| 1. |
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| 2. |
- Malmstrom, E, et al.
(författare)
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Dendritic polymers for photonic applications.
- 2002
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Ingår i: Abstracts of Papers of the American Chemical Society. - 0065-7727. ; 224, s. 384-POLY-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 3. |
- Persson, L., et al.
(författare)
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Separation of mass-overlapped time of flight-energy elastic recoil detection analysis data using Ryan and Jamieson's dynamic analysis method
- 2001
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - 0168-583X .- 1872-9584. ; 179:3, s. 403-411
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Tidskriftsartikel (refereegranskat)abstract
- Time of flight-energy (ToF-E) elastic recoil detection analysis (ERDA) data often contains mass signals with considerable overlap from adjacent isotopes in the mass-energy plane. An evaluation has been carried out of the suitability of the dynamic analysis method proposed by Ryan and Jamieson to decompose elemental signals with overlapping mass. This method is shown to work very well on generated test data and the result when it was applied to experimental data appears quite promising. Very accurate mass calibration and lineshape determination was found to be a prerequisite for the application of the method.
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| 4. |
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| 5. |
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| 6. |
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| 7. |
- Rotticci-Mulder, J. C., et al.
(författare)
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Expression in Pichia pastoris of Candida antarctica lipase B and lipase B fused to a cellulose-binding domain
- 2001
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Ingår i: Protein Expression and Purification. - : Elsevier BV. - 1046-5928 .- 1096-0279. ; 21:3, s. 386-392
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Tidskriftsartikel (refereegranskat)abstract
- Candida antarctica lipase B (CALB) and C. antarctica lipase B fused to a cellulose-binding domain (CBD-CALB) were expressed functionally in the methylotrophic yeast Pichia pastoris. The cellulose-binding domain originates from cellulase A of the anaerobic rumen fungus Neocallimastix patriciarum. The genes were fused to the a-factor secretion signal sequence of Saccharomyces cerevisiae and placed under the control of the alcohol oxidase gene (AOX1) promoter. The recombinant proteins were secreted into the culture medium reaching levels of approximately 25 mg/L. The proteins were purified using hydrophobic interaction chromatography and gel filtration with an overall yield of 69%. Results from endoglycosidase H digestion of the proteins showed that CALB and CBD-CALB were N-glycosylated. The specific hydrolytic activities of recombinant CALB and CBD-CALB were identical to that reported for CALB isolated from its native source. The fusion of the CBD to the lipase resulted in a greatly enhanced binding toward cellulose for CBD-CALB compared with that for CALB.
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| 8. |
- Busson, P., et al.
(författare)
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Preparation of mesogen-functionalized dendrimers for second-order nonlinear optics
- 2002
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Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 35:5, s. 1663-1671
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Tidskriftsartikel (refereegranskat)abstract
- Liquid crystalline dendrimers with peripheral mesogen-containing units have been prepared. Multistep synthesis with several selective reactions was used in the preparation of the mesogen-containing molecules, 4-[10-(hydroxycarbonyl)decyloxy]phenyl 4-[4'-(2-(R)-octyloxy)-3'-nitrophenyl]benzo ate and 4-[10-(hydroxycarbonyl)decyloxy]biphenyl 4-[4'-(2-(R)-octyloxy)-3'-nitrophenyl]benzoate. Both molecules possessed an electron-accepting nitro group placed perpendicular to the long axis of the molecules in order to enhance the nonlinear optical activity. A second generation hydroxyl functional aliphatic dendrimer based on the dihydroxy acid, 2,2-bis(hydroxymethyl)propionic acid, was used as dendritic scaffold and was subsequently functionalized with the aforementioned groups. The purity and structure of the two liquid crystalline dendrimers were determined by H-1 NMR spectroscopy, size exclusion chromatography, and elemental analysis. The synthesis of both the mesogen-containing units and the liquid crystalline dendrimers is described in detail. Investigation of the liquid crystalline properties of the materials by differential scanning calorimetry and optical microscopy showed that they exhibited different mesophases, including the chiral smectic C phase. Ferroelectric switching was observed in this tilted phase, and electrooptical properties, including tilt angle and spontaneous polarization measurements, were investigated. Finally, the nonlinear optical properties of one of the materials were preliminary characterized.
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| 9. |
- Claesson, Hans, et al.
