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  • 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. Linköping University, Faculty of Medicine and Health Sciences. 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
    Show others...
    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
    Show others...
    2020 (English)In: Journal of Diabetes Research, ISSN 2314-6745, E-ISSN 2314-6753, Journal of Diabetes Research, Vol. 2020, article id 4172635Article 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.

    Place, publisher, year, edition, pages
    Hindawi Publishing Corporation, 2020
    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: 2020-03-31Bibliographically approved
  • 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
  • Public defence: 2020-04-30 13:15 I:101, I-Building, LinköpingOrder onlineBuy this publication >>
    Palmqvist, Lisa
    Linköping University, Department of Behavioural Sciences and Learning, Disability Research. Linköping University, Faculty of Arts and Sciences.
    Time to Plan: How to support everyday planning in adolescents with intellectual disability2020Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Children and adolescents with intellectual disability (ID) have difficulties in executive functioning and when coping with everyday planning tasks. However, the literature cannot explain whether individuals with ID perform according to their developmental level or not. The studies in this thesis investigated if life experience could be a contributing factor to the diversity seen in the literature. Planning performance can be improved by either using external or internal support. Assistive technology for cognition (ATC) is an example of external support. This thesis investigated how the ATC is being used in an everyday planning situation which has not been investigated before. Furthermore, this thesis explored whether the internal supports of cognitive abilities and life experience correlate with planning ability in adolescents with ID, and if planning ability can be trained using a cognitive training program for everyday planning. Results showed that ATC supported cognitive functions, but that the children did not formulate the plans themselves. Furthermore, the results support the difference model of ID since planning correlated with different cognitive measures and life experience in adolescents with ID compared to children with a typical development. Adolescents with ID got better at the planning tasks in the training program, however, no transfer effects to untrained planning tasks were found. To conclude, the planning was supported by external and internal support. However, ATC needs to be designed and prescribed in a way that increases independence. Practitioners should actively support in training planning and should be cautious when introducing cognitive interventions if the transfer gap is too large.  

    List of papers
    1. Parents act as intermediary users for their children when using assistive technology for cognition in everyday planning: Results from a parental survey
    Open this publication in new window or tab >>Parents act as intermediary users for their children when using assistive technology for cognition in everyday planning: Results from a parental survey
    2019 (English)In: Assistive technology, ISSN 1040-0435, E-ISSN 1949-3614, p. 1-9Article in journal (Refereed) Published
    Abstract [en]

    Assistive Technology for Cognition (ATC) is employed by children with and without disabilities. However, how the ATC is used in everyday life has not been studied. The current study investigated ATC-usage in everyday planning in three groups: 1) children qualifying for Swedish habilitation centers (ID/ASD), 2) children with disability not qualifying for habilitation service (ADHD), and 3) children with typical development (TD). A parental survey was conducted (n = 192) and answers were analyzed with statistical tests and inductive thematic text analysis. Results showed that all groups used ATC, most in the Habilitation group and least in the TD group. According to parents, ATC supported cognitive functions in all groups, but it became evident that the parents were responsible for planning by setting up the ATC, whilst the children merely executed the plans. This was linked to several limitations, for example the design was not appropriately adapted for these groups. The implications for the practitioners are 1) evaluate the users? cognitive abilities and choose an ATC suitable for that individual rather focusing on the diagnosis, and 2) follow up usage to see if it is the parent or the child that are using the ATC.

    Place, publisher, year, edition, pages
    Taylor & Francis, 2019
    Keywords
    Activities of daily living, assessment, cognitive impairment, developmental disability, electronic aids to daily living, usability
    National Category
    Pediatrics
    Identifiers
    urn:nbn:se:liu:diva-164915 (URN)10.1080/10400435.2018.1522523 (DOI)
    Available from: 2020-04-01 Created: 2020-04-01 Last updated: 2020-04-01Bibliographically approved
    2. Cognitive abilities and life experience in everyday planning in adolescents with intellectual disabilities: Support for the difference model
    Open this publication in new window or tab >>Cognitive abilities and life experience in everyday planning in adolescents with intellectual disabilities: Support for the difference model
    2020 (English)In: Journal of Intellectual Disability Research, ISSN 0964-2633, E-ISSN 1365-2788Article in journal (Refereed) Epub ahead of print
    Abstract [en]

