| 41781. |
- Karlsson, Jonas, 1974
(författare)
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Detection of Biomolecules: Syntheses and Studies of Minor Groove Binding Unsymmetrical Cyanine Dyes and Chromogenic Enzyme Substrates
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Visualisation or detection of biomolecules is usually achieved by the use of fluorescent or highly coloured chromophores. The work presented in this thesis deals with the development of new chromogenic substrates for the detection of enzyme activity, and new DNA-binding fluorescent dyes for staining of DNA. Paper I reports on the syntheses and studies of new indolyl acetates for chromogenic detection of esterase activity. The main advantages of these new compounds are that they can detect activity at longer wavelengths and with larger shifts in absorption upon enzymatic action compared to the commonly used p-nitrophenyl acetate. In Papers II-VI, syntheses and DNA-binding studies of new crescent-shaped unsymmetrical cyanine dyes are described. Some of these dyes were shown by optical spectroscopy to exhibit a large preference for binding in the minor groove of natural DNA. Different facile synthetic routes have been developed to obtain these dyes, involving either palladium-catalysed cross-couplings or various cyclisation reactions. Similarly to the widely used intercalating unsymmetrical cyanine dyes, the minor groove binding dyes demonstrate a large enhancement in fluorescence intensity upon binding to DNA. It is shown that the extent of minor groove binding to mixed sequence DNA varies significantly between the dyes, depending on the nature of the heteroaromatic groups. The results suggest that hydrophobicity and size are the crucial parameters for recognition of the minor groove of this type of dyes. In Paper IV it is shown that the groove-bound dyes dissociate more slowly and exhibit a reduced sensitivity to ionic strength compared to corresponding intercalating dyes. Finally, one of the dyes, BEBO, has been compared to SYBR Green I as a reporter dye in real time PCR and was shown to behave similarly in all important aspects.
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| 41782. |
- Karlsson, Jakob, 1997, et al.
(författare)
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Effect of heating of pea fibres on their swelling, rheological properties and in vitro colon fermentation
- 2024
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Ingår i: Food Hydrocolloids. - : Elsevier. - 0268-005X .- 1873-7137. ; 147
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Tidskriftsartikel (refereegranskat)abstract
- Dietary fibre intake is essential for all human beings and has been correlated to beneficial health effects. Pea hull fibres (PF) are generally seen as a side stream during extraction of protein and starch from yellow pea but could be used in various food products to boost fibre content. In this study, the thermal treatment of pea hull fibres was investigated in terms of physicochemical properties and in vitro colonic fermentation. The PF that was subjected to heating showed an increase of fibres solubilised in the liquid and particle size. Results also showed that viscosity and storage modulus increased with thermal treatment, possibly due to the swelling of the PF. The pea fibre was readily fermentable based on total gas production and pH. However, the susceptibility to fermentation of PF did not increase with thermal treatment. Total gas production and short chain fatty acid produced were similar independent of thermal treatment. Conclusively, heating of the PF resulted in increased ability to structure water suspension, owing to increased fibre particle size, but is not sufficient to increase short chain fatty acid production during colonic fermentation. To explain this, we propose that the changes in cell wall structure were not major enough to induce higher fermentability.
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| 41783. |
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| 41784. |
- Karlsson, Johannes, 1990, et al.
(författare)
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Energy Distribution Diagram Used for Cost-Effective Battery Sizing of Electric Trucks
- 2023
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Ingår i: Energies. - : MDPI AG. - 1996-1073 .- 1996-1073. ; 16:2
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Tidskriftsartikel (refereegranskat)abstract
- One possible step for reducing humans’ use of fossil fuel due to transport tasks is to replace diesel trucks with battery electric ones. This paper introduces the energy distribution diagram, which makes it easy to visualise the trucks’ daily energy consumption over their full service life. The energy distribution is used to investigate which driving patterns are suitable for cost-effective battery electric trucks when compared to commercial diesel trucks. It is shown that the battery capacity that results in the lowest cost per kilowatt-hour propulsion energy depends on the driving pattern, and an algorithm for selecting the most cost-effective capacity is presented. In many instances, it was found that battery electric trucks competed favourably with diesel trucks, especially when the trucks had low variations in daily energy consumption. It is beneficial to determine the circumstances under which they may be cheaper, as this will facilitate the transition to battery electric trucks in segments with a reduced overall cost of ownership.
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| 41785. |
- Karlsson, Johan, 1984, et al.
