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  • 301. Delgado, C
    et al.
    Malmsten, M
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Van Alstine, JM
    Analytical partitioning of poly(ethyleneglycol)-modified proteins1997In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 692, p. 263-272Article in journal (Refereed)
    Abstract [en]

    Covalently grafting proteins with varying numbers (n) of poly(ethylene glycol) molecules (PEGs) often enhances their biomedical and industrial usefulness. Partition between the phases in aqueous polymer two-phase systems can be used to rapidly characterize polymer-protein conjugates in a manner related to various enhancements. The logarithm of the partition coefficient (K) approximates linearity over the range 0

  • 302. Dickinson, E
    et al.
    Eriksson, L
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Particle flocculation by adsorbing polymers1991In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 34, p. 1-29Article in journal (Refereed)
    Abstract [en]

    The flocculation of colloidal particles by adsorbing polymers is a phenomenon of considerable scientific and industrial importance. This article describes recent developments in the field with particular reference to flocculation of negatively charged particles by high-molecular-weight cationic polyelectrolytes by polymer bridging or charge neutralization. Experimental and theoretical studies of interactions between adsorbed polymer layers give insight into the favourable conditions for bridging flocculation. Neutron scattering and computer simulation give insight into the relationship between floc structure and the mechanism of flocculation.

  • 303. Dickinson, Eric
    et al.
    Bergenståhl, Björn
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Food colloids: Proteins, Lipids and Polysaccharides1997Book (Other academic)
  • 304. Djuve, J
    et al.
    Grant, LM
    Sjöblom, J
    Goloub, TP
    Pugh, RJ
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Templating of ethyl(hydroxyethyl) cellulose on graphite by surfactant-polymer interactions2002In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 18, p. 2673-2677Article in journal (Refereed)
    Abstract [en]

    Ordered, templated, thin films of ethyl(hydroxyethyl)cellulose (EHEC) were produced on a freshly cleaved crystalline graphite surface by exploiting the nature of sodium dodecyl sulfate adsorption (SDS) and its interaction with EHEC. The films were prepared by exposing the graphite surface to a dilute aqueous solution containing EHEC-SDS mixtures, followed by rinsing to remove the SDS and drying. The structure of the remaining EHEC film at the graphite-air interface was investigated by atomic force microscopy and compared with images of SDS and EHEC polymer on adsorbed graphite obtained in separate experiments. The results showed that polymer networks were formed from the EHEC-SDS mixture (after rinsing out the SDS), which were predominately aligned in one of three preferential directions separated by 60°, presumably as a result of templating by coadsorbed SDS. In addition, the alignment of the EHEC polymer and spacing between the polymer strands was found to be a function of surfactant concentration. Films formed from a solution containing EHEC (10 ppm) and SDS solution (5 mM) after removal of the SDS by washing formed "tight", highly aligned networks. At the same EHEC concentration and 20 mM SDS, a more "open" structure was formed. The results provide valuable insights into the interaction and organization of SDS and EHEC at a crystalline hydrophobic surface.

  • 305. Djuve, J
    et al.
    Pugh, RJ
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Sjöblom, J
    Foaming and dynamic surface tension of aqueous polymer/surfactants solutions 1: ethyl(hydroxyethyl) cellulose and sodium dodecyl sulphate2001In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 186, p. 189-202Article in journal (Refereed)
    Abstract [en]

    Foaming (in a column) and dynamic surface tension behaviour of aqueous solutions of sodium dodecyl sulphate (SDS), and ethyl (hydroxy ethyl) cellulose/ sodium dodecyl sulphate (EHEC/SDS) mixtures was determined. The results indicated a synergism in foaming and surface activity for the EHEC/SDS mixtures over a specific concentration range. For the SDS solution, the maximum value in Marangoni Elasticity (EM max), as determined from dynamic surface tension data, was reached within a surface age of 0.05s and it could be suggested that in this case EM max was relevant to foam stability. However, for the EHEC (non-foaming solutions), EM max was reached after longer surface ageing periods (0.05-0.1 s). For the EHEC/SDS solutions, EM max occurred over a range of surface ageing periods depending on the polymer/surfactant ratio and no correlation was obtained between EM max and foaming. The EM max time lag for the polymer and polymer/surfactant mixtures was explained by the slower diffusion from solution to the new surface. For the EHEC/SDS, the enhanced the foaming behaviour was explained by the adsorption of surface active polymer/surfactant (clusters) species at the air/solution interface. It was suggested that this could lead to coherent (gelatinous) interfacial layers in the thin film lamella which reduce drainage from the central fluid.

