| 1. |
- Dérand, Helene, et al.
(författare)
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Pol(ethylene glycol) Graft Copolymers Containing Carboxylic Acid Groups: Aggregation and Viscometric Properties in Aqueous Solution
- 1996
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Ingår i: Macromolecules. - 0024-9297. ; 29:27, s. 8770-8775
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Tidskriftsartikel (refereegranskat)abstract
- Poly(ethylene glycol) monomethyl ethers (MPEG) were grafted on copolymers of maleic anhydride and styrene, methyl methacrylate, and ethylhexyl methacrylate, respectively. Hydrolysis of the remaining anhydride residues gave graft copolymers carrying a large number of carboxylic acid groups along the main chains. The properties in aqueous solutions of these graft copolymers were studied with respect to aggregation behavior and viscometric properties, Aggregation of the polymers was examined by quasi-elastic light scattering and now field-flow fractionation in water and KCl solution. Both methods showed that the anionic graft copolymers mainly were present as single molecules in pure water, with a minor fraction of aggregates. In KCI solution, aggregates with average sizes of approximately 30 nm were the dominant species. In aqueous solution, the polymers exhibited polyelectrolyte behavior, i.e., a dramatic increase of the viscosity upon neutralization. Graft copolymers with hydrophobic groups in the backbone had lower viscosities.
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| 2. |
- Wittgren, Bengt, et al.
(författare)
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Size characterization of a charged amphiphilic copolymer in solutions of different salts and salt concentrations using flow field-flow
- 1996
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Ingår i: Langmuir. - 0743-7463. ; 12:25, s. 5999-6005
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Tidskriftsartikel (refereegranskat)abstract
- The aggregation behavior of a charged amphiphilic graft copolymer, prepared from poly(styrene-co-methyl methacrylate-co-maleic anhydride) and poly(ethylene oxide) monomethyl ether, was studied using flow field-flow fractionation (flow FFF). This method determines the hydrodynamic size of aggregates. The polymer was shown to have a complex aggregation behavior in aqueous solutions containing salt. This was expressed in the formation of differently sized structures, from single polymer chains to large polymolecular aggregates. The polymer changed its aggregation ability in the presence of different salts and salt concentrations, as reflected by changes in hydrodynamic size. Three different salts were tested: potassium chloride, sodium sulfate, and sodium phosphate. Even at micromolar concentrations of sodium sulfate, a pronounced aggregation was observed, probably due to reduced charge repulsion. At higher concentrations of the ''salting-out'' salts, the hydrodynamic size increased rapidly, reflecting the reduced solubility of the hydrophilic parts of the polymer, i.e. the poly(ethylene oxide) grafts. Sodium sulfate, and sodium phosphate in particular, had a stronger influence on polymer aggregation than potassium chloride. This agrees with current knowledge of electrolytic effects on poly(ethylene oxide) solutions. Flow FFF was found to be a suitable characterization technique for these complex systems, rapidly and efficiently separating different polymer aggregate populations ranging from a few nanometers up to 0.1 mu m.
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| 3. |
- Andersson, M, et al.
(författare)
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Size and Structure Characterization of Ethylhydroxyethyl Cellulose by the Combination of Field-Flow Fractionation with Other Techniques. Investigation of Ultralarge Components
- 2004
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1526-4602 .- 1525-7797. ; 5:1, s. 97-105
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Tidskriftsartikel (refereegranskat)abstract
- Ethylhydroxyethyl cellulose (EHEC) of three different viscosity classes (EHEC I, II, and III) was analyzed by programmed cross-flow asymmetrical flow field-flow fractionation coupled to multiangle light scattering and refractive index detectors to determine their size and molar mass distribution. Two size populations were detected in the two lower viscosity classes, EHEC I and II, one high molar mass and one ultrahigh molar mass (UHM). The two covered molar masses from 104 up to 109 g·mol-1. The highest viscosity class EHEC III was less size-dispersed covering molar masses from 5 × 105 to 5 × 107 g·mol-1. Filtering of the EHEC II solution removed small amounts of compact UHM material. Enzyme treatments were performed on EHEC II to further characterize it. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and anion ion-exchange chromatography coupled to pulsed amperometric detection showed that the UHM component contained EHEC.
