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Träfflista för sökning "WFRF:(Eriksson Fredrik 1975 ) "

Sökning: WFRF:(Eriksson Fredrik 1975 )

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1.
  • Landälv, Ludvig, 1982-, et al. (författare)
  • Phase evolution of radio frequency magnetron sputtered Cr-rich (Cr,Zr)(2)O-3 coatings studied by in situ synchrotron X-ray diffraction during annealing in air or vacuum
  • 2019
  • Ingår i: Journal of Materials Research. - : CAMBRIDGE UNIV PRESS. - 0884-2914 .- 2044-5326. ; 34:22, s. 3735-3746
  • Tidskriftsartikel (refereegranskat)abstract
    • The phase evolution of reactive radio frequency (RF) magnetron sputtered Cr0.28Zr0.10O0.61 coatings has been studied by in situ synchrotron X-ray diffraction during annealing under air atmosphere and vacuum. The annealing in vacuum shows t-ZrO2 formation starting at similar to 750-800 degrees C, followed by decomposition of the alpha-Cr2O3 structure in conjunction with bcc-Cr formation, starting at similar to 950 degrees C. The resulting coating after annealing to 1140 degrees C is a mixture of t-ZrO2, m-ZrO2, and bcc-Cr. The air-annealed sample shows t-ZrO2 formation starting at similar to 750 degrees C. The resulting coating after annealing to 975 degrees C is a mixture of t-ZrO2 and alpha-Cr2O3 (with dissolved Zr). The microstructure coarsened slightly during annealing, but the mechanical properties are maintained, with no detectable bcc-Cr formation. A larger t-ZrO2 fraction compared with alpha-Cr2O3 is observed in the vacuum-annealed coating compared with the air-annealed coating at 975 degrees C. The results indicate that the studied pseudo-binary oxide is more stable in air atmosphere than in vacuum.
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2.
  • Broekhuijsen, Sjoerd, 1993-, et al. (författare)
  • Synthesis and characterization of 11B4C containing Ni/Ti multilayers using combined neutron and X-ray reflectometry
  • 2023
  • Ingår i: Optical Materials Express. - : Optica Publishing Group. - 2159-3930 .- 2159-3930. ; 13:4, s. 1140-1149
  • Tidskriftsartikel (refereegranskat)abstract
    • The performance of multilayers in optical components, such as those used in neutron scattering instruments, is crucially dependent on the achievable interface width. We have shown how the interface width of Ni/Ti multilayers can be improved using the incorporation of B4C to inhibit the formation of nanocrystals and limit interdiffusion and intermetallic reactions at the interfaces. A modulated ion-assistance scheme was used to prevent intermixing and roughness accumulation throughout the layer stack. In this work we investigate the incorporation of low-neutron-absorbing 11B4C for Ni/Ti neutron multilayers. Combined fitting of neutron reflectivity and X-ray reflectivity measurements shows an elimination of accumulated roughness for the 11B4C containing multilayers with a mean interface width of 4.5 Å, resulting in an increase in reflectivity at the first Bragg peak by a factor of 2.3 and 1.5 for neutron and X-ray measurements, respectively.
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3.
  • Chang, Jui-Che, et al. (författare)
  • Domain epitaxial growth of Ta3N5 film on c-plane sapphire substrate
  • 2022
  • Ingår i: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 443
  • Tidskriftsartikel (refereegranskat)abstract
    • Tritantalum pentanitride (Ta3N5) semiconductor is a promising material for photoelectrolysis of water with high efficiency. Ta3N5 is a metastable phase in the complex system of TaN binary compounds. Growing stabilized single-crystal Ta3N5 films is correspondingly challenging. Here, we demonstrate the growth of a nearly single-crystal Ta3N5 film with epitaxial domains on c-plane sapphire substrate, Al2O3(0001), by magnetron sputter epitaxy. Introduction of a small amount ~2% of O2 into the reactive sputtering gas mixed with N2 and Ar facilitates the formation of a Ta3N5 phase in the film dominated by metallic TaN. In addition, we indicate that a single-phase polycrystalline Ta3N5 film can be obtained with the assistance of a Ta2O5 seed layer. With controlling thickness of the seed layer smaller than 10 nm and annealing at 1000 °C, a crystalline β phase Ta2O5 was formed, which promotes the domain epitaxial growth of Ta3N5 films on Al2O3(0001). The mechanism behind the stabilization of the orthorhombic Ta3N5 structure resides in its stacking with the ultrathin seed layer of orthorhombic β-Ta2O5, which is energetically beneficial and reduces the lattice mismatch with the substrate.
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4.
  • Chang, Jui-Che, et al. (författare)
  • Orthorhombic Ta3-xN5-yOy thin films grown by unbalanced magnetron sputtering : The role of oxygen on structure, composition, and optical properties
  • 2021
  • Ingår i: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 406
  • Tidskriftsartikel (refereegranskat)abstract
    • Direct growth of orthorhombic Ta3N5-type Ta-O-N compound thin films, specifically Ta3-xN5-yOy, on Si and sapphire substrates with various atomic fractions is realized by unbalanced magnetron sputtering. Low-degree fiber-textural Ta3-xN5-yOy films were grown through reactive sputtering of Ta in a gas mixture of N-2, Ar, and O-2 with keeping a partial pressure ratio of 3:2:0.1 in a total working pressure range of 5-30 mTorr. With increasing total pressure from 5 to 30 mTorr, the atomic fraction of O in the as-grown Ta3-xN5-yOy films was found to increase from 0.02 to 0.15 while that of N and Ta decrease from 0.66 to 0.54 and 0.33 to 0.31, respectively, leading to a decrease in b lattice constant up to around 1.3%. Metallic TaNx phases were formed without oxygen. For a working pressure of 40 mTorr, an amorphous, O-rich Ta-N-O compound film with a high O fraction of similar to 0.48, was formed, mixed with non-stoichiometric TaON and Ta2O5. By analyzing the plasma discharge, the increasing O incorporation is associated with oxide formation on top of the Ta target due to a higher reactivity of Ta with O than with N. The increase of O incorporation in the films also leads to a optical bandgap widening from similar to 2.22 to similar to 2.96 eV, which is in agreement with the compositional and structural changes from a crystalline Ta3-xN5-yOy to an amorphous O-rich Ta-O-N compound.
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5.
  • Dorri, Samira, 1988-, et al. (författare)
  • Enhanced quality of single crystal CrBx/TiBy diboride superlattices by controlling boron stoichiometry during sputter deposition
  • 2024
  • Ingår i: Applied Surface Science. - : Elsevier. - 0169-4332 .- 1873-5584.
  • Tidskriftsartikel (refereegranskat)abstract
    • Single-crystal CrB2/TiB2 diboride superlattices with well-defined layers are promising candidates for neutron optics. However, excess B in sputter-deposited TiBy using a single TiB2 target deteriorates the structural quality of CrBx/TiBy (0001) superlattices. We study the influence of co-sputtering of TiB2 + Ti on the stoichiometry and crystalline quality of 300-nm-thick TiBy single layers and CrBx/TiBy (0001) superlattices on Al2O3(0001) substrates grown by DC magnetron sputter epitaxy at growth-temperatures TS ranging from 600 to 900 °C. By controlling the relative applied powers to the TiB2 and Ti magnetrons, y could be reduced from 3.3 to 0.9. TiB2.3 grown at 750 °C exhibited epitaxial domains about 10x larger than non-co-sputtered films. Close-to-stoichiometry CrB1.7/TiB2.3 superlattices with modulation periods Λ = 6 nm grown at 750 °C showed the highest single crystal quality and best layer definition. TiB2.3 layers display rough top interfaces indicating kinetically limited growth while CrB1.7 forms flat and abrupt top interfaces indicating epitaxial growth with high adatom mobility.
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6.
