| 1. |
- Adloff, C, et al.
(författare)
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Energy flow and rapidity gaps between jets in photoproduction at HERA
- 2002
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 24:4, s. 517-527
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Tidskriftsartikel (refereegranskat)abstract
- Dijet events in photon-proton collisions in which there is a large pseudorapidity separation, Deltaeta > 2.5 between the two highest E-T jets are studied with the H1 detector at HERA. The inclusive dijet cross sections are measured as functions of the longitudinal momentum fractions of the proton and photon which participate in the production of the jets, x(p)(jets) and x(gamma)(jets) respectively, Deltaeta, the pseudorapidity P separation between the two highest E-T jets, and E-T(gap), the total summed transverse energy between the jets. Rapidity gap events are defined as events in which E-T(gap) is less than E-T(cut), for E-T(cut) varied between jets 0.5 and 2.0 GeV. The fraction of dijet events with a rapidity gap is measured differentially in Deltaeta, x(p)(jets) and x(gamma)(jets). An excess of events with rapidity gaps at low values of E-T(cut) is observed above the expectation from standard photoproduction processes. This excess can be explained by the exchange of a strongly interacting colour singlet object between the jets.
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| 2. |
- Bergström, Lars Magnus, et al.
(författare)
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A model-independent evaluation of experimental data, and comparison with theory, of synergistic effects in mixtures of an ionic and a nonionic surfactant
- 2003
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 19:26, s. 10719-10725
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Tidskriftsartikel (refereegranskat)abstract
- Critical micelle concentrations for mixtures of an anionic (sodium dodecyl sulfate) and a nonionic (decyl beta-glucoside) surfactant was obtained from surface tension measurements at different concentrations of added NaCl. The observed synergistic effects were analyzed by means of introducing a novel model-independent synergy parameter. The model-independent evaluation has enabled the comparison of experimental results with a theoretical model based on the Poisson-Boltzmann (PB) mean field theory for spherical, cylindrical, and planar geometries, respectively. We found that best agreement with experimental data was obtained for largely curved structures (spherical and cylindrical micelles) at all [NaCl], which is consistent with the fact that rather small micelles, as a rule, form at the critical micelle concentration. Moreover, the PB theory was found to better describe synergistic behavior of the experimental data than the more conventional regular mixture theory, in particular at low electrolyte concentrations. The magnitude of the observed synergistic effects was found to increase as a small amount of NaCl was added and reach a maximum at [NaCl] = 10 mM, in agreement with the PB theory. As expected, synergism was observed to decrease in magnitude upon further addition of NaCl.
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| 3. |
- Persson, C. M., et al.
(författare)
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Testing the Gouy-Chapman theory by means of surface tension measurements for SDS-NaCl-H2O mixtures
- 2003
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 267:1, s. 151-154
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Tidskriftsartikel (refereegranskat)abstract
- Surface tension isotherms were measured for sodium dodecyl sulfate (SDS) at different concentrations of added salt (NaCl). The free energy of the surfactant monolayer was assessed by invoking the Gouy-Chapman theory for the charged head groups, the hydrophobic (Tanford) free energy of transfer of the hydrocarbon chain, and the hydrocarbon chain configurational free energy according to Gruen's calculations and finally macroscopic contact terms. In particular, the effect of an increased salt concentration in bulk was examined. Theoretical predictions compare well with the experimental findings, and good agreement was found with respect to both the variation of free energy of the monolayer and the surface pressure behavior. Thus, at least for a liquid-expanded monolayer of SDS, the Gouy-Chapman model yields a satisfactory account of the electrostatic contribution to the thermodynamic properties at different salt concentrations of NaCl.
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