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  • 8551.
    Bergqvist, Göran
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mathematics, Applied Mathematics.
    Eriksson, Ingemar
    Linköping University, The Institute of Technology. Linköping University, Department of Mathematics, Applied Mathematics.
    Senovilla, José M M
    New conservation laws in Einstein-Maxwell spacetimes2004In: 17th International Conference on General Relativity and Gravitation,2004, 2004Conference paper (Other academic)
  • 8552.
    Bergqvist, Göran
    et al.
    Linköping University, Department of Mathematics, Applied Mathematics. Linköping University, The Institute of Technology.
    Forrester, Peter J.
    University of Melbourne, Victoria, Australia.
    Rank probabilities for real random NxNx2 tensors2011In: Electronic Communications in Probability, ISSN 1083-589X, E-ISSN 1083-589X, Vol. 16, 630-637 p.Article in journal (Refereed)
    Abstract [en]

    We prove that the probability P_N for a real random Gaussian NxNx2 tensor to be of real rank N is P_N=(Gamma((N+1)/2))^N/G(N+1), where Gamma(x) and G(x) denote the gamma and the Barnes G-functions respectively. This is a rational number for N odd and a rational number multiplied by pi^{N/2} for N even. The probability to be of rank N+1 is 1-P_N. The proof makes use of recent results on the probability of having k real generalized eigenvalues for real random Gaussian N x N matrices. We also prove that log P_N= (N^2/4)log (e/4)+(log N-1)/12-zeta'(-1)+O(1/N) for large N, where zeta is the Riemann zeta function.

  • 8553.
    Bergqvist, Göran
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mathematics, Applied Mathematics.
    Hoglund, A.
    Algebraic Rainich theory and antisymmetrization in higher dimensions2002In: Classical and quantum gravity, ISSN 0264-9381, E-ISSN 1361-6382, Vol. 19, no 12, 3341-3355 p.Article in journal (Refereed)
    Abstract [en]

    The classical Rainich(-Misner-Wheeler) theory gives necessary and sufficient conditions on an energy-momentum tensor T to be that of a Maxwell field (a 2-form) in four dimensions. Via Einstein's equations, these conditions can be expressed in terms of the Ricci tensor, thus providing conditions for a spacetime geometry to be an Einstein-Maxwell spacetime. One of the conditions is that T2 is proportional to the metric, and it has previously been shown in arbitrary dimension that any tensor satisfying this condition is a superenergy tensor of a simple p-form. Here we examine algebraic Rainich conditions for general p-forms in higher dimensions and their relations to identities by antisymmetrization. Using antisymmetrization techniques we find new identities for superenergy tensors of these general (non-simple) forms, and we also prove in some cases the converse: that the identities are sufficient to determine the form. As an example we obtain the complete generalization of the classical Rainich theory to five dimensions.

  • 8554.
    Bergqvist, Göran
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mathematics, Applied Mathematics.
    Lankinen, Paul
    Algebraic and differential Rainich conditions for symmetric trace-free tensors of higher rank2005In: Proceedings of the Royal Society. Mathematical, Physical and Engineering Sciences, ISSN 1364-5021, E-ISSN 1471-2946, Vol. 461, no 2059, 2181-2195 p.Article in journal (Refereed)
    Abstract [en]

    We present a study of Rainich-like conditions for symmetric and trace-free tensors T. For arbitrary even rank we find a necessary and sufficient differential condition for a tensor to satisfy the source-free field equation. For rank 4, in a generic case, we combine these conditions with previously obtained algebraic conditions to gain a complete set of algebraic and differential conditions on T for it to be a superenergy tensor of a Weyl candidate tensor, satisfying the Bianchi vacuum equations. By a result of Bell and Szekeres, this implies that in vacuum, generically, T must be the Bel-Robinson tensor of the spacetime. For the rank 3 case, we derive a complete set of necessary algebraic and differential conditions for T to be the superenergy tensor of a massless spin-3/2 field, satisfying the source-free field equation.

  • 8555.
    Bergqvist, Göran
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mathematics, Applied Mathematics.
    Lankinen, Paul
    Algebraic and differential Rainich conditions for the Bel-Robinson tensor and other higher rank tensors2004In: 17th International Conference on General Relativity and Gravitation,2004, 2004Conference paper (Other academic)
  • 8556.
    Bergqvist, Göran
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mathematics, Applied Mathematics.
    Lankinen, Paul
    Unique characterization of the Bel-Robinson tensor2004In: Classical and quantum gravity, ISSN 0264-9381, E-ISSN 1361-6382, Vol. 21, no 14, 3499-3503 p.Article in journal (Refereed)
    Abstract [en]

    We prove that a completely symmetric and trace-free rank-4 tensor is, up to sign, a Bel-Robinson-type tensor, i.e., the superenergy tensor of a tensor with the same algebraic symmetries as the Weyl tensor, if and only if it satisfies a certain quadratic identity. This may be seen as the first Rainich theory result for rank-4 tensors.

  • 8557.
    Bergqvist, Göran
    et al.
    Linköping University, Department of Mathematics, Applied Mathematics. Linköping University, The Institute of Technology.
    Larsson, Erik G
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Overview of recent advances in numerical tensor algebra2010In: Proceedings of Asilomar Conference on Signals, Systems and Computers, 2010, 3-7 p.Conference paper (Other academic)
    Abstract [en]

    We present a survey of some recent developments for decompositions of multi-way arrays or tensors, with special emphasis on results relevant for applications and modeling in signal processing. A central problem is how to find lowrank approximations of tensors, and we describe some new results, including numerical methods, algorithms and theory, for the higher order singular value decomposition (HOSVD) and the parallel factors expansion or canonical decomposition (CP expansion).

  • 8558.
    Bergqvist, Göran
    et al.
    Linköping University, Department of Mathematics, Applied Mathematics. Linköping University, The Institute of Technology.
    Larsson, Erik G.
    Linköping University, The Institute of Technology. Linköping University, Department of Electrical Engineering, Communication Systems.
    The Higher-Order Singular Value Decomposition Theory and an Application2010In: IEEE signal processing magazine (Print), ISSN 1053-5888, E-ISSN 1558-0792, Vol. 27, no 3, 151-154 p.Article in journal (Other academic)
    Abstract [en]

    Tensor modeling and algorithms for computing various tensor decompositions (the Tucker/HOSVD and CP decompositions, as discussed here, most notably) constitute a very active research area in mathematics. Most of this research has been driven by applications. There is also much software available, including MATLAB toolboxes [4]. The objective of this lecture has been to provide an accessible introduction to state of the art in the field, written for a signal processing audience. We believe that there is good potential to find further applications of tensor modeling techniques in the signal processing field.

  • 8559.
    Bergqvist, Göran
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mathematics, Applied Mathematics.
    Senovilla, José M. M.
    Structure of conformal Lorentz transformations2003In: Current Trends in Relativistic Astrophysics: theoretical, numerical, observational / [ed] L. Férnadez-Jambrina, L.M. González-Romero, Springer , 2003, 245-251 p.Chapter in book (Other academic)
    Abstract [en]

    The present volume contains the expanded lectures of a meeting on relativistic astrophysics, the goal of which was to provide a modern introduction to specific aspects of the field for young researchers, as well as for nonspecialists from related areas. Particular emphasis is placed on the theory of black holes and evolution, relativistic stars and jet hydrodynamics, as well as the production and detection of gravitational waves. The book is complemented by further contributions and animation supplied on the accompanying CD-ROM.

  • 8560.
    Bergqvist, Göran
    et al.
    Private practice, Norrköping, Sweden.
    Simonsson, Kjell
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Rydberg, Kristoffer
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Johansson, Fredrik
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Dérand, Tore
    Department of Dental Technology and Dental Materials Science, Faculty of Odontology, Malmö University, Malmö, Sweden.
    A finite element analysis of stress distribution in bone tissue surrounding uncoupled or splinted dental implants2008In: Clinical Implant Dentistry and Related Research, ISSN 1523-0899, E-ISSN 1708-8208, Vol. 10, no 1, 40-46 p.Article in journal (Refereed)
    Abstract [en]

    Background: Several studies on one-stage surgery in the treatment of the edentulous maxilla with implant-supported fixed prostheses have reported problems with removable provisional prostheses, which can load the implants in an uncontrollable manner during healing, and jeopardize healing. Immediate splinting of the implants with a fixed provisional prosthesis has been proposed to protect the bone-implant interface.

    Purpose: This study used the finite element method (FEM) to simulate stresses induced in bone tissue surrounding uncoupled and splinted implants in the maxilla because of bite force loading, and to determine whether the differences in these stress levels are related to differences in observed bone losses associated with the two healing methods.

    Materials and Methods: Stress levels in the maxilla were studied using the FEM program TRINITAS (Institute of Technology, Linköping University, Linköping, Sweden) in which all phases – preprocessing/modeling, equation solving, and postprocessing/evaluation – were simulated.

    Results: Stress levels in bone tissue surrounding splinted implants were markedly lower than stress levels surrounding uncoupled implants by a factor of nearly 9.

    Conclusion: From a mechanical viewpoint, FEM simulation supports the hypothesis that splinting reduces damage evolution in bone tissue, which agrees with clinical observations.

  • 8561.
    Bergqvist, Ingrid
    Linköping University, Department of Culture and Communication. Linköping University, Faculty of Arts and Sciences.
    Den flexibla västen: en dokumentation av en produktutveckling inom textilslöjd2010Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Detta arbete består av två delar. En del som resulterat i sömnaden av tre västar samt en del som består av en skriven rapport.

    Syftet med arbetet har varit att genomföra och dokumentera hur jag utifrån kulturarv och slöjdtradition har inspirerats till produktutveckling av plagget väst och i en vidare förlängning hoppas kunna förmedla detta till slöjdstuderande.

     Jag arbetade kvalitativt i nära kontakt med skisser, material, redskap och plagg under observation av mitt eget arbete. Under tiden fördes dagboksanteckningar utifrån rubrikerna inspiration, genomförande, erfarenheter av material och teknik samt reflektion. Litteratur har studerats om personer som arbetat på ett likartat sätt den dräkthistoriska utvecklingen av plagget väst och till viss del livstycke.

