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  • 251.
    Olsman, Helena
    et al.
    Örebro University, Department of Natural Sciences.
    Hollert, Henner
    Kammann, Ulrike
    Klempt, Martin
    Otte, Jens
    van Bavel, Bert
    Örebro University, Department of Natural Sciences.
    Engwall, Magnus
    Örebro University, Department of Natural Sciences.
    Differences in Ah receptor mediated response for eighteen polybrominated and mixed halogenated dibenzo-p-dioxins and -furans in cell lines from four different speciesManuscript (Other academic)
  • 252.
    Olsman, Helena
    et al.
    Örebro University, Department of Natural Sciences.
    Schnurer, Anna
    Bjornfoth, Helen
    van Bavel, Bert
    Örebro University, Department of Natural Sciences.
    Engwall, Magnus
    Örebro University, Department of Natural Sciences.
    Fractionation and determination of Ah receptor (AhR) agonists in organic waste after anaerobic biodegradation and in batch experiments with PCB and decaBDE2007In: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499, Vol. 14, no 1, p. 36-43Article in journal (Refereed)
    Abstract [en]

    Goals, Scope and Background. Anaerobic digestion of organic household waste can lead to an increase in dioxin-like content, as determined by dioxin-specific bioassays. This may be a result of bioactivation of Ah receptor (AhR) agonists into more potent congeners. Work towards identifying the contributing compound groups is important in order to understand the mechanisms and to assess the relevance behind this increase in dioxin-like toxicity, since the residue can be used as a soil fertilising agent. The aim with the present work was to identify compound groups with AhR agonistic properties that caused the previously reported increase in dioxin-like activity after anaerobic biodegradation Methods. Firstly, chemical fractionation combined with dioxin bioassay testing was used to find bioactive classes of compounds. Secondly, batch digestion experiments with an externally added polychlorinated biphenyl (PCB) mixture (Clophen A50) and with decabrominated diphenyl ether (decaBDE), respectively, were studied as a possible process for transformation of precursors into more potent, dioxin-like compounds. Mesophilic (37 degrees C) and thermophilic (55 degrees C) anaerobic digestion were studied. Two different dioxin-specific bioassays were used to analyse AhR agonists in the biodegraded material, the CELCAD and the DR-CALUX. Results and Discussion. AhR agonist activity was detected in both di- and polyaromatic fractions of digestate extracts, which indicated that a diverse mixture of compounds contributed to the bioassay responses. No quantifiable activities were induced by the monoaromatic fractions. Further fractionation based on planarity revealed higher concentrations of AhR agonists than what was detected after the first fractionation, probably due to non-additive biological interactions of compounds in the extract that were removed in the second fractionation. These results showed significant activity in the non-planar diaromatic fractions and in the coplanar fractions of both diaromates and polyaromates. In the batch experiment with externally added PCB, an increase in dioxin-like activity was seen after 21 days of digestion at mesophilic conditions. After completed digestion, the content of AhR agonists was equal to the start concentration. PCB analysis with GC-MS indicated that dehalogenation of PCBs occurred in the digestors. The batch experiment with decaBDE showed no significant changes in TEQ-concentrations over time. Conclusions. The results show that the previously reported increase of AhR agonists during mesophilic anaerobic digestion is probably due to an accumulation of several different groups of AhR agonists, both diaromatic and polyaromatic, and both coplanar and non-planar. Batch experiments with externally added PCBs and decaBDE, respectively, did not result in any accumulation of AhR agonist activity after completed digestion, even though chemical analysis indicate a dechlorination of PCBs. Complex, unfractionated extracts were difficult to test using the bioassay approach. Removal of AhR antagonists or otherwise interacting compounds during fractionation may yield bio-TEQ values that are much higher than in the original extract. Recommendations and Perspectives. Our results indicate that the environmental risk that AhR agonists may pose concerning largescale anaerobic digestion of organic household waste probably depends on the efficiency of the digester and the sludge residence time. in order to obtain reliable results with the bioassays, an extensive cleanup and fractionation procedure is necessary. Without clean up and fractionation, there is a risk for false negatives and misleading conclusions. DR-CALUX and CELCAD were both suitable for these kinds of studies, provided that suitable fractionation methods are used.

  • 253.
    Olsman, Helena
    et al.
    Örebro University, Department of Natural Sciences.
    Schnürer, Anna
    Björnfoth, Helén
    Örebro University, Department of Natural Sciences.
    van Bavel, Bert
    Örebro University, Department of Natural Sciences.
    Engwall, Magnus
    Örebro University, Department of Natural Sciences.
    Fractionation and determination of Ah receptor (AhR) agonists in organic waste after anaerobic biodegradation and in batch experiments with PCB and decaBDEManuscript (Other academic)
  • 254.
    Olsman, Helena
    et al.
    Örebro University, Department of Natural Sciences.
    van Bavel, Bert
    Örebro University, Department of Natural Sciences.
    Björnfoth, Helén
    Örebro University, Department of Natural Sciences.
    Hardell, Lennart
    Lindström, Gunilla
    Örebro University, Department of Natural Sciences.
    Engwall, Magnus
    Örebro University, Department of Natural Sciences.
    CALUX-TEQs, PCDD/F and PCB in SFE-extracts of human adipose tissue from breast cancer patientsManuscript (Other academic)
  • 255.
    Olsman, Helena
    et al.
    Örebro University, Department of Natural Sciences.
    van Bavel, Bert
    Örebro University, Department of Natural Sciences.
    Kalbin, Georgi
    Örebro University, Department of Natural Sciences.
    Pettersson, Anneli
    Örebro University, Department of Natural Sciences.
    Stenlund, Sara
    Örebro University, Department of Natural Sciences.
    Strid, Åke
    Örebro University, Department of Natural Sciences.
    Engwall, Magnus
    Örebro University, Department of Natural Sciences.
    Formation of dioxin-like compounds as photoproducts of decarbominated diphenyl ether (deBDE) during UV-irradiation2002In: Organohalogen Compounds, ISSN 1026-4892, Vol. 58, p. 41-44Article in journal (Refereed)
  • 256.
    Olsman [Takner], Helena
    et al.
    Örebro University, Department of Natural Sciences.
    Engwall, Magnus
    Örebro University, Department of Natural Sciences.
    Kammann, Ulrike
    Klempt, Martin
    Otte, Jens
    van Bavel, Bert
    Örebro University, Department of Natural Sciences.
    Hollert, Henner
    Relative differences in aryl hydrocarbon receptor-mediated response for 18 polybrominated and mixed halogenated dibenzo-p-dioxins and -furans in cell lines from four different species2007In: Environmental Toxicology and Chemistry, ISSN 0730-7268, E-ISSN 1552-8618, Vol. 26, no 11, p. 2448-2454Article in journal (Other academic)
    Abstract [en]

    As a consequence of ubiquitous use of brominated organic chemicals, there is a concern for persistent or increasing environmental levels of polybrominated dibenzo-p-dioxins/furans (PBDD/Fs) and mixed polychlorinated and polybrominated dibenzo-p-dioxins/furans (PXDD/Fs). Hence, there is a need to broaden the toxicological and environmental knowledge about these compounds, as a basis for risk assessment. In the study presented here, the relative potencies (REPs) for 18 PBDD/F and PXDD/ F congeners were determined in four dioxin-specific bioassays from different species: dioxin receptor chemically activated luciferase expression assay (DR-CALUX, rat hepatoma cells), TV101L (human hepatoma cells), and GPC.2D (guinea pig adenoma cells), as well as ethoxyresorufin-O-deethylase induction in the fish cell line RTL-W1 (rainbow trout liver cells). The bioassay specific REP factors presented here enable the assessment of the contribution from PBDD/Fs and PXDD/Fs to total 2,3,7,8-tetrachl orodibenzop-dioxin (TCDD) equivalents (TEQs: toxic equivalents), using bioassay analysis. The PBDD/Fs were found to be equally potent as their chlorinated analogues in the three mammalian assays, whereas the PXDD/Fs showed relatively higher potencies. Of special concern were the 2,3,7,8-substituted penta- and tetrahalogenated congeners, for which mean REPs were >= 1. The 2-B-1,3,7,8-CDD (2-bromo-1,3,7,8-tetrachlorodibenzo-p-dioxin) was up to three times more potent than TCDD in individual experiments (on weight basis). The RTL-W1 was less sensitive to the tested compounds with overall 10-fold lower REPs than the mammalian cell lines. Although the REP factors exhibited species-specific differences, overall resembling rank orders of dioxin-like potency were obtained.

  • 257.
    Olsson, Per-Erik
    et al.
    Örebro University, Department of Natural Sciences.
    Berg, A. Håkan
    von Hofsten, Jonas
    Grahn, Birgitta
    Hellqvist, Anna
    Larsson, Anders
    Örebro University, Department of Natural Sciences.
    Karlsson, Johnny
    Örebro University, Department of Natural Sciences.
    Modig, Carina
    Örebro University, Department of Natural Sciences.
    Borg, Bertil
    Thomas, Peter
    Molecular cloning and characterization of a nuclear androgen receptor activated by 11-ketotestosterone2005In: Reproductive biology and endocrinology, ISSN 1477-7827, Vol. 3:37Article in journal (Refereed)
    Abstract [en]

    Although 11-ketotestosterone is a potent androgen and induces male secondary sex characteristics in many teleosts, androgen receptors with high binding affinity for 11-ketotestosterone or preferential activation by 11-ketotestosterone have not been identified. So, the mechanism by which 11-ketotestosterone exhibits such high potency remains unclear. Recently we cloned the cDNA of an 11-ketotestosterone regulated protein, spiggin, from three-spined stickleback renal tissue. As spiggin is the only identified gene product regulated by 11-ketotestosterone, the stickleback kidney is ideal for determination of the mechanism of 11-ketotestosterone gene regulation. A single androgen receptor gene with two splicing variants, belonging to the androgen receptor-beta subfamily was cloned from stickleback kidney. A high affinity, saturable, single class of androgen specific binding sites, with the characteristics of an androgen receptor, was identified in renal cytosolic and nuclear fractions. Measurement of ligand binding moieties in the cytosolic and nuclear fractions as well as to the recombinant receptor revealed lower affinity for 11-ketotestosterone than for dihydrotestosterone. Treatment with different androgens did not up-regulate androgen receptor mRNA level or increase receptor abundance, suggesting that auto-regulation is not involved in differential ligand activation. However, comparison of the trans-activation potential of the stickleback androgen receptor with the human androgen receptor, in both human HepG2 cells and zebrafish ZFL cells, revealed preferential activation by 11-ketotestosterone of the stickleback receptor, but not of the human receptor. These findings demonstrate the presence of a receptor preferentially activated by 11-ketotestosterone in the three-spined stickleback, so far the only one known in any animal.

