| 1. |
- Sjögren, Torsten, et al.
(författare)
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Analysis of strains in cast iron joints using finite element simulations and digital image correlation techniques
- 2012
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Ingår i: 70th World Foundry Congress 2012, WFC 2012. - 9781622763825 ; , s. 396-401
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Konferensbidrag (refereegranskat)abstract
- The Metalock method is a mechanical joining technique most commonly employed in cracked castings of iron, aluminum and steel. The marine diesel engine designer MAN Diesel & Turbo uses the Metalock method for crack patching in large cast iron components. The service life of these components can thereby be extended, reducing both replacement costs and environmental impact. The purpose of this study is to investigate the mechanical behavior of the Metalock method. This was studied by full scale testing, using a non-contact deformation measurement technique known as digital image correlation (DIC), of cast iron specimens joined together by the Metalock method. Furthermore, finite element (FE) simulations were performed, and verified by experimental results, in order to study the mechanical behavior in detail and to carry out a parametric study on some of the components included in the joint. Experimental tests show that using the DIC technique gives a good possibility to verify the strain-field achieved by FE simulations and improving the understanding of the Metalock joining technique.
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| 2. |
- Svensson, Frida, 1980, et al.
(författare)
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Effects of chirality on the intracellular localization of binuclear ruthenium(II) polypyridyl complexes
- 2012
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Ingår i: Journal of Biological Inorganic Chemistry. - : Springer Science and Business Media LLC. - 0949-8257 .- 1432-1327. ; 17:4, s. 565-571
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Tidskriftsartikel (refereegranskat)abstract
- Interest in binuclear ruthenium(II) polypyridyl complexes as luminescent cellular imaging agents and for biomedical applications is increasing rapidly. We have investigated the cellular localization, uptake, and biomolecular interactions of the pure enantiomers of two structural isomers of [mu-bipb(phen)(4)Ru-2](4+) (bipb is bis(imidazo[4,5-f]-1,10-phenanthrolin-2-yl)benzene and phen is 1,10-phenanthroline) using confocal laser scanning microscopy, emission spectroscopy, and linear dichroism. Both complexes display distinct enantiomeric differences in the staining pattern of fixed cells, which are concluded to arise from chiral discrimination in the binding to intracellular components. Uptake of complexes in live cells is efficient and nontoxic at 5 mu M, and occurs through an energy-dependent mechanism. No differences in uptake are observed between the structural isomers or the enantiomers, suggesting that the interactions triggering uptake are rather insensitive to structural variations. Altogether, these findings show that the complexes investigated are promising for future applications as cellular imaging probes. In addition, linear dichroism shows that the complexes exhibit DNA-condensing properties, making them interesting as potential gene delivery vectors.
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| 3. |
- Andersson, Helene, 1983, et al.
(författare)
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Effects of molecular weight on permeability and microstructure of mixed ethyl-hydroxypropyl-cellulose films
- 2013
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Ingår i: European Journal of Pharmaceutical Sciences. - : Elsevier BV. - 0928-0987 .- 1879-0720. ; 48:1-2, s. 240-248
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Tidskriftsartikel (refereegranskat)abstract
- Films of ethyl cellulose (EC) and water-soluble hydroxypropyl cellulose (HPC) can be used for extended release coatings in oral formulations. The permeability and microstructure of free EC/HPC films with 30% w/w HPC were studied to investigate effects of EC molecular weight. Phase separation during film spraying and subsequent HPC leaching after immersion in aqueous media cause pore formation in such films. It was found that sprayed films were porous throughout the bulk of the films after water immersion. The molecular weight affected HPC leaching, pore morphology and film permeability; increasing the molecular weight resulted in decreasing permeability. A model to distinguish the major factors contributing to diffusion retardation in porous films showed that the trend in permeability was determined predominantly by factors associated with the geometry and arrangement of pores, independent of the diffusing species. The film with the highest molecular weight did, however, show an additional contribution from pore wall/permeant interactions. In addition, rapid drying and increasing molecular weight resulted in smaller pores, which suggest that phase separation kinetics affects the final microstructure of EC/HPC films. Thus, the molecular weight influences the microstructural features of pores, which are crucial for mass transport in EC/HPC films.
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| 4. |
- Andersson, Helene, 1983, et al.
