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Träfflista för sökning "WFRF:(Persson Anders) ;pers:(Persson Katarina)"

Sökning: WFRF:(Persson Anders) > Persson Katarina

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1.
  • Ersson, Anders, et al. (författare)
  • A comparison between hexaaluminates and perovskites for catalytic combustion applications
  • 2006
  • Ingår i: Catalysis Today. - 0920-5861. ; 112:04-jan, s. 157-160
  • Tidskriftsartikel (refereegranskat)abstract
    • Hexaaluminates and perovskites are two promising candidates for use in catalytic combustion applications. In the present study two hexaaluminates, LaMnAl11O19 and LaCoAl11O19, were compared with two perovskites, LaMnO3 and LaCoO3, with respect to their thermal stability and catalytic activity for combustion of methane and gasified biomass. The results showed that the hexaaluminates retained a much higher surface area even after calcination at 1200 degrees C compared to the perovskites. LaMnAl11O19 showed the highest catalytic activity of all catalysts. LaCoAl11O19 generally showed low activity. Of the two perovskites, LaCoO3 was the most active, and the initial test run the activity for biomass combustion were close to that one of LaMnAl11O19 even though its surface area was only one tenth of the hexaaluminate's. However, it was severely deactivated in the second test run. Similar deactivation but less severe was also found for the other catalyst.
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2.
  • Nilsson, Bengt-Olof, et al. (författare)
  • Effects of polyamine synthesis inhibition on polyamines, growth and mechanical properties in hypertrophic rat urinary bladder
  • 1998
  • Ingår i: Pharmacology & toxicology. - Munksgaard. - 0901-9928. ; 82:6, s. 287-294
  • Tidskriftsartikel (refereegranskat)abstract
    • The polyamines putrescine, spermidine and spermine, are ubiquitous intracellular metabolites associated with growth and protein synthesis. In this study effects of polyamine synthesis inhibition on bladder growth, polyamine levels and mechanical properties were investigated in rat urinary bladder subjected to partial outflow obstruction that causes bladder hypertrophy. The S-adenosyl methionine decarboxylase inhibitor CGP-48664 (5 and 20 mg kg-1) was administered alone or in combination with the ornithine decarboxylase inhibitor DFMO (500 mg kg-1), starting one day before creation of partial outflow obstruction and then daily for 7 days. The bladder muscle level of putrescine was increased 38 times and that of spermine reduced by 4 times while spermidine was unchanged after treatment with CGP-48664 (20 mg kg-1). The increase in putrescine was abolished in animals receiving CGP-48664 in combination with DFMO. Treatment with polyamine synthesis inhibitors could not prevent or reduce the hypertrophy of the bladder as judged by bladder wet weight and protein contents. The effects on polyamine quantities were not associated with changes in Ca(2+)-force relationship or in agonist and electrically stimulated force. In summary, treatment of rats with polyamine synthesis inhibitors resulted in changes in polyamine levels in the growing urinary bladder but did not affect growth or mechanical properties.
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3.
  • Persson, Katarina, et al. (författare)
  • Catalytic combustion of methane over bimetallic Pd-Pt catalysts: The influence of support materials
  • 2006
  • Ingår i: Applied Catalysis B: Environmental. - 0926-3373. ; 66, s. 175-185
  • Tidskriftsartikel (refereegranskat)abstract
    • The effect of support material on the catalytic performance for methane combustion has been studied for bimetallic palladium-platinum catalysts and compared with a monometallic palladium catalyst on alumina. The catalytic activities of the various catalysts were measured in a tubular reactor, in which both the activity and stability of methane conversion were monitored. In addition, all catalysts were analysed by temperature-programmed oxidation and in situ XRD operating at high temperatures in order to study the oxidation/reduction properties.The activity of the monometallic palladium catalyst decreases under steady-state conditions, even at a temperature as low as 470 degrees C. In situ XRD results showed that no decomposition of bulk PdO into metallic palladium occurred at temperatures below 800 degrees C. Hence, the reason for the drop in activity is probably not connected to the bulk PdO decomposition.All Pd-Pt catalysts, independently of the support, have considerably more stable methane conversion than the monometallic palladium catalyst. However. dissimilanties in activity and ability to reoxidise PdO were observed for the various support materials. Pd-Pt supported on Al2O3 was the most active catalyst in the low-temperature region, Pd-Pt supported on ceria-stabilised ZrO2 was the most active between 620 and 800 degrees C, whereas Pd-Pt supported on LaMnAl11O19 was superior for temperatures above 800 degrees C. The ability to reoxidise metallic Pd into PdO was observed to vary between the supports. The alumina sample showed a very slow reoxidation, whereas ceria-stabilised ZrO2 was clearly faster
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4.
