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  • 101.
    Airey, John
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Physics Didactics.
    Linder, Cedric
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Physics Didactics.
    Social semiotics in university physics education: Leveraging critical constellations of disciplinary representations2015Conference paper (Refereed)
    Abstract [en]

    Social semiotics is a broad construct where all communication is viewed as being realized through signs and their signification. In physics education we usually refer to these signs as disciplinary representations. These disciplinary representations are the semiotic resources used in physics communication, such as written and oral languages, diagrams, graphs, mathematics, apparatus and simulations. This alternative depiction of representations is used to build theory with respect to the construction and sharing of disciplinary knowledge in the teaching and learning of university physics. Based on empirical studies of physics students cooperating to explain the refraction of light, a number of theoretical constructs were developed. In this presentation we describe these constructs and examine their usefulness for problematizing teaching and learning in university physics. The theoretical constructs are: fluency in semiotic resources, disciplinary affordance and critical constellations.

    The conclusion formulates a proposal that has these constructs provide university physics teachers with a new set of meaningfully and practical tools, which will enable them to re-conceptualize their practice in ways that have the distinct potential to optimally enhance student learning.

     

     

    Purpose

    This aim of this theoretical paper is to present representations as semiotic resources in order to make a case for three related constructs that we see as being central to learning with multiple representations in university physics; fluency in semiotic resources, disciplinary affordance and critical constellations. We suggest that an understanding of these constructs is a necessary part of a physics lecturer’s educational toolbox.

     

    Why semiotics?

    The construct of representations as it is presently used in science education can, in our opinion, be unintentionally limiting since it explicitly excludes important aspects such as physical objects, (e.g. physics apparatus) and actions (e.g. measuring a value). Clearly, such aspects play a central role in sharing physics meaning and they are explicitly included as semiotic resources in a social semiotic approach. Van Leeuwen (2005:1) explains the preference for the term semiotic resource instead of other terms such as representation claiming that “[…] it avoids the impression that what a [representation] stands for is somehow pre-given, and not affected by its use”. Thus, the term semiotic resource encompasses other channels of meaning making, as well as everything that is generally termed external representations (Ainsworth, 2006).

     

    Why social semiotics?

    The reason for adopting social semiotics is that different groups develop their own systems of meaning making. This is often achieved either by the creation of new specialized semiotic resources or by assigning specific specialized meaning to more general semiotic resources. Nowhere is this more salient than in physics where the discipline draws on a wide variety of specialized resources in order to share physics knowledge. In our work in undergraduate physics education we have introduced three separate constructs that we believe are important for learning in physics: fluency in semiotic resources, disciplinary affordance and critical constellations.

     

    Fluency in semiotic resources

    The relationship between learning and representations has received much attention in the literature. The focus has often been how students can achieve “representational competence” (For a recent example see Linder et al 2014). In this respect, different semiotic resources have been investigated, including mathematics, graphs, gestures, diagrams and language. Considering just one of these resources, spoken language, it is clear that in order to share meaning using this resource one first needs to attain some sort of fluency in the language in question. We have argued by extension that the same holds for all the semiotic resources that we use in physics (Airey & Linder, 2009). It is impossible to make meaning with a disciplinary semiotic resource without first becoming fluent in its use. By fluency we mean a process through which handling a particular semiotic resource with respect to a given piece of physics content becomes unproblematic, almost second-nature. Thus, in our social semiotic characterization, if a person is said to be fluent in a particular semiotic resource, then they have come to understand the ways in which the discipline generally uses that resource to share physics knowledge. Clearly, such fluency is educationally critical for understanding the ways that students learn to combine semiotic resources, which is the interest of this symposium. However, there is more to learning physics than achieving fluency. For example:

     

    MIT undergraduates, when asked to comment about their high school physics, almost universally declared they could “solve all the problems” (and essentially all had received A's) but still felt they “really didn't understand at all what was going on”. diSessa (1993, p. 152)

     

    Clearly, these students had acquired excellent fluency in disciplinary semiotic resources, yet still lacked a qualitative conceptual understanding.

     

    The disciplinary affordance of semiotic resources

    Thus, we argue that becoming fluent in the use of a particular semiotic resource, though necessary, is not sufficient for an appropriate physics understanding. For an appropriate understanding we argue that students need to come to appreciate the disciplinary affordance of the semiotic resource (Fredlund, Airey, & Linder, 2012; Fredlund, Linder, Airey, & Linder, 2015). We define disciplinary affordance as the potential of a given semiotic resource to provide access to disciplinary knowledge. Thus we argue that combining fluency with an appreciation of the disciplinary affordance of a given semiotic resource leads to appropriate disciplinary meaning making. However, in practice the majority of physics phenomena cannot be adequately represented by one a single semiotic resource. This leads us to the theme of this symposium—the combination of multiple representations.

     

    Critical constellations – the significance of this work for the symposium theme

    The significance of the social semiotic approach we have outlined for work on multiple representations lies in the concept of critical constellations.

    Building on the work of Airey & Linder (2009), Airey (2009) suggests there is a critical constellation of disciplinary semiotic resources that are necessary for appropriate holistic experience of any given disciplinary concept. Using our earlier constructs we can see that students will first need to become fluent in each of the semiotic resources that make up this critical constellation. Next, they need to come to appreciate the disciplinary affordance of each separate semiotic resource. Then, finally, they can attempt to grasp the concept in an appropriate, disciplinary manner. In this respect, Linder (2013) suggests that disciplinary learning entails coming to appreciate the collective disciplinary affordance of a critical constellation of semiotic resources.

     

    Recommendations

    There are a number of consequences of this work for the teaching and learning of physics. First, we claim that teachers need to provide opportunities for their students to achieve fluency in a range of semiotic resources. Next teachers need to know more about the disciplinary affordances of the individual semiotic resources they use in their teaching (see Fredlund et al 2012 for a good example of this type of work).

    Finally, teachers need to contemplate which critical constellations of semiotic resources are necessary for making which physics knowledge available to their students. In this respect physics teachers need to appreciate that knowing their students as learners includes having a deep appreciation of the kinds of critical constellations that their particular students need in order to effectively learn physics

     

    References

    Ainsworth, S. (2006). DeFT: A conceptual framework for considering learning with multiple representations. Learning and Instruction, 16(3), 183-198.

    Airey, J. (2009). Science, Language and Literacy. Case Studies of Learning in Swedish University Physics. Acta Universitatis Upsaliensis. Uppsala Dissertations from the Faculty of Science and Technology 81. Uppsala  Retrieved 2009-04-27, from http://www.diva-portal.org/smash/record.jsf?pid=diva2%3A173193&dswid=-4725

    Airey, J., & Linder, C. (2009). A disciplinary discourse perspective on university science learning: Achieving fluency in a critical constellation of modes. Journal of Research in Science Teaching, 46(1), 27-49.

    diSessa, A. A. (1993). Toward an Epistemology of Physics. Cognition and Instruction, 10(2 & 3), 105-225.

    Fredlund, T., Airey, J., & Linder, C. (2012). Exploring the role of physics representations: an illustrative example from students sharing knowledge about refraction. European Journal of Physics, 33, 657-666.

    Fredlund, T., Linder, C., Airey, J., & Linder, A. (2015). Unpacking physics representations: towards an appreciation of disciplinary affordance. Phys. Rev. ST Phys. Educ. Res., 10( 020128 (2014)).

    Linder, A., Airey, J., Mayaba, N., & Webb, P. (2014). Fostering Disciplinary Literacy? South African Physics Lecturers’ Educational Responses to their Students’ Lack of Representational Competence. African Journal of Research in Mathematics, Science and Technology Education, 18(3). doi: 10.1080/10288457.2014.953294

    Linder, C. (2013). Disciplinary discourse, representation, and appresentation in the teaching and learning of science. European Journal of Science and Mathematics Education, 1(2), 43-49.

    van leeuwen, T. (2005). Introducing social semiotics. London: Routledge.

     

  • 102.
    Airey, John
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Physics Didactics. School of Languages and Literature, Linnæus University, Sweden.
    Linder, Cedric
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Physics Didactics.
    Teaching and Learning in University Physics: A Social Semiotic Approach2016Conference paper (Refereed)
    Abstract [en]

    Social semiotics is a broad construct where all communication is viewed as being realized through semiotic resources. In undergraduate physics we use a wide range of these semiotic resources, such as written and oral languages, diagrams, graphs, mathematics, apparatus and simulations. Based on empirical studies of undergraduate physics students a number of theoretical constructs have been developed in our research group (see for example Airey & Linder 2009; Fredlund et al 2012, 2014; Eriksson 2015). In this presentation we describe these constructs and examine their usefulness for problematizing teaching and learning in university physics. The theoretical constructs are: discursive fluency, discourse imitation, unpacking and critical constellations of semiotic resources.

    We suggest that these constructs provide university physics teachers with a new set of practical tools with which to view their own practice in order to enhance student 

    References

    Airey, J. (2006). Physics Students' Experiences of the Disciplinary Discourse Encountered in Lectures in English and Swedish.   Licentiate Thesis. Uppsala, Sweden: Department of Physics, Uppsala University.,

    Airey J. (2009). Science, Language and Literacy. Case Studies of Learning in Swedish University Physics. Acta Universitatis   Upsaliensis. Uppsala Dissertations from the Faculty of Science and Technology 81. Uppsala  Retrieved 2009-04-27, from   http://publications.uu.se/theses/abstract.xsql?dbid=9547

    Airey, J. (2014) Representations in Undergraduate Physics. Docent lecture, Ångström Laboratory, 9th June 2014 From   http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-226598

    Airey, J. & Linder, C. (2015) Social Semiotics in Physics Education: Leveraging critical constellations of disciplinary representations   ESERA 2015 From http://urn.kb.se/resolve?urn=urn%3Anbn%3Ase%3Auu%3Adiva-260209

    Airey, J., & Linder, C. (2009). "A disciplinary discourse perspective on university science learning: Achieving fluency in a critical   constellation of modes." Journal of Research in Science Teaching, 46(1), 27-49.