    I resultatet presenteras hur produktutvecklingen växt fram utifrån den första skissen till det färdiga slutresultatet. Resultatet visar att det går att beskriva hur den skapande processen gått till genom att noga dokumentera genom skisser och anteckningar. I mitt arbete kom jag fram till att det är betydlig enklare att fokusera på arbetet om man har sammanhängande tid och att motivationen försämrades när tiden var lösryckt.

    Resultat av de färdiga västarna visar att det går att förena nutida behov med tradition som inspiration.

    I diskussionen nämns hur viktigt det kan vara med att någon annan får insyn i den egna processen om det känns trögt samt vikten av att skissa mycket. Jag tycker även att man inom skolslöjden behöver fundera kring målet att arbeta utifrån  kulturarv och ställer frågan varför man sällan utgår från tradition gällande klädsömnad men däremot när det gäller produkter till hemmet. Som lärare bör du ha reflekterat kring begreppet.

  • 8562.
    Bergqvist, Ingrid
    Linköping University, Department of Behavioural Sciences and Learning. Linköping University, Faculty of Educational Sciences.
    Lärares bedömning av bildämnet vid en lärarutbildning i Sydafrika: En minor Field study2014Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Assessment of the Arts has been challenged regarding its quality, fairness, function and how it affects the subject and the individual .  The study examines assessment of Visual Arts in teaching education in South Africa, presented from a teacher’s view. The research questions have been based on a didactics theory .The Method is a two-month field work with participant observations, collection of documents and interviews at the teaching education where the daily work of three teachers, have been followed.

    The empirical material is analyzed from the three didactic questions what, how and why. The result shows that the teacher’s assessments are based on a normative approach in regards to high and low quality. The teachers performed collegial assessments of student work. A relative rating system were works were compared was used during the assessment. No explicit grading criteria were used. Students were repeatedly summative assessed on attendance, work pace, how they followed instructions and results of the projects. The projects were judged in parts where artistic technical skills dominated the grading process.

    Criteria were communicated to students during the lesson and presentation as brief comments, such as nice, good, bad composition and pieces student work was often used as an example. Feedback was recurrent describing the product but was rarely formative in interaction with the student. During lessons teachers improved some parts of students work by painting /drawing directly on their products, which might make questionable a fair assessment. The teacher regarded assessment as relatively easy task, referring to personal experience rather than to criteria/aims in course syllabus. Students' intentions of their work were not assessed.

    The study provides a basis for discussing how cultural context affects the way to assess and raises issues in relation to sustainable quality education of fair assessment. The ethnographic method increases understanding and helps reflections of higher education from a global perspective.

  • 8563.
    Bergqvist, Joakim
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Runn, Joel
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Relations between speed and flow for sparse 2+1 roads2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    För att besluta vilken vägtyp som ska byggas är det viktigt att Trafikverket har bra underlag. Ett viktigt sådant underlag är så kallade hastighetsflödessamband. Sambanden visar hur trafikflödet påverkar hastigheten på vägen och kan användas för att skapa en bild över vilka trafiksituationer som kan förväntas. För så kallade glesa 2+1-vägar, där endast 15-35 % av vägens totala längd är tillgänglig för omkörning, är problemet att det saknas empiriska observationer för hur flödet påverkar hastigheten vid höga flöden. För att förbättra trafiksäkerheten byggde dåvarande Vägverket ut 2+1-vägar på ett flertal platser i landet. På platser där trafiken är låg har glesa 2+1-vägar byggts istället för konventionella 2+1-vägar, där andel omkörbar längd är större. I och med att trafiken på glesa 2+1-vägar ofta är låg skapas inte trängsel i lika stor utsträckning. Om det i framtiden skulle bli ökningar av trafikvolymerna på dessa vägar innebär det att Trafikverket i dagsläget saknar information för att svara på vilken hastighet ett visst flöde leder till på de glesa 2+1-vägarna. Därför ligger det i intresse att undersöka hastighetsflödessambandets form fram till kapacitetstaket för dessa vägar. Syftet med detta arbete har varit att undersöka hur hastigheten på glesa 2+1-vägar påverkas av olika flödesnivåer på vägen. På Statens Väg- och Transportforskningsinstitut (VTI) finns ett simuleringsverktyg som är anpassat för simulera trafiksituationer på olika typer av landsvägsutformningar. Detta verktyg, RuTSim, har använts för att simulera fram data på hastigheten vid olika trafikflöden. Simuleringarna har genomförts för en typ av landvägsutformning, nämligen en rak mötesfri landsväg med hastighetsgräns 100 km/h. Detta har genomförts både för typiska glesa 2+1-vägar baserade på verkliga vägar, och fiktiva experimentvägar. För experimentvägarna har tre parametrar valts att förändras mellan scenarierna; andel tunga fordon (10 och 15 %), antal omkörningsfält (ett, två och tre) och andel omkörbar längd (20 och 30 %). Totalt har tolv olika scenarier undersökts. Simuleringsresultaten visar att det råder små skillnader mellan de olika alternativa vägutformningar och trafiksammansättningar som har undersökts. Det alternativ som har genererat minst medelfördröjning av undersökta är scenariot med tre omkörningsfält, 30 % andel omkörbar längd och 10 % tunga fordon. Dessutom har det visat sig att andel tunga fordon är den faktor som påverkar medelreshastigheten och medelfördröjningen mest. De hastighetsflödessamband som Trafikverket använder sig av ligger generellt sett högre än de samband som framtagits via trafiksimulering. Vidare arbete behövs därför för att bekräfta denna skillnad. Dessutom behöver effekten av fler alternativa utformningar och andra hastighetspåverkande faktorer undersökas.

  • 8564.
    Bergqvist, Jonas
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Microstructure and Temperature Stability of APFO-3:PCBM Organic Photovoltaic Blends2010Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this thesis, the microstructure of organic photovoltaic APFO-3:PC61BM bulk-heterojunction blends was examined. Earlier studies have focused on the microstructure after spin coating. This thesis aims to give a better insight into microstructural degradation as the films are annealed above the glass transition temperature, Tg, and the mixture approaches thermodynamic equilibrium. Electro- and photoluminescence studies indicate that the polymer and PC61BM are intermixed on a scale shorter than the exciton diffusion length of 10 nm, even when annealed above Tg. The temperature stability of APFO-3:PC61BM was also investigated with respect to the molecular weight of the polymer. The photovoltaic performance of these blends was found to be stable up to temperatures approaching the glass transition temperature, especially if a high molecular-weight APFO-3 grade was used.

     

    The crystallization of PC61BM was also investigated. Above Tg, PC61BM crystallization was found to commence, albeit slowly at temperatures close to Tg. At elevated temperatures instead, micrometer sized crystals were observed to form. It was also noted that illumination while annealing APFO-3:PC61BM thin films above Tg affected PC61BM crystallization, the origin of which is so far unclear although chemical degradation could be largely excluded.

  • 8565.
    Bergqvist, Jonas
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Optoelectrical Imaging Methods for Organic Photovoltaic Materials and Moduls2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    To achieve a high living standard for all people on Earth access to low cost energy is essential. The massive burning of fossil fuels must be drastically reduced if we are to avoid large changes of our climate. Solar cells are both technologically mature and have the potential to meet the huge demand for renewable energy in many countries. The prices for silicon solar cells have decreased rapidly during the course of this thesis and are now in grid parity in many countries.

    However, the potential for even lower energy costs has driven the research on polymer solar cells, a class of thin film solar cells. Polymer solar cells can be produced by roll to roll printing which potentially enables truly low cost solar cells. However, much research and development remain to reach that target.

    Polymer solar cells consist of a semiconducting composite material sandwiched between two electrodes, of which one is transparent, to let the light energy in to the semiconductor where it is converted to electric energy. The semiconductor comprise an intimate blend of polymer and fullerenes, where the nanostructure of this blend is crucial for the photo current extraction.

    To reach higher solar cell performance the dominating strategy is development and fine tuning of new polymers. To estimate their potential as solar cell materials their optical response have been determined by spectroscopic ellipsometry. Furthermore, optical simulations have been performed where the direction dependency of the optical response of the transparent electrode material PEDOT:PSS have been accounted for. The simulations show reduced electrode losses for light incident at large oblique angles.

    Moreover, we have shown that a gentle annealing of the active layer induces a local conformational changes of an amorphous polymer that is beneficial for solar cell performance. The active layer is deposited from solution where the drying kinetics determine the final nanostructure. We have shown that using in-situ photoluminescence phase separation can be detected during the drying process while a reflectance method have been developed to image lateral variations of solvent evaporation rate.

    Imaging methods are important tools to detect performance variations over the solar cell area. For this purpose an intermodulation based photo current imaging method have been developed to qualitatively differentiate the major photo current loss mechanisms. In addition, a 1D LED-array photo current imaging method have been developed and verified for high speed in-line characterization of printed organic solar modules.

    List of papers
    1. Comparison of selenophene and thienothiophene incorporation into pentacyclic lactam-based conjugated polymers for organic solar cells
    Open this publication in new window or tab >>Comparison of selenophene and thienothiophene incorporation into pentacyclic lactam-based conjugated polymers for organic solar cells
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    2015 (English)In: Polymer Chemistry, ISSN 1759-9954, E-ISSN 1759-9962, Vol. 6, no 42, 7402-7409 p.Article in journal (Refereed) Published
    Abstract [en]

    In this work, we compare the effect of incorporating selenophene versus thienothiophene spacers into pentacyclic lactam-based conjugated polymers for organic solar cells. The two cyclic lactam-based copolymers were obtained via a new synthetic method for the lactam moiety. Selenophene incorporation results in a broader and red-shifted optical absorption while retaining a deep highest occupied molecular orbital level, whereas thienothienophene incorporation results in a blue-shifted optical absorption. Additionally, grazing-incidence wide angle X-ray scattering data indicates edge- and face-on solid state order for the selenophene-based polymer as compared to the thienothiophene-based polymer, which orders predominantly edge-on with respect to the substrate. In polymer : PC71BM bulk heterojunction solar cells both materials show a similar open-circuit voltage of similar to 0.80-0.84 V, however the selenophene-based polymer displays a higher fill factor of similar to 0.70 vs. similar to 0.65. This is due to the partial face-on backbone orientation of the selenophene-based polymer, leading to a higher hole mobility, as confirmed by single-carrier diode measurements, and a concomitantly higher fill factor. Combined with improved spectral coverage of the selenophene-based polymer, as confirmed by quantum efficiency experiments, it offers a larger short-circuit current density of similar to 12 mA cm(-2). Despite the relatively low molecular weight of both materials, a very robust power conversion efficiency similar to 7% is achieved for the selenophene-based polymer, while the thienothiophene-based polymer demonstrates only a moderate maximum PCE of similar to 5.5%. Hence, the favorable effects of selenophene incorporation on the photovoltaic performance of pentacyclic lactam-based conjugated polymers are clearly demonstrated.