(författare)
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Ex vivo alendronate localization at the mesoporous titania implant/bone interface
- 2015
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Ingår i: Journal of materials science. Materials in medicine. - : Springer Science and Business Media LLC. - 1573-4838 .- 0957-4530. ; 26
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Tidskriftsartikel (refereegranskat)abstract
- An attractive approach in implant technology is local drug delivery, and design of efficient, safe and reliable treatments. Ourhitherto strategy has been to coat Ti implants with a thin mesoporous TiO2 film that in turnis loaded with an osteoporosis drug, such as Alendronate (ALN) that is known to suppress osteoclastic activity. This system has proven highly successful and results in excellent osseointegration. However, more detailed information about drug-release and distribution at the bone/implant interface is needed. In this study, (14)C-ALN loaded titanium implants were placed up to 8weeks into rat tibia and the spatial-temporal distribution of the drug was evaluated. Autoradiography data demonstrated a sustained release of (14)C-ALN and the releaseddrug remained bound to bone in close vicinity, within 500 micrometers,of the implants. Liquid scintillation counting experiments confirmed that the distal transport of released (14)C-ALN was extremely low. The results are favorable as they show that ALN stays for a long time in the vicinity of the implant and may therefore improve for a long time the mechanical fixation of bone anchored implants. Moreover, these findings suggest due to the low systemic spreading a minimal risk of Alendronate related systemic side effects.
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| 41786. |
- Karlsson, Jakob, 1997
(författare)
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Exploring Physico-Chemical Properties and Colonic Fermentation of Pea Hull Fibre and Pea Protein Blends
- 2023
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Yellow pea (Pisum sativum L.) is a legume with high protein and dietary fibre content commonly used for human consumption. Yellow pea is consumed as it is but also used as part of food products, in form of protein concentrate, protein isolate, dietary fibre etc. The digestion and colon fermentation of ingested foods are dependent on factors, such as composition and interaction of macromolecules. Knowledge about how more complex mixtures of plant-based nutrients changes due to processing and how it affects colon fermentation are lacking. The aim of this thesis is to study pea hull fibre and pea protein blends and determine the effect of compositional differences and thermal treatment to in vitro colonic fermentation. Rheology, microscopy, and zeta potential measurements were used to study technical function of pea hull fibre and pea protein blends. The fermentation products of the pea hull fibre and protein were studied using in vitro colonic fermentation, with determination of pH reduction, gas production and short chain fatty acid formation. Chemical characterisation of the pea fibres was determined using high performance anion exchange chromatography and uronic acid assay. Variables used in the study was ratio of fibre and protein, thermal exposure, and pH. Pea hull fibre content was dominated by glucose and uronic acid, believed to originate from cellulose and pectin like polysaccharides. Pea hull fibres and pea protein were largely insoluble, and the fibre particles were observed to be larger in size (98.4 μm) than the protein particles (19.2 μm). Thermal treatment (exposure at 95 ˚C for 30 minutes) of fibre and protein blends increased the storage modulus of the single components as well as their blends. The increase in storage modulus is attributed to swelling of particles, and not release of solubilised polysaccharides. The in vitro colonic fermentation experiment showed that the products formed from the fibre and protein blends were affected by the ratio of fibre and protein. Treatment with heating only lead to small differences in the fermentation outcome. The results show that fibre and protein composition did affect rheological and in vitro fermentation outcome, but also highlights that changes can be observed due to thermal treatment.