  • Eriksson, Fredrik, 1975-, et al. (författare)
  • Interface engineering of short-period Ni/V multilayer X-ray mirrors
  • 2006
  • Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 500:1-2, s. 84-95
  • Tidskriftsartikel (refereegranskat)abstract
    • Low-energy ion-assisted magnetron sputter deposition has been used for the synthesis of highly reflective Ni/V multilayer soft X-ray mirrors. A low ion energy and a high ion-to-metal flux ratio were employed in order to stimulate the adatom mobility while minimizing ion-induced intermixing at the interfaces. An analytic model, based on the binary collision approximation, was used in order to gain insight into low-energy ion-surface interactions as a function of ion energy and ion-to-metal flux ratio. The model predicted a favorable region in the ion energy-flux parameter space where only surface atomic displacements are stimulated during growth of Ni and V for multilayers. For a series of Ni/V multilayer mirrors with multilayer periods about Λ = 1.2 nm, grown with a continuous ion assistance using energies in the range 7-36 eV and with ion-to-metal flux ratios ΦNi = 4.7 and ΦV=20.9, specular and diffuse X-ray scattering analyses revealed that ion energies of ∼27-31 eV produced the best trade-off between reduced interfacial roughness and intermixing. However, it was also concluded that an interface mixing of about ± 1 atomic distance is unavoidable when a continuous flux of assisting ions is used. To overcome this limitation, a sophisticated interface engineering technique was employed, where the first 0.3 nm of each layer was grown with a high-flux low-energy ion assistance and the remaining part was grown with a slightly higher ion energy. This method was demonstrated to largely eliminate the intermixing while maintaining the smoothening effect of ion assistance. Two Ni/V multilayer soft X-ray mirror structures, one with 500 periods designed for near-normal incidence and one 150 periods reflecting polarizer at the Brewster angle, were grown utilizing the interface engineering concept. Both the near-normal incidence reflectivity as well as polarizability were improved by a factor of 2 as compared to previously reported data for an X-ray energy of E = 511 eV. © 2005 Elsevier B.V. All rights reserved.
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7.
  • Eriksson, Fredrik, 1975-, et al. (författare)
  • Morphology control in Ni/Ti multilayer neutron mirrors by ion-assisted interface engineering and B4C incorporation
  • 2023
  • Ingår i: Optical Materials Express. - : Optica Publishing Group. - 2159-3930 .- 2159-3930. ; 13:5, s. 1424-1439
  • Tidskriftsartikel (refereegranskat)abstract
    • The optical contrast and minimum layer thickness of Ni/Ti broadband neutron multilayer supermirrors is usually hampered by an interface width, typically 0.7 nm, caused by nanocrystallites, interdiffusion, and/or intermixing. We explore the elimination of nanocrystallites in combination with interface smoothening by modulation of ion assistance during magnetron sputter deposition of 0.8 to 6.4 nm thick Ni and Ti layers. The amorphization is achieved through incorporation of natural B4C where B and C preferably bond to Ti. A two-stage substrate bias was applied to each layer; -30 V for the initial 1 nm followed by -100 V for the remaining part, generating multilayer mirrors with interface widths of 0.40-0.45 nm. The results predict that high performance supermirrors with m-values as high as 10 are feasible by using 11B isotope-enriched B4C combined with temporal control of the ion assistance.
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8.
  • Ghafoor, Naureen, 1975-, et al. (författare)
  • Impact of B4C co-sputtering on structure and optical performance of Cr/Sc multilayer X-ray mirrors
  • 2017
  • Ingår i: Optics Express. - : Optical Society of America. - 1094-4087. ; 25:15, s. 18274-18287
  • Tidskriftsartikel (refereegranskat)abstract
    • The influence of B4C incorporation during magnetron sputter deposition of Cr/Sc multilayers intended for soft X-ray reflective optics is investigated. Chemical analysis suggests formation of metal: boride and carbide bonds which stabilize an amorphous layer structure, resulting in smoother interfaces and an increased reflectivity. A near-normal incidence reflectivity of 11.7%, corresponding to a 67% increase, is achieved at λ = 3.11 nm upon adding 23 at.% (B + C). The advantage is significant for the multilayer periods larger than 1.8 nm, where amorphization results in smaller interface widths, for example, giving 36% reflectance and 99.89% degree of polarization near Brewster angle for a multilayer polarizer. The modulated ion-energy-assistance during the growth is considered vital to avoid intermixing during the interface formation even when B + C are added.
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9.
  • Zubayer, Anton, 1995- (författare)
  • Enhanced Polarizing Neutron Optics with 11B4C Incorporation : SLD Tunability, Interface Refinement, and Elimination of Magnetic Coercivity
  • 2023
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • This thesis explores novel strategies for improving Fe-based polarizing neutron optics, a critical part for improving neutron scattering methods to study materials science, physics, biology, medicine, chemistry and cultural heritage. Polarization analysis is important in uncovering data on magnetic domains, protein structures, molecular composition and orientation in biological systems, and ion-diffusion mechanisms that would otherwise be inaccessible. However, conventional methods, particularly state-of-the-art multilayer polarizing neutron optics, are hindered by low specular reflectivity, low polarization at higher scattering vectors/angles, high diffuse scattering and the need for high external magnetic fields for polarizer magnetization.  The outcomes leading to this thesis, introduces the concept of scattering length density tuning, strategies to decrease the interface width, the diminishing of lateral correlation and magnetic coercivity. All improvements realized by introducing 11B4C in clever ways.The multilayers were deposited using ion-assisted DC magnetron sputter deposition (DCMS). Our improvement of Fe-based multilayer mirrors all revolves around the use of 11B4C. 11B4C in various concentrations can be used together with other materials to tune the scattering length density contrasts. It can amorphize the interfaces and layers to achieve smaller interface width, diminish lateral correlations and eliminate magnetic coercivity. In other words, increase reflectivity, increase polarization, decrease diffuse scattering and saturate at lower fields.   The multilayers were mainly characterized using X-ray reflectivity (XRR), X-ray diffraction (XRD), grazing incidence small/wide angle X-ray scattering (GISAXS/GIWAXS), elastic recoil detection analysis (ERDA), magneto-optical Kerr effect (MOKE), vibrating sample magnetometry (VSM), transmission electron microscopy (TEM) and polarized neutron reflectivity (PNR).  All results prove the benefit of using 11B4C in Fe-based polarizing neutron optics.   
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10.
  • Ahrentorp, Fredrik, et al. (författare)
  • Sensitive magnetic biodetection using magnetic multi-core nanoparticles and RCA coils
  • 2017
  • Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853 .- 1873-4766. ; 427, s. 14-18
  • Tidskriftsartikel (refereegranskat)abstract
    • We use functionalized iron oxide magnetic multi-core particles of 100 nm in size (hydrodynamic particle diameter) and AC susceptometry (ACS) methods to measure the binding reactions between the magnetic nanoparticles (MNPs) and bio-analyte products produced from DNA segments using the rolling circle amplification (RCA) method. We use sensitive induction detection techniques in order to measure the ACS response. The DNA is amplified via RCA to generate RCA coils with a specific size that is dependent on the amplification time. After about 75 min of amplification we obtain an average RCA coil diameter of about 1 mu m. We determine a theoretical limit of detection (LOD) in the range of 11 attomole (corresponding to an analyte concentration of 55 fM for a sample volume of 200 mu L) from the ACS dynamic response after the MNPs have bound to the RCA coils and the measured ACS readout noise. We also discuss further possible improvements of the LOD.
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11.
  • Bergström, Fredrik, 1983-, et al. (författare)
  • Neural evidence for non-conscious working memory
  • 2018
  • Ingår i: Cerebral Cortex. - : Oxford University Press. - 1047-3211 .- 1460-2199. ; 28:9, s. 3217-3228
  • Tidskriftsartikel (refereegranskat)abstract
    • Recent studies have found that non-consciously perceived information can be retained for several seconds, a feat that has been attributed to non-conscious working memory processes. However, these studies have mainly relied on subjective measures of visual experience, and the neural processes responsible for non-conscious short-term retention remains unclear. Here we used continuous flash suppression to render stimuli non-conscious in a delayed match-to-sample task together with fMRI to investigate the neural correlates of non-conscious short-term (5-15 s) retention. The participants' behavioral performance was at chance level when they reported no visual experience of the sample stimulus. Critically, multivariate pattern analyses of BOLD signal during the delay phase could classify presence versus absence of sample stimuli based on signal patterns in frontal cortex, and its spatial position based on signal patterns in occipital cortex. In addition, univariate analyses revealed increased BOLD signal change in prefrontal regions during memory recognition. Thus, our findings demonstrate short-term maintenance of information presented non-consciously, defined by chance performance behaviorally. This non-consciously retained information seems to rely on persistent neural activity in frontal and occipital cortex, and may engage further cognitive control processes during memory recognition.
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12.
  • Bergström, Fredrik, 1983-, et al. (författare)
  • The conjunction of non-consciously perceived object identity and spatial position can be retained during a visual short-term memory task
  • 2015
  • Ingår i: Frontiers in Psychology. - : Frontiers Media S.A.. - 1664-1078. ; 6
  • Tidskriftsartikel (refereegranskat)abstract
    • Although non-consciously perceived information has previously been assumed to be short-lived (<500 ms), recent findings show that non-consciously perceived information can be maintained for at least 15s Such findings can be explained as working memory without a conscious experience of the information to be retained. However, whether or not working memory can operate on non-consciously perceived information remains controversial, and little is known about the nature of such non-conscious visual short-term memory (VSTM). Here we used continuous flash suppression to render stimuli non-conscious, to investigate the properties of non-consciously perceived representations in delayed match-to-sample (DMS) tasks. In Experiment I we used variable delays (5 or 15s) and found that performance was significantly better than chance and was unaffected by delay duration, thereby replicating previous findings. In Experiment II the DMS task required participants to combine information of spatial position and object identity on a trial-by-trial basis to successfully solve the task. We found that the conjunction of spatial position and object identity was retained, thereby verifying that non-conscious, trial-specific information can be maintained for prospective use. We conclude that our results are consistent with a working memory interpretation, but that more research is needed to verify this interpretation.
