| 1. |
- Thomas, HS, et al.
(författare)
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- 2019
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swepub:Mat__t
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| 2. |
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| 3. |
- Romanelli, F, et al.
(författare)
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Overview of the JET results
- 2011
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 51:9
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Tidskriftsartikel (refereegranskat)abstract
- Since the last IAEA Conference JET has been in operation for one year with a programmatic focus on the qualification of ITER operating scenarios, the consolidation of ITER design choices and preparation for plasma operation with the ITER-like wall presently being installed in JET. Good progress has been achieved, including stationary ELMy H-mode operation at 4.5 MA. The high confinement hybrid scenario has been extended to high triangularity, lower ρ*and to pulse lengths comparable to the resistive time. The steady-state scenario has also been extended to lower ρ*and ν*and optimized to simultaneously achieve, under stationary conditions, ITER-like values of all other relevant normalized parameters. A dedicated helium campaign has allowed key aspects of plasma control and H-mode operation for the ITER non-activated phase to be evaluated. Effective sawtooth control by fast ions has been demonstrated with3He minority ICRH, a scenario with negligible minority current drive. Edge localized mode (ELM) control studies using external n = 1 and n = 2 perturbation fields have found a resonance effect in ELM frequency for specific q95values. Complete ELM suppression has, however, not been observed, even with an edge Chirikov parameter larger than 1. Pellet ELM pacing has been demonstrated and the minimum pellet size needed to trigger an ELM has been estimated. For both natural and mitigated ELMs a broadening of the divertor ELM-wetted area with increasing ELM size has been found. In disruption studies with massive gas injection up to 50% of the thermal energy could be radiated before, and 20% during, the thermal quench. Halo currents could be reduced by 60% and, using argon/deuterium and neon/deuterium gas mixtures, runaway electron generation could be avoided. Most objectives of the ITER-like ICRH antenna have been demonstrated; matching with closely packed straps, ELM resilience, scattering matrix arc detection and operation at high power density (6.2 MW m-2) and antenna strap voltages (42 kV). Coupling measurements are in very good agreement with TOPICA modelling. © 2011 IAEA, Vienna.
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| 4. |
- Abel, I, et al.
(författare)
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Overview of the JET results with the ITER-like wall
- 2013
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 53:10, s. 104002-
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Tidskriftsartikel (refereegranskat)abstract
- Following the completion in May 2011 of the shutdown for the installation of the beryllium wall and the tungsten divertor, the first set of JET campaigns have addressed the investigation of the retention properties and the development of operational scenarios with the new plasma-facing materials. The large reduction in the carbon content (more than a factor ten) led to a much lower Z(eff) (1.2-1.4) during L- and H-mode plasmas, and radiation during the burn-through phase of the plasma initiation with the consequence that breakdown failures are almost absent. Gas balance experiments have shown that the fuel retention rate with the new wall is substantially reduced with respect to the C wall. The re-establishment of the baseline H-mode and hybrid scenarios compatible with the new wall has required an optimization of the control of metallic impurity sources and heat loads. Stable type-I ELMy H-mode regimes with H-98,H-y2 close to 1 and beta(N) similar to 1.6 have been achieved using gas injection. ELM frequency is a key factor for the control of the metallic impurity accumulation. Pedestal temperatures tend to be lower with the new wall, leading to reduced confinement, but nitrogen seeding restores high pedestal temperatures and confinement. Compared with the carbon wall, major disruptions with the new wall show a lower radiated power and a slower current quench. The higher heat loads on Be wall plasma-facing components due to lower radiation made the routine use of massive gas injection for disruption mitigation essential.
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| 5. |
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| 6. |
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| 7. |
- Schael, S, et al.