  • 306. Duner, G
    et al.
    Thormann, E
    Ramstrom, O
    Dedinaite, A
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Letter to the editor: Friction between surfaces-polyacrylic acid brush and silica-mediated by calcium ions2010In: Journal of Dispersion Science and Technology, ISSN 0193-2691, E-ISSN 1532-2351, Vol. 31, no 10, p. 1285-1287Article in journal (Refereed)
    Abstract [en]

    With this letter, we report how friction can be controlled by inducing physical bonds solely within a polyelectrolyte brush layer, while keeping repulsive interactions between the brush layer and the bare surface that slides above. Our results imply that the nature of the bare surface is of minor importance as long as the repulsive surface interaction is maintained.

  • 307.
    Dunér, Gunnar
    et al.
    KTH Royal Institute of Technology, Sweden.
    Iruthayaraj, Joseph
    Aarhus University, Denmark.
    Daasbjerg, Kim
    Aarhus University, Denmark.
    Pedersen, Steen Uttrup
    Aarhus University, Denmark.
    Thormann, Esben
    KTH Royal Institute of Technology, Sweden.
    Dedinaite, Andra A.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet. KTH Royal Institute of Technology, Sweden.
    Attractive double-layer forces and charge regulation upon interaction between electrografted amine layers and silica2012In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 385, no 1, p. 225-234Article in journal (Refereed)
    Abstract [en]

    Amine functionalities have been introduced on glassy carbon surfaces through electrografting of 4-(2-aminoethyl)benzenediazonium tetrafluoroborate. The grafted layers were characterized by ellipsometry and by nanomechanical mapping in air and aqueous solutions using the atomic force microscopy PeakForce QNM mode. The layer was found to be 2.5. nm thick with low roughness, comparable to that of the glassy carbon substrate. However, small semi-spherical features were observed in the topographical image, indicating a clustering of the grafted amine compound. The nanomechanical mapping also demonstrated some swelling of the layer in water and pointed toward an important contribution of electrostatic interactions for the tip-surface adhesion. The forces between an aminated glassy carbon surface and a μm-sized silica particle in aqueous solutions were measured at different ionic strength and pH-values. The results demonstrate that an attractive double-layer force predominates at large separations, and that the surface charge densities increase as the separation between the surfaces decreases. The degree of charge regulation on the aminated glassy carbon is significant. The relatively low surface charge density of the aminated glassy carbon is attributed to significant incorporation of counterions in the water-rich grafted layer.

  • 308.
    Dunér, Gunnar
    et al.
    KTH Royal Institute of Technology, Sweden.
    Thormann, Esben
    KTH Royal Institute of Technology, Sweden.
    Dedinaite, Andra
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet. KTH Royal Institute of Technology, Sweden.
    Claesson, Per M
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet. KTH Royal Institute of Technology, Sweden.
    Matyjaszewski, Krzysztof
    Carnegie Mellon University, USA.
    Tilton, Robert D.
    Carnegie Mellon University, USA.
    Nanomechanical mapping of a high curvature polymer brush grafted from a rigid nanoparticle2012In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 8, no 32, p. 8312-8320Article in journal (Refereed)
    Abstract [en]

    Analysis of interaction forces when probing a silica core-polyelectrolyte brush shell nanoparticle, adsorbed on a silica substrate and bathed by aqueous electrolyte solution, with an ultrasharp atomic force microscopy (AFM) tip provides a spatially resolved map of heterogeneous mechanical properties across the nanoparticle. The deformation of the brush is mainly compressive when probed directly above the nanoparticle centre and mainly deflective when probed at a finite horizontal distance away from the centre. The brush is significantly stiffer against compression than against deflection, and ionization of the brush has a greater stiffening effect against compression than deflection. Whereas a height image of the core-shell nanoparticle was unremarkable, showing a monotonic decrease in height with increasing horizontal distance from the centre, brush deformation, energy dissipation and adhesion displayed local minima over the centre and maxima at a finite horizontal distance away from the centre, corresponding to a position near the rigid core nanoparticle edge. The different response to brush deformation depending on the angle of probing is relevant to the interactions of brush-decorated macroscopic surfaces with submicrometer roughness and to the interactions of brush-decorated nanoparticles with ultrafine structures in their environments.

