| 1. |
- Blomberg, E, et al.
(author)
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Adhesion of trimyristin fat to radio frequency plasma treated PVC and chromium
- 1990
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In: Langmuir. - 0743-7463 .- 1520-5827. ; 6, s. 1499-1504
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Journal article (peer-reviewed)abstract
- There is an increasing belief in the use of surface modification techniques to reduce the adhesion of soil to surface so that only weak detergents or mechanical means is required for the soil removal. In this work, we have studied how the soil adhesion is affected by controlled and well-defined modification of thr surface. Various surfaces were prepared by radio frequency plasma treatment combined with surface derivatization techninques. Adsorption and displacement of trimyristin , a model soil, were investigated by ellipsometry. Two fundametally different and succesful approaches to realize a good soil-repellant surface werw found:(i) strongly polar surfaces of poly(ethylene oxide) that interact strongly with water or (ii) surfaces which contain cross-linked fluorocarbon moieties.
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| 2. |
- Blomberg, E, et al.
(author)
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Adsorbed layers of human serum albumin investigated by the surface force technique
- 1991
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In: Journal of Dispersion Science and Technology. - 0193-2691 .- 1532-2351. ; 12, s. 179-200
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Journal article (peer-reviewed)abstract
- The interactions between human serum albumin (HSA) layers adsorbed from solution onto muscovite mica have been investigated by means of surface force measurements. The effects of varying the ionic strength and the serum albumin concentration have been studied at pH=5.5. The negatively charged protein cannot be desorbed from the negatively charged mica surface by dilution with water. The thickness of the (compressed) adsorbed layer is small compared to the dimension of HSA, except at the highest concentration used (1mg/ml). Hence, under a compressive load at low packing densities the protein conformation on the surface is different from that in bulk solution. No adhesion was observed when the amount adsorbed was large. However, an attractive
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| 3. |
- Blomberg, E, et al.
(author)
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Elastohydrodynamic effects with adsorbed layers in surface force measurements
- 1990
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In: Journal of Colloid and Interface Science. - 0021-9797 .- 1095-7103. ; 138, s. 291-293
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Journal article (peer-reviewed)abstract
- When two elastic surfaces carrying adsorbed layers are forced together under high loads, as in measurement with the surface forces apparatus, a bell-shaped deformation develops in the flattened contact zone. This behavior is due to the elastohydrodynamic "lubrication" of the adsorbed layer. Compression of molecules thus trapped between the surfaces may under some cicumstances, e.g., in the cases of surfaces carrying weakly adsorbed proteins, lead to irreversible changes in the adsorbed layer and consequently in the surface interaction.
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| 4. |
- Blomberg, E, et al.
(author)
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Interaction between adsorbed layers of lysozyme studied with the surface force technique
- 1994
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In: Langmuir. - 0743-7463 .- 1520-5827. ; 10, s. 2325-2334
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Journal article (peer-reviewed)abstract
- The surface force technique was employed to investigate the adsorption of positively charged lysozyme onto negatively charged mica surfaces in 10-3 M NaCl at pH 5.6 at lysozyme concentrations ranging from 0.002 to 0.2 mg/ml. At equilibrium the adsorbed lysozyme nearly neutralizes the surface charge of the mica at all bulk lysozyme concentrations investigated. Prior to charge neutralization the decay length of the longrange force is consistent with the electrostatic double-layer force predicted by the DLVO theory. At low concentration, 0.002 mg/ml, a densely packed side-on oriented layer adsorbs on the mica surface. Above 0.02 mg lysozyme/ml, a rather thick layer is adsorbed onto the surface. It consists of an inner, strongly bound layer of both side-on and end-on adsorbed proteins and outer, weakly adsorbed proteins. An adhesion force is established upon contact of the adsorbed protein layers. The force measured between one lysozyme coated surface and one bare mica surface is attractive at short separations. It was demonstrated that at a concentration of 0.02 mg/ml, lysozyme adsorbs "irreversibly" with respect to dilution with 10-3 M NaCl.
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| 5. |
- Blomberg, E, et al.
(author)
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Short-range interaction between adsorbed layers of human serum albumin
- 1994
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In: Journal of Colloid and Interface Science. - 0021-9797 .- 1095-7103. ; 166, s. 427-436
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Journal article (peer-reviewed)abstract
- The adsorption of human serum albumin (HSA) onto muscovite mica has been investigated by means of surface force and ESCA measurements. The range of protein concentration explored was 0.001-1.0 mg/ml in 10-3 M NaCl at pH 5.6. It was found that negatively charged albumin adsorbs onto negatively charged mica. Co-adsorption of small ions into the adsorbed protein layer was also inferred. Small structural changes are induced by the adsorption, and further structural changes can be induced by applying an external compressive force. The structure of the adsorbed layer depends on the surface density. As surfaces with a low adsorption density of HSA are brought together, the protein molecules are able to diffuse along the surface, facilitating the merging of the two HSA layers into one single HSA layer in the gap between the surfaces. At high surface density crowding effects impede the rearrangement of the HSA layers and two separate layers of HSA remain in the gap between the surfaces. An adhesion force is present at low packing but not at high packing densities. It was found that the short-range interaction between one HSA-coated surface and one bare mica surface was strongly attractive, demonstrating that the adhesion forces likely are induced by HSA molecules bridging between two surfaces and not by attractive interactions between the proteins themselves.