    Background The literature on planning ability in individuals with intellectual disability (ID) provides no clarity on whether their ability matches their mental age (MA) or not. Perhaps can planning experience explain the mixed results. The current study investigated to what extent cognitive abilities and life experience can explain everyday planning ability in individuals with ID and to what extent results from everyday planning tasks support the developmental or the difference model of ID. Method Planning tests, cognitive ability tasks and a self-rated life experience form were administered to 71 adolescents with ID and 62 children with a typical development matched on MA. Results Adolescents with ID exhibited planning ability according to their MA. Regression analyses showed that the predictors of planning differed between the groups. The cognitive measures could predict planning in both groups, but life experience only contributed positively to planning in the MA group, whereas chronological age was negatively correlated with successful planning in the ID group. Conclusions and discussion The results support the difference model of ID. When matched on MA, the individuals with ID will solve the planning task in a qualitatively different manner. Additionally, the participants with ID could not utilise their life experience when solving the planning task, contrary to the MA group. Practitioners should be aware that individuals with ID might need more everyday planning training throughout adolescence. To support adolescents with ID, practitioners may focus on supporting the individuals cognitive abilities rather than relying on their prior knowledge.

    Place, publisher, year, edition, pages
    WILEY, 2020
    Keywords
    cognitive abilities; difference model; errand task; everyday planning; intellectual disability
    National Category
    Occupational Therapy
    Identifiers
    urn:nbn:se:liu:diva-163409 (URN)10.1111/jir.12710 (DOI)000505491500001 ()31898385 (PubMedID)
    Note

    Funding Agencies|Stiftelsen Savstaholm [ST 2016-030]

    Available from: 2020-02-04 Created: 2020-02-04 Last updated: 2020-04-01
  • Public defence: 2020-05-05 09:00 Berzeliussalen, Building 463, LinköpingOrder onlineBuy this publication >>
    Toll, Rani
    Linköping University, Department of Biomedical and Clinical Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Local Health Care Services in Central Östergötland, Department of Emergency Medicine in Linköping.
    To See or Not to See: A Study on Capillary Refill2020Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Background: Assessment of the critically ill is traditionally based on vital signs (blood pressure, pulse, respiratory rate, temperature and level of consciousness). Altered vital signs are, however, late indicators of deranged hemodynamics pointing to a need for additional, more sensitive markers of circulatory compromise. In the beginning of the 20th century, the capillary refill (CR) time evolved as a possible, non-invasive adjunct to early prediction of the outcome in the critically ill. The manoeuvre entails application of blanching pressure on the skin of the finger pulp or sternum for 5 seconds. After release of the pressure, the observer estimates time in seconds for the skin to return to original colour. This time is hypothesized to reflect the dynamics of the microcirculation and its possible connection with hemodynamics. In the 1980s the “normal capillary refill time” was set to < 2 seconds and later extended to 3 seconds, without a clear scientific foundation. Naked-eye estimations of CR time met increasing scepticism in the 1990s due to subjectivity and poor prognostic value for shock or death. Several basic traits, such as age and sex, as well as ambient temperature, were also shown to independently influence the CR time. Various methods have evolved with the capability to measure CR time quantitatively, one of which is Polarisation Spectroscopy Imaging (PSI). PSI measures the Red Blood Cell (RBC) concentration in tissue (e.g. the skin) and can be used to measure CR time.

    Objectives: The purpose of this study was to establish basic characteristics for quantified CR (qCR), identify possible influencing factors in healthy subjects and to investigate how this relates to current practice. We also sought to identify technical demands for transfer of the technique into clinical studies. In paper I we analysed the (qCR) time characteristics at 5 different skin sites (forehead, sternum, volar forearm, finger pulp and dorsum finger). The objective of paper II was to investigate the inter- and intra-observer variability of naked eye CR assessments of different professions, nurses, doctors and secretaries (representing laymen). In paper III we observed the effect of low ambient temperature on the qCR time in different skin sites. In paper IV, we transferred the equipment from a laboratory to a clinical setting in the Emergency Department (ED) for application on potentially critically ill patients. In this study we evaluated the most important factors determining a reliable data collection and influencing the amount of data possible to analyse.