(författare)
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Precision electroweak measurements on the Z resonance
- 2006
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Ingår i: Physics Reports. - : Elsevier BV. - 0370-1573 .- 1873-6270. ; 427:5-6, s. 257-454
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Forskningsöversikt (refereegranskat)abstract
- We report on the final electroweak measurements performed with data taken at the Z resonance by the experiments operating at the electron-positron colliders SLC and LEP. The data consist of 17 million Z decays accumulated by the ALEPH, DELPHI, L3 and OPAL experiments at LEP, and 600 thousand Z decays by the SLID experiment using a polarised beam at SLC. The measurements include cross-sections, forward-backward asymmetries and polarised asymmetries. The mass and width of the Z boson, m(Z) and Gamma(Z), and its couplings to fermions, for example the p parameter and the effective electroweak mixing angle for leptons, are precisely measured: m(Z) = 91.1875 +/- 0.0021 GeV, Gamma(Z) = 2.4952 +/- 0.0023 GeV, rho(l) = 1.0050 +/- 0.0010, sin(2)theta(eff)(lept) = 0.23153 +/- 0.00016. The number of light neutrino species is determined to be 2.9840 +/- 0.0082, in agreement with the three observed generations of fundamental fermions. The results are compared to the predictions of the Standard Model (SM). At the Z-pole, electroweak radiative corrections beyond the running of the QED and QCD coupling constants are observed with a significance of five standard deviations, and in agreement with the Standard Model. Of the many Z-pole measurements, the forward-backward asymmetry in b-quark production shows the largest difference with respect to its SM expectation, at the level of 2.8 standard deviations. Through radiative corrections evaluated in the framework of the Standard Model, the Z-pole data are also used to predict the mass of the top quark, m(t) = 173(+10)(+13) GeV, and the mass of the W boson, m(W) = 80.363 +/- 0.032 GeV. These indirect constraints are compared to the direct measurements, providing a stringent test of the SM. Using in addition the direct measurements of m(t) and m(W), the mass of the as yet unobserved SM Higgs boson is predicted with a relative uncertainty of about 50% and found to be less than 285 GeV at 95% confidence level. (c) 2006 Elsevier B.V. All rights reserved.
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| 8. |
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| 9. |
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| 10. |
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| 11. |
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| 12. |
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| 13. |
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| 14. |
- Chen, LC, et al.
(författare)
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Excitation transfer in polymer photodiodes for enhanced quantum efficiency
- 2000
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Ingår i: Advanced Materials. - 0935-9648 .- 1521-4095. ; 12:15, s. 1110-
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Tidskriftsartikel (refereegranskat)abstract
- The realization of polymer solar cells is the driving force behind this research. In an idea inspired by photosynthesis, the authors have constructed efficient bilayer photodiodes by a well-chosen combination of conjugated polymers (see Figure) in the donor layer. Forster energy transfer within the donor layer allows the absorbed light to be channeled to the C-60 acceptor layer, improving the total photoconversion of the blend device.
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| 15. |
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| 16. |
- Efstathopoulos, P, et al.
(författare)
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NR3C1 hypermethylation in depressed and bullied adolescents
- 2018
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Ingår i: Translational psychiatry. - : Springer Science and Business Media LLC. - 2158-3188. ; 8:1, s. 121-
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Tidskriftsartikel (refereegranskat)abstract
- The disruption of key epigenetic processes during critical periods of brain development can increase an individual’s vulnerability to psychopathology later in life. For instance, DNA methylation in the glucocorticoid receptor gene (NR3C1) in adulthood is known to be associated with early-life adversities and has been suggested to mediate the development of stress-related disorders. However, the association between NR3C1 methylation and the emergence of internalizing symptoms in childhood and adolescence has not been studied extensively. In the present report, we used saliva DNA from a cohort of Swedish adolescents (13–14 years old; N = 1149) to measure NR3C1 methylation in the exon 1F region. Internalizing psychopathological symptoms were assessed using the Center for Epidemiologic Studies Depression Scale for Children (CES-DC). We found that NR3C1 hypermethylation was cross-sectionally associated with high score for internalizing symptoms in the whole group as well as among the female participants. In addition, an analysis of social environmental stressors revealed that reports of bullied or lacking friends were significantly associated with NR3C1 hypermethylation. This cross-sectional association of NR3C1 exon 1F hypermethylation with internalizing psychopathology in adolescents, as well as with bullying and lack of friends are novel results in this field. Longitudinal studies are needed to address whether NR3C1 methylation mediates the link between social stressors and psychopathology in adolescence.
