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  • Public defence: 2020-03-30 10:15 K1, Kåkenhus, NorrköpingOrder onlineBuy this publication >>
    Gryszel, Maciej
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Organic electronic materials for hydrogen peroxide production2020Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Hydrogen peroxide (H2O2) is an important oxidant, used in various fields of industry, such as paper manufacturing, production of polymers, detergents, and cosmetics. Considering that the molecule degrades only to H2O and O2, it is regarded as a green chemical. Unfortunately, the incumbent method of H2O2 synthesis, based on anthraquinone oxidation, although efficient, is not environmentally friendly, as it requires fossil fuels and significant energy input. Therefore, there are efforts underway to reduce the ecological impact of hydrogen peroxide production. Some of the most promising approaches involve catalytic reduction of O2 to H2O2 in an aqueous environment. This can be coupled with water oxidation. As the required energy could be delivered in different ways, hydrogen peroxide synthesis can be achieved by electrocatalysis, photoelectrocatalysis, or photocatalysis.

    This thesis explores the possibility of using organic electronic materials as catalysts for H2O2 evolution in oxygenated water solutions. Organic electronics is a field of materials science focused on conducting and semiconducting organic molecules. These materials offer many possible advantages, related to low cost, flexibility, and good optoelectronic properties. Huge progress in the field over the last years led to their commercial applications in e.g. organic light emitting diodes and photovoltaics. Only very recently have organic electronics begun to be considered from the point of view of catalysis.

    In the first two papers, we investigate electrocatalytic activity of an organic pigment (PTCDI) and a conducting polymer (PEDOT) towards oxygen reduction to hydrogen peroxide. Both types of catalysts are chemically stable and able to operate in a wide pH range. In paper 3, we demonstrate that H2O2-evolving photocathodes can be based on an organic PN heterojunction, giving devices of a record-breaking performance. In the first part of paper 4, the same concept was tested for a naturally-occurring semiconductor, eumelanin, leading to a first report of photoelectrocatalytic properties of this material. In the second part of paper 4, as well as in papers 5 and 6, we explore, respectively, photochemical hydrogen peroxide synthesis with eumelanin, organic semiconductors, and organic dyes. We show that the photostability of catalysts is higher for materials with low-lying HOMO level and it can be increased by an addition of a reducing agent to the reaction system. Our findings prove that already existing organic electronic materials can be successfully applied in H2O2 evolution for environmentally friendly chemical synthesis, suggesting their use in harvesting of solar energy and in situ generation of hydrogen peroxide for biomedical applications.

    List of papers
    1. Organic semiconductor perylenetetracarboxylic diimide (PTCDI) electrodes for electrocatalytic reduction of oxygen to hydrogen peroxide
    Open this publication in new window or tab >>Organic semiconductor perylenetetracarboxylic diimide (PTCDI) electrodes for electrocatalytic reduction of oxygen to hydrogen peroxide
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    2018 (English)In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 54, no 16, p. 1960-1963Article in journal (Refereed) Published
    Abstract [en]

    Hydrogen peroxide is one of the most important industrial chemicals and there is great demand for the production of H2O2 usingmore sustainable and environmentally benign methods. We show electrochemical production of H2O2 by the reduction of O-2, enabled by an organic semiconductor catalyst, N,N-dimethyl perylenetetracarboxylic diimide (PTCDI). We make PTCDI cathodes that are capable of stable and reusable operation in aqueous electrolytes in a pH range of 1-13 with a catalytic figure of merit as high as 26 kg H2O2 per g catalyst per h. These performance and stability open new avenues for organic small molecule semiconductors as electrocatalysts.

    Place, publisher, year, edition, pages
    ROYAL SOC CHEMISTRY, 2018
    National Category
    Other Chemistry Topics
    Identifiers
    urn:nbn:se:liu:diva-145755 (URN)10.1039/c7cc08471d (DOI)000425531500005 ()29323369 (PubMedID)
    Note

    Funding Agencies|Wallenberg Center for Molecular Medicine at Linkoping University

    Available from: 2018-03-22 Created: 2018-03-22 Last updated: 2020-02-25
    2. Electrocatalytic Production of Hydrogen Peroxide with Poly(3,4-ethylenedioxythiophene) Electrodes
    Open this publication in new window or tab >>Electrocatalytic Production of Hydrogen Peroxide with Poly(3,4-ethylenedioxythiophene) Electrodes
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    2019 (English)In: Advanced Sustainable Systems, ISSN 2366-7486, Vol. 3, no 2, p. 1-6, article id 1800110Article in journal (Refereed) Published
    Abstract [en]

    Electrocatalysis for energy‐efficient chemical transformations is a central concept behind sustainable technologies. Numerous efforts focus on synthesizing hydrogen peroxide, a major industrial chemical and potential fuel, using simple and green methods. Electrochemical synthesis of peroxide is a promising route. Herein it is demonstrated that the conducting polymer poly(3,4‐ethylenedioxythiophene), PEDOT, is an efficient and selective heterogeneous catalyst for the direct reduction of oxygen to hydrogen peroxide. While many metallic catalysts are known to generate peroxide, they subsequently catalyze decomposition of peroxide to water. PEDOT electrodes can support continuous generation of high concentrations of peroxide with Faraday efficiency remaining close to 100%. The mechanisms of PEDOT‐catalyzed reduction of O2 to H2O2 using in situ spectroscopic techniques and theoretical calculations, which both corroborate the existence of a chemisorbed reactive intermediate on the polymer chains that kinetically favors the selective reduction reaction to H2O2, are explored. These results offer a viable method for peroxide electrosynthesis and open new possibilities for intrinsic catalytic properties of conducting polymers.

    Place, publisher, year, edition, pages
    Wiley-VCH Verlagsgesellschaft, 2019
    National Category
    Materials Chemistry
    Identifiers
    urn:nbn:se:liu:diva-163609 (URN)10.1002/adsu.201800110 (DOI)000458426200002 ()
    Available from: 2020-02-17 Created: 2020-02-17 Last updated: 2020-02-25Bibliographically approved
    3. Organic heterojunction photocathodes for optimized photoelectrochemical hydrogen peroxide production
    Open this publication in new window or tab >>Organic heterojunction photocathodes for optimized photoelectrochemical hydrogen peroxide production
    2018 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 6, no 48, p. 24709-24716Article in journal (Refereed) Published
    Abstract [en]

    Solar-to-chemical conversion of sunlight into hydrogen peroxide as a chemical fuel is an emerging carbon-free sustainable energy strategy. The process is based on the reduction of dissolved oxygen to hydrogen peroxide. Only limited amounts of photoelectrode materials have been successfully explored for photoelectrochemical production of hydrogen peroxide. Herein we detail approaches to produce robust organic semiconductor photocathodes for peroxide evolution. They are based on evaporated donor-acceptor heterojunctions between phthalocyanine and tetracarboxylic perylenediimide, respectively. These small molecules form nanocrystalline films with good operational stability and high surface area. We discuss critical parameters which allow fabrication of efficient devices. These photocathodes can support continuous generation of high concentrations of peroxide with faradaic efficiency remaining at around 70%. We find that an advantage of the evaporated heterojunctions is that they can be readily vertically stacked to produce tandem cells which produce higher voltages. This feature is desirable for fabricating two-electrode photoelectrochemical cells. Overall, the photocathodes presented here have the highest performance reported to date in terms of photocurrent for peroxide production. These results offer a viable method for peroxide photosynthesis and provide a roadmap of strategies that can be used to produce photoelectrodes with even higher efficiency and productivity.

    Place, publisher, year, edition, pages
    ROYAL SOC CHEMISTRY, 2018
    National Category
    Other Chemical Engineering
    Identifiers
    urn:nbn:se:liu:diva-153662 (URN)10.1039/c8ta08151d (DOI)000453550700005 ()
    Note

    Funding Agencies|Knut and Alice Wallenberg Foundation; Wallenberg Centre for Molecular Medicine at Linkoping University; Vinnova within the framework of Treesearch.se

    Available from: 2019-01-07 Created: 2019-01-07 Last updated: 2020-02-25
    4. Aqueous photo(electro)catalysis with eumelanin thin films
    Open this publication in new window or tab >>Aqueous photo(electro)catalysis with eumelanin thin films
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    2018 (English)In: Materials Horizons, ISSN 2051-6347, E-ISSN 2051-6355, Vol. 5, no 5, p. 984-990Article in journal (Refereed) Published
    Abstract [en]

    We report that eumelanin, the ubiquitous natural pigment found in most living organisms, is a photocatalytic material. Though the photoconductivity of eumelanin and its photochemical reactions with oxygen have been known for some time, eumelanins have not been regarded as photofaradaic materials. We find that eumelanin shows photocathodic behavior for both the oxygen reduction reaction and the hydrogen evolution reaction. Eumelanin films irradiated in aqueous solutions at pH 2 or 7 with simulated solar light photochemically reduce oxygen to hydrogen peroxide with accompanying oxidation of sacrificial oxalate, formate, or phenol. Autooxidation of the eumelanin competes with the oxidation of donors. Deposition of thin films on electrodes yields photoelectrodes with higher photocatalytic stability compared with the case of pure photocatalysis, implicating the successful extraction of positive charges from the eumelanin layer. These results open up new potential applications for eumelanin as a photocatalytically-active biomaterial, and inform the growing fundamental body of knowledge about the physical chemistry of eumelanins.

    Place, publisher, year, edition, pages
    ROYAL SOC CHEMISTRY, 2018
    National Category
    Theoretical Chemistry
    Identifiers
    urn:nbn:se:liu:diva-151797 (URN)10.1039/c8mh00715b (DOI)000444245600023 ()
    Note

    Funding Agencies|Knut and Alice Wallenberg Foundation; Italian Project RELIGHT [PON02_00556_3306937]

    Available from: 2018-10-04 Created: 2018-10-04 Last updated: 2020-02-25
    5. General Observation of Photocatalytic Oxygen Reduction to Hydrogen Peroxide by Organic Semiconductor Thin Films and Colloidal Crystals
    Open this publication in new window or tab >>General Observation of Photocatalytic Oxygen Reduction to Hydrogen Peroxide by Organic Semiconductor Thin Films and Colloidal Crystals
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    2018 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, no 16, p. 13253-13257Article in journal (Refereed) Published
    Abstract [en]

    Low-cost semiconductor photocatalysts offer unique possibilities for industrial chemical transformations and energy conversion applications. We report that a range of organic semiconductors are capable of efficient photocatalytic oxygen reduction to H2O2 in aqueous conditions. These semiconductors, in the form of thin films, support a 2-electron/2-proton redox cycle involving photoreduction of dissolved O-2 to H2O2, with the concurrent photooxidation of organic substrates: formate, oxalate, and phenol. Photochemical oxygen reduction is observed in a pH range from 2 to 12. In cases where valence band energy of the semiconductor is energetically high, autoxidation competes with oxidation of the donors, and thus turnover numbers are low. Materials with deeper valence band energies afford higher stability and also oxidation of H2O to O-2. We found increased H2O2 evolution rate for surfactant-stabilized nanoparticles versus planar thin films. These results evidence that photochemical O-2 reduction may be a widespread feature of organic semiconductors, and open potential avenues for organic semiconductors for catalytic applications.

    Place, publisher, year, edition, pages
    AMER CHEMICAL SOC, 2018
    Keywords
    photochemistry; photocatalysis; hydrogen peroxide; organic semiconductors; oxygen reduction reaction; photoanodes
    National Category
    Materials Chemistry
    Identifiers
    urn:nbn:se:liu:diva-147927 (URN)10.1021/acsami.8b01295 (DOI)000431150900001 ()29624365 (PubMedID)
    Note

    Funding Agencies|Wallenberg Center for Molecular Medicine at Linkoping University; "Aufbruch Bayern" initiative of the state of Bavaria

    Available from: 2018-05-23 Created: 2018-05-23 Last updated: 2020-02-25
    6. Water-Soluble Organic Dyes as Molecular Photocatalysts for H2O2 Evolution
    Open this publication in new window or tab >>Water-Soluble Organic Dyes as Molecular Photocatalysts for H2O2 Evolution
    2019 (English)In: Advanced Sustainable Systems, ISSN 2366-7486, Vol. 3, no 8, p. 1-9, article id 1900027Article in journal (Refereed) Published
    Abstract [en]

    Photochemical generation of hydrogen peroxide via oxygen reduction is a critical component of emerging sustainable energy conversion concepts. Light‐absorbing semiconductors as well as electrodes modified with sensitizers typically catalyze oxygen photoreduction to hydrogen peroxide. Here, it is reported that, in contrast to these heterogeneous systems, a homogeneous solution of a metal‐free organic dye can perform the whole catalytic cycle of hydrogen peroxide photoevolution itself. This cycle can proceed with simultaneous oxidation of various organic molecules as electron donors, or even water. In the three water‐soluble dyes that are experimented with, photoevolution of peroxide occurs favorably at neutral to basic pH. The reaction is first order with respect to dye concentration, and evidence implicates a single‐electron reduction pathway with superoxide as an intermediate. Photostability of the dyes over time correlates with increased oxidation potential of the molecule. The finding that hydrogen peroxide can be produced in aqueous solution with single fully organic molecules performing the entire photocatalytic cycle creates a new avenue for the peroxide carbon free energy cycle.

    Place, publisher, year, edition, pages
    Wiley-VCH Verlagsgesellschaft, 2019
    National Category
    Materials Chemistry
    Identifiers
    urn:nbn:se:liu:diva-163617 (URN)10.1002/adsu.201900027 (DOI)000481496000004 ()2-s2.0-85070881425 (Scopus ID)
    Available from: 2020-02-17 Created: 2020-02-17 Last updated: 2020-02-25Bibliographically approved
  • Public defence: 2020-04-02 10:15 Nobel (BL32), B-building, Linköping
    Bian, Qingzhen
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Excitonic and charge carrier transport in organic materials and device applications2020Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    With the potential for future commercial use, organic electronics have been intensively studied for the last few decades. To exploit the next generation of high-performance devices, detailed study of the underlying physics is essential. Excitonic and charge carrier transport plays a critical role in device performance and related studies have attracted a lot of attention in recent decades. This thesis particularly focused on excitonic and charge carrier transport in organic materials and related device applications.

    In natural light harvesting systems, such as the reaction centers of purple bacteria, quantum coherence has been proposed to be present as a contributor to the related charge and energy transport processes, and almost 100% charge conversion is present in these efficient biological systems. This high energy conversion efficiency inspires the idea that if a similar strategy was used in artificial energy conversion devices such as organic photovoltaics, etc., this could significantly enhance the device’s performance. In the first study, the charge separation process in some donor/acceptor blends was investigated. The contribution of quantum coherence to device performance was studied in detail using several steady state and ultrafast transient techniques. In one efficient donor/acceptor blend, a pronounced coherence of charge separation was identified, which contributed to the enhancement of the photocurrent generation, which finally resulted in efficient device performance.

