| 1. |
- Andreasson, Jakob, 1975, et al.
(författare)
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Electron-phonon interactions in perovskites containing Fe and Cr studied by Raman scattering using oxygen-isotope and cation substitution
- 2008
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X .- 2469-9950 .- 2469-9969. ; 78:23, s. 235103-
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Tidskriftsartikel (refereegranskat)abstract
- We use temperature-dependent inelastic light scattering to study the origin of the strong multiphonon scattering of a local oxygen breathing mode present in the mixed B-site orthorhombic (space group Pnma) perovskite LaFe0.5Cr0.5O3 but absent in isostructural LaFeO3 and LaCrO3. It is seen that the multiphonon scattering is critically sensitive to the presence of both Fe and Cr ions on the B site. These results support our interpretation that the multiphonon scattering is activated by local electron-phonon interactions according to the Franck-Condon picture following an Fe-Cr charge transfer. Further, O-18 substitution is performed on the x=0, 0.04, and 0.5 compounds and clearly shows that all modes appearing above the first-order phonon-scattering region in these compounds originate from higher-order oxygen stretching vibrations. In particular this is the case for the strong second-order scattering dominating the scattering response in LaFeO3. Accordingly we propose that these modes are generated by infrared-active longitudinal optical (IR LO) two-phonon and combination scattering activated by Frohlich interaction. For x=0.02 and 0.04 the characteristic IR LO two-phonon and Franck-Condon multiphonon-scattering profiles mix. We also study the influence of isovalent cation substitution and Sr doping in AFe(0.5)Cr(0.5)O(3) (A=La, Nd, and Gd) and La1-ySryFe0.5Cr0.5O3-delta (y=0, 0.16, and 0.5) on the strong electron-phonon coupling present in LaFe0.5Cr0.5O3. The Franck-Condon effect in LaFe0.5Cr0.5O3, is not significantly affected by isovalent A-site substitution, despite the increasing orthorhombic distortion associated with decreasing A-site ionic radii. On the contrary, aliovalent Sr doping causes a rapid decrease in the Franck-Condon scattering. This shows that the strong electron-phonon coupling in these compounds is highly sensitive to local lattice and electronic decoherence but insensitive to global lattice distortions. Finally, a preliminary assignment of the A(g) and B-2g phonon modes in AFe(0.5)Cr(0.5)O(3) (A=La, Nd, and Gd) is made based on the present observations and published results for LaCrO3 and AMnO(3). The modes associated with oxygen octahedral tilt and bending vibrations are heavily influenced by the magnitude of the orthorhombic distortion.
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| 2. |
- Bryndahl, Fredrik, 1963-
(författare)
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Temporomandibular joint disk displacement and subsequent adverse mandibular growth : a radiographic, histologic and biomolecular experimental study
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The mandibular condyles represent important growth sites within the facial skeleton. Condylar growth is not a pacemaker of mandibular development, but it provides regional adaptive growth that is of considerable clinical significance, as the condyle’s upward and backward growth movement regulates the anteriorly and inferiorly directed displacement of the mandible as a whole.Orthopedic problems of the temporomandibular joint (TMJ), such as displacement of the TMJ disk, are common in the adolescent population. Clinical studies of mandibular asymmetry and mandibular retrognathia in adults as well as in children and adolescents, have reported an association with coexisting non-reducing displacement of the TMJ disk without identifying the cause and effect. Through experimental studies causality has been established, and unilateral affliction during growth has been shown to retard ipsilateral mandibular development with facial asymmetry as the sequel. It was hypothesized that bilateral non-reducing TMJ disk displacement during growth would impair mandibular development bilaterally, resulting in mandibular retrognathia. TMJ disk displacement has repeatedly been demonstrated to induce histological reactions of the condylar cartilage. An additional assumption was therefore that a non-deranged TMJ disk function is crucial for the maintenance of the growing condyle’s biophysical environment, and that a connection ought to exist between the amount of condylar cartilage changes caused by TMJ disk displacement and the amount of subsequent adverse mandibular growth. It was also hypothesized that non-reducing displacement of the TMJ disk in growing individuals would result in qualitative and quantitative changes of the condylar subchondral bone.An improved experimental cephalometric method was developed in order to optimize the reliability of longitudinal radiographic evaluation of fast growing small animals. Bilateral non-reducing TMJ disk displacement was surgically created in ten growing New Zealand White rabbits, with ten additional rabbits serving as a sham operated control group. The amount and direction of craniofacial growth was followed over time in serial cephalograms, aided by tantalum implants in the jaws. The study period was chosen to correspond to childhood and adolescence in man. The assessed growth of each side of the mandible was correlated to the histological feature of ipsilateral condylar cartilage at the end of the growth period. The amount and composition of subchondral bone from three regions of interest in the condyle, and the expression of local growth factors in the adjacent condylar cartilage was evaluated.The results verified that bilateral non-reducing TMJ disk displacement retarded mandibular growth bilaterally; the extent corresponding to mandibular retrognathia in man. Displacement of the TMJ disk during the growth period induced condylar cartilage adaptive reactions that were associated with both an adverse amount and direction of mandibular growth, manifesting in a retrognathic mandibular growth pattern. Growth impairment fluctuated over time, with the most striking retardation occurring during periods of increased general growth, implying a local growth reduction explicitly counteracting general hormonal growth acceleration. A significant decrease of the total amount of subchondral bone, in spite of a general increase of new bone formation in the experimental condyles, pointed to a reparative compensation for an extensive resorption of subchondral bone due to displacement of the TMJ disk, but not to the extent that normal growth would be maintained. These results constitute an explanation for the adverse mandibular development following non-reducing TMJ disk displacement in growing individuals.This project has shown that non-reducing displacement of the TMJ disk during growth has significant consequences on facial development. The findings strongly advocate early and accurate diagnosis and treatment of TMJ disk displacement in the adolescent population, thereby presumably reducing the need for future orthodontic and surgical craniofacial corrective therapy. The results furthermore enhance the need for full appraisal of TMJ disk function in the adolescent population during orthodontic functional therapy, as the condylar cartilage and subchondral bone reactions to a concomitantly displaced non-reducing TMJ disk must be expected to interfere with the intended growth stimulating treatment. The findings of intact articular layers in spite of gross histological and morphological soft and hard tissue changes as a sequel to TMJ disk displacement in growing individuals, implicate a clinical risk of false positive radiographic diagnosis of degenerative changes of the TMJ in children and adolescents.
