SwePub
Sök i SwePub databas

  Utökad sökning

Träfflista för sökning "AMNE:(NATURAL SCIENCES Chemistry Environmental chemistry) ;conttype:(scientificother);spr:eng;srt2:(2000-2004)"

Sökning: AMNE:(NATURAL SCIENCES Chemistry Environmental chemistry) > Övrigt vetenskapligt/konstnärligt > Engelska > (2000-2004)

  • Resultat 1-10 av 54
Sortera/gruppera träfflistan
   
NumreringReferensOmslagsbildHitta
1.
  • Dario, Mårten, et al. (författare)
  • Effects of cement additives on radionuclide mobility
  • 2004
  • Ingår i: Scientific basis for radioactive waste management XXVII. - Warrendale, Pa : Materials Research Society. - 1558997520 ; , s. 639-644
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)
  •  
2.
  •  
3.
  •  
4.
  •  
5.
  •  
6.
  • Sandholm, Anna, 1966- (författare)
  • Metabolism of some polychlorinated biphenyl and polybrominated diphenyl ether congeners in the rat
  • 2003
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • For the understanding of the metabolic fate of xenobiotics, in vivo studies are needed. In this thesis the metabolism of CB-28 and CB-77 and BDE-209 in the rat are determined. In addition, pharmacokinetic studies of CB-28 and BDE- 209 are included. The compounds were radiolabelled and their excretion and tissue distribution determined. The metabolites were characterised by their behaviour in the clean-up steps. The analysis of non-conjugated metabolites was performed by GC/MS. For other metabolites, HPLC with radioactivity monitoring and LC/MS were used for the characterisation. The absorption of BDE-209 has previously been reported to be low, <1%. In this work the bioavailability of BDE-209 was determined to be as high as 26% and strong indications that its absorption was even higher. Lipophilic compounds are generally distributed to lipid-rich tissues. CB-28 was rapidly distributed to adipose tissue, which over time had the highest concentration. BDE-209 was not readily distributed to adipose tissue, the liver and plasma showing the highest concentrations instead. Selective distribution can be explained by selective affinity for certain tissue proteins. Orthohydroxylated CB-28 metabolite was selectively retained in the brain. There were indications that hydroxylated BDE-209 metabolites were selectively retained in plasma. The terminal half-life of BDE-209 in rat plasma was 57 h and metabolism and faecal excretion the major routes of elimination.Common for all compounds was that the metabolic pathway included reactive metabolites. Non-extractable, water-soluble and lipid-bound metabolites were also found. For CB-77, the lipid-bound metabolites were studied and these were shown to be associated to polar lipids, e.g. phospholipids. There were indications that they were formed in the liver.In conclusion, this thesis discusses the metabolism of two PCB congeners and BDE-209. The importances of metabolism studies are emphasised for risk assessment and the understanding of levels in biota. The clearance, metabolism and distribution of a compound are essential for an understanding of biological and toxicological effects.
  •  
7.
  • Tareke, Eden, 1963- (författare)
  • Identification and origin of potential background carcinogens : endogenous isoprene and oxiranes, dietary acrylamide
  • 2003
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The primary aims of this thesis are to discover carcinogens in the general population by identification of products of reaction with hemoglobin (Hb adducts) in blood from humans without known exposure, and tracing the origin of the adducts. Chemicals and/or their metabolites forming Hb adducts mostly also react with DNA and may thus cause mutations, a key event in carcinogenesis. Factors, that may affect in vivo doses, that is cooking of food, degree of unsaturation of dietary fatty acids, and intestinal micro-flora, were investigated. Analysis of adducts to N-termini in Hb, by gas chromatography-tandem mass spectrometry (GC/MS-MS), was applied as a tool.Due to large endogenous production of isoprene the in vivo formation of reactive monoepoxides was studied. Two adducts originating from the monoepoxides were identified in rodents exposed to isoprene or isoprene monoepoxides. Relatively high in vivo doses of monoepoxides were found in mice compared to rats after treatment with isoprene, although the detoxification rates were about equal in both species. Despite an effective metabolism to monoepoxides as shown in the mouse, corresponding background adduct levels were very low in both rodents and humans, probably showing a very low cancer risk increment from endogenous isoprene.Hb adduct levels signify ubiquitous background doses of the mutagens/carcinogens ethylene oxide (EO) and propylene oxide (PO) in humans. Levels of these adducts were earlier shown to be lower in germ-free (GF) than in conventional (CV) mice. Detoxification was shown to be faster in CV mice, but, evidently due to still faster production the in vivo doses of