    For the light emitting diodes, triplet excitons harvesting plays a critical role in device performance. In the thermally activated delayed fluorescence (TADF) materials, due to an efficient reverse intersystem process from triplet excitons to singlet excitons, the losses due to triplet excitons were suppressed. As a result, a desired high quantum yield has been achieved. To enhance device efficiency, the detailed study of the upconversion physics between triplet and singlet is needed. Previous studies have proposed some physical models to explain this efficient upconversion process, while the nature of this physical process is still under debate and unclear. In my second work, we studied the exciton kinetics in two different TADF materials. These TADF materials were inserted in a protein fibril host, and the resulting protein scaffold was able to modify the geometric configuration of the related TADF molecule. As a result, an enhancement of the photoluminescence quantum yield was achieved.

    To achieve efficient device performance in organic electronics, the physical processes at the metal/material interface and charge carrier injection/extraction, also play a critical role. Efficient charge injection can be achieved by Ohmic contact, and charge injection/extraction of metal/organic materials has been intensively studied in the last few decades. In my third study, an efficient hole transport material based on the biopolymer DNA was introduced. A hole doping process was found in the hybrid materials and contributes to the Ohmic contacts. The hybrid material can be used in different organic electronics devices, such as field effect transistors, light emitting diodes and solar cells, and thus demonstrates a general application capability.

    In organic photovoltaics, the loss from the open circuit photovoltages has been an Achilles’ heel for further enhancement of device performance. The voltage loss includes the radiative and non-radiative value, and intensive studies have focused on how to suppress losses from the non-radiative channel. In my fourth study, the non-radiative voltage loss was studied in a series of terpolymer blends and ternary blends. Compared to the ternary blends, a decreased nonradiative loss was found in the terpolymer blends. 

    List of papers
    1. Vibronic coherence contributes to photocurrent generation in organic semiconductor heterojunction diodes
    Open this publication in new window or tab >>Vibronic coherence contributes to photocurrent generation in organic semiconductor heterojunction diodes
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    2020 (English)In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 11, no 1Article in journal (Refereed) Published
    Abstract [en]

    Charge separation dynamics after the absorption of a photon is a fundamental process relevant both for photosynthetic reaction centers and artificial solar conversion devices. It has been proposed that quantum coherence plays a role in the formation of charge carriers in organic photovoltaics, but experimental proofs have been lacking. Here we report experimental evidence of coherence in the charge separation process in organic donor/acceptor heterojunctions, in the form of low frequency oscillatory signature in the kinetics of the transient absorption and nonlinear two-dimensional photocurrent spectroscopy. The coherence plays a decisive role in the initial ~200 femtoseconds as we observe distinct experimental signatures of coherent photocurrent generation. This coherent process breaks the energy barrier limitation for charge formation, thus competing with excitation energy transfer. The physics may inspire the design of new photovoltaic materials with high device performance, which explore the quantum effects in the next-generation optoelectronic applications.

    Place, publisher, year, edition, pages
    Nature Publishing Group, 2020
    National Category
    Other Physics Topics
    Identifiers
    urn:nbn:se:liu:diva-164232 (URN)10.1038/s41467-020-14476-w (DOI)32001688 (PubMedID)2-s2.0-85078713267 (Scopus ID)
    Available from: 2020-03-10 Created: 2020-03-10 Last updated: 2020-03-16Bibliographically approved
  • Public defence: 2020-04-03 10:15 ACAS, A-Building, LinköpingOrder onlineBuy this publication >>
    Wangwacharakul, Promporn
    Linköping University, Department of Management and Engineering, Logistics & Quality Management. Linköping University, Faculty of Science & Engineering.
    Managing Quality in Cross-cultural Settings2020Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    As companies become multinational with subsidiaries in different countries and global customers, they face challenges in managing quality related to cultural diversity. During the past decades, cross-cultural quality management research has emerged, aiming to understand the link between culture and quality management, and to provide support for quality management in different cultural contexts. This research field becomes increasingly important considering global industries of today. Nevertheless, the first standpoint in identifying challenges in cross-cultural quality management in multinational companies remains to be an open question. This also leads to the need for developing an instrument to understand cultural diversity in quality management, from both an internal perspective related to employees and an external perspective related to customers.

    This thesis aims to provide an insight into managing quality in cross-cultural settings, focusing on both multinational companies and companies having global customers. Three studies have been conducted combining qualitative and quantitative research methods. First, case studies were employed to explore the research field and identify challenges in managing quality related to national cultural diversity in multinational companies. The second study developed an instrument based on anchoring vignettes survey to understand cultural diversity in quality management and applied it in two settings. The third study combined an interview-based study with a case study using mixed methods to further investigate and consolidate the results gained from the first two studies, leading to the suggestion of possible strategies to manage quality in multinational companies.

    The thesis findings identify three challenges in managing quality in multinational companies: 1) to translate and implement quality management approaches; 2) to motivate and engage employees in quality work; and 3) to establish shared perceptions of quality management values among employees. Further, an instrument based on anchoring vignettes is suggested to study quality management performance across subsidiaries and to measure customer satisfaction across borders. This instrument contributes to better understanding of cultural diversity and improves the comparability of survey results in quality management measurements. Regarding possible strategies, global integration is needed when a quality culture is weak. In the long-term, companies should promote technical aspects of quality management to form a ‘backbone’ of the quality management system and to set a basis for shared perceptions of quality management values and goals. Consequently, a strong quality culture can be established and companies can benefit from local adaptation of practices.

    List of papers
    1. Cultural Aspects when Implementing Lean Production and Lean Product Development: Experiences from a Swedish Perspective
    Open this publication in new window or tab >>Cultural Aspects when Implementing Lean Production and Lean Product Development: Experiences from a Swedish Perspective
    2014 (English)In: Quality Innovation Prosperity, ISSN 1335-1745, E-ISSN 1338-984X, Vol. 18, no 1, p. 125-140Article in journal (Other academic) Published
    Abstract [en]

    Lean principles and methods, originating in a Japanese cultural context, have spread to a large number of companies throughout the world. The aim of this case study research is to identify and compare national cultural aspects that influence Lean Production and Lean Product Development implementation in Swedish companies. Data were collected through questionnaires, interviews and an industrial workshop with Swedish Lean practitioners. The study shows that some sub-areas in Lean, such as value definition, control systems, leadership, team development, knowledge management, and strategies, are highly dependent on contextual factors related to human, cultural and organizational aspects. These are related to the national culture and should be considered to a higher extent for successful sustainable implementation of Lean in different cultural contexts. As for implementing Lean in Sweden, national cultural characteristics, such as individualism, autonomy and supportive management style fit well with Lean thinking.

    Keywords
    National cultural characteristics; organizational development; case study
    National Category
    Economics and Business Globalisation Studies
    Identifiers
    urn:nbn:se:liu:diva-122733 (URN)10.12776/qip.v18i1.321 (DOI)
    Available from: 2015-11-18 Created: 2015-11-18 Last updated: 2020-03-10Bibliographically approved
    2. Using anchoring vignettes to study quality management across cultures
    Open this publication in new window or tab >>Using anchoring vignettes to study quality management across cultures
    2017 (English)In: International Journal of Quality and Service Sciences, ISSN 1756-669X, E-ISSN 1756-6703, Vol. 9, no 3/4Article in journal (Refereed) Published
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-162111 (URN)
    Available from: 2019-11-19 Created: 2019-11-19 Last updated: 2020-03-10
  • Public defence: 2020-04-03 13:00 K1, Kåkenhus, NorrköpingOrder onlineBuy this publication >>
    Bielsten, Therése
    Linköping University, Department of Health, Medicine and Caring Sciences, Division of Nursing Sciences and Reproductive Health. Linköping University, Faculty of Medicine and Health Sciences.
    “Doing things together”: Towards a health promoting approach to couples’ relationships and everyday life in dementia2020Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Background: Most people with dementia live in their own homes, often together with their partners, who become informal caregivers. Relationship quality and sense of couplehood can be threatened as a result of the transition from a mutually interdependent relationship to a caregiver-care-receiver relationship. This, in turn, may lead to many negative consequences for both partners. Support provided for couples is often divided into different types for the person with dementia and for the partner without dementia and lacks couple-based support that targets the relationship, resources and the couple’s everyday life together.

    Aim: The overall aim of this thesis is to explore couple-centred interventions in dementia and to develop and test a salutogenic, resource-oriented and couple-based intervention among couples in which one partner has dementia living at home.

    Methods and findings: This thesis comprises three parts: The first part Exploring involves two linked reviews, one narrative review (study I A) and one scoping review (study I B) that aim to identify and describe what previous couple-centred interventions comprised and why they were conducted. The results of the reviews revealed a knowledge gap in and a need for easily accessible support that targets couple relationships, resources and everyday life. The second part Developing (study II) refers to the development of an easily accessible resource-oriented couple-management intervention. The first step was to identify priority topics for such an intervention through a co-researcher process with couples living with dementia. This included a comprehensive literature review, interviews with couples in which one partner has dementia, and consultation meetings with expert groups of people with dementia and partners in both Sweden and the UK. The co-researcher process and the expert meetings informed four main themes with corresponding sub-themes that couples with dementia considered as important to their wellbeing in their everyday lives: (1) Home and Neighbourhood, (2) Meaningful Activities and Relationships, (3) Approach and Empowerment, and (4) Couplehood. The themes were further developed and integrated into the multimedia application DemPower, which was developed for the delivery of the intervention. The third part Testing and Evaluating describes a feasibility study (study III) in which the DemPower application was tested for feasibility and acceptability among couples in Sweden and the UK. The results of the feasibility study indicated that the DemPower intervention was feasible and acceptable among couples in which one partner has dementia living at home. The testing and evaluating part also comprise a qualitative study (study IV) that explores the experiences of engaging with DemPower together as a couple living with dementia in Sweden. The findings resulted in the three themes: (1) Growth of the relationship, (2) We are not alone, and (3) Positive approach, which the couples appreciated and associated with the resource-oriented and salutogenic approach of DemPower. The overall findings of the thesis are presented in a concluding synthesis at the end of the thesis. The concluding synthesis, focused on “Meaningfulness”, “Empowering health promotion”, “Normalization” and “Transitions and couplehood”, represents the core findings of this thesis.

    What this thesis adds: This thesis contributes to research, healthcare and the public by highlighting the need for a salutogenic approach toward couples living with dementia. The DemPower application, with its focus on couples’ relationships, resource-orientation and everyday life, has proven feasibility and acceptability and has meaningfully addressed a gap in the literature and in practice. As researchers, healthcare professionals and the public, we need to support couples where one partner has dementia to continue to live as normal life as possible. This can best be achieved by focusing on what couples can do, by inclusion and by valuing them as the experts within dementia research and of their life experiences.

    List of papers
    1. A review of couple-centred interventions in dementia: Exploring the what and why - Part A
    Open this publication in new window or tab >>A review of couple-centred interventions in dementia: Exploring the what and why - Part A
    2019 (English)In: Dementia, ISSN 1471-3012, E-ISSN 1741-2684, Vol. 18, no 7-8, p. 2436-2449Article, review/survey (Refereed) Published
    Abstract [en]

    Introduction Symptoms of dementia bring about challenges to couples relationships. Relationship-focused support has been highlighted to be of significant importance for sustained relationship quality and to reduce the negative impact of dementia on the dyadic relationship. This review aimed to explore the what and why of interventions aimed at couples where one partner has a diagnosis of dementia and in which the couple jointly participate. Method Searches were performed in Academic Search Premier, CINAHL, PsycINFO, PubMed, Scopus and Web of Science from January 2000 to August 2017. Results Six studies were included. Objectives for the person with dementia was related to cognitive function and for the care partner the objectives were related to well-being. The majority of the outcomes were mirrored by the objectives and focused on cognitive function for people with dementia and depression and relationship quality for care partners. Our findings indicate that people with dementia should be included in the assessment of the relationship in order to gain an overall picture of relationship dynamics and to increase tailored support in couple-centred interventions. Conclusions The findings of this review indicate that joint interventions for people with dementia and care partners are lacking a genuine dyadic approach where both partners views of their relationship are valued. In order to identify targets for support and to use the appropriate outcome measures, the quality of the relationship should be recognised and taken into account. Moreover, there is a lack of a salutogenic approach in couple-centred interventions in which couples strengths and resources can be identified and supported.

    Place, publisher, year, edition, pages
    SAGE PUBLICATIONS LTD, 2019
    Keywords
    caregiver; dementia; mild cognitive impairment; review; spouses
    National Category
    Gerontology, specialising in Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-160998 (URN)10.1177/1471301217737652 (DOI)000485953300002 ()29096533 (PubMedID)
    Available from: 2019-10-31 Created: 2019-10-31 Last updated: 2020-03-13
    2. Living Life and Doing Things Together: Collaborative Research With Couples Where One Partner Has a Diagnosis of Dementia
    Open this publication in new window or tab >>Living Life and Doing Things Together: Collaborative Research With Couples Where One Partner Has a Diagnosis of Dementia
    Show others...
    2018 (English)In: Qualitative Health Research, ISSN 1049-7323, E-ISSN 1552-7557, Vol. 28, no 11, p. 1719-1734Article in journal (Refereed) Published
    Abstract [en]

    The aim of this study is to identify relevant content for a self-management guide by using the outcomes of previous research in combination with knowledge and experiences from couples where one partner has a diagnosis of dementia. The study was carried out in three phases: (a) literature search of previous research related to well-being and couplehood in dementia; (b) interviews with couples with dementia based on the findings of the literature search; and (c) further authentication of the findings within expert groups of people with dementia and carers. For analysis of data, we used a hybrid approach of thematic analysis with combined deductive and inductive approaches. The findings of this study indicated that the four main themes Home and Neighborhood, Meaningful Activities and Relationships, Approach and Empowerment, and Couplehood with related subthemes could be appropriate targets for a self-management guide for couples where one partner has a diagnosis of dementia.

    Place, publisher, year, edition, pages
    SAGE PUBLICATIONS INC, 2018
    Keywords
    couples; collaborative research; dementia; salutogenesis; self-management; Sweden; thematic analysis; UK
    National Category
    Other Social Sciences not elsewhere specified
    Identifiers
    urn:nbn:se:liu:diva-151196 (URN)10.1177/1049732318786944 (DOI)000442412400004 ()30033851 (PubMedID)
    Available from: 2018-09-17 Created: 2018-09-17 Last updated: 2020-03-13
  • Public defence: 2020-04-06 09:15 Nobel, Linköping
    Marcus, Carina
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Sensor and Signature Modeling for Aircraft Conceptual Development2020Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The aircraft design process has several phases, the first of which is conceptual design. In this phase, models describing an aircraft concept’s properties are used to evaluate its function and identify designs that meet given requirements. Fighter aircraft are generally expected to be capable of communicating, delivering munitions and gathering data about their environment to gain situational awareness. The ability to avoid detection by hostile sensors can also be important, depending on the aircraft’s role.