  • 258. Olsson, Susanna
    et al.
    Van Schaik, Joris W. J.
    Gustafsson, Jon Petter
    Kleja, Dan Berggreb
    van Hees, Patrick A. W.
    Örebro University, Department of Natural Sciences.
    Copper(II) binding to dissolved organic matter fractions in municipal solid waste incinerator bottom ash leachate2007In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 41, no 12, p. 4286-4291Article in journal (Refereed)
    Abstract [en]

    Information on Cu speciation in municipal solid waste incineration (MSWI) bottom ash leachate is needed for Cu leaching predictions and toxicity estimates. The complexation of Cu with dissolved organic matter (DOM) in leachates from a stored MSWI bottom ash was studied potentiometrically using a Cu-ion selective electrode. More than 95% of the copper was bound to DOM in the hydrophilic fraction of the leachate, indicating that the hydrophilic acids contribute to Cu complex formation. The hydrophilic acids constituted 58% of the dissolved organic carbon in the ash leachate. Comparisons between experimental results and speciation calculations with the NICA-Donnan model and the Stockholm humic model indicated differences between the ash DOM and the natural DOM for which the models have been calibrated. The ratio of carboxylic binding sites to phenolic binding sites was 2 times larger in ash DOM, and the Cu-binding affinity of the former was stronger than accounted for by the generic Cu-binding parameters. The Cu-binding affinity of the phenolic sites, on the other hand, was weaker. When these parameters were adjusted, a good description of the experimental data was obtained.

  • 259. Ostrakhovitch, Elena A.
    et al.
    Olsson, Per-Erik
    Örebro University, Department of Natural Sciences.
    Jiang, Sean
    Cherian, M. George
    Interaction of metallothionein with tumor suppressor p53 protein2006In: FEBS Letters, ISSN 0014-5793, E-ISSN 1873-3468, Vol. 580, no 5, p. 1235-1238Article in journal (Refereed)
    Abstract [en]

    Previous reports have shown that metallothionein (MT) may modulate p53 activity through zinc exchange. However, little is known on a direct interaction between MT and p53 in cells. The results demonstrate an interaction between MT and p53 can occur in vitro. The complex between MT and p53 was observed in breast cancer epithelial cells with both wild and inactive type of p53. Furthermore, it was shown that wt-p53 was preferentially associated with Apo-MT. Our data suggest that co-expression of MT and p53 and their complex formation in tumor cells may be involved in regulation of apoptosis in these cells.

  • 260. Otte, Jens C.
    et al.
    Andersson, Carin
    Abrahamson, Alexandra
    Olsman Takner, Helena
    Örebro University, Department of Natural Sciences.
    Keiter, Steffen
    Engwall, Magnus
    Örebro University, Department of Natural Sciences.
    Hollert, Henner
    Brunström, Björn
    A bioassay approach to determine the dioxin-like activity in sediment extracts from the Danube River: ethoxyresorufin-O-deethylase induction in gill filaments and liver of three-spined sticklebacks (Gasterosteus aculeatus L.)2008In: Environment International, ISSN 0160-4120, E-ISSN 1873-6750, Vol. 34, no 8, p. 1176-1184Article in journal (Refereed)
    Abstract [en]

    Sediment samples from the upper Danube River in Germany have previously been characterized as ecotoxicologically hazardous and contaminants in these sediments may contribute to the observed decline of fish populations in this river section. For the investigation of sediment toxicity there is a need for development, standardization and implementation of in vivo test systems using vertebrates. Therefore, the main objective of this study was to apply and evaluate a recently established fish gill EROD assay as a biomarker in sediment toxicity assessment by using extracts of well characterised sediment samples from the upper Danube River. This to our knowledge is the first application of this novel assay to sediment extracts. Sediments from four different sites along the upper Danube River were Soxhlet-extracted with acetone and dissolved in DMSO. Three-spined sticklebacks (Gasterosteus aculeatus L.) were exposed for 48 h to various concentrations of the extracts, to the positive control β-naphthoflavone or to the solvent. Measurements of EROD activity in gill filaments and liver microsomes followed the exposure. Concentration-dependent induction of EROD in both gill and liver was found for all sediment extracts. The highest EROD-inducing potency was determined for extracts of sediments from the sites “Öpfinger See” and “Sigmaringen” and the EROD activities in gill and liver correlated well. The results from the gill and liver assays were in accordance with in vitro results of previous investigations. The EROD activities measured in the present study corresponded with the concentrations of PAHs, PCBs and PCDD/Fs in the sediment samples derived in a previous study. The sticklebacks in this study were in the reproductive phase and a stronger EROD induction was obtained in the females than in the males. Implementation of the EROD assay in testing of sediment extracts gave highly reliable results which make this assay an ecotoxicologically relevant method for assessment of contamination with Ah receptor agonists in sediments.

  • 261.
    Ottosen, I. M,.
    et al.
    Danmarks tekn. högskola.
    Jensen, P. E.
    Danmarks tekn. högskola.
    Ribeiro, A.
    Allard, Bert
    Örebro University, Department of Natural Sciences.
    Electrolytic remediation of soil slurry: removal of Cu, Cr and As2008Conference paper (Refereed)
  • 262. Pavasars, Ivars
    et al.
    Hagberg, Jessika
    Örebro University, Department of Natural Sciences.
    Borén, Hans
    Allard, Bert
    Örebro University, Department of Natural Sciences.
    Alkaline degradation of cellulose: mechanisms and kinetics2003In: Journal of polymers and the environment, ISSN 1064-7546, E-ISSN 1572-8900, Vol. 11, no 2, p. 39-47Article in journal (Refereed)
    Abstract [en]

    Cellulose powder and softwood sawdust were subjected to alkaline degradation under conditions representative of a cementitious environment for periods of 7 and 3 years, respectively. During the first 3 years, sampling was frequent, and data on the degradation of cellulose and production of isosaccharinic acid was used for establishing long-term prediction models. Samples after an additional period of 4 years were compared to the predicted values. The total rate of degradation was measured as the increase in total organic carbon (TOC) in corresponding solutions. A previously published theoretical model of degradation kinetics gave a good approximation of the present experimental data. Peeling-off, stopping, and alkaline hydrolysis reaction rate constants were obtained as model parameters, and the results suggested that the transformation of the glucose end group is the rate-limiting step in the cellulose peeling-off reaction and also determines the pH dependence of that reaction. After 3 years, isosaccharinic (ISA) acid represented 70-85% of all degradation products as quantified by capillary zone electrophoresis. The long-term prediction model indicated that all of the cellulose would be degraded after only 150-550 years. The control sampling after 7 years points toward a lower degradation of cellulose and production of ISA than predicted by the model, reflecting either a degradation of ISA that was faster than the production or a termination of the ISA production.

  • 263. Persson, Jörgen
    et al.
    Högberg, Peter
    Ekblad, Alf
    Örebro University, Department of Natural Sciences.
    Högberg, Mona N.
    Nordgren, Anders
    Näsholm, Torgny
    Nitrogen acquisition from inorganic and organic sources by boreal forest plants in the field2003In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 137, no 2, p. 252-257Article in journal (Refereed)
    Abstract [en]

    A wide range of recent studies have indicated that organic nitrogen may be of great importance to plant nitrogen (N) nutrition. Most of these studies have, however, been conducted in laboratory settings, excluding important factors for actual plant uptake, such as competition, mycorrhizal associations and soil interactions. In order to accurately evaluate the importance of different N compounds to plant N nutrition, field studies are crucial. In this study, we investigated short- as well as long-term plant nitrogen uptake by Deschampsia flexuosa, Picea abies and Vaccinium myrtillus from 15NO3-, 15NH4+ and (U-13C, 15N) arginine, glycine or peptides. Root N uptake was analysed after 6 h and 64 days following injections. Our results show that all three species, irrespective of their type of associated mycorrhiza (arbuscular, ecto- or ericoid, respectively) rapidly acquired similar amounts of N from the entire range of added N sources. After 64 days, P. abies and V. myrtillus had acquired similar amounts of N from all N sources, while for D. flexuosa, the uptake from all N sources except ammonium was significantly lower than that from nitrate. Furthermore, soil analyses indicate that glycine was rapidly decarboxylated after injections, while other organic compounds exhibited slower turnover. In all, these results suggest that a wide range of N compounds may be of importance for the N nutrition of these boreal forest plants, and that the type of mycorrhiza may be of great importance for N scavenging, but less important to the N uptake capacity of plants.

  • 264.
    Persson, Martin
    et al.
    Örebro University, School of Science and Technology.
    Duckett, Tom
    Department of Computing and Informatics, University of Lincoln, Lincoln, UK.
    Lilienthal, Achim J.
    Örebro University, Department of Natural Sciences.
    Fusion of aerial images and sensor data from a ground vehicle for improved semantic mapping2008In: Robotics and Autonomous Systems, ISSN 0921-8890, E-ISSN 1872-793X, Vol. 56, no 6, p. 483-492Article in journal (Refereed)
    Abstract [en]

    This work investigates the use of semantic information to link ground level occupancy maps and aerial images. A ground level semantic map, which shows open ground and indicates the probability of cells being occupied by walls of buildings, is obtained by a mobile robot equipped with an omni-directional camera, GPS and a laser range finder. This semantic information is used for local and global segmentation of an aerial image. The result is a map where the semantic information has been extended beyond the range of the robot sensors and predicts where the mobile robot can find buildings and potentially driveable ground.

  • 265.
    Pettersson, Anneli
    et al.
    Örebro University, Department of Natural Sciences.
    van Bavel, Bert
    Örebro University, Department of Natural Sciences.
    Engwall, Magnus
    Örebro University, Department of Natural Sciences.
    Jimenez, Begoña
    Polybrominated diphenylethers and methoxylated tetrabromodiphenylethers in cetaceans from the Mediterranean Sea2004In: Archives of Environmental Contamination and Toxicology, ISSN 0090-4341, E-ISSN 1432-0703, Vol. 47, no 4, p. 542-550Article in journal (Refereed)
    Abstract [en]

    Eight tetrabrominated to hexabrominated diphenylethers were present at ppb levels in liver from cetaceans found stranded on the beaches of the Mediterranean Sea, Italy. The highest concentration was found in striped dolphin (sum polybrominated diphenyl ethers [PBDE] 8133 ng/g l.w.) and the lowest concentration in bottlenose dolphin (sum PBDE 66 ng/g lipid weight [l.w.]). The predominant congener in all samples was 2,2',4,4'-tetraBDE (PBDE # 47) followed by, in decreasing order, the pentaPBDE # 99 and 100 and the hexaPBDE # 154 and 153. In 12 of the 14 analyzed samples, 3 different methoxylated PBDEs (MeO-PBDE # 1, 2, and 3) were detected at semiquantitatively calculated concentration ranges of 2 to 14 ng/g l.w.; 5 to 167 ng/g l.w.; and 7 to 628 ng/g l.w., respectively. In addition, several unidentified bromine compounds were seen when screening the samples in negative-chemical ionization (NCI) mode monitoring m/z 79 and 81, which illustrates the importance of running both electron-impact ionization and NCI when analyzing environmental samples. Electron-impact ionization is more specific for monitoring the molecular ion compared with NCI, which might overestimate the concentration of certain PBDE congeners.