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| 3. |
- Eriksson, Mats, 1963-, et al.
(författare)
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Morphology changes of thin Pd films grown on SiO2: influence of adsorbates and temperature
- 1999
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Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 342:1-2, s. 297-306
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Tidskriftsartikel (refereegranskat)abstract
- Under certain conditions morphology changes occur when thin Pd films, grown on SiO2 at room temperature, are subject to elevated temperatures. First holes in the metal are observed, followed by network formation and finally isolation of metal islands. This process is known as agglomeration. The influence of gas exposures on this restructuring process has been studied by following variations in the capacitance of the structure and by atomic force microscopy, transmission electron microscopy and ultraviolet photoelectron spectroscopy. The capacitance measurements show that carbonaceous species have an impeding influence on the rate of agglomeration and may lock the film structure in a thermodynamic non-equilibrium state. By removing these species with oxygen exposure, i.e. by forming volatile CO and CO2, a clean surface is obtained and the agglomeration process can proceed. High oxygen or hydrogen coverages also lower the rate of restructuring, compared to the case of a clean surface. For the clean Pd surface, an apparent activation energy of 0.64 eV is found for the restructuring process.
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| 4. |
- Eriksson, Mats, 1963-, et al.
(författare)
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The water-forming reaction on thin, SiO2 supported, palladium films
- 1990
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Ingår i: Vacuum. - 0042-207X .- 1879-2715. ; 41:1-3, s. 137-138
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Tidskriftsartikel (refereegranskat)abstract
- The water-forming reaction has been studied on thin Pd films, evaporated on planar SiO2 substrates. The nominal film thickness varied between 5 and 100 Å. The studies were performed in uhv by means of mass spectrometry, UPS and work function measurements in the temperature range 323–523 K. The film structure was also studied with TEM. The results are compared with previous measurements on 1000 Å, thick, homogeneous Pd films. The structure of the thin Pd films changed dramatically during cyclic H2 and O2 exposures, from that of a continuous film with cracks to that of drop-like metal particles. These structural changes are not observed on the thick (1000 Å) Pd films. Even though there are large structural changes, the water-forming reaction looks qualitatively the same as on a thick Pd film. The total water production however, decreases with decreasing film thickness. We believe that some minor qualitative differences in the water-forming reaction for different nominal Pd film thicknesses, are due to the increasing PdSiO2 boundary as the thickness is reduced.
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| 5. |
- Erlandsson, Ragnar, et al.
(författare)
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Gas-induced restructuring of palladium model catalysts studied with atomic force microscopy
- 1991
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Ingår i: Journal of Vacuum Science & Technology B. - : American Vacuum Society. - 1071-1023 .- 1520-8567. ; 9:2, s. 825-828
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Tidskriftsartikel (refereegranskat)abstract
- The structure of thin Pd films evaporated onto planar SiO2 substrates changes dramatically during oxygen/hydrogen exposures in ultrahigh vacuum. In this work we have used an atomic force microscope(AFM), operated in the attractive mode, to obtain the three‐dimensional morphology of the Pd surface for different film thicknesses and treatments, and compared the data with transmission electron microscopy(TEM) micrographs. During restructuring, a 100‐Å film changes from being a smooth continuous film with cracks into metal clusters dispersed on the SiO2 support. In the 5‐Å case the metal films are already well dispersed as fabricated. Here the gas exposure instead results in a clustering effect resulting in larger particles. The AFM gives results which are consistent with TEM micrographs but also gives additional information on metal particle shape which can lead to a further understanding of the restructuring process.
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| 6. |
- Ghazzali, Mohamed I D M, 1974, et al.
(författare)
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Syntheses, crystal structures, optical limiting properties, and DFT calculations of three thiophene-2-aldazine Schiff base derivatives
- 2007
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Ingår i: New Journal of Chemistry. - : Royal Society of Chemistry (RSC). - 1369-9261 .- 1144-0546. ; 31:10, s. 1777-1784
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Tidskriftsartikel (refereegranskat)abstract
- The syntheses, characterizations and structural determinations of N,N'-bis(thiophenyl-2-methylene)hydrazine 1, N,N'-bis(4-bromothiophenyl-2-methylene)hydrazine 2 and N,N'-bis(5-bromothiophenyl-2-methylene)hydrazine 3 are presented. The materials show third-ordernonlinear behaviour with transmissions of 20, 22 and 18 μJ for an input energy of 150 μJ. The4- and 5-bromothiophenic structures show Br...Br interactions of 3.562 and 3.626 Å, respectively.Analysis of bromine containing aromatic compounds in the Cambridge CrystallographicDatabase (CSD) showed the expected angle dependences of the Br...Br interactions dividing theseinto ‘‘type I’’ and ‘‘type II’’. A semi-quantitative agreement was found between the CSD data anda model derived form calculated electrostatic potentials.
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| 7. |
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| 8. |
- Lidestam, Björn, 1968-, et al.