    Place, publisher, year, edition, pages
    ROYAL SOC CHEMISTRY, 2015
    National Category
    Biological Sciences
    Identifiers
    urn:nbn:se:liu:diva-122675 (URN)10.1039/c5py01245g (DOI)000363214600007 ()
    Note

    Funding Agencies|Chalmers Areas of Advance Materials Science, Energy and Nanoscience and Nanotechnology; Swedish Research Council; Knut and Alice Wallenberg foundation; Swedish Energy Agency; South Australian government; NSF; NIH/NIGMS via NSF [DMR-1332208]

    Available from: 2015-11-16 Created: 2015-11-13 Last updated: 2017-12-01
    2. Uniaxial anisotropy in PEDOT:PSS electrodes enhances the photo current at oblique incidence in organic solar cells
    Open this publication in new window or tab >>Uniaxial anisotropy in PEDOT:PSS electrodes enhances the photo current at oblique incidence in organic solar cells
    2015 (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    In this work an uniaxial anisotropic treatment of the transparent conductor PEDOT:PSS is included in the transfer matrix method (TMM), used to calculate the optical power dissipation in organic solar cells. PEDOT:PSS is known to be anisotropic and exhibit a weaker absorption and lower refractive index in the out of plane direction. For p-polarized light at large oblique incidence the inclusion of anisotropy show a gain of over 10% for the maximum photocurrent as compared to an isotropic treatment. Due to the interference in devices with reflecting bottom electrodes, the active layer absorption gain is not always occurring for the wavelengths with highest dichroism. This work show that using PEDOT:PSS as top electrode further strengthens the argument that thin film solar cells perform better than their silicon counterparts under oblique incidence. We also confirm previous studies showing that the optical interference maxima is shifted to slightly thicker films for oblique incidence for solar cells with reflective bottom electrodes.

    National Category
    Physical Sciences Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-123031 (URN)
    Available from: 2015-12-02 Created: 2015-12-02 Last updated: 2015-12-03Bibliographically approved
    3. In situ reflectance imaging of organic thin film formation from solution deposition
    Open this publication in new window or tab >>In situ reflectance imaging of organic thin film formation from solution deposition
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    2013 (English)In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 114, 89-98 p.Article in journal (Refereed) Published
    Abstract [en]

    In this work we present reflectance imaging as a suitable method for in situ monitoring of the drying process of film formation for organic photovoltaics (OPV) over large areas, as well as for lab-scale spin-coating. The drying wet film is illuminated with a narrow bandwidth LED with the specularly reflected light recorded by a video camera as the film dries and forms the active layer of the OPV cell. The interference fringes generated by the thinning wet film can be used to measure the rate of solvent evaporation and the drying time. Subsequent mapping elucidates variations in drying conditions over the substrate, which lead to variations in morphology formation. The technique is suitable for tracking thickness variations of the dry film, with a sensitivity of 10 nm, by comparing the intensity of the reflected light from the dry film to simulated interference conditions calculated for each thickness. The drying process is furthermore accurately simulated by an optical model considering the changes in refractive index as the amount of solvent decreases with respect to the solid content. This non-invasive in situ method represents an important monitoring tool for future large scale OPV manufacturing where high performing morphologies with uniform thickness have to be formed over very large areas.

    Place, publisher, year, edition, pages
    Elsevier, 2013
    Keyword
    Reflectance imaging, Process control, Blade coating, Spin coating, Evaporation, OPV
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-95498 (URN)10.1016/j.solmat.2013.02.030 (DOI)000319486700013 ()
    Note

    Funding Agencies|Knut and Alice Wallenberg foundation||Swedish Energy Agency||

    Available from: 2013-07-05 Created: 2013-07-05 Last updated: 2017-12-06
    4. Lateral Phase Separation Gradients in Spin-Coated Thin Films of High-Performance Polymer: Fullerene Photovoltaic Blends
    Open this publication in new window or tab >>Lateral Phase Separation Gradients in Spin-Coated Thin Films of High-Performance Polymer: Fullerene Photovoltaic Blends
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    2011 (English)In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 21, no 16, 3169-3175 p.Article in journal (Refereed) Published
    Abstract [en]

    In this study, it is demonstrated that a finer nanostructure produced under a rapid rate of solvent removal significantly improves charge separation in a high-performance polymer: fullerene bulk-heterojunction blend. During spin-coating, variations in solvent evaporation rate give rise to lateral phase separation gradients with the degree of coarseness decreasing away from the center of rotation. As a result, across spin-coated thin films the photocurrent at the first interference maximum varies as much as 25%, which is much larger than any optical effect. This is investigated by combining information on the surface morphology of the active layer imaged by atomic force microscopy, the 3D nanostructure imaged by electron tomography, film formation during the spin coating process imaged by optical interference and photocurrent generation distribution in devices imaged by a scanning light pulse technique. The observation that the nanostructure of organic photovoltaic blends can strongly vary across spin-coated thin films will aid the design of solvent mixtures suitable for high molecular-weight polymers and of coating techniques amenable to large area processing.

    Place, publisher, year, edition, pages
    Wiley-VCH Verlag Berlin, 2011
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-70526 (URN)10.1002/adfm.201100566 (DOI)000294166200019 ()
    Note

    Funding Agencies|Swedish Energy Agency||Spanish Ministerio de Ciencia e Innovacion||

    Available from: 2011-09-12 Created: 2011-09-12 Last updated: 2017-12-08Bibliographically approved
    5. Time-resolved morphology formation of solution cast polymer: fullerene blends revealed by in-situ photoluminescence spectroscopy
    Open this publication in new window or tab >>Time-resolved morphology formation of solution cast polymer: fullerene blends revealed by in-situ photoluminescence spectroscopy
    Show others...
    2015 (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    The nanoscale morphology of the photo-active layer in organic solar cells is critical for device efficiency. The photoactive layer is cast from solution and during drying both the polymer and the fullerene self-assemble to form a blend. Here, we introduce in-situ spectroscopic photoluminescence (PL) combined with laser reflectometry to monitor the drying process of an amorphous polymer:fullerene blend. When casting only the pristine components (polymer or PCBM only), the strength of PL emission is proportional to the solid content of the drying solution, and both kinetics reveal a rapid aggregation onset at the final stage of film drying. On the contrary, when casting polymer:fullerene blends, the strength of PL emission is proportional to the wet film thickness and reveals polymer/fullerene charge transfer (CT) already at the earliest stages of film drying, i.e. in dilute solutions. The proposed method allows to detect polymer/fullerene phase separation during film casting – from a reduction in the PL quenching rate as the film dries. Poor solvents lead to phase separation already at early stages of film drying (low solid content), resulting in a coarse final morphology as confirmed by atomic force microscopy (AFM). We therefore anticipate that the proposed method will be an important tool in the future development of processing inks, not only for solution-cast polymer:fullerene solar cells but also for organic heterojunctions in general.

    National Category
    Physical Sciences Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-123032 (URN)
    Available from: 2015-12-02 Created: 2015-12-02 Last updated: 2015-12-03
    6. Sub-glass transition annealing enhances polymer solar cell performance
    Open this publication in new window or tab >>Sub-glass transition annealing enhances polymer solar cell performance
    Show others...
    2014 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 2, no 17, 6146-6152 p.Article in journal (Refereed) Published
    Abstract [en]

    Thermal annealing of non-crystalline polymer: fullerene blends typically results in a drastic decrease in solar cell performance. In particular aggressive annealing above the glass transition temperature results in a detrimental coarsening of the blend nanostructure. We demonstrate that mild annealing below the glass transition temperature is a viable avenue to control the nanostructure of a non-crystalline thiophene-quinoxaline copolymer: fullerene blend. Direct imaging methods indicate that coarsening of the blend nanostructure can be avoided. However, a combination of absorption and luminescence spectroscopy reveals that local changes in the polymer conformation as well as limited fullerene aggregation are permitted to occur. As a result, we are able to optimise the solar cell performance evenly across different positions of the coated area, which is a necessary criterion for large-scale, high throughput production.

    Place, publisher, year, edition, pages
    Royal Society of Chemistry, 2014
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-106302 (URN)10.1039/c3ta14165a (DOI)000333580700024 ()
    Available from: 2014-05-06 Created: 2014-05-05 Last updated: 2015-12-03Bibliographically approved
    7. New method for lateral mapping of bimolecular recombination in thin film organic solar cells
    Open this publication in new window or tab >>New method for lateral mapping of bimolecular recombination in thin film organic solar cells
    Show others...
    2016 (English)In: Progress in Photovoltaics, ISSN 1062-7995, E-ISSN 1099-159X, Vol. 24, no 8, 1096-1108 p.Article in journal (Refereed) Published
    Abstract [en]

    The best organic solar cells are limited by bimolecular recombination. Tools to study these losses are available; however, they are only developed for small area (laboratory-scale) devices and are not yet available for large area (production-scale) devices. Here we introduce the Intermodulation Light Beam-Induced Current (IMLBIC) technique, which allows simultaneous spatial mapping of both the amount of extracted photocurrent and the bimolecular recombination over the active area of a solar cell. We utilize the second-order non-linear dependence on the illumination intensity as a signature for bimolecular recombination. Using two lasers modulated with different frequencies, we record the photocurrent response at each modulation frequency and the bimolecular recombination in the second-order intermodulation response at the sum and difference of the two frequencies. Drift-diffusion simulations predict a unique response for different recombination mechanisms. We successfully verify our approach by studying solar cells known to have mainly bimolecular recombination and thus propose this method as a viable tool for lateral detection and characterization of the dominant recombination mechanisms in organic solar cells. We expect that IMLBIC will be an important future tool for characterization and detection of recombination losses in large area organic solar cells.