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| 17. |
- Fridén, H, et al.
(författare)
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Low temperature EPR and MCD studies on cytochrome b-558 of the Bacillus subtilis succinate: quinone oxidoreductase indicate bis-histidine coordination of the heme iron
- 1990
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Ingår i: Biochimica et Biophysica Acta - Bioenergetics. - 0005-2728. ; 1041:2, s. 207-215
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Tidskriftsartikel (refereegranskat)abstract
- Bacillus subtilis cytochrome b-558 was expressed in high amounts in Escherichia coli, solubilized from membranes with detergent and purified free from other hemoproteins. The cytochrome possibly contains two heme groups. To determine the axial ligands to the low-spin heme and the heme rhombicity, the cytochrome was analyzed using low-temperature electron paramagnetic resonance (EPR) and magnetic circular dichroism (MCD) spectroscopy. The combined results exclude bis-methionine, bis-lysine and histidine-methionine coordination. Bis-histidine coordination of the heme(s) with a near perpendicular orientation of the imidazole planes is strongly suggested by the highly axial low-spin EPR signals and the intense near infrared MCD spectrum (Δϵ=380 M−1·cm−1 at 4.2 K and 5 T) of the charge-transfer band at 1600 nm.
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| 18. |
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| 19. |
- Galanti, MR, et al.
(författare)
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Current tobacco use and COVID-19 diagnoses in a cohort of adult clients of public dental clinics in Sweden
- 2023
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Ingår i: Scientific reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 13:1, s. 1204-
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Tidskriftsartikel (refereegranskat)abstract
- Smoking has been linked with both increased and decreased risk of COVID-19, prompting the hypothesis of a protective role of nicotine in the pathogenesis of the disease. Studies of the association between use of smokeless tobacco and COVID-19 would help refining this hypothesis. We analysed data from 424,386 residents in the Stockholm Region, Sweden, with information on smoking and smokeless tobacco (snus) use prior to the pandemic obtained from dental records. Diagnoses of COVID-19 between February and October 2020 were obtained from health-care registers. We estimated the risk of receiving a diagnosis of COVID-19 for current smokers and for current snus users relative to non-users of tobacco, adjusting for potential confounders (aRR). The aRR of COVID -19 was elevated for current snus users (1.09 ;95%CI = 0.99–1.21 among men and 1.15; 95%CI = 1.00–1.33 among women). The risk for women consuming more than 1 can/day was twice as high as among non-users of tobacco. Current smoking was negatively associated with risk of COVID-19 (aRR = 0.68; 95% CI = 0.61–0.75); including hospital admission (aRR = 0.60; 95% CI = 0.47–0.76) and intensive care (aRR = 0.43; 95% CI = 0.21–0.89). The hypothesis of a protective effect of tobacco nicotine on COVID-19 was not supported by the findings. The negative association between smoking and COVID-19 remains unexplained.
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| 20. |
- Gillissen, S, et al.
(författare)
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Synthesis and characterization of poly(pyridine vinylene) via the sulfinyl precursor route
- 2001
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Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 34:21, s. 7294-7299
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis and characterization of poly(pyridine vinylene) (PPyV) via the nonionic sulfinyl precursor route is presented. Starting from an unsymmetrical monomer, precursor polymers were prepared in various solvents, which led to polymers with variable molecular weights. The thermal conversion to the conjugated structure, as well as its stability, was studied with different techniques such as FT-IR, UV-vis, TGA, and direct insertion probe mass spectroscopy (DIP-MS). From these results we were able to derive the most suitable conditions to perform the conversion. The fully conjugated PPyV was further characterized with photoluminescence (PL) and cyclic voltammetry (CV) measurements. The PL efficiency was found to be as high as 14%. The CV measurements showed that the polymer can be reduced (n-doped).