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13.
  • Berndt, Sonja I., et al. (författare)
  • Genome-wide meta-analysis identifies 11 new loci for anthropometric traits and provides insights into genetic architecture
  • 2013
  • Ingår i: Nature Genetics. - : Springer Science and Business Media LLC. - 1061-4036 .- 1546-1718. ; 45:5, s. 501-U69
  • Tidskriftsartikel (refereegranskat)abstract
    • Approaches exploiting trait distribution extremes may be used to identify loci associated with common traits, but it is unknown whether these loci are generalizable to the broader population. In a genome-wide search for loci associated with the upper versus the lower 5th percentiles of body mass index, height and waist-to-hip ratio, as well as clinical classes of obesity, including up to 263,407 individuals of European ancestry, we identified 4 new loci (IGFBP4, H6PD, RSRC1 and PPP2R2A) influencing height detected in the distribution tails and 7 new loci (HNF4G, RPTOR, GNAT2, MRPS33P4, ADCY9, HS6ST3 and ZZZ3) for clinical classes of obesity. Further, we find a large overlap in genetic structure and the distribution of variants between traits based on extremes and the general population and little etiological heterogeneity between obesity subgroups.
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14.
  • Broekhuijsen, Sjoerd, 1993- (författare)
  • 11B4C containing Ni/Ti neutron multilayer mirrors
  • 2021
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The work in this thesis covers the design, growth and characterisation of neutron multilayers. The performance of these multilayers is highly dependent on the obtained interface width between the layers, even a modest improvement can offer a substantial increase in reflectivity performance. As multilayers are such an integral component of many neutron optical instruments, any improvement in terms of reflectivity performance has broad implications for all neutron scattering experiments. This project has been carried out with the construction of the European Spallation Source (ESS) in mind, but the principles extend to all neutron scattering sources.Ni/Ti is the conventional material system of choice for neutron optical components due to the high contrast in scattering length density (SLD). The reflected intensity of such components is largely dependent on the interface width, caused by the formation of nanocrystallites, interdiffusion, and/or intermixing. Apart from hampering the reflectivity performance, the finite interface width between the layers also limits the minimum usable layer thickness in the mirror stack. The formation of nanocrystallites has been eliminated by co-depositing of B4C . This has been combined with a modulated ion assistance scheme to smoothen the interfaces. X-ray reflectivity (XRR) measurements show significantly improvements compared to pure Ni/Ti multilayers. This has further been investigated using low neutron-absorbing 11B4C instead. After deposition, the 11B4C containing films have been characterized using neutron reflectometry, X-ray reflectivity, transmission electron microscopy, elastic recoil detection analysis, X-ray photoelectron spectroscopy. A large part of his work has focused on fitting X-ray and neutron reflectivity measurements in order to obtain structural parameters.The fits to the experimental data suggest a significant improvement in interface width for the samples that have been co-deposited with 11B4C using a modulated ion assistance scheme during deposition. Any accumulation of roughness has been eliminated, and the average initial interface width at the first bilayer has been reduced from 6.3 Å to 4.5 Å per bilayer. The respective reflectivity performance for these structural parameters have been simulated for a neutron supermirror (N = 5000) for both materials at a neutron wavelength at λ = 3 Å using the IMD software. The predicted reflectivity performance for the 11B4C containing samples amounts to about 71%, which is a significant increase compared to the pure Ni/Ti samples which have a predicted reflectivity of 62%. This results in a reflectivity increase from 0.84% to 3.3% after a total of 10 reflections, resulting in more than 400% higher neutron flux at experiment.
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15.
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16.
  • Ekström, Erik, 1989-, et al. (författare)
  • Epitaxial Growth of CaMnO3-y Films on LaAlO3 (112 over bar 0) by Pulsed Direct Current Reactive Magnetron Sputtering
  • 2022
  • Ingår i: Physica Status Solidi. Rapid Research Letters. - : Wiley-V C H Verlag GMBH. - 1862-6254 .- 1862-6270. ; 16:4
  • Tidskriftsartikel (refereegranskat)abstract
    • CaMnO3 is a perovskite with attractive magnetic and thermoelectric properties. CaMnO3 films are usually grown by pulsed laser deposition or radio frequency magnetron sputtering from ceramic targets. Herein, epitaxial growth of CaMnO3-y (002) films on a (112 over bar 0)-oriented LaAlO3 substrate using pulsed direct current reactive magnetron sputtering is demonstrated, which is more suitable for industrial scale depositions. The CaMnO3-y shows growth with a small in-plane tilt of <approximate to 0.2 degrees toward the (200) plane of CaMnO3-y and the (1 over bar 104) with respect to the LaAlO3 (112 over bar 0) substrate. X-ray photoelectron spectroscopy of the electronic core levels shows an oxygen deficiency described by CaMnO2.58 that yields a lower Seebeck coefficient and a higher electrical resistivity when compared to stoichiometric CaMnO3. The LaAlO3 (112 over bar 0) substrate promotes tensile-strained growth of single crystals. Scanning transmission electron microscopy and electron energy loss spectroscopy reveal antiphase boundaries composed of Ca on Mn sites along and , forming stacking faults.
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17.
  • Ekström, Erik, 1989- (författare)
  • Epitaxial growth, structure, and thermoelectric properties of CaMn- and V-based oxides
  • 2021
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • This thesis is focused on physical vapor deposition, epitaxy, and structural characterization of CaMnO3 and VO2. Environmentally friendly and abundant materials are important for energy savings in applications, e.g., thermoelectrics for waste-heat recycling and thermochromic materials for passive indoor-temperature regulation. CaMnO3 is thermoelectric and VO2 is thermochromic at attractive temperatures for waste heat recycling and passive indoor-temperature regulation, respectively. The two material systems in this thesis were grown by reactive magnetron sputtering. A two-step synthesis process was investigated where rock-salt (Ca,Mn)O was grown by sputtering followed by an annealing step to form the perovskite CaMnO3. CaMnO3 was alloyed with Nb with the purpose to enhance the thermoelectric properties by increasing the number of free carriers, resulting in CaMn1-xNbxO3 (x = 0 – 0.10) films. CaMnO3 was grown on Al2O3 and LaAlO3 while VO2 was grown on muscovite (mica), phase-pure films of the metastable B phase and the stable M1 phase could be grown by controlling the gas flow and pressure. The mica substrate is a material with weakly interacting van der Waals layers in the structure that enable van der Waals epitaxy for the stable VO2 film in M1 phase. The thickness effect on electrical properties in the thermochromic region was investigated as well as proving van der Waals epitaxy. This thesis therefore provides an overall contribution to the understanding of film structure and the control thereof and how it affects the properties of the film.
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18.
  • Ekström, Erik, 1989- (författare)
  • Growth and thermoelectric properties of CaMnO3-based thin films
  • 2018
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The field of them1oelectrics started in early 19th century. Since the discovery of the Seebeck effect and the Peltier effect, thermoelectric modules have found their way into, mostly, niche applications such as radioisotope thermoelectric generators on space missions. Thermoelectric modules can also be used for cooling, utilizing the Peltier effect.Thermoelectrics are promising materials due to the operation nature of the modules. That is, they have no moving parts, no exhaust, long lifetime without maintenance, features that make them attractive for many applications. Despite these promising properties, thermoelectric modules are mostly used in niche applications. The main reason for this is conventional modules with the highest efficiency are commonly made of expensive and/or rare elements which prevents mass production.To tackle this problem, new materials are investigated to find a module that can be made widely available. Oxides are one possibility, where an added benefit is that they are chemically stable even at elevated temperature. The perovskite CaMnO3 is one of the more promising oxides, with elements that are abundant on earth and cheap. The material does suffer from low electrical conductivity which results in a low electrical conductivity and efficiency. A substantial effort has been put in to increase the efficiency of CaMnO3, hut it still needs improvement.In my thesis, I have investigated the CaMnO3 system. CaMnO3 was synthesized using co-reactive RF-magnetron sputtering and post annealing. The synthesis method is already known hut has not been used for deposition of perovskites. I have also demonstrated that this synthesis method can be used to dope CaMnO3 with niobium at appropriate levels for enhancing the efficiency.
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19.