(författare)
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Speed perception affected by field of view : Energy-based versus rhythm-based processing
- 2019
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Ingår i: Transportation Research Part F. - : Elsevier. - 1369-8478 .- 1873-5517. ; 65, s. 227-241
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Tidskriftsartikel (refereegranskat)abstract
- Two experiments were carried out to test speed perception dependency on field of view (FoV), virtual road markings (VRMs), and presentation orders. The primary purpose was to examine how the extent of the optic flow (foremost peripherally–vertically) informs the driver about egospeed. A second purpose was to examine different task demands and stimulus characteristics supporting rhythm-based versus energy-based processing. A third purpose was to examine speed changes indicative of changes in motion sensitivity. Participants were tested in a car simulator, with FoV resembling low front-door windows, and with VRMs inside the car. Three main results were found. Larger FoV, both horizontally and peripherally–vertically, significantly reduced participants' speed, as did VRMs. Delineator posts and road center lines were used for participants' rhythm-based processing, when the task was to drive at target speeds. Rich motion-flow cues presented initially resulted in lower egospeed in subsequent conditions with relatively less motion-flow cues. The practical implication is that non-iconic, naturalistic and intuitive interfaces can effectively instill spontaneous speed adaptation in drivers.
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| 9. |
- Acke, Filip, 1968, et al.
(författare)
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Influence of the platinum-support interaction on the direct reduction of NOx under lean conditions
- 1998
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Ingår i: Studies in Surface Science and Catalysis. - 0167-2991. ; 116, s. 285-294
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Tidskriftsartikel (refereegranskat)abstract
- Catalysts containing Pt supported on SiC, Al2O3 and ZSM-5 were prepared and studied for NOx reduction by C3H6 in Oz excess under transient (temperature ramps) and steady-state conditions. The maximum NOx reduction activity in the heating ramp experiments was similar for Pt/SiC and Pt/ZSM-5, while Pt/Al2O3 showed higher maximum activity. Both N-2 and N2O formation was observed for all catalysts, although the respective amounts varied with the investigated system. Highest Nz selectivity was observed for Pt/Al2O3. When the NOx reduction activity was studied under steady-state conditions the activity of Pt/Al2O3 decreased substantially (mainly due to a loss in N-2 production). Pt/ZSM-5 became somewhat more selective towards Na production whereas the activity and selectivity of Pt/SiC remained at about the same values as far the heating ramp experiments. Adsorbed species on the surface of the different catalysts were investigated using in-situ FTIR in order to obtain information about the reaction mechanisms. The adsorption of species on Pt/SiC was negligible, while a number of absorption bands were observed for Pt/Al2O3 (N and C containing species, and -NCO) and Pt/ZSM-5 (HC).
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| 10. |
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| 11. |
- Andreasson, Jakob, 1975, et al.
(författare)
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Electron-lattice interactions in the perovskite LaFe0.5Cr0.5O3 characterized by optical spectroscopy and LDA plus U calculations
- 2009
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X .- 2469-9950 .- 2469-9969. ; 80:7, s. 075103-
-
Tidskriftsartikel (refereegranskat)abstract
- We use resonance Raman scattering (incident photon energies between 1.8 and 4.13 eV), LDA+U calculations, spectroscopic ellipsometry, and oblique IR reflectivity to characterize the strong electron-phonon interactions in the disordered perovskite LaFe0.5Cr0.5O3. When the photon energy coincides with a Cr to Fe Mott-Hubbard transfer gap around 2.4 eV the electron-phonon interaction is manifested by a Franck-Condon effect with exceptional first-and higher order scattering of a local oxygen breathing mode. At higher incident energies we observe a superposition of Franck-Condon scattering and Frohlich interaction induced infrared active longitudinal optical two-phonon scattering activated mainly by O to Fe charge transfer. Our results establish LaFe0.5Cr0.5O3 as a model compound for research on electron-phonon interactions in strongly correlated complex systems and show that Franck-Condon scattering in complex solids is not limited to Jahn-Teller active compounds.
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| 12. |
- Andreasson, Jakob, 1975, et al.
(författare)
-
Franck-Condon higher order lattice excitations in the LaFe(1-x)Cr(x)O3 (x=0, 0.1, 0.5, 0.9, 1.0) perovskites due to Fe-Cr charge transfer effects
- 2007
-
Ingår i: Physical Review B. ; 75, s. 104302-
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Tidskriftsartikel (refereegranskat)abstract
- First and higher order lattice excitiations in the B-site disordered perovskites LaFe(1-x)Cr(x)O3 (x = 0, 0.1, 0.5, 0.9, 1) and La(0.835)Sr(0.165)Fe(0.5)Cr(0.5)O(3-d) are investigated using temperature dependent and polarised inelastic light scattering [lambda = 515 nm (2.41 eV) and 676 nm (1.83 eV)] on oriented crystallites.A peak at approximately 2.4 eV in the imaginary part of the dielectric function of LaFe(0.5)Cr(0.5)O3 is assigned to a charge transfer from Fe 3+ (d5) to Cr 3+ (d3) ions and coupled the appearance of an intense Ag-like mode at approximately 700 cm-1 in the Raman data. This excitation is identified as a symmetric oxygen breathing mode activated by the Fe-Cr charge transfer through an orbital coupling mechanism. Higher order scattering (up to 7th order) of the intrinsic Raman active symmetric breathing mode is also explained by an orbital mediated, electron-phonon coupling, similar to the Franck-Condon effect observed in the Jahn-Teller active perovskite structured manganite LaMnO3. These results show that the Franck-Condon mechanism is a more common mechanism for resonant higher order scattering in solids than previously believed and propose the LaFe(1-x)Cr(x)O(3) system as a model system for electron-phonon coupling and higher order Raman scattering in solids.