(författare)
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Extensional flow, viscoelasticity and baking performance of gluten-free zein-starch doughs supplemented with hydrocolloids
- 2011
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Ingår i: Food Hydrocolloids. - : Elsevier BV. - 0268-005X .- 1873-7137. ; 25:6, s. 1587-1595
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Tidskriftsartikel (refereegranskat)abstract
- Viscoelastic doughs of zein and starch were prepared at 40 degrees C, above the glass transition temperature of zein. The effects of hydrocolloid supplementation with hydroxypropyl methylcellulose (HPMC) or oat bran with a high content of beta-glucan (28%) were investigated by dynamic measurements in shear, confocal laser scanning microscopy (CLSM) and Hyperbolic Contraction Flow. Zein-starch dough without hydrocolloids exhibited rapid age-related stiffening, believed to be caused by cross-links between peptide chains. A prolonged softness was attributed to doughs containing hydrocolloids, with the oat bran exhibiting the most pronounced reduction in age-related stiffening. Moreover, CLSM-images of dough microstructure revealed that a finer fibre network may be formed by increased shearing through an addition of viscosity-increasing hydrocolloids, a reduction in water content in the dough or the use of appropriate mixing equipment. The Hyperbolic Contraction Flow measurements showed that doughs containing hydrocolloids had high extensional viscosities and strain hardening, suggesting appropriate rheological properties for bread making. Zein-starch dough without hydrocolloids showed poor bread making performance while hydrocolloid additions significantly improved bread volume and height. Although the hydrocolloid supplemented doughs had similar extensional rheological properties and microstructures, a fine crumb structure was attributed only to bread containing HPMC, marking the importance of surface active components in the liquid-gas interface of dough bubble walls. Zein could not mimic the properties of gluten on its own, but hydrocolloids did positively affect the structural and rheological properties of zein, which yielded dough similar to wheat dough and bread with increased volume.
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| 5. |
- Andersson, Helene, 1983
(författare)
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Mass Transport through Phase Separated Films - Effects of Ethyl Cellulose Molecular Weight on Cellulose Derivative Blends for Pharmaceutical Coatings
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Polymer blends are utilized for a variety of applications, not least in pharmaceutical coatings for controlled release of drugs. For instance, blends of ethyl cellulose (EC) and the water-soluble hydroxypropyl cellulose (HPC) can be used to coat drug pellets for oral extendedrelease formulations. Although EC and HPC can be co-dissolved in ethanol, they tend to phase separate during solvent evaporation in the coating process. If a substantial amount of HPC is present in the coating, pores form when the coating is subjected to water. The HPC-rich phase may then serve as a template for the pore geometries that transport the drug. Phase separated microstructures can have a variety of morphological features. However, polymer phase separation is a complex process and much is still left to be understood regardingthe underlying mechanisms that drive structure evolution. A range of physical and chemical parameters are known to affect phase separation, including the molecular weight (MW) of polymers. If the morphology of phase separated structures is affected by the MW, then drugrelease through a phase separated coating is likely to be affected as well. The major aims of this work were to study the effects of the MW of EC, on the mass transport and microstructure in films made of 70% EC and 30% HPC, and to understand the underlying mechanisms behind different release profiles from coated pharmaceutical pellets. A wide range of batches of EC were investigated, with weight average MWs from 19·10^3 to 68·10^3. Overall, the effects on solvent cast films, sprayed films and spray coated pellets were investigated. The MW showed substantial influence on the phase separated morphology, as well as effects on the pore structures in sprayed freestanding films. A decrease in mass transfer ratewith increasing MW of EC was found by permeability measurements on free films and drug release from coated pellets. The observed trend in permeability was mainly affected by the geometries of pores, while drug release was affected by both HPC-leakage and the film structure.As a result, it was concluded that the MW of EC affects the phase separated structure of EC/HPC-films, which has profound effects on diffusion mediated release from coated pellets.
