| 1. |
- Brännvall, Karin, et al.
(författare)
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Enhanced neuronal differentiation in a three-dimensional collagen-hyaluronan matrix
- 2007
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Ingår i: Journal of Neuroscience Research. - : Wiley. - 0360-4012 .- 1097-4547. ; 85:10, s. 2138-2146
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Tidskriftsartikel (refereegranskat)abstract
- Efficient 3D cell systems for neuronal induction are needed for future use in tissue regeneration. In this study, we have characterized the ability of neural stem/progenitor cells (NS/PC) to survive, proliferate, and differentiate in a collagen type I-hyaluronan scaffold. Embryonic, postnatal, and adult NS/PC were seeded in the present 3D scaffold and cultured in medium containing epidermal growth factor and fibroblast growth factor-2, a condition that stimulates NS/PC proliferation. Progenitor cells from the embryonic brain had the highest proliferation rate, and adult cells the lowest, indicating a difference in mitogenic responsiveness. NS/PC from postnatal stages down-regulated nestin expression more rapidly than both embryonic and adult NS/PC, indicating a faster differentiation process. After 6 days of differentiation in the 3D scaffold, NS/PC from the postnatal brain had generated up to 70% neurons, compared with 14% in 2D. NS/PC from other ages gave rise to approximately the same proportion of neurons in 3D as in 2D (9-26% depending on the source for NS/PC). In the postnatal NS/PC cultures, the majority of III-tubulin-positive cells expressed glutamate, -aminobutyric acid, and synapsin I after 11 days of differentiation, indicating differentiation to mature neurons. Here we report that postnatal NS/PC survive, proliferate, and efficiently form synapsin I-positive neurons in a biocompatible hydrogel.
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| 2. |
- Friedman, Mikaela, et al.
(författare)
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Engineering and characterization of a bispecific HER2 x EGFR-binding affibody molecule
- 2009
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Ingår i: Biotechnology and applied biochemistry. - 0885-4513 .- 1470-8744. ; 54, s. 121-131
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Tidskriftsartikel (refereegranskat)abstract
- HER2 (human epidermal-growth-factor receptor-2; ErbB2) and EGFR (epidermal-growth-factor receptor) are overexpressed in various forms of cancer, and the co-expression of both HER2 and EGFR has been reported in a number of studies. The simultaneous targeting of HER2 and EGFR has been discussed as a strategy with which to potentially increase efficiency and selectivity in molecular imaging and therapy of certain cancers. In an effort to generate a molecule capable of bispecifically targeting HER2 and EGFR, a gene fragment encoding a bivalent HER2-binding affibody molecule was genetically fused in-frame with a bivalent EGFR-binding affibody molecule via a (G(4)S)(3) [(Gly(4)-Ser)(3)]-encoding gene fragment. The encoded 30 kDa affibody construct (Z(HER2))(2)-(G(4)S)(3)-(Z(EGFR))(2), with potential for bs (bispecific) binding to HER2 and EGFR, was expressed in Escherichia coli and characterized in terms of its binding capabilities. The retained ability to bind HER2 and EGFR separately was demonstrated using both biosensor technology and flow-cytometric analysis, the latter using HER2- and EGFR-overexpressing cells. Furthermore, simultaneous binding to HER2 and EGFR was demonstrated in: (i) a sandwich format employing real-time biospecific interaction analysis where the bs affibody molecule bound immobilized EGFR and soluble HER2; (ii) immunofluorescence microscopy, where the bs affibody molecule bound EGFR-overexpressing cells and soluble HER2; and (iii) a cell-cell interaction analysis where the bs affibody molecule bound HER2-overexpressing SKBR-3 cells and EGFR-overexpressing A-431 cells. This is, to our knowledge, the first reported bs affinity protein with potential ability for the simultaneous targeting of HER2 and EGFR. The potential future use of this and similar constructs, capable of bs targeting of receptors to increase the efficacy and selectivity in imaging and therapy, is discussed.
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| 3. |
- Jenei, István Zoltán, et al.
