| 1. |
- Mohlin, Kristina, 1970, et al.
(författare)
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Water pores in alkyl ketene dimer (AKD) dispersions studied by NMR diffusometry and optical microscopy
- 2007
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Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - : Elsevier BV. - 1873-4359 .- 0927-7757. ; 297:1-3, s. 114-121
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Tidskriftsartikel (refereegranskat)abstract
- Water borne alkyl ketene dimer (AKD) dispersions have been investigated by means of optical microscopy and NMR diffusometry (NMR-D). In two different formulations, different amounts of entrapped water in pores with different sizes are obtained, which can be compared to a waterin-oil-in-water (w/o/w) dispersion. It is shown that the amount of entrapped water inside the AKD particles can conveniently be measured with the NMR-D technique. The pore size is however not obtained correctly from the NMR-D experiment. Due to the small size of the water pores, the pore size is underestimated when measured with NMR-D. This effect is investigated in more detail by Brownian dynamic simulations from which a correction factor is obtained that allows a more correct value of the pore size from NMR-D measurements. When the pore size is too small to be observed by optical microscopy, typically below 0.5 mu m, NMR diffusometry combined with Brownian dynamic simulations are shown to be a rapid and reliable tool for quantifying the porosity in these types of systems.
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| 2. |
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| 3. |
- Blanck, Hans, 1950, et al.
(författare)
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New strategy for design of optimised combinations of antifoulants: mixture efficacy predictions, risk weighting and microcapsule technology
- 2008
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Ingår i: 14th International Congress on Marine Corrosion and Fouling, July 2008, Kobe Japan.
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Konferensbidrag (refereegranskat)abstract
- Organisms differ in their sensitivity to toxicants, and each biocide will have its own efficacy profile. Whenever an antifoulant is used to affect organisms beyond its high-efficacy profile, an excess of biocides will be emitted to the environment. We propose an unprejudiced and rational design of efficacy-optimised combinations with minimum environmental risk. To control release of several antifoulants independently we use microcapsules bound to a polymer coating. The approach is based on three initial steps: Mixture toxicity concepts are used to predict efficacy of >100 000 combinations of 2-8 antifoulants. Predictions are based on full concentration-efficacy relationships with regard to prevention of settling of fouling model organisms (e.g. periphyton, sea lettuce, barnacles, sea squirt, blue mussel). Based on the predictions we will identify a set of > 100 000 combinations that are efficacious to all model organisms, and define their mixture concentrations and mixture ratios. Risk ratios (e.g. PEC/ PNEC) for the individual antifoulants are then used as weighing factors to rank the combinations according to their estimated relative risk to the environment. This results in a set of promising antifoulant combinations defined by their constituents, mixture ratios and total concentrations in water. The release rate from each of the individual mixture components will be regulated by microcapsule numbers, chemical and physical properties, to deliver the expected combination at the surface of the ship hull. The flexibility of the paint formulation ・with one antifoulant only in each capsule ・suggests that the coating can easily be reformulated to adjust to more demanding conditions. This study is a part of the Marine Paint Research Programme funded by MISTRA, the Foundation for Strategic Environmental Research, Sweden.
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| 4. |
- Hamngren Blomqvist, Charlotte, 1984, et al.
(författare)
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Pore size effects on convective flow and diffusion through nanoporous silica gels
- 2015
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Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - : Elsevier BV. - 0927-7757 .- 1873-4359. ; 484, s. 288-296
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Tidskriftsartikel (refereegranskat)abstract
- Material structure has great impact on mass transport properties, a relationship that needs to be understood on several length scales. Describing and controlling the properties of flow through soft materials are both challenges concerning the industrial use of gel structures. This paper reports on how the porous structure in nanoporous materials affects the water transport through them. We used three different silica gels with large differences in the pore sizes but of equal silica concentration. Particle morphology and gel structure were studied using high-resolution transmission electron microscopy and image analysis to estimate the pore size distribution and intrinsic surface area of each gel. The mass transport was studied using a flow measurement setup and nuclear magnetic resonance diffusometry. The average pore size ranged from approximately 500. nm down to approximately 40. nm. An acknowledged limit for convective flow to occur is in the pore size range between 100 and 200. nm. The results verified the existence of a non-linear relationship between pore size and liquid flow at length scales below 500. nm, experimentally. A factor of 4.3 in flow speed separated the coarser gel from the other two, which presented almost identical flow speed data despite a factor 3 in pore size difference. In the setup, the mass transport in the gel with the largest pores was flow dominated, while the mass transport in the finer gels was diffusion dominated. Besides providing new insights into mass transport as a function of pore sizes, we conclude that three-dimensional analysis of the structures is needed for a comprehensive understanding of the correlation between structure and mass transport properties.
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| 5. |
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| 6. |
- Jonasson, Jenny, 1976, et al.