    The design process of the aircraft itself has usually focused on an aircraft’s flight performance and ability to carry loads, e.g. munitions and extra fuel. While acceleration, rate of turn, maximum speed, and operational range are important parameters, the success of military missions also depends on sensor capabilities and signature levels. However, sensor installation and signature reduction measures can affect the aircraft and its flight performance. Whether an aircraft concept fulfills the requirements given is evaluated using simulations in appropriate scenarios. The concept’s performance is assessed using models of aircraft properties, weapon properties, sensor capabilities and signature levels. Models of the aircraft properties are usually connected dynamically, and respond to changes in such things as the size of the concept. However, sensor and signature models are often the result of a separate optimization process and are only statically connected to the aircraft model. The complete aircraft model can be improved by introducing sensor and signature models that dynamically describe both their functions, and their impact on the aircraft. Concurrent design of all the aircraft properties may improve the quality of results from scenario simulations. When models used in simulations contain parameters coupled to each other, analysis of the resulting data is particularly important because that is what supports a decision-maker’s design choice.

    Sensor and signature models, in some cases combined with flight performance models, have been used to test methodologies intended for use in conceptual aircraft design. The results show that even seemingly simple models can produce results that can make a significant contribution to the aircraft design process.

    List of papers
    1. Military utility: A proposed concept to support decision-making
    Open this publication in new window or tab >>Military utility: A proposed concept to support decision-making
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    2015 (English)In: Technology in society, ISSN 0160-791X, E-ISSN 1879-3274, Vol. 43, p. 23-32Article in journal (Refereed) Published
    Abstract [en]

    A concept called Military Utility is proposed for the study of the use of technology in military operations. The proposed concept includes a three-level structure representing key features and their detailed components. On basic level the Military Utility of a technical system, to a military actor, in a specific context, is a compound measure of the military effectiveness, of the assessed technical system's suitability to the military capability system and of the affordability. The concept is derived through conceptual analysis and is based on related concepts used in social sciences, the military domain and Systems Engineering. It is argued that the concept has qualitative explanatory powers and can support military decision-making regarding technology in forecasts, defense planning, development, utilization and the lessons learned process. The suggested concept is expected to contribute to the development of the science of Military-Technology and to be found useful to actors related to defense.

    Place, publisher, year, edition, pages
    Elsevier, 2015
    Keywords
    Technology, utility, decision-making
    National Category
    Mechanical Engineering
    Research subject
    Systems science for defence and security
    Identifiers
    urn:nbn:se:liu:diva-163641 (URN)10.1016/j.techsoc.2015.07.001 (DOI)000215364900003 ()
    Available from: 2020-02-17 Created: 2020-02-17 Last updated: 2020-02-17Bibliographically approved
    2. Balancing the radar and long wavelength infrared signature properties in concept analysis of combat aircraft - A proof of concept
    Open this publication in new window or tab >>Balancing the radar and long wavelength infrared signature properties in concept analysis of combat aircraft - A proof of concept
    2017 (English)In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 71, p. 733-741Article in journal (Refereed) Published
    Abstract [en]

    Designing combat aircraft with high military effectiveness, affordability and military suitability requires balancing the efforts of many engineering disciplines during all phases of the development. One particular challenge is aircraft survivability, the aircrafts ability to avoid or withstand hostile actions. Signature management is one way of increasing the survivability by improving the ability to avoid detection. Here, the long-wave infrared and radar signatures are studied simultaneously in a mission context. By establishing a system of systems approach at mission system level, the risk of sub optimization at a technical level is greatly reduced. A relevant scenario is presented where the aim is to incapacitate an air-defense system using three different tactics: A low-altitude cruise missile option, a low and medium altitude combat aircraft option. The technical sub-models, i.e. the properties of the signatures, the weapons and the sensors are modeled to a level suitable for early concept development. The results from the scenario simulations are useful for a relative comparison of properties. Depending on the situation, first detection is made by either radar or infrared sensors. Although the modeling is basic, the complexity of the infrared signature and detection chain is demonstrated and possible pivot points for the balancing of radar and IR signature requirements are identified. The evaluation methodology can be used for qualitative evaluation of aircraft concepts at different design phases, provided that the technical models are adapted to a suitable level of detail. (C) 2017 Elsevier Masson SAS. All rights reserved.

    Place, publisher, year, edition, pages
    ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER, 2017
    Keywords
    Radar; Infrared; Signatures; Scenario; Evaluation
    National Category
    Aerospace Engineering
    Identifiers
    urn:nbn:se:liu:diva-144148 (URN)10.1016/j.ast.2017.10.022 (DOI)000418313700067 ()
    Note

    Funding Agencies|Saab Aeronautics; Swedish Defence University; Swedish Armed Forces

    Available from: 2018-01-09 Created: 2018-01-09 Last updated: 2020-02-17
    3. Balancing Antenna Performance vs. Radar Cross Section for a Passive Radar-Detecting Sensor on an Aircraft
    Open this publication in new window or tab >>Balancing Antenna Performance vs. Radar Cross Section for a Passive Radar-Detecting Sensor on an Aircraft
    2019 (English)Conference paper, Published paper (Refereed)
    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-163593 (URN)10.2514/6.2019-2047 (DOI)
    Conference
    AIAA SciTech'19
    Available from: 2020-02-17 Created: 2020-02-17 Last updated: 2020-02-17
    4. Detection Chain Model Designed for Aircraft Concept Development
    Open this publication in new window or tab >>Detection Chain Model Designed for Aircraft Concept Development
    2019 (English)In: Journal of Aircraft, ISSN 0021-8669, E-ISSN 1533-3868, Vol. 56, no 5, p. 1942-1950Article in journal (Refereed) Published
    Abstract [en]

    Simultaneous design of an aircraft and its sensor systems offers advantages over integrating standard sensors because the need for sensor function can be balanced against the integration issues. A model of the detection chain is here defined as mathematical representations of the sensors, the wave propagation, and the signatures of the target. When used in aircraft concept development in a design space exploration context, the model of the detection chain needs to be simple yet detailed enough to sufficiently describe both the sensor performance and the impact it has on the infrastructure of the aircraft. In this paper a detection chain model for radar is introduced. It includes the detection range, search volume, and signature together with implications in terms of the aircraft infrastructure the parameters of mass, the volume, and power and cooling requirements as a function of antenna size. The best choice of radar cannot be determined by the sensor function alone; it has to be evaluated together with the aircraft in tactical simulations in order to obtain the complete picture. The benefits of a larger antenna can, to some degree, be counteracted by the changes to the aircraft that affect its flight performance.

    Place, publisher, year, edition, pages
    AMER INST AERONAUTICS ASTRONAUTICS, 2019
    National Category
    Aerospace Engineering
    Identifiers
    urn:nbn:se:liu:diva-161415 (URN)10.2514/1.C034930 (DOI)000489572700017 ()
    Available from: 2019-10-31 Created: 2019-10-31 Last updated: 2020-02-17
    5. Aspects of the design, evaluation and accuracy of airborne sensor clusters using time-difference of arrival
    Open this publication in new window or tab >>Aspects of the design, evaluation and accuracy of airborne sensor clusters using time-difference of arrival
    2019 (English)In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 92, p. 892-900Article in journal (Refereed) Published
    Abstract [en]

    One way of improving situational awareness without increasing the risk of detection is to use passive sensor systems. If this capability is provided by several aircraft in a cluster, which can incorporate small basic sensor platforms, advantages can be gained such as longer baselines and an increased number of sensors in the cluster. In this paper, a methodology is presented that links results from signal processing to a Design Space Exploration, DSE, regarding sensor clusters when designing clusters that can operate both independently and in cooperation with other systems. When using Time-Difference of Arrival, the accuracy of the estimated location of a signal source depends on errors in timing and positioning of the sensors, errors in estimating signal arrival times and number of sensors and their spatial distribution. The Cramer-Rao Lower Bound is used to investigate the accuracy of signal source estimates for five different clusters and two levels of timing and positioning accuracy. The results show that the direction of arrival estimates are more accurate than those for the range. Although more sensors generally increased the accuracy, their spatial distribution and baseline related to the distance to the signal source also influence the quality of the results. The DSE process is supported by the collected presentation of the data regarding the measurement accuracy of the different sensor configurations, incorporating both cluster configuration as well as the positioning and timing. Having readily accessible data, the decision makers can focus on choosing the sensor system that meets the operational needs. (C) 2019 Elsevier Masson SAS. All rights reserved.

    Place, publisher, year, edition, pages
    ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER, 2019
    Keywords
    Design Space Exploration; TDOA; Accuracy; Passive; Estimation; Source position; Sensor cluster
    National Category
    Aerospace Engineering
    Identifiers
    urn:nbn:se:liu:diva-161194 (URN)10.1016/j.ast.2019.07.025 (DOI)000485852600074 ()
    Available from: 2019-10-25 Created: 2019-10-25 Last updated: 2020-02-17
  • Public defence: 2020-04-17 09:00 Eken, Building 421, Entrance 65, LinköpingOrder onlineBuy this publication >>
    Zötterman, Johan
    Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Anaesthetics, Operations and Specialty Surgery Center, Department of Hand and Plastic Surgery.
    Laser Speckle Contrast Imaging in Reconstructive Surgery2020Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Objectives

    Reconstructive surgery aims to restore function or normal appearance by reconstructing defective organs after trauma or disease. In patients undergoing reconstructive surgery, previous trauma, surgery or radiotherapy can result in compromised blood supply. This will affect the viability of the tissue and increases the risk for postoperative complications, such as ischemia and infection. It is therefore important to assess the tissue viability, both before, during and after the surgery. This can be done using different techniques that monitor the perfusion of the skin covering the affected area. In this thesis, LSCI have been evaluated for tissue monitoring in reconstructive surgery. The technique allows for a fast and noninvasive assessment of superficial tissue perfusion over a wide field. Based on previous work on the technology, we have seen clear advantages with LSCI compared to other methods, for example laser Doppler flowmetry (LDF). We have evaluated laser speckle contrast imaging (LSCI) as a tool for tissue monitoring in reconstructive surgery in four studies.

    Methods

    In study I we used a bench top model and healthy subjects to address methodological concerns subjected to the LSCI technology. We investigated the effect of motion distance and angle on the assessed perfusion value In study II we used a porcine model to compare LSCI and LDF as tools to detect partial and full venous outflow obstruction. We used both methods to assess a flap based on the cranial gluteal artery perforator with partial and complete occlusion of the vein and artery. In study III we used the same porcine model as in study II to investigate the possibility to use LSCI intraoperatively to identify flap areas with compromised circulation and thereby predict areas with a high risk of postoperative necrosis. In study IV we used LSCI for intraoperative evaluation of tissue viability during deep inferior epigastric perforator (DIEP) free flap surgery and to investigate the perfusion distribution according to the Hartrampf zones, as measured with LSCI, in relation to the selected perforator in the deep inferior epigastric perforator free flap.

    Results

    In study I we saw that tissue perfusion as measured with LSCI increases with increasing tissue motion, independent of frame rate, number of images, and tissue perfusion. Measured perfusion will decrease when images are acquired at an angle larger than 45° but distances between 15 and 40 cm do not affect the measured perfusion. In study II we observed significant decreases in perfusion during both partial and complete venous occlusion with both LSCI and LDF. However, higher variability seen with LDF, measured as % coefficient of variation. In study III a decrease in perfusion during the first 30 min after raising the flap and a perfusion value below 25 PU after 30 min was a predictor for tissue morbidity 72h after surgery. In study IV the highest perfusion values were found in zone I and higher perfusion in zone II compared to zone III, directly after the flap was raised. No remaining significant difference between zone I, II and III could be seen after anastomosis of the vessels. All flaps with a minimum perfusion <30 PU, measured after the flap was shaped and inserted, later suffered from partial flap necrosis.

    Conclusion

    LSCI is a technology that has the potential to contribute to tissue monitoring in reconstructive surgery. It has many advantages over other techniques, such as the fast acquisition time, the spatial resolution and the fact that it is completely non-invasive. However, the current system is still too bulky to be easily introduced into a clinical setting and the technology is also subject to certain drawbacks which limit its usability. It is sensitive to motion artefacts; only superficial tissue is assessed and cannot offer absolute perfusion data. If these disadvantages could be addressed, LSCI could contribute to a more accurate survey of tissue perfusion and thus better outcome in reconstructive surgery.

    List of papers
    1. Methodological concerns with laser speckle contrast imaging in clinical evaluation of microcirculation
    Open this publication in new window or tab >>Methodological concerns with laser speckle contrast imaging in clinical evaluation of microcirculation
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    2017 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 12, no 3, article id e0174703Article in journal (Refereed) Published
    Abstract [en]

    Background Laser Speckle Contrast Imaging (LSCI) is a non-invasive and fast technique for measuring microvascular blood flow that recently has found clinical use for burn assessment and evaluation of flaps. Tissue motion caused by for example breathing or patient movements may however affect the measurements in these clinical applications, as may distance between the camera and the skin and tissue curvature. Therefore, the aims of this study were to investigate the effect of frame rate, number of frames/image, movement of the tissue, measuring distance and tissue curvature on the measured perfusion. Methods Methyl nicotinate-induced vasodilation in the forearm skin was measured using LSCI during controlled motion at different speeds, using different combinations of frame rate and number of frames/image, and at varying camera angles and distances. Experiments were made on healthy volunteers and on a cloth soaked in a colloidal suspension of polystyrene microspheres. Results Measured perfusion increased with tissue motion speed. The relation was independent of the absolute perfusion in the skin and of frame rate and number of frames/image. The measured perfusion decreased with increasing angles (16% at 60, p = 0.01). Measured perfusion did not vary significantly between measurement distances from 15 to 40 cm (p = 0.77, %CV 0.9%). Conclusion Tissue motion increases and measurement angles beyond 45 decrease the measured perfusion in LSCI. These findings have to be taken into account when LSCI is used to assess moving or curved tissue surfaces, which is common in clinical applications.