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| 6. |
- Claesson, PM, et al.
(author)
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Interactions between fluorocarbon surfaces in aqueous nonionic block copolymer solutions
- 1991
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In: Journal of Colloid and Interface Science. - 0021-9797 .- 1095-7103. ; 147:1, s. 129-136
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Journal article (peer-reviewed)abstract
- The interaction between solid fluorocarbon surfaces immersed in aqueous solutions of a poly(ethylene oxide) - poly(propylene oxide) - poly(ethylene oxide) block copolymer (Proxanol 268) has been determined after different adsorption times. It was found that the compressed layer thickness is independent of the adsorption time, whereas the range of the repulsive force decreases during the first hours. This is interpreted as evidence for a decreasing fraction of polymer tails in the adsorbed polymer layer. A weak attractive force is observed when Proxanol coated surfaces are separated from contact. The presence of this attraction on separation only indicates structural changes in the block copolymer layer when two such layers on opposing surfaces are in contact for a prolonged time. Most of the Proxanol layer is easily desorbed by dilution with water. These results are discussed in connection with the known properties of perfluorocarbon emulsions coated with the same block copolymer.
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| 7. |
- Dahlgren, MAG, et al.
(author)
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Salt effects on the interaction between adsorbed cationic polyelectrolyte layers - Theory and experiment
- 1993
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In: Journal of Physical Chemistry A. - 1089-5639 .- 1520-5215. ; 97, s. 11769-11775
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Journal article (peer-reviewed)abstract
- The effect of inert salt concentration on polyelectrolyte adsorption from aqueous solutions onto oppositely charged surfaces, and the interactions between such surfaces were studied experimentally using a surface force technique and compared to theoretical predictions from Monte Carlo simulations. At a polyelectrolyte concentration of 10 ppm and a low inert salt concentration (10-4 M) the polyelectrolytes adsorb in a flat conformation and the force acting between the surfaces is close to zero down to a separation of 10-15 nm, where the surfaces jump inwards. The attractive force observed at separations below 10 nm is stronger than the expected van der Waals force. The magnitude and range of the attraction agrees with forces obtained from Monte Carlo simulation and we interpret the attraction as being due to bridging polyelectrolytes. When the salt concentration is increased, additional polyelectrolyte adsorption takes place. This gives again rise to a repulsive force, which is significantly larger than what is observed between bare surfaces. The extra repulsion is due to adsorbed polyelectrolytes stretching out from the surfaces and is also predicted from simulations.
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| 8. |
- Elenius, K.O.E., et al.
(author)
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Experiments with artificial neural networks for phoneme and word recognit
- 1993
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In: STL-QPSR. ; 34:1, s. 47-56
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Journal article (peer-reviewed)abstract
- An artificial neural network has been bained by the error back-propagation technique to recopse phonemes and words. The speech material was recorded by a male Swedish talker and was labelled by a phonetician. There were 38ou put nodes corresponding to Swedish phonemes. Introducing coarticulation information by adding simple recurrency to the net is shown to be more effective than expanding the size of the input spectral window. The phoneme recognition network was used with dynamic programming for time alignment to recognise connected digits in a speakerindependent way. It was compared to a similar recogniser based on nine quasi-phonetic features instead of 38phonemes. The phoneme-based system performed better fhan the feature-based one for five out of seven speakers.
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| 9. |
- Erlandson, R. E., et al.
(author)
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Freja observations of electromagnetic ion cyclotron ELF waves and transverse oxygen ion acceleration on auroral field lines
- 1994
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In: Geophysical Research Letters. - 0094-8276. ; 21:17, s. 1855-1858
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Journal article (peer-reviewed)abstract
- Extremely low-frequency (ELF) magnetic and electric field plasma wave emissions were recorded on 2 October 1993 on auroral field lines by the Magnetic Field Experiment during Freja orbit 4770. The ELF wave frequencies were below the local oxygen gyrofrequency (25 Hz) and between the helium and proton gyrofrequencies (100 to 400 Hz). The ELF waves, interpreted as electromagnetic ion cyclotron (EMIC) waves, were observed in a region of inverted-v-type electron precipitation. The EMIC waves were correlated over time with auroral and lower energy (≈ 100 eV) electrons, which are both possible sources of free energy, and also with transversely accelerated oxygen ions. The waves above the helium gyrofrequency were more closely correlated with the transverse oxygen ion acceleration than the waves below the oxygen gyrofrequency. These observations are consistent with a scenario in which electron beams generate EMIC waves, which then produce transverse oxygen ion acceleration through a gyroresonant interaction.