  • 309. Dunér, Gunnar
    et al.
    Thormann, Esben
    Ramström, Olof
    Dédinaité, Andra
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Friction between surfaces - Polyacrylic acid brush and silica - mediated by calcium ions2010In: Journal of Dispersion Science and Technology, ISSN 0193-2691, E-ISSN 1532-2351, Vol. 31, no 10, p. 1285-1287Article in journal (Refereed)
    Abstract [en]

    With this letter, we report how friction can be controlled by inducing physical bonds solely within a polyelectrolyte brush layer, while keeping repulsive interactions between the brush layer and the bare surface that slides above. Our results imply that the nature of the bare surface is of minor importance as long as the repulsive surface interaction is maintained.

  • 310.
    Dédinaité, A
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Ernstsson, Marie
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Chitosan-SDS interactions at a solid-liquid interface: Effects of surfactant concentration and ionic strength2003In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 107, p. 8181-8188Article in journal (Refereed)
    Abstract [en]

    The effect of ionic strength on adsorption of chitosan on mica as well as the impact of addition of an anionic surfactant, SDS, on the adsorbed chitosan layers is explored. It is demonstrated by chemical surface analysis (ESCA) and surface force measurements (SFA) that an elevated salt concentration leads to larger adsorbed amounts and thicker adsorption layers of this cationic polyelectrolyte. It is also shown that in contrast to the bulk, the binding of oppositely charged surfactant to the polyelectrolyte adsorbed on a negatively charged surface is facilitated by elevated ionic strength. Thus, the association process in bulk and at solid-liquid interfaces is rather different. The main point of difference is that at the solid-liquid interface one also has to consider interactions between the polyelectrolyte and the surface as well as between the surfactant and the surface.

  • 311.
    Dédinaité, A
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Pettersson, T
    Mohanty, B
    Claesson, PM
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Lubrication by organized soft matter2010In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 6, no 7, p. 1520-1526Article in journal (Refereed)
    Abstract [en]

    The AFM-colloidal probe technique has been used to explore surface interactions and friction forces between polyelectrolyte-coated surfaces immersed in aqueous solutions in the absence and presence of surfactant. It is found that the nature of the load bearing forces is decisive for the lubricating properties of the layers. Low frictional forces are obtained when the load is carried by a force that allows the interfacial layer to have a high fluidity, whereas attractive surface forces most often increase the friction. Highly charged polyelectrolytes and oppositely charged surfactants associate in bulk solution to form complexes with a well-defined internal structure. At the surface, similarly structured polyelectrolyte-surfactant layers are spontaneously formed. Such layers have a high load bearing capacity, and the friction coefficient is very low as long as the integrity of the layer remains intact. Interestingly, when the load is increased step-wise the friction force as a function of load displays some sharp peaks, which are identified as being due to structural rearrangements in the polyelectrolyte-surfactant layer. On unloading very low frictional forces are obtained despite the presence of an adhesion between the layers. To maintain the favorable lubricating properties it is essential to have surfactants present in solution, whereas, after the initial adsorption step, there is no need to have the polyelectrolyte present in the bulk. The reason for this is the essentially irreversible adsorption of the polyelectrolyte.

  • 312.
    Dédinaité, Andra
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Biomimetic lubrication2012In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 8, no 2, p. 273-284Article in journal (Refereed)
    Abstract [en]

    The lubrication of synovial joints is extremely efficient, allowing smooth motion to be performed between relatively soft and vulnerable cartilage surfaces for close to 100 years. A failure of this system leads to significant pain and loss of life quality. The ultrastructure of cartilage is complex and of functional significance. The molecules that are involved in the lubrication process are of many types, and they associate with each other in a complex fashion. This review focuses on the lubricating molecules, both biolubricants and biomimetic ones that share some features of the biolubricants. It discusses the conditions that must be fulfilled for achieving low friction in aqueous media and emphasizes the importance of load bearing capacity and self-healing ability.

  • 313.
    Dédinaité, Andra
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Interfacial properties of mucins2010In: Encyclopedia of Surface and Colloid Science, Second Ed., Taylor & Francis, 2010, p. 1-17Chapter in book (Refereed)
    Abstract [en]

    Mucins are a very abundant class of glycoproteins present on most internal interfaces in most organisms in the animal kingdom. They fulfill many functions related to hydration, lubrication, and protection and also in recognition events and cell signaling. Despite the great importance of mucins, it is fair to say that even today the understanding of the interfacial properties of mucins is limited. One reason for this is the great variation in mucin structure. Mucins can be secreted or they can be membrane‐bound, their molecular weight can be vastly different, and their charge density varies, but most importantly, the unlimited number of ways that the carbohydrate moieties can be assembled provides a structural variation that is enormous. Thus, different mucins behave differently in solution, they aggregate differently, and they have very different interfacial properties. This has yet not been investigated in a systematic manner and thus the structure–property relations are not fully clear. However, different mucins do show general structural similarities, and some general features of their interfacial properties also display similarities. This review seeks to elucidate these similarities and tries to relate them to common physical chemical characteristics, which are also key elements for their functions in living organisms.