(författare)
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Correlation Studies of WS2 Fullerene-Like Nanoparticles Enhanced Tribofilms : A Scanning Electron Microscopy Analysis
- 2013
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Ingår i: Tribology letters. - : Springer Science and Business Media LLC. - 1023-8883 .- 1573-2711. ; 51:3, s. 461-468
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Tidskriftsartikel (refereegranskat)abstract
- The beneficiary effects of tungsten disulphide (WS2) inorganic fullerene-like nanoparticles (IFLNPs) in the lubrication industry were shown in recent years. However, their successful incorporation into lubricants (oils, greases) is not straightforward. In practice, the lubricant contains several components for different purposes, e.g. reducing the oxidization of the oil (antioxidant), minimizing the wear rate (anti-wear additive), dispersants, etc. These additives can contain chemically active compounds, which under the lubrication process (where locally extreme conditions can develop: high pressure and flash temperatures) can change the chemistry in the contact zone and block the beneficial effects of the inorganic nanoparticles. In this investigation, poly-alpha-olefin (PAO) is being used as base oil in which the WS2 nanoparticles and different additives are mixed. A ball-on-disc sliding test revealed that certain additives inhibit the nanoparticles to reduce friction (less than 5 % decrease in friction coefficient), while in other cases, the friction reduction was above 50 %. The comparison is being made between PAO + additive and PAO + additive + IFLNPs. Scanning electron microscope and energy dispersive X-ray spectroscopy were used to investigate the elemental composition of the tribofilms formed on the wear marks. Further analysis was made in order to reveal correlations between elemental compositions of the tribofilms and external parameters such as the friction coefficient and wear rate. For instance, a strong correlation between tungsten content of the tribofilm and the friction coefficient was found.
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| 4. |
- Lindholm, Per, et al.
(författare)
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Method and surface roughness aspects for the design of DLC coatings
- 2006
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Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 261:1, s. 107-111
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Tidskriftsartikel (refereegranskat)abstract
- The design of coatings for highly loaded component contacts, such as bearings, gears and valve train components involves several important factors, including load, friction, lubrication, surface characteristics and material parameters. This paper presents an investigation of the influence of the material, coating thickness and surface roughness on tensional stress levels for coatings that are more compliant than the substrate material. Specifically the effect of multiple asperity contact is studied in three dimensions. The simulation is based on a finite element model where the load is applied as several interacting Hertzian pressure distributions. The results show that the surface structure, in combination with the elastic properties of the coating, has a large influence on the tensional stress level in the coating. The highest tensional stress level in the coating occurs when contact spots almost overlap neighbouring cells and at the same time the size of the contact spots is in the same order of magnitude as the coating thickness.
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| 5. |
- Loos, Robert, et al.
(författare)
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Summary recommendations on “Analytical methods for substances in the Watch List under the Water Framework Directive”
- 2023
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Ingår i: Science of the Total Environment. - : Elsevier. - 0048-9697 .- 1879-1026. ; 912
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Tidskriftsartikel (refereegranskat)abstract
- The Watch List (WL) is a monitoring program under the European Water Framework Directive (WFD) to obtain high-quality Union-wide monitoring data on potential water pollutants for which scarce monitoring data or data of insufficient quality are available. The main purpose of the WL data collection is to determine if the substances pose a risk to the aquatic environment at EU level and subsequently to decide whether a threshold, the Environmental Quality Standards (EQS) should be set for them and, potentially to be listed as priority substance in the WFD. The first WL was established in 2015 and contained 10 individual or groups of substances while the 4th WL was launched in 2022. The results of monitoring the substances of the first WL showed that some countries had difficulties to reach an analytical Limit of Quantification (LOQ) below or equal to the Predicted No-Effect Concentrations (PNEC) or EQS. The Joint Research Centre (JRC) of the European Commission (EC) organised a series of workshops to support theEU Member States (MS) and their activities under the WFD. Sharing the knowledge among the Member States on the analytical methods is important to deliver good data quality. The outcome and the discussion engaged with the experts are described in this paper, and in addition a literature review of the most important publications on the analysis of 17-alpha-ethinylestradiol (EE2), amoxicillin, ciprofloxacin, metaflumizone, fipronil, metformin, and guanylurea from the last years is presented.
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| 6. |
- Svahn, Fredrik, et al.
(författare)
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Formation of Low-Friction Particle/Polymer Composite Tribofilms by Tribopolymerization
- 2011
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Ingår i: Tribology letters. - : Springer Science and Business Media LLC. - 1023-8883 .- 1573-2711. ; 41:2, s. 387-393
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Tidskriftsartikel (refereegranskat)abstract
- Inorganic fullerene-like (IF) solid lubricant particles based on MoS(2) or WS(2) have recently gained attention in various tribological applications, for instance incorporated in coatings, porous materials, greases and dispersed in oils. However, their effect in oil can be limited often due to inadequate penetration into the contact zone. Meanwhile, tribopolymerization of monomer additives in oil have proven to be efficient to reduce wear, but without significantly reducing the friction. This investigation combines these two lubrication techniques in order to form particle/polymer composite tribofilms, aimed to give low friction and wear in high-pressure sliding contacts. A cyclic amine, caprolactam, was used as the monomer together with IF as well as normal 2H WS(2) particles. Zn-DTP was used as a reference antiwear additive and poly-alfa-olefin (PAO) was used as the base oil. Reciprocal ball-on-flat sliding test results found that monomer plus particles reduced the friction by 10-50%, depending on sliding speed and type of particles, compared with particles or monomer alone. And the scattering between different tests was also considerably lower. The wear rate was also substantially reduced to a level similar to that of Zn-DTP. The particle/polymer composite tribofilms were generally much larger than the actual contact area and its thickness varied from below a few nanometres in the contact centre to several micrometers in the outer parts. Consequently, the reduced friction is believed to come from two effects: one being a trapping of particles in the contact zone, which reduces the boundary friction level; and the other a shift in lubrication regime towards EHD-lubrication due to reduced contact pressures accompanied with the formation of the composite tribofilm.