EO and PO were higher in CV than in GF mice. The influence of unsaturated fatty acids was small. Formation of EO and PO and also of a peroxidation indicator in GF mice, that is in the absence of micro-flora, points towards ethene and propene, peroxidatively formed in tissues, being the precursors of the oxiranes. The same mechanism, amplified by changes of the host metabolism caused by the microflora, occurs also in CV animals.Background Hb adducts from acrylamide show a general occurrence, in humans at levels possibly associated with a relatively high cancer risk. Acrylamide is present in tobacco smoke. In wild animals lower adduct levels than in humans are observed. These facts indicate a role of cooking in acrylamide exposure, a hypothesis tested in animal feeding experiments. Rats fed heated feed showed increase of several adducts including un about 10 times increase of the adduct levels from acrylamide, identified by MS-MS in comparison with authentic standards, with confirmation by analysis of acrylamide in heated feed. In follow-up studies with heated foods, high acrylamide formation was found in carbohydrate-rich foodstuffs as compared to low levels in protein foods. Acrylamide was formed above 120°C in a temperature-dependent manner.These studies give support to the use of Hb adducts for the detection and identification of endogenous and exogenous genotoxic factors which are potential contributors to background cancer incidence, and for identification of determinants of their in vivo doses.
  •  
8.
  • Öberg, Tomas (författare)
  • Persistent Organic Pollutants and the Environment : A Chemometric Approach to the Study of Halogenated Aromatics
  • 2003
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Concern is growing about the environmental and health effects of persistent organic pollutants (POPs), many of which are halogenated aromatic compunds. The research reported in this thesis focuses on factors determining their behaviour and release into the environment. The aims have been to relate molecular features with physical and chemical properties and to interpret casual relationships, with the common methodological approach of chemometrics.Quantitative structure-property relationships (QSPR) were investigated for polychlorinated biphenyls (PCB), polychlorinated diphenyl ethers (PCDE) and polybrominated diphenyl ethers (PBDE). QSPR models were developed from computationally derived descriptors using partial least squares regression (PLSR). The results show that it is possible to model and predict properties such as vapour pressure almost to the limit of the experimental error. The models obtained could be applied both to validate available experimental data and extend the current database of experimental determinations.The distribution and levels of brominated flame retardants (BFRs) in sewage sludge were investigated using exploratory data analysis (EDA), analysis of variance (ANOVA) and principal component analysis (PCA). The levels of polybrominated diphenyl ethers (PBDE) and biphenyls (PBB) agreed well with another investigation reported recently, but for tetrabromobisphenol A (TBBPA) there was a divergence, possible due to the analytical methodology. The variation among wastewater treatment plants was statistically significant, and three distinct types of technical products were shown to contribute.The formation and release of chlorinated aromatics was investigated in an industrial afterburner with a series of statistically design experiments. Th effect of temperature was studied with some detail and the results indicate different decomposition pathways for hydrocarbons and chlorinated aromatics. Additional factors were studied in a multifactor experiment, with a full factorial design in two blocks. Catalytic lowtemperature formation and chlorine input were both statistically highly significant factors. Polychlorinated dioxins (PCDD) and dibenzofurans (PCDF) showed a statistically significant correlation to chlorinated benzenes, and the results could thus be described and interpreted within a simple conceptual model. The efficiency of the final oxidation, the chlorine input and the presence of a catalyst (e.g. copper) control the thermal formation of the different groups of chlorinated aromatics.The reported investigations show that empirical 'soft' models can provide insight and understanding of complex chemical properties and reactions. Latent variable models and Taylor polynomials were able to approximate the behaviour of these systems within the investigated boundaries. The chemometric models and methods are thus likely to find use also in other areas of environmental science where theoretical understanding is still limited.
  •  
9.
  • Backe, Cecilia (författare)
  • Persistent organic pollutants in the atmosphere - spatial and temporal variations
  • 2001
