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- Westermark, Karin, et al.
(författare)
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Determination of the electronic density of states at a nanostructured TiO2/Ru-dye/electrolyte interface by means of photoelectron spectroscopy
- 2002
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Ingår i: Chemical Physics. - 0301-0104 .- 1873-4421. ; 285:1, s. 157-165
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Tidskriftsartikel (refereegranskat)abstract
- In this work, photoelectron spectroscopy is used to measure the electronic density of states in the band gap region of a nanostructured TiO2 film. Such nanostructured films are used in dye-sensitized solar cells, and in this study a plain TiO2 film as well as a dye-sensitized film were examined. Further, to simulate the electrolyte effect on the energy levels at the oxide/dye/electrolyte interface in a solar cell, the density of states in the band gap region for an electrochemically prepared TiO2 film inserted with Li+ ions was measured. From the experimental findings we discuss the distribution and chemical nature of electron trap states in the band gap and the energy matching between the LUMO level of the adsorbed dye, cis-bis(4,4′-dicarboxy-2,2′-bipyridine)-bis(isothiocyanato)ruthenium(II), and the TiO2 conduction band edge.
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- Bidleman, TF, et al.
(författare)
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Chiral signatures of chlordanes indicate changing sources to the atmosphere over the past 30 years
- 2004
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 38:35, s. 5963-5970
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Tidskriftsartikel (refereegranskat)abstract
- Chlordane was used as an insecticide for half a century until its withdrawal from the world market in 1997. Trans- and cis-chlordane (TC, CC) are racemic in the technical product, but undergo enantio selective degradation in soil to leave nonracemic residues. In most cases, the (+) enantiomer of TC and the (-) enantiomer of CC are depleted, leading to enantiomer fractions, EF = (+)/[(+) + (-)], that are < 0.500 for TC and > 0.500 for CC. Nonracemic EFs of TC and CC, showing the same degradation preference as soils, were found in 1998-2001 air samples from stations in Arctic Canada and Finland, and on the west coast of Sweden. Environmental samples representing different time periods of chlordane history were also examined in: (a) archived atmospheric deposition samples collected in Sweden, Slovakia and Iceland in 1971-1973, (b) soils from southern Sweden sampled in 2001 and (c) a laminated lake sediment core from the Canadian Arctic representing similar to50 years of accumulation. TC and CC were racemic or nearly so in the historical atmospheric deposition samples and nonracemic in the Swedish soils. The EF of TC in the dated take sediment core decreased from nearly racemic in the past to nonracemic in recent times. These observations suggest that sources of chlordane to the atmosphere have changed over time and are now influenced to a greater extent by emission from soils.
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- Cetkauskaite, A, et al.
(författare)
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Elemental sulfur: Toxicity in vivo and in vitro to bacterial luciferase, in vitro yeast alcohol dehydrogenase, and bovine liver catalase
- 2004
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Ingår i: Environmental Toxicology. - : Wiley. - 1520-4081. ; 19:4, s. 372-386
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this research was to analyze the effects and the modes of action of elemental sulfur (So) in bioluminescence and respiration of Vibrio fischeri cells and the enzymes crude luciferase, pure catalase, and alcohol dehydrogenase (ADH). Metallic copper removed sulfur and reduced the toxicity of acetone extracts of sediment samples analyzed in the bioluminescence test. The sulfur inhibition of cell bioluminescence was noncompetitive with decanal, the luciferase substrate; reversible, with maximum toxicity after 15 min (EC50 = 11.8 mug/L); and almost totally recovered after 2 h. In vitro preincubation of crude luciferase extract with sulfur (0.28 ppm) weakly inhibited bioluminescence at 5 min, but at 30 min the inhibition reached 60%. Increasing the concentration of sulfur in the parts per million concentration range in vitro decreased bioluminescence, which was not constant, but depended on exposure time, and no dead-end/total inhibition was observed. The redox state of enzymes in the in vitro system significantly affected inhibition. Hydrogen peroxide restored fully and the reducing agent dithiothreitol, itself toxic, restored only partially luciferase activity in the presence of sulfur. Sulfur (5.5 ppm) slightly inhibited ADH and catalase, and dithiothreitol enhanced sulfur inhibition. High sulfur concentrations (2.2 ppm) inhibited the bioluminescence and enhanced the respiration rate of V. fischeri cells. Elemental sulfur data were interpreted to show that sulfur acted on at least a few V. fischeri cell sites: reversibly modifying luciferase at sites sensitive to/protected by oxidative and reducing agents and by affecting electron transport processes, resulting in enhanced oxygen consumption. Sulfur together with an enzyme reducing agent inhibited the oxidoreductive enzymes ADH and catalase, which have -SH groups, metal ion cofactors, or heme, respectively, in their active centers.© 2004 Wiley Periodicals, Inc. Environ Toxicol 19: 372-386, 2004.
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- Munday, B L, et al.
(författare)
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Accumulation of persistent organic pollutants in Tasmanian platypus (Ornithorhynchus anatinus)
- 2002
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Ingår i: Environmental Pollution. - 0269-7491. ; 120:2, s. 233-237
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Tidskriftsartikel (refereegranskat)abstract
- Tailfat samples were collected from 56 platypuses, 38 male and 18 fernale in Tasmania. No statistically significant, nor apparent, differences between the sexes were found for tailfat lipid levels and DDT and its metabolites, Lindane and PCB concentrations in tailfat lipid. Apparently-but not statistically-significantly different levels of DDT and its metabolites, Lindane and PCB concentrations were found in animals from different geographic regions of the State. Higher concentrations of DDT and its metabolites and Lindane were related to the intensity of agricultural activity and elevated PCB levels were mainly found in animals from zones with industrial and hydroelectric developments. (C) 2002 Elsevier Science Ltd. All rights reserved.
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