  • 314.
    Dédinaité, Andra
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Monolayer properties probed by surface forces measurements: Chapter 22007In: Advanced Chemistry of Monolayers at Interfaces: Trends in Methodology and Technology, Elsevier, 2007, p. 23-53Chapter in book (Refereed)
  • 315.
    Dédinaité, Andra
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Thormann, Esben
    Olanya, Geoffrey
    Claesson, Per M
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Nyström, Bo
    Kjøniksen, Anna-Lena
    Friction in aqueous media tuned by temperature-responsive polymer layers2010In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 6, no 11, p. 2489-2498Article in journal (Refereed)
    Abstract [en]

    An atomic force microscope colloidal probe technique has been employed to probe normal and friction forces between silica surfaces coated with adsorbed layers of a diblock copolymer of the composition poly(N-isopropylacrylamide)48-block-poly(3-acrylamidopropyl)trimethylammonium chloride)20, abbreviated PNIPAAM48-b-PAMPTMA(+)20. The interactions between the PNIPAAM48-b- PAMPTMA(+)20-coated surfaces across a 0.1 mM NaCl (pH 6) solution at 25 _x0002_C are purely repulsive, due to a combination of steric and electrostatic double-layer forces. However, when the temperature is increased to 35 _x0002_C, and subsequently to 45 _x0002_C, an attractive force develops at short separations due to the unfavourable PNIPAAM–water interaction at these temperatures. The temperature-dependent polymer–water interaction has implications for the friction force between the layers. At 25 _x0002_C a frictional force that increases linearly with increasing load is observed once the surfaces are brought into close contact. At higher temperatures significantly higher friction forces appear as a consequence of attractive segment–segment interactions. Further, a clearly expressed hysteresis between friction forces encountered on loading and unloading is detected. Our results demonstrate that both normal and friction forces between surfaces can be controlled by temperature changes when temperatureresponsive polymers are employed, and friction forces can be adjusted as required from low to high.

  • 316.
    Ederth, T
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Substrate and solution effects on the long-range "hydrophobic" interactions between hydrophobised gold surfaces2000In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 104, p. 9704-9712Article in journal (Refereed)
    Abstract [en]

    Hydrophobic surfaces prepared by adsorption of hexadecanethiol, 1,10-dithiodecane, octadecanoic acid, and hexadecanol onto gold have been used to study long-ranged "hydrophobic" interactions, and direct force measurements were performed in water, aqueous NaCl electrolytes, and water/ethanol mixtures, using a bimorph surface force instrument. Results confirm that for very stable hydrophobic surfaces the contact angle is sufficient to predict the presence of an attraction in excess of van der Waals forces, in which case the attraction is caused by the coalesence of microscopic bubbles on the surfaces. For the less stable hydrophobic films, the properties of the adsorbed layer is important for the qualitative nature of the interaction. For such surfaces different -- and as yet unknown -- mecanisms cause the attraction

  • 317.
    Ederth, T
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Template-stripped gold surfaces with 0.4-nm rms roughness suitable for force measurements: Application to the Casimir force in the 20-100 nm range2000In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 62, p. 0621041-8Article in journal (Refereed)
    Abstract [en]

    Using a template-stripping method, macroscopic gold surfaces with root-mean-square (rms) roughness less than 0.4 nm have been prepared, making them useful for studies of surface interactions in the nanometer range. The utility of such substrates is demonstrated by measurements of the Casimir force at surface separations between 20 and 100 nm, resulting in good agreement with theory. The significance and quantification of this agreement is addressed, as well as some methodological aspects regarding the measurement of the Casimir force with high accuracy

  • 318.
    Ederth, T
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Claesson, P
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Forces between carboxylic acid surfaces in divalent electrolyte solutions2000In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 229, p. 123-128Article in journal (Refereed)
    Abstract [en]

    The behaviour of self-assembled monolayers of thiohexadecanoic acid adsorbed onto gold interacting in assymmetric 2:1 electrolytes has been studied with direct force measurements. The effects of two divalent cations (Mg2+ and Ca2+) were studied at concentrations ranging from 1 µM to 10 mM. As compared to interactions in the presence of Na+, the divalent ions adsorb strongly to the surfaces, with the effect of lowering the surface potential, and decreasing the double-layer repulsion. At concentrations above 10 µM, the Ca2+ ions were found to adsorb stronger than Mg2+, causing charge reversal at higher concentrations, and the net interactions at 10 mM were attractive over the measurable range.