    Place, publisher, year, edition, pages
    John Wiley & Sons, 2016
    Keyword
    Organic photovoltaics, imaging, photocurrent, bimolecular recombination, light beam induced current, LBIC, intermodulation
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-123033 (URN)10.1002/pip.2770 (DOI)000380164100007 ()
    Note

    Funding agencies|Swedish Research Council; Swedish Energy Agency; the Knut and Alice Wallenberg foundation through a Wallenberg Scholar grant to O.I

    At the time for thesis presentation publication was in status: Manuscript

    Available from: 2015-12-02 Created: 2015-12-02 Last updated: 2017-12-01Bibliographically approved
    8. LED array scanner for inline characterization of thin film photovoltaic modules
    Open this publication in new window or tab >>LED array scanner for inline characterization of thin film photovoltaic modules
    2016 (English)In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 157, no 17, 1057-1064 p.Article in journal (Refereed) Published
    Abstract [en]

    Thin film solar cells, and in particular printed organic solar cells, offer a potential route to a low cost power generation from sunlight. However, manufacturing these solar cells rapidly generates large areas that have to be characterized, preferably in-line for a direct feed back in the production process. Here we introduce the LEDimage, a LED array illumination induced photocurrent method suitable for high speed inline characterization and defect detection of organic solar cell modules. The LEDimage enables simultaneous illumination of all connected subcells without additional bias light. Each LED in the array is amplitude modulated at an individual frequency and the photocurrent response is Fourier transformed to generate a photocurrent map. Furthermore, the LEDimage can be used as a hand scanner for fast device characterization. We expect that LEDimage can be an effective research and industry tool for characterization of large area thin film solar cells.

    Place, publisher, year, edition, pages
    Elsevier, 2016
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-123034 (URN)10.1016/j.solmat.2016.08.010 (DOI)000384391700127 ()
    Note

    Funding agencies: Swedish Energy Agency [2012-004594, 30032-3]; Knut and Alice Wallenberg foundation [2010.0053]

    Available from: 2015-12-02 Created: 2015-12-02 Last updated: 2017-12-01Bibliographically approved
  • 8566.
    Bergqvist, Jonas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Determination of optical constants and phase transition temperatures in polymer fullerene thin films for polymer solar cells2012Conference paper (Other academic)
    Abstract [en]

    Plastic photovoltaics combining semiconducting polymers with fullerene derivatives have the potentialto become the first cost efficient solar cells able to compete with fossil fuels. The maximum powerconversion efficiency is already 8.3%[1] , and new polymers arrive frequently in the search for efficienciesof 10%. As a first step in the screening of candidate materials, the optical constants of the purepolymer as well as the polymer blend with fullerenes are determined from Variable Angle SpectroscopicEllipsometry (VASE), using Tauc-Lorentz oscillator models, throughout the solar spectrum. Thesemodels are then used to predict the upper limits to photocurrent generation in devices, in transfermatrix simulations of the multilayer thin film photovoltaic devices. This forms an essential step in thechoice of materials for optimization in devices.Materials optics measurements are also used to deduce the phase diagram of polymer and polymerblend films. The glass transition temperature is very important for plastic solar cells and mustbe higher than the 80C a device can reach to avoid degradation during operation. Temperaturedependent ellipsometric measurements has proven to be a feasible way to determine phase transitionsin polymer thin films[2] . These transitions are displayed as a sudden change of the volumetricexpansion coefficient, and are manifested by an abrupt increase of thickness at the phase transitiontemperature. For thickness determination a Cauchy model is applied to the transparent infrared partof the spectra.References1. Z. He, C. Zhong, X. Huang, W-Y. Wong, H. Wu, L. Chen, S. Su, Y Cao, Advanced Materials 23, 4636(2011)2. M. Campoy-Quiles, P.G. Etchegoin, D.D.C. Bradley, Synthetic Metals 155, 279(2005)

  • 8567.
    Bergqvist, Jonas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    In situ reflectance imaging of organic thin film formation from solution2012Conference paper (Other academic)
  • 8568.
    Bergqvist, Jonas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Uniaxial anisotropy in PEDOT:PSS electrodes enhances the photo current at oblique incidence in organic solar cells2015Manuscript (preprint) (Other academic)
    Abstract [en]

    In this work an uniaxial anisotropic treatment of the transparent conductor PEDOT:PSS is included in the transfer matrix method (TMM), used to calculate the optical power dissipation in organic solar cells. PEDOT:PSS is known to be anisotropic and exhibit a weaker absorption and lower refractive index in the out of plane direction. For p-polarized light at large oblique incidence the inclusion of anisotropy show a gain of over 10% for the maximum photocurrent as compared to an isotropic treatment. Due to the interference in devices with reflecting bottom electrodes, the active layer absorption gain is not always occurring for the wavelengths with highest dichroism. This work show that using PEDOT:PSS as top electrode further strengthens the argument that thin film solar cells perform better than their silicon counterparts under oblique incidence. We also confirm previous studies showing that the optical interference maxima is shifted to slightly thicker films for oblique incidence for solar cells with reflective bottom electrodes.

  • 8569.
    Bergqvist, Jonas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Lindqvist, Camilla
    Chalmers, Sweden .
    Backe, Olof
    Chalmers, Sweden .
    Ma, Zaifei
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Tang, Zheng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Tress, Wolfgang
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Gustafsson, Stefan
    Chalmers, Sweden .
    Wang, Ergang
    Chalmers, Sweden .
    Olsson, Eva
    Chalmers, Sweden .
    Andersson, Mats R.
    Chalmers, Sweden .
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Müller, Christian
    Chalmers, Sweden .
    Sub-glass transition annealing enhances polymer solar cell performance2014In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 2, no 17, 6146-6152 p.Article in journal (Refereed)
    Abstract [en]

    Thermal annealing of non-crystalline polymer: fullerene blends typically results in a drastic decrease in solar cell performance. In particular aggressive annealing above the glass transition temperature results in a detrimental coarsening of the blend nanostructure. We demonstrate that mild annealing below the glass transition temperature is a viable avenue to control the nanostructure of a non-crystalline thiophene-quinoxaline copolymer: fullerene blend. Direct imaging methods indicate that coarsening of the blend nanostructure can be avoided. However, a combination of absorption and luminescence spectroscopy reveals that local changes in the polymer conformation as well as limited fullerene aggregation are permitted to occur. As a result, we are able to optimise the solar cell performance evenly across different positions of the coated area, which is a necessary criterion for large-scale, high throughput production.

  • 8570.
    Bergqvist, Jonas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Mauger, Scott
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Tvingstedt, Kristofer
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    In situ reflectance imaging of organic thin film formation from solution deposition2013In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 114, 89-98 p.Article in journal (Refereed)
    Abstract [en]

    In this work we present reflectance imaging as a suitable method for in situ monitoring of the drying process of film formation for organic photovoltaics (OPV) over large areas, as well as for lab-scale spin-coating. The drying wet film is illuminated with a narrow bandwidth LED with the specularly reflected light recorded by a video camera as the film dries and forms the active layer of the OPV cell. The interference fringes generated by the thinning wet film can be used to measure the rate of solvent evaporation and the drying time. Subsequent mapping elucidates variations in drying conditions over the substrate, which lead to variations in morphology formation. The technique is suitable for tracking thickness variations of the dry film, with a sensitivity of 10 nm, by comparing the intensity of the reflected light from the dry film to simulated interference conditions calculated for each thickness. The drying process is furthermore accurately simulated by an optical model considering the changes in refractive index as the amount of solvent decreases with respect to the solid content. This non-invasive in situ method represents an important monitoring tool for future large scale OPV manufacturing where high performing morphologies with uniform thickness have to be formed over very large areas.

  • 8571.
    Bergqvist, Jonas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Melianas, Armantas
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Andersson, Olof
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Lindqvist, Camilla
    INTERACT, Department of Engineering and Physics, Karlstad University, Karlstad, Sweden.
    Musumeci, Chiara
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Time-resolved morphology formation of solution cast polymer: fullerene blends revealed by in-situ photoluminescence spectroscopy2015Manuscript (preprint) (Other academic)
    Abstract [en]

    The nanoscale morphology of the photo-active layer in organic solar cells is critical for device efficiency. The photoactive layer is cast from solution and during drying both the polymer and the fullerene self-assemble to form a blend. Here, we introduce in-situ spectroscopic photoluminescence (PL) combined with laser reflectometry to monitor the drying process of an amorphous polymer:fullerene blend. When casting only the pristine components (polymer or PCBM only), the strength of PL emission is proportional to the solid content of the drying solution, and both kinetics reveal a rapid aggregation onset at the final stage of film drying. On the contrary, when casting polymer:fullerene blends, the strength of PL emission is proportional to the wet film thickness and reveals polymer/fullerene charge transfer (CT) already at the earliest stages of film drying, i.e. in dilute solutions. The proposed method allows to detect polymer/fullerene phase separation during film casting – from a reduction in the PL quenching rate as the film dries. Poor solvents lead to phase separation already at early stages of film drying (low solid content), resulting in a coarse final morphology as confirmed by atomic force microscopy (AFM). We therefore anticipate that the proposed method will be an important tool in the future development of processing inks, not only for solution-cast polymer:fullerene solar cells but also for organic heterojunctions in general.