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| 21. |
- Godovsky, D, et al.
(författare)
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The use of combinatorial materials development for polymer solar cells
- 2000
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Ingår i: Advanced Materials for Optics and Electronics. - 1057-9257 .- 1099-0712. ; 10:2, s. 47-54
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Tidskriftsartikel (refereegranskat)abstract
- Vile use a combinatorial approach to develop molecular plastic solar cells based on soluble fullerene derivatives blended with conjugated polymers. A combinatorial way of sample preparation is well suited to deal with the multitude of possible combinations of the components of such blends. We use high mobility poly(thiophene) and poly(phenylenevinylene) derivatives to be combined with accepters, Gradients of methanofullerene/polymer concentration were formed by diusion of the low molecular weight component in the spin-cast polymer matrix, Likewise the gradients of zinc phthalocyanine/C-60 were prepared by co-evaporation of the two materials from two sources to make a linear array of photodiode devices, Photo- and electrophysical properties, such as absorption, luminescence, short circuit photocurrent and open circuit photovoltage, were measured using a specially designed installation with a resolution of 70-100 mu. Clear evidence was obtained that the photoconversion efficiency increased with the amount of methanofullerene up to very high levels, in the case of methanofullerene/polymer blends, verifying the important role of the acceptor in the photoconversion. By choosing the optimal ratio between C-60 and ZnPc in the evaporated layer it Is possible to obtain high photocurrent in the 600-700 nm range, due to the added contribution from photoinduced electron transfer between the two molecules, Copyright (C) 2000 John Wiley & Sons, Ltd.
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| 22. |
- Granlund, T, et al.
(författare)
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Luminescence probing of crystallization in a polymer film
- 2000
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Ingår i: Journal of Applied Physics. - 0021-8979 .- 1089-7550. ; 87:12, s. 8549-8556
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Tidskriftsartikel (refereegranskat)abstract
- We report studies of a thin film multilayer stack including a highly emissive substituted polythiophene, poly[3-(2,5-dioctylphenyl)thiophene]. Analysis of the photoluminescence spectra revealed an inhomogeneous polymer film. X-ray diffraction studies attribute the existence of an inhomogeneous film as originating from crystallization of the polymer. We used the interference effect of light to detect the region of crystallization in the film. Photoluminescence and absorption were redshifted upon crystallization and displayed an enhanced vibronic structure. Comparison between calculated and measured photoluminescence shows that the crystallization starts from the top of the film and not from the supporting substrate. (C) 2000 American Institute of Physics. [S0021- 8979(00)08112-3].
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| 23. |
- Gustafsson, Carlberg JC, et al.
(författare)
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Tuning the bandgap for polymeric smart windows and displays
- 1995
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Ingår i: ELECTROCHIMICA ACTA. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0013-4686. ; 40:13-14, s. 2233-2235
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Tidskriftsartikel (refereegranskat)abstract
- The band gap, and thus the optical properties, of polythiophene can be turned for use in electrochromic applications by attaching substituents to the monomers before polymerization. Electron donating substituents lower the bandgap, while steric inter
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| 24. |
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| 25. |
- Hjorvarsson, B, et al.
(författare)
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Probing the local electronic structure in the H induced metal-insulator transition of Y
- 1999
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Ingår i: JOURNAL OF PHYSICS-CONDENSED MATTER. ; 11, s. L119-
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Tidskriftsartikel (refereegranskat)abstract
- The occupied acid unoccupied valence band states of yttrium (Y) metal, Y dihydride and Y trihydride were measured by soft x-ray emission and absorption spectroscopy. The experiments were complemented by first principles calculations. Both experiments and
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| 26. |
- Inganäs, Olle, et al.