    Airey, J. & Linder, C. (in press) Social Semiotics in Physics Education : Multiple Representations in Physics Education   Springer

    Airey, J., & Eriksson, U. (2014). A semiotic analysis of the disciplinary affordances of the Hertzsprung-Russell diagram in   astronomy. Paper presented at the The 5th International 360 conference: Encompassing the multimodality of knowledge,   Aarhus, Denmark.

    Airey, J., Eriksson, U., Fredlund, T., and Linder, C. (2014). "The concept of disciplinary affordance"The 5th International 360   conference: Encompassing the multimodality of knowledge. City: Aarhus University: Aarhus, Denmark, pp. 20.

    Eriksson, U. (2015) Reading the Sky: From Starspots to Spotting Stars Uppsala: Acta Universitatis Upsaliensis.

    Eriksson, U., Linder, C., Airey, J., & Redfors, A. (2014). Who needs 3D when the Universe is flat? Science Education, 98(3),   412-442.

    Eriksson, U., Linder, C., Airey, J., & Redfors, A. (2014). Introducing the anatomy of disciplinary discernment: an example from   astronomy. European Journal of Science and Mathematics Education, 2(3), 167‐182.

    Fredlund 2015 Using a Social Semiotic Perspective to Inform the Teaching and Learning of Physics. Acta Universitatis Upsaliensis.

    Fredlund, T., Airey, J., & Linder, C. (2012). Exploring the role of physics representations: an illustrative example from students   sharing knowledge about refraction. European Journal of Physics, 33, 657-666.

    Fredlund, T, Airey, J, & Linder, C. (2015a). Enhancing the possibilities for learning: Variation of disciplinary-relevant aspects in   physics representations. European Journal of Physics.

    Fredlund, T. & Linder, C., & Airey, J. (2015b). Towards addressing transient learning challenges in undergraduate physics: an   example from electrostatics. European Journal of Physics. 36 055002.

    Fredlund, T. & Linder, C., & Airey, J. (2015c). A social semiotic approach to identifying critical aspects. International Journal for   Lesson and Learning Studies 2015 4:3 , 302-316

    Fredlund, T., Linder, C., Airey, J., & Linder, A. (2014). Unpacking physics representations: Towards an appreciation of disciplinary   affordance. Phys. Rev. ST Phys. Educ. Res., 10(020128).

    Gibson, J. J. (1979). The theory of affordances The Ecological Approach to Visual Perception (pp. 127-143). Boston: Houghton   Miffin.

    Halliday, M. A. K. (1978). Language as a social semiotic. London: Arnold.

    Linder, C. (2013). Disciplinary discourse, representation, and appresentation in the teaching and learning of science. European   Journal of Science and Mathematics Education, 1(2), 43-49.

    Norman, D. A. (1988). The psychology of everyday things. New York: Basic Books.

    Mavers, D. Glossary of multimodal terms  Retrieved 6 May, 2014, from http://multimodalityglossary.wordpress.com/affordance/

    van Leeuwen, T. (2005). Introducing social semiotics. London: Routledge.

    Wu, H-K, & Puntambekar, S. (2012). Pedagogical Affordances of Multiple External Representations in Scientific Processes. Journal of Science Education and Technology, 21(6), 754-767.

  • 103.
    Airey, John
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Physics Didactics.
    Linder, Cedric
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Physics Didactics.
    Tvåspråkig ämneskompetens? En studie av naturvetenskaplig parallellspråkighet i svensk högreutbildning.2010In: Språkvård och språkpolitik / [ed] Lars-Gunnar Andersson, Olle Josephson, Inger Lindberg, and Mats Thelander, Stockholm: Språkrådet/Norstedts , 2010, p. 195-212Chapter in book (Other academic)
  • 104.
    Airey, John
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Physics Didactics. Department of Mathematics and Science Education, Stockholm University.
    Simpson, Zachary
    University of Johannesburg.
    Multimodal Science and Engineering Teaching: Perspectives from 8ICOM2018In: 9ICOM - Complete Book Of Abstracts, Odense, Denmark.: Syddansk Universitet, 2018Conference paper (Other academic)
    Abstract [en]

    Multimodal Science and Engineering Teaching: Perspectives from 8ICOM

    The previous international conference on multimodality – 8ICOM – featured two sessions devoted to multimodal, social semiotic approaches to science teaching and learning (c.f. Halliday1978; van Leeuwen 2005, Airey & Linder 2017). What the papers in these sessions shared was the argument that such perspectives on science, and science teaching, can, at least in part, respond to calls to ‘democratize’ science education by recognising diverse sets of semiotic resources and, in so doing, seeking to address impediments to equal participation (Burke et al., 2017). 

    The 8ICOM science sessions were particularly noteworthy given the backdrop against which 8ICOM had been organised. In the months leading up to the conference, South Africa (and Cape Town, in particular) had experienced campus unrest aimed at ‘decolonizing’ higher education in that country. As part of this movement, the phrase #ScienceMustFall briefly trended on social media. This emanated from the claim that ‘science’ is a western, colonial construct that needs to be dismantled and replaced with the teaching of indigenous, African knowledge. Although the #ScienceMustFall slogan has since departed from the wider public consciousness, the questions it raises nonetheless remain: why, and how, should science be taught?  Is science more than just a western colonial construction and, if so, why? And, what can the concept of multimodality offer by way of answering these questions? 

    In this paper, we offer an overview of the multimodal science papers presented in the two sessions at 8ICOM in the light of these questions. This is done with a view to assessing where the multimodality community finds itself regarding science education, and how it might address questions of the legitimacy of western science in the future. It is thus an attempt, as the conference theme suggests, to ‘move the theory forward’.      

    References

    Airey, J. (2009). Science, Language and Literacy. Case Studies of Learning in Swedish University Physics. ActaUniversitatis  Upsaliensis. Uppsala Dissertations from the Faculty of Science and Technology 81. Uppsala, Sweden.:   http://www.diva-portal.org/smash/record.jsf?pid=diva2%3A173193&dswid=-4725.

    Airey, J. (2012). “I don’t teach language.” The linguistic attitudes of physics lecturers in Sweden.AILAReview, 25(2012), 64–79.

    Bernstein, B. (1999). Vertical and horizontal discourse: An essay. British Journal of Sociology Education, 20(2), 157-173.

    Lindstrøm, C. (2011) Analysing Knowledge and Teaching Practices in Physics. Presentation 21 November 2011. Department of   Physicsand Astronomy Uppsala University, Sweden.

    Martin, J. R. (2011). Bridgingtroubled waters: Interdisciplinarityand what makes it stick, in F. Christie and K. Maton, (eds.),   Disciplinarity. London: Continuum International Publishing, pp. 35-61.

    Volkwyn, T., Airey, J., Gregorčič, B., & Heijkenskjöld, F. (in press). Learning Science through Transduction: Multimodal disciplinary   meaning-making in the physics laboratory. Designs for Learning.

  • 105.
    Airey, John
    et al.
    Stockholm University, Faculty of Science, Department of Mathematics and Science Education. Uppsala University, Sweden.
    Simpson, Zachary
    Multimodal Science and Engineering Teaching: Perspectives from 8ICOM2018Conference paper (Other academic)
    Abstract [en]

    The previous international conference on multimodality – 8ICOM – featured two sessions devoted to multimodal, social semiotic approaches to science teaching and learning (c.f. Halliday1978; van Leeuwen 2005, Airey & Linder 2017). What the papers in these sessions shared was the argument that such perspectives on science, and science teaching, can, at least in part, respond to calls to ‘democratize’ science education by recognising diverse sets of semiotic resources and, in so doing, seeking to address impediments to equal participation (Burke et al., 2017). 

    The 8ICOM science sessions were particularly noteworthy given the backdrop against which 8ICOM had been organised. In the months leading up to the conference, South Africa (and Cape Town, in particular) had experienced campus unrest aimed at ‘decolonizing’ higher education in that country. As part of this movement, the phrase #ScienceMustFall briefly trended on social media. This emanated from the claim that ‘science’ is a western, colonial construct that needs to be dismantled and replaced with the teaching of indigenous, African knowledge. Although the #ScienceMustFall slogan has since departed from the wider public consciousness, the questions it raises nonetheless remain: why, and how, should science be taught?  Is science more than just a western colonial construction and, if so, why? And, what can the concept of multimodality offer by way of answering these questions? 

    In this paper, we offer an overview of the multimodal science papers presented in the two sessions at 8ICOM in the light of these questions. This is done with a view to assessing where the multimodality community finds itself regarding science education, and how it might address questions of the legitimacy of western science in the future. It is thus an attempt, as the conference theme suggests, to ‘move the theory forward’.      

  • 106.
    Airey, John
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Physics Didactics.
    Urban, Eriksson
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Physics Didactics. Högskolan i Kristianstad.
    What do you see here?: Using an analysis of the Hertzsprung-Russell diagram in astronomy to create a survey of disciplinary discernment.2014Conference paper (Refereed)
    Abstract [en]

    Becoming part of a discipline involves learning to interpret and use a range of disciplinary-specific semiotic resources (Airey, 2009). These resources have been developed and assigned particular specialist meanings over time. Nowhere is this truer than in the sciences, where it is the norm that disciplinary-specific representations have been introduced and then refined by a number of different actors in order to reconcile them with subsequent empirical and theoretical advances. As a consequence, many of the semiotic resources used in the sciences today still retain some (potentially confusing) traces of their historical roots. However, it has been repeatedly shown that university lecturers underestimate the challenges such disciplinary specific semiotic resources may present to undergraduates (Northedge, 2002; Tobias, 1986).