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| 4. |
- ARNELL, MAGNUS
(författare)
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Performance Assessment of Wastewater Treatment Plants : Multi-Objective Analysis Using Plant-Wide Models
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- As the knowledge about anthropogenic impacts of climate change has grown, the awareness of the contributions from treatment of wastewater has widened the scope for wastewater treatment plants (WWTPs). Not only shall ever stricter effluent constraints be met, but also energy efficiency be increased, greenhouse gases mitigated and resources recovered. All under a constant pressure on costs. The main objective of this research has been to develop a plant-wide modelling tool to evaluate the performance of operational strategies for multiple objectives at the plant and for off-site environmental impact. The plant-wide model platform Benchmark Simulation Model no. 2 (BSM2) has been modified to improve the evaluation of energy efficiency and include greenhouse gas emissions. Furthermore, the plant-wide process model has been coupled to a life cycle analysis (LCA) model for evaluation of global environmental impact. For energy evaluation, a dynamic aeration system model has been adapted and implemented. The aeration model includes oxygen transfer efficiency, dynamic pressure in the distribution system and non-linear behaviour of blower performance. To allow for modelling of energy recovery via anaerobic co-digestion the digestion model of BSM2 was updated with a flexible co-digestion model allowing for dynamic co-substrate feeds. A feasible procedure for substrate characterisation was proposed. Emissions of the greenhouse gases CO2, CH4 and N2O were considered. The bioprocess model in BSM2 was updated with two-step nitrification, four-step denitrification and nitrifier denitrification to capture N2O production. Fugitive emissions of the three gases were included from digestion, cogeneration and sludge storage. The models were tested in case studies for the three areas of development: aeration, co-digestion and greenhouse gas production. They failed to reject the hypothesis that dynamic process models are required to assess the highly variable operations of wastewater treatment plants. All parts were combined in a case study of the Käppala WWTP in Lidingö, Sweden, for comparison of operational strategies and evaluation of stricter effluent constraints. The averaged model outputs were exported to an LCA model to include off-site production of input goods and impact of discharged residues and wastes. The results reveal trade-offs between water quality, energy efficiency, greenhouse gas emissions and abiotic depletion of elemental and fossil resources. The developed tool is generally applicable for WWTPs and the simulation results from this type of combined models create a good basis for decision support.
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| 5. |
- Axelsson, Bodil, 1965-, et al.
(författare)
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Skärningspunkter och glapp i länkat, delat och nätverkat kulturarv
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Idag delar arkiv, museer och bibliotek en och samma utmaning – gränserna mellan dem och mellan vardagsliv och kulturarvsinstitutioner blir allt mer porösa när digitala miljöer får större betydelse för hur människor, miljöer och kulturarvspraktiker knyts samman. Redan utpekade kulturarv får nya sammanhang och nya former för framspringande kulturarv skapas. I det här projektet studeras de skärningspunkter och glapp som uppstår mellan kulturarvsmyndigheter och identitetspolitiskt kulturarvsskapande bland människor i platsbaserade gemenskaper likaväl som bland dem som förenas av funktionsnedsättning, sexualitet och könsuttryck, etnisk tillhörighet eller religion.
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| 6. |
- Fitzpatrick, Fiona, et al.
(författare)
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NMR, cloud-point measurements and enzymatic depolymerization: Complementary tools to investigate substituent patterns in modified celluloses
- 2006
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1526-4602 .- 1525-7797. ; 7:10, s. 2909-2917
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Tidskriftsartikel (refereegranskat)abstract
- The substituent patterns of some chemically modified celluloses were characterized as a function of their size distribution, using size-exclusion chromatography coupled to both nuclear magnetic resonance spectroscopy (NMR) and cloud-point measurements. Intact and enzymatically hydrolyzed methyl cellulose (MC) was fractionated according to size, and the level of substitution of the fractions was measured off-line using NMR. Clouding behavior was also measured as a function of size. Clear differences between hydrolyzed and nonhydrolyzed samples were observed using both techniques. For samples that had been selectively hydrolyzed using cellulose-degrading enzymes, NMR data showed a direct link between the degree of degradation and the level of substitution. Differences in the clouding behavior highlighted changes in substituent levels and substituent patterns across the size distribution. The techniques gave valuable and somewhat complementary information on the substituent distributions of the samples before and after enzymatic hydrolysis.
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| 7. |
- Johnson, Louis Banka, et al.
(författare)
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Combination of pre-operative radiotherapy and surgery suppresses local accumulation of collagen and TGF-beta 1 in rats
- 2006
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Ingår i: Journal of Surgical Research. - : Elsevier BV. - 1095-8673 .- 0022-4804. ; 133:2, s. 136-142
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Tidskriftsartikel (refereegranskat)abstract
- Background. The systemic and local tissue repair responses of radiation in combination with surgery are still unclear. We have studied the effect of fractionated pre-operative radiotherapy with or without subsequent laparotomy on collagen accumulation using a rodent model. Materials and methods. Thirty-two male Sprague-Dawley rats were divided into four groups (eight rats per group): 1) sham radiation and sham laparotomy (control); 2) sham radiation and laparotomy; 3) radiation and sham laparotomy; and 4) radiation followed by laparotomy. Expanded polytetrafluoroethylene (ePTFE) tubes were implanted subcutaneously in the abdominal wall in the radiotherapy field and on the back outside the radiotherapy field day 0. The abdomen (3 cm x 4 cm) was irradiated day 3 (10 Gy) and again day 7 (10 Gy). On day 10, implants were extirpated, laparotomy undertaken in groups 2 and 4 and new ePTFE tubes implanted subcutaneously. The second implants were extirpated on day 20. Implants were analyzed for hydroxyproline, total protein and transforming growth factor-ss 1 (TGF-ss 1) levels. Results. On day 10, hydroxyproline (P < 0.05) and TGF-ss 1 (P < 0.001) were lower in ePTFE tubes in irra-diated compared with non-irradiated rats. On day 20, the abdominal ePTFE hydroxyproline remained low (P < 0.001) in animals subjected to laparotomy and pre-operative irradiation while hydroxyproline levels of rats subjected to irradiation only were similar to controls. The effects of radiation on hydroxyproline were confined to the irradiated abdominal area. There was a positive correlation between hydroxyproline and TGF-ss 1 levels in the abdominal wall implant day 20 (r = 0.53, P < 0.005). Conclusion. A clinically relevant fractionated radiation scheme reduced subcutaneous collagen accumulation pre-operatively and profoundly within the radiation field post-operatively after laparotomy, possibly because of lowered TGF ss 1 levels. (c) 2006 Elsevier Inc. All rights reserved.