  • 266.
    Pettersson-Julander, Anneli
    et al.
    Örebro University, Department of Natural Sciences.
    van Bavel, Bert
    Örebro University, Department of Natural Sciences.
    Engwall, Magnus
    Örebro University, Department of Natural Sciences.
    Westberg, Håkan
    Personal air sampling and analysis of polybrominated diphenyl ethers and other bromine containing compounds at an electronic recycling facility in Sweden2004In: Journal of Environmental Monitoring, ISSN 1464-0325, E-ISSN 1464-0333, Vol. 6, no 11, p. 874-880Article in journal (Refereed)
    Abstract [en]

    Brominated flame retardants (BFRs) have been used extensively and are considered ubiquitous contaminants. To evaluate exposure to brominated flame retardants within an electronic recycling facility personal air monitoring was done during a two year period. A total of 22 polybrominated diphenyl ethers (PBDEs) and 2 other bromine containing organic compounds have been analysed and evaluated in 17 personal air samples. The most abundant congeners of PBDE was #209 (<0.7-61 ng m(-3)), #183 (<0.1-32 ng m(-3)) indicating the use of the commercial octaBDE mixture, followed by PBDE #99 and #47 (<1.3-25 and <0.9-16 ng m(-3), respectively). The second most abundant peak in the chromatogram from all samples was identified as 1,2-bis(2,4,6-tribromophenyxy)ethane (BTBPE) in the concentration range <0.6-39 ng m(-3) (semi-quantitatively calculated against PBDE #191). A second bromine containing compound was also detected, structurally similar to decabromodiphenyl ethane (DeBDethane), however no definite identification could be made. The air samples were also evaluated on a work exposure category basis. The workers represented three different categories: dismantlers, other workers and unexposed. There was a significant difference (p < 0.05 with the Mann-Whitney test) among the dismantlers and the unexposed categories for PBDE congeners #47, #100, #99, #154; #153, #183, #209 and BTBPE. Another observation was that the air concentrations of PBDEs and BTBPE in the breathing zone were negatively correlated (p < 0.05) to the amount of recycled material ( in kg). The present work shows that the exposure to brominated flame retardants varied within the electronic facility and that further research is needed to evaluate how the exposure differs with different products being dismantled as well as how the bioavailability of the different BFRs to humans is related to particle exposure.

  • 267. Polder, A.
    et al.
    Thomsen, C.
    Lindström, Gunilla
    Örebro University, Department of Natural Sciences.
    Loken, K. B.
    Skaare, J. U.
    Levels and temporal trends of chlorinated pesticides, polychlorinated biphenyls and brominated flame retardants in individual human breast milk samples from Northern and Southern Norway2008In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 73, no 1, p. 14-23Article in journal (Refereed)
    Abstract [en]

    Human breast milk samples from primipara women from Northern (Tromso) (N = 10) and Southern Nor way (Oslo) (N = 19) collected in 2000-2001 were analysed with respect to hexachlorobenzene (HCB) hexachlorocyclohexane (HCHs), chlordanes (CHLs), DDTs. mirex, toxaphenes (CHBs), polychlorinated biphenyls (PCBs), polybrominated diphenylethers (PBDEs) and hexabromocyclododecane (HBCD) CHBs, PBDEs and HBCD were only analysed in the Tromso samples. Sum-PCBs and sum-DDTs were the major organochlorines (OCs) (170 and 110 ng g(-1) lipid weight (lw), respectively). Other OCs were found in levels of approximately 10- to 300-fold lower than sum-PCBs. Overall, the concentrations of OCs followed the decreasing order of PCBs > DDTs > HCB > HCHs approximate to CHLs > CHBs > mirex. Concentrations of sum-HCHs were significantly higher in breast milk from Oslo compared to Tromso (p < 0.05). The PCE profile was dominated by PCB-153, -138 and - 180. The PBDE pattern was dominated by PBDE-47 and PBDE-153. The median level of sum-PBDEs was 4.1 ng g(-1) lw. PBDE-209 was detected in all analysed samples (median 0.13 ng g(-1) lw). The estimated daily intake (EDI) for the median (range) of Sum monoortho (mo) PCBS8 was 3.7 (1-9) pg TEQ kg(-1) body weight per day for breast fed infants in Norway. This exceeded the TDI by a factor of 1.8 (1-4) based only on intake of mono-ortho PCBs. The present study shows that concentrations of OCs in primipara breast milk have decreased 50-60% since 1991, and that this trend is continuing. (c) 2008 Elsevier Ltd. All rights reserved.

  • 268.
    Ristilä, Mikael
    Örebro University, Department of Natural Sciences.
    Vitamin B6 as a potential antioxidant: a study emanating from UV-B-stressed plants2006Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Increased influx of solar UV-B radiation (280-320 nm), due to a decreasing stratospheric ozone layer, impacts severely on plants. Some of the UV-B effects on plants are related to stress induced by produced reactive oxygen species (ROS). Pyridoxine (vitamin B6) has been reported to be a potential quencher of ROS.

    Previous studies have shown that the PDX1.3 gene (encoding a key enzyme in vitamin B6 biosynthesis) is up-regulated by UV-B. We showed that this up-regulation also occurs at the protein level in UV-B exposed Col-0 wild-type plants. Studies performed using pdx1 knock-out mutants of Arabidopsis thaliana showed elevated transcripts levels for LHCB1*3 and PR-5 compared with the Col-0 wild-type. The pdx1 knock-out mutants showed an increased sensitivity towards H2O2-stress, but no increased sensitivity towards low dose UV-B-stress.

    To study the postulated role of pyridoxine as quencher of ROS in more detail, both theoretical and experimental studies were performed. Theoretical and experimental UV absorption spectra obtained at different protonation/deprotonation states of pyridoxine showed a very close resemblance at low and high pH. However, for the computational studies at physiological pH addition of counterions were required to accurately describe the experimental spectra.

    When theoretically studying the reactivity of pyridoxine towards three different ROS, .OH, .OOH and .O2-, the hydroxyl radical (.OH) was shown to be the most reactive species, while the superoxide radical (.O2-) showed no reactivity towards pyridoxine.

    In order to study the role of G-proteins in UV-B signal transduction pathways, UV-B irradiated G-protein mutants of Arabidopsis thaliana were studied. The regulation of the PDX1.3 gene was not affected in the G-protein mutants, regardless of the developmental stage of the plant. However, the expression of CHS was affected in the Ga subunit mutants.

    List of papers
    1. The role of the pyridoxine (vitamin B6) biosynthesis enzyme PDX1 in ultraviolet-B radiation responses in plants
    Open this publication in new window or tab >>The role of the pyridoxine (vitamin B6) biosynthesis enzyme PDX1 in ultraviolet-B radiation responses in plants
    Show others...
    2011 (English)In: Plant physiology and biochemistry (Paris), ISSN 0981-9428, E-ISSN 1873-2690, Vol. 49, no 3, p. 284-292Article in journal (Refereed) Published
    Abstract [en]

    Ultraviolet-B radiation regulates plant growth and morphology at low and ambient fluence rates but can severely impact on plants at higher doses. Some plant UV-B responses are related to the formation of reactive oxygen species (ROS) and pyridoxine (vitamin B6) has been reported to be a quencher of ROS. UV-B irradiation of Arabidopsis Col-0 plants resulted in increased levels of PDX1 protein, compared with UV-A-exposed plants. This was shown by immunoblot analysis using specific polyclonal antibodies raised against the recombinant PDX1.3 protein and confirmed by mass spectrometry analysis of immunoprecipitated PDX1. The protein was located mainly in the cytosol but also to a small extent in the membrane fraction of plant leaves. Immunohistochemical analysis performed in pea revealed that PDX1 is present in UV-B-exposed leaf mesophyll and palisade parenchyma but not in epidermal cells. Pyridoxine production increased in Col-0 plants exposed to 3 days of UV-B, whereas in an Arabidopsis pdx1.3 mutant UV-B did not induce pyridoxine biosynthesis. In gene expression studies performed after UV-B exposure, the pdx1.3 mutant showed elevated transcript levels for the LHCB1*3 gene (encoding a chlorophyll a/b-binding protein of the photosystem II light-harvesting antenna complex) and the pathogenesis-related protein 5 (PR-5) gene, compared with wild type.

    Place, publisher, year, edition, pages
    Amsterdam: Elsevier, 2011
    National Category
    Biochemistry and Molecular Biology
    Research subject
    Biochemistry
    Identifiers
    urn:nbn:se:oru:diva-3111 (URN)10.1016/j.plaphy.2011.01.003 (DOI)000288777300008 ()21288732 (PubMedID)2-s2.0-79951683043 (Scopus ID)
    Note

    This is a pre-print article

    Available from: 2012-08-07 Created: 2006-09-21 Last updated: 2018-05-02Bibliographically approved
    2. pH-dependent electronic and spectroscopic properties of pyridoxine (vitamin B6)
    Open this publication in new window or tab >>pH-dependent electronic and spectroscopic properties of pyridoxine (vitamin B6)
    2006 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 110, no 33, p. 16774-16780Article in journal (Refereed) Published
    Abstract [en]

    The key electronic and spectroscopic properties of vitamin B6 (pyridoxine) and some of its main charged and protonated/deprotonated species are explored using hybrid density functional theory (DFT) methods including polarized solvation models. It is found that the dominant species at low pH is the N1-protonated form and, at high pH, the O3¢-deprotonated compound. Computed and experimental UV-spectra for these species (experimental spectra recorded at pH 1.7 and 11.1, respectively) show a very close resemblance. At pH 4.3, the protonated species dominates, but with onset of the zwitterionic oxo form which is also the dominant species at neutral pH. The computational studies furthermore show that neither a polarized continuum model of the polar aqueous solvent or explicit hydrogen bonding through additional water molecules are sufficient to describe accurately the spectrum at physiological pH. Instead, Na+ and Cl- counterions were required to give a blue-shift of approximately 0.15 eV.

    Keywords
    Electrons, Hydrogen-Ion Concentration, Molecular Structure, Pyridoxine/*chemistry, Quantum Theory, Solvents/chemistry, Spectrum Analysis, Thermodynamics, Vitamin B 6/*chemistry, Vitamin B Complex/chemistry, Water/chemistry
    National Category
    Chemical Sciences
    Research subject
    Chemistry
    Identifiers
    urn:nbn:se:oru:diva-3112 (URN)10.1021/jp062800n (DOI)
    Available from: 2006-09-21 Created: 2006-09-21 Last updated: 2017-12-14Bibliographically approved
    3. Theoretical study of the antioxidant properties of pyridoxine
    Open this publication in new window or tab >>Theoretical study of the antioxidant properties of pyridoxine
    2006 (English)In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 110, no 48, p. 13068-13072Article in journal (Refereed) Published
    Abstract [en]

    Molecules acting as antioxidants capable of scavenging reactive oxygen species (ROS) are of utmost importance in the living cell. The antioxidative properties of pyridoxine (vitamin B6) have recently been discovered. In this study, we have analyzed the reactivity of pyridoxine toward the ROS .OH, .OOH, and .O2- at the density functional theory level (functionals B3LYP and MPW1B95). Two reaction types have been studied as follows: addition to the aromatic ring atoms and hydrogen/proton abstraction. Our results show that .OH is the most reactive species, while .OOH displays low reactivity and .O2- does not react at all with pyridoxine. The most exergonic reactions are those where .H is removed from the CH2OH groups or the ring-bound OH group and range from -33 to -39 kcal/mol. The most exergonic addition reactions occur by attacking the carbon atoms bonded to nitrogen but with an energy gain of only 6 kcal/mol.