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| 13. |
- Balachandran, Arvind, 1994-
(författare)
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Battery Integrated Modular Multilevel Converter Topologies for Automotive Applications
- 2023
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Electric vehicles are rapidly developing in response to the need for increasing sustainable energy sources. The range and lifetime of an electric vehicle are limited by the battery pack. A pack comprises modules with several parallel and/or series-connected cells. Differences in leakage currents and cell in-homogeneities cause individual cell voltage and state-of-charge distribution among the cells to be non-homogeneous. As a result, over time, some cells discharge faster than other cells, thus limiting the total energy delivered by the pack. In order to maximize the energy delivered by the pack, individual cell control is desirable. As a solution, battery-integrated modular multi-level converter (BI-MMC) topologies are proposed, presented, and evaluated. BI-MMC topology consists of either one or two arms per phase, and each arm comprises several cascaded stages of DC–AC converters and is commonly referred to as submodules. BI-MMCs provide increased controllability and potential improvement in the lifetime of the battery pack. Furthermore, BI-MMCs have low output total harmonic distortion, further improving the powertrain efficiency.The first contribution is the design and evaluation of 3-phase and 6-phase BI-MMCs; comparisons are made against a conventional 2-level inverter for a 40-ton 400 kW commercial vehicle. The evaluation considers the total number of submodules, energy rating of the DC-link capacitors, battery losses, capacitor losses, and semiconductor losses. The evaluation showed that the BI-MMCs have lower semiconductor losses than the conventional 2-level inverter. However, the BI-MMCs have higher capacitor and battery losses. The second contribution is the investigation of the impact that the number of series connected cells per submodule has on the total losses of the BI-MMC. The study showed that 5- to 6-series connected cells have the lowest losses. The third contribution is the design principles for optimization of the DC-link capacitors and the MOSFET switching frequency; this is supported by experimental validation for the loss distribution within a submodule. The fourth contribution is a methodology for determining the battery impedance using the full-load converter current. In a conventional battery pack, the battery is connected directly to the fast charger’s DC supply. However, in a BI-MMC, the battery and the inverter are integrated, potentially increasing the DC charging capabilities because higher voltages can be achieved during charging than during operation. The fifth contribution is thus the derivation and investigation of the maximum DC charging power of BI-MMCs assuming the same submodule semiconductor losses during traction. The analysis showed that most BI-MMCs have a maximum DC charging power of about 1MW.
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| 14. |
- Balachandran, Arvind, 1994-, et al.
(författare)
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DC Charging Capabilities of Battery-Integrated Modular Multilevel Converters Based on Maximum Tractive Power
- 2023
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Ingår i: Electricity. - : MDPI. - 2673-4826. ; 4:1, s. 62-77
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Tidskriftsartikel (refereegranskat)abstract
- The increase in the average global temperature is a consequence of high greenhouse gas emissions. Therefore, using alternative energy carriers that can replace fossil fuels, especially for automotive applications, is of high importance. Introducing more electronics into an automotive battery pack provides more precise control and increases the available energy from the pack. Battery-integrated modular multilevel converters (BI-MMCs) have high efficiency, improved controllability, and better fault isolation capability. However, integrating the battery and inverter influences the maximum DC charging power. Therefore, the DC charging capabilities of 5 3-phase BI-MMCs for a 40-ton commercial vehicle designed for a maximum tractive power of 400 kW was investigated. Two continuous DC charging scenarios are considered for two cases: the first considers the total number of submodules during traction, and the second increases the total number of submodules to ensure a maximum DC charging voltage of 1250 V. The investigation shows that both DC charging scenarios have similar maximum power between 1 and 3 MW. Altering the number of submodules increases the maximum DC charging power at the cost of increased losses.
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| 15. |
- Balachandran, Arvind, 1994-, et al.
(författare)
-
Experimental Evaluation of Submodule Losses in Battery-Integrated MMCs with NLM and PSPWM
- 2024
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Konferensbidrag (refereegranskat)abstract
- Electric vehicle (EV) battery packs contain several parallel and series-connected cells and variations in leakage currents and cell characteristics result in heterogeneous discharge rates among cells, thus limiting the total energy delivery of the pack. Battery-integrated modular multilevel converters (BI-MMCs) increase the controllability of cells thereby improving the energy utilization of the battery pack. Design optimization for BI-MMC with phase-shifted modulation (PSPWM) showed that submodule (SM) DC-link capacitors designed to bypass the switching frequency components result in minimum total losses. However, this requires a large DC-link capacitor bank, which increases the system cost. An alternative modulation technique, nearest level modulation (NLM), characterized by low semiconductor switching frequency, is often preferred for MMCs with many SMs. The first contribution is an experimental loss comparison in an SM of a BI-MMC with PSPWM and NLM. The second contribution is investigating the impact of the size of DC-link capacitors on battery and capacitor losses for NLM. The experiments showed that the battery and capacitor losses are independent of the DC-link capacitor size when using NLM. Furthermore, NLM has lower total losses but higher battery losses than PSPWM. A single-phase 4-SM BI-MMC is used as the experimental platform for the comparison.
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| 16. |
- Balldin, Ulf, et al.
(författare)
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Color vision with rapid-onset acceleration
- 2003
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Ingår i: Aviation, Space and Environmental Medicine. - 0095-6562 .- 1943-4448. ; 74:1, s. 29-36
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Tidskriftsartikel (refereegranskat)
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| 17. |
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| 18. |
- Bergman, Martin, 1985-, et al.
