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Kvalitet och kritiskt tänkande
- 1997
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Samlingsverk (redaktörskap) (övrigt vetenskapligt/konstnärligt)abstract
- Denna rapport dokumenterar de föredrag som hölls vid konferensen Kvalitet och kritiskt tänkande som anordnades av Sociologiska institituionen i Lund våren 1997. Syftet med konferensen var att belysa kritiskt tänkande som kvalitetskriterium inom universitetsutbildningen. I skriften reflekterar utbildningsminister Carl Tham över kritiskt tänkande ur ett utbildningspolitiskt perspektiv. Gunilla Svingby, professor i pedagogik vid Lärarhögskolan i Malmö, gör en översikt över forskning om förhållandet mellan lärande och kritiskt tänkande. Karl-Axel Nilsson, Lunds universitets utvärderingschef, funderar i sin text över hur universitetsutbildningens bidrag till kritiskt tänkande kan utvärderas. Anders Persson diskuterar i sin uppsats universitetsutbildningens olika kvalitetsdimensioner.
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| 2. |
- Launois, Pascale, et al.
(författare)
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Pressure polymerized C60 single crystals: First x-ray diffraction results
- 1998
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Ingår i: Molecular Nanostructures. - Singapore : World Scientific. - 9789810232610 ; , s. 348-352
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Konferensbidrag (refereegranskat)abstract
- C60 single crystals compressed at approx. 1 GPa and heated at about 300 C are found to polymerize in one dimension without losing their crystalline order. The resulting structure is orthrhombic, with space group Pmnn and parameters a=9.14 Å, b=9.9 Å and c=14.66 Å. The X-ray single crystal results allow us to derive a polymerization mechanism, which may also, for instance, apply to one dimensional C60 polymers in the doped compounds. The new polymer phase is discussed with respect to the C60 pressure-temperature diagram. The comparison with the A1C60 polymers raises questions about the interchain and the alkali metal - fullerene interactins.
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| 3. |
- Moret, Roger, et al.
(författare)
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First X-ray diffraction analysis of pressure polymerized C60 single crystals
- 1997
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Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 40:1, s. 55-60
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Tidskriftsartikel (refereegranskat)abstract
- It is shown that C60 single crystals can be polymerized under relatively modest pressure-temperature conditions. The resulting single crystals exhibit long-range order and they are made up of 12 orientation variants. The structure is orthorhombic with a short intermolecular distance along the chains (9.14 Å), characteristic of covalent bonding. We propose a structural mechanism for the polymerization of fullerene-based compounds; it involves a shift of one of the (111) cubic planes together with a shortening of the (111) spacing. The configuration of the polymer chains presents interesting relations with that found in the A1C60 polymer compounds.
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| 4. |
- Nagel, Peter, et al.
(författare)
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C60 one- and two-dimensional polymers, dimers, and hard fullerite: Thermal expansion, anharmonicity, and kinetics of depolymerization
- 1999
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 60:24, s. 16920-16927
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Tidskriftsartikel (refereegranskat)abstract
- We report on high-resolution thermal expansion measurements of high-temperature-pressure treated C60 [one-dimensional (1D) and (2D) polymers and “hard fullerite”], as well as of C60 dimers and single crystal monomer C60 between 10 and 500 K. Polymerization drastically reduces the thermal expansivity from the values of monomeric C60 due to the stronger and less anharmonic covalent bonds between molecules. The expansivity of the “hard” material approaches that of diamond. The large and irreversible volume change upon depolymerization between 400 and 500 K makes it possible to study the kinetics of depolymerization, which is described excellently by a simple activated process, with activation energies of 1.9±0.1 eV (1D and 2D polymers) and 1.75±0.05 eV (dimer). Although the activation energies are very similar for the different polymers, the depolymerization rates differ by up to four orders of magnitude at a given temperature, being fastest for the dimers. Preliminary kinetic data of C70 polymers are presented as well.
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| 5. |
- Nagel, Peter, et al.