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| 6. |
- Andersson, Helene, 1983
(författare)
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Structure control by phase separation and influence on mass transport in films for controlled release
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Controlled release coatings for oral pharmaceutics are often made of cellulose derivatives. Such coatings can be used to promote a prolonged therapeutic concentration in the blood by a slow drug delivery in the gastrointestinal tract. Furthermore, two polymers with different solubilities can be used in the same coating to give the desirable release characteristics. If a water-soluble polymer is present in the film this polymer can leak out from the coating and form pores that mediate drug release. In this thesis, specific focus has been aimed at films made from the water-insoluble ethyl cellulose (EC) and the water-soluble hydroxypropyl cellulose (HPC). Although EC and HPC can be co-dissolved in ethanol they tend to phase-separate during the spray-coating process, which results in distinct domains enriched in one polymer and depleted in the other. Due to this, the HPC-rich phase can serve as a template for the pores. Since phase separation is affected by the physicochemical properties of the polymers, the microstructure is likely to be affected as well. This in turn could influence drug release. Therefore, structure control is important for controlled mass transport through the films. The major aim was to investigate how different molecular weight (Mw) grades of the two cellulose derivative affects the film microstructures and mass transport properties in order to better understand the structure-release relation. The EC/HPC films produced contained 30% w/w HPC using different Mw grades of either EC or HPC while keeping the other polymer fixed. In general, combined studies on both sprayed films, cast films and pellet coatings showed that the final structure can be shifted from a percolating bicontinuous structure to disconnected HPC-rich domains by use of different Mw grades. Disconnected domains will prevent extensive leakage of HPC and formation of pores, resulting in overall low film permeability. However, by the use of more rapid drying conditions this morphology can be changed to a more bicontinuous structure, which both increases the total polymer release and film permeability. On the other hand, when very rapid drying conditions are used, leading to an early arrest in phase separation and very small domains, this can also prevent HPC release and decrease the mass transfer rate through films. Decreasing film permeability was found for both freestanding sprayed films and pellet coatings with increasing Mw of EC. On the other hand, when different Mw grades of HPC were used, sprayed free films showed an optimum in water permeability in the middle Mw range and very low permeability for films with low Mw HPC. Moreover, a slow release rate of HPC was achieved by using a high Mw grade of HPC, which also caused a slow increase in permeability. The drug release behaviour from coated pellets was, however, very different. This was believed to be due to different manufacturing conditions for spraying of free films and pellet coatings, as well as differences in the evolution of the phase-separated structure for systems of EC/HPC with different Mw grades. Overall, it was concluded that the Mw grade used in the films affects the phase-separated structure and in turn the geometries and percolation of pores, which will influences the overall mass transport properties of film. In addition, the effect of manufacturing conditions will much depend on the Mw grades used. Therefore, combining the effects of the Mw and the manufacturing conditions can be useful as a tool for controlling structure formation and mass transport in films.
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| 7. |
- Andersson, Helene, 1983, et al.
(författare)
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The influence of the molecular weight of the water-soluble polymer on phase-separated films for controlled release
- 2016
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Ingår i: International Journal of Pharmaceutics. - : Elsevier BV. - 0378-5173 .- 1873-3476. ; 511:1, s. 223-235
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Tidskriftsartikel (refereegranskat)abstract
- Hydroxypropyl cellulose (HPC) and ethyl cellulose (EC) can be used for extended release coatings, where the water-soluble HPC may act as a pore former. The aim was to investigate the effect of the molecular weight of HPC on the microstructure and mass transport in phase-separated freestanding EC/HPC films with 30% w/w HPC. Four different HPC grades were used, with weight averaged molecular weights (Mw) of 30.0 (SSL), 55.0 (SL), 83.5 (L) and 365 (M) kg/mol. Results showed that the phase-separated structure changed from HPC-discontinuous to bicontinuous with increasing Mw of HPC. The film with the lowest Mw HPC (SSL) had unconnected oval-shaped HPC-rich domains, leaked almost no HPC and had the lowest water permeability. The remaining higher Mw films had connected complex-shaped pores, which resulted in higher permeabilities. The highest Mw film (M) had the smallest pores and very slow HPC leakage, which led to a slow increase in permeability. Films with grade L and SL released most of their HPC, yet the permeability of the L film was three times higher due to greater pore connectivity. It was concluded that the phase-separated microstructure, the level of pore percolation and the leakage rate of HPC will be affected by the choice of HPC Mw grade used in the film and this will in turn have strong impact on the film permeability.
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| 8. |
- Bergstrand, Anna, 1974, et al.