    Place, publisher, year, edition, pages
    PUBLIC LIBRARY SCIENCE, 2017
    National Category
    Radiology, Nuclear Medicine and Medical Imaging
    Identifiers
    urn:nbn:se:liu:diva-137098 (URN)10.1371/journal.pone.0174703 (DOI)000399174800074 ()28358906 (PubMedID)
    Note

    Funding Agencies|ALF grants, Region Ostergotland

    Available from: 2017-05-05 Created: 2017-05-05 Last updated: 2020-03-18
    2. Monitoring of partial and full venous outflow obstruction in a porcine flap model using laser speckle contrast imaging
    Open this publication in new window or tab >>Monitoring of partial and full venous outflow obstruction in a porcine flap model using laser speckle contrast imaging
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    2016 (English)In: Journal of Plastic, Reconstructive & Aesthetic Surgery, ISSN 1748-6815, E-ISSN 1532-1959, Vol. 69, no 7, p. 936-943Article in journal (Refereed) Published
    Abstract [en]

    Background: In microsurgery, there is a demand for more reliable methods of postoperative monitoring of free flaps, especially with regard to tissue-threatening obstructions of the feeding arteries and draining veins. In this study, we evaluated laser speckle contrast imaging (LSCI) and laser Doppler flowmetry (LDF) to assess their possibilities to detect partial and full venous outflow obstruction, as well as full arterial occlusion, in a porcine flap model. Methods: Cranial gluteal artery perforator flaps (CGAPs) were raised, and arterial and venous blood flow to and from the flaps was monitored using ultrasonic flow probes. The venous flow was altered with an inflatable cuff to simulate partial and full (50% and 100%) venous obstruction, and arterial flow was completely obstructed using clamps. The flap microcirculation was monitored using LSCI and LDF. Results: Both LDF and the LSCI detected significant changes in flap perfusion. After partial (50%) venous occlusion, perfusion decreased from baseline, LSCI: 63.5 +/- 12.9 PU (p = 0.01), LDF 31.3 +/- 15.7 (p = 0.64). After 100% venous occlusion, a further decrease in perfusion was observed: LSCI 54.6 +/- 14.2 PU (p amp;lt; 0.001) and LDF 16.7 +/- 12.8 PU (p amp;lt; 0.001). After release of the venous cuff, LSCI detected a return of the perfusion to a level slightly, but not significantly, below the baseline level 70.1 +/- 11.5 PU (p=0.39), while the LDF signal returned to a level not significant from the baseline 36.1 +/- 17.9 PU (p amp;gt; 0.99). Perfusion during 100% arterial occlusion decreased significantly as measured with both methods, LSCI: 48.3 +/- 7.7 (PU, pamp;lt;0.001) and LDF: 8.5 +/- 4.0 PU (pamp;lt;0.001). During 50% and 100% venous occlusion, LSCI showed a 20% and 26% inter-subject variability (CV%), respectively, compared to 50% and 77% for LDF. Conclusions: LSCI offers sensitive and reproducible measurements of flap microcirculation and seems more reliable in detecting decreases in blood perfusion caused by venous obstruction. It also allows for perfusion measurements in a relatively large area of flap tissue. This may be useful in identifying areas of the flap with compromised microcirculation during and after surgery. (C) 2016 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.

    Place, publisher, year, edition, pages
    ELSEVIER SCI LTD, 2016
    Keywords
    Free flaps; Venous occlusion; Arterial occlusion; Laser Doppler; Laser speckle contrast imaging
    National Category
    Surgery
    Identifiers
    urn:nbn:se:liu:diva-130059 (URN)10.1016/j.bjps.2016.02.015 (DOI)000377698600010 ()27026039 (PubMedID)
    Note

    Funding Agencies|county of Ostergotland

    Available from: 2016-07-06 Created: 2016-07-06 Last updated: 2020-03-18
    3. The use of laser speckle contrast imaging to predict flap necrosis: An experimental study in a porcine flap model
    Open this publication in new window or tab >>The use of laser speckle contrast imaging to predict flap necrosis: An experimental study in a porcine flap model
    2019 (English)In: Journal of Plastic, Reconstructive & Aesthetic Surgery, ISSN 1748-6815, E-ISSN 1532-1959, Vol. 72, no 5, p. 771-777Article in journal (Refereed) Published
    Abstract [en]

    Background: We evaluated the use of laser speckle contrast imaging (LSCI) in the perioperative planning in reconstructive flap surgery. The aim of the study was to investigate whether LSCI can predict regions with a high risk of developing postoperative necrosis. Our hypothesis was that, perioperatively, such regions have perfusion values below a threshold value and show a negative perfusion trend. Methods: A porcine flap model based on the cranial gluteal artery perforator was used. Images were acquired before surgery, immediately after surgery (t = 0), after 30 min (t =30 min), and after 72h (t = 72 h). Regions of interest (ROIs) were chosen along the central axis of the flap. Clinical evaluation of the flap was made during each time point. Results: At t = 72 h, a demarcation line could be seen at a distance of 15.8 +/- 0.4 cm away from the proximal border of the flaps. At t =0, perfusion decreased gradually from the proximal to the distal ROI. At t =30 min, perfusion was significantly lower in the ROI distal to the final demarcation line than that at t = 0, and in all flaps, these ROIs had a perfusion amp;lt;25 PU. At t= 72 h, perfusion in the ROI proximal to this line returned to baseline levels, whereas perfusion in the distal ROI remained low. Conclusions: In our model, a decrease in perfusion during the first 30 min after surgery and a perfusion amp;lt;25 PU at t = 30 min was a predictor for tissue morbidity 72 h after surgery, which indicates that LSCI is a promising technique for perioperative monitoring in reconstructive flap surgery. (C) 2018 Published by Elsevier Ltd on behalf of British Association of Plastic, Reconstructive and Aesthetic Surgeons.

    Place, publisher, year, edition, pages
    ELSEVIER SCI LTD, 2019
    Keywords
    Flap monitoring; Reconstructive surgery; Laser speckle contrast imaging; Partial flap necrosis
    National Category
    Surgery
    Identifiers
    urn:nbn:se:liu:diva-156911 (URN)10.1016/j.bjps.2018.11.021 (DOI)000464986400009 ()30711464 (PubMedID)
    Note

    Funding Agencies|County of Ostergotland

    Available from: 2019-05-28 Created: 2019-05-28 Last updated: 2020-03-18
    4. Intraoperative Laser Speckle Contrast Imaging in DIEP Breast Reconstruction: A Prospective Case Series Study
    Open this publication in new window or tab >>Intraoperative Laser Speckle Contrast Imaging in DIEP Breast Reconstruction: A Prospective Case Series Study
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    2020 (English)In: Plastic and reconstructive surgery. Global open, ISSN 2169-7574, Vol. 8, no 1, p. e2529-e2529Article in journal (Refereed) Published
    Abstract [en]

    Laser speckle contrast imaging (LSCI) is a laser-based perfusion imaging technique that recently has been shown to predict ischemic necrosis in an experimental flap model and predicting healing time of scald burns. The aims were to investigate perfusion in relation to the selected perforator during deep inferior epigastric artery perforator (DIEP) flap surgery, and to evaluate LSCI in assisting of prediction of postoperative complications. METHODS: Twenty-three patients who underwent DIEP-procedures for breast reconstruction at 2 centers were included. Perfusion was measured in 4 zones at baseline, after raising, after anastomosis, and after shaping the flap. The perfusion in relation to the selected perforator and the accuracy of LSCI in predicting complications were analyzed. RESULTS: After raising the flap, zone I showed the highest perfusion (65 ± 10 perfusion units, PU), followed by zone II (58 ± 12 PU), zone III (53 ± 10 PU), and zone IV (45 ± 10 PU). The perfusion in zone I was higher than zone III (P = 0.002) and zone IV (P < 0.001). After anastomosis, zone IV had lower perfusion than zone I (P < 0.001), zone II (P = 0.01), and zone III (P = 0.02). Flaps with areas <30 PU after surgery had partial necrosis postoperatively (n = 4). CONCLUSIONS: Perfusion is highest in zone I. No perfusion difference was found between zones II and III. Perfusion <30 PU after surgery was correlated with partial necrosis. LSCI is a promising tool for measurement of flap perfusion and assessment of risk of postoperative ischemic complications.

    Place, publisher, year, edition, pages
    Wolters Kluwer, 2020
    National Category
    Surgery
    Identifiers
    urn:nbn:se:liu:diva-164324 (URN)10.1097/GOX.0000000000002529 (DOI)32095386 (PubMedID)
    Note

    32095386[pmid]; PMC7015619[pmcid]

    Available from: 2020-03-17 Created: 2020-03-17 Last updated: 2020-03-23Bibliographically approved
  • Public defence: 2020-04-17 10:15 K3 Önnesjösalen, Kåkenhus, NorrköpingOrder onlineBuy this publication >>
    Adam, Rania Elhadi
    Linköping University, Department of Science and Technology, Physics, Electronics and Mathematics. Linköping University, Faculty of Science & Engineering.
    Synthesis and Characterization of Some Nanostructured Materials for Visible Light-driven Photo Processes2020Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Nanostructured materials for visible light driven photo-processes such as photodegradation of organic pollutants and photoelectrochemical (PEC) water oxidation for hydrogen production are very attractive because of the positive impact on the environment. Metal oxides-based nanostructures are widely used in these photoprocesses due to their unique properties. But single nanostructured metal oxide material might suffer from low efficiency and instability in aqueous solutions under visible light. These facts make it important to have an efficient and reliable nanocomposite for the photo-processes. The combination of different nanomaterials to form a composite configuration can produce a material with new properties. The new properties which are due to the synergetic effect, are a combination of the properties of all the counterparts of the nanocomposite. Zinc oxides (ZnO) have unique optical and electrical properties which grant it to be used in optoelectronics, sensors, solar cells, nanogenerators, and photocatalysis activities. Although ZnO absorbs visible light from the sun due to the deep level band, it mainly absorbs ultraviolet wavelengths which constitute a small portion of the whole solar spectrum range. Also, ZnO has a problem with the high recombination rate of the photogenerated electrons. These problems might reduce its applicability to the photo-process. Therefore, our aim is to develop and investigate different nanocomposites materials based on the ZnO nanostructures for the enhancement of photocatalysis processes using the visible solar light as a green source of energy. Two photo-processes were applied to examine the developed nanocomposites through photocatalysis: (1) the photodegradation of organic dyes, (2) PEC water splitting. In the first photo-process, we used the ZnO nanoparticles (NPs), Magnesium (Mg)-doped ZnO NPs, and plasmonic ZnO/graphene-based nanocomposite for the decomposition of some organic dyes that have been used in industries. For the second photo-process, ZnO photoelectrode composite with different silver-based semiconductors to enhance the performance of the ZnO photoelectrode was used for PEC reaction analysis to perform water splitting. The characterization and photocatalysis experiment results showed remarkable enhancement in the photocatalysis efficiency of the synthesized nanocomposites. The observed improved properties of the ZnO are due to the synergetic effects are caused by the addition of the other nanomaterials. Hence, the present thesis attends to the synthesis and characterization of some nanostructured materials composite with ZnO that are promising candidates for visible light-driven photo-processes.  

    List of papers
    1. Synthesis of ZnO nanoparticles by co-precipitation method for solar driven photodegradation of Congo red dye at different pH
    Open this publication in new window or tab >>Synthesis of ZnO nanoparticles by co-precipitation method for solar driven photodegradation of Congo red dye at different pH
    2018 (English)In: PHOTONICS AND NANOSTRUCTURES-FUNDAMENTALS AND APPLICATIONS, ISSN 1569-4410, Vol. 32, p. 11-18Article in journal (Refereed) Published
    Abstract [en]

    Solar driven photocatalytic processes to remove organic pollutants from wastewater and other aqueous solutions is very important and useful due to its environmental benefits regarding sustainability aspect. In this article, we report a study on the use of bare zinc oxide (ZnO) nanoparticles (NPs) prepared by the chemical low temperature co-precipitation method and used as a catalyst to degrade the Congo red dye from aqueous solution using solar radiation. We performed the photocatalytic experiments for degradation of Congo red dye under solar radiation at different pH values. The results showed that the ZnO NPs are effective under solar radiation for degradation of Congo red dye. Even when the pH was varied down to 4 or raised to 10, the degradation was observed to be slightly improved. This result is due to the excess of radicals species, which enhance the photocatalytic process. In general, the observed degradation efficiency of the ZnO NPs is due to the deep level defects within the band gap that were introduced during the growth process of the ZnO NPs, which enhance the absorption wavelength band towards the visible light region. Recycling of the ZnO NPs for 3 successive runs have indicated the feasibility of reusing the NPs for several times. This implies that by using bare ZnO NPs an efficient approach for degradation of toxic waste can be achieved. Radical scavengers were used to evaluate the role of the radicals in the reaction mechanism.

    Place, publisher, year, edition, pages
    ELSEVIER SCIENCE BV, 2018
    Keywords
    ZnO nanoparticles; Point defects; Photocatalytic
    National Category
    Atom and Molecular Physics and Optics
    Identifiers
    urn:nbn:se:liu:diva-153525 (URN)10.1016/j.photonics.2018.08.005 (DOI)000451653700003 ()
    Note

    Funding Agencies|department of Science and Technology, Linkoping University, Sweden

    Available from: 2018-12-20 Created: 2018-12-20 Last updated: 2020-03-18
    2. Synthesis of Mg-doped ZnO NPs via a chemical low-temperature method and investigation of the efficient photocatalytic activity for the degradation of dyes under solar light
    Open this publication in new window or tab >>Synthesis of Mg-doped ZnO NPs via a chemical low-temperature method and investigation of the efficient photocatalytic activity for the degradation of dyes under solar light
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    2020 (English)In: Solid State Sciences, ISSN 1293-2558, E-ISSN 1873-3085, Vol. 99, article id 106053Article in journal (Refereed) Published
    Abstract [en]

    Doped semiconductors nanostructures (NSs) have shown great interest as a potential for green and efficient photocatalysis activities. Magnesium (Mg)-doped zinc oxide (ZnO) nanoparticles (NPs) has been synthesized by a one-step chemical low temperature (60 °C) co-precipitation method without further calcination and their photocatalytic performance for photodegradation of Methylene blue (MB) dye under the illumination of solar light is investigated. The crystal structure of the synthesized NPs is examined by X-ray diffraction (XRD). XRD data indicates a slight shift towards higher 2θ angle in Mg-doped samples as compared to the pure ZnO NPs which suggest the incorporation of Mg2+ into ZnO crystal lattice. X-ray photoelectron spectroscopy (XPS), UV–Vis spectrophotometer and cathodoluminescence (CL) spectroscopy, were used to study electronics, and optical properties, respectively. The XPS analysis confirms the substitution of the Zn2+ by the Mg2+ into the ZnO crystal lattice in agreement with the XRD data. The photocatalytic activities showed a significant enhancement of the Mg-doped ZnO NPs in comparison with pure ZnO NPs. Hole/radical scavengers were used to reveal the mechanism of the photodegradation. It was found that the addition of the Mg to the ZnO lattices increases the absorption of the hydroxyl ions at the surface of the NPs and hence acts as a trap site leading to decrease the electron-hole pair and consequently enhancing the photodegradation.