  • Persson, Katarina, et al. (författare)
  • Influence of co-metals on bimetallic palladium catalysts for methane combustion
  • 2005
  • Ingår i: Journal of Catalysis. - 0021-9517. ; 231, s. 139-150
  • Tidskriftsartikel (refereegranskat)abstract
    • The catalytic combustion of methane has been investigated over eight different bimetallic palladium catalysts, comprising the co-metals Co, Rh, Ir, Ni, Pt, Cu, Ag, or An. The catalysts were characterized by TEM, EDS, PXRD, and temperature-programmed oxidation (TPO). It was found that a catalyst containing both Pd and Pt was the most promising, as it had a high activity that did not decline with time. The catalyst containing Pd and Ag was also a promising candidate, but its activity was slightly lower. For PdCo and PdNi, the co-metals formed spinel structures with the alumina support, with the result that the co-metals did not affect the combustion performance of palladium. For PdRh, PdIr, PdCu, and PdAg, the co-metals formed separate particles consisting of the corresponding metal oxide. These catalysts, except PdRh, showed a stable activity. For PdPt and PdAu, the co-metals formed alloys with palladium, and both catalysts showed a stable activity.
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5.
  • Persson, Katarina, et al. (författare)
  • Influence of molar ratio on Pd-Pt catalysts for methane combustion
  • 2006
  • Ingår i: Journal of Catalysis. - 0021-9517. ; 243:1, s. 14-24
  • Tidskriftsartikel (refereegranskat)abstract
    • The catalytic oxidation of methane was investigated over six catalysts with different palladium and platinum molar ratios. The catalysts were characterised by TEM, EDS, XPS, PXRD and temperature-programmed oxidation. The results suggest that in the bimetallic catalysts, an alloy between Pd and Pt was formed in close contact with the PdO phase, with an exception for the Pt-rich catalyst, where no PdO was observed. It was found that the molar ratio between palladium and platinum clearly influences both the activity and the stability of methane conversion. By adding small amounts of platinum into the palladium catalyst, improved activity was obtained in comparison with the monometallic palladium catalyst. However, higher amounts of platinum are required for stabilising the methane conversion. The most promising catalysts with respect to both activity and stability were Pd67Pt33 and Pd50Pt50. The platinum-rich catalyst showed very poor activity for methane conversion.
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6.
  • Persson, Katarina, et al. (författare)
  • Stability of palladium-based catalysts during catalytic combustion of methane: The influence of water
  • 2007
  • Ingår i: Applied Catalysis B : Environmental. - 0926-3373. ; 74:3-4, s. 242-250
  • Tidskriftsartikel (refereegranskat)abstract
    • The stability of methane conversion was studied over a Pd/Al2O3 catalyst and bimetallic Pd-Pt/Al2O3 catalysts. The activity of methane combustion over Pd/Al2O3 gradually decreased with time, whereas the methane conversion over bimetallic Pd-Pt catalysts was significantly more stable. The differences in combustion behavior were further investigated by activity tests where additional water vapor was periodically added to the feed stream. From these tests it was concluded that water speeds up the degradation process of the Pd/Al2O3 catalyst, whereas the catalyst containing Pt was not affected to the same extent. DRIFTS studies in a mixture of oxygen and methane revealed that both catalysts produce surface hydroxyls during combustion, although the steady state concentration on the pure Pd catalyst is higher for a fixed temperature and water partial pressure. The structure of the bimetallic catalyst grains with a PdO domain and a Pd-Pt alloy domain may be the reason for the higher stability, as the PdO domain appears to be more affected by the water generated in the combustion reaction than the alloy. Not all fuels that produce water during combustion will have stability issues. It appears that less strong binding in the fuel molecule will compensate for the degradation.