    Methods: qCR time was measured in a total of 38 volunteers and 10 patients in different skin sites (2-5 skin sites) at different ambient temperatures. PSI (TiVi 600 and 700, WheelsBridge AB, Linköping, Sweden) was used to determine the rapid temporal changes in RBC concentration in skin during the CR manoeuvre. Films using a range of the first measurements from paper I were shown for assessment to 48 observers working in the ED.

    Results: In paper I we could delineate qCR curves and suggest 2 possible equivalents to the naked-eye observed CR time which we named Time to Return to Baseline 1 (tRtB1) and Time to Peak (tpk). We demonstrated differences in qCR-curves depending on skin site and possibly due to skin temperature. In paper II we showed a poor inter- and intra-observer reproducibility in visually estimating the CR time regardless of profession (clinicians or laymen). Paper III demonstrated a rapid effect of ambient temperature on qCR time in peripheral skin sites such as finger pulp. The forehead, regarded as a more central skin site was the most temperature stable site and showed least variability in qCR time as determined using tRtB1. Paper IV, a study on patients in an ED setting, yielded assayable data in 80% of the measurements. We identified critical performance parameters to address in the further development of a more robust, easy-to-use device for future validation of the possible relevance of qCR in patient triage and monitoring.

    Conclusions: CR time can be quantified using PSI. Quantified CR time demonstrated a large variability between different skin sites, specifically, skin temperature was shown to be an important factor influencing qCR time, particularly at the fingertip. Naked-eye estimates of CR time were highly variable, both within and between observers. Agreement between quantified CR time and naked-eye estimates was poor. The prototypic PSI technique was feasible in a clinical setting and, with further improvements, clinical evaluation of qCR in relation to relevant patient outcomes will be possible.

    List of papers
    1. Reflectance spectroscopy: to shed new light on the capillary refill test
    Open this publication in new window or tab >>Reflectance spectroscopy: to shed new light on the capillary refill test
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    2018 (English)In: Journal of Biophotonics, ISSN 1864-063X, E-ISSN 1864-0648, Vol. 11, no 1, article id e201700043Article in journal (Refereed) Published
    Abstract [en]

    To use Bioengineering methodology is used to achieve, at five anatomical sites, a detailed, quantitative assessment of the return of blood content to the blanched area, during the Capillary Refill (CR) test. An observational, non-randomized, experimental study on 23 healthy subjects (14 females) was performed in our climate controlled skin physiology laboratory. Our main outcome measures were based on the chronological assessment and quantification of red blood cell concentration (RBC) after the release of blanching pressure in the CR test, using Tissue Viability Imaging (TiVi), a digital photographic technique based on polarisation spectroscopy. TiVi enabled collection of detailed data on skin RBC concentration during the CR test. The results were shown as curves with skin blood concentration (TiVi-value) on the y-axis and the time on the x-axis. Quantitative CR responses showed site and temperature variability. We also suggest possible objective endpoint values from the capillary refill curve. Detailed data on skin RBC concentration during the CR test is easily obtained and allows objective determination of end points not possible to achieve by naked eye assessment. These findings have the potential to place the utility of the CR test in a clinical setting in a new light. Picture: Regular photograph and TiVi Image showing CR test and corresponding graph for the CR response. [GRAPHICS] .