(författare)
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Surface design methodology : challenge the steel
- 2013
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Ingår i: Metrology and Properties of Engineering Surfaces, 2013. - Bristol, UK : Institute of Physics Publishing (IOPP). ; 483:1, s. Art. no. 012013-
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Konferensbidrag (refereegranskat)abstract
- The way a product or material is experienced by its user could be different depending on the scenario. It is also well known that different materials and surfaces are used for different purposes. When optimizing materials and surface roughness for a certain something with the intention to improve a product, it is important to obtain not only the physical requirements, but also the user experience and expectations. Laws and requirements of the materials and the surface function, but also the conservative way of thinking about materials and colours characterize the design of medical equipment. The purpose of this paper is to link the technical- and customer requirements of current materials and surface textures in medical environments. By focusing on parts of the theory of Kansei Engineering, improvements of the companys' products are possible. The idea is to find correlations between desired experience or «feeling» for a product, -customer requirements, functional requirements, and product geometrical properties -design parameters, to be implemented on new improved products. To be able to find new materials with the same (or better) technical requirements but a higher level of user stimulation, the current material (stainless steel) and its surface (brushed textures) was used as a reference. The usage of focus groups of experts at the manufacturer lead to a selection of twelve possible new materials for investigation in the project. In collaboration with the topical company for this project, three new materials that fulfil the requirements -easy to clean and anti-bacterial came to be in focus for further investigation in regard to a new design of a washer-disinfector for medical equipment using the Kansei based Clean ability approach CAA. © Published under licence by IOP Publishing Ltd.
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| 19. |
- Bergström, Göran, 1964, et al.
(författare)
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Body weight at age 20 and in midlife is more important than weight gain for coronary atherosclerosis: Results from SCAPIS.
- 2023
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Ingår i: Atherosclerosis. - : Elsevier BV. - 1879-1484 .- 0021-9150. ; 373, s. 46-54
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Tidskriftsartikel (refereegranskat)abstract
- Elevated body weight in adolescence is associated with early cardiovascular disease, but whether this association is traceable to weight in early adulthood, weight in midlife or to weight gain is not known. The aim of this study is to assess the risk of midlife coronary atherosclerosis being associated with body weight at age 20, body weight in midlife and body weight change.We used data from 25,181 participants with no previous myocardial infarction or cardiac procedure in the Swedish CArdioPulmonary bioImage Study (SCAPIS, mean age 57 years, 51% women). Data on coronary atherosclerosis, self-reported body weight at age 20 and measured midlife weight were recorded together with potential confounders and mediators. Coronary atherosclerosis was assessed using coronary computed tomography angiography (CCTA) and expressed as segment involvement score (SIS).The probability of having coronary atherosclerosis was markedly higher with increasing weight at age 20 and with mid-life weight (p<0.001 for both sexes). However, weight increase from age 20 until mid-life was only modestly associated with coronary atherosclerosis. The association between weight gain and coronary atherosclerosis was mainly seen in men. However, no significant sex difference could be detected when adjusting for the 10-year delay in disease development in women.Similar in men and women, weight at age 20 and weight in midlife are strongly related to coronary atherosclerosis while weight increase from age 20 until midlife is only modestly related to coronary atherosclerosis.
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| 20. |
- Bäckström, David C, M.D. 1978-, et al.
(författare)
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Prediction and early biomarkers of cognitive decline in Parkinson disease and atypical parkinsonism: a population-based study
- 2022
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Ingår i: Brain Communications. - : Oxford University Press (OUP). - 2632-1297. ; 4:2
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Tidskriftsartikel (refereegranskat)abstract
- Backstrom et al. report that, in a population-based cohort of patients with new-onset Parkinson disease, approximately half develop dementia within 10 years. Measurement of CSF biomarkers together with baseline cognitive function, olfaction and motor disease severity has high accuracy for predicting who will develop dementia. The progression of cognitive decline is heterogeneous in the three most common idiopathic parkinsonian diseases: Parkinson disease, multiple system atrophy and progressive supranuclear palsy. The causes for this heterogeneity are not fully understood, and there are no validated biomarkers that can accurately identify patients who will develop dementia and when. In this population-based, prospective study, comprehensive neuropsychological testing was performed repeatedly in new-onset, idiopathic parkinsonism. Dementia was diagnosed until 10 years and participants (N = 210) were deeply phenotyped by multimodal clinical, biochemical, genetic and brain imaging measures. At baseline, before the start of dopaminergic treatment, mild cognitive impairment was prevalent in 43.4% of the patients with Parkinson disease, 23.1% of the patients with multiple system atrophy and 77.8% of the patients with progressive supranuclear palsy. Longitudinally, all three diseases had a higher incidence of cognitive decline compared with healthy controls, but the types and severity of cognitive dysfunctions differed. In Parkinson disease, psychomotor speed and attention showed signs of improvement after dopaminergic treatment, while no such improvement was seen in other diseases. The 10-year cumulative probability of dementia was 54% in Parkinson disease and 71% in progressive supranuclear palsy, while there were no cases of dementia in multiple system atrophy. An easy-to-use, multivariable model that predicts the risk of dementia in Parkinson disease within 10 years with high accuracy (area under the curve: 0.86, P < 0.001) was developed. The optimized model adds CSF biomarkers to four easily measurable clinical features at baseline (mild cognitive impairment, olfactory function, motor disease severity and age). The model demonstrates a highly variable but predictable risk of dementia in Parkinson disease, e.g. a 9% risk within 10 years in a patient with normal cognition and CSF amyloid-beta(42) in the highest tertile, compared with an 85% risk in a patient with mild cognitive impairment and CSF amyloid-beta(42) in the lowest tertile. Only small or no associations with cognitive decline were found for factors that could be easily modifiable (such as thyroid dysfunction). Risk factors for cognitive decline in multiple system atrophy and progressive supranuclear palsy included signs of systemic inflammation and eye movement abnormalities. The predictive model has high accuracy in Parkinson disease and might be used for the selection of patients into clinical trials or as an aid to improve the prevention of dementia.