(författare)
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Pixel-based analysis of FRAP data with a general initial bleaching profile
- 2010
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Ingår i: Journal of Microscopy. - : Wiley. - 0022-2720 .- 1365-2818. ; 239:2, s. 142-153
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Tidskriftsartikel (refereegranskat)abstract
- Jonasson et al. (2008), we presented a new pixel-based maximum likelihood framework for the estimation of diffusion coefficients from data on fluorescence recovery after photobleaching (FRAP) with confocal laser scanning microscopy (CLSM). The main method there, called the Gaussian profile method below, is based on the assumption that the initial intensity profile after photobleaching is approximately Gaussian. In the present paper, we introduce a method, called the Monotone profile method, where the maximum likelihood framework is extended to a general initial bleaching profile only assuming that the profile is a non-decreasing function of the distance to the bleaching centre. The statistical distribution of the image noise is further assumed to be Poisson instead of normal, which should be a more realistic description of the noise in the detector. The new Monotone profile method and the Gaussian profile method are applied to FRAP data on swelling of super absorbent polymers (SAP) in water with a Fluorescein probe. The initial bleaching profile is close to a step function at low degrees of swelling and close to a Gaussian profile at high degrees of swelling. The results obtained from the analysis of the FRAP data are corroborated with NMR diffusometry analysis of SAP with a polyethylene glycol probe having size similar to the Fluorescein. The comparison of the Gaussian and Monotone profile methods is also performed by use of simulated data. It is found that the new Monotone profile method is accurate for all types of initial profiles studied, but it suffers from being computationally slow. The fast Gaussian profile method is sufficiently accurate for most of the profiles studied, but underestimates the diffusion coefficient for profiles close to a step function. We also provide a diagnostic plot, which indicates whether the Gaussian profile method is acceptable or not.
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| 7. |
- Lorén, Niklas, 1970, et al.
(författare)
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Fluorescence recovery after photobleaching in material and life sciences: Putting theory into practice
- 2015
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Ingår i: Quarterly Reviews of Biophysics. - 1469-8994 .- 0033-5835. ; 48:3, s. 323-387
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Tidskriftsartikel (refereegranskat)abstract
- Copyright © 2015 Cambridge University Press.Fluorescence recovery after photobleaching (FRAP) is a versatile tool for determining diffusion and interaction/binding properties in biological and material sciences. An understanding of the mechanisms controlling the diffusion requires a deep understanding of structure-interaction-diffusion relationships. In cell biology, for instance, this applies to the movement of proteins and lipids in the plasma membrane, cytoplasm and nucleus. In industrial applications related to pharmaceutics, foods, textiles, hygiene products and cosmetics, the diffusion of solutes and solvent molecules contributes strongly to the properties and functionality of the final product. All these systems are heterogeneous, and accurate quantification of the mass transport processes at the local level is therefore essential to the understanding of the properties of soft (bio)materials. FRAP is a commonly used fluorescence microscopy-based technique to determine local molecular transport at the micrometer scale. A brief high-intensity laser pulse is locally applied to the sample, causing substantial photobleaching of the fluorescent molecules within the illuminated area. This causes a local concentration gradient of fluorescent molecules, leading to diffusional influx of intact fluorophores from the local surroundings into the bleached area. Quantitative information on the molecular transport can be extracted from the time evolution of the fluorescence recovery in the bleached area using a suitable model. A multitude of FRAP models has been developed over the years, each based on specific assumptions. This makes it challenging for the non-specialist to decide which model is best suited for a particular application. Furthermore, there are many subtleties in performing accurate FRAP experiments. For these reasons, this review aims to provide an extensive tutorial covering the essential theoretical and practical aspects so as to enable accurate quantitative FRAP experiments for molecular transport measurements in soft (bio)materials.
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| 8. |
- MacGregor-Ramiasa, M., et al.
(författare)
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Magnetic alignment of nontronite dispersions
- 2015
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Ingår i: Applied Clay Science. - : Elsevier BV. - 0169-1317. ; 116-117, s. 167-174
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Tidskriftsartikel (refereegranskat)abstract
- The time dependent alignment of exfoliated nontronite dispersions subjected to moderate magnetic field strengths (B.
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| 9. |
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| 10. |
- Nordin, Matias, 1981, et al.
(författare)
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Estimation of mass thickness response of embedded aggregated silica nanospheres from high angle annular dark-field scanning transmission electron micrographs
- 2014
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Ingår i: Journal of Microscopy. - : Wiley. - 0022-2720 .- 1365-2818. ; 253:2, s. 166-170
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we investigate the functional behaviour of the intensity in high-angle annular dark field scanning transmission electron micrograph images. The model material is a silica particle (20 nm) gel at 5 wt%. By assuming that the intensity response is monotonically increasing with increasing mass thickness of silica, an estimate of the functional form is calculated using a maximum likelihood approach. We conclude that a linear functional form of the intensity provides a fair estimate but that a power function is significantly better for estimating the amount of silica in the z-direction. The work adds to the development of quantifying material properties from electron micrographs, especially in the field of tomography methods and three-dimensional quantitative structural characterization from a scanning transmission electron micrograph. It also provides means for direct three-dimensional quantitative structural characterization from a scanning transmission electron micrograph.
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