    Place, publisher, year, edition, pages
    Washington, DC: American Chemical Society, 2006
    National Category
    Natural Sciences Chemical Sciences
    Research subject
    Chemistry
    Identifiers
    urn:nbn:se:oru:diva-3113 (URN)10.1021/jp065115p (DOI)17134167 (PubMedID)
    Available from: 2006-09-21 Created: 2006-09-21 Last updated: 2017-12-14Bibliographically approved
    4. The role of heterotrimeric G-proteins in ultraviolet-B-stress in Arabidopsis thaliana
    Open this publication in new window or tab >>The role of heterotrimeric G-proteins in ultraviolet-B-stress in Arabidopsis thaliana
    (English)Manuscript (Other academic)
    National Category
    Chemical Sciences
    Research subject
    Chemistry
    Identifiers
    urn:nbn:se:oru:diva-3114 (URN)
    Available from: 2006-09-21 Created: 2006-09-21 Last updated: 2017-10-18Bibliographically approved
  • 269.
    Ristilä, Mikael
    et al.
    Örebro University, Department of Natural Sciences.
    Kalbina, Irina
    Örebro University, Department of Natural Sciences.
    Strid, Åke
    Örebro University, Department of Natural Sciences.
    The role of heterotrimeric G-proteins in ultraviolet-B-stress in Arabidopsis thalianaManuscript (Other academic)
  • 270.
    Ristilä, Mikael
    et al.
    Örebro University, Department of Natural Sciences.
    Matxain, Jon M.
    Strid, Åke
    Örebro University, Department of Natural Sciences.
    Eriksson, Leif A.
    Örebro University, Department of Natural Sciences.
    pH-dependent electronic and spectroscopic properties of pyridoxine (vitamin B6)2006In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 110, no 33, p. 16774-16780Article in journal (Refereed)
    Abstract [en]

    The key electronic and spectroscopic properties of vitamin B6 (pyridoxine) and some of its main charged and protonated/deprotonated species are explored using hybrid density functional theory (DFT) methods including polarized solvation models. It is found that the dominant species at low pH is the N1-protonated form and, at high pH, the O3¢-deprotonated compound. Computed and experimental UV-spectra for these species (experimental spectra recorded at pH 1.7 and 11.1, respectively) show a very close resemblance. At pH 4.3, the protonated species dominates, but with onset of the zwitterionic oxo form which is also the dominant species at neutral pH. The computational studies furthermore show that neither a polarized continuum model of the polar aqueous solvent or explicit hydrogen bonding through additional water molecules are sufficient to describe accurately the spectrum at physiological pH. Instead, Na+ and Cl- counterions were required to give a blue-shift of approximately 0.15 eV.

  • 271.
    Ristilä, Mikael
    et al.
    Örebro University, Department of Natural Sciences.
    Strid, Hilja
    Örebro University, School of Health and Medical Sciences.
    Eriksson, Leif A.
    National University of Ireland, Galway, Ireland.
    Strid, Åke
    Örebro University, Department of Natural Sciences.
    Sävenstrand, Helena
    Örebro University, School of Science and Technology.
    The role of the pyridoxine (vitamin B6) biosynthesis enzyme PDX1 in ultraviolet-B radiation responses in plants2011In: Plant physiology and biochemistry (Paris), ISSN 0981-9428, E-ISSN 1873-2690, Vol. 49, no 3, p. 284-292Article in journal (Refereed)
    Abstract [en]

    Ultraviolet-B radiation regulates plant growth and morphology at low and ambient fluence rates but can severely impact on plants at higher doses. Some plant UV-B responses are related to the formation of reactive oxygen species (ROS) and pyridoxine (vitamin B6) has been reported to be a quencher of ROS. UV-B irradiation of Arabidopsis Col-0 plants resulted in increased levels of PDX1 protein, compared with UV-A-exposed plants. This was shown by immunoblot analysis using specific polyclonal antibodies raised against the recombinant PDX1.3 protein and confirmed by mass spectrometry analysis of immunoprecipitated PDX1. The protein was located mainly in the cytosol but also to a small extent in the membrane fraction of plant leaves. Immunohistochemical analysis performed in pea revealed that PDX1 is present in UV-B-exposed leaf mesophyll and palisade parenchyma but not in epidermal cells. Pyridoxine production increased in Col-0 plants exposed to 3 days of UV-B, whereas in an Arabidopsis pdx1.3 mutant UV-B did not induce pyridoxine biosynthesis. In gene expression studies performed after UV-B exposure, the pdx1.3 mutant showed elevated transcript levels for the LHCB1*3 gene (encoding a chlorophyll a/b-binding protein of the photosystem II light-harvesting antenna complex) and the pathogenesis-related protein 5 (PR-5) gene, compared with wild type.

  • 272. Rosling, A.
    et al.
    Suttle, K. B.
    Johansson, E.
    van Hees, Patrick A. W.
    Örebro University, Department of Natural Sciences.
    Banfield, J. F.
    Phosphorous availability influences the dissolution of apatite by soil fungi2007In: Geobiology, ISSN 1472-4677, E-ISSN 1472-4669, Vol. 5, no 3, p. 265-280Article in journal (Refereed)
    Abstract [en]

    Apatite (Ca-10(PO4)(6)(OH,F,Cl)(2)) is the primary inorganic source of phosphorus in the biosphere. Soil fungi are known to increase plant-available phosphorus by promoting dissolution of various phosphate minerals. Yet no apatite dissolution studies exist using fungi as weathering agents, and regulation of fungal weathering activity in response to different levels of phosphorus availability is largely unknown. Fungi were isolated from a grassland soil in northern California. Three pathways of tri-calcium phosphate (Ca-3(PO4)(2)) (TCP) dissolution in liquid culture were identified among biogeochemically active fungi: (1) acidification (pH 3.3 +/- 0.16), (2) moderate acidification (pH 4.9 +/- 0.11) and (3) no acidification. Isolates representing pathway 1 and 2 were Zygomycetes in the order of Mucorales. All non-acidifying isolates in pathway 3 were Ascomycetes and cleared the media by altering TCP into hydroxyapatite (Ca-10(PO4)(6)(OH)(2)) and sequestering it within mycelial spheres. One isolate representing each pathway was used in fluorapatite dissolution experiments either with the fungi present or under abiotic conditions using cell-free liquid media conditioned by fungal growth at different phosphorus and calcium availabilities. Both Mucorales isolates acidify their substrate when growing in the presence of phosphorus. Mucorales exudates were mainly oxalic acid, and conditioned cell-free media with phosphorus induced fluorapatite dissolution at a rate of 10(-0.9 +/- 0.14) and 10(-1.2 +/- 0.22) mu mol P m(-2) s(-1). The ascomycete isolate on the other hand, induced fluorapatite dissolution at a rate of 10(-1.1 +/- 0.05) mu mol P m(-2) s(-1) by lowering the pH of the media under phosphorus-limited conditions, without producing significant amounts of low molecular weight organic acids (LMWOAs). Oxalate strongly etches fluorapatite along channels parallel to [001], forming needle-like features, while exudates from the ascomycete-induced surface rounding. We conclude that while LMWOAs are well-studied weathering agents, these do not appear to be produced by fungi in response to phosphorus-limiting growth conditions.

  • 273. Routti, H.
    et al.
    Letcher, R. J.
    Arukwe, A.
    van Bavel, Bert
    Örebro University, Department of Natural Sciences.
    Yoccoz, N. G.
    Chu, S.
    Gabrielsen, G. W.
    Biotransformation of PCBs in relation to phase I and II xenobiotic-metabolizing enzyme activities in ringed seals (Phoca hispida) from Svalbard and the Baltic Sea2008In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 42, no 23, p. 8952-8958Article in journal (Refereed)
    Abstract [en]

    Polychlorinated biphenyls (PCBs) may induce activity of hepatic enzymes, mainly Phase I monooxygenases and conjugating Phase II enzymes, that catalyze the metabolism of PCBs leading to formation of metabolites and to potential adverse health effects. The present study investigates the concentration and pattern of PCBs, the induction of hepatic phase I and II enzymes, and the formation of hydroxy (OH) and methylsulfonyl (CH3SO 2=MeSO2) PCB metabolites in two ringed seal (Phoca hispida) populations, which are contrasted by the degree of contamination exposure, that is, highly contaminated Baltic Sea (n = 31) and less contaminated Svalbard (n = 21). Phase I enzymes were measured as ethoxyresorufin-O- deethylation (EROD), benzyloxyresorufin-O-dealkylation (BROD), methoxyresorufin-O-demethylation (MROD), and pentoxyresorufin-O-dealkylation (PROD) activities, and phase II enzymes were measured as uridine diphosphophate glucuronosyl transferase (UDPGT) and glutathione-S-transferase (GST). Geographical comparison, multivariate, and correlation analysis indicated that Σ-PCB had a positive impact on Phase I enzyme and GST activities leading to biotransformation of group III (vicinal ortho-meta-H atoms and ≀1 ortho-chlorine (Cl)) and IV PCBs (vicinal meta-para-H atoms and ≀2 ortho-Cl). The potential precursors for the main OH-PCBs detected in plasma in the Baltic seals were group III PCBs. MeSO2-PCBs detected in liver were mainly products of group IV PCB metabolism. Both CYP1A- and CYP2B-like enzymes are suggested to be involved in the PCB biotransformation in ringed seals. © 2008 American Chemical Society.

  • 274.
    Saenz-Mendez, Patricia
    et al.
    Örebro University, Department of Natural Sciences.
    Guedes, Rita C.
    dos Santos, Daniel J.V.A.
    Eriksson, Leif A.
    Örebro University, Department of Natural Sciences.
    Theoretical prediction of binding modes and hot sequences for allopsoralen-DNA interaction2007In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 450, no 1-3, p. 127-131Article in journal (Refereed)
    Abstract [en]

    Molecular docking studies of two duplex DNA sequences as target fragments and allopsoralen as ligand were performed. The calculated interaction energies showed that the ligand can be docked into the minor groove as well as become intercalated. However, unlike psoralen, allopsoralen preferred binding mode for non-poly-TA sequences is minor groove binding. Calculated energies for intercalation between different base pairs suggest that the predicted sequence selectivity for allopsoralen is analogous to that observed for psoralen. Intercalation is favored in 5'-TpA sites in poly-TA sequences.