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| 21. |
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| 22. |
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| 23. |
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| 24. |
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| 25. |
- Ekedahl, Lars-Gunnar, et al.
(författare)
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Hydrogen sensing mechanisms of metal insulator interfaces
- 1998
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Ingår i: Accounts of Chemical Research. - 0001-4842 .- 1520-4898. ; 31:5, s. 249-256
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Tidskriftsartikel (refereegranskat)abstract
- The hydrogen sensitivity of palladium-silicon dioxidesilicon (Pd-MOS) structures was demonstrated about 25 years ago. One of the most interesting features of the Pd-MOS device as a hydrogen sensor is its very large dynamic pressure range. Such devices are now used in several practical applications and in commercially available equipment, both as single sensors and in sensor arrays. We recall that the hydrogen sensitivity of the device occurs due to a hydrogen induced polarization at the Pd-SiO2 interface as schematically shown in Figure 1. During the years, several types of devices have been developed, both with insulators other than silicon dioxide and catalytic metals other than palladium. Furthermore, it has been demonstrated that sensors with thin, discontinuous catalytic metals can detect molecules, like ammonia, which are not detected by sensors with thick continuous palladium gates. 1-3 Although several insulators have been used in hydrogen sensitive Pd-insulator-semiconductor
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| 26. |
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| 27. |
- Eriksson, Lars, 1963-
(författare)
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Age, cognitive load, and multimodal effects on driver response to directional warning
- 2019
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Ingår i: Applied Ergonomics. - : Elsevier. - 0003-6870 .- 1872-9126. ; 76, s. 147-154
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Tidskriftsartikel (refereegranskat)abstract
- Inattention can be considered a primary cause of vehicular accidents or crashes, and in-car warning signals are applied to alert the driver to take action even in automated vehicles. Because of age related decline of the older driver's abilities, in-car warning signals may need adjustment to the older driver. We therefore investigated the effects of uni-, bi- and trimodal directional warnings (i.e., light, sound, vibration) on young and older drivers' responses in a driving simulator. A young group of 15 drivers (20-25 years of age) and an older group of 16 drivers (65-79 years of age) participated. In the simulations, warning signal was presented at the left, the center, or the right in front of the participant. With a warning at the left, the center, and the right the correct response was to steer to the right, brake, and steer to the left, respectively. The main results showed the older drivers' responses were slower for each type of warning compared with the young drivers' responses. Overall, the responses were slower with an added cognitively loading task. The only multimodal type of warning inducing overall faster response than its constituent warning types was the vibration-sound, and only for the older drivers. Additionally, with the groups' responses collapsed, such a true multimodal effect on response time also showed for the center vibration-sound warning (i.e., braking response). The only multimodal warning showing clear reduction in response errors compared with its constituent warning types was the vibration-sound for the older drivers during extra cognitive load. The main conclusion is that older drivers can benefit from bimodal warning, as compared with unimodal, in terms of faster and more accurate response. The potential superiority of trimodal warning is nevertheless argued.
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| 28. |
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| 29. |
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| 30. |
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| 31. |
- Eriksson, Lars, 1963-, et al.
(författare)
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Effects of visual flow display of flight maneuvers on perceived spatial orientation
- 2005
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Ingår i: Human Factors. - 0018-7208 .- 1547-8181. ; 47:2, s. 378-393
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Tidskriftsartikel (refereegranskat)abstract
- Postural responses were utilized as measures of the effectiveness of a wide-angle visual flow display in determining perceived spatial orientation (SO). The general experimental setup included a 150 degrees x 34 degrees wide-field display showing flight over computer-generated ground with horizon. Simulated roll maneuvers on this display induced postural sway in the observer that was registered by a head-tracker system. Two experiments with 16 participants in each investigated the effects of visual flow, display exclusions in the central visual field, and display extensions into the visual periphery. Clear vestibular and proprioceptive suppression effects were demonstrated on postural sway with the inclusion of visual flow of forward ego motion in roll maneuvers. Compared with the full view, up to 20 degrees x 20 degrees central field omission either did not reduce the effect or reduced the effect but, frequently, only moderately. Limiting the display area to 45 degrees in the horizontal dimension reduced display effectiveness significantly, whereas a 105 degrees area did not, compared with the full view. Utilizing postural responses as indications of visual display resonance with our SO mechanism, actual or potential applications of this research include the design of an interface integrating flight-adapted visual flow to counteract or reduce pilot spatial disorientation.
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| 32. |
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| 33. |
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| 34. |
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| 35. |
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| 36. |
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| 37. |
- Eriksson, Lars, 1963-
(författare)
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Toward a Visual Flow Integrated Display Format to Combat Pilot Spatial Disorientation
- 2010
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Ingår i: The International journal of aviation psychology. - Philadelphia : Taylor & Francis. - 1050-8414 .- 1532-7108. ; 20:1, s. 1-24
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Tidskriftsartikel (refereegranskat)abstract
- Aiming to ascertain basic display guidelines for improved support of pilot spatial orientation (SO), the visual resonance with the perceptual mechanism for SO was explored in two experiments. Postural responses indicated the efficiency of visual cues to control proprioception and equilibrium sense. A display design is suggested which integrates the results with the concepts for an operational head-up display symbology. By means of improved perception of integrated pitch, roll, and yaw information and resonance of synthetic visual flow with the SO mechanism, the design may in the future contribute to combating pilot spatial disorientation.