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| 7. |
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| 8. |
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| 9. |
- Svahn, Ola, et al.
(författare)
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Assessment of full-scale 4th treatment step for micro pollutant removal in Sweden : Sand and GAC filter combo
- 2023
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Ingår i: Science of the Total Environment. - : Elsevier. - 0048-9697 .- 1879-1026. ; 906
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Tidskriftsartikel (refereegranskat)abstract
- This study focuses on the 4th treatment step in Degeberga WWTP treatment plant, the first full scale GAC filter in Sweden installed in April 2020 for removal of micropollutants. The two GAC filters, containing two different carbon types, has operated flawlessly for three years (30,000 bed volumes) without requiring backwashing. The results indicate that the sand filter provides effective protection to the carbon filters, preventing solids from reaching the carbon and reducing the growth of organic matter. Additionally substantial biodegradation was observed for several substances. During the first year of operation, the two filters (at 8500 and 5700 bed volumes respectively) achieved >98 % removal of 24 substances. By the end of the second year (at 19,000 and 12,600 bed volumes respectively), fluconazole and sulfamethoxazole broke through completely, and the number of compounds below 80 % removal increased. The average removal of micro pollutants decreased over time. Compounds with positive charges generally exhibited higher adsorption capacities, while negatively charged compounds had lower removals. On average the investigated 24 compounds was removed by 89 % in the 4th treatment step over three years. The study suggests that biodegradation may contribute to the removal of some micropollutants in GAC filters, similar to observations made in the sand filter. Both Swiss and suggested EU regulations aim for at least an 80 % removal in micropollutant concentration. The study evaluated the performance of the filters based on this guideline and the presented technique is after a total of eight years of investigation and evaluation a proven performer. Overall, the 4th treatment combination of sand and GAC filters in WWTPs has shown promising results in removing organic micropollutants, addressing the need for efficient treatment strategies targeting these emerging pollutants. Degeberga WWTP serves as an example of successful implementation of advanced treatment for improving water quality and protecting human and aquatic health.
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| 10. |
- Svahn, Stefan, 1977-
(författare)
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Analysis of Secondary Metabolites from Aspergillus fumigatus and Penicillium nalgiovense : Antimicrobial Compounds from Filamentous Fungi Isolated from Extreme Environments
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis describes the cultivation and extraction of filamentous fungi isolated from extreme environments in the search for new antibiotic compounds. Filamentous fungi are a rich source of medicines including antibiotics, and it is believed that many currently unknown fungal species and bioactive fungal metabolites remain to be discovered.Aspergillus fumigatus and Penicillium nalgiovense strains were isolated from an antibiotic-contaminated riverbed near Hyderabad, India, and soil taken from a penguin’s nest on Paulete Island, Antarctica, respectively. It was anticipated that the extreme conditions within these environments would exert unusual selective pressures on their filamentous fungi, possibly causing the secretion of new bioactive compounds.The cultivation, extraction and analysis of metabolites from the A. fumigatus strain resulted in the isolation of the antimicrobial substance gliotoxin. Subsequent investigations revealed that this strain’s secretion of gliotoxin was increased by as much as 65 % when it was cultivated in the presence of pathogen-associated molecular patterns. These results indicate the existence of a fungal receptor/signaling system for detecting nearby bacteria. The scope for using gliotoxin and the related metabolite bis(methyl)gliotoxin as biomarker metabolites for diagnosing the lethal pulmonary condition invasive aspergillosis was also investigated. Bronchoalveolar lavage fluid from 42 patients with and without possible invasive aspergillosis was extracted and analyzed. The results obtained suggest that gliotoxin and bis(methyl)gliotoxin are not suitable markers for diagnosing invasive aspergillosis.Studies on the P. nalgiovense strain from Antarctica resulted in the isolation of the antifungal agent amphotericin B. The secretion of this compound increased when P. nalgiovense was cultured on a potato-dextrose agar enriched with coconut flakes rather than liquid RPMI 1640 medium. This was the first time amphotericin B was isolated from any organism other than the bacterium Streptomyces nodosus.The results presented in this thesis will be useful in the continuing search for novel bioactive compounds, the diagnosis of fungal infections, and as a source of insight into the interactions between microorganisms. Moreover, they show that even extensively studied fungal genera such as Aspergillus and Penicillium are not completely understood and may produce unexpected or previously unknown bioactive metabolites under appropriate conditions.
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