(författare)
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Rheological behaviour during UV-curing of a star-branched polyester
- 2002
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Ingår i: Progress in organic coatings. - 0300-9440 .- 1873-331X. ; 44:1, s. 63-67
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Tidskriftsartikel (refereegranskat)abstract
- Using a rheometer coupled with an UV-light generator, the viscoelastic behaviour during the fast cure of star-branched polyester is investigated. The 32 arm star polymers consist of a hyperbranched polyester core, Boltorn(TM) and linear grafts of poly(E-caprolactone) (degree of polymerisation: 20-52) with methacrylate end groups. The resins are crystalline and the melting points range from 34 to 50degreesC; films can be formed and cured below 80degreesC. The crossover of G' and G was used as the gel point. The time to reach the gel point, a few seconds, increases linearly with molecular weight.
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| 10. |
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| 11. |
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| 12. |
- Gustavsson, M., et al.
(författare)
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Stable linker peptides for a cellulose-binding domain-lipase fusion protein expressed in Pichia pastoris
- 2001
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Ingår i: Protein Engineering. - : Oxford University Press (OUP). - 0269-2139 .- 1460-213X. ; 14:9, s. 711-715
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Tidskriftsartikel (refereegranskat)abstract
- Fusion proteins composed of a cellulose-binding domain from Neocallimastix patriciarum cellulase A and Candida antarctica lipase B were constructed using different linker peptides. The aim was to create proteolytically stable linkers that were able to join the functional modules without disrupting their function. Six fusion variants containing linkers of 4-44 residues were expressed in Pichia pastoris and analysed. Three variants were found to be stable throughout 7-day cultivations. The cellulose-binding capacities of fusion proteins containing short linkers were slightly lower compared with those containing long linkers. The lipase-specific activities of all variants, in solution or immobilized on to cellulose, were equal to that of the wildtype lipase.
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| 13. |
- Hardalupas, Y, et al.
(författare)
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Chemiluminescence sensor for local equivalence ratio of reacting mixtures of fuel and air (FLAMESEEK)
- 2004
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Ingår i: Applied Thermal Engineering. - : Elsevier BV. - 1359-4311. ; 24:11-12, s. 1619-1632
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes a Cassegrain optics-based chemiluminescence sensor (CS) for measurements in gas turbine combustors. The chemiluminescence sensor measures the equivalence ratio of reacting fuel and air mixtures, and can identify the flame location, in partially premixed flames. It has the potential for monitoring the degree of premixedness of reacting fuel and air in industrial gas turbine combustors, where operation with lean premixed mixtures is important for reduction of NO, emissions. The spatial resolution of the sensor is evaluated by comparing OH* chemiluminescence measurement from the CS with laser induced OH fluorescence, in the cone-shaped premixed flame of a Bunsen burner. The ability of the sensor to measure in a modified micro-gas turbine environment burning a methane/air, as well as, a methane/ water/air flame (humidified flame) is also demonstrated.
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| 14. |
- Hedenqvist, Mikael S., et al.
(författare)
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Transport properties of hyperbranched and dendrimer-like star polymers
- 2000
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Ingår i: Polymer. - 0032-3861 .- 1873-2291. ; 41:5, s. 1827-1840
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Tidskriftsartikel (refereegranskat)abstract
- Moisture transport properties were assessed by sorption and desorption measurements on hydroxyl-functional hyperbranched polyesters based on 2,2-bis(methylol) propionic acid (bis-MPA) as AB(2)-monomer with ethoxylated pentaerythritol. A series of these polymers with different molar masses were studied. For the first time, it is reported that sigmoidal sorption curves were successfully modelled using a time-dependent surface boundary concentration, where the relaxation time was obtained from the mechanical stress relaxation data. The zero concentration diffusivities were very small and comparable with the values of fully amorphous poly(vinyl alcohol). Both the diffusivity data and the stress relaxation data indicated that these materials were plasticized by moisture. Ethylene glycol transport properties were measured on a hexadecanoate(C16)-terminated bis-MPA hyperbranched polymer. The replacement of the hydroxyl groups with C16 paraffin tails resulted in an increase in solute diffusivity despite the fact that these polymers became semicrystalline. The shape of the desorption curves indicated that continuous micropores were present and facilitated mass transport. The moisture transport properties were also measured on a series of semicrystalline dendrimer-like star poly(epsilon-caprolactone(s)). The low measured densities of these highly crystalline dendrimers confirmed that the porosity, as indicated by the shape of the desorption curves, had to be discontinuous. The porosity in the (C16)-terminated and the poly(epsilon-caprolactone(s)) was impossible to eliminate by applying a high external pressure during crystallization. A collective view of all the results obtained confirm that the transport properties are primarily controlled by the hydroxyl group concentration.