  • 275.
    Saenz-Mendez, Patricia
    et al.
    Örebro University, Department of Natural Sciences.
    Guedes, Rita C.
    dos Santos, Daniel J.V.A.
    Eriksson, Leif A.
    Örebro University, Department of Natural Sciences.
    Theoretical study of sequence selectivity and preferred binding mode of psoralen with DNA2007In: Research Letters in Physical Chemistry, ISSN 1687-6873, p. Article number 60623-Article in journal (Refereed)
    Abstract [en]

    Psoralen interaction with two models of DNA was investigated using molecular mechanics and molecular dynamics methods. Calculated energies of minor groove binding and intercalation were compared in order to define a preferred binding mode for the ligand.We found that both binding modes are possible, explaining the low efficiency for monoadduct formation from intercalated ligands. A comparison between the interaction energy for intercalation between different base pairs suggests that the observed sequence selectivity is due to favorable intercalation in 5'-TpA in (AT)n sequences.

  • 276.
    Sakic, Azra
    Örebro University, Department of Natural Sciences.
    Solsystemet2008Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The view of how the Earth and the Sun move has changed through the ages. The idea that was “right", from the time of ancient Greece, was that the Earth was at the centre and everything revolved around it even if some facts were unexplained. It was in the middle of the 1500s that Copernicus developed the idea that Sun was in the centre and the Earth revolved around it. His theory was controversial, especially since it did not improve the positions of the planets very much.

    The person who provided the necessary data was Tycho Brahe. In the late 1500s he observed and logged the planetary positions for many years, using his own instruments on the island of Ven. His assistant Johannes Kepler then used the data to infer his three famous laws of planetary motion. Kepler could not explain why the planets moved according to the laws, since the latter were empirical. Isaac Newton could later on derive Kepler’s laws from his own gravitational law and three laws of motion, thereby confirming Kepler’s result. Newton also provided a great synthesis between local physics (the famous apple falling down) and celestial motion.

    This report will discuss the Kepler and Newton laws in more detail, as well as the modern view of the dynamics and structure of the solar system.

  • 277. Salih, Isam
    et al.
    Bäckström, Mattias
    Örebro University, Department of Natural Sciences.
    Karlsson, Stefan
    Örebro University, Department of Natural Sciences.
    Lund, Eva
    Pettersson, Håkan B. L.
    Impact of fluoride and other aquatic parameters on radon concentration in natural waters2004In: Applied Radiation and Isotopes, ISSN 0969-8043, E-ISSN 1872-9800, Vol. 60, no 1, p. 99-104Article in journal (Refereed)
    Abstract [en]

    Radon (222Rn) accumulation in water in relation to stable elements was studied for the purpose of determining factors influencing the transfer of 222Rn to and from water. In 72 groundwater samples, 222Rn and about 70 analytical parameters were analysed using radiometric and ICP-MS techniques. Using multivariate statistics (partial least squares), it was observed that 222Rn has a positive correlation with fluoride and uranium. The correlation with fluoride was further investigated by a laboratory time-scale experiment to measure the emanation of 222Rn from water as a function of fluoride, pH and carbonate. The transfer of 222Rn from water was measured by continuous monitoring in air in a closed loop set-up. It was observed that fluoride in water adhere or trap 222Rn preferably in acidic water (pH 3). It is suspected that natural physical processes (such as diffusion and microbubble phenomenon) are less effective to transport 222Rn in the presence of fluoride.

  • 278.
    Sandstrom, Ulf G.
    et al.
    Örebro University, Department of Natural Sciences.
    Angelstam, Per
    Mikusinski, Grzegorz
    Ecological diversity of birds in relation to the structure of urban green space2006In: Landscape and Urban Planning, ISSN 0169-2046, E-ISSN 1872-6062, Vol. 77, no 1-2, p. 39-53Article in journal (Refereed)
    Abstract [en]

    A functional network of green space is important for the maintenance of the ecological dimension of a sustainable urban landscape. We used avian ecological diversity as a proxy for evaluating the functionality of different types of urban green space. The urban landscape of the municipality of Orebro in Sweden was stratified into four strata (City centre, Residential, Greenway and Periphery). Bird species found in these strata were classified into four ecological groups with decreasing degree of specialisation (woodpeckers, hole-nesters, forest birds and urban birds). Overall there was lower bird species richness in the City centre and Residential areas compared to the Greenway and Periphery. Woodpeckers, hole-nesters and forest birds showed an increasing trend in the number of species as well as individuals from the City centre to the Periphery while urban birds showed the opposite trend. The amount and quality of green space as well as natural vegetation increased from the City centre to the Periphery. Species richness of woodpeckers, forest birds and hole-nesters were positively correlated with tree density while urban birds showed an inverse correlation. There was no dead wood in City centre, Residential and Greenway in contrast to the Periphery, which held some dying trees, stumps and old windthrows. Our findings emphasise the importance of urban green space with natural structures to maintain high ecological diversity. Finally, we discuss how conflicts between habitat for biodiversity maintenance and other functions of green space could be handled by zoning. (c) 2005 Elsevier B.V. All rights reserved.

  • 279.
    Sandström, Ulf
    Örebro University, Department of Natural Sciences.
    Enhanced predation rates on cavity bird nests at deciduous forest edges: an experimental study1991In: Ornis Fennica, ISSN 0030-5685, Vol. 68, no 3, p. 93-98Article in journal (Refereed)
    Abstract [en]

    The size of a forest tract influences the composition of the fauna. If forests become fragmented this will affect the fauna in several ways. One of the main effects is enhanced nest predation. Several studies which confirm this effect have been carried out, but none has used natural cavities. I tested experimentally whether the predation rate was higher in natural tree-holes close to the forest/farmland edge than in the interior of the wood. In a fragmented deciduous forest, fresh Quail eggs were placed in natural cavities at various distances from the edge. The eggs were exposed during a period corresponding in length to the egg and nestling period of a hole-nesting bird. In the beginning of the period, the predation rate was higher close to the edge (< 20 m) than further inside the wood. This result may indicate that a predator first searches the ecotone and afterwards penetrates deeper inside the forest. The results is in accord with earliest observations than nests in natural cavities seem to be less vulnerable than other types of nests.

  • 280.
    Sandström, Ulf G.
    Örebro University, Department of Natural Sciences.
    Biodiversity and green infrastructure in urban landscapes2004Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this thesis, I evaluate the extent to which biodiversity is affected, and taken into consideration by, urban planning. Based on landscape ecology, I apply an interdisciplinary approach. In addition to natural science, I have included social and political sciences, as methods from these two disciplines were required to study issues dealing with both biodiversity and urban planning.

    Urbanisation affects biodiversity in several ways. For example, changes in vegetation structures as well as an increased fragmentation of natural habitats will take place. In a fragmented environment an increased nest predation rate occurs. In the smaller spatial scale, predation rate was found to be higher closer to the edge of natural habitat patches than further inside. I also carried out research in order to identify the local and regional effects that cities have on compositional and structural elements of biodiversity. The amount and quality of green space and natural vegetation increased from the centre to the periphery of the city. Avian species richness showed the same trend with the exception of avian generalists, which showed the opposite trend. Certain qualities such as old-growth trees and dead wood, as well as availability of green space, were identified as being important for avian diversity. These findings emphasise the importance of urban green space with natural structures to maintain high ecological diversity.

    Based on analyses of policy documents, I examined whether Swedish local authorities and planners take urban green spaces into consideration as potential multifunctional systems, including the maintenance of biodiversity. The result showed that Swedish planners and local decision-makers have not fully understood the multiple uses of urban green space, for example, the same area can act as a recreation area, improve the local climate, and maintain biodiversity.

    A normative model for conservation planning in urban landscapes was defined and operationalised by using landscape ecological principles. Urban planners were interviewed about their interest, ability, and knowledge with respect to planning for functional networks of green spaces in relation to the normative model. The unanimous view was that planners were interested in the concept of biodiversity. However, they were restricted by the extent of their knowledge, by personnel lacking suitable qualifications, and by inadequacies within their organisations. To deal with this, better integration of natural, social, and political sciences in education, as well as policy implementation should be developed.

    List of papers
    1. Availability and use of natural tree holes by cavity nesting birds in a Swedish deciduous forest
    Open this publication in new window or tab >>Availability and use of natural tree holes by cavity nesting birds in a Swedish deciduous forest
    1998 (English)In: Ardea, ISSN 0373-2266, E-ISSN 2213-1175, Vol. 86, no 1, p. 109-119Article in journal (Refereed) Published
    Abstract [en]

    Cavities in trees are an important resource as nest sites or shelter for many birds and mammals. The aim of this study was to quantify the density of cavities, their characteristics, and their origin, and the implication these have on nest site choice by hole-nesting birds. The study was carried out in a deciduous forest in south central Sweden during two years. The forest was dominated by Pendunculate Oak Quercus robur, Norway Maple Acer plantanoides, Small-leaved Lime Tilia cordata, Rowan Sorbus aucuparia, birch Betula pubescens/verrucosa and Aspen Populus tremula, in decreasing order of abundance. We found an average cavity density of 60.4 ha-1. Limb holes were the most abundant type found (53%) and were also most frequently used by hole-nesting birds (64.8%). Pendunculate Oak and Aspen were the two tree species richest in cavities. Limb holes dominated in Pendunculate Oak while woodpecker-excavated holes dominated in aspen. Cavities with occupied bird nests had narrower entrances, were located higher up, had smaller volumes, thicker walls and a smaller circumference of the stem at the hole compared with unoccupied cavities. Limb holes, woodpecker holes and other hole types were used as nest sites by birds in proportion to their frequency of occurrence in the forest. Each year only 5-10% of available cavities attracted breeding birds. The most salient features that emerge from these results are the high density of cavities and their low occupancy rate.

    National Category
    Biological Sciences
    Research subject
    Biologi med ekologisk inriktning
    Identifiers
    urn:nbn:se:oru:diva-3138 (URN)
    Available from: 2004-05-07 Created: 2004-05-07 Last updated: 2017-12-14Bibliographically approved
    2. Enhanced predation rates on cavity bird nests at deciduous forest edges: an experimental study
    Open this publication in new window or tab >>Enhanced predation rates on cavity bird nests at deciduous forest edges: an experimental study
    1991 (English)In: Ornis Fennica, ISSN 0030-5685, Vol. 68, no 3, p. 93-98Article in journal (Refereed) Published
    Abstract [en]

    The size of a forest tract influences the composition of the fauna. If forests become fragmented this will affect the fauna in several ways. One of the main effects is enhanced nest predation. Several studies which confirm this effect have been carried out, but none has used natural cavities. I tested experimentally whether the predation rate was higher in natural tree-holes close to the forest/farmland edge than in the interior of the wood. In a fragmented deciduous forest, fresh Quail eggs were placed in natural cavities at various distances from the edge. The eggs were exposed during a period corresponding in length to the egg and nestling period of a hole-nesting bird. In the beginning of the period, the predation rate was higher close to the edge (< 20 m) than further inside the wood. This result may indicate that a predator first searches the ecotone and afterwards penetrates deeper inside the forest. The results is in accord with earliest observations than nests in natural cavities seem to be less vulnerable than other types of nests.