(författare)
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Optical emission from confined poly(thiophene) chains
- 1998
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Ingår i: Optical materials (Amsterdam). - : Elsevier. - 0925-3467 .- 1873-1252. ; 9:1-4, s. 104-108
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Tidskriftsartikel (refereegranskat)abstract
- We discuss the stages of the luminescence processes in substituted and soluble poly(thiophenes), using results from determinations of absolute quantum yields of photoluminescence, fast pump-probe experiments and microcavity devices. Enhancement of the quantum yield of photoluminescence, with poly(thiophenes) in the solid state, call be obtained by dispersing the conjugated chain in a molecularly dispersed polymer blend, or by adding side chains designed for forcing the conjugated main chains apart. At the wavelength of stimulated emission, we observe a narrow bandwidth emission in the high-Q one-dimensional microcavity devices prepared by sandwiching two dielectric mirrors around a thin polymer film, A strong enhancement of the power efficiency is observed at a pump power of 1 mu W/cm(2), but does not conclusively show lasing characteristics. (C) 1998 Elsevier Science B.V.
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| 27. |
- Johansson, DM, et al.
(författare)
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Influence of polymerization temperature on molecular weight, photoluminescence, and electroluminescence for a phenyl-substituted poly(p-phenylenevinylene)
- 2001
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Ingår i: Macromolecules. - 0024-9297 .- 1520-5835. ; 34:11, s. 3716-3719
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Tidskriftsartikel (refereegranskat)abstract
- We present the synthesis and characterization of poly(2-(2",5'-bis(2"-ethylhexyloxy)phenyl)-1,4-phenylenevinylene) (BEHP-PPV) polymerized at different temperatures. The photoluminescence efficiencies in the solid state of BEHP-PPV obtained at 144 and 0 degreesC are 28% and 60%, respectively. H-1 NMR measurements showed a lower concentration of structural defects for BEHP-PPV obtained at lower temperatures, which can explain the increased photoluminescence efficiencies for these polymers. Polymerization temperatures below 0 degreesC decrease the molecular weight without changing the photoluminescence efficiency to any large extent. The electroluminescence efficiencies follow the trend in the photoluminescence efficiencies.
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| 28. |
- Johansson, DM, et al.
(författare)
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Synthesis and characterization of polyfluorenes with light-emitting segments
- 2001
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Ingår i: Macromolecules. - 0024-9297 .- 1520-5835. ; 34:6, s. 1981-1986
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Tidskriftsartikel (refereegranskat)abstract
- Two new polymers consisting of poly(9-(2'-ethylhexyl)-9-hexylfluorene) (EHH-PF) with a small amount of substituted poly(p-phenylenevinylene) (PPV) segments have been synthesized and characterized. The synthetic route was designed to allow the incorporation of only one (or zero) PPV segments per polymer chain. Photoluminescence measurements showed that energy transfer from the PF segments to the more narrow band-gap PPV segments did occur, both in solution and in film. In the solid state, all emissions were detected from the PPV segments with photoluminescence quantum yields up to 68%. One of the polymers has been used as the active material in a microcavity laser device. The threshold for lasing is 2 muJ/cm(2).
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| 29. |
- Johansson, DM, et al.
(författare)
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Synthesis of soluble phenyl-substituted poly(p-phenylenevinylenes) with a low content of structural defects
- 2002
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Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 35:13, s. 4997-5003
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis and characterization of two new soluble poly(p-phenylenevinylenes) (PPVs) are reported. The polymers are poly(2-2',5'-bis(octyloxy)benzene)-1,4-phenylenevinylene) (BOP-PPV) and poly(2-(2',5'-bis(octyloxy)benzene)-5-methoxy-1,4-phenylenevinylene) (BOPM-PPV). Both polymers have been polymerized at high and low temperatures to study the formation of structural defects. It is shown that both methoxy groups as side chains and low polymerization temperatures decrease the content of defects in the final polymer. As a consequence, the polymers with lower concentration of defects exhibit higher electroluminescence yields in light-emitting diodes. In addition to this, the polymers with a low content of defects exhibited longer operational lifetimes in these devices. The highest photoluminescence quantum yield in the solid state and electroluminescence efficiency were found to be 72% and 1.74%, respectively.