  • Eriksson, Emma, 1980, et al. (författare)
  • A microfluidic device for reversible environmental changes around single cells using optical tweezers for cell selection and positioning
  • 2010
  • Ingår i: Lab Chip. - : Royal Society of Chemistry (RSC). - 1473-0197 .- 1473-0189. ; 10:5, s. 617-625
  • Tidskriftsartikel (refereegranskat)abstract
    • Cells naturally exist in a dynamic chemical environment, and therefore it is necessary to study cell behaviour under dynamic stimulation conditions in order to understand the signalling transduction pathways regulating the cellular response. However, until recently, experiments looking at the cellular response to chemical stimuli have mainly been performed by adding a stress substance to a population of cells and thus only varying the magnitude of the stress. In this paper we demonstrate an experimental method enabling acquisition of data on the behaviour of single cells upon reversible environmental perturbations, where microfluidics is combined with optical tweezers and fluorescence microscopy. The cells are individually selected and positioned in the measurement region on the bottom surface of the microfluidic device using optical tweezers. The optical tweezers thus enable precise control of the cell density as well as the total number of cells within the measurement region. Consequently, the number of cells in each experiment can be optimized while clusters of cells, that render subsequent image analysis more difficult, can be avoided. The microfluidic device is modelled and demonstrated to enable reliable changes between two different media in less than 2 s. The experimental method is tested by following the cycling of GFP-tagged proteins (Mig1 and Msn2, respectively) between the cytosol and the nucleus in Saccharomyces cerevisiae upon changes in glucose availability.
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20.
  • Eriksson, Fredrik, 1975- (författare)
  • Multilayer X-ray mirrors for water window wavelengths
  • 2001
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • This thesis describes the design, growth and x-ray characterization of normal incidence multilayer x-ray mirrors. The mirrors are intended as condenser optics for soft x-ray microcsopy in the water window.A droplet-target laser-plasma soft x-ray source has been developed to be used in a compact soft x-ray microscope. The microscope operates at the wavelength λ=3.374 nm, corresponding to the C VI emission line from a laser plasma x-ray source. Due to the isotropic nature of laser-produced plasma sources, large shaped, normal incidence condenser mirrors collecting x-rays over a large solid angle from the source, and focusing them onto the specimen, are required.Since ordinary refractive optics cannot be utilized in this wavelength range, so called multilayer interference structures, based on diffraction and reflection, have been developed.The multilayers were designed to have the maximal theoretical normal reflection of the first and second order of λ=3.374 nm using the IMD computer software. The realization of the multilayers were accomplished using ion-assisted dual target DC magnetron sputtering. To characterize the multilayers and improve the deposition process hard x-ray reflectivity was used. Further, at-wavelength (λ=3.374 nm) reflectivity measurements were carried out using a reflectometer based on the laser-plasma source. In addition, measurements have been performed using synchrotron radiation at the Advanced Light Source (ALS) in Berkeley.
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21.
  • Eriksson, Fredrik, 1975- (författare)
  • Soft X-ray Multilayer Mirrors
  • 2004
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • This thesis is focused on the design, growth and characterization of soft x-ray multilayer mirrors with the emphasis on the wavelength region called the water window (λ=2.4-4.4 nm). The main application in mind is condenser mirrors for a high resolution compact soft x-ray microscope using a droplet-target laser-produced plasma (LPP) source operating at λ=3.374 nm. However, other applications, utilizing other wavelengths, have also been considered.The design of the multilayers which involves understanding of the details of the optical properties of the elements and the interaction between multilayer and electromagnetic radiation is reviewed. To design the multilayers, e.g., to determine the material system, the individual layer thicknesses, and the total number of layers, the simulation software package IMD was used. From the simulations it was also found that in order to realize high-reflectivity multilayer mirrors, interface imperfections, like roughness and intermixing need to be minimized.In particular the material systems W/B4C, Cr/Sc, and Ni/V grown by ion-assisted dualtarget magnetron sputter deposition, have been studied. The effect of various process parameters, especially the energy and flux of low-energy ion bombardment have been investigated in order to increase the understanding of the ion-surface interactions and the materials science of the multilayers.To characterize the multilayers mainly different x-rays techniques have been used; hard x-ray reflectivity, LPP soft x-ray reflectivity and also soft x-ray synchrotron reflectivity measurements at BESSY in Berlin and at the Advanced Light Source (ALS) in Berkeley. Both specular reflectivity and diffuse scattered intensity has been measured to assess the lateral and vertical structure of the multilayers.With an increased knowledge and understanding of the effects of the ion-surface interaction on the structure of the multilayers, advances were made in the development, with a following improvement in performance. The first multilayer material system investigated was W /B,C. However, because of a naturally high absorption of x-rays in W, the theoretically achievable reflectivity is very low, only about 12%.Cr/Sc, on the other hand, has potentially a much higher reflectivity of about 60%. Here different energies, but also fluxes, of ion assistance was investigated. It was found that, for a low ion flux, the ion energy, providing the optimum compromise between reduced roughness and induced intermixing, was rather high. By increasing the ion flux,the energy could be lowered, which in turn decreased the intermixing with a subsistent surface smoothening. This resulted in an improved reflectivity, where maximum nearnormal incidence reflectivities of R=5.5% and R=14.5% were achieved at λ=3.374 nm and at the Sc absorption edge (λ=3.115 nm), respectively.However, although fairly high reflectivities were obtained, the trade-off between roughness reduction and interface mixing persisted. Analytical calculations, based on a binary collision approximation, revealed that an interface mixing of ±1 atomic distance is unavoidable when a continuous flux of assisting ions is used. To overcome this limitation, a sophisticated interface engineering technique was employed, where the first part of each layer was grown using a high-flux of low energy ions, and the remaining part with a slightly higher ion energy. This method was demonstrated to largely eliminate the intermixing while maintaining the smoothening effect of ion-assistance.Using this novel modulated low-energy and high-flux ion-assistance technique extremely flat and abrupt interfaces were obtained. Soft x-ray Cr/Sc and Ni/V multilayer mirrors with near-normal incidence reflectivities of 20.7% and 2.7% at the Sc and V(λ=2.43 nm) absorption edges, respectively, were realized. Multilayer optimized for the Brewster angle showed a reflectance of R=26.7% and a polarizing power of Rs/Rp=5450 for Cr/Sc and R=l0% and Rs/Rp=4190 for Ni/V, when realized with engineered interfaces.Finally, also the long-term goal of producing a large-area, spherically-shaped, normalincidence soft x-ray multilayer condenser mirror for a compact soft x-ray microscope was accomplished.
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22.
  • Eriksson, Maja, 1975, et al. (författare)
  • Comparing mono- and divalent DNA groove binding cyanine dyes--Binding geometries, dissociation rates, and fluorescence properties
  • 2006
  • Ingår i: Biophysical Chemistry. - : Elsevier BV. - 1873-4200 .- 0301-4622. ; 122:3, s. 195-205
  • Tidskriftsartikel (refereegranskat)abstract
    • The unsymmetrical cyanine dyes BOXTO-PRO and BOXTO-MEE were derived from the DNA groove binder BOXTO, by adding a positively charged or a non-ionic hydrophilic tail to BOXTO, respectively. The main objective was to obtain more efficient DNA probes, for instance in electrophoresis and microscopy, by slowing down the dissociation of BOXTO from DNA. The interactions with mixed sequence DNA was studied with fluorescence and absorbance spectroscopy, stopped-flow dissociation and gel electrophoresis. Both the derivatives are groove bound as BOXTO, and have similar fluorescence properties when bound to mixed sequence DNA in free solution. BOXTO-PRO exhibits a slower dissociation than BOXTO from DNA, whereas the dissociation rate for BOXTO-MEE is faster and, unexpectedly independent of the ionic strength. During gel electrophoresis both BOXTO-PRO and BOXTO-MEE exhibit a faster dissociation rate than BOXTO. Still, BOXTO-PRO seems to be a good alternative as DNA probe, especially for applications in free solution where the dissociation is slower than for the corresponding intercalator TOPRO-1.
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23.
  • Gharavi, Mohammad Amin, 1985-, et al. (författare)
  • High thermoelectric power factor of pure and vanadium-alloyed chromium nitride thin films
  • 2021
  • Ingår i: Materials Today Communications. - : ELSEVIER. - 2352-4928. ; 28
  • Tidskriftsartikel (refereegranskat)abstract
    • Chromium-nitride based materials have shown unexpected promise as thermo-electric materials for, e.g., wasteheat harvesting. Here, CrN and (Cr,V)N thin films were deposited by reactive magnetron sputtering. Thermoelectric measurements of pure CrN thin films show a low electrical resistivity between 1.2 and 1.5 x 10(-3) Omega cm and very high values of the Seebeck coefficient and thermoelectric power factor, in the range between 370-430 mu V/K and 9-11 x 10(-3) W/mK(2), respectively. Alloying of CrN films with small amounts (less than 15 %) of vanadium results in cubic (Cr,V)N thin films. Vanadium decreases the electrical resistivity and yields powerfactor values in the same range as pure CrN. Density functional theory calculations of sub-stoichiometric CrN1-delta and (Cr,V)N1-delta show that nitrogen vacancies and vanadium substitution both cause n-type conductivity and features in the band structure typically correlated with a high Seebeck coefficient. The results suggest that slight variations in nitrogen and vanadium content affect the power factor and offers a means of tailoring the power factor and thermoelectric figure of merit.