    Place, publisher, year, edition, pages
    Wiley-VCH Verlagsgesellschaft, 2018
    Keywords
    Capillary refill; microvasculature; circulation; skin imaging; gender variability; blood concentration
    National Category
    Dermatology and Venereal Diseases
    Identifiers
    urn:nbn:se:liu:diva-145478 (URN)10.1002/jbio.201700043 (DOI)000425294600022 ()28544641 (PubMedID)2-s2.0-85019540776 (Scopus ID)
    Available from: 2018-03-05 Created: 2018-03-05 Last updated: 2020-04-01Bibliographically approved
    2. Man versus machine: comparison of naked-eye estimation and quantified capillary refill
    Open this publication in new window or tab >>Man versus machine: comparison of naked-eye estimation and quantified capillary refill
    2019 (English)In: Emergency Medicine Journal, ISSN 1472-0205, E-ISSN 1472-0213, Vol. 36, no 8, p. 465-471Article in journal (Refereed) Published
    Abstract [en]

    Background Capillary refill (CR) time is traditionally assessed by naked-eye inspection of the return to original colour of a tissue after blanching pressure. Few studies have addressed intra-observer reliability or used objective quantification techniques to assess time to original colour. This study compares naked-eye assessment with quantified CR (qCR) time using polarisation spectroscopy and examines intra-observer and interobserver agreements in using the naked eye. Method A film of 18 CR tests (shown in a random fixed order) performed in healthy adults was assessed by a convenience sample of 14 doctors, 15 nurses and 19 secretaries (Department of Emergency Medicine, Linkoping University, September to November 2017), who were asked to estimate the time to return to colour and characterise it as fast, normal or slow. The qCR times and corresponding naked-eye time assessments were compared using the Kruskal-Wallis test. Three videos were shown twice without observers knowledge to measure intra-observer repeatability. Intra-observer categorical assessments were compared using Cohens Kappa analysis. Interobserver repeatability was measured and depicted with multiple-observer Bland-Altman plotting. Differences in naked-eye estimation between professions were analysed using ANOVA. Results Naked-eye assessed CR time and qCR time differ substantially, and agreement for the categorical assessments (naked-eye assessment vs qCR classification) was poor (Cohens kappa 0.27). Bland-Altman intra-observer repeatability ranged from 6% to 60%. Interobserver agreement was low as shown by the Bland-Altman plotting with a 95% limit of agreement with the mean of +/- 1.98 s for doctors, +/- 1.6 s for nurses and +/- 1.75 s for secretaries. The difference in CR time estimation (in seconds) between professions was not significant. Conclusions Our study suggests that naked-eye-assessed CR time shows poor reproducibility, even by the same observers, and differs from an objective measure of CR time.

    Place, publisher, year, edition, pages
    BMJ PUBLISHING GROUP, 2019
    National Category
    Anesthesiology and Intensive Care
    Identifiers
    urn:nbn:se:liu:diva-159714 (URN)10.1136/emermed-2018-207948 (DOI)000478913300006 ()31308133 (PubMedID)
    Note

    Funding Agencies|Region Ostergotland [LIO-532001, LIO-700271]

    Available from: 2019-08-19 Created: 2019-08-19 Last updated: 2020-04-01
    3. A cool response: the influence of ambient temperature on capillary refill time
    Open this publication in new window or tab >>A cool response: the influence of ambient temperature on capillary refill time
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    2018 (English)In: Journal of Biophotonics, ISSN 1864-063X, E-ISSN 1864-0648, Vol. 11, no 6Article in journal (Refereed) Published
    Abstract [en]

    Objective

    To describe the effect of low ambient temperature on skin temperature and capillary refill (CR) time in forehead, sternum and finger pulp.

    Methods

    An observational, nonrandomized experimental study on 15 healthy subjects (6 females) in a cold room (8°C). Outcome measures were skin temperature and quantified CR test after application of a standardized blanching pressure (9 N/cm2) using digital photographic polarization spectroscopy to generate CR times.

    Results

    The finger pulp showed marked temperature fall and prolonged CR times (>10 seconds). The CR registrations of the forehead and sternum were more comparable to curves observed in a control material at room temperature, and skin temperature falls were less marked. CR times were not prolonged in forehead measurements. At the sternum, some individuals showed CR times beyond guideline recommendations despite only a marginal reduction in skin temperature.

    Conclusions

    Low ambient temperature is a strong independent factor for CR time at peripheral sites. Reservation about sternum as a site of measurement is warranted since cold provocation produced prolonged CR times in some individuals. We found that the forehead is the most thermostable of the 3 sites and thus the preferred site to avoid ambient temperature artifact in measuring CR time.

