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- Funk, Eva, 1953-, et al.
(author)
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Patient-initiated breath-holds in MRI : an alternative for reducing respiratory artifacts and improving image quality
- 2015
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In: Clinical imaging. - : Elsevier. - 0899-7071 .- 1873-4499. ; 39:4, s. 619-622
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Journal article (peer-reviewed)abstract
- Purpose: To investigate MRI image quality using two different breath-hold techniques.Materials and methods: Thirty patients remitted for MRI, 2D-dual gradient echo acquisition of the liver conducted two separate breath-hold acquisitions in randomized order, operator-instructed and patient-initiated. The images were reviewed by two radiologists.Results: There were no significant differences in image quality between the two breath-hold techniques either in overall image quality or respiratory motion artifacts. This assessment was equal and concordant for both radiologists.Conclusion: In terms of image quality, the patient self-initiated breath-hold was shown to be an equal alternative to conventional breath-hold imaging.
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| 3. |
- Carlsson, Linn, et al.
(author)
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Surface characteristics of cellulose nanoparticles grafted by surface-initiated ring-opening polymerization of epsilon-caprolactone
- 2015
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In: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 22:2, s. 1063-1074
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Journal article (peer-reviewed)abstract
- In this study, surface-initiated ring-opening polymerization has been employed for the grafting of epsilon-caprolactone from cellulose nanoparticles, made by partial hydrolysis of cellulose cotton linters. A sacrificial initiator was employed during the grafting reactions, to form free polymer in parallel to the grafting reaction. The degree of polymerization of the polymer grafts, and of the free polymer, was varied by varying the reaction time. The aim of this study was to estimate the cellulose nanoparticle degree of surface substitution at different reaction times. This was accomplished by combining measurement results from spectroscopy and chromatography. The prepared cellulose nanoparticles were shown to have 3.1 (+/- 0.3) % of the total anhydroglucose unit content present at the cellulose nanoparticle surfaces. This effectively limits the amount of cellulose that can be targeted by the SI-ROP reactions. For a certain SI-ROP reaction time, it was assumed that the resulting degree of polymerization (DP) of the grafts and the DP of the free polymer were equal. Based on this assumption it was shown that the cellulose nanoparticle surface degree of substitution remained approximately constant (3-7 %) and seemingly independent of SI-ROP reaction time. We believe this work to be an important step towards a deeper understanding of the processes and properties controlling SI-ROP reactions occurring at cellulose surfaces.
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| 4. |
- Erlandsson, Johan, et al.
(author)
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On the mechanism behind freezing-induced chemical crosslinking in ice-templated cellulose nanofibril aerogels
- 2018
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In: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 6:40, s. 19371-19380
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Journal article (peer-reviewed)abstract
- The underlying mechanism related to freezing-induced crosslinking of aldehyde-containing cellulose nanofibrils (CNFs) has been investigated, and the critical parameters behind this process have been identified. The aldehydes introduced by periodate oxidation allows for formation of hemiacetal bonds between the CNFs provided the fibrils are in sufficiently close contact before the water is removed. This is achieved during the freezing process where the cellulose components are initially separated, and the growth of ice crystals forces the CNFs to come into contact in the thin lamellae between the ice crystals. The crosslinked 3-D structure of the CNFs can subsequently be dried under ambient conditions after solvent exchange and still maintain a remarkably low density of 35 kg m-3, i.e. a porosity greater than 98%. A lower critical amount of aldehydes, 0.6 mmol g-1, was found necessary in order to generate a crosslinked 3-D CNF structure of sufficient strength not to collapse during the ambient drying. The chemical stability of the 3-D structure can be further enhanced by converting the hemiacetals to acetals by treatment with an alcohol under acidic conditions.
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