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24.
  • Gustavsson, Ulf, 1975, et al. (författare)
  • On the Impact of Hardware Impairments on Massive MIMO
  • 2014
  • Ingår i: IEEE Globecom 2014 Workshop - Massive MIMO: From Theory to Practice, 2014-12-08, Austin, Texas, USA. - 9781479974702 ; , s. 294-300
  • Konferensbidrag (refereegranskat)abstract
    • Massive multi-user (MU) multiple-input multiple-output (MIMO) systems are one possible key technology for next generation wireless communication systems. Claims have been made that massive MU-MIMO will increase both the radiated energy efficiency as well as the sum-rate capacity by orders of magnitude, because of the high transmit directivity. However, due to the very large number of transceivers needed at each base-station (BS), a successful implementation of massive MU-MIMO will be contingent on of the availability of very cheap, compact and power-efficient radio and digital-processing hardware. This may in turn impair the quality of the modulated radio frequency (RF) signal due to an increased amount of power-amplifier distortion, phase-noise, and quantization noise. In this paper, we examine the effects of hardware impairments on a massive MU-MIMO single-cell system by means of theory and simulation. The simulations are performed using simplified, well-established statistical hardware impairment models as well as more sophisticated and realistic models based upon measurements and electromagnetic antenna array simulations.
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25.
  • Jemberie, Wossenseged Birhane, 1985-, et al. (författare)
  • "Ageing with an alcohol problem is not what I envision" : reclaiming agency in shaping personal ageing trajectory and recovery from alcohol problems
  • 2023
  • Ingår i: BMC Geriatrics. - : BioMed Central (BMC). - 1471-2318. ; 23
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Eliciting and understanding older persons’ descriptions of their resources for healthy ageing and the interaction of these resources with alcohol use and alcohol problems can facilitate health promotion. It can also inform clinicians when identifying areas of recovery capital that present risks and strength for older people seeking alcohol treatment. The objective of this study was to illuminate the experiences and perspectives of older persons on ageing, alcohol use, treatment, and recovery from alcohol problems, as well as their understanding of healthy ageing.Methods: Eight men and two women, aged 61 to 73 years, with moderate drinking as a treatment goal and treated at an outpatient alcohol clinic in Sweden, participated in semi-structured audio-recorded virtual interviews. A qualitative content analysis examined the transcribed interviews.Results: Three themes were identified: “Tipping the balance”, “Staying behind a veil” and “Lifting the vail”. First, participants understood healthy ageing as a personal and multidimensional process that involved actively expanding, maintaining or adjusting to the resources needed to lead an active and meaningful life while preserving autonomy, dignity and independence for as long as possible. Second, most participants viewed moderate alcohol use as a contributor to healthy ageing. They sought treatment when their drinking became unsustainable and an immediate threat to their healthy ageing resources. Stigma, ambivalence and a lack of treatment options, however, contributed to delayed treatment. Third, the participants responded to treatment approaches that elicited their concern, incorporated their expertise and treatment and life goals, appreciated their autonomy and agency, and considered them partners in goal setting and decision making. Reduced drinking helped participants regain their agency and improved their healthy ageing capital which in turn catalyzed continuing recovery.Conclusions: Older persons in non-abstinent recovery perceive healthy ageing and alcohol recovery as personal and interacting multidimensional processes involving their agency to improve biopsychosocial functioning. Treatment approaches that recognize older persons’ desire for healthy ageing, incorporate their treatment goals and respect their autonomy are likely to be acceptable and effective.
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26.
  • Jemberie, Wossenseged Birhane, 1985- (författare)
  • Alcohol and aging : a multimethod study on heterogeneity and multidimensionality
  • 2023
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Background and Objectives: With an ageing population, the number of older persons with substance use problems, particularly problematic alcohol use, is increasing. Despite grow­ing recognition of the negative consequences of problematic alcohol use on older persons, there is a dearth of knowledge about the alcohol use profiles and the dimensionality of alcohol problems in older people. Moreover, little is known about older persons’ experi­ences and perspectives on alcohol use in relation to their ageing and their personal goals regarding treatment and recovery. This thesis aimed to (i) describe the characteristics of older persons who accessed municipal substance use treatment and care services (addic­tion services) and to investigate their future hospitalization; (ii) examine the heterogeneity and multidimensionality of problematic alcohol use among older persons; and (iii) to shed light on the experiences and perspectives of older persons regarding ageing, alcohol prob­lems and recovery.Methods: For studies I-III, municipal Addiction Severity Index (ASI) assessment data (between 2003 and 2017) from adults aged 50 years and older were used to select the study samples. Generalized linear regression models investigated hospitalization related out­comes among 3624 older persons in Study-I. In Study-II, a latent class analysis was applied on ASI data from 1747 individuals with alcohol problems. Study-III linked the ASI data from Study-II to hospital discharge and mortality data forming time-to-repeated-event dataset; Andersen-Gill regression model with a robust variance estimator was used for the analysis. Study-IV applied qualitative content analysis on interview data from ten older persons re­cruited from a specialist outpatient clinic for alcohol treatment. Results: Nearly three-fourth of older persons assessed for substance use severity at municipal addiction services were later hospitalized (Study-I). Individuals diagnosed with substance use disorders, psychiatric or dual diagnoses had more cumulative hospitalized days, higher rates of hospital readmissions, and shorter time to first admission following an initial ASI assessment at municipal addiction services (Study-I). Five distinct groups of older persons with comparable alcohol problem severity but with variation in onset age, psychiatric comorbidities, polysubstance use, social support and gender composition were identified (Study-II). The five groups varied in risks of repeated hospitalizations due to substance use and psychiatric disorders (Study-III). Older persons experienced their ageing and alcohol use having a dynamic interplay (Study-IV). They needed to constantly negotiate with their environment to maintain a positive ageing trajectory. They perceived moderate alcohol use fosters healthy ageing, but over time, experienced their alcohol use as unsustainable and a threat to their pursuit of healthy ageing. Stigma and ambivalence delayed treatment seeking (Study-IV). They accessed treatment programs which re­spected their preferences and autonomy, engaged them in goal setting and strengthened their agency. After reducing their alcohol use, positive changes in their biopsychosocial functioning encouraged them to continue their recovery journey even in the presence of setbacks (Study-IV).Conclusion: Most older persons who access municipal addiction services are hospitalized repeatedly. Many older persons with alcohol problems live with medical and psychiatric comorbidities suggesting multiple care needs from health and social care services. Incor­porating older persons’ desire for healthy ageing into alcohol treatment plan can facilitate treatment engagement and recovery. Many older persons aim to moderate their alcohol consumption. Clinicians can deliver person-centered care for older persons, by consider­ing their heterogeneity in treatment goals, biopsychosocial functioning, and available re­sources. A multidimensional identification of alcohol use profiles could improve treatment by establishing the variation in alcohol problems among older treatment seekers. Older persons stay engaged in alcohol treatment programs which value their experiences and expertise, incorporate their personal treatment and life goals, respect their autonomy and agency, and involve them as active participants. Sensitizing service providers on old age substance use problems could provide multiple points of contact for screening of older persons and earlier referral to treatment. A streamlined data sharing within and between health and social care services fosters timely and equitable care and facilitates an inte­grated and person-centered care across the continuum. 
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27.
  • Jemberie, Wossenseged Birhane, 1985-, et al. (författare)
  • Studying the trajectories and mediators of old-age problematic alcohol use and the agency of older persons
  • 2023
  • Annan publikationabstract
    • Unit of analysis: IndividualPopulation: Older people aged between 61 and 73 years who have sought treatment for alcohol at a specialist outpatient clinic in a metropolitan city in Sweden.Time Method: Cross-sectionSampling procedure: Non-probability: PurposiveThe study participants were purposefully recruited from a specialist outpatient alcohol treatment clinic located in a Swedish metropolitan city. To be eligible for the study, participants had to be 55 years or older, had to self-report a history of problematic alcohol use and treatment for alcohol use after the age of 50. Individuals who were unable or unwilling to provide informed consent or participate in the interview via Zoom, Skype, or telephone were excluded from the study.Time period(s) investigated: 2021-12 – 2022-04Number of individuals/objects: 10Data format / data structure: Text
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28.
