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Sökning: WFRF:(Olsson Bengt) > (2000-2004) > (2001) > Naturvetenskap

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1.
  • van Aarle, Ingrid, et al. (författare)
  • Microscopic detection of phosphatase activity of saprophytic and arbuscular mycorrhizal fungi using a fluorogenic substrate
  • 2001
  • Ingår i: Mycologia. - 0027-5514. ; 93:1, s. 17-24
  • Tidskriftsartikel (refereegranskat)abstract
    • The location and activity of saprophytic and arbuscular mycorrhizal (NM) fungal phosphatases have been investigated with a fluorogenic substrate (ELF) that forms a fluorescent crystalline precipitate at the site of phosphatase activity. This ELF substrate method was compared with other detection methods such as fast blue RR salt staining and p-nitrophenyl phosphate. The ELF substrate was successfully used to determine the location of phosphatase activity in AM fungal hyphae, and to visualize the active AM fungal colonization of roots. The substrate was taken up by fungal hyphae, when acid and alkaline buffers were used, and internal phosphatase activity was visualized. The release of both acid and alkaline phosphatases by a saprophytic fungus to an agar medium was demonstrated. ELF combined with an alkaline buffer led to specific staining of active fungal structures such as hyphae, arbuscules and young vesicles in AM-colonized roots. The results indicate that the ELF substrate is a sensitive indicator for fungal phosphatase activity and that it can be used to visualize hyphal phosphatase activity in both roots and external hyphae.
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2.
  • Lif, Magnus, et al. (författare)
  • Workspaces enhance efficiency – theories, concepts and a case study
  • 2001
  • Ingår i: Information Technology and People. - : MCB UP Ltd. - 0959-3845 .- 1758-5813. ; 14:3, s. 261-272
  • Tidskriftsartikel (refereegranskat)abstract
    • Traditional process-oriented system development methods often result in fragmentary user interfaces with information presented in various windows without considerations of requirements for simultaneous viewing. Opening, closing, moving and resizing these windows attracts the users’ attention away from the actual work. User interface design according to the workspace metaphor could provide skilled professional users with an efficient, customised user interface to administrative information systems. This can improve work performance and facilitate efficient navigation between workspaces. A case study in co-operation with the Swedish National Tax Board (RSV) describes practical use of the workspace metaphor.
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3.
  • Evilevitch, Alex, et al. (författare)
  • Kinetics of oil solubilization in microemulsion droplets. Mechanism of oil transport.
  • 2001
  • Ingår i: Electroanalysis. - : American Chemical Society (ACS). - 1040-0397. ; 16:23, s. 8755-8762
  • Tidskriftsartikel (refereegranskat)abstract
    • We have studied the kinetics of the solubilization of oil through a temperature jump into a droplet microemulsion phase in the system water-pentaethylene oxide dodecyl ether-decane at 25 C. The initial state is formed by subjecting the equilibrium system at 25 C to a temperature quench to 22, 20, and 14 C, respectively. At this lower temperature, which at equilibrium corresponds to a two-phase system, oil droplets form and grow in size with increasing time. By varying the time between the quench and the T-jump, the size of the initial oil drops is varied in a systematic and known way in the relaxation study. The relaxation process is monitored by following the turbidity of the system. We find that for all the systems the relaxation back to equlibrium is much faster than the drop growth process observed after the temperature quench. This general observation is explained by realizing that the redissolution of the oil drops is analogous to the oil transfer phase, which in the quench experiment occurs prior to the Ostwald ripening phase. More significant is that we observed a qualitative transition in the relaxation behavior when the initial aggregate distribution is varied. In all cases we have the same initial temperature and overall composition and one population of many small droplets and fewer larger drops. The size of the larger drops only affects the relaxation in a quantitative way. If the small droplets are only slightly smaller than the equilibrium size, equilibration occurs through the diffusion of oil molecules in the bulk phase. When the initial droplets are sufficiently small, a new kinetic route is available where there is an efficient direct oil transfer between the small droplets and large drops. This allows for a fast relaxation of the oil distribution between the two populations of drops.
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4.
  • Evilevitch, Alex, et al. (författare)
  • Molecular transport in a nonequilibrium droplet microemulsion system.
  • 2001
  • Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 17:22, s. 6893-6904
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, we consider the problem of oil molecular transport between nonequilibrium microemulsion oil droplets in water. In particular, we have investigated the kinetics of solubilization of big oil drops by smaller microemulsion droplets transforming a bimodal size distribution into an equilibrium microemulsion with a unimodal size distribution. The process involves the diffusion of oil monomers across the aqueous solvent. Solubilization experiments are presented on a well-characterized nonionic microemulsion system, where interfacial area and dispersed volume are conserved and where the excess oil chemical potential is dominated by interfacial curvature energy. An analysis of the experiments shows that the solubilization kinetics depend significantly on the concentrations and sizes of big and small droplets. We formulate a quantitative model for the solubilization kinetics where the effects of size and concentrations are treated within the framework of a cell model. A quantitative agreement between model and experiment is obtained, and the analysis also shows that the majority of oil monomers are captured by small droplets already in the vicinity of the big drop surface when the concentration of small droplets is high.
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  • Resultat 1-4 av 4

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