  • 319. Ederth, T
    et al.
    Claesson, P
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Liedberg, B
    Self-assembled monolayers of alkanethiolates on thin gold films as substrates for surface force measurements. Long-range hydrophobic interactions and electrostatic double-layer interactions1998In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 14, p. 4782-4789Article in journal (Refereed)
    Abstract [en]

    Surfaces prepared by self-assembly of alkanethiolates onto thin (10 nm) gold films supported on glass have been used as substrates for surface force measurements between macroscopic surfaces. Surface roughness, the order in the monomolecular film, wetting properties and their stability in aqueous electrolyte solutions have been investigated using atomic force microscopy, infrared absorption spectroscopy, and contact angle measurements. Direct force measurements have been performed with a non-interferometric bimorph surface force apparatus, using surfaces with differently functionalised thiolates; measurements were made in air, water and aqueous electrolyte solutions. Results from force measurements between hydrophobic and neutral hydrophilic surfaces in air and water are presented and discussed, as well as some results from measurements with surfaces exposing carboxylic groups in various aqueous electrolyte solutions. It is demonstrated that alkanethiol monolayers self-assembled onto thin gold films on macroscopic surfaces are well suited as substrates for direct measurements of long-range surface forces. The utility of these surfaces as substrates for investigations of short-range phenomena is limited until the effect of the roughness on the adhesion between the surfaces has been properly quantified, and the contribution of the van der Waals force to the total interaction has been calculated. The latter is difficult to assess due to the large number of layers in the system, and the presence of conducting surfaces.

  • 320.
    Ederth, T
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Liedber, g B
    Influence of wetting properties on the long-range "hydrophobic" interaction between self-assembled alkylthiolate monolayers2000In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 16, p. 2177-2184Article in journal (Refereed)
    Abstract [en]

    The effect of solid-liquid interfacial energy on the long-range attraction between self-assembled thiolate monolayers in water has been studied by direct force measurements. The solid-liquid interfacial energy was tuned by changing the properties of the solid surface: the thiolate monolayers were prepared by self-assembly of mixtures of methyl- and hydroxyl- functionalized alkylthiols onto thin gold films. The wetting properties were examined by contact angle measurements with the Wilhelmy plate method. Our results show that the shape of the long-ranged attractive force is sensitive to the advancing solid-liquid contact angle: whenever it exceeds 90° the force profiles are discontinuous and contains steps, whereas no attraction beyond the van der Waals force is observed for contact angles lower than 90°. We attribute the steps in the long-range attraction between hydrophobic surfaces to bridging of microscopic bubbles residing on the surfaces, and we conclude that the stability of these bubbles are related to macroscopic contact angles.

  • 321. Ederth, T
    et al.
    Tamada, K
    Claesson, PM
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Valiokas, R
    Colorado, Jr R
    Graupe, M
    Force measurements between semifluorinated thiolate self-assembled monolayers: Long-range hydrophobic interactions and surface charge2001In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 235, p. 391-397Article in journal (Refereed)
    Abstract [en]

    Long-range interactions between self-assembled monolayers (SAMs) of semifluorinated alkanethiols have been studied by direct force measurements in water and aqueous NaCl solutions. SAMs prepared from three different thiols, with identical fluorinated headgroups but varying hydrocarbon spacer lengths, were investigated: CF3(CF2)9(CH2)xSH, where x = 2, 11, or 17. Force measurements show that the interactions in water and electrolyte solutions are composed of both double-layer interactions emerging from what appears to be charges adsorbed onto the surfaces, and long-range "hydrophobic" attractions, in excess of the expected van der Waals forces. The three investigated thiols produce similar results in force measurements, though the contact angles with water are slightly different. The "hydrophobic" attraction has the form of step-like attractive discontinuities in the force profiles at separations ranging from 20 to 40 nm, caused by bridging of microscopic bubbles residing at the surfaces. The shape or range of these discontinuities are not significantly affected by replacement of the water with either 1 mM or 1 M NaCl solutions. The origin of the charges causing the electrostatic double-layer interaction is unclear, but some possible causes are discussed.