    National Category
    Biological Sciences
    Research subject
    Biologi med ekologisk inriktning
    Identifiers
    urn:nbn:se:oru:diva-3139 (URN)
    Available from: 2004-05-07 Created: 2004-05-07 Last updated: 2017-12-14Bibliographically approved
    3. Ecological diversity of birds and the quality of urban green space
    Open this publication in new window or tab >>Ecological diversity of birds and the quality of urban green space
    (English)Manuscript (preprint) (Other academic)
    National Category
    Biological Sciences
    Research subject
    Biology
    Identifiers
    urn:nbn:se:oru:diva-3140 (URN)
    Available from: 2004-05-07 Created: 2004-05-07 Last updated: 2017-10-18Bibliographically approved
    4. Green infrastructure planning in urban Sweden
    Open this publication in new window or tab >>Green infrastructure planning in urban Sweden
    2002 (English)In: Planning practice + research, ISSN 0269-7459, E-ISSN 1360-0583, Vol. 17, no 4, p. 373-385Article in journal (Refereed) Published
    National Category
    Biological Sciences
    Research subject
    Biologi med ekologisk inriktning
    Identifiers
    urn:nbn:se:oru:diva-3141 (URN)10.1080/02697450216356 (DOI)
    Available from: 2004-05-07 Created: 2004-05-07 Last updated: 2017-12-14Bibliographically approved
    5. Urban comprehensive planning: identifying barriers for the maintenance of functional habitat networks
    Open this publication in new window or tab >>Urban comprehensive planning: identifying barriers for the maintenance of functional habitat networks
    2006 (English)In: Landscape and Urban Planning, ISSN 0169-2046, E-ISSN 1872-6062, Vol. 75, no 1-2, p. 43-57Article in journal (Refereed) Published
    Abstract [en]

    Maintaining biodiversity requires a wise combination of protection, management and recreation of habitats to secure representative and functional habitat networks. As urbanisation is increasing worldwide, town and cities are becoming the most common habitat for humankind. Accordingly, the urban landscape is becoming increasingly important for maintaining biodiversity on site, as well as for understanding the concept of biodiversity in general, and its maintenance in urban landscapes.

    We evaluated the extent to which Swedish urban planners experience barriers when using comprehensive planning as a tool for the maintenance of biodiversity through the provision of sufficient quantity and quality of green space. All of the six large Swedish cities, having had constant relative population growth since the beginning of the 19th century were chosen as case studies. We first defined a normative model for planning urban biodiversity and operationalised this concept by using landscape ecological principles. Structured in-depth interviews were then carried out with three planners in each city. The respondents were asked about their interest, ability, and knowledge concerning planning for functional networks of green spaces in relation to the normative model.

    The in-depth interviews with 18 urban planners indicated that legislation was an important driver for green space planning, that they paid attention to new knowledge concerning recreation values and public health, but that biodiversity maintenance was not a high priority. There was a general agreement that local governments lack necessary resources to plan for biodiversity. A majority of the respondents mentioned geographical information systems (GIS) as an important tool to integrate knowledge about biodiversity in the planning process, and to evaluate likely consequences caused by deviations from current structure plans related to an efficient use of urban green spaces to maintain biodiversity. However, an evaluation of the answers revealed that the respondents had actually overestimated their capacity to implement the normative model. To conclude, the unanimous view was that planners were interested in the maintenance of biodiversity, but were limited by knowledge and by personnel lacking suitable qualifications, as well as by inadequate organisations. Only a minority of the respondents thought that local governments should have resources for biodiversity conservation planning. Finally, we discuss how the implementation of biodiversity policies could be improved by better integration of natural and social sciences in education and policy implementation.

    National Category
    Biological Sciences
    Research subject
    Biology
    Identifiers
    urn:nbn:se:oru:diva-3142 (URN)10.1016/j.landurbplan.2004.11.016 (DOI)
    Available from: 2004-05-07 Created: 2004-05-07 Last updated: 2017-12-14Bibliographically approved
  • 281.
    Sandström, Ulf G.
    Örebro University, Department of Natural Sciences.
    Green infrastructure planning in urban Sweden2002In: Planning practice + research, ISSN 0269-7459, E-ISSN 1360-0583, Vol. 17, no 4, p. 373-385Article in journal (Refereed)
  • 282.
    Sandström, Ulf G.
    et al.
    Örebro University, Department of Natural Sciences.
    Angelstam, Per
    Khakee, Abdul
    Urban comprehensive planning: identifying barriers for the maintenance of functional habitat networks2006In: Landscape and Urban Planning, ISSN 0169-2046, E-ISSN 1872-6062, Vol. 75, no 1-2, p. 43-57Article in journal (Refereed)
    Abstract [en]

    Maintaining biodiversity requires a wise combination of protection, management and recreation of habitats to secure representative and functional habitat networks. As urbanisation is increasing worldwide, town and cities are becoming the most common habitat for humankind. Accordingly, the urban landscape is becoming increasingly important for maintaining biodiversity on site, as well as for understanding the concept of biodiversity in general, and its maintenance in urban landscapes.

    We evaluated the extent to which Swedish urban planners experience barriers when using comprehensive planning as a tool for the maintenance of biodiversity through the provision of sufficient quantity and quality of green space. All of the six large Swedish cities, having had constant relative population growth since the beginning of the 19th century were chosen as case studies. We first defined a normative model for planning urban biodiversity and operationalised this concept by using landscape ecological principles. Structured in-depth interviews were then carried out with three planners in each city. The respondents were asked about their interest, ability, and knowledge concerning planning for functional networks of green spaces in relation to the normative model.

    The in-depth interviews with 18 urban planners indicated that legislation was an important driver for green space planning, that they paid attention to new knowledge concerning recreation values and public health, but that biodiversity maintenance was not a high priority. There was a general agreement that local governments lack necessary resources to plan for biodiversity. A majority of the respondents mentioned geographical information systems (GIS) as an important tool to integrate knowledge about biodiversity in the planning process, and to evaluate likely consequences caused by deviations from current structure plans related to an efficient use of urban green spaces to maintain biodiversity. However, an evaluation of the answers revealed that the respondents had actually overestimated their capacity to implement the normative model. To conclude, the unanimous view was that planners were interested in the maintenance of biodiversity, but were limited by knowledge and by personnel lacking suitable qualifications, as well as by inadequate organisations. Only a minority of the respondents thought that local governments should have resources for biodiversity conservation planning. Finally, we discuss how the implementation of biodiversity policies could be improved by better integration of natural and social sciences in education and policy implementation.

  • 283.
    Sandström, Ulf G.
    et al.
    Örebro University, Department of Natural Sciences.
    Angelstam, Per
    Mikusinski, Grzegorz
    Ecological diversity of birds and the quality of urban green spaceManuscript (preprint) (Other academic)
  • 284. Sartz, L.
    et al.
    Bäckström, Mattias
    Örebro University, Department of Natural Sciences.
    The behaviour of barium, strontium, aluminium, chromium and molybdenum when leaching fly ash with acid rock drainage2008In: ICAM 2008: Ninth international congress for applied mineralogy, 2008, p. 357-364Conference paper (Other academic)
    Abstract [en]

    Acid rock drainage (ARD), commonly found in vicinities of sulfidic mines, possess properties capable of widely affecting the surrounding environment by acidification and heavy metal pollution. In most ARD treatments, various alkaline sources are used to neutralise the acid produced. Utilisation of highly alkaline fly ashes instead of raw materials is a cost-effective alternative, which lately have become increasingly popular. In laboratory batch experiments, neutralising capacity of fly ash was studied during 20 days. ARD was added to the fly ash once a day, for each increment the liquid to solid ratio (L/S ratio) was increased. At an early stage of the experiment (day 6, L/S ratio 12), the concentration of barium in solution unexpectedly increased by a factor of 50 (from 200 to 10 000 Όg·1-1). This high concentration also sustained the following two days (L/S ratios 14 and 16) before dropping to the original level. pH showed a slight increase during these observations (pH 12.4-12.7). The phenomenon was also observed in a parallel and identical series. In addition to barium, aluminium and strontium clearly increased in the same manner, however not as much as barium. Furthermore, concentrations of chromium and molybdenum noticeably decreased at these distinct L/S ratios (12, 14 and 16). The behaviour of barium and subsequently strontium, aluminium, chromium and molybdenum is only partially understood. The decrease of chromium and molybdenum is suggested to be due to incorporation into the interlayer regions of hydrocalumite (Ca4Al2(OH)12(OH) 2·6H2O), replacing the hydroxide groups, which also explains the increase in pH. Moreover, the increase of barium, strontium and aluminium could be attributable to dissolution of the silicate mineral celsian (Ba,Sr(Al2Si2O8)). Alternatively, barium and strontium increase could be explained by dissolution of a Ba,Sr(SO 4)-solid solution and aluminium increase by dissolution of hydrocalumite or ettringite.

  • 285.
    Schellwat, Holger
    Örebro University, Department of Natural Sciences.
    A simple slide rule for finite fields2001In: The American mathematical monthly, ISSN 0002-9890, E-ISSN 1930-0972, Vol. 108, no 4, p. 358-360Article in journal (Refereed)
  • 286.
    Schellwat, Holger
    Örebro University, Department of Natural Sciences.
    Induced Cayley graphs and double covers1995In: Linear and multilinear algebra, ISSN 0308-1087, E-ISSN 1563-5139, Vol. 39, no 1-2, p. 161-164Article in journal (Refereed)
  • 287.
    Scherbak, Nikolai
    Örebro University, Department of Natural Sciences.
    Characterization of stress-inducible short-chain dehydrogenases/reductases (SDR) in plants: study of a novel small protein family from Pisum sativum (pea)2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In pea (Pisum sativum), the short-chain alcohol dehydrogenase-like protein (SAD) gene family consists of at least three members (SAD-A, -B, and -C). The SAD genes are transiently expressed in plants after short exposures to ultraviolet-B radiation, which in turn leads to formation of SAD protein in leaf and stem tissue upon prolonged irradiation. SAD gene expression is also seen as a result of wounding stress.

    The recombinant SAD-C protein (which was the most highly over-expressed isoform in Escherichia coli of the isoforms) was shown to be a tetramer that probably consists of a dimer of dimers and which possesses quinone-reducing capability. The enzyme shows approximately the same NADH- and NADPH-dependent activity with 2,5- and 2,6-dimethylbenzoquinone and menadione as substrates.