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| 38. |
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| 39. |
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| 40. |
- Eriksson, Lars, 1963-
(författare)
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Visual Flow Display for Pilot Spatial Orientation
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Pilot spatial disorientation (SD) is a significant cause of incidents and fatal accidents in aviation. The pilot is susceptible to SD especially in low visibility when the visual system is deprived of information from outside the cockpit. This thesis presents the notion of visual flow displays as enhancement of symbology on flight displays primarily in low visibility for improved support of the pilot’s spatial orientation (SO) and control actions. In Studies I and II, synthetic visual flow of forward ego-motion was presented on displays and postural responses were used as measures of display effectiveness in determining SO. The visual flow significantly affected SO, and although the increased stimulation of the visual periphery from a width of 45° to about 105° increased the effects there was no further effect at a width of about 150° (Studies I and II). Studies I and II also showed that omitting 20°- or 30°-wide central fields of view from the visual flow either reduced or not reduced the effects. Further, although inconclusive, Study II may indicate that horizon symbology in central visual field may enhance the effects of peripheral visual flow. The appropriate integration of peripheral visual flow with the head-up display symbology of the Gripen aircraft was presented. Acceleration in a human centrifuge was used in Study III to investigate the effects of synthetic visual flow on the primarily vestibular-dependent somatogravic illusion of pitch-up. Two experiments revealed a reduced illusion with the visual flow. The results of Experiment 2 showed the visual flow scene not only reduced the illusion compared with a darkness condition but also compared with the visual scene without visual flow. Thus, similar to the main findings of Studies I and II, synthetic visual flow can significantly affect SO and supports the visually dependent SO system in an essential manner.
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| 41. |
- Eriksson, Lars, 1963-, et al.
(författare)
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Visual flow scene effects on the somatogravic illusion in non-pilots
- 2008
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Ingår i: Aviation, Space and Environmental Medicine. - 0095-6562 .- 1943-4448. ; 79:9, s. 860-866
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: The somatogravic illusion (SGI) is easily broken when the pilot looks out the aircraft window during daylight flight, but it has proven difficult to break or even reduce the SGI in non-pilots in simulators using synthetic visual scenes. Could visual-flow scenes that accommodate compensatory head movement reduce the SGI in naive subjects? Methods: We investigated the effects of visual cues on the SGI induced by a human centrifuge. The subject was equipped with a head-tracked, head-mounted display (HMD) and was seated in a fixed gondola facing the center of rotation. The angular velocity of the centrifuge increased from near zero until a 0.57-G centripetal acceleration was attained, resulting in a tilt of the gravitoinertial force vector, corresponding to a pitch-up of 30 degrees. The subject indicated perceived horizontal continuously by means of a manual adjustable-plate system. We performed two experiments with within-subjects designs. In Experiment 1, the subjects (N = 13) viewed a darkened TIMID and a presentation of simple visual flow beneath a horizon. In Experiment 2, the subjects (N = 12) viewed a darkened HMD, a scene including symbology superimposed on simple visual flow and horizon, and this scene without visual flow (static). Results: In Experiment 1, visual flow reduced the SGI from 12.4 +/- 1.4 degrees (mean +/- SE) to 8.7 +/- 1.5 degrees. In Experiment 2, the SGI was smaller in the visual flow condition (9.3 +/- 1.8 degrees) than with the static scene (13.3 +/- 1.7 degrees) and without HMD presentation (14.5 +/- 2.3 degrees), respectively. Conclusion: It is possible to reduce the SGI in non-pilots by means of a synthetic horizon and simple visual flow conveyed by a head-tracked HMD. This may reflect the power of a more intuitive display for reducing the SGI.
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| 42. |
- Eriksson, Mats, 1963-, et al.
(författare)
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A model of the Temkin isotherm behaviour for hydrogen adsorption at Pd-SiO2 interfaces
- 1997
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 82:6, s. 3143-3146
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Tidskriftsartikel (refereegranskat)abstract
- A simple electrostatic model of the adsorbate–adsorbateinteraction of hydrogen atoms at a Pd–SiO 2 interface is presented. The model predicts a hydrogen adsorption isotherm of the Temkin type. It is found that, in practice, an upper limit for the hydrogen response of a Pd-metal-oxide-semiconductor device exists. The value (in V) is equal to the difference of the initial heats of adsorption (in eV) of the interface and the Pd bulk, respectively. Furthermore, a corresponding maximum hydrogen concentration, at the interface, of 1×10 18 m −2 is predicted. The predictions are in good agreement with previously observed experimental data.
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| 43. |
- Eriksson, Mats, 1963-, et al.
(författare)
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Hydrogen adsorption states at the Pd-SiO2 interface and simulation of the response of a Pd metal-oxide-semiconductor hydrogen sensor
- 1998
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 83:8, s. 3947-3951
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Tidskriftsartikel (refereegranskat)abstract
- The response of a Pd–SiO 2 –Si hydrogen sensor depends on the reaction kinetics of hydrogen on the Pd surface and on the hydrogen adsorption states at the Pd/SiO 2 interface. In this work we show that besides the dominating hydrogen adsorption state located on the oxide side of the interface, a second state, resulting in opposite hydrogen polarization, exists. This state is possibly a reminiscence of the hydrogen adsorption state on a clean Pd surface. Taking both states into account, a simulation of the hydrogen response over more than ten decades in hydrogen pressures gives good agreement with published data.
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| 44. |
- Eriksson, Mats, 1963-, et al.
(författare)
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Real time measurements of hydrogen desorption and absorption during CO exposures of Pd: Hydrogen sticking and dissolution
- 1998
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Ingår i: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 133:1-2, s. 89-97
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Tidskriftsartikel (refereegranskat)abstract
- Combined real time measurements of hydrogen desorption and absorption show that both processes may be induced simultaneously by CO adsorption on a hydrogen-covered Pd surface. The induced absorption is found to be a kinetic effect, where the amount absorbed depends on the hydrogen desorption rate and the CO adsorption rate. In addition to simple site blocking, adsorbed CO induces an increase in the hydrogen desorption energy and an activation barrier for hydrogen dissociation. Both increase linearly with CO coverage for θCO>0.18 ML. Below this coverage, the hydrogen dissociation is non-activated.