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • In these thesis I have studied the spatial and temporal variations of PCBs in the atmosphere and in precipitation in southern Sweden. Further, soil-air exchange processes of PCBs were investigated. Finally, the long-range transport of PCBs and DDT was studied in the Baltic Sea region and in a tropical vs. a temporal region. On the regional scale there were significant differences in PCB concentration in the atmosphere, in precipitation and in soil between nearby sampling-areas. Differences in PCB concentrations between areas probably originated from varying geographical and meteorological conditions that affected exchange processes between air and soil/vegetation surfaces. Temporal variations in PCB concentration in atmosphere and precipitation were also found. For PCBs in the air, a systematic pattern in the deviation from the yearly median value for the region was observed. Wind direction played an important role for PCB concentration in precipitation in coastal areas, while at the inland sites this variable seemed to have a minor influence. To examine the intensity of precipitation scavenging, the total washout ratios were calculated and the highest ratios were observed at the two sites where PCB concentration in the air was high. Further, high concentrations of PCB in precipitation correlated with a composition of highly chlorinated PCB congeners, as shown by principal component analysis. For most of the sites there was a significant negative relationship between PCB concentration and rain volume. Soil type and soil organic matter content was found to be important for the variations in PCB concentration between nearby areas. Highest concentrations were found at two sites with sandy soils, one with an extremely high organic carbon content. Soils with similar soil textures (i.e. sandy silt moraine) did not show any significant differences in PCB concentrations. PCB congener composition was shown to differ between sites, with site-specific congener patterns. No significant relationships were found between air and soil concentrations of PCBs, or between deposition and soil concentrations. From fugacity quotient calculations it was shown that the soil- and air compartments for most of the sampling-areas were close to equilibrium. However, for some areas there was an outgassing of PCBs from the soil and at one site a tendency for a transport of PCBs from the air to the soil was observed. Within the Baltic Sea region a latitudinal gradient of PCBs in the atmosphere was revealed, with higher levels in the south. Further evidence of the global distillation theory was shown in a study with higher atmospheric levels of DDT in a tropical region in comparison with DDT levels in a temperate region. In accordance with the theory, DDT levels were high in fish from the temperate region, but low in fish from the tropical region.
  •  
10.
  • Fiedler, Heidelore, 1953- (författare)
  • Global and local disposition of PCBs
  • 2001
  • Ingår i: PCBs. - Lexington, Ky. : University Press of Kentucky. - 9780813122267 ; , s. 11-15
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)
  •  
Skapa referenser, mejla, bekava och länka
  • Resultat 1-10 av 54
Typ av publikation
doktorsavhandling (37)
konferensbidrag (9)
rapport (6)
annan publikation (1)
bokkapitel (1)
Typ av innehåll
Författare/redaktör
Strömberg, Dan, 1959 (7)
Gårdfeldt, Katarina, ... (7)
Lindqvist, Oliver, 1 ... (5)
Bergman, Åke (4)
Sommar, Jonas, 1969 (4)
Feng, Xinbin (3)
visa fler...
Allard, Bert (3)
Munthe, John (2)
Sommar, Jonas (2)
Tysklind, Mats (2)
Marklund, Stellan, P ... (2)
Eriksson, Lars (1)
Törnqvist, Margareta (1)
Fiedler, Heidelore, ... (1)
Abdu, Yassir Ahmed M ... (1)
Annersten, Hans (1)
Ericsson, Tore (1)
Linden, Johan, Docen ... (1)
Larsson, Mattias (1)
Eriksson, Mats (1)
Fransson, Agneta, 19 ... (1)
Pettersson, Håkan (1)
Backe, Cecilia (1)
Karlsson, Daniel (1)
Fröling, Morgan, 196 ... (1)
Karlsson, Stefan (1)
Greis, Christina (1)
Düker, Anders (1)
Öberg, Tomas, 1956- (1)
Öberg, Tomas (1)
Wennersten, Ronald, ... (1)
Ramnäs, Olle Jerker, ... (1)
Chimuka, Luke (1)
Bergbäck, Bo (1)
Eriksson, Eva, 1973- (1)
Ledin, Anna (1)
Haglund, Peter (1)
Andersson, Barbro (1)
Sommar, J. (1)
Lithner, Delilah, 19 ... (1)
Bergqvist, Per-Ander ... (1)
Larsson, Åke, 1944 (1)
Stjernström, Olof (1)
Fängmark, Ingrid (1)
Nilsson, Calle (1)
Baun, Anders (1)
Lazor, Peter (1)
Nistor, Catalin (1)
Broman, Dag (1)
Lundgren, Kjell (1)
visa färre...
Lärosäte
Stockholms universitet (13)
Umeå universitet (9)
Göteborgs universitet (8)
Lunds universitet (8)
Uppsala universitet (7)
Chalmers tekniska högskola (7)
visa fler...
Örebro universitet (4)
Linnéuniversitetet (4)
visa färre...
Språk
Forskningsämne (UKÄ/SCB)
Naturvetenskap (54)
Teknik (1)
Medicin och hälsovetenskap (1)

År

Kungliga biblioteket hanterar dina personuppgifter i enlighet med EU:s dataskyddsförordning (2018), GDPR. Läs mer om hur det funkar här.
Så här hanterar KB dina uppgifter vid användning av denna tjänst.

 
pil uppåt Stäng

Kopiera och spara länken för att återkomma till aktuell vy