  • 322. Ekholm, P
    et al.
    Blomberg, E
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Claesson, P
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Auflem, IH
    Sjöblom, J
    Kornfeldt, A
    A quartz crystal microbalance study of the adsorption of asphaltenes and resins onto a hydrophilic surface2002In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 247, p. 342-350Article in journal (Refereed)
    Abstract [en]

    The adsorption of extracted and purified samples of asphaltenes and resins onto gold surfaces has been studied as a function of bulk concentration using a quarts crystal microbalance with dissipation measurements (QCM-D). With this device, which works equally well in transparent, opaque, and nontransparent samples, the adsorbed amount is measured through a change in resonant frequency of the quartz oscillator. The measured change in dissipation reports on changes in layer viscoelasticity and slip of the solvent at the surface. The results show that the adsorbed amount for resins from heptane corresponds to a rigidly attached monolayer. The adsorbed amount decreases with increasing amount of toluene in the solvent and is virtually zero in pure toluene. Asphaltenes, on the other hand, adsorb in large quantities and the mass and dissipation data demonstrate the presence of aggregates on the surface. The aggregates are firmly attached and cannot be removed by addition of resins. On the other hand, resins and asphaltenes associate in bulk liquid and the adsorption from mixtures containing both resins and asphaltenes is markedly different from that obtained from the pure components. Hence, we conclude that preformed resin aggregates adsorb to the surface. These results are compared and discussed in relation to adsorption from crude oil diluted in heptane/toluene mixtures

