| 691. |
- Lyngsie, Gry, et al.
(författare)
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Generation of hydroxyl radicals from reactions between a dimethoxyhydroquinone and iron oxide nanoparticles
- 2018
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- The hydroxyl radical (·OH) is a powerful oxidant that is produced in a wide range of environments via the Fenton reaction (Fe2+ + H2O2 → Fe3+ + ·OH + OH-). The reactants are formed from the reduction of Fe3+ and O2, which may be promoted by organic reductants, such as hydroquinones. The aim of this study was to investigate the extent of ·OH formation in reactions between 2,6-dimethoxyhydroquinone (2,6-DMHQ) and iron oxide nanoparticles. We further compared the reactivities of ferrihydrite and goethite and investigated the effects of the O2 concentration and pH on the generation of ·OH. The main finding was that the reactions between 2,6-DMHQ and iron oxide nanoparticles generated substantial amounts of ·OH under certain conditions via parallel reductive dissolution and catalytic oxidation reactions. The presence of O2 was essential for the catalytic oxidation of 2,6-DMHQ and the generation of H2O2. Moreover, the higher reduction potential of ferrihydrite relative to that of goethite made the former species more susceptible to reductive dissolution, which favored the production of ·OH. The results highlighted the effects of surface charge and ligand competition on the 2,6-DMHQ oxidation processes and showed that the co-adsorption of anions can promote the generation of ·OH.
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| 692. |
- Läthén, Gunnar, et al.
(författare)
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Automatic Tuning of Spatially Varying Transfer Functions for Blood Vessel Visualization
- 2012
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Ingår i: IEEE Transactions on Visualization and Computer Graphics. - : IEEE. - 1077-2626 .- 1941-0506. ; 18:12, s. 2345-2354
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Tidskriftsartikel (refereegranskat)abstract
- Computed Tomography Angiography (CTA) is commonly used in clinical routine for diagnosing vascular diseases. The procedure involves the injection of a contrast agent into the blood stream to increase the contrast between the blood vessels and the surrounding tissue in the image data. CTA is often visualized with Direct Volume Rendering (DVR) where the enhanced image contrast is important for the construction of Transfer Functions (TFs). For increased efficiency, clinical routine heavily relies on preset TFs to simplify the creation of such visualizations for a physician. In practice, however, TF presets often do not yield optimal images due to variations in mixture concentration of contrast agent in the blood stream. In this paper we propose an automatic, optimization- based method that shifts TF presets to account for general deviations and local variations of the intensity of contrast enhanced blood vessels. Some of the advantages of this method are the following. It computationally automates large parts of a process that is currently performed manually. It performs the TF shift locally and can thus optimize larger portions of the image than is possible with manual interaction. The method is based on a well known vesselness descriptor in the definition of the optimization criterion. The performance of the method is illustrated by clinically relevant CT angiography datasets displaying both improved structural overviews of vessel trees and improved adaption to local variations of contrast concentration.
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| 693. |
- Löfving, Adam, et al.
(författare)
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Angiographic visualization of the coronary arteries in computed tomography with virtual contrast injection
- 2006
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Ingår i: The Internet Journal of Radiology. - : Internet Scientific Publications, Llc.. - 1528-8404. ; 4:2
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Tidskriftsartikel (refereegranskat)abstract
- Computed Tomography Angiography (CTA) is a non-invasive alternative to catheter angiography but has had limited use in the coronary arteries due to resolution and visualization problems. Maximum intensity projection (MIP) is difficult to apply in the heart with numerous overlying contrast-filled structures. The study proposes virtual contrast injection, originally introduced for MR angiography, for visualizing the coronaries in CTA. Examination after i.v. contrast injection was made in a 16-slice CT. After virtual contrast injection (concurrent grayscale connectedness) separating the vessels, rendering of the right and left coronary separately was made with MIP and volume rendering (VRT). Images similar to invasive angiography were obtained in all 7 projections used in the clinical routine. The observer also has the possibility to freely select an optimal projection. After validation in larger materials, this may become a clinically useful non-invasive alternative for examining coronary arteries.
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| 694. |
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| 695. |
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| 696. |
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| 697. |
- Lönnermark, Anders, 1968-, et al.
(författare)
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Fire Safety of Waste Storage
- 2010
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Ingår i: PROCEEDINGS. ; , s. 51-62
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The EC Directive on landfill of waste and the development of different national regulations, together with the need and interest for biofuels, have resulted in more extensive handling and storage of these products. Calorific value and bulk density are for most fractions lower than for example oil, which translates into a further increase in volumes of fuel needed for a given amount of energy. Since the material is to be used as a high-grade fuel, higher requirements are placed on the storage technology. There will also probably be strong desire to place stocks in direct connection with for example a specific industry or co-generation plant, to minimize the need for transport. Overall, this means that very large production and handling facilities with large stocks will be required. These new types of storages also mean new types of risks. There is therefore a great need for knowledge on the risks for spontaneous ignition, fire characteristics, and risk for fire spread for these fuels and storages. If a fire occurs it can lead to significant problems with emissions and in many cases the rescue services have problems with handling these fires. These fires can also lead to large economic losses. It is, therefore, important to know both how to avoid and how to facilitate extinguishment of these fires.In the paper some trends regarding storage of waste are discussed together with the risks for self-heating and emissions. Experiences from real fires are presented and some existing guidelines for storage of waste are discussed.
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| 698. |
- Lönnermark, Anders, et al.
(författare)
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Fuel Storage Safety
- 2013
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Ingår i: EERA Bioenergy News. ; :2, s. 9-10
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 699. |
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| 700. |
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