthe SSU-model. It is found that the Uhlmann phase is split into two regimes with the dividing parameter being the temperature. This temperature is called the critical temperature, Tc. If the temperatureis is below the critical temperature, the Uhlmann phase yields Π and if thetemperature is above the critical temperature, the Uhlmann phase yields zero.

  • 3.
    Hansson, Rickard
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Lindqvist, Camilla
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Ericsson, Leif
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Opitz, Andreas
    Humboldt univ. .
    Wang, Ergang
    Chalmers.
    Moons, Ellen
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Photodegradation in air of the active layer components in a thiophene-quinoxaline copolymer:fullerene solar cell2016Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, nr 16, s. 11132-11138Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have studied the photo-degradation in air of a blend of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and poly[2,3-bis-(3-octyloxyphenyl)quinoxaline-5,8-diyl-alt-thiophene-2,5-diyl] (TQ1), and how the photo-degradation affects the solar cell performance. Using near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, changes to the electronic structure of TQ1 and PCBM caused by illumination in ambient air are investigated and compared between the pristine materials and the blend. The NEXAFS spectra show that the unoccupied molecular orbitals of TQ1 are not significantly changed by the exposure of pristine TQ1 to light in air, whereas those of PCBM are severely affected as a result of photo-induced degradation of PCBM. Furthermore, the photo-degradation of PCBM is accelerated by blending it with TQ1. While the NEXAFS spectrum of TQ1 remains unchanged upon illumination in air, its valence band spectrum shows that the occupied molecular orbitals are weakly affected. Yet, UV-Vis absorption spectra demonstrate photo-bleaching of TQ1, which is attenuated in the presence of PCBM in blend films. Illumination of the active layer of TQ1: PCBM solar cells prior to cathode deposition causes severe losses in electrical performance.

  • 4.
    Juteräng, David
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap.
    STM Study of PTCDA on Pb/Si(111) 1×12012Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    The interaction and orbital energy levels of 3,4,9,10-perylene-tetracarboxylic dianhydride (PTCDA) molecules on a Pb/Si(111) 1x1 substrate have been investigated. A Si(111) sample was annealed to form the 7x7 configuration. 1.5 monolayer of Pb was evaporated onto the surface, which was then annealed. 0.5 monolayer of PTCDA was applied to the substrate through molecular beam epitaxy (MBE). The surface configuration of the substrate was monitored step by step by low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM). Scanning tunneling spectroscopy (STS) was used to pinpoint the energy levels of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the molecules.

    It was found that the PTCDA molecules formed a herringbone pattern on the substrate. The PTCDA electronic energy levels corresponding to the HOMO and the LUMO were obtained. From these values the energy gap between these orbitals, the molecular bandgap of PTCDA on Pb/Si(111) 1x1, was determined.

  • 5.
    Selin, Mårten
    et al.
    KTH.
    Fogelqvist, Emelie
    KTH.
    Holmberg, Anders
    KTH.
    Guttmann, Peter
    Vogt, Ulrich
    KTH.
    Hertz, Hans M.
    KTH.
    3D simulation of the image formation in soft x-ray microscopes2014Inngår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 22, nr 25, s. 30756-30768Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In water-window soft x-ray microscopy the studied object is typically larger than the depth of focus and the sample illumination is often partially coherent. This blurs out-of-focus features and may introduce considerable fringing. Understanding the influence of these phenomena on the image formation is therefore important when interpreting experimental data. Here we present a wave-propagation model operating in 3D for simulating the image formation of thick objects in partially coherent soft x-ray microscopes. The model is compared with present simulation methods as well as with experiments. The results show that our model predicts the image formation of transmission soft x-ray microscopes more accurately than previous models.

  • 6.
    Thorén, Alexander
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013).
    Quantum teleportation and its experimental realization: Teleporting moving quantum states onto a stationary medium2013Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    A quantum mechanical state may be transferred between locations using quantum teleportation.Specically information encoded in the polarized state of a light pulse maybe teleported onto the collective spin state of an ensemble of atoms. This thesis providesa theoretical framework for achieving such a teleportation protocol experimentally.

  • 7.
    Vilardell, Anna M.
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Fredriksson, Gunnel
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Yadroitsev, I.
    Cent Univ Technol Free State, Dept Mech & Mechatron Engn, South Africa.
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Fracture mechanisms in the as-built and stress-relieved laser powder bed fusion Ti6Al4V ELI alloy2019Inngår i: Optics and Laser Technology, ISSN 0030-3992, E-ISSN 1879-2545, Vol. 109, s. 608-615Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The influence of a stress-relief treatment on impact and fatigue properties of Ti6Al4V ELI samples manufactured by laser powder bed fusion was analyzed. The heat treatment resulted in removal of residual stresses, coarsening of needles and formation of precipitations between needles. In both, impact and fatigue tests, crack development was correlated to microstructural features. Fracture analysis was carried out by means of optical and electron microscopy to reveal the influence of microstructure on crack development. Ductile fracture was the dominating fracture mode at impact testing. Pore formation and coalescence were the main crack formation mechanisms. The microstructural changes led to a decrease in impact toughness after heat treatment. Presumably, this was a result of the precipitations between needles. Fatigue results showed multiple crack nucleation at the surface in both, as-built and stress-relieved material. The crack propagation rate was slightly higher and the crack was less deflected in the stress-relieved material due to the stress relief and coarsening of the microstructure.

  • 8.
    Vogt, Ulrich
    et al.
    KTH.
    Reinspach, Julia
    KTH.
    Uhlén, Fredrik
    KTH.
    Nilsson, Daniel
    KTH.
    Hertz, Hans M.
    KTH.
    Holmberg, Anders
    KTH.
    Diffractive optics for laboratory sources to free electron lasers2013Inngår i: 11th International Conference On X-Ray Microscopy (XRM2012), Institute of Physics (IOP), 2013, s. 012001-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this contribution we present our recent results in the field of diffractive optics for both soft and hard x-ray radiation, and for laboratory sources to x-ray free electron lasers (XFEL). We developed a laboratory soft x-ray microscope that uses in-house produced zone plate optics as high-resolution objectives. We continuously try to improve these optics, both in terms of efficiency and resolution. Our latest development is the manufacturing of tungsten soft x-ray zone plates with outermost zone widths of 12 nm and 90 nm high structures. For hard x-rays, we investigated the possibility to use metal zone plates on a diamond substrate for nano-focusing of the European X-ray Free Electron Laser. The simulations show that the heat conduction is efficient enough to keep a zone plate well below melting temperature. However, metal zone plates will experience large and rapid temperature fluctuations of several hundred Kelvin that might prove fatal. To test this, we manufactured tungsten on diamond prototype zone plates and exposed them to radiation from the LCLS XFEL. Results show that metal zone plates can survive the XFEL beam.

  • 9.
    Zhang, Hanmin
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    Ericsson, Leif
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    Johansson, Lars
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    PTCDA on Sn/Si(111)-2√3×2√32012Konferansepaper (Fagfellevurdert)
  • 10.
    Östersjö, Victor
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Supersymmetry for the Hydrogen Atom2015Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    In this thesis it will be shown that the hydrogen atom has a SU(2) × SU(2) symmetry generated by the quantum mechanical angular momentum and Runge-Lenz vector operators. Additionally, the hydrogenic atom will be studied with supersymmetric methods to identify a supersymmetry that relates different such systems. This thesis is intended to present the material in a manner accessible to people without background in Lie groups and supersymmetry, as well as fill in some calculations between steps that are not spelt out in the litterature.

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