  • 323.
    Ekwall, P
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Associations- och ordningstillstånd i system av amfifila ämnen1967In: Svensk Kemisk Tidskrift, ISSN 0371-0742, Vol. 79, no 11, p. 605-623Article in journal (Refereed)
  • 324.
    Ekwall, P
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Two types of micelle formation in organic solvents1968In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 29, p. 16-26Article in journal (Refereed)
  • 325.
    Ekwall, P
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Eikrem, H
    Stenius, P
    The properties and structures of aqueous sodium caprylate solutions : V theactivity of water and sodium caprylate1967In: Acta Chemica Scandinavica, ISSN 0904-213X, E-ISSN 1902-3103, Vol. 21, p. 1639-1642Article in journal (Refereed)
  • 326.
    Ekwall, P
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Holmberg, P
    The properties and structures of aqueous sodium caprylate solutions : II theviscosities of sodium caprylate solutions at 20 C measured with capillaryviscometers1965In: Acta Chemica Scandinavica, ISSN 0904-213X, E-ISSN 1902-3103, Vol. 19, p. 455-468Article in journal (Refereed)
  • 327.
    Ekwall, P
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Holmberg, P
    The properties and structures of aqueous sodium caprylate solutions : III the viscosities at temperatures between 20 and 40 C1965In: Acta Chemica Scandinavica, ISSN 0904-213X, E-ISSN 1902-3103, Vol. 19, p. 573-583Article in journal (Refereed)
  • 328.
    Ekwall, P
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Lemström, K-E
    Eikrem, H
    Holmberg, P
    The properties and structures of aqueous sodium caprylate solutions : IV the vapour pressure of the solutions and the osmotic coefficient of the sodiumcaprylate1967In: Acta Chemica Scandinavica, ISSN 0904-213X, E-ISSN 1902-3103, Vol. 21, p. 1401-1407Article in journal (Refereed)
  • 329.
    Ekwall, P
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Mandell, L
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Properties and structure of the decanolic solutions in the sodium caprylate-decanol-water systems : I. the region of existence of the isotropic decanolic solutions1967In: Acta Chemica Scandinavica, ISSN 0904-213X, E-ISSN 1902-3103, Vol. 21, p. 1612-1618Article in journal (Refereed)
  • 330.
    Ekwall, P
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Mandell, L
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Solutions of alkali soaps and water in fatty acids : I. region of existence of the solutions1969In: Kolloid Zeitschrift & Zeitschrift Polymere, ISSN 0023-2904, Vol. 233, p. 938-944Article in journal (Refereed)
  • 331.
    Ekwall, P
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Mandell, L
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Fontell, K
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    A lamellar mesophase with single amphiphile layers1968In: Acta Chemica Scandinavica, ISSN 0904-213X, E-ISSN 1902-3103, Vol. 22, p. 365-367Article in journal (Refereed)
  • 332.
    Ekwall, P
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Mandell, L
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Fontell, K
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Lyotropic mesophases with 'normal' and 'reversed' twodimensional hexagonal structure1968In: Acta Chemica Scandinavica, ISSN 0904-213X, E-ISSN 1902-3103, Vol. 22, p. 373-375Article in journal (Refereed)
  • 333.
    Ekwall, P
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Mandell, L
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Fontell, K
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Lyotropic mesophases with 'normal' and 'reversed' twodimensional tetragonalstructure1968In: Acta Chemica Scandinavica, ISSN 0904-213X, E-ISSN 1902-3103, Vol. 22, p. 697-699Article in journal (Refereed)
  • 334.
    Ekwall, P
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Mandell, L
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Fontell, K
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Minimum water content of a number of 'reversed' micellar and mesomorphous structures1968In: Acta Chemica Scandinavica, ISSN 0904-213X, E-ISSN 1902-3103, Vol. 22, p. 699-702Article in journal (Refereed)
  • 335.
    Ekwall, P
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Mandell, L
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Fontell, K
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Phase equilibria in the ternary system sodium caprylate-1,8-octane diol-water1969In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 29, p. 542-551Article in journal (Refereed)
  • 336.
    Ekwall, P
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Mandell, L
    Fontell, K
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Some observations on binary and ternary aerosol OT systems1970In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 33, p. 215-235Article in journal (Refereed)
  • 337.
    Ekwall, P
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Mandell, L
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Fontell, K
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Ternary systems of potassium soap, alcohol and water : I. phase equilibria and phase structures1969In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 31, p. 508-529Article in journal (Refereed)
  • 338.
    Ekwall, P
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Mandell, L
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Fontell, K
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Ternary systems of potassium soap, alcohol and water : II. structure and composition of the mesophases1969In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 31, p. 530-539Article in journal (Refereed)
  • 339.
    Ekwall, P
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Mandell, L
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Fontell, K
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Ternary systems of sodium caprylate and water with ethylene glycol, glycerol and tetraethylene glycol1968In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 28, p. 219-226Article in journal (Refereed)
  • 340.
    Ekwall, P
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Mandell, L
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Fontell, K
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    The cetyltrimethylammonium bromide-hexanol-water system1969In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 29, p. 639-646Article in journal (Refereed)
  • 341.
    Ekwall, P
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Mandell, L
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Fontell, K
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Two types of neat soap in ternary systems1968In: Acta Chemica Scandinavica, ISSN 0904-213X, E-ISSN 1902-3103, Vol. 22, p. 1543-1550Article in journal (Refereed)
  • 342.
    Ekwall, P
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Mandell, L
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Solyom, P
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    The aqueous cetyl trimethylammonium bromide solutions1971In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 35, p. 519-528Article in journal (Refereed)
  • 343.
    Ekwall, P
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Mandell, L
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Solyom, P
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    The solution phase with reversed micelles in the cetyl trimethylammonium bromide-hexanol-water system1971In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 35, p. 266-272Article in journal (Refereed)
  • 344.
    Ekwall, P
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Solyom, P
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Properties and structure of the decanolic solutions in the sodium caprylate-decanol-water system : II density and viscosity of the solutions1967In: Acta Chemica Scandinavica, ISSN 0904-213X, E-ISSN 1902-3103, Vol. 21, p. 1619-1629Article in journal (Refereed)
  • 345.
    Ekwall, P
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Solyom, P
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Solutions of alkali soaps and water in fatty acids : II. density and viscosity measurements1969In: Kolloid Zeitschrift & Zeitschrift Polymere, ISSN 0023-2904, Vol. 233, p. 945-955Article in journal (Refereed)
  • 346.
    Ekwall, P
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Stenius, P
    The properties and structures of aqueous sodium caprylate solutions : VII activities of caprylate anions, and counter ion binding to the micelles1967In: Acta Chemica Scandinavica, ISSN 0904-213X, E-ISSN 1902-3103, Vol. 21, p. 1767-1772Article in journal (Refereed)
  • 347. Elftonson, JE
    et al.
    Ström, G
    Holmberg, K
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Olsson, J
    Adhesion of Streptococcus sanguis to porous and non-porous substrates with well-defined surface energies1996In: Journal of Adhesion Science and Technology, ISSN 0169-4243, E-ISSN 1568-5616, Vol. 10, p. 761-770Article in journal (Refereed)
    Abstract [en]