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| 15. |
- Hedin, Eva . M. K., et al.
(författare)
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Interfacial orientation of Thermomyces lanuginosa lipase on phospholipid vesicles investigated by electron spin resonance relaxation spectroscopy
- 2002
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Ingår i: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 41:48, s. 14185-14196
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Tidskriftsartikel (refereegranskat)abstract
- The binding orientation of the interfacially activated Thermomyces lanuginosa lipase (TLL, EC 3.1.1.3) on phospholipid vesicles was investigated using site-directed spin labeling and electron spin resonance (ESR) relaxation spectroscopy. Eleven TLL single-cysteine mutants, each with the mutation positioned at the surface of the enzyme, were selectively spin labeled with the nitroxide reagent (1-oxyl-2,2,5,5-tetramethyl-Delta(3)-pyrroline-3-methyl) methanethiosulfonate. These were studied together with small unilamellar vesicles (SUV) consisting of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylglycerol (POPG), to which TLL has previously been shown to bind in a catalytically active form [Cajal, Y., et al. (2000) Biochemistry, 39, 413-423]. The orientation of TLL with respect to the lipid membrane was investigated using, a water-soluble spin relaxation agent. chromium(III) oxalate (Crox), and a recently developed ESR relaxation technique [Lin, Y., et al. (1998) Science 279, 1925-1929], here modified to low microwave amplitude (< 0.36 G). The exposure to Crox for the spin label at the different positions on the surface of TLL was determined in the absence and presence of vesicles. The spin label at positions Gly61-Cys and Thr267-Cys, closest to the active site nucleophile Ser146 of the positions analyzed, displayed the lowest exposure factors to the membrane-impermeable spin relaxant, indicating the proximity to the vesicle surface. As an independent technique, fluorescence spectroscopy was employed to measure fluorescence quenching of dansyl-labeled POPG vesicles as exerted by the protein-bound spin labels. The resulting Stern-Volmer quenching constants showed excellent agreement with the ESR exposure factors. An interfacial orientation of TLL is proposed on the basis of the obtained results.
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| 16. |
- Hedin, Eva M. K., et al.
(författare)
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Low microwave-amplitude ESR spectroscopy : Measuring spin-relaxation interactions of moderately immobilized spin labels in proteins
- 2004
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Ingår i: Journal of Biochemical and Biophysical Methods. - : Elsevier BV. - 0165-022X .- 1872-857X. ; 60:2, s. 117-138
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Tidskriftsartikel (refereegranskat)abstract
- Electron spin resonance (ESR) spectroscopy in combination with site-directed spin labeling (SDSL) is a powerful tool for determining protein structure, dynamics and interactions. We report here a method for determining interactions between spin labels and paramagnetic relaxation agents, which is performed under subsaturating conditions. The low microwave-field amplitude employed (h(1) < 0.36 G) only requires standard, commercially available ESR equipment. The effect of relaxation enhancement on the spin-spin-relaxation time, T-2e, is measured by this method, and compared to classical progressive power saturation performed on a free spin label, (1-oxyl-2,2,5,5-tetramethyl-Delta(3)-pyrroline-3-methyl)methanethiosulfonate (MTSL), and a spin-labeled protein (Thermomyces lanuginosa lipase, TLL-1252C), employing the water-soluble relaxation agent chromium(III) oxalate (Crox) in concentrations between 0-10 mM. The low-amplitude theory showed excellent agreement with that of classical power saturation in quantifying Crox-induced relaxation enhancement. Low-amplitude measurements were then performed using a standard resonator, with Crox, on 11 spin-labeled TLL mutants displaying rotational correlation times in the motional narrowing regime. All spin-labeled proteins exhibited significant changes in T-2e. We postulate that this novel method is especially suitable for studying moderately immobilized spin labels, such as those positioned at exposed sites in a protein. This method should prove useful for research groups with access to any ESR instrumentation.
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| 17. |
- Hedin, Eva. M. K., et al.