    In this paper we analyse one such disciplinary-specific semiotic resource from the field of Astronomy—the Hertzsprung-Russell diagram. First, we audit the potential of this semiotic resource to provide access to disciplinary knowledge—what Fredlund et al (2012) have termed its disciplinary affordances. Our analysis includes consideration of the use of scales, labels, symbols, sizes and colour. We show how, for historical reasons, the use of these aspects in the resource may differ from what might be expected by a newcomer to the discipline. Using the results of our analysis we then created an online questionnaire to probe what is discerned (Eriksson, Linder, Airey, & Redfors, in press) with respect to each of these aspects by astronomers and physicists ranging from first year undergraduates to university professors.

    Our findings suggest that some of the issues we highlight in our analysis may, in fact, be contributors to the alternative conceptions of undergraduate students and we therefore propose that lecturers pay particular attention to the disambiguation of these features for their students.

  • 107. Akabori, M.
    et al.
    Hidaka, S.
    Iwase, H.
    Yamada, S.
    Ekenberg, Ulf
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Realization of In0.75Ga0.25As two-dimensional electron gas bilayer system for spintronics devices based on Rashba spin-orbit interaction2012In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 112, no 11, p. 113711-Article in journal (Refereed)
    Abstract [en]

    Narrow gap InGaAs two-dimensional electron gas (2DEG) bilayer samples are fabricated and confirmed to have good electronic qualities as well as strong Rashba-type spin-orbit interactions (SOIs). The 2DEG systems are realized by molecular beam epitaxy in the form of wide quantum wells (QWs) with thicknesses tQW∼40-120nm modulation doped in both the upper and lower InAlAs barriers. From the Hall measurements, the overall mobility values of μe ∼15 m2/V s are found for the total sheet electron density of ns ∼8 × 1011/cm2, although the ns is distributed asymmetrically as about 1:3 in the upper and lower 2DEGs, respectively. Careful low temperature magneto-resistance analysis gives large SO coupling constants of α ∼20 × 10 -12eV m as well as expected electron effective masses of m*/m0 ∼0.033-0.042 for each bilayer 2DEG spin sub-band. Moreover, the enhancement of α with decrease of tQW is found. The corresponding self-consistent calculation, which suggests the interaction between the bilayer 2DEGs, is carried out and the origin of α enhancement is discussed.

  • 108.
    Akhmedov, Evgeny
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Neutrino oscillations: Theory and phenomenology2011In: Nuclear Physics B - Proceedings Supplements, ISSN 0920-5632, Vol. 221, p. 19-25Article in journal (Refereed)
    Abstract [en]

    A brief overview of selected topics in the theory and phenomenology of neutrino oscillations is given. These include: oscillations in vacuum and in matter; phenomenology of 3-flavour neutrino oscillations; CP and T violation in neutrino oscillations in vacuum and in matter; matter effects on ν μ↔ν τ oscillations; parametric resonance in neutrino oscillations inside the earth; oscillations below and above the MSW resonance; unsettled issues in the theory of neutrino oscillations.

  • 109.
    Akhtari, Mohammad Mehdi
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Accuracy of inverse treatment planning on computed tomography like images derived from magnetic resonance data2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Treatment planning for radiotherapy involves different types of imaging to delineate target volume precisely. The most suitable sources to get 3D information of the patient are the computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET)/CT modalities. CT is a modern medical imaging technique that allows three-dimensional treatment planning and conformal treatment techniques. By combining CT images with efficient dosimetry software, accurate patient positioning methods and verification and quality assurance good results can be achieved. The CT images show how the radiation interacts with the material based on each tissue has a different attenuation coefficient, so the data can be used for dose calculations in treatment planning.

    Radiation oncology is therapeutic modality, in which irradiating cancer cells as target is the main goal while always try to limit the dose to healthy tissues and organs. CT images have good potentials because they can provide high geometrical accuracy and electron density information. Having said that, however, using CT images alone for planning does not provide enough information in order to delineate the target volume accurately because the attenuation in soft tissue is fairly constant therefore the soft tissue contrast is poor. Here, (MR) imaging can be very useful since it has superior soft tissue contrast especially in conditions such as prostate cancer, brain lesions, and head and neck tumors. It should be noted that MR images cannot provide electron density information that is required for dose calculations.

    It has been hypothesized that since MRI images have certain benefits in comparison with CT images such as its superior soft tissue contrast which improves contrast resolution between different types of tissues, it would be beneficial to use MRI alone for both target delineation and treatment planning to save time and costs. This was investigated by introducing substitute computed tomography (SCT) which can be interpreted as CT equivalent information obtained by MRI images.

    We used data from five patients with intracranial tumors, and reviewed their initial dosimetric treatment plans that were based solely on CT images, that data was also used to evaluate the dosimetric accuracy of our research treatment plans. Optimization plans that are based on CT images and substitute CT (SCT) was compared with each other in the first step. On the second step the treatment plan that was based on SCT images was transferred to the CT images without any changes and comparisons between the dose calculations on both data sets were made. The delivered dose to planning target volume (PTV) and risk organs was compared.

    Gamma index results between SCT and transferred plan showed no difference in the dose distribution map in PTV. The maximum difference was in the outer contour to the skull. The average and median dose delivered to PTV was within 0.35% difference studying in all patients.

    In conclusion for patients with intracranial tumors the dosimetric accuracy of treatment plans based on SCT and MR images were very accurate, and we demonstrated that it was possible to reach the same dose volume histograms by SCT compared to CT with minimal differences, which were not significant. 

  • 110. Aksenova, N.A.
    et al.
    Isakina, A.P.
    Prokhvatilov, A.N.
    Strzhemechny, M.A.
    Soldatov, Alexander
    Sundqvist, Bertil
    Structural studies of C60 polymerized at high pressure1997In: Proceedings of the Symposium on Recent Advances in the Chemistry and Physics of Fullerenes and Related Materials: : [based on papers presented at the fourth symposium of the Fullerenes Group of the Electrochemical Society, held at the 192nd Meeting of the Electrochemical Society in Paris, France, from August 31 to September 5, 1997. This symposium, entitled Fullerenes: Chemistry, Physics and New Directions X ...] / [ed] Karl M. Kadish, Pennington, NJ: Electrochemical Society, Incorporated , 1997Conference paper (Refereed)
  • 111.
    Aksér, Marielle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Physics Didactics.
    Laborera i fysik, en självklarhet, men när?2014Independent thesis Advanced level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The theoretical background in this essay made clear that the students’ knowledge about physics improve, and they express a more positive attitude towards physics as a subject, when they have access to a more laboratory-based learning style. The aim of this study is to research how the placement of the lab relative to the lecture affects the students’ experiences and level of knowledge. The study involved students in year eight and was carried out during four weeks. A total of four lectures were held in addition to a total of eight labs devided on four lab-lessons. The students were divided into two different groups, one where the students were given lectures before they preformed the labs and one where the students had the labs prior to the corresponding lectures. Tests were given at the beginning and end of the study to evaluate any difference in knowledge and in addition to this the students answered surveys regarding their attitudes and experiences. The data belonging to each group was then compared. The result showed that the two groups improved their knowledge by nearly the same amount and any differences found regarding qualitative or quantitative knowledge between the two groups was minor. The one difference that could be found dealt with the students’ attitudes towards their education. The students in the group that had their lab-lesson before the corresponding lecture perceived the lecture as easier to understand than the other group. The perceived difficulty of the labs could not be connected to whether the students had the lab or the lecture first.

  • 112. Aktas, O.
    et al.
    Ren, H.
    Runge, A. F. J.
    Peacock, A. C.
    Hawkins, T.
    Ballato, J.
    Gibson, Ursula J.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Interfacing telecom fibers and silicon core fibers with nano-spikes for in-fiber silicon devices2018In: Optics InfoBase Conference Papers, Optics Info Base, Optical Society of America, 2018, article id u12d3i3mConference paper (Refereed)
    Abstract [en]

    We report fabrication of tapered silicon core fibers with nano-spikes enabling efficient optical coupling into the core, as well as their seamless integration with single mode fibers. A proof-of-concept integrated in-fiber silicon device is demonstrated. © OSA 2018.

  • 113.
    Al-attar, N.
    et al.
    Iraq.
    Al-Shammari, R. M.
    Ireland.
    Manzo, Michele
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Gallo, Katia
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Rodriguez, B. J.
    Ireland.
    Rice, J. H.
    Ireland.
    Wide-field surface-enhanced Raman scattering from ferroelectrically defined Au nanoparticle microarrays for optical sensing2018In: Optics InfoBase Conference Papers, OSA - The Optical Society , 2018Conference paper (Refereed)
    Abstract [en]

    The acquisition-time in optical sensors using SERS is vital value. Wide-field SERS is used to perform high-density of hot-spots of GNPs photodeposition on a periodically-protonexchanged- LiNbO3 which, leads to increase the sensitivity at ultralow probe concentrations.

  • 114.
    Albernaz, Daniel L.
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Do-Quang, Minh
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Hermanson, J. C.
    Amberg, Gustav
    KTH, School of Engineering Sciences (SCI), Mechanics, Physicochemical Fluid Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Thermodynamics of a real fluid near the critical point in numerical simulations of isotropic turbulence2016In: Physics of fluids, ISSN 1070-6631, E-ISSN 1089-7666, Vol. 28, no 12, article id 125105Article in journal (Refereed)
    Abstract [en]

    We investigate the behavior of a fluid near the critical point by using numerical simulations of weakly compressible three-dimensional isotropic turbulence. Much has been done for a turbulent flow with an ideal gas. The primary focus of this work is to analyze fluctuations of thermodynamic variables (pressure, density, and temperature) when a non-ideal Equation Of State (EOS) is considered. In order to do so, a hybrid lattice Boltzmann scheme is applied to solve the momentum and energy equations. Previously unreported phenomena are revealed as the temperature approaches the critical point. Fluctuations in pressure, density, and temperature increase, followed by changes in their respective probability density functions. Due to the non-linearity of the EOS, it is seen that variances of density and temperature and their respective covariance are equally important close to the critical point. Unlike the ideal EOS case, significant differences in the thermodynamic properties are also observed when the Reynolds number is increased. We also address issues related to the spectral behavior and scaling of density, pressure, temperature, and kinetic energy.

