| 1. |
- Aldén, Marcus, et al.
(författare)
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Application of laser-induced fluorescence and CARS for combustion diagnostics
- 1993
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Ingår i: Berichte der Bunsengesellschaft für Physikalische Chemie. - 0005-9021. ; 97:12, s. 1643-1649
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Tidskriftsartikel (refereegranskat)abstract
- Laser diagnostic techniques have during the last decade been successfully applied for diagnostics of combustion processes. The main advantages with these techniques are that they are inherently non-intrusive and that spatially as well as temporally resolved information can be achieved. The current paper will exemplify two different laser spectroscopic techniques. Laser-Induced Fluorescence (LIF), and Coherent anti-Stokes Roman Scattering (CARS), which are currently the most used laser techniques for temperature and species concentration measurements in combustion systems.
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| 2. |
- Andersson-Engels, S., et al.
(författare)
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Tissue diagnostics using laser-induced fluorescence
- 1989
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Ingår i: Berichte der Bunsengesellschaft für Physikalische Chemie. - : Wiley. - 0005-9021. ; 93:3, s. 335-342
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Tidskriftsartikel (refereegranskat)abstract
- We have performed extensive investigations of laser-induced fluorescence in animal and human tissue aimed at instant tissue characterization. Autofluorescence, as well as specific fluorescence from HPD/DHE and other photosensitizers, has been utilized. The studies have been focused on the demarcation of malignant tumours and atheroscleortic plaques. A nitrogen laser or an excimer-pumped dye laser was used to induce fluorescence, which was analysed with an intensified optical multichannel system. A fibre-optic sensor system was developed for the clinical work. Multi-colour fluorescence imaging has also been demonstrated along a line and equipment for two-dimensional imaging is being constructed. Dimensionless spectroscopic functions, which are not affected by factors that are clinically uncontrollable have been employed for optimum tissue discrimination. The investigations have so far been performed in a time-integrated mode, but time-resolved studies are now being initiated to fully exploit the diagnostic power of tissue laser-induced fluorescence. In addition to a presentation of our own work a brief review of tissue fluorescence studies performed by other groups is also given.
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| 3. |
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| 4. |
- Claesson, PM, et al.
(författare)
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Polyelectrolyte-surfactant association at solid surfaces
- 1996
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Ingår i: Berichte Der Bunsen-Gesellschaft. - 0005-9021. ; 100, s. 1008-1013
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Tidskriftsartikel (refereegranskat)abstract
- The interferometric surface force technique has been utilized for studying the inreraction between negatively charged surfaces coated with a cationic polyelectrolyte across solutions of anionic surfactant, sodium dodecyl sulphate (SDS). The polyelectrolyte used was poly ([2-(propionyloxy)ethyl]trimethylammonium chloride), PCMA, which has one positive charge per segment. At low ionic strength the polyelectrolyte adsorbs in a flat conformation and neutralizes the negative mica surface charge. The interaction forces between the polyelectrolytecoared surfaces are dominated by a strongly attractive force at distances shorter than about 150 Å. Addition of SDS into the measuring chamber to a concentration of about 0.1 cmc changes the interaction forces dramatically. The long-range forces are now repulsive due to a recharging of the surfaces. The polyelectrolyte layer also sweüs considerably and, more surprisingly, the force versus distance profile displays clear oscillations. We interpret these oscillations as being caused by the spatial arrangement of SDS micelles stabilized by the polyelectrolyte. The oscillations in the force curve remain as the SDS concentration is increased to cmc. The interaction forces and the layer structure for the PCMA/SDS system are very different compared to those observed for weakly charged polyelectrolyte/SDS and Iysozyme/SDS systems. The differences can be rationalized by considering that los charge density polyelectrolytes and Iysozyme, a compact cationic globular protein, cannot equally efficiently stabilize SDS micelles as a flexible high charge density cationic polyelectrolyte such as PCMA .
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| 5. |
- Dahlgren, MAG, et al.