(författare)
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Selective reduction and chemical modification of oxidized lipase cysteine mutants
- 2002
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Ingår i: Canadian journal of chemistry (Print). - : Canadian Science Publishing. - 0008-4042 .- 1480-3291. ; 80:6, s. 529-539
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Tidskriftsartikel (refereegranskat)abstract
- Thirteen single-cysteine mutants of the 33 kDa fungal triacylglycerol lipase Thermomyces (formerly Humicola) lanuginosa lipase (TLL, EC 3.1.1.3) Were produced and characterized for the purpose of site-directed chemical modification with spectroscopic reporter groups. All cysteine mutants were found to be predominantly blocked by oxidation to disulfides with endogenous cysteine during production. The fraction of lipase molecules with free sulfhydryl groups was analyzed by labeling with N-biotinylaminoethyl methanethiosulfonate, followed by a novel dot-blot method based on biotin-streptavidin interactions. A non-invasive method for the reduction of the introduced cysteine was elaborated for this protein containing three native disulfide bridges. The site-specifically reduced TLL mutants were then labeled with the sulfhydryl-specific reagents 2-(5-dimethylaminonaphth-1-ylsulfonamido)ethyl methanethiosulfonate or (1-oxyl-2,2,5,5-tetramethyl-Delta(3)-pyrroline-3-methyl) methanethiosulfonate, and studied by fluorescence and electron spin resonance (ESR) spectroscopy.
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| 18. |
- Hermann, D. S., et al.
(författare)
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Novel passive polymer waveguides integrated with electro-optically active ferroelectric liquid crystals
- 2001
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Ingår i: Optical Engineering. - : SPIE-Intl Soc Optical Eng. - 0091-3286 .- 1560-2303. ; 40:10, s. 2188-2198
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Tidskriftsartikel (refereegranskat)abstract
- We report the preparation and characterization of novel isotropic polymer slab waveguides made by photochemical crosslinking, and their integration with a ferroelectric liquid crystal in an integrated electro-optic modulator. The refractive index of the passive copolymer material in the device was controlled by the copolymer composition, and good agreement between measured and calculated effective indices for the guided modes of polymer films was obtained. The active ferroelectric liquid crystal exhibited a refractive index change of Deltan approximate to0.10 upon application of an ac voltage of +/- 30 V, giving an electro-optic modulation of the input TE0-mode with a contrast ratio of 11:1 and only a small polarization conversion into TM output light.
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| 19. |
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| 20. |
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| 21. |
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| 22. |
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| 23. |
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| 24. |
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| 25. |
- Ortegren, J., et al.
(författare)
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Dielectric relaxation of liquid crystalline dendrimers and liquid crystalline polymers with pendant nitro groups
- 2001
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Ingår i: Polymer. - 0032-3861 .- 1873-2291. ; 42:25, s. 10027-10033
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Tidskriftsartikel (refereegranskat)abstract
- The dielectric relaxation was determined in a time-domain spectrometer between 100 and 295 K and from 0.1 to 1000 Hz for series of dendritic liquid crystalline polymers with scaffolds based on 2,2-bis(hydroxymethyl)propionic acid (bis-MPA) of generations 0-3 with 4-((R)-1-methylheptyloxy)phenyl 4-{4'-[10-(hydroxy-carbonyl)decyloxy]-phenyl} benzoate as mesogen and for the second generation of dendrimers with 4-[10-(hydroxycarbonyl)decyloxy]-biphenyl 4-[4'-(2-(R)-octyloxy)-3-nitrophenyl] benzoate as mesogen. Dielectric data are also reported for a side-chain liquid crystalline polymer based on {4''-[(R)-(-)-2-octyloxyl-3-nitro-phenyl 4-(4'-(11-acryloyl-oxyundecyloxy)phenyl}benzoate. The low temperature subglass process (gamma) assigned to the spacer group was essentially insensitive to molecular architecture and to the presence of a pendant nitro group in the mesogen. The high temperature sub-glass process (beta) assigned to a 180 degrees flip of part of mesogen was only moderately sensitive to the molecular architecture. The introduction of a pendant nitro group in the mesogen led to a substantial increase in both activation energy and relaxation strength. The results suggest that the phenylene ring with the pendant nitro group participates in the beta process.
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| 26. |
- Pitois, C., et al.
(författare)
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Characterization of fluorinated hyperbranched polymers and dendrimers for waveguide applications
- 2002
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Ingår i: Proceedings of SPIE, the International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 4805, s. 27-34
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We report on optical transmission properties and results of optical waveguide characterization of flourinated hyperbranched polymers and dendrimers (details on chemical synthesis were reported recently [1]). The polymers and dendrimers allow the introduction of additional functionality, such as cross-linking and refractive index tuneability. The dendrimers having a similar bulk structure as the hyperbranched polymer were also shown to house lanthanide cations for optical amplifying application. The fluorinated bulk structure results in a low contribution from vibration overtones in the absorption spectra in the NIR/IR region (800 - 2200 nm). The refractive index of the fundamental fluorinated hyperbranched polymer was found to be tuneable between ca 1.45 and 1.65 by incorporating various substituents. Optical losses were measured to be below ca 0.5 dB/cm at 1550 nm.
