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Sökning: WFRF:(Persson F) > Mittuniversitetet

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1.
  • Boily, J F, et al. (författare)
  • Benzenecarboxylate surface complexation at the goethite (alpha-FeOOH)/water interface : I. A mechanistic description of pyromellitate surface complexes from the combined evidence of infrared spectroscopy, potentiometry, adsorption data, and surface complexation modeling
  • 2000
  • Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 16:13, s. 5719-5729
  • Tidskriftsartikel (refereegranskat)abstract
    • An investigation combining IR spectroscopy, potentiometric titrations, and adsorption experiments was carried out to study pyromellitate (1,2,4,5-benzenetetracarboxylate) sorption at the goethite (α-FeOOH)/water interface. The IR spectra show evidence of outer-sphere complexation throughout the pH range from 3 to 9. Below pH 6 additional IR spectroscopic features appear, which are tentatively assigned to inner-sphere complexes. A normalized IR peak area plot for each peak indicative of inner- and of outer-sphere complexes as a function of pH provided a semiquantitative surface speciation scheme. This scheme was successfully reproduced using surface complexation theory with a multisite complexation model calibrated on potentiometric titration and on adsorption data. The surface speciation was described with a binuclear outer-sphere complex on the {110} plane of goethite and a mononuclear inner-sphere complex on the {001} plane. Furthermore, as the IR spectra also indicated partial protonation of pyromellitate complexes at low pH, a partially protonated outer-sphere species on the {110} plane was included in the model.
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2.
  • Ekdahl, F., et al. (författare)
  • Introducing domain knowledge for selection of active factors in designed experiments
  • 2000
  • Ingår i: International Journal of Reliability, Quality and Safety Engineering (IJRQSE). - 0218-5393. ; 7:4, s. 341-356
  • Tidskriftsartikel (refereegranskat)abstract
    • Unreplicated factorial designs are widely used for designed experimentation in industry. In the analysis of designed experiments, the experimental factors influencing the response must be identified and separated from those that do not. An abundance of procedures intended to perform this selection have been introduced in the literature. A recent study indicated that the procedure due to Box and Meyer outperforms the lot of the other selection procedures in terms of efficiency and robustness. The procedure of Box and Meyer rests on a quasi-Bayesian foundation and utilizes generic domain knowledge, in the form of a common-for-all-factors a priori probability, that a factor significantly influences the response, to calculate an a posteriori probability for each factor. This paper suggests a strategy for introducing more elaborate domain knowledge about the experimental factors in the procedure of Box and Meyer, aiming to further improve its performance.
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3.
  • Johansson, L.I., et al. (författare)
  • Electronic structure of 6H-SiC(0001)
  • 1996
  • Ingår i: Physical Review B (Condensed Matter). - 0163-1829. ; 53:20, s. 13803-13807
  • Tidskriftsartikel (refereegranskat)
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4.
  • Rineau, F., et al. (författare)
  • Carbon availability triggers the decomposition of plant litter and assimilation of nitrogen by an ectomycorrhizal fungus
  • 2013
  • Ingår i: The ISME Journal. - : nternational Society for Microbial Ecology. - 1751-7362 .- 1751-7370. ; 7:10, s. 2010-2022
  • Tidskriftsartikel (refereegranskat)abstract
    • The majority of nitrogen in forest soils is found in organic matter-protein complexes. Ectomycorrhizal fungi (EMF) are thought to have a key role in decomposing and mobilizing nitrogen from such complexes. However, little is known about the mechanisms governing these processes, how they are regulated by the carbon in the host plant and the availability of more easily available forms of nitrogen sources. Here we used spectroscopic analyses and transcriptome profiling to examine how the presence or absence of glucose and/or ammonium regulates decomposition of litter material and nitrogen mobilization by the ectomycorrhizal fungus Paxillus involutus. We found that the assimilation of nitrogen and the decomposition of the litter material are triggered by the addition of glucose. Glucose addition also resulted in upregulation of the expression of genes encoding enzymes involved in oxidative degradation of polysaccharides and polyphenols, peptidases, nitrogen transporters and enzymes in pathways of the nitrogen and carbon metabolism. In contrast, the addition of ammonium to organic matter had relatively minor effects on the expression of transcripts and the decomposition of litter material, occurring only when glucose was present. On the basis of spectroscopic analyses, three major types of chemical modifications of the litter material were observed, each correlated with the expression of specific sets of genes encoding extracellular enzymes. Our data suggest that the expression of the decomposition and nitrogen assimilation processes of EMF can be tightly regulated by the host carbon supply and that the availability of inorganic nitrogen as such has limited effects on saprotrophic activities.
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5.
  • Verheggen, F, et al. (författare)
  • Electrophysiological and Behavioral Activity of Secondary Metabolites in the Confused Flour Beetle, Tribolium confusum
  • 2007
  • Ingår i: Journal of Chemical Ecology. - : Springer Science and Business Media LLC. - 0098-0331 .- 1573-1561. ; 33:3, s. 525-539
  • Tidskriftsartikel (refereegranskat)abstract
    • Several previous studies have addressed pheromone communication in various flour beetles (Coleoptera: Tenebrionidae), including the confused flour beetle, Tribolium confusum (du Val). Different stereoisomers of 4,8-dimethyldecanal (DMD) were reported as the only components of an aggregation pheromone, but the behavioral activity of DMD is low. In the present study, additional previously reported secondary metabolites (benzoquinones and hydrocarbons) were tested for electrophysiological activity (EAG) with both sexes of T. confusum. Two benzoquinones and three monoenic hydrocarbons elicited significant EAG activity from both male and female antennae. There was an elevated male EAG response (vs. the females) to two out of the three hydrocarbons and for both quinones. The EAG-active compounds were subsequently investigated for behavioral activity in a walking bioassay. Benzoquinones are considered toxic and have been assigned a function as alarm substances in flour beetles, but we found that methyl-1, 4-benzoquinone in intermediate concentrations was attractive to both male and female beetles and could therefore act as an aggregation pheromone component. Males were also attracted to ethyl-1,4-benzoquinone. The corresponding hydroquinones, presumed precursors of the benzoquinones, did not elicit any electrophysiological response and were not tested for behavioral activity. The unsaturated hydrocarbons (1-tetradecene, 1-pentadecene, and 1-hexadecene) elicited significant EAG responses from both male and female antennae and were also attractive in the behavioral assay. Our results show that several beetle-produced compounds, in addition to 4,8-dimethyldecanal, may be part of a complex pheromone system in flour beetles and play a role in mediating aggregation in T. confusum.
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  • Resultat 1-5 av 5

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