  • 115.
    Albrecht, Felix
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Numerical modeling and simulation of the deformation of wood under an applied indentation load2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 116.
    Albrecht, Felix
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Numerical modeling and simulation of the deformation of wood under an applied indentation load2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 117. Alcusa-Saez, E. P.
    et al.
    Diez, A.
    Rivera-Perez, E.
    Margulis, Walter
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Norin, Lars
    Andres, M. V.
    All-fiber acousto-optic tunable filter in polyimide coated optical fibers2017In: 2017 19th International Conference on Transparent Optical Networks (ICTON), IEEE Computer Society, 2017, article id 8025093Conference paper (Refereed)
    Abstract [en]

    We present the experimental demonstration of in-fiber acousto-optic coupling in a polyimide-coated optical fiber. Although the presence of the polyimide coating increases is significantly the attenuation of the acoustic wave, we show that acousto-optic interaction can still be produced with reasonable efficiency. The effect of the polyimide coating on the acousto-optic interaction process is analyzed in detailed. Theoretical and experimental results are in good agreement. To our knowledge, this is the first experimental demonstration of acousto-optic coupling in optical fibers with robust protective coating.

  • 118.
    Aldahan, Filip
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Svensson Grape, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Beräkning av kostnader för lågaktiv kärnavfallshantering2016Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The surtax in Sweden, which exclusively applies for nuclear power plants, in conjunction with low electricity prices, has forced Swedish nuclear power plants to minimize their expenses.

    At Oskarshamn power plant, estimation of cost, associated with low-level nuclear waste management has been conducted several years ago, but with lacking knowledge about how the calculations were performed. Therefore, the purpose of this project was to establish an independent cost estimation for compactible and non-compactible, low level and medium level nuclear waste. Cost estimates for free released low-level nuclear waste was also performed.

    By analyzing average economic figures from year 2014-2015 and visits on-site, an excel-based calculation template was accomplished. During the on-site studies, several visits to the low-level nuclear waste management facilities at Oskarshamn power plant were made, in order to get an overview of how the handling process works.

    By following the staff around, it was possible to estimate some of the time durations for the different parts in the handling process for compactible lowlevel nuclear waste, that were used in the calculations.

    The price for compactible low-level nuclear waste was calculated to 6,72 - 6,97 kr/kg, depending on the activity level. The non-compactible low-level nuclear waste price was found to vary between 4 – 48 kr/kg.

    The large fluctuations are due to different activity levels and associated additional costs in handling, measuring, final deposition etc.

    For both compactible and non-compactible nuclear waste, the storage cost is a factor that dominates the total cost and that could be minimized. Based on the analysis presented in this work, the cost can be decreased by reducing the storage time and/or store the nuclear waste in a more space efficient way.

    The cost estimate for free released material is low (5,94 – 8,74 kr/kg), which concludes that Oskarshamn power plant may profit from free releasing as much material as possible, due to the fact that it is highly profitable to recycle metals.

  • 119. Aldongarov, Anuar
    et al.
    Irgibaeva, Irina
    Hermansson, Kersti
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Theoretical study on passivation of small CdS clusters2014In: Molecular Physics, ISSN 0026-8976, E-ISSN 1362-3028, Vol. 112, no 5-6, p. 674-682Article in journal (Refereed)
    Abstract [en]

    We use density functional theory quantum chemical calculations to model optical properties of small cadmium sulphide clusters in order to explore the formation of trap states and the possibility to achieve surface passivation. The addition of capping oxygen ions on the surface of the CdS quantum dots is found to passivate the single-bonded Cd atoms. Added Cu ions resulted in the formation of deep trap states for certain locations of the copper impurity, while removal of single-bonded Cd atoms by adding S or SH groups leads to a band gap increase.

  • 120.
    Aldén, Liselotte
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences. Nätverket för vindbruk.
    Ridbäck, Ulrika
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences. Nätverket för vindbruk.
    Ny och pågående vindkraftsforskning i Sverige 2018: En sammanställning av svenska forskningsprogram och publikationer inom vindkraftsområdet2019Report (Other (popular science, discussion, etc.))
    Abstract [sv]

    Uppsala universitet Campus Gotland producerar årligen en sammanställning av svensk forskning om vindkraft i serien Ny och pågående forskning om vindkraft i Sverige. Syftet med dessa publikationer är att intresserade ska få en lättillgänglig överblick av vad som skett under året inom vindkraftsforskningen i landet. Sammanställningen är indelad i två avsnitt. Det första är en presentation av de forskningsprogram och forskningscentra som är verksamma inom vindkraftsforskning i Sverige med fokus på deras pågående projekt. Därefter följer en ämnesindelad förteckning över publicerad forskning om vindkraft under aktuellt år vid svenska universitet, högskolor och institutioner. Där ingår vetenskapliga artiklar och rapporter, doktors- och licentiatavhandlingar samt uppsatser på kandidat-, magister- och mastersnivå samt sammanfattningar med statistik och jämförelser med tidigare år.

  • 121. Aleksandrovski, A. N.
    et al.
    Kir'yanova, E. A.
    Manzheli, V. G.
    Soldatov, Alexander
    Tolkachev, A. M.
    Anomalies of the plastic deformation of solid parahydrogen1987In: Soviet Journal of Low Temperature Physics, ISSN 0360-0335, Vol. 13, no 10, p. 623-624Article in journal (Refereed)
    Abstract [en]

    The work hardening curves σ(ε) of special-purity parahydrogen single crystals are obtained in the temperature range 2-6 °K at very low stresses (σ=5 10 - 2 g/mm2). Our study reveals a number of anomalies, in particular an effect whereby a sample recovers its dimensions after plastic deformation reaching 7%. The work hardening curves of solid neon are also obtained for comparison. The gravity-induced downward flow of parahydrogen single crystals at helium temperatures mentioned in the literature has not been observed.

  • 122. Aleksandrovskii,, A. N.
    et al.
    Esel'son, V. B.
    Manzhelii, V. G.
    Udovidchenko, B. G.
    Soldatov, Alexander
    Sundqvist, B.
    Negative thermal expansion of fullerite C60 at liquid helium temperatures1997In: Low temperature physics (Woodbury, N.Y., Print), ISSN 1063-777X, E-ISSN 1090-6517, Vol. 23, no 11, p. 943-946Article in journal (Refereed)
    Abstract [en]

    The thermal expansion of fullerite C60 has been measured in the temperature range 2-9 K. A compacted fullerite sample with a diameter of about 6 mm and height of 2.4 mm was used. It was found that at temperatures below ~ 3.4 K the linear thermal expansion coefficient becomes negative. At temperatures above 5 K our results are in good agreement with the available literature data. A qualitative explanation of the results is proposed.

  • 123. Aleksandrovskii, A. N.
    et al.
    Palei, V. V.
    Soldatov, Alexander
    Parbuzin, V. S.
    Thermal expansion of solid deuterohydrogen at helium temperatures1990In: Soviet Journal of Low Temperature Physics, ISSN 0360-0335, Vol. 16, no 11, p. 784-785Article in journal (Refereed)
    Abstract [en]

    For the first time, the thermal expansion of solid deuterohydrogen (HD) is studied in the temperature range 1.2 to 5 K. The isotopic impurity concentrations are 1.5% H2 and 0.4% D2, the other impurities totalling less than 5 · 10 - 4%. It is shown that the thermal expansion coefficient of solid HD can be described by the expression [proportional]HD(K - 1)=1.38 · 10 - 7 T3 in the investigated temperature range. The isothermal compressibility ξT=(34 ± 6) · 10 - 10 Pa - 1 is predicted on the basis of the experimental results and literature data.

  • 124. Aleksandrovskii, A. N.
    et al.
    Soldatov, Alexander
    Manzhelii, V. G.
    Palei, V.V:
    Thermal expansion of solid parahydrogen at helium temperatures1989In: Soviet Journal of Low Temperature Physics, ISSN 0360-0335, Vol. 15, no 8, p. 492-493Article in journal (Refereed)
    Abstract [en]

    Thermal expansion of solid parahydrogen is investigated in the temperature range from 0.9 to 5 K. The content of the orthomodification in parahydrogen is 0.13 at. %, and that of nonhydrogen impurities is less than 2 10 - 3 at. %. No anisotropy in thermal expansion was observed within the experimental error. The temperature dependence of the linear expansion coefficient can be described by the expression α=1.82 10 - 7 T3. The obtained values of α are in good agreement with the available data on compressibility and ([partial derivate]p/[partial derivate]T)V. The Grüneisen coefficient is γ=3αV/CV`T=2.00 ± 0.25.