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| 41787. |
- Karlsson, Jan, 1967
(författare)
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Fiber-Supported Hydrogels with Controlled surface Properties
- 1998
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Hydrogels are emerging materials that have the ability to hold a substantial amount of water. However, the low mechanical performance of hydrogels is often a limitation for extending the field of applications. This thesis describes the preparation and characterization of a new generation of materials that combines the benefits of hydrogels with the mechanical performance of fibers. In the present work, cellulose and PP-supported hydrogels were prepared by means of an ozone-induced graft polymerization process. The work focused on engineering and controlling surface properties such as the wettability and morphology as well as the swelling and environmental response of the hybrid materials. Materials were engineered by changing the ozonation and grafting conditions as well as the chemical composition of the monomer mixture. The techniques used for characterization were chiefly ESCA, DCA, SEM, ESEM and AFM. It was demonstrated that it was possible to prepare fiber-supported hydrogels with controlled wettability by graft polymerization of HEMA, DEGMA and TEGMA onto PP and cellulose. Angle-dependent ESCA measurements showed that a gradient in chemical composition existed in the near-surface region. DEGMA and TEGMA-grafted PP fibers exhibited a less pronounced contact angle hysteresis in water as compared with HEMA-grafted fibers. Both these observations can be explained by the mobility of functional groups in the outermost surface layer. It was possible to control the amount of grafted polymer on cellulose fibers by adding a small amount of bifunctional crosslinking agent to the monomer mixture used for grafting. A mechanism for the grafting enhancement is proposed. An increased yield of grafting resulted in a coverage of the cellulose fibers and, when certain monomers were used, surface microstructures were formed. It was possible to influence the appearance of the microstructure by controlling the grafting yield. pH-sensitive solid-supported hydrogels were prepared by graft polymerization of acrylic acid onto cellulose fibers. Crosslinking of the solid-supported hydrogels affected the grafting amount and resulted in a reversible swelling behavior of the fibers. DCA measurements showed substantial changes in the swelled perimeter in test liquids with various pH values. This work shows that controlled graft polymerization results in the ability to prepare a new generation of engineered materials. Abbreviations: HEMA 2-hydroxyethyl methacrylate ESCA electron spectroscopy for chemical analysis DEGMA diethyleneglycol methacrylate DCA dynamic contact angle TEGMA triethyleneglycol methacrylate (E)SEM (environmental) scanning electron microscopy PP polypropylene AFM atomic force microscopy
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| 41788. |
- Karlsson, Jonas, 1989, et al.
(författare)
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Implementation of Anisotropic Mesh Refinement in OpenFOAM
- 2012
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Ingår i: 15th Numerical Towing Tank Symposium.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Researchers and engineers practicing Computational Fluid Dynamics (CFD) have over the years gained a lot of experience on how to design good computational meshes. Nevertheless, for a general hull shape it is impossible to a priori know the resolution and exact design of the coarsest mesh required to obtain a certain computational accuracy. Here, the use of self-adapting schemes becomes vital. There are several methods to design self-adapting schemes. By far the most popular method is Adaptive Mesh Refinement (AMR) where the mesh is refined by adding cell points in order to split cells and reduce cell size.
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| 41789. |
- Karlsson, Johan, 1984, et al.
(författare)
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In vivo biomechanical stability of osseointegrating mesoporous TiO2 implants
- 2012
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Ingår i: Acta Biomaterialia. - : Elsevier BV. - 1878-7568 .- 1742-7061. ; 8:12, s. 4438-4446
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Tidskriftsartikel (refereegranskat)abstract
- Mesoporous materials are of high interest as implant coatings to receive an enhanced osseointegration. In this study, titanium implants coated with mesoporous TiO(2) thin films have been evaluated both in vitro and in vivo. Material characterization showed that, with partly crystalline TiO(2) (anatase), long-range-ordered hydrophilic mesoporous thin films with a pore size of 6nm were obtained. Evaluation of the mechanical resistance showed that the films were robust enough to withstand the standard implantation procedure. In vitro apatite formation was studied using simulated body fluids, showing that the pores are accessible for ions and that formation of apatite was increased due to the presence of the mesopores. An in vivo study using a rabbit model was executed in which the removal torque and histomorphometry were evaluated. The results show that the biomechanical stability of the TiO(2) coating was unaffected by the presence of mesopores and that osseointegration was achieved without any signs of inflammation.
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| 41790. |
- Karlsson, Johan, 1991, et al.
(författare)
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Intersection crossing with reduced number of conflicts
- 2018
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Ingår i: IEEE Conference on Intelligent Transportation Systems, Proceedings, ITSC. ; , s. 1993-1999
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Konferensbidrag (refereegranskat)abstract
- In this paper, an optimization based algorithm for safe and efficient collaborative driving in intersections is formulated. The problem is to determine the optimal order in which vehicles should travel through an intersection under the assumptions that the longitudinal velocity of all vehicles can be controlled along a predefined path. In the original formulation one quadratic optimization program was solved for each possible crossing order of the vehicles and collisions were avoided by formulating constraints that only allowed one vehicle at the time inside the intersection. To make this algorithm more effective, we formulate less restrictive collision avoidance constraints by introducing one critical zone for each point where two predefined paths cross. It is shown that this formulation leads to a decrease in the number of quadratic optimization programs that need to be solved to find the best crossing order. Further, an algorithm is provided that finds the number of crossing sequences which yield unique formulations of the optimization program. The results show that when simulating more complex scenarios, like four vehicles traveling through an ordinary intersection, the reduction of computational time and the total time it takes for all vehicles to make it through the intersection can be significantly reduced using these less restrictive constraints.
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