(författare)
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Polyelectrolytes interacting with interfaces: Surface forces and theoretical results
- 1996
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Ingår i: Berichte Der Bunsen-Gesellschaft. - 0005-9021. ; 100, s. 1004-1007
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Tidskriftsartikel (refereegranskat)abstract
- The order in which salt and polyelectrolyte is added to a solution influences the structure of the adsorbed polyelectrolyte on surfaces in contact with the solution, and the interactions between surfaces across such solutions. These effects were investigated using the interferometric surface force technique. The results show that in low ionic strength (0.1mM KBr), there is a strong attraction between two mica surfaces covered with oppositely charged polyelectrolytes. When the ionic strength is increased (up to 100 mM KBr), a long-ranged repulsion is developing. This repulsion is more long ranged and larger in magnitude when the salt is added before the polyelectrolyte than when salt is added to a system which already contains polyelectrolyte. This indicates a more extended adsorbed layer when the adsorption is carried out directly from the higher ionic strength solution. This more extended adsorbed layer is irreversibly compressed upon the first approach of the surfaces. Mean field calculations (Scheutjens-Fleer model) were used to rationalize experimental findings. The results from these calculations show that the adsorbed layer is much more extended in high ionic strength solutions, which is in good agreement with the experimental results.
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| 6. |
- Forsman, Hans, et al.
(författare)
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Effects of temperature and pressure on the thermal conductivity of solid n‐undecane
- 1983
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Ingår i: Berichte Der Bunsen-Gesellschaft. - : John Wiley & Sons. - 0005-9021. ; 87:6, s. 490-495
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Tidskriftsartikel (refereegranskat)abstract
- We have measured the thermal conductivity, λ, of n-undecane, using the transient hot-wire technique. At low pressure, n-undecane has a plastic crystal phase αH. The increase in λ, going from the liquid to phase αH, was 35%. For a liquid → plastic crystal transition, this is a high value. It reflects that orientational disorder is mainly limited to rotation of the rod-shaped molecule around its chain axis. The low temperature phase βo, was shown to exhibit a weak temperature dependence of λ at isochoric conditions. This suggests the presence of structural disorder, probably caused by reorientation of the chain-end methyl groups. The volume dependence of λ in phase βo, g = - (∂ lnλ/∂ ln V)T, was found to be about 9.5. This result is discussed in terms of the anharmonicity of the weak interchain van der Waals bonds. Some heat capacity results were also obtained.
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| 7. |
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| 8. |
- Nordholm, Strure, et al.
(författare)
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Progress on the modeling of the collisional energy transfer mechanism in unimolecular reactions
- 1997
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Ingår i: Berichte Der Bunsen-Gesellschaft. - 0005-9021. ; 101, s. 574-580
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Tidskriftsartikel (refereegranskat)abstract
- The RRKM theory of unimolecular reaction rates is a statistical mechanical theory based on an assumption of microcanonical equilibrium in the reactant phase space. The energy transfer in reactant medium collisions was originally described by a canonical strong collision assumption, i.e., an assumption of full thermal equilibration in each collision. In our work we first introduce a microcanonical strong collision assumption which gives the RRKM theory a consistent form. We then introduce parametrizations of the degree of weakness (nonergodicity) of the collisions. A concept of collision efficiency is defined. The weakness of the collision is expressed in terms of reduced subsets of active reactant and medium degrees of freedom. The corresponding partially ergodic collision theory (PECT) yields physical functional forms of the collisional energy transfer kernel P(E,E). In order to resolve the energy and temperature dependence and the dependence on interaction strength a multiple encounter theory is introduced (PEMET). Initially each encounter may be described by a semiempirical PECT model. Eventually the encounters may be resolved by quantum dynamical calculations of the semiclassical or CAQE (classical approach quantum encounter) type. Simple statistical collision models only distinguish between hits and misses . In reality the energy transfer efficiency exhibits characteristic fall off with increasing impact parameter b. This b-dependence can be explicitly accounted for in the master equation for the reaction rate coefficient.
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