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| 30. |
- Jonforsen, M, et al.
(författare)
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Synthesis and characterization of soluble and n-dopable poly(quinoxaline vinylene)s and poly(pyridopyrazine vinylene)s with relatively small band gap
- 2002
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Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 35:5, s. 1638-1643
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Tidskriftsartikel (refereegranskat)abstract
- Synthesis and characterization of poly(quinoxaline vinylene)s and poly(pyridopyrazine vinylene)s with linear and branched aliphatic side chains are reported. The electron affinity of the polymers was measured with cyclic voltammetry (CV) and found to be highest for the pyridopyrazine vinylene polymers, Compared to CN-MEH-PPV, the pyridopyrazine vinylene polymers were easier to reduce, while the quinoxaline derivatives were harder. UV-vis absorption measurements showed that the polymers have relatively small band gaps.
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| 31. |
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| 33. |
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| 34. |
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| 35. |
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| 36. |
- Nguyen, TTD, et al.
(författare)
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Randomised controlled study of two counselling models at the Swedish alcohol helpline: Effectiveness and sustainability outcomes at 12-month follow-up
- 2022
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Ingår i: Nordisk alkohol- & narkotikatidskrift : NAT. - : SAGE Publications. - 1458-6126. ; 39:2, s. 163-174
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Tidskriftsartikel (refereegranskat)abstract
- Aim: This two-arm parallel randomised controlled trial explored the effectiveness of a brief counselling model compared with the usual multi-session counselling at an alcohol telephone helpline. Methods: A total of 320 callers who contacted the Swedish Alcohol Helpline (SAH) because of hazardous or harmful alcohol use were randomised to either brief structured intervention (self-help booklet plus one proactive call) or usual care (multi-session telephone counselling). The primary outcome was a downward shift in risk level at 12-month follow-up compared with baseline, based on self-reports. Sustained risk level reduction throughout the whole follow-up was also assessed as secondary outcome. Results: Both interventions were significantly associated with a shift to a lower level of risky alcohol use (75% among participants in the brief structured intervention, and 70% in the usual care group) after 12 months. There was no difference between the two interventions in the proportions changing alcohol use or sustaining risk level reduction. Conclusion: In the context of telephone helplines, minimal and extended interventions appear to be equally effective in promoting long-term change in alcohol use.
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| 37. |
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| 38. |
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| 39. |
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| 40. |
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| 41. |
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| 42. |
- Rastad, AA, et al.
(författare)
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Management of infections caused by respiratory syncytial virus
- 2001
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Ingår i: Scandinavian Journal of Infectious Diseases. - 0036-5548 .- 1651-1980. ; 33:5, s. 323-328
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Tidskriftsartikel (refereegranskat)abstract
- This is a consensus document compiled by the Medical Products Agency in Sweden and the Swedish Reference Group for Antiviral Therapy on management of respiratory syncytial virus (RSV) infections. Prophylaxis against RSV infections using palivizumab, a commercially available humanized monoclonal IgG, antibody preparation, is recommended for children <2 y of age with chronic respiratory diseases requiring continuous treatment (oxygen and/or inhalations and/or steroids) during the previous 6 months and children 6 months old who were born before gestational week 26. Ribavirin inhalation treatment may be considered in high-risk infants with clinical symptoms indicating a serious course of an RSV infection. Treatment with ribavirin in combination with intravenous polyclonal immunoglobulin should be considered in patients who have received an allogenic stem cell transplantation or organ transplantation with >1 episode of rejection treatment and who have mild or moderate RSV pneumonia. Evidence-based documentation for treatment of other groups of patients is lacking.
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| 43. |
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| 44. |
- Roman, LS, et al.