    Place, publisher, year, edition, pages
    Wiley-VCH Verlagsgesellschaft, 2018
    National Category
    Atom and Molecular Physics and Optics
    Research subject
    Disaster Medicine
    Identifiers
    urn:nbn:se:liu:diva-145527 (URN)10.1002/jbio.201700371 (DOI)000434641700017 ()29384267 (PubMedID)
    Note

    Funding agencies: Socialstyrelsen; Region Ostergotland

    Available from: 2018-03-05 Created: 2018-03-05 Last updated: 2020-04-01Bibliographically approved
  • Public defence: 2020-05-05 13:15 C3 C-Building, Linköping
    Ekman, Petter
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering.
    Important Factors for Accurate Scale-Resolving Simulations of Automotive Aerodynamics2020Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Road transports are responsible for almost 18 % of the greenhouse gas emission in Europe and are today the leading cause of air pollution in cities. Aerodynamic resistance has a significant effect on fuel consumption and hence the emission of vehicles. For electric vehicles, emissions are not affected by the aerodynamics as such but instead have a significant effect on the effective range of the vehicle.

    In 2017, a new measurement procedure was introduced, Worldwide Harmonized Light Vehicles Test Procedure (WLTP), for measuring emissions, fuel consumption, and range. This procedure includes a new test cycle with increased average driving speed compared to the former procedure, which thereby increases the importance of the aerodynamic resistance, as it drastically increases with speed. A second effect is that the exact car configuration sold to the customer needs to be certified in terms of fuel consumption and emissions. The result is that every possible combination of optional extras, which might affect the aerodynamic resistance, needs to be aerodynamically analyzed and possibly improved. From 2021, the European Commission will introduce stricter emission regulations for new passenger cars, with the fleet-wide average lowered to 95 grams CO2=km, which puts an even higher demand on achieving efficient aerodynamics.

    Virtual development of the aerodynamics of road vehicles is today used to a great extent, using Computational Fluid Dynamics, as it enables faster and cheaper development. However, achieving high accuracy for the prediction of the flow field and aerodynamic forces is challenging, especially given the complexity of both the vehicle geometry in itself and the surrounding flow field. Even for a simplified generic bluff body, accurately predicting the flow field and aerodynamic forces is a challenge. The main reason for this challenge of achieving results with high accuracy is the prediction of the complex behavior of turbulence. Scale-resolving simulation (SRS) methods, such as Large Eddy Simulation (LES), where most of the turbulent structures are resolved has in many studies shown high accuracy but unfortunately to a very high computational cost. It is primarily the small turbulent structures within the near-wall region that requires a _ne resolution in both space (the mesh) and in time. This fine resolution is the reason for the very high computational cost and makes LES unfeasible for practical use in industrial aerodynamic development at present and in the near future. By modeling the turbulent structures within the near-wall region using a Reynolds-Averaged Navier-Stokes (RANS) model, and resolving the turbulence outside the region with a LES model, a coarser resolution is possible to use, resulting in significantly lower computational cost. Which used RANS model is of high importance, and especially how much turbulent viscosity the model generates, as too high values can result in suppression of the resolved turbulence.

    The transitioning between the RANS and LES regions have a significant effect on the results. Faster transition enables more resolved turbulence, favorable for higher accuracy, but needs to be balanced with sufficient shielding of the RANS region. If resolving the turbulence occurs within the near-wall region, and the mesh is not sufficiently fine, it can result in poor accuracy.

    By increasing the time-step size and disregarding best-practice guides, the computational cost can be significantly reduced. The accuracy is reasonably insensitive to the larger time step sizes until a certain degree, thereby enabling computationally cheaper SRS to achieve high accuracy of aerodynamic predictions needed to meet present and future emission regulations.