    Western blotting and immunohistochemistry (IHC) shows that the SAD protein is present to a smaller or larger extent in all the different pea tissues examined. Environmental stress such as UV-B radiation clearly increases the content of SAD in leaf and stem tissue but not in roots. This indicates that increased expression of the SAD genes, as a result of UV-B exposure, is limited to the exposed tissue. This is substantiated by the heterologous GUS expression from the pea SAD-C promoter in Arabidopsis during wounding. Only the wound site and the vicinal tissue show transcription from this promoter. In non-stressed tissue (as well as in UV-B-stressed leaves and stem), SAD predominantly occurred in epidermal or sub-epidermal cells as judged by IHC. The protoderm of the pea seed cotyledonary axis contains the most heavily stained cells. This indicates a possible role for the SAD protein in development as well as in protection against environmental stress. Also, discrete staining was obtained in particular cell types of the ovary.

    To be able to understand the biochemical and physiological role of the SAD enzyme, an in silico modeling study of the SAD protein structure was performed. The simulations of our SAD protein, as well as of related proteins with known crystal structure (3alfa,20beta-hydroxysteroid dehydrogenase and secoisolariciresinol dehydrogenase), allowed us to obtain an energy-minimized structure for the monomeric SAD as well as important data on the cofactor interaction in the active site.

    Crystallization of recombinant SAD-C has been performed. The needle-like crystals, which diffract to 3.5Å, contain probably eight monomers in the asymmetric unit, presumably containing a pair of tetramers.

    SAD enhances the reduction rates of quinones with NADH. However, NADH can also accomplish reduction of certain quinones non-enzymatically. Both theoretical calculations and experimental techniques were used to elucidate the structural and electronic pre-requisites for this non-enzymatic quinone reduction.

    List of papers
    1. Plant SAD proteins: characterization of the tetrameric Pisum sativum protein
    Open this publication in new window or tab >>Plant SAD proteins: characterization of the tetrameric Pisum sativum protein
    Show others...
    (English)Manuscript (preprint) (Other academic)
    National Category
    Biochemistry and Molecular Biology Biological Sciences
    Research subject
    Biochemistry; Biology
    Identifiers
    urn:nbn:se:oru:diva-2939 (URN)
    Available from: 2005-11-11 Created: 2005-11-11 Last updated: 2017-10-18Bibliographically approved
    2. Non-enzymatic oxidation of NADH by quinones
    Open this publication in new window or tab >>Non-enzymatic oxidation of NADH by quinones
    2005 (English)In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 414, no 1-3, p. 243-247Article in journal (Refereed) Published
    Abstract [en]

    Non-enzymatic oxidation of NADH by a large number of different quinones has been explored both theoretically and experimentally. It is concluded that the smaller benzo- and naphtho-quinones are capable of oxidising NADH in aqueous solution, whereas the larger anthraquinone is not. The mechanisms of stepwise electron and proton transfers are explored, and ruled out in favour of direct hydride transfer. For menadione (2-methyl-1,4-naphthoquinone), no reaction is observed experimentally; theoretically we find that there is a very close balance between the energetic cost of hydride removal from NADH and the energy gain of formation of the menadione semiquinone radical anion.

    National Category
    Biological Sciences Biochemistry and Molecular Biology
    Research subject
    Biology; Biochemistry
    Identifiers
    urn:nbn:se:oru:diva-2940 (URN)10.1016/j.cplett.2005.08.067 (DOI)
    Available from: 2005-11-11 Created: 2005-11-11 Last updated: 2017-12-14Bibliographically approved
    3. Tissue distribution of short-chain alcohol dehydrogenase (SAD) proteins in pea (Pisum sativum) in the absence and presence of UV-B stress, and heterologous stress-induced expression from the SAD promoter
    Open this publication in new window or tab >>Tissue distribution of short-chain alcohol dehydrogenase (SAD) proteins in pea (Pisum sativum) in the absence and presence of UV-B stress, and heterologous stress-induced expression from the SAD promoter
    Show others...
    (English)Manuscript (preprint) (Other academic)
    National Category
    Biochemistry and Molecular Biology Biological Sciences
    Research subject
    Biochemistry; Biology
    Identifiers
    urn:nbn:se:oru:diva-2941 (URN)
    Available from: 2005-11-11 Created: 2005-11-11 Last updated: 2017-10-18Bibliographically approved
    4. Modelling Pisum sativum short-chain dehydrogenase/reductase enzymes
    Open this publication in new window or tab >>Modelling Pisum sativum short-chain dehydrogenase/reductase enzymes
    (English)Manuscript (Other academic)
    National Category
    Biological Sciences
    Research subject
    Biology
    Identifiers
    urn:nbn:se:oru:diva-2942 (URN)
    Available from: 2005-11-11 Created: 2005-11-11 Last updated: 2017-10-18Bibliographically approved
  • 288.
    Scherbak, Nikolai
    et al.
    Örebro University, Department of Natural Sciences.
    Ala-Häivälä, Anneli
    Gittins, John R.
    Brosché, Mikael
    Strid, Hilja
    Strid, Åke
    Örebro University, Department of Natural Sciences.
    Tissue distribution of short-chain alcohol dehydrogenase (SAD) proteins in pea (Pisum sativum) in the absence and presence of UV-B stress, and heterologous stress-induced expression from the SAD promoterManuscript (preprint) (Other academic)
  • 289.
    Scherbak, Nikolai
    et al.
    Örebro University, Department of Natural Sciences.
    Brosché, Mikael
    Ala-Häivälä, Anneli
    Olsson, Annika
    Enroth, Cristofer
    Örebro University, Department of Natural Sciences.
    Eriksson, Leif A.
    Örebro University, Department of Natural Sciences.
    Nilsson, Fredrik
    Strid, Åke
    Örebro University, Department of Natural Sciences.
    Plant SAD proteins: characterization of the tetrameric Pisum sativum proteinManuscript (preprint) (Other academic)
  • 290.
    Scherbak, Nikolai
    et al.
    Örebro University, Department of Natural Sciences.
    Strid, Åke
    Örebro University, Department of Natural Sciences.
    Eriksson, Leif A.
    Örebro University, Department of Natural Sciences.
    Non-enzymatic oxidation of NADH by quinones2005In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 414, no 1-3, p. 243-247Article in journal (Refereed)
    Abstract [en]

    Non-enzymatic oxidation of NADH by a large number of different quinones has been explored both theoretically and experimentally. It is concluded that the smaller benzo- and naphtho-quinones are capable of oxidising NADH in aqueous solution, whereas the larger anthraquinone is not. The mechanisms of stepwise electron and proton transfers are explored, and ruled out in favour of direct hydride transfer. For menadione (2-methyl-1,4-naphthoquinone), no reaction is observed experimentally; theoretically we find that there is a very close balance between the energetic cost of hydride removal from NADH and the energy gain of formation of the menadione semiquinone radical anion.

  • 291. Schyman, Patric
    et al.
    Eriksson, Leif A.
    Örebro University, Department of Natural Sciences.
    Zhang, Ru bo
    Laaksonen, Aatto
    Hydroxyl radical - thymine adduct induced DNA damages2008In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 458, no 1-3, p. 186-189Article in journal (Refereed)
    Abstract [en]

    DNA damages caused by a 5-hydroxy-5,6-dihydrothymine-6-yl radical (5-OHT-6yl) abstracting a C20 hydrogen from a neighboring sugar (inter-H abstraction) have been theoretically investigated using hybrid DFT in gas phase and in water solution. The inter-H abstraction was here shown to be comparable in energy (24 kcal mol 1) with the intra-H abstraction in which the 5-OHT-6yl abstracts a C20 hydrogen from its own sugar. The effect of a neutrally or a negatively charged phosphate group was also studied and the results show no significant impact on the activation energy of the hydrogen abstraction whereas base release and strand break reactions are affected.

  • 292. Schyman, Patric
    et al.
    Zhang, Ru bo
    Eriksson, Leif A.
    Örebro University, Department of Natural Sciences.
    Laaksonen, Aatto
    Hydrogen Abstraction from Deoxyribose by a Neighbouring Uracil-5-yl Radical2007In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 9, p. 5975-5979Article in journal (Refereed)
    Abstract [en]

    Hydrogen abstraction from the C1 and C2 positions of deoxyadenosine by a neighbouring uracil-5-yl radical in the 5-AU-3 DNA sequence is explored using DFT. This hydrogen abstraction is the first step in a sequence leading to single or double strand break in DNA. The uracil-5-yl radical can be the result of photolysis or low-energy electron (LEE) attachment. If the radical is produced by photolysis the neighbouring adenine will become a cation radical and if it is produced by LEE the adenine will remain neutral. The hydrogen abstraction reactions for both cases were investigated. It is concluded that it is possible for the uracil-5-yl to abstract hydrogen from C1 and C2. When adenine is neutral there is a preference for the C1 site and when the adenine is a radical cation the C2 site is the preferred. If adenine is positively charged, the rate-limiting step when abstracting hydrogen from C1 is the formation of an intermediate crosslink between uracil and adenine. This crosslink might be avoided in dsDNA, making C1 the preferred site for abstraction.

  • 293. Sebastian, Eider San
    et al.
    Matxain, Jon M.
    Örebro University, Department of Natural Sciences.
    Eriksson, Leif A.
    Örebro University, Department of Natural Sciences.
    Stote, Roland H.
    Dejaegere, Annick
    Cossio, Fernando P.
    Lopez, Xabier
    Metal ion dependent adhesion sites in integrins: A Combined DFT and QMC Study on Mn2+2007In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 111, no 30, p. 9099-9103Article in journal (Refereed)
    Abstract [en]

    The theoretical study of relative energies of different spin states of Mn2+ has been carried out for the isolated cation and for structures in which the cation is coordinated to ligands that represent the first coordination shell in a protein environment that contains a metal ion dependent adhesion site (MIDAS, found in the ligand binding domain of protein LFA-1). The calculations determine whether the ligand field generated by a prototype protein environment affects the relative energies between high, intermediate, and low spin states. Geometry optimizations and vibrational frequency calculations were carried out at the B3LYP/SKBJ+* level of theory. Single point calculations were performed at the B3LYP/6-311++G(2df,2p) and diffusion monte carlo (DMC) levels for the refinement of the electronic energies. These calculations reveal important differences in the relative energies between high/low spin complexes obtained by B3LYP and DMC and show that although both DFT and DMC show similar trends, a higher level method such as DMC is necessary for a quantitative description of the interactions between Mn2+ and its natural ligands. (G)s of acetate-type ligand binding reactions were calculated that show that the higher the spin of the manganese complex, the lower the affinity for the ligand.