    Place, publisher, year, edition, pages
    Elsevier, 2020
    Keywords
    ZnO nanoparticles, Mg-doped ZnO NPs, Photocatalytic, Photodegradation, Methylene blue, Congo red
    National Category
    Materials Chemistry
    Identifiers
    urn:nbn:se:liu:diva-164333 (URN)10.1016/j.solidstatesciences.2019.106053 (DOI)000516720100024 ()2-s2.0-85074706430 (Scopus ID)
    Available from: 2020-03-18 Created: 2020-03-18 Last updated: 2020-03-24Bibliographically approved
    3. Graphene-based plasmonic nanocomposites for highly enhanced solar-driven photocatalytic activities
    Open this publication in new window or tab >>Graphene-based plasmonic nanocomposites for highly enhanced solar-driven photocatalytic activities
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    2019 (English)In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 9, no 52, p. 30585-30598Article in journal (Refereed) Published
    Abstract [en]

    High-efficiency photocatalysts are crucial for the removal of organic pollutants and environmental sustainability. In the present work, we report on a new low-temperature hydrothermal chemical method, assisted by ultrasonication, to synthesize disruptive plasmonic ZnO/graphene/Ag/AgI nanocomposites for solar-driven photocatalysis. The plasmonic nanocomposites were investigated by a wide range of characterization techniques, confirming successful formation of photocatalysts with excellent degradation efficiency. Using Congo red as a model dye molecule, our experimental results demonstrated a photocatalytic reactivity exceeding 90% efficiency after one hour simulated solar irradiation. The significantly enhanced degradation efficiency is attributed to improved electronic properties of the nanocomposites by hybridization of the graphene and to the addition of Ag/AgI which generates a strong surface plasmon resonance effect in the metallic silver further improving the photocatalytic activity and stability under solar irradiation. Scavenger experiments suggest that superoxide and hydroxyl radicals are responsible for the photodegradation of Congo red. Our findings are important for the fundamental understanding of the photocatalytic mechanism of ZnO/graphene/Ag/AgI nanocomposites and can lead to further development of novel efficient photocatalyst materials.

    Place, publisher, year, edition, pages
    Royal Meteorological Society, 2019
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-160568 (URN)10.1039/C9RA06273D (DOI)000487989300064 ()
    Note

    Funding agencies: Department of Science and Technology (ITN) at Campus Norrkoping, Linkoping University, Sweden; Knut and Alice Wallenberg FoundationKnut & Alice Wallenberg Foundation

    Available from: 2019-09-30 Created: 2019-09-30 Last updated: 2020-03-18Bibliographically approved
    4. n–n ZnO–Ag2CrO4 heterojunction photoelectrodes with enhanced visible-light photoelectrochemical properties
    Open this publication in new window or tab >>n–n ZnO–Ag2CrO4 heterojunction photoelectrodes with enhanced visible-light photoelectrochemical properties
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    2019 (English)In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 9, no 14, p. 7992-8001Article in journal (Refereed) Published
    Abstract [en]

    In this study, ZnO nanorods (NRs) were hydrothermally grown on an Au-coated glass substrate at a relatively low temperature (90 °C), followed by the deposition of Ag2CrO4 particles via a successive ionic layer adsorption and reaction (SILAR) route. The content of the Ag2CrO4 particles on ZnO NRs was controlled by changing the number of SILAR cycles. The fabricated ZnO–Ag2CrO4 heterojunction photoelectrodes were subjected to morphological, structural, compositional, and optical property analyses; their photoelectrochemical (PEC) properties were investigated under simulated solar light illumination. The photocurrent responses confirmed that the ability of the ZnO–Ag2CrO4 heterojunction photoelectrodes to separate the photo-generated electron–hole pairs is stronger than that of bare ZnO NRs. Impressively, the maximum photocurrent density of about 2.51 mA cm−2 at 1.23 V (vs. Ag/AgCl) was measured for the prepared ZnO–Ag2CrO4 photoelectrode with 8 SILAR cycles (denoted as ZnO–Ag2CrO4-8), which exhibited about 3-fold photo-enhancement in the current density as compared to bare ZnO NRs (0.87 mA cm−2) under similar conditions. The improvement in photoactivity was attributed to the ideal band gap and high absorption coefficient of the Ag2CrO4 particles, which resulted in improved solar light absorption properties. Furthermore, an appropriate annealing treatment was proven to be an efficient process to increase the crystallinity of Ag2CrO4 particles deposited on ZnO NRs, which improved the charge transport characteristics of the ZnO–Ag2CrO4-8 photoelectrode annealed at 200 °C and increased the performance of the photoelectrode. The results achieved in the present work present new insights for designing n–n heterojunction photoelectrodes for efficient and cost-effective PEC applications and solar-to-fuel energ

    Place, publisher, year, edition, pages
    Royal Society of Chemistry, 2019
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-155657 (URN)10.1039/C9RA00639G (DOI)000462646000051 ()2-s2.0-85062919263 (Scopus ID)
    Note

    Funding agencies: University of Mohaghegh Ardabili-Iran and Linkoping University-Sweden; AForsk [17-457

    Available from: 2019-03-22 Created: 2019-03-22 Last updated: 2020-03-18Bibliographically approved
    5. ZnO/Ag/Ag2WO4 photo-electrodes with plasmonic behavior for enhanced photoelectrochemical water oxidation
    Open this publication in new window or tab >>ZnO/Ag/Ag2WO4 photo-electrodes with plasmonic behavior for enhanced photoelectrochemical water oxidation
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    2019 (English)In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 9, no 15, p. 8271-8279Article in journal (Refereed) Published
    Abstract [en]

    Ag-based compounds are excellent co-catalyst that can enhance harvesting visible light and increase photo-generated charge carrier separation owing to its surface plasmon resonance (SPR) effect in photoelectrochemical (PEC) applications. However, the PEC performance of a ZnO/Ag/Ag2WO4 heterostructure with SPR behavior has not been fully studied so far. Here we report the preparation of a ZnO/Ag/Ag2WO4 photo-electrode with SPR behavior by a low temperature hydrothermal chemical growth method followed by a successive ionic layer adsorption and reaction (SILAR) method. The properties of the prepared samples were investigated by different characterization techniques, which confirm that Ag/Ag2WO4 was deposited on the ZnO NRs. The Ag2WO4/Ag/ZnO photo-electrode showed an enhancement in PEC performance compared to bare ZnO NRs. The observed enhancement is attributed to the red shift of the optical absorption spectrum of the Ag2WO4/Ag/ZnO to the visible region (>400 nm) and to the SPR effect of surface metallic silver (Ag0) particles from the Ag/Ag2WO4 that could generate electron–hole pairs under illumination of low energy visible sun light. Finally, we proposed the PEC mechanism of the Ag2WO4/Ag/ZnO photo-electrode with an energy band structure and possible electron–hole separation and transportation in the ZnO/Ag/Ag2WO4 heterostructure with SPR effect for water oxidation. ER

    Place, publisher, year, edition, pages
    Royal Society of Chemistry, 2019
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-155655 (URN)10.1039/C8RA10141H (DOI)000461445300016 ()
    Available from: 2019-03-22 Created: 2019-03-22 Last updated: 2020-03-18Bibliographically approved
  • Public defence: 2020-04-17 13:00 ACAS, A-Building, LinköpingOrder onlineBuy this publication >>
    Sylvander, Johanna
    Linköping University, Department of Management and Engineering, Business Administration. Linköping University, Faculty of Arts and Sciences.
    The influence of clients on the social identities within the audit profession2020Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The overall purpose of the thesis is to explore the meaning of professionalism and independence for the individuals within the audit arena. Professionalism is defined as the occupational values that guide auditors’ professional behaviour, and how independence is understood is assumed to be influenced by the social groups the auditors identify with. The audit arena consists of several social actors, i.e. the audit profession, audit firms, and auditors, as well as external constituencies of the profession, i.e. accountors and accountees. The audit profession both serves the public interest by quality-ensuring the information provided by the accountors to the accountees as well as conducts business in a state-sanctioned monopoly-like market. Appearing independent and professional is therefore critical for the profession as independence and professionalism is the basis of society’s trust in the profession and may particularly influence the profession’s ability to recruit and retain staff.

    The audit profession, audit firms, offices and audit teams are social groups which influence the values, attitudes, and behaviours of the auditors through the process of socialization into the profession and the audit firm. However, accountors (i.e. clients) and accountees (i.e. stakeholders such as investors) are also social actors, who may influence the values, attitudes, and behaviour of auditors, if auditors identify with these social actors. Exploring the social identities at ‘play’ within the audit arena enables us to more fully understand the values that guide professional work.

    The thesis empirically investigates the social identity audit arena through potential, current, and former audit employees’ perceptions of the audit arena, where the data is both qualitative (interviews) and quantitative (surveys) in nature. The empirical material provides both pre-socialized and post-socialized perspectives on the audit arena, where the bulk of the material stems from the pre-socialized perspective. The thesis suggests that there are two types of auditors, namely small client auditors and large client auditors, where the small client auditor group dominates the audit arena. The role of the small client auditor is described differently from the large (public) client auditor’s role. The small client auditor is perceived as a teacher who helps the clients run their businesses better, and avoid problems with tax authorities et cetera, making it necessary for the auditor to have a good and close relationship with the client in order to fulfil her/his role. The large client auditor is described more as having the ‘traditional’ guardians of the market role. Hence, it seems as the small client auditor is guided by other values and has a different understanding of independence compared to the large client auditor. However, the large client auditor is also perceived as having a counselling teacher role, indicating that some professional values are shared by small client and large client auditors.

    These different roles auditors are perceived to have, where independence and working for the public interest seem to mean different things, can influence how new audit employees perceive the profession. If employees expect to work as ‘large client auditors’, but instead experience work being guided by small client auditor values (or vice versa), it may influence the willingness to stay in the profession. These two roles are also a potential factor influencing the expectation gap, i.e. the gap between what society thinks the auditor does and what s/he does in practice. These two roles may therefore influence society’s image of the auditor, and where the profession may have issues in appearing independent in the relationship with small clients.

    List of papers
    1. Exploring Motivational Drivers of Audit Employees - A Study Focusing on Generation Y
    Open this publication in new window or tab >>Exploring Motivational Drivers of Audit Employees - A Study Focusing on Generation Y
    2018 (English)In: Journal of Accounting and Finance, ISSN 1823-4992, E-ISSN 2180-4192, Vol. 8, no 2, p. 89-105Article in journal (Refereed) Published
    Abstract [en]

    This study explores audit employee motivation and especially what motivates the new generation of auditemployees, Generation Y. A survey was distributed amongst Swedish audit employees, and the resultrevealed five categories of motivational drivers; intrinsic, social, material, status and well-being drivers.The results indicate that Generation Y is more motivated by social, material and status drivers incomparison to other generations. However, the results indicate that motivation changes over time,making it hard to distinguish between generational traits and experience.

    National Category
    Business Administration
    Identifiers
    urn:nbn:se:liu:diva-162213 (URN)
    Available from: 2019-11-24 Created: 2019-11-24 Last updated: 2020-03-02
    2. Exploring audit assistants decision to leave the audit profession
    Open this publication in new window or tab >>Exploring audit assistants decision to leave the audit profession
    2017 (English)In: Managerial Auditing Journal, ISSN 0268-6902, E-ISSN 1758-7735, Vol. 32, no 9, p. 879-898Article in journal (Refereed) Published
    Abstract [en]

    Purpose - The purpose of this paper is to explore why audit assistants leave the audit profession. By including both the perceptions held by audit assistants that left the audit profession and the perceptions of audit assistants still working in the audit profession, this study aims to explore how determinants of job satisfaction are associated with decisions to leave the audit profession. Design/methodology/approach - To explore the association between determinants of job satisfaction and decisions to leave, a survey was developed based on a literature review of determinants of job satisfaction. The survey was sent to both current and former Swedish audit assistants. The subsequent analysis was based on 231 complete surveys, of which 78 were from former audit assistants. Findings - The main finding of this study is that there is a negative association between the choice to leave the profession and audit assistants perceptions of the profession and between the choice to leave and work-life balance. Another finding was thatmet expectations and Big 4were found to be positively associated with career change. Originality/value - By approaching both current and former audit assistants, this study contributes to the literature on audit employee turnover by exploring determinants of actual career change, rather than turnover intentions. It also contributes by identifying and testing a variable not previously used as a determinant of job satisfaction, namely, perceptions of the audit profession.

    Place, publisher, year, edition, pages
    EMERALD GROUP PUBLISHING LTD, 2017
    Keywords
    Job satisfaction; Employee turnover; Audit assistants; Audit profession; Career change; Perceptions of the profession
    National Category
    Business Administration
    Identifiers
    urn:nbn:se:liu:diva-143383 (URN)10.1108/MAJ-05-2016-1381 (DOI)000415625100003 ()
    Available from: 2017-12-05 Created: 2017-12-05 Last updated: 2020-03-02
  • Public defence: 2020-04-23 13:15 Ada Lovelace, B-Building, LinköpingOrder onlineBuy this publication >>
    Roy, Biman
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Applications of Partial Polymorphisms in (Fine-Grained) Complexity of Constraint Satisfaction Problems2020Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this thesis we study the worst-case complexity ofconstraint satisfaction problems and some of its variants. We use methods from universal algebra: in particular, algebras of total functions and partial functions that are respectively known as clones and strong partial clones. The constraint satisfactionproblem parameterized by a set of relations Γ (CSP(Γ)) is the following problem: given a set of variables restricted by a set of constraints based on the relations Γ, is there an assignment to thevariables that satisfies all constraints? We refer to the set Γ as aconstraint language. The inverse CSPproblem over Γ (Inv-CSP(Γ)) asks the opposite: given a relation R, does there exist a CSP(Γ) instance with R as its set of models? When Γ is a Boolean language, then we use the term SAT(Γ) instead of CSP(Γ) and Inv-SAT(Γ) instead of Inv-CSP(Γ).

    Fine-grained complexity is an approach in which we zoom inside a complexity class and classify theproblems in it based on their worst-case time complexities. We start by investigating the fine-grained complexity of NP-complete CSP(Γ) problems. An NP-complete CSP(Γ) problem is said to be easier than an NP-complete CSP(∆) problem if the worst-case time complexity of CSP(Γ) is not higher thanthe worst-case time complexity of CSP(∆). We first analyze the NP-complete SAT problems that are easier than monotone 1-in-3-SAT (which can be represented by SAT(R) for a certain relation R), and find out that there exists a continuum of such problems. For this, we use the connection between constraint languages and strong partial clones and exploit the fact that CSP(Γ) is easier than CSP(∆) when the strong partial clone corresponding to  Γ contains the strong partial clone of ∆. An NP-complete CSP(Γ) problem is said to be the easiest with respect to a variable domain D if it is easier than any other NP-complete CSP(∆) problem of that domain. We show that for every finite domain there exists an easiest NP-complete problem for the ultraconservative CSP(Γ) problems. An ultraconservative CSP(Γ) is a special class of CSP problems where the constraint language containsall unary relations. We additionally show that no NP-complete CSP(Γ) problem can be solved insub-exponential time (i.e. in2^o(n) time where n is the number of variables) given that theexponentialtime hypothesisis true.