  • 8572.
    Bergqvist, Jonas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Tholén, Erik A.
    al Institute of Technology (EPFL), Station 6, Lausanne, Switzerland.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    LED array scanner for inline characterization of thin film photovoltaic modules2016In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 157, no 17, 1057-1064 p.Article in journal (Refereed)
    Abstract [en]

    Thin film solar cells, and in particular printed organic solar cells, offer a potential route to a low cost power generation from sunlight. However, manufacturing these solar cells rapidly generates large areas that have to be characterized, preferably in-line for a direct feed back in the production process. Here we introduce the LEDimage, a LED array illumination induced photocurrent method suitable for high speed inline characterization and defect detection of organic solar cell modules. The LEDimage enables simultaneous illumination of all connected subcells without additional bias light. Each LED in the array is amplitude modulated at an individual frequency and the photocurrent response is Fourier transformed to generate a photocurrent map. Furthermore, the LEDimage can be used as a hand scanner for fast device characterization. We expect that LEDimage can be an effective research and industry tool for characterization of large area thin film solar cells.

  • 8573.
    Bergqvist, Jonas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Tress, Wolfgang
    Laboratory of Photonics and Interfaces, Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland.
    Forchheimer, Daniel
    Nanostructure Physics, KTH Royal Institute of Technology, Stockholm, Sweden.
    Melianas, Armantas
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Tang, Zheng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Haviland, David
    Nanostructure Physics, KTH Royal Institute of Technology, Stockholm, Sweden.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    New method for lateral mapping of bimolecular recombination in thin film organic solar cells2016In: Progress in Photovoltaics, ISSN 1062-7995, E-ISSN 1099-159X, Vol. 24, no 8, 1096-1108 p.Article in journal (Refereed)
    Abstract [en]

    The best organic solar cells are limited by bimolecular recombination. Tools to study these losses are available; however, they are only developed for small area (laboratory-scale) devices and are not yet available for large area (production-scale) devices. Here we introduce the Intermodulation Light Beam-Induced Current (IMLBIC) technique, which allows simultaneous spatial mapping of both the amount of extracted photocurrent and the bimolecular recombination over the active area of a solar cell. We utilize the second-order non-linear dependence on the illumination intensity as a signature for bimolecular recombination. Using two lasers modulated with different frequencies, we record the photocurrent response at each modulation frequency and the bimolecular recombination in the second-order intermodulation response at the sum and difference of the two frequencies. Drift-diffusion simulations predict a unique response for different recombination mechanisms. We successfully verify our approach by studying solar cells known to have mainly bimolecular recombination and thus propose this method as a viable tool for lateral detection and characterization of the dominant recombination mechanisms in organic solar cells. We expect that IMLBIC will be an important future tool for characterization and detection of recombination losses in large area organic solar cells.

  • 8574.
    Bergqvist, Jonas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Tvingstedt, Kristofer
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    In situ reflectance imaging of organic thin film formation from solution2012Conference paper (Other academic)
    Abstract [en]

    The rapid progress of organic photovoltaic devices during the last decade, with power conversion efficiencies now exceeding 8%, has brought the technology close to an industrial breakthrough. For polymer solar cells, roll to roll printing is desired to gain the production advantage. The formation of the photoactive material from solutions needs to be controlled and optimized. Therefore a suitable method to monitor the deposition process is needed as deviations of drying times1 and drying rates2 during the coating process have proven to generate morphology variations causing variations in photocurrent generation.

    Here we demonstrate how reflectance imaging can be used to monitor the drying process, both for spin coating and blade coating deposition. A blue LED is used as light source to generate specular reflections imaged by a CMOS camera. The thinning of the wet film can then be observed by thin film interference, and can be recorded for each pixel. This enables an estimation of the evaporation rate for each pixel mapped over the substrate. For spin coating the evaporation rate is shown to increase with the distance from the rotation center, whereas the air flow is the determining parameter during blade coating. By mapping the times when interference ceases, lateral variations in drying time are visualized. Furthermore the quenching of polymer photoluminescence during the drying process can be visualized, thus creating a possibility to estimate morphological variations. Moreover lateral thickness variations of the dry film can be visualized by scanning ellipsometry. After depositing a top electrode photocurrent images can be generated by a laser scanning method. This allows for a direct comparison of drying conditions and photocurrent generation.  The possibility to monitor the thin film formation as well as lateral variations in thickness in-situ by a non-invasive method, is an important step for future large scale applications where stable high performing generating morphologies have to be formed over large areas.

    1Schmidt-Hansberg, B.; Sanyal, M.; Klein, M.F.G.; Pfaff, M.; Schnabel, N.; Jaiser, S.; Vorobiev, A.; Müller, E.; Colsmann, A.; Scharfer, P.; Gerthsen, D.; Lemmer, U.; Barrena, E.; and Schabel, W., ACS Nano 5 , 2011, 8579-8590

    2 Hou, L.; Wang, E.; Bergqvist, J.; Andersson, V.B.; Wang, Z.; Müller, C.; Campoy-Quiles, M.; Andersson, M.R.; Zhang, F.; Inganäs, O.,Adv. Func. Mat. 21 , 2011, 3169–3175

  • 8575.
    Bergqvist, Jonna
    Linköping University, Department of Culture and Communication. Linköping University, Faculty of Arts and Sciences.
    En bild säger mer än tusen ord: En analys av svenska barnboksillustrationer2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Att en bild säger mer än tusen ord är ett känt uttryck, att bilder talar till läsaren och innehåller väldigt mycket information som inte framkommer i ord är inget nytt. Bilden fyller många funktioner där den informerar, suggererar, pläderar och manar (Fridell, 1982, s. 12). Edwards kallar bildspråket för ett av våra allra första språk, vi börjar rita så fort vår hand kan greppa en krita, oavsett vilket modersmål vi har (Edwards, 2008, s. 93). Jag har i mitt arbete analyserat fem olika bilderböcker som är illustrerade av svenska illustratörer. Syftet med uppsatsen är att undersöka hur våra samtida illustrationer riktade till barn ser ut. Vilka bilder ser barn i dagens bilderböcker och vilka identifieringsmöjligheter erbjuds.

    I analysen har jag tittat på hur illustratörerna Lisen Adbåge, Gunna Grähs, Anna Höglund, Olof Lindström och Sven Nordqvist skildrar personerna och miljön, hur de använder bildrummet och visar på rörelser i bilden samt hur vi kan förstå personernas känslor och relationer till varandra. Studiens resultat visar att de flesta böckerna låter text och bild dela på uppgiften att berätta handlingen, de berättar om karaktärerna, deras känslor och omgivning. De fem utvalda böckerna har stora likheter, fyra av dem utspelar sig i stadsmiljö, de har endast två huvudpersoner och handlingen utspelar sig under en kort tid, allt för att passa små barn. Berättelserna är förhållandevis verklighetstrogna, med undantag för Sunkan som kan flyga och Findus som är en talande katt. Vi möter barn och vuxna i vardagliga händelser som gör det möjligt för det lilla barnet att känna igen sig och identifiera sig med karaktärerna.

  • 8576.
    Bergqvist, Kerstin
    Linköping University, Faculty of Educational Sciences. Linköping University, Department of Behavioural Sciences, Teaching and Learning in School, Teacher Education and other Educational Settings.
    Discourse and classroom practices. Reflectivity and responsibility in learning and instruction2001In: Nordisk Pedagogik, ISSN 0901-8050, E-ISSN 1504-2995, Vol. 21, no 2, 82-91 p.Article in journal (Refereed)
  • 8577.
    Bergqvist, Kerstin
    Linköping University, Department of Behavioural Sciences and Learning, Teaching and Learning in School, Teacher Education and other Educational Settings. Linköping University, Faculty of Health Sciences.
    Doing schoolwork: task premisses and joint activity in the comprehensive classroom1990Doctoral thesis, monograph (Other academic)
    Abstract [en]

    This study is about teaching and learning as institutionalized phenomena. In particular interest is focused on two issues; firstly, the concrete premisses for learning and communication in what in Swedish school rhetoric is referred to as "student-active" and co-operative working forms, and, secondly, what according to the actors qualifies as work and productive learning in such contexts. The rationale for focussing on groupwork is the wide spread assumption in curricular documents as well as in school ideology about the appropriateness of this approach to teaching and learning for dealing with some of the difficulties that teachers face in the comprehensive classroom, e. g. large differences in motivation and academic ability. Group work is also an essential ingredient in a child-centered ideology in which learning is seen as the result of direct studentinvolvement in the definition and implementation of learning goals.

    Theoretically, the study has its basis within an interactionist interpretive tradition, viewing school as a socially constructed and negotiated world. The methodological approach is inspired by research made within anthropology and ethnography. Data is drawn from fieldwork during one school year in two classes in grade 7 at the secondary level of the Swedish comprehensive school. The main sources of the data areobservations and field notes from lessons, breaks and outdoor activities and from conversations with the students, tape-recordings of group work and interviews with students. Group work in Science, Swedish and Social Science was used as case studies to illustrate significant features of schoolwork in the classroom.

    The study shows that success in schoolwork is a question of knowing and adhering to implicit educational "ground rules". Even "student-active" working forms and fairly "open" tasks presuppose specific interpretations by the students. Tasks have to be transformed in such a way that they fit the time constraints and the constraints with respect to what qualifies as knowledge in the particular context of school. This means that the possibilities of letting students who vary in their social background and academic orientation share the conversational floor and assume responsibility for the work diminish. It is also shown that the assumption of the superiority of inductive forms of learning appears highty questionable if one looks at what students do in such settings. Students were generally not aware of the wider- theoretical- contexts for a particular task since endpoints of activities were kept implicit in accordance with an inductive learning philosophy. Often there was no shared understanding of the premisses for work among teachers and students, and all students were not involved in the specific kind of work that was intended. Thus, the students had difficulties in identifying thecommunicative contexts in which the tasks were to be interpreted and the concrete activity often replaced genuine learning and understanding.

    The results are discussed in relation to an inductive, child-centered ideology of teaching and learning. It is maintained that the implicitness in teaching obscures learning goals. Instead, premisses should be made explicit and students should be more actively guided into participating in learning activities.