  • 125.
    Alekseeva, L.A.
    et al.
    B. I. Verkin Institute of Low-temperature Physics and Engineering, National Academy of Sciences of Ukraine.
    Dobryden, Illia
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Unusual changes in the shape of solid parahydrogen with higher than natural isotope content2016In: Low temperature physics (Woodbury, N.Y., Print), ISSN 1063-777X, E-ISSN 1090-6517, Vol. 42, no 6, p. 484-490Article in journal (Refereed)
    Abstract [en]

    The relative elongation epsilon of samples of high purity (99.9999 mol. % with respect to nonhydrogenic impurities) parahydrogen (p-H-2, similar to 0.2% o-H-2) with different amounts of the stable hydrogen isotope deuterium is measured as a function of applied stress sigma at temperatures of 1.8-4.2 K. The samples were subjected to uniaxial tension by stepwise loading. The ratio [D]/[H] of the number [D] of deuterium atoms to the number [H] of p-H-2 hydrogen atoms ranged from 0.0055 +/- 0.0005 at. % up to 0.07 at. %. For deuterium enriched p-H-2, the easy slip dislocation stage vanished from the sigma(epsilon) curves and there was a significant reduction in the total relative elongation of the samples, as well as a substantial increase in the hardening coefficient d sigma/d epsilon. Deformation of samples of p-H-2 with deuterium contents higher than the natural amount produces an unusual change in their shape owing to the appearance of a rotational component of the low-temperature plastic mass transfer

  • 126. Alexandrovskii, A. N.
    et al.
    Esel’son, V. B.
    Manzhelii, V. G.
    Soldatov, Alexander
    Sundqvist, B.
    Udovidchenko, B. G.
    Thermal expansion of single-crystal fullerite C60 at helium temperatures2000In: Low temperature physics (Woodbury, N.Y., Print), ISSN 1063-777X, E-ISSN 1090-6517, Vol. 26, no 1, p. 75-80Article in journal (Refereed)
    Abstract [en]

    The thermal expansion of single-crystal fullerite C60 has been studied in the range of liquid-helium temperatures (2-10 K). At temperatures below ~4.5 K the thermal expansion of fullerite C60 becomes negative, in agreement with the previous results on polycrystalline materials. A qualitative explanation of the results is proposed

  • 127.
    Algers, Björn
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Stereo Camera Calibration Accuracy in Real-time Car Angles Estimation for Vision Driver Assistance and Autonomous Driving2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The automotive safety company Veoneer are producers of high end driver visual assistance systems, but the knowledge about the absolute accuracy of their dynamic calibration algorithms that estimate the vehicle’s orientation is limited.

    In this thesis, a novel measurement system is proposed to be used in gathering reference data of a vehicle’s orientation as it is in motion, more specifically the pitch and roll angle of the vehicle. Focus has been to estimate how the uncertainty of the measurement system is affected by errors introduced during its construction, and to evaluate its potential in being a viable tool in gathering reference data for algorithm performance evaluation.

    The system consisted of three laser distance sensors mounted on the body of the vehicle, and a range of data acquisition sequences with different perturbations were performed by driving along a stretch of road in Linköping with weights loaded in the vehicle. The reference data were compared to camera system data where the bias of the calculated angles were estimated, along with the dynamic behaviour of the camera system algorithms. The experimental results showed that the accuracy of the system exceeded 0.1 degrees for both pitch and roll, but no conclusions about the bias of the algorithms could be drawn as there were systematic errors present in the measurements.

  • 128.
    Alhassan, Erwin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Nuclear data uncertainty propagation for a lead-cooled fast reactor: Combining TMC with criticality benchmarks for improved accuracy2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    For the successful deployment of advanced nuclear systems and for optimization of current reactor designs, high quality and accurate nuclear data are required. Before nuclear data can be used in applications, they are first evaluated, benchmarked against integral experiments and then converted into formats usable for applications. The evaluation process in the past was usually done by using differential experimental data which was then complimented with nuclear model calculations. This trend is fast changing because of increase in computational power and tremendous improvements in nuclear reaction theories over the last decade. Since these model codes are not perfect, they are usually validated against a large set of experimental data. However, since these experiments are themselves not exact, the calculated quantities of model codes such as cross sections, angular distributions etc., contain uncertainties. A major source of uncertainty being the input parameters to these model codes. Since nuclear data are used in reactor transport codes asinput for simulations, the output of transport codes ultimately contain uncertainties due to these data. Quantifying these uncertainties is therefore important for reactor safety assessment and also for deciding where additional efforts could be taken to reduce further, these uncertainties.

    Until recently, these uncertainties were mostly propagated using the generalized perturbation theory. With the increase in computational power however, more exact methods based on Monte Carlo are now possible. In the Nuclear Research and Consultancy Group (NRG), Petten, the Netherlands, a new method called ’Total Monte carlo (TMC)’ has been developed for nuclear data evaluation and uncertainty propagation. An advantage of this approach is that, it eliminates the use of covariances and the assumption of linearity that is used in the perturbation approach.

    In this work, we have applied the TMC methodology for assessing the impact of nuclear data uncertainties on reactor macroscopic parameters of the European Lead Cooled Training Reactor (ELECTRA). ELECTRA has been proposed within the GEN-IV initiative within Sweden. As part of the work, the uncertainties of plutonium isotopes and americium within the fuel, uncertainties of the lead isotopes within the coolant and some structural materials of importance have been investigated at the beginning of life. For the actinides, large uncertainties were observed in the k-eff due to Pu-238, 239, 240 nuclear data while for the lead coolant, the uncertainty in the k-eff for all the lead isotopes except for Pb-204 were large with significant contribution coming from Pb-208. The dominant contributions to the uncertainty in the k-eff came from uncertainties in the resonance parameters for Pb-208.

    Also, before the final product of an evaluation is released, evaluated data are tested against a large set of integral benchmark experiments. Since these benchmarks differ in geometry, type, material composition and neutron spectrum, their selection for specific applications is normally tedious and not straight forward. As a further objective in this thesis, methodologies for benchmark selection based the TMC method have been developed. This method has also been applied for nuclear data uncertainty reduction using integral benchmarks. From the results obtained, it was observed that by including criticality benchmark experiment information using a binary accept/reject method, a 40% and 20% reduction in nuclear data uncertainty in the k-eff was achieved for Pu-239 and Pu-240 respectively for ELECTRA.

  • 129.
    Alhassan, Erwin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Sjöstrand, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Duan, Junfeng
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Gustavsson, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Koning, Arjan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Pomp, Stephan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Rochman, Dimitri
    Nuclear Research and Consultancy Group.
    Österlund, Michael
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Combining Total Monte Carlo and Benchmarks for Nuclear Data Uncertainty Propagation on a Lead Fast Reactor's Safety Parameters2014In: Nuclear Data Sheets, ISSN 0090-3752, E-ISSN 1095-9904, Vol. 118, p. 542-544Article in journal (Refereed)
    Abstract [en]

    Analyses are carried out to assess the impact of nuclear data uncertainties on some reactor safety parameters for the European Lead Cooled Training Reactor (ELECTRA) using the Total Monte Carlo method. A large number of Pu-239 random ENDF-format libraries, generated using the TALYS based system were processed into ACE format with NJOY99.336 code and used as input into the Serpent Monte Carlo code to obtain distribution in reactor safety parameters. The distribution in keff obtained was compared with the latest major nuclear data libraries – JEFF-3.1.2, ENDF/B-VII.1 and JENDL-4.0. A method is proposed for the selection of benchmarks for specific applications using the Total Monte Carlo approach based on a correlation observed between the keff of a given system and the benchmark. Finally, an accept/reject criteria was investigated based on chi squared values obtained using the Pu-239 Jezebel criticality benchmark. It was observed that nuclear data uncertainties were reduced considerably from 748 to 443 pcm.

  • 130.
    Alhassan, Erwin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Sjöstrand, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Duan, Junfeng
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Gustavsson, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Pomp, Stephan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Österlund, Michael
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Rochman, Dimitri
    Nuclear Research and Consultancy Group.
    Koning, Arjan J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Uncertainty analysis of Lead cross sections on reactor safety for ELECTRA2016In: SNA + MC 2013 - Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo, 2016, article id 02401Conference paper (Refereed)
    Abstract [en]

    The Total Monte Carlo (TMC) method was used in this study to assess the impact of Pb-206, 207 and 208 nucleardata uncertainties on k-eff , beta-eff, coolant temperature coefficient, the coolant void worth for the ELECTRA reactor. Relatively large uncertainties were observed in the k-eff and the coolant void worth for all the isotopes with significant contribution coming from Pb-208 nuclear data. The large Pb-208 nuclear data uncertainty observed was further investigated by studying the impact of partial channels on the k-eff and beta-eff. Various sections of ENDF file: elasticscattering (n,el), inelastic scattering (n,inl), neutron capture (n,gamma), (n,2n), resonance parameters and the angular distribution were varied randomly and distributions in k-eff and beta-eff obtained. The dominant contributions to the uncertainty in the k-eff from Pb-208 came from uncertainties in the resonance parameters; however, elastic scattering cross section and the angular distribution also had significant impact. The impact of nuclear data uncertainties on the beta-eff was observed to be small.

  • 131.
    Alhassan, Erwin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Sjöstrand, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Helgesson, Petter
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Österlund, Michael
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Pomp, Stephan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Koning, Arjan J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics. Nuclear Research and Consultancy Group, Petten, The Netherlands.
    Rochman, D.
    Laboratory for Reactor Physics Systems Behaviour, Paul Scherrer Institut, Villigen, Switzerland.
    Benchmark selection methodology for reactor calculations and nuclear data uncertainty reduction2015In: Annals of Nuclear Energy, ISSN 0306-4549, E-ISSN 1873-2100Article in journal (Refereed)
    Abstract [en]

    Criticality, reactor physics and shielding benchmarks are expected to play important roles in GEN-IV design, safety analysis and in the validation of analytical tools used to design these reactors. For existing reactor technology, benchmarks are used for validating computer codes and for testing nuclear data libraries. Given the large number of benchmarks available, selecting these benchmarks for specic applications can be rather tedious and difficult. Until recently, the selection process has been based usually on expert judgement which is dependent on the expertise and the experience of the user and there by introducing a user bias into the process. This approach is also not suitable for the Total Monte Carlo methodology which lays strong emphasis on automation, reproducibility and quality assurance. In this paper a method for selecting these benchmarks for reactor calculation and for nuclear data uncertainty reduction based on the Total Monte Carlo (TMC) method is presented. For reactor code validation purposes, similarities between a real reactor application and one or several benchmarks are quantied using a similarity index while the Pearson correlation coecient is used to select benchmarks for nuclear data uncertainty reduction. Also, a correlation based sensitivity method is used to identify the sensitivity of benchmarks to particular nuclear reactions. Based on the benchmark selection methodology, two approaches are presented for reducing nuclear data uncertainty using integral benchmark experiments as an additional constraint in the TMC method: a binary accept/reject and a method of assigning file weights using the likelihood function. Finally, the methods are applied to a full lead-cooled fast reactor core and a set of criticality benchmarks. Signicant reductions in Pu-239 and Pb-208 nuclear data uncertainties were obtained after implementing the two methods with some benchmarks.