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7.
  • Persson, Katarina, et al. (författare)
  • Supported palladium-platinum catalyst for methane combustion at high pressure
  • 2005
  • Ingår i: Catalysis Today. - 0920-5861. ; 100, s. 479-483
  • Tidskriftsartikel (refereegranskat)abstract
    • Catalytic combustion of methane over a supported bimetallic Pd-Pt catalyst and a monometallic Pd catalyst has been investigated experimentally. Two different reactor configurations were used in the study, i.e. a tubular lab-scale reactor working at atmospheric pressure and a high-pressure reactor working at up to 15 bar. The results showed that the bimetallic catalyst has a clearly more stable activity during steady-state operation compare to the palladium only catalyst. The activity of the bimetallic catalyst was slightly higher than for the palladium catalyst. These results were established in both test facilities. Further, the impact of pressure on the combustion activity has been studied experimentally. The tests showed that the methane conversion decreases with increasing pressure. However, the impact of pressure is more prominent at lower pressures and levels out for pressures above 10 bar
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8.
  • Radziszewski, Piotr, et al. (författare)
  • Exogenously Administered Bombesin and Gastrin Releasing Peptide Contract the Female Rat Urethra In Vivo and In Vitro
  • 2011
  • Ingår i: Neurourology and Urodynamics. - Wiley-Blackwell Publishing, Inc. - 0733-2467. ; 30:8, s. 1681-1685
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Bombesin (BOM) and gastrin releasing peptide (GRP) have been located to the lower urinary tract. However, there is a paucity of data demonstrating the impact of these neuropeptides. Objectives: The present study investigates the impact of BOM and GRP in the female Sprague--Dawley rats 225 g b.w. n = 37 urethras in vitro and in vivo. Intraurethral pressure was recorded by a catheter placed at the maximum pressure zone corresponding to the intrinsic urethral spincter. Measurements: In vitro, the intraurethral pressure was measured in response to the administration of BOM and GRP and noradrenaline from perfused intact urethral/bladder preparations. In vivo, changes in intraurethral pressure were conducted in anesthetized subjects and compared with the basal intraurethral pressure and sham controls. Results: In vitro, the increase in intraurethral pressure induced by BOM was 23.6+/-3.2cmH(2)O, exceeding the pressure evoked with NA by 10.7cmH(2)O whereas GRP induced 10.7+/-1.6cmH(2)O, an increase of 3.3cmH(2)O but less than the NA evoked intraurethral pressure by 2.2cmH(2)O. Incubation with scopolamine (1 mu M), phentolamine (1 mu M), pancuronium (1 mu M), and indomethacin (1 mu M) did not produce any significant difference in the contractile responses to BOM or GRP. In vivo, the mean basal pressure was 22.9+/-1.4cmH(2)O. The intraurethral pressure evoked by BOM was 29.7cmH(2)O (21.3+/-1.3 to 51.0+/-1.6cmH(2)O), and for GRP, the evoked intraurethral pressure was 33.8cmH(2)O (22.3+/-1.9 to 56.2+/-30cmH(2)O). Conclusions: BOM and GRP may contribute to the control of continence by their contractile action on the sphincters of the lower urinary tract outflow region. Neurourol. Urodynam. 30:1681-1685, 2011. (C) 2011 Wiley Periodicals, Inc.
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