  • 8578.
    Bergqvist, Kerstin
    Linköping University, Faculty of Educational Sciences. Linköping University, Department of Behavioural Sciences, Teaching and Learning in School, Teacher Education and other Educational Settings.
    Eget arbete-eget ansvar2007In: Forskning om lärares arbete i klassrummet / [ed] Kjell Granström, Stockholm: Myndigheten för skolutveckling , 2007, 95-108 p.Chapter in book (Other academic)
    Abstract [sv]

    Denna kunskapsöversikt har kommit till tack vare ett samlat engagemang inom forskningsmiljön om lärares arbete vid Linköpings universitet. Flera av forskarna medverkar också i nätverket om lärares arbete, som leds från Högskolan i Kalmar. Forskarna i Linköpingsmiljön har bidragit till att öka våra kunskaper om lärares och elevers arbete i klassrummet. Texterna i boken koncentreras till de baskunskaper som alla lärare är ansvariga för visavi eleverna. Samtidigt behandlas den professionella lärarens roll att ge utrymme för eleverna att även diskutera centrala frågor som demokrati, rättvisa, jämställdhet m.m. Lärares arbete handlar inte bara om innehållet utan också om de omgivande faktorernas betydelse t.ex. organisations-, undervisnings-, mål- och metodfrågor. Hemarbete, individuellt arbete och olika syn på lärande och undervisning behandlas också.

  • 8579.
    Bergqvist, Kerstin
    Linköping University, Faculty of Educational Sciences. Linköping University, Department of Behavioural Sciences, Teaching and Learning in School, Teacher Education and other Educational Settings.
    Examensarbetet. Ett bidrag till vetenskaplighet i lärarutbildningen2000In: Pedagogisk forskning i Sverige, ISSN 1401-6788, E-ISSN 2001-3345, Vol. 5, no 1Article in journal (Refereed)
  • 8580.
    Bergqvist, Kerstin
    Linköping University, Faculty of Educational Sciences. Linköping University, Department of Behavioural Sciences, Teaching and Learning in School, Teacher Education and other Educational Settings.
    Planering av eget arbete - ett förändrat innehåll i undervisning2005In: Eget arbete - en kameleont i klassrummet: perspektiv på ett arbetssätt från förskola till gymnasium / [ed] Eva Österlind, Lund: Studentlitteratur , 2005, 1, 61-75 p.Chapter in book (Other academic)
    Abstract [sv]

    Individuellt organiserat skolarbete – eget arbete – är ett arbetssätt som blivit allt vanligare i undervisningen. Detta antyder att eget arbete löser vissa praktiska problem, till exempel i samband med åldersintegrerad undervisning och ökad datoranvändning i klassrummen. Eget arbete har visat sig kunna anta skiftande former beroende på lärarens intentioner, ämnesfokus och elevernas ålder, men innehåller alltid inslag av elevers planering och ansvar. Trots arbetssättets genomslagskraft har forskningen kring eget arbete tagit fart först på senare år, vilket innebär att det inte blivit mångsidigt belyst och diskuterat förrän nu.

    I antologin ges exempel på hur lärare resonerat när eget arbete införts och hur arbetssättet har utvecklats och förändrats över tid: Vad händer när eget arbete möter andra undervisningstraditioner? Kan eget arbete vara samarbete? Hur upplever barn och ungdomar i olika åldrar att planera och ”ta ansvar” för sitt lärande? Hur påverkas lärarrollen? Eget arbete granskas framför allt ur barn-, elev- och lärarperspektiv men även genom jämförelser mellan skolor. Merparten av kapitlen bygger på forskning, medan ett par kapitel består av mer personliga beskrivningar och reflexioner. Genom att på detta vis belysa eget arbete från olika utgångspunkter synliggörs både dess kärna och variationsrikedom.

  • 8581.
    Bergqvist, Kerstin
    Linköping University, Department of Behavioural Sciences, Teaching and Learning in School, Teacher Education and other Educational Settings. Linköping University, Faculty of Educational Sciences.
    Plötsligt kom universitetet in i undervisningen1999In: Möten-en vänbok till Roger Säljö / [ed] Ullabeth Sätterlund Larsson, Kerstin Bergqvist, Linköping: Tema Kommunikation, Univ. , 1999, 169-193 p.Chapter in book (Other academic)
  • 8582.
    Bergqvist, Kerstin
    Linköping University, Faculty of Educational Sciences. Linköping University, Department of Behavioural Sciences, Teaching and Learning in School, Teacher Education and other Educational Settings.
    Samtal om planering2005In: Grundskoletidningen, ISSN 1652-7844, Vol. 4, 36-41 p.Article in journal (Other (popular science, discussion, etc.))
  • 8583.
    Bergqvist, Kerstin
    Linköping University, Faculty of Educational Sciences. Linköping University, Department of Behavioural Sciences, Teaching and Learning in School, Teacher Education and other Educational Settings.
    Skolarbete som interaktion2001In: Interaktion i pedagogiska sammanhang / [ed] Karl-Georg Ahlström; Fritjof Sahlström; Sverker Lindblad, Stockholm: Liber , 2001, 1, 36-52 p.Chapter in book (Other academic)
    Abstract [sv]

    Hur går det till när barn leker eller när ungdomar samtalar i skolan, och vad betyder leken och samtalen för deras lärande, socialisation och identitetsskapande? Författarna till Interaktion i pedagogiska sammanhang presenterar ett perspektiv för att svara på sådana frågor, och visar i sex undersökande kapitel hur perspektivet kan användas. Bokens utgångspunkt är konstruktionistisk. Det innebär att socialisation och lärande ses som något skapat i interaktion. Med den utgångspunkten är det nödvändigt att i detalj analysera barn och ungdomars interaktion - med varandra och med vuxna - för att förstå vilka erfarenheter de gör i olika pedagogiska sammanhang.

  • 8584.
    Bergqvist, Kerstin
    Linköping University, Department of Behavioural Sciences and Learning, Education, Teaching and Learning. Linköping University, Faculty of Educational Sciences.
    Ungdomar och skolarbete: om förhållningssätt och samtal på högstadiet1995In: Korsvägar: en antologi om möten mellan unga och institutioner förr och nu / [ed] Kerstin Bergqvist, Kenneth Petersson, Maria Sundkvist, Stockholm: Symposion Brutus Östlings bokförlag, 1995, 167-190 p.Chapter in book (Other academic)
  • 8585.
    Bergqvist, Kerstin
    Linköping University, Department of Behavioural Sciences, Teaching and Learning in School, Teacher Education and other Educational Settings. Linköping University, Faculty of Educational Sciences.
    Var dags samtal i klassrummet1999In: Miljöer för lärande / [ed] Ingrid Carlgren, Lund: Studentlitteratur , 1999, 135-154 p.Chapter in book (Other academic)
  • 8586.
    Bergqvist, Kerstin
    Linköping University, Faculty of Educational Sciences. Linköping University, Department of Behavioural Sciences, Teaching and Learning in School, Teacher Education and other Educational Settings.
    Vi lärde oss bara sätta fast lampor och grejer på bänken1999In: Pedagogiska magasinet : Lärarförbundets tidskrift för pedagogisk forskning och debatt, ISSN 1401-3320, Vol. 9, no 3, 27-31 p.Article in journal (Other (popular science, discussion, etc.))
    Abstract [sv]

      

  • 8587.
    Bergqvist, Kerstin
    et al.
    Linköping University, Faculty of Educational Sciences. Linköping University, Department of Behavioural Sciences, Teaching and Learning in School, Teacher Education and other Educational Settings.
    Evaldsson, Ann-Carita
    Pedagogiska institutionen Uppsala universitet.
    Lindblad, Sverker
    Pedagogiska institutionen Uppsala universitet.
    Sahlström, Fritjof
    Pedagogiska institutionen Uppsala universitet.
    Introduktion och forskningsöversikt2001In: Interaktion i pedagogiska sammanhang, Stockholm: Liber , 2001, 1, 9-35 p.Chapter in book (Other academic)
    Abstract [sv]

    Hur går det till när barn leker eller när ungdomar samtalar i skolan, och vad betyder leken och samtalen för deras lärande, socialisation och identitetsskapande? Författarna till Interaktion i pedagogiska sammanhang presenterar ett perspektiv för att svara på sådana frågor, och visar i sex undersökande kapitel hur perspektivet kan användas. Bokens utgångspunkt är konstruktionistisk. Det innebär att socialisation och lärande ses som något skapat i interaktion. Med den utgångspunkten är det nödvändigt att i detalj analysera barn och ungdomars interaktion - med varandra och med vuxna - för att förstå vilka erfarenheter de gör i olika pedagogiska sammanhang.

  • 8588.
    Bergqvist, Kerstin
    et al.
    Linköping University, Department of Behavioural Sciences, Teaching and Learning in School, Teacher Education and other Educational Settings. Linköping University, Faculty of Educational Sciences.
    Petersson, KennethLinköping University, Department of Social and Welfare Studies, Society, Diversity, Identity. Linköping University, Faculty of Arts and Sciences.Sundkvist, MariaLinköping University, The Tema Institute, Department of Child Studies. Linköping University, Faculty of Arts and Sciences.
    Korsvägar. En antologi om möten mellan unga och institutioner förr och nu1995Collection (editor) (Other academic)
    Abstract [sv]

    Vad är det som händer ute på de olika institutioner där barn och ungdomar tillbringar stora delar av sina liv? Varför vill vuxna i till exempel skolan en sak, medan de unga vanligen är intresserade av någonting helt annat? Det är sådana frågor som Korsvägar försöker ge svar på. Bokens titel syftar på de ibland konfliktfyllda möten som sker mellan barn, ungdomar och vuxna. De olika artiklarna vill synliggöra spelet mellan unga och olika institutioner utifrån de ungas perspektiv. Likaså studeras hur de vuxnas ideal om den goda barn- och ungdomstiden förändrats under de senaste hundra åren och hur ungdomarna förhållit sig till detta.  