    Adhesion of the oral bacterium Streptococcus sanguis was investigated on two series of surfaces, one solid, non-porous and one porous with a pore diameter centered around 0.2 µm. Each series consisted of four substrates with varying surface free energies: pure aluminum oxide, PEG modified aluminum oxide, and two types of silanized aluminum oxide. The surface composition was analyzed by ESCA and the surface free energy and acid-base character were determined by contact angle measurement using water, formamide and diiodomethane according to Van Oss and Good. Contact angle measurements were conducted on non-porous substrates which had been subjected to the same silanization procedure as the porous ones. Untreated aluminum oxide and PEG modified aluminum oxide were both hydrophilic and gave water contact angles of less than 10°. One silanization procedure gave a surface of intermediate hydrophobicity, with a y-tot of 47.5 mN/m; the other gave a strongly hydrophobic surface of y-tot = 27.4 mN/m. Adhesion of S. sanguis was measured by using radiolabelled bacteria. It was demonstrated that more bacteria adhered to the porous than to the non_x001F_porous substrate and that the PEG treatment, as well as the two sil aniz ation pro cedures, resulted in a decreas e in bacterial adhesion, b oth to the controls treated with aqueous buffer and to surfaces treated with fresh saliva.

  • 348.
    Elofsson, Ulla
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Millqvist-Fureby, A
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Drying of probiotic micro-organisms in aqueous two-phase systems2000In: Minerva biotecnologica (Testo stampato), ISSN 1120-4826, E-ISSN 1827-160X, Vol. 12, p. 279-286Article in journal (Refereed)
    Abstract [en]

    Spray-drying has been investigated as a method for preparation of dry formulations of live bacteria with high viability and high cell density. The concept used in this study has been to disperse the bacteria in an aqueous polymer containing two-phase system (ATPS), compatible with the micro-organisms. The cells partition to one phase, which is separated from the other phase in a droplet dispersion or bi-continuous system. The exclusion of the dispersed phase and the bacteria from the particle surface is studied by ESCA (electron spectroscopy for chemical analysis), which gives an estimate of the molecular composition at the powders surface. A measure of the powder dissolution rate was obtained, this property was highly related to the molecular composition at the powder surface. The effect of additives was studied by adding disaccharides and proteins to the ATPS before drying. The probiotic bacteria Enterococcus faecium M74 and Lactobacillus plantarum have been used as model organisms for this study. The viability after drying and 5 weeks storage has been evaluated by plate counting and was found to be higher in the ATPS compared to when single phase polymer solutions were used as drying matrices. Comparisons were made with freeze-drying of the same systems and also the effect of cell status before the drying step has been evaluated.

  • 349.
    Elofsson, Ulla
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Millqvist-Fureby, Anna
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Stability of spray-dried protein-stabilized emulsions: Effects of different carbohydrate additives2003In: Food Colloids, Biopolymers and Materials / [ed] Eric Dickinson, Ton van Vliet, Royal Society of Chemistry, 2003, p. 265-274Chapter in book (Refereed)
  • 350. Elversson, J
    et al.
    Andersson, K
    Millqvist-Fureby, Anna
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    An atomic force microscopy approach for assessment of particle density applied to single spray-dried carbohydrate particles2007In: Journal of Pharmaceutical Sciences, ISSN 0022-3549, E-ISSN 1520-6017, Vol. 96, no 4, p. 905-912Article in journal (Refereed)
    Abstract [en]

    To evaluate an atomic force microscopy (AFM) approach for effective density analysis of single spray dried carbohydrate particles in order to investigate the internal structure of the particles. In addition, the AFM method was compared to an established technique, that is gas pycnometry. Resonant frequency AFM analysis was employed for determination of the mass of individual particles of spray-dried lactose, mannitol, and a mixture of sucrose/dextran (4:1). The effective particle density was calculated using the diameter of the spherical particles obtained from light microscopy. The apparent particle density was further analyzed with gas pycnometry. It was observed by microscopy that particles appeared either ‘‘solid’’ or ‘‘hollow.’’ A solid appearance applied to an effective particle density close to the true density of the material, whereas a density around 1 g/cm3 corresponded to a hollow appearance. However, carbohydrates, which crystallized during spray drying, for example, mannitol appeared solid but the average effective particle density was 0.95 g/cm3, indicating a continuous but porous structure. AFM measurements of effective particle density corroborate the suggestion of differences in particle structure caused by the varying propensity of carbohydrates to crystallize during spray drying, resulting in mainly either amorphous hollow orcrystalline porous particles.

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