| 1. |
- Cho, DL, et al.
(författare)
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Structure and surface properties of plasma polymerized acrylic acid layers
- 1990
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Ingår i: Journal of Applied Polymer Science. - 0021-8995 .- 1097-4628. ; 41, s. 1373-1390
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Tidskriftsartikel (refereegranskat)abstract
- Thin plasma polymerized layers of acrylic acid (PPAA) were deposited onto polyethylene and muscovite mica surfaces. Structure and surface properties of the deposited layer depend on the polymerization conditions. The content of carboxylic groups in the layer decreases, whereas the degree of crosslinking or branching increases, with increasing discharge power. A soft, sticky layer with a low contact angle against water is obtained when a low discharge power (5 W) is used. In contrast, a hard film with a rather high water contact angle is obtained when the discharge power is high (50 W). A surface force apparatus was employed to study some film properties including adhesion force, crack formation, and capillary condensation. The adhesion force between plasma polymerized acrylic acid layers prepared at a low discharge power is high in dry air. It decreases remarkably in humid air and no adhesion is observed in water. In dry air, the adhesion force between PPAA layers decreases as the discharge power increases.
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| 2. |
- Malmsten, M, et al.
(författare)
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Forces between proteoheparan sulfate layers adsorbed at hydrophobic surfaces
- 1994
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Ingår i: Langmuir. - 0743-7463 .- 1520-5827. ; 10, s. 1274-1280
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Tidskriftsartikel (refereegranskat)abstract
- The forces between proteoheparan sulphate layers adsorbed at hydrophobic surfaces were investigated by direct surface force measurements. In 0.2 mg/ml proteoheparan sulphate and 0.1 mM NaCl, the forces were monotonically repulsive, with one distant regime having a decay length of about 180 Å, and one steeply repulsive proximal part at distances smaller than about 100 Å. Only small effects were observed on dilution with 0.1 mM NaCl, indicating ”irreversible” adsorption. The decay length of the distant force component was 280 Å after dilution, whereas the proximal repulsive component remained unchanged. Furthermore, after dilution, a weak adhesion (F/R = 200 mN/m) was observed. At addition of CaCl2, the decay length of the distant repulsion decreased from 280 Å in 0.1 mM NaCl to 86 Å and 77 Å in 1.25 and 2.5 mM CaCl2, respectively. The deacay-lenghts in CaCl2 solutions are significantly larger than the expected Debye-lengths, demonstrating the predominance of steric forces. Furthermore, on addition of CaCl2 the magnitude of the adhesion increased from 200 mN/m to 1000 mN/m, and the proximal repulsion was observed at slightly smaller distances. It was found that both steric and electrostatic forces contribute to the interactions between proteoheparan sulphate layers
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| 3. |
- Stenius, P, et al.
(författare)
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Nonionic hydrophilic surfaces: adsorption and interactions
- 1990
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Ingår i: Croatica Chemica Acta. - 0011-1643 .- 1334-417X. ; 63, s. 501-516
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Tidskriftsartikel (refereegranskat)abstract
- An overview is given of recent studies of nonionic, hydrophilic surfaces formed by the adsorption surfactants or surface active polymers. Hydrophobic surfaces can be easily hydrophilized by the adsorption of nonionic surfactants or block copolymers containing hydrophobic chain segements; the cooperative interaction between the hydrocarbon moieties contributes more to the free energy of adsorption than the interaction with the hydrophobic surface. Hydrophilic layers are also readily formed on hydrophilic surfaces provided specific interaction between the hydrophilic end groups and the surface creates a sufficiently hydrophobic surface so that a second layer can bed formed through cooperative interaction. The temperature dependence of the interaction forces between layers of surfactants can be closely correlated with their phase equilibria with water. In order to prevent protein adsorption the surface should be neither charged nor hydrophobic; it is shown that, accordingly, protein adsorption is extremely low on poly ethylene oxide-covered surfaces.
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| 4. |
- Öhlander, Björn, et al.
(författare)
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Delineation and character of the Archaean-Proterozoic boundary in northern Sweden
- 1993
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Ingår i: Precambrian Research. - 0301-9268 .- 1872-7433. ; 64:1-4, s. 67-84
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Tidskriftsartikel (refereegranskat)abstract
- Before the deposition of a Proterozoic cover and the repeated Proterozoic reworking of the older rocks, the presently exposed Archaean areas in northern Sweden formed part of a coherent craton. In the present study, we have used Sm---Nd isotopic analyses of Proterozoic granitoids and metavolcanics to delineate the Archaean palaeoboundary. In a regional context, the transition from strongly negative εNd(t) values in the northeast to positive values in the southwest is distinct, and approximately defines the border of the old craton. The Archaean palaeoboundary extends in a WNW direction, and is subparallel to the longitudinal axis of the Skellefte sulphide ore district but it is situated ≈ 100 km farther to the north. The ≈ 1.9 Ga old granitoids on the two sides of the palaeoboundary were all formed in compressional environments, but those situated to the north have higher contents of LILE and LREE at similar contents of Si. This indicates that they were generated in an area with thicker crust and supports the location of the Archaean-Proterozoic palaeoboundary. There is no simple correlation between the Archaean palaeoboundary, as defined by the isotopic results, and any of the major fracture systems as interpreted from regional geophysical measurements. Reflection seismic work indicates that juvenile volcanic-arc terrains to the south have been thrust onto the Archaean craton. Possible thrust faults have been identified from aeromagnetic measurements. Rifting of the Archaean craton created a passive margin ≈ 2.0 Ga ago. Spreading shifted to convergence with subduction beneath the Archaean continent ≈ 1.9 Ga ago. Subsequently, the resulting juvenile volcanic arc collided with the old continent, and the Archaean palaeoboundary as existing today was formed by a collision characterized by overthrusting. The boundary then was disturbed by later deformation predominantly along NNE-trending fracture systems.
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