    Moving to classical complexity, we show that for any Boolean constraint language Γ, Inv-SAT(Γ) is either in P or it is coNP-complete. This is a generalization of an earlier dichotomy result, which was only known to be true for ultraconservative constraint languages. We show that Inv-SAT(Γ) is coNP-complete if and only if the clone corresponding to Γ contains essentially unary functions only. For arbitrary finite domains our results are not conclusive, but we manage to prove that theinversek-coloring problem is coNP-complete for each k>2. We exploit weak bases to prove many of theseresults. A weak base of a clone C is a constraint language that corresponds to the largest strong partia clone that contains C. It is known that for many decision problems X(Γ) that are parameterized bya constraint language Γ(such as Inv-SAT), there are strong connections between the complexity of X(Γ) and weak bases. This fact can be exploited to achieve general complexity results. The Boolean domain is well-suited for this approach since we have a fairly good understanding of Boolean weak bases. In the final result of this thesis, we investigate the relationships between the weak bases in the Boolean domain based on their strong partial clones and completely classify them according to the setinclusion. To avoid a tedious case analysis, we introduce a technique that allows us to discard a largenumber of cases from further investigation.

    List of papers
    1. A Preliminary Investigation of Satisfiability Problems NotHarder than 1-in-3-SAT
    Open this publication in new window or tab >>A Preliminary Investigation of Satisfiability Problems NotHarder than 1-in-3-SAT
    2016 (English)Conference paper, Published paper (Refereed)
    National Category
    Computer Sciences
    Identifiers
    urn:nbn:se:liu:diva-164152 (URN)
    Conference
    Proceedings of the 41st International Symposium on Mathematical Foundations of Computer Science (MFCS-2016)
    Available from: 2020-03-07 Created: 2020-03-07 Last updated: 2020-03-07
    2. On the Interval of Boolean Strong Partial ClonesContaining Only Projections as Total Operations
    Open this publication in new window or tab >>On the Interval of Boolean Strong Partial ClonesContaining Only Projections as Total Operations
    2017 (English)Conference paper, Published paper (Refereed)
    National Category
    Computer Sciences
    Identifiers
    urn:nbn:se:liu:diva-164153 (URN)
    Conference
    47th International Symposium on Multiple-Valued Logic (ISMVL-2017)
    Available from: 2020-03-07 Created: 2020-03-07 Last updated: 2020-03-07
    3. Time Complexity of Constraint Satisfaction via Universal Algebra
    Open this publication in new window or tab >>Time Complexity of Constraint Satisfaction via Universal Algebra
    2017 (English)Conference paper, Published paper (Refereed)
    National Category
    Computer Sciences
    Identifiers
    urn:nbn:se:liu:diva-164154 (URN)
    Conference
    42nd International Symposium on Mathematical Foundations of Computer Science (MFCS-2017)
    Available from: 2020-03-07 Created: 2020-03-07 Last updated: 2020-03-07
    4. A Dichotomy Theorem for the Inverse Satisfiability Problem
    Open this publication in new window or tab >>A Dichotomy Theorem for the Inverse Satisfiability Problem
    2018 (English)Conference paper, Published paper (Refereed)
    National Category
    Computer Sciences
    Identifiers
    urn:nbn:se:liu:diva-164155 (URN)
    Conference
    37th IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS-2017)
    Available from: 2020-03-07 Created: 2020-03-07 Last updated: 2020-03-07
    5. The Inclusion Structure of Boolean Weak Bases
    Open this publication in new window or tab >>The Inclusion Structure of Boolean Weak Bases
    2019 (English)In: 2019 IEEE 49TH INTERNATIONAL SYMPOSIUM ON MULTIPLE-VALUED LOGIC (ISMVL), IEEE , 2019, p. 31-36Conference paper, Published paper (Refereed)
    Abstract [en]

    Strong partial clones are composition closed sets of partial operations containing all partial projections, characterizable as partial polymorphisms of sets of relations Gamma (pPol(Gamma)). If C is a clone it is known that the set of all strong partial clones whose total component equals C, has a greatest element pPol(Gamma(w)), where Gamma(w) is called a weak base. Weak bases have seen applications in computer science due to their usefulness for proving complexity classifications for constraint satisfaction related problems. In this paper we completely describe the inclusion structure between pPol(Gamma(w)), pPol(Delta(w)) for all Boolean weak bases Gamma(w), and Delta(w.)

    Place, publisher, year, edition, pages
    IEEE, 2019
    Series
    International Symposium on Multiple-Valued Logic, ISSN 0195-623X
    National Category
    Computer Sciences
    Identifiers
    urn:nbn:se:liu:diva-160634 (URN)10.1109/ISMVL.2019.00014 (DOI)000484992100006 ()978-1-7281-0092-0 (ISBN)
    Conference
    49th IEEE International Symposium on Multiple-Valued Logic (ISMVL)
    Available from: 2019-10-11 Created: 2019-10-11 Last updated: 2020-03-07
  • Public defence: 2020-04-24 09:00
    Gutefeldt, Kerstin
    Linköping University, Department of Health, Medicine and Caring Sciences, Division of Diagnostics and Specialist Medicine. Region Östergötland, Heart and Medicine Center, Department of Endocrinology.
    Upper extremity impairments in type 1 diabetes in comparison to matched controls without diabetes: associations to the IGF-system, metabolic factors, disability and quality of life2020Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Compared with the general population, people with type 1 diabetes (T1D) more often exhibit pathological alterations in musculoskeletal tissue (impairments). Some of these impairments involve the upper extremities, i.e., the shoulders, hands, and fingers. Although present in diabetes, these complications are underdiagnosed and not actively searched for during routine clinical examinations. Furthermore, much is still unclear about these impairments, specifically regarding their etiology, risk factors, and consequences on daily life activities and quality of life. The growth hormone (GH)/insulinlike growth factor (IGF)-system is known to be affected in diabetes, but whether this is involved in upper extremity impairments (UEIs) is unclear. The aim of this thesis was to describe the prevalence of UEIs in patients with diabetes compared with controls. Furthermore, we aimed to search for risk factors of UEIs, and elucidate the impact of UEIs on daily life activities and health-related quality of life (HRQOL). We used two cohorts; the LedIG cohort (papers I–III), a large population-based study in which all patients with a long duration of T1D (>20 years), aged <67 years, living in the south-east region of Sweden were invited to participate, as well as matched controls without diabetes. This study was based on questionnaires as well as blood samples from the participants. The last paper (IV) included a smaller cohort (n=69) of patients with T1D, who both completed a questionnaire and were the subjects of a clinical examination.

    Paper I: The UEIs were common in diabetes, with a prevalence of up to 48%. Hand paresthesia was the most common impairment, followed by shoulder pain and stiffness. The prevalence of UEIs was 2–4 times higher in patients than in controls and was associated with more activity limitations. Risk factors were heterogeneous for the different UEIs and included female sex, increasing age, longer duration of diabetes, and poor glycemic control.

    Paper II: The GH-IGF-axis is important for the growth and function of musculoskeletal tissues. We examined differences in the IGF system between patients with T1D on subcutaneous insulin treatment and controls. We found lower levels of IGF-I and insulinlike growth factor-binding protein (IGFBP)-3 and higher levels of GH and IGFBP-1 in patients with T1D than in controls. The largest difference was found in IGFBP-1, and this probably reflected insulin deficiency. The IGF-I levels were increased with increasing insulin doses. However, even at very high insulin doses (>1 U/kg) the IGF-I Z-score was subnormal, indicating that IGF-I cannot be normalized by subcutaneous insulin treatment. Residual endogenous insulin secretion counteracted these alterations. Furthermore, we investigated possible relationships between UEIs and IGF-I, and found no association.

    Paper III: The HRQOL was lower in patients with T1D than in controls. Patients with shoulder impairments, hand paresthesia, and hand stiffness, but not finger impairments, had lower HRQOL scores than patients without these impairments. The patients with T1D showed a higher frequency of sick leave than controls, and a common reason for this was musculoskeletal impairments.

    Paper IV: In addition to the self-reported UEIs, the prevalence of UEIs was also investigated by clinical examination. Clinical UEIs were found in 65% of the participants, with shoulder test (hands against back), prayer sign test, and the Phalen’s and Tinel’s tests being most prevalent. We compared self-reported UEIs to clinical UEIs and found that self-reported impairments were associated with clinical examination. We also found that self-reported shoulder impairments, reduced hand strength, and previous surgery for carpal tunnel syndrome and trigger finger were associated with several other UEIs.

    In current diabetic care, there is no established routine to capture UEIs, as opposed to other known diabetes complications. We show that UEIs are more common in patients with T1D than in controls, and that they are related to impaired HRQOL and daily life activity limitations. Clinical routines including self-reported UEIs, e.g. shoulder stiffness and reduced hand strength, might be used to identify patients with UEIs in need of clinical investigation, enhanced preventive and therapeutic strategies, as well as rehabilitative interventions.

    List of papers
    1. Upper extremity impairments in type 1 diabetes with long duration: common problems with great impact on daily life
    Open this publication in new window or tab >>Upper extremity impairments in type 1 diabetes with long duration: common problems with great impact on daily life
    Show others...
    2019 (English)In: Disability and Rehabilitation, ISSN 0963-8288, E-ISSN 1464-5165, Vol. 41, no 6, p. 633-640Article in journal (Refereed) Published
    Abstract [en]

    PURPOSE: To investigate the prevalence, activity limitations and potential risk factors of upper extremity impairments in type 1 diabetes in comparison to controls.

    METHODS: In a cross-sectional population-based study in the southeast of Sweden, patients with type 1 diabetes <35 years at onset, duration ≥20 years, <67 years old and matched controls were invited to answer a questionnaire on upper extremity impairments and activity limitations and to take blood samples.

    RESULTS: Seven hundred and seventy-three patients (ages 50 ± 10 years, diabetes duration 35 ± 10 years) and 708 controls (ages 54 ± 9 years) were included. Shoulder pain and stiffness, hand paraesthesia and finger impairments were common in patients with a prevalence of 28-48%, which was 2-4-folds higher than in controls. Compared to controls, the patients had more bilateral impairments, often had coexistence of several upper extremity impairments, and in the presence of impairments, reported more pronounced activity limitations. Female gender (1.72 (1.066-2.272), p = 0.014), longer duration (1.046 (1.015-1.077), p = 0.003), higher body mass index (1.08 (1.017-1.147), p = 0.013) and HbA1c (1.029 (1.008-1.05), p = 0.007) were associated with upper extremity impairments.

    CONCLUSIONS: Compared to controls, patients with type 1 diabetes have a high prevalence of upper extremity impairments, often bilateral, which are strongly associated with activity limitations. Recognising these in clinical practise is crucial, and improved preventative, therapeutic and rehabilitative interventions are needed. Implications for rehabilitation Upper extremity impairments affecting the shoulder, hand and fingers are common in patients with type 1 diabetes, the prevalence being 2-4-fold higher compared to non-diabetic persons. Patients with diabetes type 1 with upper extremity impairments have more pronounced limitations in daily activities compared to controls with similar impairments. Recognising upper extremity impairments and activity limitations are important and improved preventive, therapeutic and rehabilitation methods are needed.

    Place, publisher, year, edition, pages
    Taylor & Francis, 2019
    Keywords
    Dupuytren’s disease, Type 1 diabetes, carpal tunnel syndrome, frozen shoulder, trigger finger disorder
    National Category
    Endocrinology and Diabetes
    Identifiers
    urn:nbn:se:liu:diva-144020 (URN)10.1080/09638288.2017.1397202 (DOI)000461521100002 ()29105514 (PubMedID)2-s2.0-85033477270 (Scopus ID)
    Note

    Funding agencies: Medical Research Council of Southeast Sweden (FORSS); County council of Region Ostergotland, Sweden; Stiftelseforvaltningen of Region Ostergotland, Sweden

    Available from: 2018-01-03 Created: 2018-01-03 Last updated: 2020-03-24Bibliographically approved
    2. Dysregulated growth hormone-insulin-like growth factor-1 axis in adult type 1 diabetes with long duration
    Open this publication in new window or tab >>Dysregulated growth hormone-insulin-like growth factor-1 axis in adult type 1 diabetes with long duration
    Show others...
    2018 (English)In: Clinical Endocrinology, ISSN 0300-0664, E-ISSN 1365-2265, Vol. 89, no 4, p. 424-430Article in journal (Refereed) Published
    Abstract [en]

    ContextIn type 1 diabetes (T1D), dysregulation of the GH-IGF-1 axis has been reported. Whether this is related to upper extremity impairments (UEI) is unknown. ObjectiveExamine differences in GH-IGF-1 axis between T1D on subcutaneous insulin treatment and matched controls without diabetes and possible associations between GH-IGF-1 axis and UEI. DesignCross-sectional population-based study. Patients with T1D, onset amp;lt;35years, duration 20years, amp;lt;67years old and controls were invited to answer questionnaires and take blood samples. SubjectsA total of 605 patients with T1D and 533 controls accepted to participate. OutcomesFasting levels of IGF-1, IGF-1 Z-score, IGFBP-1, IGFBP-3, C-peptide, GH and UEI. ResultsPatients with T1D had lower IGF-1 and IGFBP-3 and higher IGFBP-1 and GH than controls. The difference in IGF-1 persisted with age. Insulin dose was associated with increasing IGF-1 Z-score but even at a very high insulin dose (amp;gt;1U/kg) IGF-1 Z-score was subnormal compared to controls. IGF-1 Z-score was unaffected by glycaemic control (HbA1c) but increased with residual insulin secretion, (C-peptide 1-99 pmol/L). IGFBP-1 was associated with fasting blood glucose, negatively in controls and positively in patients with T1D probably reflecting insulin resistance and insulin deficiency, respectively. There was no association between lower IGF-1 Z-score and UEI in T1D. ConclusionIn adult T1D with fair glycaemic control, the GH-IGF-1 axis is dysregulated exhibiting GH resistance, low IGF-1 and elevated IGFBP-1. Subcutaneous insulin cannot normalize these changes while endogenous insulin secretion has marked effects on IGF-1 pointing to a role of portal insulin.

    Place, publisher, year, edition, pages
    WILEY, 2018
    Keywords
    GH; insulin-like growth factor-1; insulin-like growth factor-binding protein-1; insulin; type 1 diabetes; upper extremity impairments
    National Category
    Endocrinology and Diabetes
    Identifiers
    urn:nbn:se:liu:diva-151773 (URN)10.1111/cen.13810 (DOI)000444539600006 ()29989677 (PubMedID)
    Note

    Funding Agencies|Medical Research Council of Southeast Sweden FORSS; County council and Stiftelseforvaltningen of Region Ostergotland, Sweden

    Available from: 2018-10-08 Created: 2018-10-08 Last updated: 2020-03-24
    3. Low health-related quality of life is strongly linked to upper extremity impairments in type 1 diabetes with a long duration
    Open this publication in new window or tab >>Low health-related quality of life is strongly linked to upper extremity impairments in type 1 diabetes with a long duration
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    2020 (English)In: Disability and Rehabilitation, ISSN 0963-8288, E-ISSN 1464-5165Article in journal (Refereed) Epub ahead of print
    Abstract [en]

    Purpose: To compare health-related quality of life (HRQOL) in type 1 diabetes and non-diabetic controls and possible links to upper extremity impairments (UEIs). Prevalence of sick-leave and causes were investigated.