  • Jemberie, Wossenseged Birhane, 1985-, et al. (författare)
  • Substance Use Disorders and COVID-19 : Multi-Faceted Problems Which Require Multi-Pronged Solutions
  • 2020
  • Ingår i: Frontiers in Psychiatry. - : Frontiers Media S.A.. - 1664-0640. ; 11
  • Tidskriftsartikel (refereegranskat)abstract
    • COVID-19 shocked health and economic systems leaving millions of people without employment and safety nets. The pandemic disproportionately affects people with substance use disorders (SUDs) due to the collision between SUDs and COVID-19. Comorbidities and risk environments for SUDs are likely risk factors for COVID-19. The pandemic, in turn, diminishes resources that people with SUD need for their recovery and well-being. This article presents an interdisciplinary and international perspective on how COVID-19 and the related systemic shock impact on individuals with SUDs directly and indirectly. We highlight a need to understand SUDs as biopsychosocial disorders and use evidence-based policies to destigmatize SUDs. We recommend a suite of multi-sectorial actions and strategies to strengthen, modernize and complement addiction care systems which will become resilient and responsive to future systemic shocks similar to the COVID-19 pandemic.
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29.
  • Khajavizadeh, Lida, 1978- (författare)
  • Materials Design for the Improvement of SiC Field Effect Gas Sensor performance in High Temperature Process Control applications
  • 2023
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Following growing concerns about the effect these last decades of accelerating energy consumption, escalating use of natural (not the least fossil) resources, and waste generation has had on earth’s climate, human health, and the environment, industry is facing mounting pressure to increase the energy-, resource-, and cost-efficiency of both processes and products while drastically reducing pollutant emissions. In response, industry is, besides increasing their utilization of renewable energy and introducing new bio-based products, taking advantage of the rapid development in 5G technology and associated wireless interconnectivity to move towards full automation of production processes and facilities. With the ability to connect and collect information from a large number of instruments and process steps as well as to analyse huge amounts of multi-dimensional data, entire production lines can be automatically controlled and/or adapted, e.g., through the application of machine learning, for optimized efficiency and minimized greenhouse gas and pollutant emissions. In order to fully benefit from this so-called 4th industrial revolution and the Industrial Internet of Things (IIoT), however, access to cost-efficient and long-term reliable means for measuring various process parameters in multiple locations is required.The basis for this thesis is therefore the characterization of silicon carbide-based Metal Oxide Semiconductor Field Effect Transistor (MOSFET) gas sensors for their applicability in real-time monitoring of process gases/ gas mixtures and pollutant emissions in high-temperature applications, e.g., control of flue gas/ exhaust after-treatment systems, as well as investigations performed to gain a better understanding of the corresponding sensing mechanisms and to improve sensor performance in terms of e.g., long-term reliability.Besides demonstrating the general applicability of SiC MOSFET gas sensors in ammonia (NH3) slip detection and control of Selective Catalytic Reduction and similar flue gas/ exhaust emissions abatement systems to minimize the release of nitrogen oxides into the atmosphere from the energy production and transport sectors, sensors for the selective monitoring of nitrogen oxides with negligible interference from (sensitivity/ cross-sensitivity to) ammonia have been developed. Through variation of the gold/ iridium composition of the MOSFET gate contact, the interaction of which with gaseous substances in the ambient determines the sensor signal, sensors selective to ammonia and nitrogen oxides (NOx; NO and NO2), respectively, could be developed. Furthermore, as both sensor-types exhibit decent sensitivity to the respective substance over a common temperature interval, the realization of simultaneous NH3 and NOx monitoring with one and the same sensor probe would be facilitated. In relating the sensor response under different conditions to the composition and micro- (/nano-) structure of the gate contact material another piece in the puzzle towards an understanding of the ammonia sensing mechanism of field effect sensor devices could also be obtained.Through the investigation of co-deposited platinum group metals/ metal oxides in different ratios it was also shown possible to improve the long-term stability of carbon monoxide (CO) sensors intended for emissions monitoring and combustion control in industrial processes. Both the materials composition and structure were thereby evaluated and their effect on other important sensor parameters, e.g., sensitivity and temperature dependence, analysed. To further improve sensitivity and selectivity of CO as well as NH3 sensors for combustion control and ammonia slip monitoring applications, respectively, the sensor characteristics were also studied under different ambient conditions, e.g., variations in oxygen concentration, and related to the microstructure of the deposited gate materials. From the simultaneous tuning of film structure and operating temperatures, the selectivity could be enhanced for both the CO and NH3 sensors.In summary, the obtained research results from this thesis work have contributed to a further understanding of the sensing mechanisms of silicon carbide-based MOSFET sensors for CO, NOx, and NH3 monitoring and through the tuning of materials properties and sensor operation parameters generated improvements in sensor reliability, sensitivity, and selectivity of importance to the further realization of sensors for process control and emissions reduction applications.
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30.
  • Lagou, Vasiliki, et al. (författare)
  • Sex-dimorphic genetic effects and novel loci for fasting glucose and insulin variability
  • 2021
  • Ingår i: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 12:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Differences between sexes contribute to variation in the levels of fasting glucose and insulin. Epidemiological studies established a higher prevalence of impaired fasting glucose in men and impaired glucose tolerance in women, however, the genetic component underlying this phenomenon is not established. We assess sex-dimorphic (73,089/50,404 women and 67,506/47,806 men) and sex-combined (151,188/105,056 individuals) fasting glucose/fasting insulin genetic effects via genome-wide association study meta-analyses in individuals of European descent without diabetes. Here we report sex dimorphism in allelic effects on fasting insulin at IRS1 and ZNF12 loci, the latter showing higher RNA expression in whole blood in women compared to men. We also observe sex-homogeneous effects on fasting glucose at seven novel loci. Fasting insulin in women shows stronger genetic correlations than in men with waist-to-hip ratio and anorexia nervosa. Furthermore, waist-to-hip ratio is causally related to insulin resistance in women, but not in men. These results position dissection of metabolic and glycemic health sex dimorphism as a steppingstone for understanding differences in genetic effects between women and men in related phenotypes.
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31.
  • Lidehäll, Anna Karin, 1975-, et al. (författare)
  • T cell control of primary and latent cytomegalovirus infections in healthy subjects
  • 2005
  • Ingår i: Journal of Clinical Immunology. - : Springer Science and Business Media LLC. - 0271-9142 .- 1573-2592. ; 25:5, s. 473-481
  • Tidskriftsartikel (refereegranskat)abstract
    • The T cell repertoire required to control acute and latent CMV infection in otherwise healthy individuals was examined using both functional analysis and a wide range of MHC I tetramers. Both frequency and function of CMV specific T cells varied considerably between subjects, however, within subjects values remained stable over time. In total 16 ± 3.5 CMV specific T cells/μl blood was detected, with obvious immunodominance between different CMV epitopes. Most subjects with latent infection showed low CMV specific T cell activity, whereas a subgroup (1/3) of individuals was high in either frequency or function of their CMV specific T cells. Patients with acute infection displayed high initial, but rapidly decreasing, numbers of CMV specific cells. In conclusion, a majority of healthy individuals readily seem to control latent CMV infection, whereas a subpopulation (1/3) of individuals uses a large proportion of their CD8+ T cell repertoire to control the infection.
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32.
  • Magnuson, Martin, 1965-, et al. (författare)
  • Bonding Structures of ZrHx Thin Films by X-ray Spectroscopy
  • 2017
  • Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 121, s. 25750-25758
  • Tidskriftsartikel (refereegranskat)abstract
    • The variation in local atomic structure and chemical bonding of ZrHx (x=0.15, 0.30, 1.16) magnetron sputtered thin films are investigated by Zr K-edge (1s) X-ray absorption near-edge structure and extended X-ray absorption fine structure spectroscopies. A chemical shift of the Zr K-edge towards higher energy with increasing hydrogen content is observed due to charge-transfer and an ionic or polar covalent bonding component between the Zr 4d and the H 1s states with increasing valency for Zr. We find an increase in the Zr-Zr bond distance with increasing hydrogen content from 3.160 Å in the hexagonal closest-packed metal (a-phase) to 3.395 Å in the understoichiometric d-ZrHx film (CaF2-type structure) with x=1.16 that largely resembles that of bulk d-ZrH2. For yet lower hydrogen contents, the structures are mixed a- and d-phases, while sufficient hydrogen loading (x>1) yields a pure δ-phase that is understoichiometric, but thermodynamically stable. The change in the hydrogen content and strain is discussed in relation to the corresponding change of bond lengths, hybridizations, and trends in electrical resistivity.
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33.