(författare)
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Photovoltaic devices based on photo induced charge transfer in polythiophene : CN-PPV blends
- 2003
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Ingår i: Brazilian journal of physics. - 0103-9733 .- 1678-4448. ; 33:2, s. 376-381
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the photovoltaic properties of polymer devices based on a blend of two polymers, (poly(3-(2'-methoxy-5'-octylphenyl) thiophene) (POMeOPT) and poly(2,5,2',5'-tetrahexyloxy-7,8'-dicyanodi-p-phenylenevinylene) (CN-PPV), where photo induced charge transfer takes place at the interfaces formed by the interpenetrating network of the donor and the acceptor. The polymer blend films resulting from the spin coating were phase separated and the photo response of the devices depended on the morphology of the segregation. We have studied different blend ratios by photoluminescence quenching, scanning force microscopy and photovoltaic measurements. External quantum efficiencies of 4.5% at 500nm were achieved for the less segregated polymer blend.
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| 45. |
- Roman, LS, et al.
(författare)
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Trapping light in polymer photodiodes with soft embossed gratings
- 2000
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Ingår i: Advanced Materials. - 0935-9648 .- 1521-4095. ; 12:3, s. 189-
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Tidskriftsartikel (refereegranskat)abstract
- Increasing the conversion efficiency is very important in photovoltaic devices, as is cheap and simple technology. Here is demonstrated a soft embossing technique for printing a submicrometer grating with an elastomeric mold into an optically active polymer layer in a photovoltaic device (see Figure). The light trapping due to the grating pattern enhances the photoconversion efficiency by more than 25 % at normal light incidence (see also inside front cover).
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| 46. |
- Ruseckas, A, et al.
(författare)
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Intra- and interchain luminescence in amorphous and semicrystalline films of phenyl-substituted polythiophene
- 2001
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Ingår i: JOURNAL OF PHYSICAL CHEMISTRY B. - : American Chemical Society (ACS). - 1089-5647 .- 1520-6106 .- 1520-5207. ; 105:32, s. 7624-7631
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Tidskriftsartikel (refereegranskat)abstract
- We report time-resolved photoluminescence (PL) measurements of spin-cast amorphous films of a regioregular polythiophene derivative poly[3-(4-octylphenyl)thiophene] and of annealed semicrystalline films of the same polymer with an interchain stacking distance of 5 Angstrom. Red-shifted PL appears at long delay times in both pristine and annealed films, which we assign to interchain aggregates populated by excitation energy migration. Aggregate luminescence in annealed films exhibits a pronounced vibronic structure indicating the coupling to a C=C bond stretch with a Huang-Rhys factor S = 2. Two types of aggregates are distinguished in annealed films: in a few picoseconds most excitations are trapped by aggregates with a large energy gap (about 1.83 eV) between the lowest excited singlet state and the ground state. Excitation energy is transferred or the aggregates relax structurally with a time constant of about 200 ps to aggregates with a smaller energy gap (about 1.75 eV). The radiative lifetime of aggregates with smaller energy gap is estimated to be about 35 ns, two times longer than that of aggregates with the larger energy gap. In spin-cast amorphous films, emission from intrachain singlet excitons has a longer lifetime than in annealed films and only high-energy-gap aggregates are populated.
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| 47. |
- Ruseckas, A, et al.
(författare)
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Ultrafast photogeneration of inter-chain charge pairs in polythiophene films
- 2000
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Ingår i: Chemical Physics Letters. - 0009-2614 .- 1873-4448. ; 322:1-2, s. 136-142
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Tidskriftsartikel (refereegranskat)abstract
- Photoexcitation dynamics in films of polythiophenes with different side groups were studied by transient absorption spectroscopy using 80 fs pulses. We show that inter-chain charge pairs (CP) are generated with similar to 20% efficiency in a polymer with short inter-chain distance (similar to 4 Angstrom) within 100 fs after photoexcitation. We discuss two mechanisms for inter-chain charge separation: (i) electron or hole transfer from an initially excited intra-chain singlet state or (ii) optical excitation of mixed exciton-charge transfer states, which quickly evolve to inter-chain CPs. (C) 2000 Elsevier Science B.V, All rights reserved.
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