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- Johansson, Jonas, et al.
(författare)
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Time-Resolved Studies of Light Propagation in Crassula and Phaseolus Leaves
- 1999
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Ingår i: Photochemistry and Photobiology. - 0031-8655. ; 69:2, s. 242-247
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Tidskriftsartikel (refereegranskat)abstract
- Time-resolved transmittance was used to extract in vivo optical properties of leaves of green plants experimentally. In time-resolved transmittance measurements an ultrashort light pulse is directed onto the surface of the object and the transmitted light is measured with a time resolution in the range of picoseconds. A table-top terawatt laser was used to generate 200 fs light pulses at 790 nm with a repetition rate of 10 Hz. The light pulses were focused through a cuvette filled with water to produce white light pulses and optical filters were placed in the beam path to select the wavelength of the light focused onto the leaf surface. The time profiles of the light transmitted through the leaves was recorded with a streak camera having a time resolution of about 2.5 ps. Results from Crassula falcata and Phaseolus vulgaris studied at 550, 670 and 740 nm are reported. The three selected wavelength regions represent medium, high and a low absorption of light, respectively. A library of curves was generated using Monte Carlo simulation, and the absorption and scattering coefficients were extracted by comparison of experimental curves with this library. Our results suggest that in the case of the thin (200 μm) Phaseolus leaves and certainly in the case of the thick (4 mm) Crassula leaves, light scattering plays an important role in light transport through the leaf and should also affect light flux in these leaves.
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| 2. |
- Johansson, Mikael, et al.
(författare)
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Tumor blood flow and the cytotoxic effects of estramustine and its constituents in a rat glioma model
- 1997
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Ingår i: Neurosurgery. - : Oxford University Press. - 0148-396X .- 1524-4040. ; 41:1, s. 237-244
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: Estramustine (EaM) is a conjugate of nor-nitrogen mustard (NNM) and 17 beta-estradiol (E2) that has cytotoxic and radiosensitizing effects on experimental malignant glioma. Its mechanism of action is only partly understood. To further investigate the mechanism in vivo, the effects on tumor blood flow (TBF) and tumor growth were analyzed.METHODS: TBF was measured by radioactive microspheres, and tumor growth was measured by weight. Apoptosis was evaluated by in situ end labeling and gel electrophoresis. The effects of the constituents NNM and E2 were also evaluated.RESULTS: EaM increased TBF to 153.8 ml/100 g/min after 3 days and to 153.9 ml/100 g/min after 10 days of treatment, compared with 94.0 ml/100 g/min in untreated controls. Cerebral blood flow did not change after EaM treatment. NNM increased TBF but also showed a tendency to increase cerebral blood flow. E2 increased TBF, whereas cerebral blood flow was unchanged. EaM resulted in a rapid reduction in tumor weight from 230 mg in untreated animals to 146 mg after 3 days of treatment. EaM induced an early transient fragmentation of deoxyribonucleic acid in glioma but not in the normal brain. Neither NNM nor E2 affected tumor weight.CONCLUSION: EaM increases TBF in the BT4C rat glioma model with a concomitant rapid antitumoral effect. The increase in TBF could partially be induced by an estrogen-like action of EaM, but the rapid cytotoxic effect of the drug is obviously attributed to the intact EaM compound. This cytotoxic effect might be attributable to the induction of programmed cell death.
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| 5. |
- Nilsson, Ulf, et al.
(författare)
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Synthesis, conformational analysis and comparative protein binding of a galabioside and its thioglycoside analogues
- 1996
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 2:3, s. 295-302
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Tidskriftsartikel (refereegranskat)abstract
- The two thio analogues (2 and 3) of TMSEt galabioside [2-(trimethylsilyl) ethyl 4-O-(α-D-galactopyranosyl)-β-D-galactopyranoside, 1], having anomeric sulfur instead of anomeric oxygen atoms, were synthesized and their conformations investigated by NMR and computational (MM3) methods. A spacer galabioside was covalently coupled to aminated microtiter plates, and binding of a bacterial pilus adhesin (PapG) to the plates was inhibited by the soluble ligands 1, 2 and 3. The ligand 2, which has an intersaccharidic sulfur linkage, was a much less efficient inhibitor than 1, which has the natural oxygen linkage. The inhibitory power of ligand 3 was only slightly less than that of 1. An NMR experiment with 1 and 2, in which hydroxyl-group hydrogens had been partially (50%) substituted by deuterium, demonstrated the presence (in 1) and absence (in 2) of an intramolecular (HO2′-HO6) hydrogen bond. This result indicates that the conformations of 1 and 2 are different and that the difference is sufficient to cause the observed (≈30 times) reduction of the saccharide-protein binding strength.
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| 6. |
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| 7. |
- Törngren, Martin, 1963-, et al.
(författare)
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A mechatronics test-bed for embedded distributed real-time control systems
- 1997
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Ingår i: Proceedings of IFAC workshop on Algorithms and Architectures in real-time control systems.
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Konferensbidrag (refereegranskat)abstract
- A testbed has been developed to be used for research in distributed real-time control systems.The testbed is modular both in mechanics and in control system, allowing a number of robot configurations,control system structures and execution strategies to be implemented and evaluated. The nodes of thecontrol system are currently based on a microprocessor, CAN communication, interfaces to analog anddigital I/O, and motor drive units. The modularity of the nodes allows changes of I/O and communicationsystem, as well as the implementation of different resource structures. To give an idea of the experimentalcapabilities of the testbed, initial experiments in the area of time-varying control systems are described.The research goals include design and experimental evaluation of execution strategies, time-varying controlsystems and development tools for real-time implementation support.
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| 8. |
- Åklint, Thorbjörn, et al.
(författare)
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Magnetic Properties of deposited iron clusters produced in a high yield laser vaporization source
- 1998
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Ingår i: Applied Organometallic Chemistry. ; 12, s. 479-
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Tidskriftsartikel (refereegranskat)abstract
- Clusters of iron produced in a laser vaporization source have been characterized with time-of-flight spectra and deposited on different substrates for production of films of varying thickness. The magnetic properties of these films with thicknesses of 60 and 120 nm were investigated using an alternating gradient magnetometer. The films exhibit mono-domain behavior from a broad size distribution which has been confirmed by transmission electron microscopy. Films were also investigated by Mössbauer spectroscopy, which showed fast relaxation in the particles at room temperature.
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