  • 132.
    Alho, Artur
    et al.
    University of Lisbon, Portugal.
    Hell, Juliette
    Free University Berlin, Germany.
    Uggla, Claes
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Global dynamics and asymptotics for monomial scalar field potentials and perfect fluids2015In: Classical and quantum gravity, ISSN 0264-9381, E-ISSN 1361-6382, Vol. 32, no 14, article id 145005Article in journal (Refereed)
    Abstract [en]

    We consider a minimally coupled scalar field with a monomial potential and a perfect fluid in flat Friedmann-Lemaitre-Robertson-Walker cosmology. We apply local and global dynamical systems techniques to a new three-dimensional dynamical systems reformulation of the field equations on a compact state space. This leads to a visual global description of the solution space and asymptotic behavior. At late times we employ averaging techniques to prove statements about how the relationship between the equation of state of the fluid and the monomial exponent of the scalar field affects asymptotic source dominance and asymptotic manifest self-similarity breaking. We also situate the ’attractor’ solution in the three-dimensional state space and show that it corresponds to the one-dimensional unstable center manifold of a de Sitter fixed point, located on an unphysical boundary associated with the dynamics at early times. By deriving a center manifold expansion we obtain approximate expressions for the attractor solution. We subsequently improve the accuracy and range of the approximation by means of Pade approximants and compare with the slow-roll approximation. 

  • 133.
    Ali, Babar
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Study of the performance of the Level-1 track trigger in the H→ττ→ee channel in ATLAS at high luminosity LHC2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 134.
    Allali, Naoual
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Covalent functionalization of carbon nanomaterials for bioelectrochemical applications2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Carbon nanotubes (CTNs) are renowned for their exceptional electronic and mechanical properties. Their structure can be considered as rolling up a graphene sheet along a specific crystallographic direction, leading to a 1D confinement of the electronic wavefunction of the delocalized electrons along the perimeter of the cylindrical structure thus obtained. This confinement produces the existence of defined spikes of high intensity in the electronic density of states, called van Hove singularities. These singularities are primordial to understand both the optical and electronic properties of CNTs through electronphonon coupling processes. If the electronic density of states (DoS) is non zero at the Fermi level the nanotube is metallic, otherwise the nanotube is semiconducting. The synthesis of CNTs always produces a mixture of both metallic and semiconducting nanotubes, and this material can be useful to be incorporated at the surface of electrodes for electrochemical devices. The high specific surface area, the high mechanical and thermal stability of CNTs and the low percolation threshold for electron transport in a mat of CNTs render them very attractive for such kind of applications. There is yet a drawback of using raw CNTs: they are not compatible with solvents and modification of their surfaces by chemistry is required to make good suspensions for easy deposition at the electrode surface and to introduce specific functional groups for promoting electron transfer, called electron shuttles.

    The final aim of this thesis is therefore the covalent functionalization of CNTs by electron shuttles and their incorporation at the surface of glassy carbon electrodes for electrochemical devices application. A strategy of chemical grafting in three steps has been chosen: i) a controlled oxidation step in acidic media assisted by microwave irradiation in order to keep the structural integrity of CNTs, so as to save their useful electronic properties; ii) a chloration step to produce acid chloride groups and iii) reaction of these groups with electron shuttles modified by specific linkers. The study was first conducted on very clean HiPCO single-walled CNTs (SWCNTs). This enabled to avoid any disturbing effects of carbonaceous impurities or residual catalytic particles, since their possible effects are extremely controversial in the literature. Once validated, this approach was then conducted with cheaper material including few-walls carbon nanotubes (FWCNTs). The use of FWCNTs compared to SWCNTs was not only beneficial for the production of costeffective electrochemical devices but also for a better durability ofthe final device, the inner nanotubes being not functionalized.

    The challenge was to obtain a functionalization process with enough grafted electron shuttles to obtain a good electrocatalytic activity but maintaining CNTs integrity. The first step is predominant to reach this goal, and requires a very accurate understanding of the nature and the number of defects created in the CNTs structure versus the physico-chemical conditions used. The introduction of defects in the crystallographic structure of CNTs has strong consequences both for the electronic DoS and for the phononic properties of the material. Spectroscopic methods are essential in probing these consequences. UV-visible-near IR absorption spectroscopy is the method of choice to directly probe the existence of van Hove singularities and the oscillator strength associated with the authorized electronic transitions between theses ingularities. Covalent grafting of chemical groups at the surface of CNTs changes both the energy and the intensity of these transitions. However, this spectroscopic method requires solubilizing CNTs in non-absorbing solvents using adequate surfactants. Interactions between surfactant molecules and CNT sidewalls may also alter the position and intensity of electronic transitions between van Hove singularities unrelated to the chemical groups covalently grafted.

    Raman spectroscopy of CNTs involves the electronphonon coupling processes through the resonant electronic enhancement of Raman modes. Double resonance processes are also observed in Raman spectrum of CNTs, for instance with the D-band mode that is actually related to the existence of defects in the graphene structure of CNTs. Therefore, Raman spectroscopy is a widespread analytical method to characterize the structural defects created by covalent functionalization processes. Indeed, the intensity ratio of the D and G bands in the Raman spectrum is correlated to the number of defects. However, CNTs are used as bundles when chemical functionalization is performed, which produces a heterogeneous distribution of chemical species grafted on CNTs. Therefore, we have developed a new protocol to obtain statistically significant data for most of the samples made in this thesis. Nevertheless, this statistical approach is still limited for samples slightly functionalized, whence the idea to use spectroscopic ellipsometry as an alternative method to characterize these samples.

    More specifically, ellipsometric data were collected from UV to the IR part of the electromagnetic spectrum for CNTs functionalized in different conditions. The complex dielectric function was retrieved from the experimental data. A Drude model was used to model the infrared part of the data for raw and acid oxidized CNTs. The optical conductivity of the samples was obtained. These results, combined with other information collected using a set of complementary analytical techniques (Raman scattering, UV-visible-NIR absorption, X-ray photoelectron spectroscopy, thermogravimetric analysis coupled to mass spectrometry, transmission electron microscopy and rare gas volumetric adsorption), show that the microwave-assisted oxidation process actually consists in removing amorphous carbon deposits away from the surface of CNTs and transforming the already existing defects in the CNT structure to oxygen-containing groups such as carboxylic acids.

    Rare gas volumetric adsorption was also used to compare the distribution of chemical groups at the surface of CNT bundles when two different acids are used (HNO3 and H2SO4). The chloration step was also studied by these methods, as well as the final grafting of electron shuttles. Finally, these functionalized CNTs were deposited at the surface of glassy carbon electrodes and used as electron mediators for diaphorase-catalysed oxidation of nicotinamide adenine dinucleotide (NADH). This was a good example of mediated electron transfer for development of electrochemical devices based on NADH recycling and it validated the good electrocatalytic properties of functionalized CNTs for making electrochemical sensors and actuators, opening new perspectives with potential market applications.

  • 135.
    Allali, Naoual
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. LCPME, UMR CNRS-Université de Lorraine, Villers-lès-Nancy, France. SRSMC, UMR CNRS-Université de Lorraine, Faculté des Sciences et Technologies, Vandoeuvre-lès-Nancy, France.
    Urbanova, Veronika
    LCPME, UMR CNRS-Université de Lorraine, Villers-lès-Nancy, France.
    Etienne, Mathieu
    LCPME, UMR CNRS-Université de Lorraine, Villers-lès-Nancy, France.
    Devaux, Xavier
    IJL, UMR CNRS-Université de Lorraine, Nancy Cedex, France.
    Mallet, Martine
    LCPME, UMR CNRS-Université de Lorraine, Villers-lès-Nancy, France.
    Vigolo, Brigitte
    IJL, UMR CNRS-Université de Lorraine, Faculté des Sciences et Technologies, Vandoeuvre-lès-Nancy Cedex, France.
    Adjizian, Jean-Joseph
    IMN, UMR CNRS-Université de Nantes, Nantes, France.
    Ewels, Chris
    IMN, UMR CNRS-Université de Nantes, Nantes, France.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Soldatov, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    McRae, Edward
    IJL, UMR CNRS-Université de Lorraine, Faculté des Sciences et Technologies,Vandoeuvre-lès-Nancy Cedex, France.
    Fort, Yves
    SRSMC, UMR CNRS-Université de Lorraine, Faculté des Sciences et Technologies, Vandoeuvre-lès-Nancy, France.
    Dossot, Manuel
    LCPME, UMR CNRS-Université de Lorraine, Villers-lès-Nancy, France.
    Mamane, Victor
    Institut de Chimie de Strasbourg, UMR CNRS-Université de Strasbourg, Strasbourg, France.
    Accurate control of the covalent functionalization of single-walled carbon nanotubes for the electro-enzymatically controlled oxidation of biomolecules2018In: Beilstein Journal of Nanotechnology, ISSN 2190-4286, Vol. 9, p. 2750-2762Article in journal (Refereed)
    Abstract [en]

    Single-walled carbon nanotubes (SWCNTs) were functionalized by ferrocene through ethyleneglycol chains of different lengths (FcETGn) and the functionalized SWCNTs (f-SWCNTs) were characterized by different complementary analytical techniques. In particular, high-resolution scanning electron transmission microscopy (HRSTEM) and electron energy loss spectroscopy (EELS) analyses support that the outer tubes of the carbon-nanotube bundles were covalently grafted with FcETGn groups. This result confirms that the electrocatalytic effect observed during the oxidation of the reduced form of nicotinamide adenine dinucleotide (NADH) co-factor by the f-SWCNTs is due to the presence of grafted ferrocene derivatives playing the role of a mediator. This work clearly proves that residual impurities present in our SWCNT sample (below 5 wt. %) play no role in the electrocatalytic oxidation of NADH. Moreover, molecular dynamic simulations confirm the essential role of the PEG linker in the efficiency of the bioelectrochemical device in water, due to the favorable interaction between the ETG units and water molecules that prevents π-stacking of the ferrocene unit on the surface of the CNTs. This system can be applied to biosensing, as exemplified for glucose detection. The well-controlled and well-characterized functionalization of essentially clean SWCNTs enabled us to establish the maximum level of impurity content, below which the f-SWCNT intrinsic electrochemical activity is not jeopardized.

