| 1. |
- Aarstad, Olav, et al.
(författare)
-
Mechanical properties of composite hydrogels of alginate and cellulose nanofibrils
- 2017
-
Ingår i: Polymers. - : MDPI AG. - 2073-4360. ; 9:8
-
Tidskriftsartikel (refereegranskat)abstract
- Alginate and cellulose nanofibrils (CNF) are attractive materials for tissue engineering and regenerative medicine. CNF gels are generally weaker and more brittle than alginate gels, while alginate gels are elastic and have high rupture strength. Alginate properties depend on their guluronan and mannuronan content and their sequence pattern and molecular weight. Likewise, CNF exists in various qualities with properties depending on, e.g., morphology and charge density. In this study combinations of three types of alginate with different composition and two types of CNF with different charge and degree of fibrillation have been studied. Assessments of the composite gels revealed that attractive properties like high rupture strength, high compressibility, high gel rigidity at small deformations (Young’s modulus), and low syneresis was obtained compared to the pure gels. The effects varied with relative amounts of CNF and alginate, alginate type, and CNF quality. The largest effects were obtained by combining oxidized CNF with the alginates. Hence, by combining the two biopolymers in composite gels, it is possible to tune the rupture strength, Young’s modulus, syneresis, as well as stability in physiological saline solution, which are all important properties for the use as scaffolds in tissue engineering.
|
|
| 2. |
- Andersson, N, et al.
(författare)
-
Structural features and adsorption behaviour of mesoporous silica particles formed from droplets generated in a spraying chamber
- 2004
-
Ingår i: Microporous and Mesoporous Materials. - 1387-1811 .- 1873-3093. ; 72, s. 175-183
-
Tidskriftsartikel (refereegranskat)abstract
- Spherical mesoporous particles have been produced by spraying hydrolysed alkoxide solutions containing templating amphiphilic molecules. The modified spray drying method produces up to 10 g/h of spherical non-hollow particles with a size of 1–5 m. Transmission electron microscopy and X-ray diffraction showed that well ordered internal 2D hexagonal mesostructures could be prepared using both nonionic block copolymers and cationic surfactants as the templating molecules. Disordered cubic and well ordered lamellar, onion like, particles were prepared from the block copolymer templates. Nitrogen sorption data and mercury porosimetry show that pore size distribution of the mesoporous particles is very narrow with pore sizes varying from 2.5 to 8.5 nm as a function of templating amphiphiles. We have shown that the mesoscopic pores are accessible after calcination and can be filled with relatively large molecules; the particles adsorbed more than 20% (by weight) of the cationic dye Janus Green B from aqueous solutions.
|
|
| 3. |
- Arleth, L., et al.
(författare)
-
Small-angle neutron scattering study of the growth behavior, flexibility, and intermicellar interactions of wormlike SDS micelles in NaBr aqueous solutions
- 2002
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 18:14, s. 5343-5353
-
Tidskriftsartikel (refereegranskat)abstract
- SDS wormlike micelles in water with NaBr are studied using small-angle neutron scattering. SDS concentrations ranging from 0.08 to 8.6 % vol in NaBr aqueous solutions at salinities from 0.6 to 1.0 M are covered. The scattering data are analyzed using a novel approach based on polymer theory and the results of Monte Carlo simulations. The method makes it possible to give a full interpretation of the scattering data, even for the entangled micellar solutions occurring at high concentrations and high salinities. Analysis of the scattering data at zero scattering angle demonstrates that the length of the micelles increases according to a power law as a function of concentration in the studied interval. The analysis furthermore shows that the length of the micelles increases exponentially with increasing salinity. The scattering data in the full range of scattering angles are analyzed using a model for polydisperse wormlike micelles where excluded volume effects are taken into account via an expression based on the polymer reference interaction site model (PRISM). This part of the analysis show that the micelles become more flexible as the salinity increases, which is due to an increased screening of the ionic micelles.
|
|
| 4. |
- Bergström, L, et al.
(författare)
-
Interparticle forces and rheological properties of ceramic suspensions
- 1999
-
Ingår i: Key Engineering Materials. - 1013-9826 .- 1662-9795. ; 159-160, s. 119-126.