  • 8589.
    Bergqvist, Kerstin
    et al.
    Linköping University, Faculty of Educational Sciences. Linköping University, Department of Behavioural Sciences, Teaching and Learning in School, Teacher Education and other Educational Settings.
    Säljö, Roger
    Inst för pedagogik och didaktik Göteborgs universitet.
    Conceptually blindfolded in the optics laboratory. Dilemmas of inductive learning.1994In: European Journal of Psychology of Education, ISSN 0256-2928, E-ISSN 1878-5174, Vol. IX, no 1, 149-158 p.Article in journal (Refereed)
  • 8590.
    Bergqvist, Kerstin
    et al.
    Linköping University, Faculty of Educational Sciences. Linköping University, Department of Behavioural Sciences, Teaching and Learning in School, Teacher Education and other Educational Settings.
    Säljö, Roger
    Institutionen för pedagogik och didaktik Göteborgs universitet.
    Learning to plan. A study of reflexivity and discipline in modern pedagogy.2004In: Dialogic learning: shifting perspectives to learning, instruction, and teaching / [ed] Jos van der Linden and Peter Renshaw, Dordrecht: Kluwer Academic Publishers , 2004, 109-124 p.Chapter in book (Other academic)
    Abstract [en]

    This book shows the importance of a more socially grounded account on learning, instruction and teaching at and between different levels: meta-theory, theory, methods and educational practices. Three main questions are dealt with in the research presented in the book:

    • what are the affordances and constraints of a dialogic view of knowing, knowledge, and learning;
    • how useful it is to integrate contemporary learning mechanisms and concepts (like elaboration, metacognition) within a dialogic framework;
    • what are the educational implications of a dialogic view of knowing and learning
  • 8591.
    Bergqvist, Malin
    Linköping University, Department of Computer and Information Science. Linköping University, Faculty of Arts and Sciences.
    ​Ökad mobilitet, delaktighet och frihet ― IKT-stöd som fyller verkliga behov inom äldreomsorg: Behovskartläggning för kommunikation och information mellan omsorgstagare, närstående och utförare som grund till en gemensam kontaktyta2014Independent thesis Basic level (degree of Bachelor), 12 credits / 18 HE creditsStudent thesis
    Abstract [en]

    Sweden’s population is steadily growing older and while the demand for care of senior citizens is increasing, care givers are forced to cope with diminishing resources in terms of money and qualified staff. Many put hope in new eHealth technology, as a means of raising efficiency and quality in the every day working situation. This thesis aims to study needs regarding communication, information and interaction between care takers, dependants and caregivers in geriatric care, in order to create a foundation upon which an ICT system may be built to fulfill those needs. The results presented are part of a research project focusing on future ICT systems in healthcare. Data was collected through an observational study, group discussions with informants related to care takers, and qualitative interviews with 13 informants who have extensive experience of geriatric care. The results imply there are existing problems that may be avoided by facilitating information sharing between the aforementioned groups. The study also presents some important points of discussion regarding usefulness, clashing needs of different users, and the balance between simplicity of use and system size.

  • 8592.
    Bergqvist, Mathias
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Extending a Game Concept’s Scope of use by Adapting Mobile Platform Usage2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The report features the technical fundamentals, implementation, results and discussions within the field of mobile application development in the game industry. The thesis explored the game industry from within the industry, as the purpose was to further expand the game concept of the PC game theHunter by using a mobile platform. In the age of the multi-touch smartphone, applications are a huge and competitive industry withmany interesting development approaches. Using the fundamental principles of system architecture and interface design for mobile development, a game companion application based in an Android environment was developed. Game data was provided by the game development studio Expansive Worlds. The results showed support for the platform, but clearly states that further development is needed to actually explore the mobile market further. Implications for the results of the study and future tasks are discussed.

  • 8593.
    Bergqvist, Mattias
    Linköping University, Department of Management and Engineering, Carl Malmsten - furniture studies. Linköping University, Faculty of Science & Engineering.
    Med MODE som INSPIRATION: Hur kan ett gränsöverskridande skapande se ut?2015Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    This work is about transcending in to another environment to discover new inspiration and new paths. It’s about borrowing from other areas of art/design to find different passages in to your own creativity. Without having a clear vision beforehand of how the end result would turn out, I wanted to explore how a fusion design process would look. I used the world of fashion as my starting point, the designer Diana Orving lead the way and I designed freely from that platform. By learning more from that other world, the world of fashion, I got a bigger insight in my own! Physically it resulted in a folding wall that symbolizes what I want to work with in the future.

  • 8594. Bergqvist, Michael
    et al.
    Sörenson, Sverre
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Pulmonary Medicine. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Respiratory Medicine UHL.
    Brattström, Baniel
    Mok, Tony
    Henriksson, Roger
    Role of non-taxane-containing chemotherapy in advanced non-small cell lung cancer2006In: American Journal of Cancer, ISSN 1175-6357, E-ISSN 2230-6064, Vol. 5, no 4, 223-244 p.Article in journal (Refereed)
    Abstract [en]

    Treatment for advanced-stage NSCLC generally includes the use of systemic chemotherapy as well as biologic therapies (targeted therapy) at later stages of the disease. However, in general, NSCLC is moderately sensitive to the currently available cytotoxic drugs, so the intention of chemotherapeutic treatment in the advanced setting is mainly palliative. Several treatment regimens are available, but in the first-line setting, treatment traditions differ both within countries and between various parts of the world. The role of taxaneplatinum chemotherapeutic combinations (mainly used in North America) has been questioned in the palliative setting since these combinations are known to cause neutropenia, skin and nail problems, as well as neurological toxicity. This review aims to summarize the current knowledge about the role of non-taxane therapy for patients with advanced NSCLC, with a focus on gemcitabine, vinorelbine, etoposide, pemetrexed, irinotecan, epidermal growth factor receptor (EGFR)-inhibiting agents, angiogenesis inhibitors, and small molecules. The compilation of literature in the present review indicates that the use of non-taxane treatment for patients with advanced NSCLC has an anti-tumor effect that is not different from that which can be seen with various taxane combinations. Furthermore, the combination of cisplatin with gemcitabine or vinorelbine seems to be a most compelling regimen in the first-line setting because of its modest toxicity (when administered by experienced staff), favorable clinical response, and relatively low drug cost. It is also clear that the novel therapies (EGFR inhibitors and inhibitors of angiogenesis) that have been approved so far will be of great clinical value, however, their use will be restricted to small, well defined, subpopulations of patients. The great challenge now is to define the populations benefiting from these novel therapies. © 2006 Adis Data Information BV. All rights reserved.

  • 8595.
    Bergqvist, Niclas
    et al.
    Linköping University, Department of Biomedical Engineering. Linköping University, Faculty of Science & Engineering.
    Nyman, Elin
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering. AstraZeneca RandD, Sweden.
    Cedersund, Gunnar
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Clinical and Experimental Medicine. Linköping University, Faculty of Medicine and Health Sciences.
    Stenkula, Karin G.
    Lund University, Sweden.
    A systems biology analysis connects insulin receptor signaling with glucose transporter translocation in rat adipocytes2017In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 292, no 27, 11206-11217 p.Article in journal (Refereed)
    Abstract [en]

    Type 2 diabetes is characterized by insulin resistance, which arises from malfunctions in the intracellular insulin signaling network. Knowledge of the insulin signaling network is fragmented, and because of the complexity of this network, little consensus has emerged for the structure and importance of the different branches of the network. To help overcome this complexity, systems biology mathematical models have been generated for predicting both the activation of the insulin receptor (IR) and the redistribution of glucose transporter 4 (GLUT4) to the plasma membrane. Although the insulin signal transduction between IR and GLUT4 has been thoroughly studied with modeling and time-resolved data in human cells, comparable analyses in cells from commonly used model organisms such as rats and mice are lacking. Here, we combined existing data and models for rat adipocytes with new data collected for the signaling network between IR and GLUT4 to create a model also for their interconnections. To describe all data (amp;gt;140 data points), the model needed three distinct pathways from IR to GLUT4: (i) via protein kinase B (PKB) and Akt substrate of 160 kDa (AS160), (ii) via an AS160-independent pathway from PKB, and (iii) via an additional pathway from IR, e.g. affecting the membrane constitution. The developed combined model could describe data not used for training the model and was used to generate predictions of the relative contributions of the pathways from IR to translocation of GLUT4. The combined model provides a systems-level understanding of insulin signaling in rat adipocytes, which, when combined with corresponding models for human adipocytes, may contribute to model-based drug development for diabetes.

  • 8596.
    Bergqvist, Petter
    Linköping University, Department of Computer and Information Science.
    Förebildsanalys som grund i agil utveckling: en studie i prioritering av bruksegenskaper2010Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Att utveckla ett program som lyckas uppfylla alla förväntningar som en användare kan ha är svårt.Att utveckla ett program som lyckas uppfylla vissa av alla de förväntningar en användare kan ha ärbetydligt mycket lättare. Men att kunna hitta just de egenskaperna som gör att en användare inteblir besviken utan nöjd med ett program är en svår process. Ett sätt att hitta de egenskaperna kanvara genom att nyttja en användarcentrerad metod som extrem programmering. Agil utvecklingoch extrem programmering har som område fokuserat relativt lite på användarnöjdhet som måttför att avgöra om ett program är lyckat eller ej.Med detta som bakgrund har ett utvecklingsprojekt tagit form med syfte att utveckla ettmodelleringsverktyg för analysmetoden FRAM. I detta projekt har en metod bestående av delsförebildsanalys och agil utveckling legat som grund. För att gruppera och prioriteraprogramegenskaper har Kanos modell för kundnöjdhet använts.Uppsatsen visar att en metod som grundar sig i förebildsanalys kan användas för att ta fram demest basala egenskaperna hos en artefakt. Detta i kontrast till viss agil utveckling ska det visa sig.Uppsatsen visar även på att den tillgängliga tiden för ett utvecklingsprojekt kan vara avgörande förvilka sorts egenskaper man utvecklar

  • 8597.
    Bergqvist, Ulrika
    et al.
    Linköping University, Department of Management and Economics.
    Hermansson, Anna
    Linköping University, Department of Management and Economics.
    Varumärkesinriktad positionering: en fallstudie av ICAs&Nordeas etablering i Estland2003Independent thesis Advanced level (degree of Magister)Student thesis
    Abstract [sv]

    Bakgrund: Bland annat ett stundande EU-inträde och en stark ekonomisk tillväxt har bidragit till att Estland utvecklats till att bli en mycket intressant marknad för svenska företag. För att företag ska klara sig långsiktigt i konkurrensen på den estniska marknaden krävs en tydlig positionering av dess varumärke. ICA och Nordea är två företag med starka varumärken på den svenska marknaden, vilka dessutom är etablerade på den estniska marknaden.