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| 8. |
- Johnson, Louis Banka, et al.
(författare)
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Radiation enteropathy and leucocyte-endothelial cell reactions in a refined small bowel model
- 2004
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Ingår i: BMC Surgery. - : Springer Science and Business Media LLC. - 1471-2482. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Leucocyte recruitment and inflammation are key features of high dose radiation-induced tissue injury. The inflammatory response in the gut may be more pronounced following radiotherapy due to its high bacterial load in comparison to the response in other organs. We designed a model to enable us to study the effects of radiation on leucocyte-endothelium interactions and on intestinal microflora in the murine ileum. This model enables us to study specifically the local effects of radiation therapy. METHOD: A midline laparotomy was performed in male C57/Bl6 mice and a five-centimetre segment of ileum is irradiated using the chamber. Leucocyte responses (rolling and adhesion) were then analysed in ileal venules 2 - 48 hours after high dose irradiation, made possible by an inverted approach using intravital fluorescence microscopy. Furthermore, intestinal microflora, myeloperoxidase (MPO) and cell histology were analysed. RESULTS: The highest and most reproducible increase in leucocyte rolling was exhibited 2 hours after high dose irradiation whereas leucocyte adhesion was greatest after 16 hours. Radiation reduced the intestinal microflora count compared to sham animals with a significant decrease in the aerobic count after 2 hours of radiation. Further, the total aerobic counts, Enterobacteriaceae and Lactobacillus decreased significantly after 16 hours. In the radiation groups, the bacterial count showed a progressive increase from 2 to 24 hours after radiation. CONCLUSION: This study presents a refinement of a previous method of examining mechanisms of radiation enteropathy, and a new approach at investigating radiation induced leucocyte responses in the ileal microcirculation. Radiation induced maximum leucocyte rolling at 2 hours and adhesion peaked at 16 hours. It also reduces the microflora count, which then starts to increase steadily afterwards. This model may be instrumental in developing strategies against pathological recruitment of leucocytes and changes in intestinal microflora in the small bowel after radiotherapy.
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| 9. |
- Korner, Anna, et al.
(författare)
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Influence of Different Polymer Types on the Overall Release Mechanism in Hydrophilic Matrix Tablets
- 2009
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Ingår i: Molecules. - : MDPI AG. - 1420-3049. ; 14:8, s. 2699-2716
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Tidskriftsartikel (refereegranskat)abstract
- The effect of three different types of polymer chain structures on the polymer release from hydrophilic matrix tablets was investigated by comparing a synthetic semi-crystalline linear polymer (PEO), a branched amorphous polysaccharide (dextran) and an amorphous substituted cellulose derivative (HPMC). The polymer release rates for tablets containing mixtures of high and low molecular weight grades in different ratios were determined by using a modified USP II method and a SEC-RI chromatography system. The results showed that independent of polymer type: (i) plots of the release versus time had similar shapes, (ii) the release of long and short polymer chains was equal and no fractionation occurred during the release and (iii) the release rate could be related to the average intrinsic viscosity of the polymer mixtures. This confirms the hypothesis that the release rate can be related to a constant viscosity on the surface of the hydrophilic matrix tablet and that it is valid for all the investigated polymers.
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| 10. |
- Körner, Anna, et al.
(författare)
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Molecular Information on the Dissolution of Polydisperse Polymers: Mixtures of Long and Short Poly(ethylene oxide).
- 2005
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 109:23, s. 11530-11537
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Tidskriftsartikel (refereegranskat)abstract
- Abstract:A systematic study of the dissolution of dry, polydisperse poly(ethylene oxide) (PEO) samples, obtained from mixtures of low-molecular-weight and high-molecular-weight PEO, was made. During the dissolution process, the individual release of the low- and high-molecular-weight fractions was monitored. The high-molecular-weight/low-molecular-weight ratio controls the release rate, and the fraction of high-molecular-weight polymers dominates the effect on the overall release rate in mixed PEO tablets. Both fractions are released at the same rate during the main part of the dissolution process; however, during the initial dissolution period a fractionation occurs. The release rate is not a unique function of the average molecular weight of the polymer, but also depends on the polydispersity. By contrast, the average dimension of a polymer coil, as given by the intrinsic viscosity, gives a good prediction of the release rate irrespective of the polydispersity or details of the molecular weight distribution.
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