-
Tidskriftsartikel (refereegranskat)abstract
- Dispersants have a profound influence on the suspension properties of ceramic slurries. We will illustrate the effect of polymers and polyelectrolytes on the colloidal stability and the rheological properties in both aqueous and non-aqueous media. We have related direct measurements of polymerically induced interparticle forces to the rheological properties of different ceramic systems. Simple estimates of the effective volume fractions of non-aqueous, polymerically stabilized silicon nitride suspensions gave a reasonable correspondence between calculated and measured polymer layer thicknesses. We show that PAA stabilize zirconia by an electrosteric mechanism; also, we found an excellent agreement between the presence of bridging attraction and poor colloidal stability at low surface coverage. In addition, the van der Waals forces have been quantified by theoretical calculations and direct measurements.
|
|
| 5. |
- Bergström, L. Magnus, et al.
(författare)
-
The growth of micelles, and the transition to bilayers, in mixtures of a single-chain and a double-chain cationic surfactant investigated with small-angle neutron scattering
- 2011
-
Ingår i: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-683X .- 1744-6848. ; 7:22, s. 10935-10944
-
Tidskriftsartikel (refereegranskat)abstract
- Self-assembly in aqueous mixtures of a single-chain (DTAB) and a double-chain cationic surfactant (DDAB) has been investigated with small-angle neutron scattering (SANS). Small oblate spheroidal micelles formed by DTAB grow with respect to width and length to form mixed ellipsoidal tablet-shaped micelles as an increasing fraction of DDAB is admixed into the micelles. The growth behaviour of the micelles is rationalized from the general micelle model in terms of three bending elasticity constants spontaneous curvature (H-0), bending rigidity (k(c)) and saddle-splay constant ((k(c)) over bar kc). It is found that micelles grow with respect to width, mainly as a result of decreasing k(c)H(0), and in the length direction as a result of decreasing k(c). The micelles are still rather small, i.e. about 140 angstrom in length, as an abrupt transition to large bilayer aggregates is observed. The micelle-to-bilayer transition is induced by changes in aggregate composition and is observed to occur at a mole fraction of DDAB equal to about x = 0.48 in D2O, which is a significantly higher value than previously observed for the same system in H2O (x = 0.41). An abrupt micelle-to-bilayer transition is in agreement with predictions from the general micelle model, according to which an abrupt transition from micelles to bilayers is expected to occur at xi H-0 = 1/4, where x is the thickness of the self-assembled interface, and we may conclude that H-0(D2O) > H-0(H2O) for the system DDAB/DTAB in absence of added salt. Samples with bilayers are found to be composed of bilayer disks coexisting with vesicles. Disks are found to always predominate over vesicles with mass fractions about 70-90% disks and 10-30% vesicles. Micelles, disks and vesicles are observed to coexist in a few samples close to the micelle-to-bilayer transition.
|
|
| 6. |
- Callesen, Gustav, et al.
(författare)
-
Recycling Nutrients and Reducing Carbon Emissions in the Baltic Sea Region—Sustainable or Economically Infeasible?
- 2022
-
Ingår i: Environmental Management. - : Springer. - 0364-152X .- 1432-1009. ; 69:1, s. 213-225
-
Tidskriftsartikel (refereegranskat)abstract
- Ecotechnologies have the potential to reduce the use of finite resources while providing a variety of co-benefits to society, though they often lack in market competitiveness. In this study, we investigate the sustainability of ecotechnologies for recovering carbon and nutrients, and demonstrate how a so-called “bottom-up” approach can serve as a decision-making instrument. Based on three case study catchments with a focus on domestic wastewater in Sweden and Poland, and on manure, grass and blackwater substrates in Finland, we apply a cost–benefit analysis (CBA) on system alternatives derived from a participatory process. After drawing on an initial systematic mapping of relevant ecotechnologies, the scope of the CBA is determined by stakeholder suggestions, namely in terms of the considered assessment criteria, the physical impacts and the utilised data. Thus, this CBA is rooted in a localised consideration of ecotechnologies rather than a centralised governmental approach to systems boundaries. The key advantage of applying such a bottom-up approach is that it has gone through a robust participatory selection process by local stakeholders, which provides more legitimacy to the decisions reached compared with traditional feasibility studies. Despite considering the revenues of the recovered products as well as the provision of the non-market goods CO2 mitigation and reduced eutrophication, findings from this study indicate that the benefits of the considered ecotechnologies are often outweighed by their costs. Only anaerobic digestion of agricultural wastes appears to be economically feasible under the current conditions, highlighting that further efforts and incentives may be required to mainstream ecotechnologies. © 2021, The Author(s),
|
|
| 7. |
- Guldberg Pedersen, H, et al.