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| 27. |
- Pitois, Claire, et al.
(författare)
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Fluorinated dendritic polymers and dendrimers for waveguide applications
- 2003
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Ingår i: Optical materials (Amsterdam). - 0925-3467 .- 1873-1252. ; 21:1-3, s. 499-506
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Tidskriftsartikel (refereegranskat)abstract
- I Fluorinated hyperbranched polymers and dendrimers with low optical losses and functionality to modify refractive index and add a cross-linking unit were developed. The results of refractive index. measurements indicate a tunability of the refractive index between approximately 1.5 and 1.6, and optical losses below 0.5 dB/cm at 1550 nm. Dendrimers with similar, surface group structure and possibility to surface functionalization were prepared using a lanthanide. cation as focal point. Results on luminescent properties in the NIR and IR regions were measured for lanthanide ions such as Nd3+ and Er3+, showing characteristic emission bands at 1.06, 1.3 and 1.5 mum. The associated absorption and excitation spectra were found similar to those of the corresponding ions in optical glasses.
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| 28. |
- Pitois, C., et al.
(författare)
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Functionalized fluorinated hyperbranched polymers for optical waveguide applications
- 2001
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Ingår i: Advanced Materials. - 0935-9648 .- 1521-4095. ; 13:19, s. 1483-1487
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Tidskriftsartikel (refereegranskat)abstract
- Fluorinated dendritic or hyperbranched polymers are demonstrated for the first time to be potentially useful for optical waveguide applications, for example in telecommunications. The required materials properties include the control of the refractive index over a wide range and UV-crosslinking for ease of processing and stable long-term mechanical properties. The authors report the synthesis of suitable functionalized fluorinated hyperbranched polymers and how the above requirements can be met by functionalization at the periphery of the polymers.
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| 29. |
- Thuvander, A., et al.
(författare)
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Levels of ochratoxin A in blood from Norwegian and Swedish blood donors and their possible correlation with food consumption
- 2001
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Ingår i: Food and Chemical Toxicology. - 0278-6915 .- 1873-6351. ; 39:12, s. 1145-1151
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Tidskriftsartikel (refereegranskat)abstract
- Blood levels of ochratoxin A were determined in 406 Scandinavian blood donors (206 from Oslo, Norway, and 200 from Visby on the island of Gotland, Sweden), using an HPLC method. In connection with the blood collection, the subjects were asked to fill in a food questionnaire to obtain individual dietary information relevant to ochratoxin A exposure. The mean plasma level of ochratoxin A was 0.18 ng/ml in Oslo and slightly higher, 0.21 ng/ml (P = 0.046) in Visby. There was no correlation between plasma levels of ochratoxin A and the estimated total dietary intake of ochratoxin A based on consumption data and levels in food (retrieved from the literature), neither was the plasma level of ochratoxin A correlated with the total amount of food consumed. However, consumption of several foods, including cereal products, wine, beer and pork, were to some minor degree related to high plasma levels of ochratoxin A. The strongest correlations (correlation coefficient r >0.4; P <0.001) were observed for women in relation to the consumption of beer or medium brown bread. Correlation analysis of combinations of two or more food categories did not result in any statistically significant correlation.
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| 30. |
- Vestberg, Robert, et al.
(författare)
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Dendritic polyesters for optical applications
- 2003
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Ingår i: ORGANIC NANOPHOTONICS. - DORDRECHT, NETHERLANDS : SPRINGER. - 1402012799 ; , s. 169-176
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Konferensbidrag (refereegranskat)abstract
- In the protection against lasers, optical power limiting (OPL) is an area of interest. We have explored the effect of using dendritic molecules, based on bis-MPA (2,2-bis(methylol)-propionic acid), as encapsulants; of porphyrine and thiophene dyes having OPL-properties. Preliminary results indicate that the OPL-effect of the porphyrine is increased approximately by a factor 2 if the porphyrine is. decorated with dendritic wedges. This is thought to be a result of isolation of the dye leading to extended lifetimes for the excited states, increasing the probability for multi-photon absorption. For the thiophenes no OPL-effect was observed. This was probably due to the small size of the dendrons; (first generation).
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