(författare)
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High-resolution thermal expansion of high-pressure polymerized and 'normal' C60 from 10-500 K: Kinetics of depolymerization
- 1998
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Ingår i: Molecular Nanostructures. - Singapore : World Scientific. - 9810232616 ; , s. 365-368
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Konferensbidrag (refereegranskat)abstract
- High-resolution capacitance dilatometry was used to study the thermal expansion of both 'normal' and polymer phases of C60. The expansivity, alpha(T), of 'normal' C60 exhibits an unusual temperature dependence above the orientational disordering transition at 260 K; alpha(T) decreases by about 30% from 260 to 500 K and appears to reach a minimum near 500 K. Polymerized C60 has a much smaller expansivity than normal C60 due to the stronger covalent bonding between molecules. The polymerized state converts back to 'normal' C60 at temperatures between 450 and 500 K. We show that this is an activated process with a well-defined activation energy of 1.92 eV and a volume increase of about 2%.
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| 6. |
- Persson, Per-Axel, et al.
(författare)
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High-pressure polymerized C60
- 1996
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Ingår i: Extended Abstracts of Carbon´96, European Carbon Conference, Newcastle-upon-Tyne 1996, volume 2. - : The British Carbon Group. ; , s. 746-747, s. 746-747
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 7. |
- Persson, Per-Axel, et al.
(författare)
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NMR and Raman characterization of pressure polymerized C-60
- 1996
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614 .- 1873-4448. ; 258:5-6, s. 540-546
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Tidskriftsartikel (refereegranskat)abstract
- Bulk C60 has been treated at 1.1 GPa and 550–585 K, producing a dense insoluble material which on heating to above 600 K reverts to normal C60. Raman and IR studies on modified material show a large number of new lines, and the Raman pentagon pinch mode shifts from 1469 to 1458 cm−1 as on photopolymerization. MAS NMR shows one broadened line at the original C60 shift 144 ppm and a small peak at about 77 ppm due to the bridging carbons. None of the new resonances observed for C60 polymerized by other methods were observed. The results verify previously suggested polymeric structures where the fullerence cages are connected by four-membered rings.
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| 8. |
- Persson, Per-Axel, et al.
(författare)
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Physical properties of pressure polymerized C60
- 1996
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Ingår i: High Pressure Science and Technology. - Singapore : World Scientific. - 9810225474 ; , s. 716-718
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Konferensbidrag (refereegranskat)abstract
- The properties of C60 have been studied after treatment at high temperature and high pressure (1.1 GPa and 565 K for 2 h). The treated material is insoluble in organic solvents. We present results obtained in NMR and Raman studies and measured data for the specific heat and the thermal expansion. Our results show clearly that there are no covalent bonds and no molecular rotation, but suggest that the molecules are slightly deformed and held together by weak pi-type bonds.
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| 9. |
- Persson, Per-Axel, et al.
(författare)
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The physical properties of high-pressure polymerized C60
- 1997
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Ingår i: Journal of Physics and Chemistry of Solids, volume 58, issue 11. - : Elsevier B.V.. ; 58:11, s. 1881-1885
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Konferensbidrag (refereegranskat)abstract
- We have studied the structural, thermophysical, and spectroscopic properties of polymeric C60 obtained by high pressure treatment at pressures and temperatures near 1 GPa and 600 K. We present here a brief overview of our results for the structural and thermophysical properties and a more detailed report on recent results obtained by Raman spectroscopy on both thin films, polycrystalline, and single crystal material. The results presented include a comparison between Raman results for photopolymerized and pressure polymerized thin films and a preliminary estimate of the binding energy of polymeric C60.
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| 10. |
- Soldatov, Alexander, et al.
(författare)
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Pressure polymerized C60 : Raman and NMR studies
- 1996
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Ingår i: Fullerenes and Fullerene Nanostructures. - Singapore : World Scientific. - 9810228538 ; , s. 344-348
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Konferensbidrag (refereegranskat)abstract
- The properties of bulk C60 have been studied after treatment at 1.1 GPa and 550-585 K. The treated material is insoluble in both toluene and 1,2-dichlorobenzene. Raman spectroscopy on modified aterial shows a large number of new lines, and the Raman pentagon pinch mode (Ag2) shifts from 1469 to 1458 /cm as on photopolymerization. MAS NMR shows one broadened line at the original C60 shift 144 ppm and a small peak at about 77 ppm due to the bridging carbons. The results verify previous suggested polymeric structures where the fullerene cages are connected by four-membered rings.
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