(författare)
-
Forces measured between zirconia surfaces in poly(acrylic acid) solutions
- 1999
-
Ingår i: Journal of The American Ceramic Society. - 0002-7820 .- 1551-2916. ; 82, s. 1137-1145
-
Tidskriftsartikel (refereegranskat)abstract
- We have studied the forces between a sphere and a plane surface of yttria-partially-stabilized tetragonal-zirconia immersed in aqueous solutions of low-molecular-weight (Mw = 10 000) poly(acrylic acid) (PAA) using atomic force microscopy. The measurements are performed at high pH where the adsorbed, highly charged anionic polyelectrolyte extends far into the solution, resulting in a combination of polymeric (steric) and electrostatic interactions. Analysis of the experimental data using scaling theory shows that the polymeric contribution dominates and that the electrostatic contribution is small at relatively high ionic strength (0.01M NaCI). We find that the measured forces are highly dependent on time and interaction history of the absorbed PAA layer; consecutive compression-decompression cycles result in an increase of the surface coverage and the range of the repulsive polymeric interaction. This buildup of PAA at the inter-face is strongly related to attractive bridging interactions manifested as strong adhesion during decompression at less than full surface coverage. The force results are compared to rheological observations of zirconia suspensions stabilized by the same dispersant; the poor colloidal sta-bility and high viscosity at low surface coverage of PAA are related to the attractive bridging interactions.
|
|
| 8. |
|
|
| 9. |
- Skoglund, Sara, et al.
(författare)
-
A novel explanation for the enhanced colloidal stability of silver nanoparticles in the presence of an oppositely charged surfactant
- 2017
-
Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 19:41, s. 28037-28043
-
Tidskriftsartikel (refereegranskat)abstract
- The structural behavior in aqueous mixtures of negatively charged silver nanoparticles (Ag NPs) together with the cationic surfactants cetyltrimethylammonium bromide (CTAB) and dodecyltrimethylammonium chloride (DTAC), respectively, has been investigated using SANS and SAXS. From our SANS data analysis we are able to conclude that the surfactants self-assemble into micellar clusters surrounding the Ag NPs. We are able to quantify our results by means of fitting experimental SANS data with a model based on cluster formation of micelles with very good agreement. Based on our experimental results, we propose a novel mechanism for the stabilization of negatively charged Ag NPs in a solution of positively charged surfactants in which cluster formation of micelles in the vicinity of the particles prevents the particles from aggregating. Complementary SAXS and DLS measurements further support this novel way of explaining stabilization of small hydrophilic nanoparticles in surfactant-containing solutions.
|
|
| 10. |
- van Hoek, A. H. A. M., et al.
(författare)
-
A quantitative approach towards a better understanding of the dynamics of Salmonella spp. in a pork slaughter-line
- 2012
-
Ingår i: International Journal of Food Microbiology. - : Elsevier BV. - 0168-1605 .- 1879-3460. ; 153:1-2, s. 45-52
-
Tidskriftsartikel (refereegranskat)abstract
- Pork contributes significantly to the public health disease burden caused by Salmonella infections. During the slaughter process pig carcasses can become contaminated with Salmonella. Contamination at the slaughter-line is initiated by pigs carrying Salmonella on their skin or in their faeces. Another contamination route could be resident flora present on the slaughter equipment. To unravel the contribution of these two potential sources of Salmonella a quantitative study was conducted. Process equipment (belly openers and carcass splitters), faeces and carcasses (skin and cutting surfaces) along the slaughter-line were sampled at 11 sampling days spanning a period of 4. months.Most samples taken directly after killing were positive for Salmonella. On 96.6% of the skin samples Salmonella was identified, whereas a lower number of animals tested positive in their rectum (62.5%). The prevalence of Salmonella clearly declined on the carcasses at the re-work station, either on the cut section or on the skin of the carcass or both (35.9%). Throughout the sampling period of the slaughter-line the total number of Salmonella per animal was almost 2log lower at the re-work station in comparison to directly after slaughter.Seven different serovars were identified during the study with S. Derby (41%) and S. Typhimurium (29%) as the most prominent types. A recurring S. Rissen contamination of one of the carcass splitters indicated the presence of an endemic 'house flora' in the slaughterhouse studied. On many instances several serotypes per individual sample were found.The enumeration of Salmonella and the genotyping data gave unique insight in the dynamics of transmission of this pathogen in a slaughter-line. The data of the presented study support the hypothesis that resident flora on slaughter equipment was a relevant source for contamination of pork. © 2011 Elsevier B.V.
|
|