    List of papers
    1. Aerodynamic Drag Reduction - from Conceptual Design on a Simplified Generic Model to Full-Scale Road Tests
    Open this publication in new window or tab >>Aerodynamic Drag Reduction - from Conceptual Design on a Simplified Generic Model to Full-Scale Road Tests
    2015 (English)In: SAE 2015 World Congress & Exhibition, SAE International , 2015Conference paper, Published paper (Refereed)
    Abstract [en]

    Road transportation by trucks is the major part of the goods transportations system in the European Union (EU), and there is a need for increased fuel efficiency. While truck manufacturers already spend significant resources in order to reduce the emissions from their vehicles, most truck manufacturers do not control the shape of the trailer and/or swap bodies. These devices are usually manufactured by different companies that cannot consider the overall aerodynamics around the complete vehicle.By use of Computational Fluid Dynamics (CFD) and previous wind tunnel experiments, the flow around a simplified generic tractor-trailer model has been investigated. With better understanding of the flow features around the tractor with attached trailer or swap bodies, an improved design of the trailer and swap body can be achieved, which is the aim for the project. Special emphasis is put on achieving simple, easy to install or implement drag-reducing geometrical modifications to the trailer or swap bodies that can be mounted on existing trucks.Reynolds-Averaged Navier-Stokes (RANS) simulations were used for the conceptual development phase where trends in drag reduction due to the modified geometries were studied using a parameter study, while more advanced scale resolving simulations (SRS) were used in order to investigate the details of the flow fields.The investigation indicates that aerodynamic drag reduction is possible with quite simple geometrical modifications. Some of the results have also been verified through road tests of vehicles in commercial use, which has shown reduced fuel consumption of up to 5%.

    Place, publisher, year, edition, pages
    SAE International, 2015
    National Category
    Vehicle Engineering
    Identifiers
    urn:nbn:se:liu:diva-164920 (URN)10.4271/2015-01-1543 (DOI)
    Conference
    SAE 2015 World Congress & Exhibition
    Available from: 2020-04-02 Created: 2020-04-02 Last updated: 2020-04-02Bibliographically approved
    2. Aerodynamic Drag Reduction of a Light Truck - from Conceptual Design to Full Scale Road Tests
    Open this publication in new window or tab >>Aerodynamic Drag Reduction of a Light Truck - from Conceptual Design to Full Scale Road Tests
    2016 (English)In: SAE 2016 World Congress and Exhibition, SAE International , 2016Conference paper, Published paper (Refereed)
    Abstract [en]

    Considerable amounts of the everyday goods transports are done using light trucks. In the last ten years (2005-2015), the number of light trucks has increased by 33 % in Sweden. The majority of these light trucks are fitted with a swap body and encounter the same problem as many other truck configurations, namely that several different manufacturers contribute to the final shape of the vehicle. Due to this, the aerodynamics of the final vehicle is often not fully considered. Hence there appears to be room for improving the aerodynamic performance. In this study the flow around a swap body fitted to a light truck has been investigated using Computational Fluid Dynamics. The focus has been on improving the shape of the swap body in order to reduce both the aerodynamic drag and fuel consumption, while still keeping it usable for daily operations. Reynolds-Averaged Navier-Stokes simulations were used for concept evaluation while more advanced Detached Eddy Simulations were performed on the best concept in order to investigate details of the flow. Various concepts were evaluated from which it could be seen that a more streamlined top of the swap body together with a lowered top trailing edge had a significant positive effect on the aerodynamic drag. A full scale light truck was equipped with a swap body with with these modifications for road tests. During a test period, a mean fuel consumption reduction of 12 % was measured, thus indicating a significantly reduced aerodynamic drag.