  • 136.
    Allali, Naoual
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Urbanova, Veronika
    Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564, CNRS–University of Lorraine.
    Etienne, Mathieu
    Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564, CNRS–University of Lorraine.
    Mallet, Martine
    Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564, CNRS–University of Lorraine.
    Devaux, Xavier
    Département P2M, Institut Jean Lamour, UMR 7198 CNRS-Université de Lorraine.
    Vigolo, Brigitte
    Département CP2S, Institut Jean Lamour UMR 7198 CNRS-Université de Lorraine.
    Fort, Yves
    Laboratoire de Structure et Réactivité des Systèmes Moléculaires Complexes, UMR 7565 CNRS–Université de Lorraine, 54506 Vandoeuvre-les-Nancy.
    Walcarius, Alain
    Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564, CNRS–University of Lorraine.
    Noël, Maxime
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    McRae, Edward
    Département CP2S, Institut Jean Lamour UMR 7198 CNRS-Université de Lorraine.
    Soldatov, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Dossot, Manuel
    Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564, CNRS–University of Lorraine.
    Mamane, Victor
    Laboratoire de Structure et Réactivité des Systèmes Moléculaires Complexes, UMR 7565 CNRS–Université de Lorraine, 54506 Vandoeuvre-les-Nancy.
    Electrocatalytic effect towards NADH induced by HiPco single-walled carbon nanotubes covalently functionalized by ferrocene derivatives2013In: 2012 MRS Fall Meeting: Symposium YY – Low-Voltage Electron Microscopy and Spectroscopy for Materials Characterization, Cambridge University Press, 2013Conference paper (Refereed)
    Abstract [en]

    The present work reports the covalent functionalization of single-walled carbon nanotubes (SWCNTs) by ferrocene derivatives with polyethyleneglycol linkers. A very clean initial sample was chosen to avoid any residual catalyst and carbon impurities. Functionalized SWCNTs (f-CNTs) are deposited on the surface of a glassy carbon electrode (GCE) and this modified electrode is used for oxidizing the cofactor NADH (dihydronicotinamide adenine dinucleotide) in the presence of diaphorase. A clear electrocatalytic effect is evidenced, which can only be attributed to the f-CNTs.

  • 137.
    Allali, Naoual
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Urbanova, Veronika
    Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564, CNRS–University of Lorraine.
    Mamane, Victor
    Laboratoire de Structure et Réactivité des Systèmes Moléculaires Complexes, UMR 7565 CNRS–Université de Lorraine, 54506 Vandoeuvre-les-Nancy.
    Etienne, Mathieu
    Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564, CNRS–University of Lorraine.
    Mallet, Martine
    Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564, CNRS–University of Lorraine.
    Devaux, Xavier
    Institut Jean Lamour, Department P2M, UMR 7198 CNRS–Université de Lorraine, Ecole des Mines, 54042 Nancy.
    Vigolo, Brigitte
    Institut Jean Lamour, Department CP2S, UMR 7198 CNRS–Université de Lorraine, 54506 Vandoeuvre-les-Nancy.
    Fort, Yves
    Laboratoire de Structure et Réactivité des Systèmes Moléculaires Complexes, UMR 7565 CNRS–Université de Lorraine, 54506 Vandoeuvre-les-Nancy.
    Walcarius, Alain
    Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564, CNRS–University of Lorraine.
    Noël, Maxime
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Soldatov, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    McRae, Edward
    Institut Jean Lamour, Department CP2S, UMR 7198 CNRS–Université de Lorraine, 54506 Vandoeuvre-les-Nancy.
    Dossot, Manuel
    Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564, CNRS–University of Lorraine.
    Covalent functionalization of few-wall carbon nanotubes by ferrocene derivatives for bioelectrochemical devices2012In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 249, no 12, p. 2349-2352Article in journal (Refereed)
    Abstract [en]

    The present work reports the covalent functionalization of few-wall CNTs (FWCNTs) by ferrocene derivatives to (i) improve their dispersion efficiency in water and (ii) graft electroactive chemical groups on their side-walls in order to promote electron transfer to biomolecules. The functionalized CNTs (f-CNTs) are used to modify a glassy carbon electrode and this modified electrode is used for oxidizing the cofactor NADH (dihydronicotinamide adenine dinucleotide).

  • 138.
    Allali, Naoual
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Urbanova, Veronika
    Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564, CNRS–University of Lorraine.
    Mamane, Victor
    Laboratoire de Structure et Réactivité des Systèmes Moléculaires Complexes, UMR 7565 CNRS–Université de Lorraine, 54506 Vandoeuvre-les-Nancy.
    Waldbock, Jeremy
    Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564, CNRS–University of Lorraine.
    Etienne, Mathieu
    Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564, CNRS–University of Lorraine.
    Mallet, Martine
    Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564, CNRS–University of Lorraine.
    Devaux, Xavier
    Département P2M, Institut Jean Lamour, UMR 7198 CNRS-Université de Lorraine.
    Vigolo, Brigitte
    Département CP2S, Institut Jean Lamour UMR 7198 CNRS-Université de Lorraine.
    Fort, Yves
    Laboratoire de Structure et Réactivité des Systèmes Moléculaires Complexes, UMR 7565 CNRS–Université de Lorraine, 54506 Vandoeuvre-les-Nancy.
    Walcarius, Alain
    Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564, CNRS–University of Lorraine.
    Noël, Maxime
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Soldatov, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    McRae, Edward
    Département CP2S, Institut Jean Lamour UMR 7198 CNRS-Université de Lorraine.
    Dossot, Manuel
    Département CP2S, Institut Jean Lamour UMR 7198 CNRS-Université de Lorraine.
    Few-wall carbon nanotubes covalently functionalized by ferrocene groups for bioelectrochemical devices2012In: MRS Online Proceedings Library, Cambridge University Press, 2012Conference paper (Refereed)
    Abstract [en]

    The present work reports the covalent functionalization of few-wall CNTs (FWCNTs) by ferrocene derivatives to i) improve their dispersion efficiency in water and ii) to graft electroactive chemical groups on their side-walls in order to promote electron transfer to biomolecules. The functionalized CNTs (f-CNTs) are used to modify a glassy carbon electrode and this modified electrode is used for oxidizing the cofactor NADH (dihydronicotinamide adenine dinucleotide).

  • 139.
    Almhagen, Erik
    Stockholm University, Faculty of Science, Department of Physics.
    Development and validation of a scanned proton beam model for dose distribution verification using Monte Carlo2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 140.
    Almhagen, Erik
    Stockholm University, Faculty of Science, Department of Physics.
    Development and validation of a scanned proton beam model for dose distribution verification using Monte Carlo2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Background and purpose: Although proton therapy is becoming increasingly common as a radiotherapy modality, facilities offering proton therapy are still scarce in comparison to photon therapy. Sweden's new proton therapy facility, Skandionkliniken, is scheduled to being operation during August 2015, employing the pencil beam scanning technique. Given Skandionklinikens unique stance as the only facility offering proton therapy in Sweden as of this writing, it is important to minimize the need for measurements during quality assurance to free up beam time for patients and other endeavors. It is the purpose of this work to create a foundation for a method whereby dose distribution verification is done via Monte Carlo simulation by developing and performing simple validation of a beam model. As input for simulating a dose distribution, log files storing a wide variety of data on how the dose distribution was delivered were used.

    Method: GATE, an open source Monte Carlo code and built on top of Geant4, was used for all simulations. A beam model parameterizing phase space at the nozzle exit was developed. The beam model development process made use of the beam data library and log file data. Using an in house developed code to convert log file data to treatment plans readable by GATE allowed simulation of delivered dose distributions. For validation, gamma index tests were performed comparing measured and simulated dose distributions.

    Results: The beam model was found able to predict the spot size in almost all cases within 0.2 mm. Likewise, the beam model was able to predict the proton range within 0.2 mm. The energy spread was found to be more difficult to estimate; comparisons of simulated and measured curves for at six points around the Bragg peak yielded a maximum deviation of 0.86 mm. Several difficulties prevented easy interpretation of the results of the gamma index tests. If allowance is made for certain data manipulation, pass rates of 90% or above using the global method can be achieved for all depths and for both treatment plans scanned.

    Conclusion: Although some complications arose during validation, the beam model performance appears capable of producing accurate results. To produce a full product suitable for routine patient specific quality assurance, further work will be necessary. Significant computing power would also be mandatory for routine use, necessitating the acquisition of a dedicated computer cluster or using GPUs.