  • Magnuson, Martin, 1965-, et al. (författare)
  • Compositional dependence of epitaxial Tin+1SiCn MAX-phase thin films grown from a Ti3SiC2 compound target
  • 2019
  • Ingår i: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Institute of Physics (AIP). - 0734-2101 .- 1520-8559. ; 37:2
  • Tidskriftsartikel (refereegranskat)abstract
    • The authors investigate sputtering of a Ti3SiC2 compound target at temperatures ranging from RT (no applied external heating) to 970 °C as well as the influence of the sputtering power at 850 °C for the deposition of Ti3SiC2 films on Al2O3(0001) substrates. Elemental composition obtained from time-of-flight energy elastic recoil detection analysis shows an excess of carbon in all films, which is explained by differences in the angular distribution between C, Si, and Ti, where C scatters the least during sputtering. The oxygen content is 2.6 at. % in the film deposited at RT and decreases with increasing deposition temperature, showing that higher temperatures favor high purity films. Chemical bonding analysis by x-ray photoelectron spectroscopy shows C–Ti and Si–C bonding in the Ti3SiC2 films and Si–Si bonding in the Ti3SiC2 compound target. X-ray diffraction reveals that the phases Ti3SiC2, Ti4SiC3, and Ti7Si2C5 can be deposited from a Ti3SiC2 compound target at substrate temperatures above 850 °C and with the growth of TiC and the Nowotny phase Ti5Si3Cx at lower temperatures. High-resolution scanning transmission electron microscopy shows epitaxial growth of Ti3SiC2, Ti4SiC3, and Ti7Si2C5 on TiC at 970 °C. Four-point probe resistivity measurements give values in the range ∼120 to ∼450 μΩ cm and with the lowest values obtained for films containing Ti3SiC2, Ti4SiC3, and Ti7Si2C5.
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34.
  • Magnuson, Martin, 1965-, et al. (författare)
  • Electronic Structure of ß-Ta Films from X-ray Photoelectron Spectroscopy and First-principles Calculations
  • 2019
  • Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 470, s. 607-612
  • Tidskriftsartikel (refereegranskat)abstract
    • The electronic structure and chemical bonding of ß-Ta synthesized as a thin 001-oriented film (space group P 21m) is investigated by 4f core level and valence band X-ray photoelectron spectroscopy and compared to α-Ta bulk. For the b-phase, the 4f7/2 peak is located at 21.91 eV and with the 4f5/2 at 23.81 eV which is 0.16 eV higher compared to the corresponding 4f peaks of the a-Ta reference. We suggest that this chemical shift originates from higher resistivity and tensile strain in the ß-Ta film. Furthermore, the 5d-5s states at the bottom of the valence band are shifted by 0.75 eV towards higher binding energy in ß-Ta compared to α-Ta. This is a consequence of the lower number of nearest neighbors with four in ß-Ta compared to eight in the α-Ta phase. The difference in the electronic structures, spectral line shapes of the valence band and the energy positions of the Ta 4f, 5p core-levels of b-Ta versus a-Ta are discussed in relation to calculated states of ß-Ta and α-Ta. In particular, the lower number of states at the Fermi level of ß-Ta (0.557 states/eV/atom) versus α-Ta (1.032 states/eV/atom) that according to Mott’s law should decrease the conductivity in metals and affect the stability by charge redistribution in the valence band. This is experimentally supported from resistivity measurements of the film yielding a value of ~170 µW cm in comparison to α-Ta bulk with a reported value of ~13.1 µW cm.
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35.
  • Magnuson, Martin, 1965-, et al. (författare)
  • Reactive magnetron sputtering of tungsten target in krypton/trimethylboron atmosphere
  • 2019
  • Ingår i: Thin Solid Films. - : Elsevier. - 0040-6090 .- 1879-2731. ; 688
  • Tidskriftsartikel (refereegranskat)abstract
    • W-B-C films were deposited on Si(100) substrates held at elevated temperature by reactive sputtering from a W target in Kr/trimethylboron (TMB) plasmas. Quantitative analysis by Xray photoelectron spectroscopy (XPS) shows that the films are W-rich between ~ 73 and ~ 93 at.% W. The highest metal content is detected in the film deposited with 1 sccm TMB. The C and B concentrations increase with increasing TMB flow to a maximum of ~18 and ~7 at.%, respectively, while the O content remains nearly constant at 2-3 at.%. Chemical bonding structure analysis performed after samples sputter-cleaning reveals C-W and B-W bonding and no detectable W-O bonds. During film growth with 5 sccm TMB and 500 o C or with 10 sccm TMB and 300-600 o C thin film X-ray diffraction shows the formation of cubic 100-oriented WC1-x with a possible solid solution of B. Lower flows and lower growth temperatures favor growth of W and W2C, respectively. Depositions at 700 and 800 o C result in the formation of WSi2 due to a reaction with the substrate. At 900 o C, XPS analysis shows ~96 at.% Si in the film due to Si interdiffusion. Scanning electron microscopy images reveal a fine-grained microstructure for the deposited WC1-x films. Nanoindentation gives hardness values in the range from ~23 to ~31 GPa and reduced elastic moduli between ~220 and 280 GPa in the films deposited at temperatures lower than 600 o C. At higher growth temperatures the hardness decreases by a factor of 3 to 4 following the formation of WSi2 at 700-800 o C and Si-rich surface at 900 o C.
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36.
  • Orru, Anna Maria, 1976, et al. (författare)
  • AHA! festival 2016
  • 2016
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • For the third year, the AHA festival investigates the meeting between art and science in a three-day event at the Chalmers University of Technology hosted by the Department of Architecture and the Department of Physics. An international festival intended to provide enlightening experiences, staging surprises, new thoughts and displaced perspectives that lead to alternative modes of thinking about exploring the world through art and science. We invite scientists (physicists, historians, astronomers, engineers), artists (dancers, musicians, painters, poets, acrobats) who reside in these borderlands and wish to share their vision and work. The key intention is to celebrate both art and science as key knowledge building devices.The first year’s theme ’Embodiment’ (2014) explored the body as our anchor in the world, followed by the 2015 theme on ’Numbers’, a delightful net we cast over the world. This year's theme is ’Uni-verse,’ again a natural consequence of our interest in the relation between art and science. The elemental force that drives science as well as art is curiosity. Come be curious with us! During the festival we have chosen to divide the word universe into three: uni and "-" and verse. Uni means that something is combined into a whole. Verse means that we are turned in a direction, the origin of the word tells us that it is the plow that turns at the end of the field. And the dash "-" is all the spaces and cracks where new discoveries can grow. Art and science unfolds in the gap between what we know and what we want to know.
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37.
  • Persson, Anders I., 1973, et al. (författare)
  • Expression of delta opioid receptor mRNA and protein in the rat cerebral cortex and cerebellum is decreased by growth hormone.
  • 2003
  • Ingår i: Journal of neuroscience research. - : Wiley. - 0360-4012 .- 1097-4547. ; 71:4, s. 496-503
  • Tidskriftsartikel (refereegranskat)abstract
    • Hormones released from the pituitary have been shown to regulate the expression of different proteins in the central nervous system. We wanted to examine whether peripheral administration of bovine growth hormone (bGH) regulates the expression of delta-opioid receptor (DOR) in the cerebral cortex and cerebellum. Expression of the DOR protein was quantified using Western blot densitometry. DOR mRNA was quantified with a solution hybridization RNase protection assay. Hypophysectomized (Hx) and untreated normal female rats were included in the study. All Hx rats were hormonally treated with cortisol (400 microg/kg/day) and L-thyroxine (10 microg/kg/day) for 19 days. Hypophysectomy resulted in a threefold increase in cerebral cortex and a twofold increase in cerebellum of the DOR protein compared with normal rats. One subgroup of Hx rats received bGH (1 mg/kg body weight) as a daily subcutaneous injection for 19 days. This treatment normalized the levels of DOR protein in the cerebral cortex and cerebellum. Immunohistochemical experiments showed that GH decreased DOR expression especially in layers II-VI in cerebral cortex and in stratum moleculare in cerebellum. Quantification of DOR mRNA by solution hybridization RNase protection assay corresponded to the DOR protein measurements. We conclude that the expression of DORs in cerebral cortex and cerebellum is regulated by GH.
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38.