    Place, publisher, year, edition, pages
    SAE International, 2016
    National Category
    Vehicle Engineering
    Identifiers
    urn:nbn:se:liu:diva-164923 (URN)10.4271/2016-01-1594 (DOI)
    Conference
    SAE 2016 World Congress and Exhibition
    Available from: 2020-04-02 Created: 2020-04-02 Last updated: 2020-04-02Bibliographically approved
    3. Aerodynamics of an Unloaded Timber Truck - A CFD Investigation
    Open this publication in new window or tab >>Aerodynamics of an Unloaded Timber Truck - A CFD Investigation
    2016 (English)In: SAE International Journal of Commercial Vehicles, ISSN 1946-391X, E-ISSN 1946-3928, Vol. 9, no 2, p. 217-223Article in journal (Refereed) Published
    Abstract [en]

    Reducing energy consumption and emissions are ongoing challenges for the transport sector. The increased number of goods transports emphasize these challenges even more, as greenhouse gas emissions from these vehicles increased by 20 % between 1990 and 2013, in Sweden. One special case of goods transports is the transport of timber. Today in Sweden, around 2000 timber trucks transport around six billion ton kilometers every year. For every ton kilometer these vehicles use around 0.025 liter diesel, and there should exist large possibilities to reduce the fuel consumption and the emissions for these vehicles. Timber trucks spend most of their operation time travelling in speeds of around 80 km/h. At this speed aerodynamic drag contributes to around 30 % of the total vehicle resistance, which makes the aerodynamic drag a significant part of the energy consumption. One of the big challenges with timber trucks is that they travel unloaded half of the time. This put higher demands on possible drag reduction modifications, as they need to function and be practical for both when the timber truck is loaded and unloaded. In this study an unloaded timber truck has been investigated by use of computational fluid dynamics. The recently released Stress Blended Eddy Simulation model has been used for simulating the flow over a timber truck at a Reynolds number of 1.1 million, based on the square root of its frontal area. From the results it could be seen that 52.8 % of the drag is generated by the cab. By investigating a drag reduction device that covered the gap between the bulkhead and the first stake pair, a drag reduction up to 6.7 % was possible, which shows potential for simple modifications that not influence the daily usage.

    Place, publisher, year, edition, pages
    SAE INT, 2016
    National Category
    Transport Systems and Logistics
    Identifiers
    urn:nbn:se:liu:diva-163998 (URN)10.4271/2016-01-8022 (DOI)000389233800010 ()
    Available from: 2020-03-05 Created: 2020-03-05 Last updated: 2020-04-02
    4. Accuracy and Speed for Scale-Resolving Simulations of the DrivAer Reference Model
    Open this publication in new window or tab >>Accuracy and Speed for Scale-Resolving Simulations of the DrivAer Reference Model
    2019 (English)In: WCX SAE World Congress Experience, SAE International , 2019Conference paper, Published paper (Refereed)
    Abstract [en]

    In aerodynamic development of ground vehicles, the use of Computational Fluid Dynamics (CFD) is crucial for improving the aerodynamic performance, stability and comfort of the vehicle. Simulation time and accuracy are two key factors of a well working CFD procedure. Using scale-resolving simulations, accurate predictions of the flow field and aerodynamic forces are possible, but often leads to long simulation time. For a given solver, one of the most significant aspects of the simulation time/cost is the temporal resolution. In this study, this aspect is investigated using the realistic vehicle model DrivAer with the notchback geometry as the test case. To ensure a direct and accurate comparison with wind tunnel measurements, performed at TU Berlin, a large section of the wind tunnel is included in the simulation domain. All simulations are performed at a Reynolds number of 3.12 million, based on the vehicle length. Three spatial resolutions were compared, where it could be seen that a hybrid element mesh consisting of 102 million cells only revealed small differences to the finest mesh investigated, well as showing excellent agreement with wind tunnel measurements. An investigation of the temporal resolution is performed, in order to see its effect on the simulation time/cost and accuracy of the results. The finest temporal resolution resulted in a Courant-Friedrichs-Lewy number less than unity, while the coarsest reached a CFL number of around 100. From these results, it is seen that it is possible to reduce the simulation time with more than 90 % (CFL 20) and still keep sufficient accuracy of the forces and important features of the flow field.

    Place, publisher, year, edition, pages
    SAE International, 2019
    National Category
    Vehicle Engineering
    Identifiers
    urn:nbn:se:liu:diva-164924 (URN)10.4271/2019-01-0639 (DOI)
    Conference
    WCX SAE World Congress Experience
    Available from: 2020-04-02 Created: 2020-04-02 Last updated: 2020-04-02Bibliographically approved