    Materials and methods: This Swedish population-based case-control study included type 1 diabetes patients <67 years old and with a diabetes duration ≥20 years. Participants completed a postal questionnaire including Short Form 36, and questions regarding UEIs, and sick-leave.

    Results: In total, 773 patients, aged 50 ± 10 years (diabetes duration 35 ± 10 years), and 708 non-diabetic controls, aged 54 ± 9 years, completed the study. Patients reported significantly lower HRQOL compared with controls. The difference was greatest for general health, vitality, and bodily pain. Patients with shoulder or hand but not finger impairments scored significantly lower than asymptomatic patients. The prevalence of sick leave was higher in patients vs. controls (23% vs. 9%, p < 0.001), and nearly half cited impairments from back, muscles, or joints as the main reason.

    Conclusions: Health-related quality of life is lower in type 1 diabetes than controls and in patients with shoulder and hand impairments than in asymptomatic. Musculoskeletal impairments (back/muscle/joints) have impact on work ability. Identification of UEIs is important for initiating preventative-, therapeutic-, and rehabilitative interventions.

    • Implications for rehabilitation
    • Upper extremity impairments (UEIs) that are common in type 1 diabetes, and associated with reduced health-related quality of life, should preferably be screened for on a regular basis along with other known diabetes complications.

    • Early identification of UEIs is important to improve health by initiating preventive as well as therapeutic multi-professional rehabilitative interventions.

    • Sick leave is higher in type 1 diabetes than in controls. Musculoskeletal impairments, including the back, muscles, and joints, are a common cause for sick leave warranting further studies.

    Place, publisher, year, edition, pages
    Taylor & Francis, 2020
    Keywords
    Quality of life; type 1 diabetes; upper extremity impairments; work ability; disability
    National Category
    General Practice
    Identifiers
    urn:nbn:se:liu:diva-163405 (URN)10.1080/09638288.2019.1705924 (DOI)000505880400001 ()31906725 (PubMedID)2-s2.0-85078623672 (Scopus ID)
    Note

    Funding Agencies|Medical Research Council South-east Sweden (FORSS); County Council; Stiftelseforvaltningen of Region Ostergotland, Sweden

    Available from: 2020-02-04 Created: 2020-02-04 Last updated: 2020-03-24Bibliographically approved
    4. Clinical Examination and Self-Reported Upper Extremity Impairments in Patients with Long-Standing Type 1 Diabetes Mellitus
    Open this publication in new window or tab >>Clinical Examination and Self-Reported Upper Extremity Impairments in Patients with Long-Standing Type 1 Diabetes Mellitus
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    2020 (English)In: Journal of Diabetes Research, Vol. 2020Article in journal (Refereed) Published
    Abstract [en]

    Aim. The aims of the current study were (1) to determine the prevalence of upper extremity impairments (UEIs) in patients with type 1 diabetes by clinical investigation; (2) to investigate if self-reported impairments were concordant with clinical findings and if key questions could be identified; and (3) to investigate if answers to our self-reported questionnaire regarding UEIs are reliable. Methods. Patients with type 1 diabetes were invited to participate in a cross-sectional study of clinical and self-reported (12 items) UEIs in adjunction to ordinary scheduled clinical visit. Before the visit, a questionnaire on UEIs was filled in twice (test-retest) followed by clinical testing at the planned visit. Results. In total, 69 patients aged and with diabetes duration were included in the study. In the clinical examination, two-thirds (65%) of the patients showed one or more UEI, with failure to perform hand against back as the most common clinical finding (40%) followed by positive Phalen’s test (27%), Tinel’s test (26%), and Prayer’s sign (24%). UEIs observed by clinical examination were often bilateral, and multiple impairments often coexisted. Self-reported shoulder stiffness was associated with impaired shoulder mobility and with Prayer’s sign. Self-reported reduced hand strength was associated to lower grip force, Prayer’s sign, trigger finger, fibrosis string structures, and reduced thenar strength as well as reduced shoulder mobility. In addition, self-reporting previous surgery of carpal tunnel and trigger finger was associated with several clinical UEIs including shoulder, hand, and finger. The test-retest of the questionnaire showed a high agreement of 80-98% for reported shoulder, hand, and finger impairments. Conclusion. UEIs are common in type 1 diabetes. Self-reported shoulder stiffness and reduced hand strength might be used to capture patients with UEIs in need of clinical investigation and enhanced preventive and therapeutic strategies, as well as rehabilitative interventions.

    National Category
    Physiotherapy
    Identifiers
    urn:nbn:se:liu:diva-164549 (URN)10.1155/2020/4172635 (DOI)
    Available from: 2020-03-24 Created: 2020-03-24 Last updated: 2020-03-24
  • Public defence: 2020-04-24 10:15 Planck, F Building, LinköpingOrder onlineBuy this publication >>
    Jönsson, Johan
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Electronic transitions and correlation effects: From pure elements to complex materials2020Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Macroscopic properties of real materials, such as conductivity, magneticproperties, crystal structure parameters, etc. are closely related or evendetermined by the configuration of their electrons, characterized by electronicstructure. By changing the conditions, e.g, pressure, temperature, magnetic/electric field, chemical doping, etc. one can modify the electronic structure ofsolids and therefore induce a phase transition(s) between different electronic andmagnetic states. One famous example is a Mott metal-to-insulator phase transition,at which a material undergoes a significant, often many orders of magnitude, changeof conductivity caused by the interplay between itineracy and localization of thecarriers.

    Electronic topological transitions (ETT) involvechanges in the topology of a metal's Fermi surface. This thesis investigates theeffect of such electronic transitions in various materials, ranging from pureelements to complex compounds.

    To describe the interplay between electronic transitionsand properties of real materials,different state-of-the-art computational methods are used. The densityfunctional theory(DFT), as well as the DFT + U method, is used to calculatestructural properties. The validity of recently introduced exchange-correlationfunctionals, such as the strongly constrained and appropriately normed (SCAN)functional, is also assessed for magnetic elements. In order toinclude dynamical effects of electron interactions we use the DFT + dynamical meanfield theory (DFT + DMFT) method.

    Experiments in hcp-Os have reported peculiarities in the ratio betweenlattice parameters at high pressure. Previous calculations have suggested these transitions maybe related to ETTs and even crossings of core levels at ultra high pressure. Inthis thesis it is shownthat the crossing of core levels is a general feature of heavy transitionmetals. Experiments have therefore been performed to look for indications ofthis transition in Ir using X-ray absorption spectroscopy. In NiO, strongrepulsion between electrons leads to a Mott insulating state at ambientconditions. It has long been predicted that high pressure will lead to aninsulator-to-metal transition. This has been suggested to be accompanied by aloss of magnetic order, and a structural phase transition. In collaboration withexperimentalists we look for thistransition by investigating the X-ray absorption spectra as well as themagnetic hyperfine field. We find no evidence of a Mott transition up to 280GPa. In the Mott insulator TiPO4, application of external pressure has beensuggested to lead to a spin-Peierls transition at room temperature. Weinvestigate the dimerisation and the magnetic structure of TiPO4 at high pressure.As pressure is increased further, TiPO4 goes through a metal to insulatortransition before an eventual crystallographic phase transition. Remarkably, thenew high pressure phases are found to be insulators; the Mott insulating stateis restored.

    MAX phases are layered materials that combinemetallic and ceramic properties and feature layers of M-metal and X-C or N atomsinterconnected by A-group atoms. Magnetic MAX-phases with their low dimensionalmagnetism are promising candidates for applications in e.g., spintronics.The validity of various theoretical approaches are discussed in connection tothe magnetic MAX-phase Mn2GaC. Using DFT and DFT + DMFT we consider the hightemperature paramagnetic state, and whether the magnetic moments are formed bylocalized or itinerant electrons.

    List of papers
    1. Assessing the SCAN functional for itinerant electron ferromagnets
    Open this publication in new window or tab >>Assessing the SCAN functional for itinerant electron ferromagnets
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    2018 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 98, no 9, article id 094413Article in journal (Refereed) Published
    Abstract [en]

    Density functional theory is a standard model for condensed-matter theory and computational material science. The accuracy of density functional theory is limited by the accuracy of the employed approximation to the exchange-correlation functional. Recently, the so-called strongly constrained appropriately normed (SCAN) [Sun, Ruzsinszky, and Perdew, Phys. Rev. Lett. 115, 036402 (2015)] functional has received a lot of attention due to promising results for covalent, metallic, ionic, as well as hydrogen- and van der Waals-bonded systems alike. In this work, we focus on assessing the performance of the SCAN functional for itinerant magnets by calculating basic structural and magnetic properties of the transition metals Fe, Co, and Ni. We find that although structural properties of bcc-Fe seem to be in good agreement with experiment, SCAN performs worse than standard local and semilocal functionals for fcc-Ni and hcp-Co. In all three cases, the magnetic moment is significantly overestimated by SCAN, and the 3d states are shifted to lower energies, as compared to experiments.

    Place, publisher, year, edition, pages
    AMER PHYSICAL SOC, 2018
    National Category
    Theoretical Chemistry
    Identifiers
    urn:nbn:se:liu:diva-151640 (URN)10.1103/PhysRevB.98.094413 (DOI)000444348500004 ()
    Note

    Funding Agencies|Swedish e-Science Research Centre (SeRC); Swedish Research Council (VR) through the International Career Grant [20146336]; Marie Sklodowska CurieActions, Cofund, Project [INCA 600398]; Swedish Foundation for Strategic Research (SSF) through the Future Research Leaders 6 program; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009-00971]; competence center FunMat-II - Vinnova [201605156]; Russian Science Foundation [18-12-00492]

    Available from: 2018-09-27 Created: 2018-09-27 Last updated: 2020-03-17
    2. Pressure-induced crossing of the core levels in 5d metals
    Open this publication in new window or tab >>Pressure-induced crossing of the core levels in 5d metals
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    2016 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 93, no 20, p. 205150-Article in journal (Refereed) Published
    Abstract [en]

    A pressure-induced interaction between core electrons, the core-level crossing (CLC) transition, has been observed in hcp Os at P approximate to 400 GPa [L. Dubrovinsky et al., Nature (London) 525, 226 (2015)]. By carrying out a systematic theoretical study for all metals of the 5d series (Hf, Ta, W, Re, Os, Ir, Pt, Au) we have found that the CLC transition is a general effect for this series of metals. While in Pt it occurs at approximate to 1500 GPa, at a pressure substantially higher than in Os, in Ir it occurs already at 80 GPa. Moreover, we predict that in Re the CLC transition may take place already at ambient pressure. We explain the effect of the CLC and analyze the shift of the transition pressure across the series within the Thomas-Fermi model. In particular, we show that the effect has many common features with the atomic collapse in rare-earth elements.

    Place, publisher, year, edition, pages
    AMER PHYSICAL SOC, 2016
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-129490 (URN)10.1103/PhysRevB.93.205150 (DOI)000376638700004 ()
    Note

    Funding Agencies|Swedish Government Strategic Research Area Grant Swedish e-Science Research Centre (SeRC); Ministry of Education and Science of the Russian Federation in the framework of Increase Competitiveness Program of MISiS; Swedish Foundation for Strategic Research (SSF) program SRL [10-0026]; Swedish Research Council (VR) [2015-04391]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009 00971]; Ministry of Education and Science of the Russian Federation [14.Y26.31.0005]; German Research Foundation (DFG); Federal Ministry of Education and Research (BMBF), Germany; DFG [DU 954-8/1]; BMBF (PT-DESY) [5K13WC3, O5K2013, 2]; Act 211 Government of the Russian Federation [02.A03.21.0006]; Knut and Alice Wallenberg Foundation [2012.0083, 2014-2019]

    Available from: 2016-06-21 Created: 2016-06-20 Last updated: 2020-03-17
    3. Topological transitions of the Fermi surface of osmium under pressure: an LDA plus DMFT study
    Open this publication in new window or tab >>Topological transitions of the Fermi surface of osmium under pressure: an LDA plus DMFT study
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    2017 (English)In: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 19, article id 033020Article in journal (Refereed) Published
    Abstract [en]

    The influence of pressure on the electronic structure of Os has attracted substantial attention recently due to reports on isostructural electronic transitions in this metal. Here, we theoretically investigate the Fermi surface of Os from ambient to high pressure, using density functional theory combined with dynamical mean field theory. Weprovide a detailed discussion of the calculated Fermi surface and its dependence on the level of theory used for the treatment of the electron-electron interactions. Although we confirm that Os can be classified as weakly correlated metal, the inclusion of local quantum fluctuations between 5d electrons beyond the local density approximation explains the most recent experimental reports regarding the occurrence of electronic topological transitions in Os.

    Place, publisher, year, edition, pages
    IOP PUBLISHING LTD, 2017
    Keywords
    electronic topological transitions; strong correlations; Fermi surfaces
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-136604 (URN)10.1088/1367-2630/aa5f8e (DOI)000398666100004 ()
    Note

    Funding Agencies|Swedish Foundation for Strategic Research SSF (SRL) [10-0026]; Swedish Research Council (VR) grant [2015-04391]; Knut and Alice Wallenberg Foundation [2014-2019]; Swedish Government Strategic Research Area SeRC; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFOMatLiU) [2009 00971]; Ministry of Education and Science of the Russian Federation of NUST MISIS [K2-2016-013]; PHD DALEN Project [26228RM]; Swedish National Infrastructure for Computing (SNIC)

    Available from: 2017-04-21 Created: 2017-04-21 Last updated: 2020-03-17
    4. Phase stability and electronic structure of iridium metal at the megabar range
    Open this publication in new window or tab >>Phase stability and electronic structure of iridium metal at the megabar range
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    2019 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, article id 8940Article in journal (Refereed) Published
    Abstract [en]

    The 5d transition metals have attracted specific interest for high-pressure studies due to their extraordinary stability and intriguing electronic properties. In particular, iridium metal has been proposed to exhibit a recently discovered pressure-induced electronic transition, the so-called core-level crossing transition at the lowest pressure among all the 5d transition metals. Here, we report an experimental structural characterization of iridium by x-ray probes sensitive to both long- and short-range order in matter. Synchrotron-based powder x-ray diffraction results highlight a large stability range (up to 1.4 Mbar) of the low-pressure phase. The compressibility behaviour was characterized by an accurate determination of the pressure-volume equation of state, with a bulk modulus of 339(3) GPa and its derivative of 5.3(1). X-ray absorption spectroscopy, which probes the local structure and the empty density of electronic states above the Fermi level, was also utilized. The remarkable agreement observed between experimental and calculated spectra validates the reliability of theoretical predictions of the pressure dependence of the electronic structure of iridium in the studied interval of compressions.