  • Ramasamy, Sudha, 1974-, et al. (författare)
  • Sampling-Based Path Planning Algorithm for a Plug & Produce Environment
  • 2023
  • Ingår i: Applied Sciences. - : MDPI. - 2076-3417. ; 13:22, s. 12114-12114
  • Tidskriftsartikel (refereegranskat)abstract
    • The purpose of this article is to investigate a suitable path planning algorithm for a multi-agent-based Plug & Produce system that can run online during manufacturing. This is needed since in such systems, resources can move around frequently, making it hard to manually create robot paths. To find a suitable algorithm and verify that it can be used online in a Plug & Produce system, a comparative study between various existing sampling-based path planning algorithms was conducted. Much research exists on path planning carried out offline; however, not so much is performed in online path planning. The specific requirements for Plug & Produce are to generate a path fast enough to eliminate manufacturing delays, to make the path energy efficient, and that it run fast enough to complete the task. The paths are generated in a simulation environment and the generated paths are tested for robot configuration errors and errors due to the target being out of reach. The error-free generated paths are then tested on an industrial test bed environment, and the energy consumed by each path was measured and validated with an energy meter. The results show that all the implemented optimal sampling-based algorithms can be used for some scenarios, but that adaptive RRT and adaptive RRT* are more suitable for online applications in multi-agent systems (MAS) due to a faster generation of paths, even though the environment has more constraints. For each generated path the computational time of the algorithm, move-along time and energy consumed are measured, evaluated, compared, and presented in the article.
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39.
  • Rosqvist, Fredrik, 1985-, et al. (författare)
  • Overeating saturated fat promotes fatty liver and ceramides compared to polyunsaturated fat : a randomized trial
  • 2019
  • Ingår i: Journal of Clinical Endocrinology and Metabolism. - : Oxford University Press. - 0021-972X .- 1945-7197. ; 104:12, s. 6207-6219
  • Tidskriftsartikel (refereegranskat)abstract
    • CONTEXT: Saturated fat (SFA) versus polyunsaturated fat (PUFA) may promote non-alcoholic fatty liver disease (NAFLD) by yet unclear mechanisms.OBJECTIVE: To investigate if overeating SFA- and PUFA-enriched diets lead to differential liver fat accumulation in overweight and obese humans.DESIGN: Double-blind randomized trial (LIPOGAIN-2). Overfeeding SFA vs PUFA for 8 weeks, followed by 4 weeks of caloric restriction.SETTING: General community.Participants: n=61 overweight or obese men and women.INTERVENTION: Muffins high in either palm (SFA)- or sunflower oil (PUFA) were added to the habitual diet.MAIN OUTCOME MEASURE: Lean tissue mass (not reported here). Secondary and exploratory outcomes included liver and ectopic fat depots.RESULTS: By design, body weight gain was similar in SFA (2.31±1.38 kg) and PUFA (2.01±1.90 kg) groups, P=0.50. SFA markedly induced liver fat content (50% relative increase) along with liver enzymes and atherogenic serum lipids. In contrast, despite similar weight gain, PUFA did not increase liver fat or liver enzymes or cause any adverse effects on blood lipids. SFA had no differential effect on the accumulation of visceral fat, pancreas fat or total body fat compared with PUFA. SFA consistently increased, while PUFA reduced circulating ceramides; changes that were moderately associated with liver fat changes and proposed markers of hepatic lipogenesis. The adverse metabolic effects of SFA were reversed by calorie restriction.CONCLUSIONS: Saturated fat markedly induces liver fat and serum ceramides whereas dietary polyunsaturated fat prevent liver fat accumulation, reduce ceramides and hyperlipidemia during excess energy intake and weight gain in overweight individuals.
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40.
  • Stenberg, Fredrik, 1975- (författare)
  • Semi-Markov Models for Insurance and Option Rewards
  • 2007
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • This thesis presents studies of semi-Markov models for insurance and option rewards. The thesis consists of the introduction and six papers. The introduction presents the results of the thesis in an informal way.In paper A, a general semi-Markov reward model is presented. Recurrence relations for evaluation of higher moments of the reward process are given, as well as a backward semi-Markov reward processes are applied to insurance problems for the first time.In paper B, models for disability insurance given in paper A are further extended. Statistical evidences of relevance of semi-Markov setting are given. Applications to profit-risk analysis for contracts are considered.In paper C, a more detailed explanation of the algorithmic for the non-homogenous backward semi-Markov reward process is given. Two algorithmic approaches to solve the problem in an iterative manner are given. One of the algorithms is presented in a pseudo-code.In paper D, the geometrical Brownian motion with drift and volatility controlled by a semi-Markov processes is considered as a price process in option valuation. The discrete version is examined and limit theorems describing the transition from discrete to continuous time are given. Monte-Carlo algorithms are described.In paper E, a general price process represented by a two-component Markov process is considered. American options with pay-off functions, which admit power type upper bounds are studied. Both the transition characteristics of the price processes and the pay-off functions are assumed to depend on a perturbation parameter and to converge to the corresponding limits. Results about the convergence of reward functionals for American options are presented.In paper F, convergence for option rewards when the price processes are perturbed exponential Lévy type process controlled by semi-Markov indices is studied. Both European and American type options with pay-off functions which admit power type upper bounds are considered. The paper continues research started in paper D and gives a key example for paper E.
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41.
  • Stendahl, Sjoerd, 1993- (författare)
  • Multilayer neutron optics based on isotope-enriched 11B4C
  • 2023
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The work in this thesis covers the design, growth and characterisation of neutron multilayers. The achieved reflectivity performance of a neutron multilayer depends on the achieved optical contrast between the layers as well as the achieved interface width between the layers. Because the reflectivity of a neutron multilayer depends exponentially on the square of the interface width, even a modest improvement can substantially increase the achieved reflectivity performance. It is for this reason that a large part of this work has been focused in making smoother and more abrupt multilayers, descreasing the total interface width. As multilayers are such an integral component of most neutron optical instruments, any improvement in terms of reflectivity performance has broad implications for all conducted neutron scattering experiments. The conventional material system of choice for neutron optical components is Ni/Ti, owing to the high contrast in scattering length density (SLD). The reflected intensity of such components is largely dependent on the interface width, primarily caused by the formation of nanocrystallites, interdiffusion, and/or intermixing. Apart from hampering the reflectivity performance, the finite interface width between the layers also limits the minimum usable layer thickness in the mirror stack. In this work, Ni/Ti based multilayers are grown using ion‐assisted magnetron sputtering. By co‐depositing B4C in the multilayer stack, the for‐mation of nanocrystallites as well as intermetallics between the interfaces were succesfully prevented. The co‐deposition of B4C has been combined with a modulated ion assistance scheme, where an initial buffer layer is grown at a low ion energy creating abrupt interfaces, while the remainder of the layer is grown at a higher ion energy, smoothening the interfaces. X‐ray reflectivity (XRR) measurements show significant improvements in terms of reflectivity when the multilayers are co‐deposited with B4C . This has further been investigated using low neutron‐absorbing isotope‐enriched 11B4C . The deposited 11B4C containing multilayers have been, characterized using neutron reflectometry, X-ray reflectivity, transmission electron microscopy, elastic recoil detection analysis, X‐ray photoelectron spectroscopy and grazing incidence small angle scattering (GISAXS). Structural parameters in the growth direction such as interface width and thickness variations have been determined by combined fits on X‐ray and neutron reflectivity measurements, while the interface morphology has been investigated using GISAXS. The GISAXS measurements show that the co‐deposition of 11B4C leads to mounded interfaces with more strongly vertically correlated interface profiles, this can be attributed to a decreased adatom mobility when 11B4C is incorporated. The coupled fits to specular X‐ray and neutron reflectivity measurements suggest a significant improvement in interface width for the samples that have been co‐deposited with 11B4C using a modulated on assistance scheme during deposition, where an interface width of 2.7 Å has been achieved in a 11B4C containing multilayer. The reflectivity for such 11B4C containing multilayers have been simulated for a neutron supermirror (N = 5000) using the IMD software. The predicted reflectivity performance at the critical angle of an m = 6 supermirror for the 11B4C containing samples amounts to about 76%, which is a significant increase compared to the current state‐of‐the‐art supermirrors made with pure Ni/Ti, which have a predicted reflectivity of 65%. This results in a reflectivity increase from 1.3% to 6.6% after a total of 10 reflections from this critical angle, translating to an increase of over 500% for neutrons reflected at this angle. At lower incidence angles, corresponding to thicker periods, the current state‐of‐the‐art is expected to perform better due the higher optical contrast. By combining a material system with a higher optical contrast in the thicker layers with 11B4C containing multilayers in the thinner layers, a high reflectivity performance can be obtained over all reflected incidence angles. This has been demonstrated by a proof of concept, where thicker Ni/Ti multilayers with thin (0.15 nm) 11B4C interlayers between the interfaces show the best reflectivity at a period of 84 Å, while 11B4C deposited in both multilayer stacks has shown the best reflectivity performance at thinner periods at 48 Å and 30 Å. Chemically homogeneous B4C interference mirrors with 11B/10B isotope modulation have been investigated as well to seek new possibilities for future neutron optical components. Preliminary neutron reflectometry were performed, showing very promising results with 10% absolute reflectivity for a 128 nm thick multilayer consisting of only 20 bilayer periods with a periodicity of 33.1 Å, showing how only few layers are needed for a high reflectivity. 
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