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| 45. |
- Eriksson, Mats, 1963-, et al.
(författare)
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Spillover of hydrogen, oxygen and carbon monoxide in oxidation reactions on SiO2 supported Pd
- 1994
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 311:1-2, s. 139-152
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Tidskriftsartikel (refereegranskat)abstract
- Oxidation of H2 and CO on large, oxygen preexposed Pd islands supported on SiO2, has been investigated in the temperature range 323 ⩽, T ⩽ 523 K. The results have been compared with the corresponding reactions on a polycrystalline Pd film. A maximum reactive sticking coefficient of 0.9 for H2 and an initial sticking coefficient for O2 of 0.8 on both structures is concluded. The maximum reactive sticking coefficient for CO is 0.85 on the film and apparently larger than unity on the island structure. The results obtained from the island structure can be rationalized if O2 and H2 dissociate on the Pd islands and have the possibility to spillover onto the oxide, while CO adsorbs and reacts both on the Pd islands and on the oxide. Spillover of oxygen occurs in a precursor state and is irreversible with an apparent activation energy of 0.1 eV for the forward reaction.
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| 46. |
- Eriksson, Mats, 1963-, et al.
(författare)
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The catalytic oxidation of CO on polycrystalline Pd: Experiments and kinetic modelling
- 1998
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Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 412/413, s. 430-440
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Tidskriftsartikel (refereegranskat)abstract
- The catalytic oxidation of CO on a thin, polycrystalline Pd film has been studied. Even though the Pd film is expected to be dominated by (111) facets, some distinct differences compared to single crystalline Pd(111) are observed. A kinetic model for the CO oxidation reaction is presented. It gives good agreement with experiments, both in terms of CO2 reaction probability and CO coverage during reaction conditions. The model assumes a random distribution of the adsorbates, an activation energy for the reaction that decreases with increasing CO coverage, as well as a CO sticking coefficient that in a temperature dependent fashion depends on the oxygen coverage. Single crystal data available from the literature (initial sticking coefficients and heats of adsorption) were mainly used as input parameters. Thus, the model might also be a useful starting point when modeling the catalytic oxidation of CO on single crystal surfaces.
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| 47. |
- Eriksson, Mats, 1963-, et al.
(författare)
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The influence of CO on the response of hydrogen sensitive Pd-MOS devices
- 1997
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Ingår i: Sensors and actuators. B, Chemical. - 0925-4005 .- 1873-3077. ; 42:3, s. 217-223
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Tidskriftsartikel (refereegranskat)abstract
- In order to understand and correctly interpret the response of chemical sensors under measurement conditions, detailed studies of molecule—sensor interactions under well-controlled conditions are needed. In this work, the influence of CO on the response of a hydrogen sensitive Pd—metal-oxide-semiconductor (Pd—MOS) device with a dense Pd film is studied in ultrahigh vacuum (UHV). The results show that although CO by itself does not induce any response of the device, CO may have a significant influence on the hydrogen response, especially so in the presence of oxygen. It is also shown that high CO coverages on the Pd surface increases the time needed to obtain equilibrium between the gas phase hydrogen pressure and the response of the Pd—MOS device. This is due to a CO induced increase of the activation energies of the dissociation and association processes for hydrogen. The effect on the hydrogen response is small for CO coverages below 0.2 monolayers and increases dramatically above this coverage.
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| 48. |
- Eriksson, Stefan, 1963-, et al.
(författare)
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Autonomi och religion - Jehovas vittnen och blodtransfusioner
- 2001
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Ingår i: Socialmedicinsk Tidskrift. - 0037-833X. ; 78:5, s. 436-448
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Tidskriftsartikel (refereegranskat)abstract
- I denna artikel diskuteras utförligt de problem som uppkommer när Jehovas vittnen vägrar ta emot blod. Särskilt argumenteras för ett starkt autonomibegrepp och för det lämpliga i att vårdpersonal med vittnen diskuterar samfundets grundläggande religiösa argument för att vägra transfunderat blod.
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| 49. |
- Eriksson, Stefan, Docent, 1963-, et al.
(författare)
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How to counter undeserving authorship
- 2018
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Ingår i: Insights: the UKSG journal. - Witney, UK : UKSG & Ubiquity Press. - 2048-7754. ; 31:1, s. 1-6
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Tidskriftsartikel (refereegranskat)abstract
- The average number of authors listed on contributions to scientific journals has increased considerably over time. While this may be accounted for by the increased complexity of much research and a corresponding need for extended collaboration, several studies suggest that the prevalence of non-deserving authors on research papers is alarming. In this paper a combined qualitative and quantitative approach is suggested to reduce the number of undeserving authors on academic papers: 1) ask scholars who apply for positions to explain the basics of a random selection of their co-authored papers, and 2) in bibliometric measurements, divide publications and citations by the number of authors.
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| 50. |
- Eriksson, Stefan, 1963-, et al.
(författare)
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Samtal måste föras! : Autonomi i fallet Jehovas vittnen och blodtransfusioner
- 2002
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Ingår i: Läkartidningen. ; 99:4, s. 321-322
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- En sammanfattning av artikeln "Autonomi och religion - Jehovas vittnen och blodtransfusioner" skriven i debattartikelns form. Argumenterar för vikten av att vårdpersonal med vittnen diskuterar grunderna - även de religiösa - för att vägra ta emot blod.
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