    Place, publisher, year, edition, pages
    Nature Publishing Group, 2019
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-158862 (URN)10.1038/s41598-019-45401-x (DOI)000472137700036 ()31222067 (PubMedID)2-s2.0-85067628529 (Scopus ID)
    Note

    Funding Agencies|Spanish Ministry of Science, Innovation and Universities; Spanish Research Agency (AEI); European Fund for Regional Development (FEDER) [MAT2016-75586-C4-1/2-P]; Generalitat Valenciana [Prometeo/2018/123]; Spanish Mineco Project [FIS2017-83295-P]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009 00971]; Ministry of Science and High Education of the Russian Federation [K2-2019-001]; "Juan de la Cierva" fellowship [FJCI-2016-27921]; "Ramon y Cajal" fellowship [RYC-2015-17482]

    Available from: 2019-07-16 Created: 2019-07-16 Last updated: 2020-03-19Bibliographically approved
    5. Magnetic interactions in NiO at ultrahigh pressure
    Open this publication in new window or tab >>Magnetic interactions in NiO at ultrahigh pressure
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    2016 (English)In: PHYSICAL REVIEW B, ISSN 2469-9950, Vol. 93, no 20, p. 201110-Article in journal (Refereed) Published
    Abstract [en]

    Magnetic properties of NiO have been studied in the multimegabar pressure range by nuclear forward scattering of synchrotron radiation using the 67.4 keV Mossbauer transition of Ni-61. The observed magnetic hyperfine splitting confirms the antiferromagnetic state of NiO up to 280 GPa, the highest pressure where magnetism has been observed so far, in any material. Remarkably, the hyperfine field increases from 8.47 T at ambient pressure to similar to 24 T at the highest pressure, ruling out the possibility of a magnetic collapse. A joint x-ray diffraction and extended x-ray-absorption fine structure investigation reveals that NiO remains in a distorted sodium chloride structure in the entire studied pressure range. Ab initio calculations support the experimental observations, and further indicate a complete absence of Mott transition in NiO up to at least 280 GPa.

    Place, publisher, year, edition, pages
    AMER PHYSICAL SOC, 2016
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-129492 (URN)10.1103/PhysRevB.93.201110 (DOI)000376638400001 ()
    Note

    Funding Agencies|National Science Foundation-Earth Sciences [EAR-1128799]; Department of Energy-GeoSciences [DE-FG02-94ER14466]; DOE Office of Science [DE-AC02-06CH11357]; Helmholtz Association; Materials Sciences and Engineering Division, Office of Basic Energy Sciences, U.S. Department of Energy; Swedish Government Strategic Research Area Grants Swedish e-Science Research Center (SeRC) and in Materials Science on Functional Materials at Linkoping University [2009 00971]; Knut and Alice Wallenbergs Foundation project Strong Field Physics and New States of Matter; Swedish Foundation for Strategic Research program SRL Grant [10-0026]; Swedish Research Council (VR) [2015-04391]; Grant of Ministry of Education and Science of the Russian Federation [14.Y26.31.0005]; Tomsk State University Academic D.I. Mendeleev Fund Program

    Available from: 2016-06-20 Created: 2016-06-20 Last updated: 2020-03-17
    6. Inverse pressure-induced Mott transition in TiPO4
    Open this publication in new window or tab >>Inverse pressure-induced Mott transition in TiPO4
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    2019 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 99, no 24, article id 245132Article in journal (Refereed) Published
    Abstract [en]

    TiPO4 shows interesting structural and magnetic properties as temperature and pressure are varied, such as a spin-Peierls phase transition and the development of incommensurate modulations of the lattice. Recently, high-pressure experiments for TiPO4 reported two structural phases appearing at high pressures, the so-called phases IV and V [M. Bykov et al., Angew. Chem. Int. Ed. 55, 15053 (2016).]. The latter was shown to include the first example of fivefold O-coordinated P atoms in an inorganic phosphate compound. In this work, we characterize the electronic structure and other physical properties of these phases by means of ab initio calculations and investigate the structural transition. We find that the appearance of phases IV and V coincides with a collapse of the Mott insulating gap and quenching of magnetism in phase III as pressure is applied. Remarkably, our calculations show that in the high-pressure phase V, these features reappear, leading to an antiferromagnetic Mott insulating phase, with robust local moments.

    Place, publisher, year, edition, pages
    AMER PHYSICAL SOC, 2019
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-158863 (URN)10.1103/PhysRevB.99.245132 (DOI)000471984200002 ()
    Note

    Funding Agencies|Knut and Alice Wallenberg Foundation [KAW-2013.0020]; Swedish e-Science Research Centre (SeRC); Swedish Research Council (VR) [2015-04391]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009 00971]; Russian Science Foundation [18-12-00492]

    Available from: 2019-07-16 Created: 2019-07-16 Last updated: 2020-03-17
  • Public defence: 2020-04-24 10:15 ACAS, A-Building, LinköpingOrder onlineBuy this publication >>
    Johansson, Henrik
    Linköping University, Department of Management and Engineering, Logistics & Quality Management. Linköping University, Faculty of Science & Engineering.
    Customer Benefits in City Logistics: Towards Viable Urban Consolidation Centres2020Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Urban Consolidation Centre (UCC) is a city logistics initiative that has the potential to increase the efficiency of urban freight delivery systems while reducing negative environmental and social effects caused by freight vehicles. One important issue that have hindered longevity of this initiative is its viability, both the financial viability and acceptance from affected stakeholders (also called UCC customers). The UCC customers in focus in this thesis are receivers of goods and municipalities. To satisfy both types of stakeholders, their requests and, in particular, the benefits they can gain from using UCCs need to be studied. The types of benefits to be given priority differ between the stakeholders, where municipalities strive towards more societal benefits, and the main goals of receivers are an increase in efficiency and financial sustainability. In response, the purpose of this thesis is to deepen the understanding of benefits for customers of UCCs, with a particular focus on customer needs and benefits that UCCs can provide.

    This thesis consists of five appended papers, each of which uses a different methodology. The methodologies applied in the papers include a multiple interview study of five UCCs, a surveybased interview study of retail stores, and a case study of an operating UCC. Regarding customer needs, this thesis takes the customer perspective, in order to identify needs that UCCs can meet. The results presented in this thesis also highlight the importance for UCCs to give priority to meeting customer needs that stem from some type of problem. Regarding benefits that UCCs can provide, the thesis suggests how different types of benefits can be distinguished. This can give guidance to UCC operators regarding which benefits should be given priority in communication with UCC customers. However, the results highlight that it is also important to understand the situation of the customer to be able to communicate the most relevant benefits that UCCs can provide. Furthermore, the results illustrate different improvement areas that can affect the benefits for UCC customers. These identified areas are: improved understanding by both UCCs and its customers of each other’s operation, communication, developing a more holistic view for UCC customers, and developing new UCC services to match customer needs.

    The results provide a foundation for customer needs that UCCs can meet, and the benefits that UCCs can provide. This foundation can be important for UCC customers to gain a better understanding of what a UCC is and how it can affect their operation, something that this thesis contributes towards. It can also assist initiators of UCCs to determine which customer needs they should focus on. Lastly, the results and contribution also address the potential role of municipalities, and it is argued that their role should change from a more supportive role to that of a paying UCC customer. All of these aspects can increase the probability that a UCC, when established becomes viable.

    List of papers
    1. Urban consolidation centre - a literature review, categorisation, and a future research agenda
    Open this publication in new window or tab >>Urban consolidation centre - a literature review, categorisation, and a future research agenda
    2018 (English)In: International Journal of Physical Distribution & Logistics Management, ISSN 0960-0035, E-ISSN 1758-664X, Vol. 48, no 8, p. 745-764Article, review/survey (Refereed) Published
    Abstract [en]

    Purpose Urban consolidation centre (UCC) is a popular initiative targeting the challenge of negative environmental and social impacts from freight transports in cities. Despite this, UCC often fails in practice, which indicates a knowledge gap. Furthermore, research within the field can be described as fragmented, transdisciplinary and fast growing. The purpose of this paper is to provide an overview of the field by describing dominant categories and themes within the area, identify gaps in order to propose a future research agenda, and provide insights into the needs of practitioners. Design/methodology/approach A systematic literature review (SLR) targeting journal articles based on UCCs has been constructed with a supplementary snowball approach. A content analysis was performed to categorise themes in the research on UCCs and to identify research gaps, both within and outside the categories identified. Findings Despite substantial research on UCC, very little research ends up in academic journals. In all, 56 articles address UCC. The most common topics were the role of stakeholders, design of distribution structures and transport resources, environmental and social consideration, and economic considerations. Much focus is directed towards finding optimal solutions and designs for potential initiatives with very little, if any, consideration to financial viability or the management of the UCC initiative. Research limitations/implications This research points out existing gaps in the literature and proposes a future research agenda with UCCs as the focus. For example, although environmental and social arguments are often applied to justify the implementation of UCCs, few studies measure or evaluate their impact. Another important research gap is the economical consideration, both how to generate revenue and how to consider economies of scale. Practical implications The practical contribution of most studies is directed towards municipalities. Few findings are presented in a way to support companies. Additionally, by bridging the gaps related to how stakeholders can collaborate and describe what is happening in a UCC, practitioners can use such information as guidelines. Originality/value The results provide a research agenda for the fragmented research targeting UCCs, supporting the viability of future initiatives.

    Place, publisher, year, edition, pages
    EMERALD GROUP PUBLISHING LTD, 2018
    Keywords
    Content analysis; City logistics; Urban freight; Urban consolidation centre; Structural literature review
    National Category
    Business Administration
    Identifiers
    urn:nbn:se:liu:diva-151808 (URN)10.1108/IJPDLM-01-2017-0050 (DOI)000444391000002 ()
    Note

    Funding Agencies|Swedish Energy Agency

    Available from: 2018-10-04 Created: 2018-10-04 Last updated: 2020-03-20
    2. Critical factors for viable business models for urban consolidation centres
    Open this publication in new window or tab >>Critical factors for viable business models for urban consolidation centres
    2017 (English)In: Research in Transportation Economics, ISSN 0739-8859, E-ISSN 1875-7979, Vol. 64, p. 36-47Article in journal (Refereed) Published
    Abstract [en]

    Abstract Although urban consolidation centres (UCC) worldwide have improved urban freight distribution and reduced externalities, other UCC initiatives have not materialised due to problems such as for example, business model limitations. All the same, researchers have rarely described business model components relevant to city logistics. In response, the purpose of this article is to analyse critical factors for viable business models of city logistics initiatives involving UCCs. Following an extensive literature review and multiple-case study of five initiatives with UCCs, we identified seven critical factors of viable city logistics business models: the ability to scale up and down the UCC solution; an ability to continuously develop and adapt to a dynamic environment; the important entrepreneurial role of the initiator as well; the acknowledgment of society; ability to innovate new services; logistics and supply chain management competence; and the ability to take full advantage of advanced IT. All seven factors describe continuously redeveloped business models seeking to seize new and unexpected opportunities, yet also indicate that city logistics systems require local authorities and municipalities to act as initiators, enablers, and customers. The models also underscore differences between purely commercial and purely municipal city logistics initiatives.

    Place, publisher, year, edition, pages
    Elsevier, 2017
    Keywords
    Urban logistics, Business models, Critical factors, Urban consolidation centres
    National Category
    Transport Systems and Logistics
    Identifiers
    urn:nbn:se:liu:diva-144226 (URN)10.1016/j.retrec.2017.09.009 (DOI)
    Funder
    VINNOVA
    Available from: 2018-01-11 Created: 2018-01-11 Last updated: 2020-03-20
    3. Urban consolidation centres: retail stores demands for UCC services
    Open this publication in new window or tab >>Urban consolidation centres: retail stores demands for UCC services
    2017 (English)In: International Journal of Physical Distribution & Logistics Management, ISSN 0960-0035, E-ISSN 1758-664X, Vol. 47, no 7, p. 646-662Article in journal (Refereed) Published
    Abstract [en]

    Purpose - Urban consolidation centres (UCCs) are often conceived to improve services in retail stores and potentially reduce costs. However, few studies have examined how retail stores perceive the services a UCC could provide. The purpose of this paper is to explore retail stores potential demands for different services that a UCC could provide in order to foster the development and implementation of UCC solutions aimed towards more economically feasible business models. Design/methodology/approach - Structured interviews were conducted with employees at 72 retail stores. Qualitative, as well as quantitative analyses, were conducted to identify the potential demands of the retail stores. Findings - The authors have provided arguments why retail stores might be interested in UCC services, and thereby potentially pay for them. Improved customer service to stores customers might not be a valid argument. The authors point to the cost aspect: stores expend resources that a UCC could provide in a more cost-efficient manner. Research limitations/implications - The findings contradict previous studies to some extent, as it indicates that a UCC may actually not enhance customer service in retail stores. Instead, the findings point to the importance of considering the potential advantages according to economies of scale that are facilitated by UCC services. Practical implications - Taking the perspective of the stores is important in order to identify arguments for why they should pay for the services provided by a UCC. Social implications - Financially viable UCC solutions are needed in order for the initiatives to be maintained and thereby provide a long-term decrease in the environmental and social footprints caused by urban freight. Originality/value - This study answers the call for research addressing retailers perspective in urban logistics, as it takes a demand-driven perspective of the development of UCC services. Furthermore, by highlighting services requested by retail stores, it can guide the financing of UCC initiatives, an aspect that has been lacking.

    Place, publisher, year, edition, pages
    EMERALD GROUP PUBLISHING LTD, 2017
    Keywords
    Customer service; Business model; Urban freight; City logistics; Receivers; Urban consolidation centre; Urban distribution
    National Category
    Business Administration
    Identifiers
    urn:nbn:se:liu:diva-140529 (URN)10.1108/IJPDLM-02-2017-0114 (DOI)000407286000005 ()
    Conference
    Annual Nordic Logistics and SCM Researchers Conference (NOFOMA)
    Note

    Funding Agencies|VINNOVA; Swedens Innovation Agency

    Available from: 2017-09-11 Created: 2017-09-11 Last updated: 2020-03-20
    4. Designing a business model for redistribution of surplus food
    Open this publication in new window or tab >>Designing a business model for redistribution of surplus food
    2018 (English)Conference paper, Published paper (Refereed)
    National Category
    Transport Systems and Logistics
    Identifiers
    urn:nbn:se:liu:diva-148837 (URN)
    Conference
    NoFoMa 2018, Kolding, Denmark, 13-15 June, 2018
    Funder
    VINNOVA, 2017-03156
    Available from: 2018-06-20 Created: 2018-06-20 Last updated: 2020-03-20Bibliographically approved