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| 10. |
- Feldstein, Y. I., et al.
(author)
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Electromagnetic weather at 100 km altitude on 3 August 1986
- 1994
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In: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 21, s. 2095-2098
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Journal article (peer-reviewed)abstract
- The electromagnetic weather at high altitudes above the Earth’s surface is determined by the transport of ionospheric plasma, which in turn is governed by the magnitude as well as the direction of the electric and magnetic fields. Different models [Levitin et al., 1984; Friis-Christensen et al., 1985; Mishin, 1990] have been proposed that allow an estimation of the electromagnetic parameters of the upper atmosphere, given a knowledge of the magnitude and orientation of the interplanetary magnetic field. Here we use one such model to estimate the global convection pattern and its temporal evolution during a pass of the Swedish satellite Viking over the northern polar cap. The model predictions are shown to agree well with the electric and magnetic fields measured along the satellite trajectory. The good agreement implies that the model can be used to reconstruct, with reasonable confidence, the large-scale distribution of electric and magnetic fields and their time-variation in the entire auroral ionosphere.
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| 11. |
- Malmsten, M, et al.
(author)
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Mucin layers on hydrophobic surfaces studied with ellipsometry and surface force measurements
- 1992
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In: Journal of Colloid and Interface Science. - 0021-9797 .- 1095-7103. ; 151, s. 579-590
-
Journal article (peer-reviewed)abstract
- The forces acting between layers of gastric mucins from rat (RGM) and pig (PGM) adsorbed on to hydrophobized mica surfaces were investigated by using the surface force technique, whereas information on the kinetics and the reversibility of the adsorption process was obtained with ellipsometry. From the surface force measurements, we found that the amount adsorbed from a 0.1 mg/ml RGM solution was 3.5±1.5 mg/m2 at adsorption equilibrium, within experimental error equal to that (about 3 mg/m2) found with ellipsometry. The forces obtained with RGM were purely repulsive, whereas those displayed by PGM were partially attractive. Dilution of the bulk solution caused only minor desorption and the interaction force between the RGM layers was only weakly dependent on the excess electrolyte concentration. Hence, steric forces predominate the interaction in the RGM system. Both RGM and PGM adsorb in a flat conformation, with compressed adsorbed layer thicknesses of 10-20 nm and 3-4 nm, respectively. The interaction force was essentially reversible on approach and separation for RGM, whereas 'relaxation effects' were prominent for PGM layers.
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| 12. |
- Parker, JL, et al.
(author)
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Plasma modification of mica
- 1990
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In: Journal of Colloid and Interface Science. - 0021-9797 .- 1095-7103. ; 134, s. 449-458
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Journal article (peer-reviewed)abstract
- When mica is exposed to a low temperature nonpolymer-forming plasma the surface structure is altered by a combination of sputtering and chemical reaction with reactive species in the plasma. The chemical composition of the surface is altered without a significant increase in surface roughness under optimal conditions. The effect of the plasma process parameters (exposure time, power, flow rate, and pressure) on the extent of surface modification has been investigated by means of ESCA and contact angle measurements. After exposure to water vapor plasma the mica surface becomes reactive to silanation with chlorosilanes in the gas phase. The durability of mica surfaces modified by plasma treatment and subsequent reaction with some chlorosilanes has been investigated. The forces between water plasmatreated surfaces after silanation have been measured using a surface force apparatus.
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| 13. |
- Tilton, RD, et al.
(author)
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Effect of anionic surfactant on interactions between lysozyme layers adsorbed on mica
- 1993
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In: Langmuir. - 0743-7463 .- 1520-5827. ; 9, s. 2102-2108
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Journal article (peer-reviewed)abstract
- Protein-surfactant interactions play a key role in competitive adsorption and desorption of adsorbed proteins by surfactants. The influence of nonmicellar solutions of an anionic surfactant, sodium dodecane-sulfonate, on the interaction forces between preadsorbed layers of Iysozyme on mica were investigated using the surface force apparatus. In the absence of surfactant, Iysozyme adsorbs irreversibly and neutralizes the negative mica surface charge. The force profile indicates that the adsorbed layer is heterogeneous and deformable, consisting of protein monomers and loosely associated dimers. An adhesion force is established upon contact of the adsorbed layers. Surfactant binding increases the interfacial charge and eliminates the adhesion force between opposing surfaces. Large-scale desorption or conforma-tional change in response to surfactant binding is not observed, although partial desorption of the outer members of adsorbed dimers is induced at the highest surfactant concentration investigated.
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