  • 294. Sepulveda, Borja
    et al.
    Alaverdyan, Yuri
    Alegret, Joan
    Käll, Mikael
    Johansson, Peter
    Örebro University, Department of Natural Sciences.
    Shape effects in the localized surface plasmon resonance of single nanoholes in thin metal films2008In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 16, no 8, p. 5609-5616Article in journal (Refereed)
    Abstract [en]

    We report on the polarization-dependent optical response of elongated nanoholes in optically thin gold films. We measured elastic scattering spectra of spatially isolated ellipsoidal nanoholes with varying aspect ratio and compared the results to electrodynamic simulations. Both experiments and theory show that the plasmon mode that is polarized parallel to the short axis of the ellipsoidal hole red-shifts with increasing aspect ratio. This behavior is completely opposite to the case of elongated metal particles. We present a simple analytical model that qualitatively explains the observations in terms of the different orientations of the induced dipole moments in holes and particles.

  • 295.
    Strid, Åke
    et al.
    Örebro University, Department of Natural Sciences.
    Brosché, Mikael
    Opportunities to genetically modify plants to cope with environmental stress2001In: British Food Journal, ISSN 0007-070X, E-ISSN 1758-4108, Vol. 103, no 11, p. 796-800Article in journal (Refereed)
    Abstract [en]

    Discusses the responses of plants to a variety of environmental stresses and considers different techniques that could potentially be used to detect and amplify such responses. Because plants may naturally produce steroids in response to raised stress levels, the paper suggests that genetic modification of crop plants to improve resistance to stress is worth investigating as a strategy. Sensitive to public concerns about the safety of transgenic crops, the authors suggest using such plants in carefully controlled locations.

  • 296.
    Sundberg, Bodil
    Örebro University, Department of Natural Sciences.
    Att kommunicera naturvetenskap med lärarstudenter med inriktning mot yngre åldrar2007Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Denna uppsats handlar om kommunikation mellan föreläsare och studenter vid en lärarutbildningskurs i naturvetenskap som riktar sig mot yngre åldrar. I arbetet presenteras en studie av hur väl studenter kunde återge innehållet i tre föreläsningar, dels enskilt och dels efter gruppdiskussioner. Syftet med studien var att få större insikt i om det förekom ”förståelseklyftor” mellan lärarna och studenterna på inriktningen, och om dessa kunde överbryggas med hjälp av gruppdiskussioner. I studien fick studenterna efter varje föreläsningstillfälle till uppgift att individuellt göra en skriftlig sammanfattning (2-3 meningar) av vad föreläsningen handlat om, samt beskriva de tre viktigaste budskapen i varje föreläsning. Studenterna arbetade därefter gruppvis med samma uppgifter för att den här gången komma fram till ett gemensamt svar. Studenternas skriftliga svar – både de enskilda och de gruppvisa - kategoriserades sedan enligt hur väl de stämde överens med föreläsarens beskrivning av den egna föreläsningens centrala innehåll och tre viktigaste budskap. En jämförelse gjordes också mellan studenternas individuella och gruppernas gemensamma svar.

    Sammanfattningsvis kunde man av resultaten se att studenterna relativt väl kunde redogöra för det innehåll och budskap som föreläsaren avsett att förmedla, men att de efter gemensamma diskussioner i de flesta fallen kommit ännu närmare. De fall där studenterna inte tillsammans kunnat resonera sig fram till en beskrivning som bättre sammanföll med föreläsarens beskrivning berörde moment med ett abstrakt innehåll. Slutsatsen blir att strukturerade gruppdiskussioner i kombination med skrivuppgifter mycket väl kan vara gynnsamma för fördjupad förståelse och därmed är väl värda att lägga ner tid på. Men för att fånga upp missförstånd rörande mer abstrakta momenten krävs en uppföljning där studenterna inte arbetar på egen hand. Vidare föreslås att mer tid sätts av dels till att bättre skola in studenterna i ett (natur)vetenskapligt tankesätt, dels till att diskutera med studenterna om deras egna inställningar till sitt studieprojekt. Detta för att bättre förbereda dem för ett arbete i en förskola som svängt från att vara en främst vårdande plats till att också vara en plats för grundläggandet av ett livslångt lärande.

  • 297. Sundqvist, Maja K.
    et al.
    Björk, Robert G.
    Örebro University, Department of Natural Sciences.
    Molau, Ulf
    Establishment of boreal forest species in alpine dwarf-shrub heath in subarctic Sweden2008In: Plant Ecology & Diversity, ISSN 1755-0874, E-ISSN 1755-1668, Vol. 1, no 1, p. 67-75Article in journal (Refereed)
    Abstract [en]

    Background: Saplings of mountain birch ( Betula pubescens ssp. czerepanovii) have established in pockets of dwarf-shrub heath approximately 250 m above the treeline in the Latnjavagge Valley, northern Sweden. Aim: We examined if the establishment of these mountain birch outposts was related to favourable local microclimate, and if birch establishment has affected the surrounding vegetation, changing it from dwarf-shrub heath to more akin to birch forest floor. Methods: Daily mean and mean maximum temperatures were compared for two sites in the dwarf-shrub heath ( 990 m a. s. l., few birch saplings; 1060 m a. s. l., numerous birch saplings) between January 2005 and June 2006. The cover-abundance of vascular plants was estimated in sample plots in dwarf-shrub heath with mountain birch, dwarf-shrub heath without mountain birch, in heath between the upper limit of closed mountain birch forest and the treeline, and in closed mountain birch forest. Species composition and diversity were statistically compared. The presence in the dwarf-shrub heath of boreal montane species other than birch was also noted. Results: The higher elevation site, containing a higher density of birch, had a significantly higher growing season temperature than the lower elevation site. There was a significant difference in plant community composition between the alpine heath plots containing mountain birch saplings and plots without mountain birch, alpine heath with birch being more similar to the plots of the treeline ecotone and the birch forest than to alpine heath without birch. No significant difference in species diversity among plots in dwarf-shrub heath was found and species diversity increased with altitude. A number of montane species were observed in the dwarf-shrub heath, however, their distribution was not associated with that of the mountain birch. Conclusions: This study provides evidence for favourable microclimate being a key driver for the establishment of mountain birch above the treeline. In addition, the results imply that the composition of the dwarf-shrub heath changes after the establishment of mountain birch to a plant community whose composition points towards a birch forest.

  • 298.
    Suèr, Pascal
    Örebro University, Department of Natural Sciences.
    Electroremediation of contaminated soil2001Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Electroremediation was applied to contaminated soils in order to study the transport of metals and organic compounds by the external electric field. The electric field caused acidic conditions near the anode, so that copper, zinc, lead, nickel, cadmium, calcium and manganese were released from soil from a chlor-alkali site. The metals were transported towards and immobilised near the cathode, where pH was high. The metals were very strongly attached to the soil, which was shown by selective extraction. Mercury was removed through the electromigration of a mercury-iodide complex. 89 % of the mercury was removed from the soil near the cathode, and 46 % had arrived in the anode solution after 3 days. Chloride mobilised less than 50 %.

    Clay had an over-all larger influence (retardation) then peat or goethite on the migration behaviour of metals in an artificial soil with sand base. The influence of clay on polyaromatic hydrocarbons (PAH) was the opposite. The presence of clay or fulvic acid increased the apparent solubility of pyrene and phenanthrene. However, when solid organic matter was added, pyrene and phenanthrene were sorbed to the soil, and the organic matter that was released into the soil solution could not compete for the PAH. Fulvic, citric, oxalic and gluconic acids, and phosphate were transported towards the cathode, while chloride, nitrate and sulphate moved towards the anode, as expected.

    The results from an in-situ pilot scale experiment on mercury-contaminated soil are presented as well as a discussion on the Swedish method of surveying contaminated sites (MIFO).

    List of papers
    1. Natural organic matter to enhance electrokinetic transport of PAH
    Open this publication in new window or tab >>Natural organic matter to enhance electrokinetic transport of PAH
    (English)Manuscript (preprint) (Other academic)
    National Category
    Chemical Sciences
    Research subject
    Enviromental Science
    Identifiers
    urn:nbn:se:oru:diva-16001 (URN)
    Available from: 2011-06-17 Created: 2011-06-17 Last updated: 2017-10-17Bibliographically approved
    2. Multivariate evaluation of electrokinetic movement of heavy metals by systematic variation of the voltage, the soil composition and complexing agents
    Open this publication in new window or tab >>Multivariate evaluation of electrokinetic movement of heavy metals by systematic variation of the voltage, the soil composition and complexing agents
    (English)Manuscript (preprint) (Other academic)
    National Category
    Chemical Sciences
    Research subject
    Enviromental Science
    Identifiers
    urn:nbn:se:oru:diva-16002 (URN)
    Available from: 2011-06-17 Created: 2011-06-17 Last updated: 2017-10-17Bibliographically approved
    3. Speciation and transport of heavy metals and macroelements during electroremediation
    Open this publication in new window or tab >>Speciation and transport of heavy metals and macroelements during electroremediation
    (English)Manuscript (preprint) (Other academic)
    National Category
    Chemical Sciences
    Research subject
    Enviromental Science
    Identifiers
    urn:nbn:se:oru:diva-16003 (URN)
    Available from: 2011-06-17 Created: 2011-06-17 Last updated: 2017-10-17Bibliographically approved
    4. Mercury transport and speciation during electrokinetic soil remediation
    Open this publication in new window or tab >>Mercury transport and speciation during electrokinetic soil remediation
    (English)Manuscript (preprint) (Other academic)
    National Category
    Chemical Sciences
    Research subject
    Enviromental Science
    Identifiers
    urn:nbn:se:oru:diva-16007 (URN)
    Available from: 2011-06-17 Created: 2011-06-17 Last updated: 2017-10-17Bibliographically approved
    5. Mercury contaminated soil remediation by iodide and electroreclamation
    Open this publication in new window or tab >>Mercury contaminated soil remediation by iodide and electroreclamation
    (English)Manuscript (preprint) (Other academic)
    National Category
    Chemical Sciences
    Research subject
    Enviromental Science
    Identifiers
    urn:nbn:se:oru:diva-16008 (URN)
    Available from: 2011-06-17 Created: 2011-06-17 Last updated: 2017-10-17Bibliographically approved
    6. Critical remarks concerning the method used in Sweden for risk assessment of contaminated soils (MIFO)
    Open this publication in new window or tab >>Critical remarks concerning the method used in Sweden for risk assessment of contaminated soils (MIFO)
    (English)Manuscript (preprint) (Other academic)
    National Category
    Chemical Sciences
    Research subject
    Enviromental Science
    Identifiers
    urn:nbn:se:oru:diva-16009 (URN)
    Available from: 2011-06-17 Created: 2011-06-17 Last updated: 2017-10-17Bibliographically approved
  • 299.
    Suèr, Pascal
    et al.
    Örebro University, Department of Natural Sciences.
    Allard, Bert
    Örebro University, Department of Natural Sciences.
    Mercury transport and speciation during electrokinetic soil remediationManuscript (preprint) (Other academic)
  • 300.
    Suèr, Pascal
    et al.
    Örebro University, Department of Natural Sciences.
    Gitye, Katarina
    Allard, Bert
    Örebro University, Department of Natural Sciences.
    Speciation and transport of heavy metals and macroelements during electroremediationManuscript (preprint) (Other academic)
34567 251 - 300 of 350
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