    Syfte: Syftet är att jämföra ICAs respektive Nordeas varumärkespositionering i Sverige och Estland för att utröna om det krävs en anpassning av denna vid en nyetablering i Estland.

    Avgränsningar: Vi behandlar enbart respektive fallföretags kärnverksamhet. Inga kulturella aspekter kommer att beröras. Genomförande: Det empiriska materialet har inhämtats genom intervjuer inom respektive företag.

    Resultat: Fallföretagens respektive varumärkespositionering är relativt standardiserad. Dock anpassas företagens strategier något efter rådande marknadssituation i Estland.

  • 8598.
    Bergren, Åsa
    et al.
    Institutionen för arkeologi och anti¬kens historia, Lunds universitet, Sverige.
    Nilsson Stutz, Liv
    Oxford College of Emory University, UK.
    Ett utmanat koncept?: Ritualbegreppets möte med arkeologin2010In: Den rituella människan: Flervetenskapliga Perspektiv / [ed] Anne-Christine Hornborg, Linköping: Linköping University Electronic Press , 2010, 25-52 p.Chapter in book (Other academic)
    Abstract [sv]

    Begreppet ritual är problematiskt. Sedan 1990-talets början har forskningen på området i allt högre grad kommit att ifrågasätta användningen av begreppet (Bell 1992; Humphrey & Laidlaw 1994; Thinès & de Heusch 1995; Stausberg 2002). Samtidigt som tidigare definitioner av begreppet har problematiserats, har det också vidgats till att omfatta allt fler kategorier av handlingar. Ämnet har också rört sig från sin religionshistoriska vagga och blivit en egen disciplin: Ritual Studies, som förutom religionsvetenskap och socialantropologi också inkluderar ämnen som konstvetenskap, teatervetenskap, litteraturvetenskap, etologi, etno-logi, psykologi, sociologi osv. Vi vill här visa att också arkeologin har en plats i denna diskussion.

  • 8599.
    Bergseth, Brita
    Linköping University, Department of Behavioural Sciences and Learning. Linköping University, Faculty of Educational Sciences.
    Har externa granskningar av kvalitetsarbete någon effekt på kvaliteten i högre utbildning för yrken inom medicin och vård?Manuscript (preprint) (Other academic)
    Abstract [sv]

    svenska universitet och högskolor med bedömningar av utbildningarnas kvalitet. Jämförelsen gjordes mellan de externa kvalitetsgranskningar som Högskoleverket genomförde 1995-2007 av 24 lärosäten och 119 utbildningsprogram för yrken inom medicin och vård. Slutsatsen är att det inte går att påvisa något statistiskt signifikant samband mellan utfallen av granskningarna. Resultaten indikerar istället att de omfattande nationella insatser som gjorts under sju års tid i syfte att driva kvalitetsutveckling inte lett till någon konstaterbart högre kvalitet i utbildningarna fyra till sex år senare. Det är visserligen svårt att urskilja och kvantifiera effekterna av kvalitetsarbetet isolerat från övriga faktorer som styr högre utbildning. Men den modell och de mätmetoder som Högskoleverket använt sig av för att bedöma lärosätenas kvalitetsarbete visar sig samtidigt också ha brister i validitet, reliabilitet och relevans. Granskningsmodellen syns vara svagt vetenskaplig underbyggd.

  • 8600.
    Bergseth, Brita
    Linköping University, Department of Behavioural Sciences and Learning. Linköping University, Faculty of Educational Sciences.
    Vägledande eller vilseledande?: Kvalitetsmätning och ranking av universitet och högskolor2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [sv]

    Få samhällsinstitutioner kan räkna sin historia lika långt tillbaka i tiden som universiteten. Utan tvekan kan akademin hävda sin hållbarhet som kunskapsorganisation. Det institutionella konceptet för att bedriva forskning och utbildning har under århundradenas lopp vunnit stora framgångar. Ett universitets auktoritet, autonomi och integritet är dock inte given.

    Sedan slutet av 1990-talet granskas, bedöms och rankas kvaliteten vid svenska lärosäten systematiskt av externa organisationer, offentliga myndigheter, intresseorganisationer och kommersiella medier både nationellt och internationellt. Syftet med granskningarna uppges som regel vara att informera en bred allmänhet och framför allt ge vägledning till blivande studenter om kvaliteten i högre utbildning. Men de modeller och metoder som tillämpas vid bedömningarna kan skilja sig åt väsentligt.

    I två empiriska studier analyseras och jämförs resultaten av tre skilda modeller för extern bedömning, mätning och rankning av kvaliteten vid 24 svenska universitet och högskolor. Modellerna har alla det gemensamt att bedömningarna baseras på högskolelagen och samma övergripande definition av begreppet kvalitet. Vilka faktorer som anses konstituera kvalitet varierar däremot liksom valet av data och metoder för kvalitetsmätning.

    I den första studien jämfördes resultaten från Högskoleverkets utvärdering av 119 utbildningsprogram inom medicin och vård med en kvalitetsranking av lärosäten som genomförts av en enskild förening, Urank. De statistiska analyser som gjordes av resultaten från de båda kvalitetsgranskningarna indikerade endast ett slumpmässigt samband. I flera fall var skillnaderna betydande.

    Också i den andra studien är utvärderingen av utbildningarna i medicin och vård ett av jämförelseobjekten. Den här gången jämfördes utfallen av utvärderingen med slutsatserna av de bedömningar som  Högskoleverket under en sjuårsperiod gjort av lärosätenas systematiska kvalitetsarbete. Inte heller dessa analyser indikerade något annat än ett statistiskt slumpmässigt samband.

    Resultaten bekräftar svårigheterna att finna valida, tillförlitliga och relevanta modeller för kvalitetsbedömningar och rankningar. Hittills har det inte vuxit fram några internationellt vedertagna instrument för mätning av kvaliteten i högre utbildning. Trots det har i synnerhet internationella universitetsrankningar, så kallade ’league tables’, fått ett kraftigt genomslag både som informationskälla och styrinstrument i utvecklingen vid universitet och högskolor.

    Erfarenheterna från undersökningarna ger flera skäl att förhålla sig kritisk till resultat av utvärderingar, kvalitetsmätningar och ranking. Externa icke-akademiska organisationer, myndigheter och media, äger för närvarande initiativet ifråga om information och bedömningar av kvaliteten i högre utbildning. En successiv förskjutning syns också i utvecklingen från kollegial styrning till management. Samtidigt riskeras att lärosätenas akademiska auktoritet och autonomi urholkas.

    Slutsatserna understryker behovet av fortsatt metodutveckling för att etablera robusta granskningsmodeller som kan vinna tilltro såväl hos  allmänheten som inom akademin själv.

    List of papers
    1. Ranking quality in higher education: guiding or misleading?
    Open this publication in new window or tab >>Ranking quality in higher education: guiding or misleading?
    2014 (English)In: Quality in Higher Education, ISSN 1353-8322, E-ISSN 1470-1081, Vol. 20, no 3, 330-347 p.Article in journal (Refereed) Published
    Abstract [en]

    The study examines two different models of measuring, assessing and ranking quality in higher education. Do different systems of quality assessment lead to equivalent conclusions about the quality of education? This comparative study is based on the rankings of 24 Swedish higher education institutions. Two ranking actors have independently assessed the quality of these institutions during the same year. The analysis focuses on the concepts of quality on which the rankings are based, the choice of quality indicators, as well as methods, data sources and assessors. Although both actors base their rankings on the same overarching definition of quality, their conclusions do not correspond. The statistical method applied in this review, Bland-Altman analysis, indicates no significant agreement between the qualitative and quantitative measurements of quality in higher education. On the contrary, in several cases there are remarkable differences.

    Keyword
    Quality assessment; ranking; higher education; medical and health care professions; qualitative and quantitative measurements
    National Category
    Pedagogy
    Identifiers
    urn:nbn:se:liu:diva-122139 (URN)10.1080/13538322.2014.976419 (DOI)
    Available from: 2015-10-20 Created: 2015-10-20 Last updated: 2017-12-01
    2. Har externa granskningar av kvalitetsarbete någon effekt på kvaliteten i högre utbildning för yrken inom medicin och vård?
    Open this publication in new window or tab >>Har externa granskningar av kvalitetsarbete någon effekt på kvaliteten i högre utbildning för yrken inom medicin och vård?
    (Swedish)Manuscript (preprint) (Other academic)
    Abstract [sv]

    svenska universitet och högskolor med bedömningar av utbildningarnas kvalitet. Jämförelsen gjordes mellan de externa kvalitetsgranskningar som Högskoleverket genomförde 1995-2007 av 24 lärosäten och 119 utbildningsprogram för yrken inom medicin och vård. Slutsatsen är att det inte går att påvisa något statistiskt signifikant samband mellan utfallen av granskningarna. Resultaten indikerar istället att de omfattande nationella insatser som gjorts under sju års tid i syfte att driva kvalitetsutveckling inte lett till någon konstaterbart högre kvalitet i utbildningarna fyra till sex år senare. Det är visserligen svårt att urskilja och kvantifiera effekterna av kvalitetsarbetet isolerat från övriga faktorer som styr högre utbildning. Men den modell och de mätmetoder som Högskoleverket använt sig av för att bedöma lärosätenas kvalitetsarbete visar sig samtidigt också ha brister i validitet, reliabilitet och relevans. Granskningsmodellen syns vara svagt vetenskaplig underbyggd.

    Keyword
    Högre utbildning, kvalitetsarbete, kvalitetsbedömning, medicin och vård, rankning, statistisk analys
    National Category
    Pedagogy
    Identifiers
    urn:nbn:se:liu:diva-122141 (URN)
    Available from: 2015-10-20 Created: 2015-10-20 Last updated: 2015-10-20Bibliographically approved
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