(författare)
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Preparation of Porous Poly(3-Hydroxybutyrate) Films by Water-Droplet Templating
- 2012
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Ingår i: Journal of Biomaterials and Nanobiotechnology. - : Scientific Research Publishing, Inc.. - 2158-7027 .- 2158-7043. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- Porous resorbable implants are of great interest since they may deliver bioactives or drugs, facilitate the transport of body fluids or degradation products and provide a favorable environment for cell attachment and growth. In this work we report on a method using concentrated emulsions to template interconnected solid foam materials and to produce highly porous poly(3-hydroxybutyrate) (PHB) materials. Porous PHB films were cast made from water-in-oil template emulsions including Span 80 and lithium sulphate. The films were characterized by SEM-EDX and DMA. The water uptake of the films was recorded in order to determine the fraction water available pores. The results show that the ad-dition of lithium sulphate allows a fine tuning of the film morphology with respect to porosity and interconnected po-rous structure. The film porosity was determined to 51% ± 3%, 52% ± 3% and 45% ± 3% for the films made with 0%, 2.9% and 14.3% lithium sulphate in the template emulsion, respectively. The fraction water available pores was sig-nificantly lower, 11% ±3%, 38% ±12% and 48% ± 7% for films with 0%, 2.9% and 14.3% litium sulphate respectively. Differences in fraction water available pores and total porosity for the films reflects the film morphology and differ-ences in pore interconnection.
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| 9. |
- Häbel, Henrike, 1987, et al.
(författare)
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Characterization of pore structure of polymer blended films used for controlled drug release
- 2016
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Ingår i: Journal of Controlled Release. - : Elsevier BV. - 0168-3659 .- 1873-4995. ; 222, s. 151-158
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Tidskriftsartikel (refereegranskat)abstract
- The characterization of the pore structure in pharmaceutical coatings is crucial for understanding and controlling mass transport properties and function in controlled drug release. Since the drug release rate can be associated with the film permeability, the effect of the pore structure on the permeability is important to study. In this paper, a new approach for characterizing the pore structure in polymer blended films was developed based on an image processing procedure for given two-dimensional scanning electron microscopy images of film cross-sections. The focus was on different measures for characterizing the complexity of the shape of a pore. The pore characterization developed was applied to ethyl cellulose (EC) and hydroxypropyl cellulose (HPC) blended films, often used as pharmaceutical coatings, where HPC acts as the pore former. It was studied how two different HPC viscosity grades influence the pore structure and, hence, mass transport through the respective films. The film with higher HPC viscosity grade had been observed to be more permeable than the other in a previous study; however, experiments had failed to show a difference between their pore structures. By instead characterizing the pore structures using tools from image analysis, statistically significant differences in pore area fraction and pore shape were identified. More specifically, it was found that the more permeable film with higher HPC viscosity grade seemed to have more extended and complex pore shapes than the film with lower HPC viscosity grade. This result indicates a greater degree of connectivity in the film with higher permeability and statistically confirms hypotheses on permeability from related experimental studies.
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| 10. |
- Marklund, Emelie, et al.
(författare)
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Serum-IgG responses to SARS-CoV-2 after mild and severe COVID-19 infection and analysis of IgG non-responders.
- 2020
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Ingår i: PloS one. - : Public Library of Science (PLoS). - 1932-6203. ; 15:10
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Tidskriftsartikel (refereegranskat)abstract
- To accurately interpret COVID-19 seroprevalence surveys, knowledge of serum-IgG responses to SARS-CoV-2 with a better understanding of patients who do not seroconvert, is imperative. This study aimed to describe serum-IgG responses to SARS-CoV-2 in a cohort of patients with both severe and mild COVID-19, including extended studies of patients who remained seronegative more than 90 days post symptom onset.SARS-CoV-2-specific IgG antibody levels were quantified using two clinically validated and widely used commercial serological assays (Architect, Abbott Laboratories and iFlash 1800, YHLO), detecting antibodies against the spike and nucleocapsid proteins.Forty-seven patients (mean age 49 years, 38% female) were included. All (15/15) patients with severe symptoms and 29/32 (90.6%) patients with mild symptoms of COVID-19 developed SARS-CoV-2-specific IgG antibodies in serum. Time to seroconversion was significantly shorter (median 11 vs. 22 days, P = 0.04) in patients with severe compared to mild symptoms. Of the three patients without detectable IgG-responses after >90 days, all had detectable virus-neutralizing antibodies and in two, spike-protein receptor binding domain-specific IgG was detected with an in-house assay. Antibody titers were preserved during follow-up and all patients who seroconverted, irrespective of the severity of symptoms, still had detectable IgG levels >75 days post symptom onset.Patients with severe COVID-19 both seroconvert earlier and develop higher concentrations of SARS-CoV-2-specific IgG than patients with mild symptoms. Of those patients who not develop detectable IgG antibodies, all have detectable virus-neutralizing antibodies, suggesting immunity. Our results showing that not all COVID-19 patients develop detectable IgG using two validated commercial clinical methods, even over time, are vital for the interpretation of COVID-19 seroprevalence surveys.
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