  • 141.
    Almlöf, Jonas
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics (Closed 20120101), Quantum Electronics and Quantum Optics, QEO (moved to SCI 2011-07-01).
    Björk, Gunnar
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics (Closed 20120101), Quantum Electronics and Quantum Optics, QEO (moved to SCI 2011-07-01).
    A short and efficient quantum-erasure code for polarization-coded photonic qubits2009In: CLEO/Europe - EQEC 2009 - European Conference on Lasers and Electro-Optics and the European Quantum Electronics Conference, 2009, p. 5191786-Conference paper (Refereed)
  • 142.
    Almqvist, Nils
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Fractal analysis of scanning probe microscopy images1996In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 355, no 1-3, p. 221-228Article in journal (Refereed)
    Abstract [en]

    The accuracy and precision of several algorithms, including newly developed, for calculating the fractal dimension from scanning probe microscopy images of material surfaces are investigated. The algorithms are based on the area-perimeter method, a variance method or versions of the structure function method. The latter two methods show good correspondence to computer simulated images, with known fractal dimensions, and have successfully been applied also on real images. The results show that these two methods give reliable fractal dimensions and are well suited to describe surface roughness quantitatively.

  • 143.
    Almqvist, Nils
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Scanning probe microscopy: Applications1994Licentiate thesis, comprehensive summary (Other academic)
  • 144.
    Almqvist, Nils
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Studies of plasma-facing materials and macromolecules using scanning probe microscopy1995Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The main topic of this thesis is experimental analysis of material surfaces using scanning probe microscopies. These microscopes are used for characterization through high-resolution topographical imaging, but also for controlled modification of surfaces and molecules. The surface characterization includes evaluation and development of fractal methods for surface roughness determination. The term modification is used for manipulating the structures on a microscale by scraping them with a tiny tip. The major application of this technique in the present work is the analysis of effects induced by plasma-surface interactions. Such studies are fundamental in the understanding of erosion and deposition processes on the first wall in controlled fusion devices. In this work, scanning probe microscopes were for the first time used for studying such plasma-facing materials. Both the surface structure and composition have to be known in order to evaluate new wall-materials for fusion reactors. The materials studied here are graphites, SiC/Al coatings, graphite-silicon mixtures and various silicon carbide based composites. They were all exposed to plasmas, either to lowenergy deuterium plasmas and ions in laboratory experiments, or to the plasma in a socalled tokamak. The results show the usefulness of these high-resolution microscopes in the study of plasma-surface interaction. Several other surface sensitive techniques were also applied, at the home laboratories of our collaborators, the most important ones being Rutherford backscattering spectroscopy and nuclear reaction analysis. The scanning probe microscopy in combination with the ion-beam analysis made it possible to trace fine structural features on the surfaces and to measure the surface roughness. The main results are: (i) the detection of the initial stages of bubble/blister formation on CSi mixtures, SiC/AI coatings and graphites; (ii) the morphological changes and the physical properties of the silicon carbide composites; (iii) the distinction of radiation damages on different phases of multicomponent composites; (iv) the estimation of layer thickness with scanning probe microscopy; (v) the determination of the structure of codeposited layers formed during exposure in a tokamak; (vi) the uptake of deuterium by the materials. The atomic force microscope has also been used to study the human protein spectrin, and we managed to image free spectrins with molecular resolution in an almost natural environment. The elongated spectrin macromolecule was found to be 100 rim long and 5 nm broad. Indications of a substructure were observed. The force between the sensor tip and the molecules was crucial, both for sample movement, manipulation and image resolution. Therefore, the instrument was rebuilt to operate with so called tapping-mode in liquid. Preliminary results with this method on spectrin are presented.

  • 145.
    Almqvist, Nils
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Bhatia, R
    Neuroscience Research Institute, University of California, Santa Barbara.
    Primbs, G
    Neuroscience Research Institute, University of California, Santa Barbara.
    Desai, N
    NutraSweet Company, Chicago.
    Banerjee, S
    Department of Chemical Engineering, University of California, Santa Barbara.
    Lal, R
    Neuroscience Research Institute, University of California, Santa Barbara.
    Elasticity and adhesion force mapping reveals real-time clustering of growth factor receptors and associated changes in local cellular rheological properties2004In: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 86, no 3, p. 1753-1762Article in journal (Refereed)
    Abstract [en]

    Cell surface macromolecules such as receptors and ion channels serve as the interface link between the cytoplasm and the extracellular region. Their density, distribution, and clustering are key spatial features influencing effective and proper physical and biochemical cellular responses to many regulatory signals. In this study, the effect of plasma-membrane receptor clustering on local cell mechanics was obtained from maps of interaction forces between antibody-conjugated atomic force microscope tips and a specific receptor, a vascular endothelial growth factor (VEGF) receptor. The technique allows simultaneous measurement of the real-time motion of specific macromolecules and their effect on local rheological properties like elasticity. The clustering was stimulated by online additions of VEGF, or antibody against VEGF receptors. VEGF receptors are found to concentrate toward the cell boundaries and cluster rapidly after the online additions commence. Elasticity of regions under the clusters is found to change remarkably, with order-of-magnitude stiffness reductions and fluidity increases. The local stiffness reductions are nearly proportional to. receptor density and, being concentrated near the cell edges, provide a mechanism for cell growth and angiogenesis.

  • 146.
    Almqvist, Nils
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Delamo, Y
    Neuroscience Research Institute, University of California.
    Smith, BL
    Thomson, NH
    Laboratoire d'Océanographie Biologique (LOB).
    Bartholdson, A
    Department of Physics and Astronomy, University of Leeds.
    Lal, R
    Marine Science Institute, University of California.
    Brzezinski, M
    Neuroscience Research Institute, University of California.
    Hansma, PK
    Luleå tekniska universitet.
    Micromechanical and structural properties of a pennate diatom investigated by atomic force microscopy2001In: Journal of Microscopy, ISSN 0022-2720, E-ISSN 1365-2818, Vol. 202, no 3, p. 518-532Article in journal (Refereed)
    Abstract [en]

    The mechanisms behind natural nanofabrication of highly structured silicas are increasingly being investigated. We have explored the use of a standard Nanoscope III Multimode atomic force microscope (AFM) to study the silica shell of diatoms. The delicate structures of the shell surface of the diatom Navicula pelliculosa (Breb.) Hilse were imaged and the shell's micromechanical properties were measured semi-quantitatively with a resolution down to approximately 10 nm. The technique to measure elasticity and hardness with the AFM was demonstrated to be useable even on these hard glass-like surfaces, Different experimental configurations and evaluation methods were tested, They gave a consistent result of the shell micromechanical properties, The first results showed that the diatom shell's overall hardness and elasticity was similar to that of known silicas. However, regions with different mechanical proper ties were distinguished. The elastic modulus varied from 7 to 20 GPa, from 20 to 100 GPa and from 30 to hundreds of GPa depending on the location. In general, the hardness measurements showed similar spatial differences, The hardness values ranged from 1 to 12 GPa but one specific part of the shell was even harder. Hence, certain localized regions of the shell were significantly harder or more elastic. These regions coincide with known characteristic features and mechanisms appearing at the different stages of the shell's growth. These results show that this method serves as a complementary tool in the study of silica biomineralization, and can detect eventual crystalline phases.

  • 147.
    Almqvist, Nils
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Fredriksson, Sverker
    Backman, Lars
    Imaging human erythrocyte spectrin with atomic force microscopy1994In: Micron, ISSN 0968-4328, E-ISSN 1878-4291, Vol. 25, no 3, p. 227-232Article in journal (Refereed)
    Abstract [en]

    Isolated spectrin covalently attached to a surface in a liquid environment as well as dried on mica has been studied with a contact-mode atomic force microscope. Both pyramidal and conical-type cantilever tip facets were used in the AFM. Our images show structures and give dimensions that correlate well with previous structural studies using transmission electron microscopy.

  • 148.
    Almqvist, Nils
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Fredriksson, Sverker
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Rubel, Marek
    Royal Institute of Technology, Physics Department, S-10405 Stockholm, Sweden.
    Emmoth, Birger
    Royal Institute of Technology, Physics Department, S-10405 Stockholm, Sweden.
    SFM and STM topographic studies of carbon-based surfaces exposed to deuterium plasma1994In: Book of abstracts: Microprobe Symposium, Vadstena, April 25-26, 1994, 1994Conference paper (Refereed)
  • 149.
    Almqvist, Nils
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Quist, Arjan P
    Mälardalen University, Department of Chemical Engineering, Box 325 SE-63105 Eskilstuna, Sweden.
    Lal, Ratnesh
    University of California, Neuroscience Research Institute, Santa Barbara, CA 93106, USA.
    Elastic properties of living cells studied by multimodal atomic force microscopy2000In: Abstract book Nordic-Baltic SPM Workshop, 2000: abstract #1, 2000Conference paper (Refereed)
  • 150.
    Almqvist, Nils
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Rubel, M.
    Franconi, E.
    Surface characterization of SiC composites exposed to deuterium ions, using atomic force microscopy1995In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 201, no 1-2, p. 277-285Article in journal (Refereed)
    Abstract [en]

    We study the influence of deuterium plasma on the surface structure of SiC based composites. The substrates are silicon carbides doped with titanium diboride, aluminium nitride or graphite. A number of surface sensitive techniques are used to characterize the substrates, before and after exposure to low-energy deuterium ions, the main method being atomic force microscopy. The microscope reveals distinct morphological changes on the irradiated samples. The density and surface area of the samples probably influence the content of deuterium in the surfaces. However, this study shows that the amount of graphite aggregated on the surfaces is of crucial importance for the uptake of deuterium.

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