| 1. |
- Moberg, Christina, et al.
(författare)
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De unga gör helt rätt när de stämmer staten
- 2022
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Ingår i: Aftonbladet. - 1103-9000.
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- 1 620 forskare och lärare i forskarvärlden: Vi ställer oss bakom Auroras klimatkrav
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| 2. |
- Rosén, Tomas, 1985-, et al.
(författare)
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Cross-Sections of Nanocellulose from Wood Analyzed by Quantized Polydispersity of Elementary Microfibrils
- 2020
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Ingår i: ACS Nano. - : American Chemical Society. - 1936-0851 .- 1936-086X. ; 14:12, s. 16743-16754
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Tidskriftsartikel (refereegranskat)abstract
- Bio-based nanocellulose has been shown to possess impressive mechanical properties and simplicity for chemical modifications. The chemical properties are largely influenced by the surface area and functionality of the nanoscale materials. However, finding the typical cross-sections of nanocellulose, such as cellulose nanofibers (CNFs), has been a long-standing puzzle, where subtle changes in extraction methods seem to yield different shapes and dimensions. Here, we extracted CNFs from wood with two different oxidation methods and variations in degree of oxidation and high-pressure homogenization. The cross-sections of CNFs were characterized by small-angle X-ray scattering and wide-angle X-ray diffraction in dispersed and freeze-dried states, respectively, where the results were analyzed by assuming that the cross-sectional distribution was quantized with an 18-chain elementary microfibril, the building block of the cell wall. We find that the results agree well with a pseudosquare unit having a size of about 2.4 nm regardless of sample, while the aggregate level strongly depends on the extraction conditions. Furthermore, we find that aggregates have a preferred cohesion of phase boundaries parallel to the (110)-plane of the cellulose fibril, leading to a ribbon shape on average.
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| 3. |
- Görür, Yunus Can, et al.
(författare)
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Advanced Characterization of Self-Fibrillating Cellulose Fibers and Their Use in Tunable Filters
- 2021
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society. - 1944-8244 .- 1944-8252. ; 13:27, s. 32467-32478
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Tidskriftsartikel (refereegranskat)abstract
- Thorough characterization and fundamental understanding of cellulose fibers can help us develop new, sustainable material streams and advanced functional materials. As an emerging nanomaterial, cellulose nanofibrils (CNFs) have high specific surface area and good mechanical properties; however, handling and processing challenges have limited their widespread use. This work reports an in-depth characterization of self-fibrillating cellulose fibers (SFFs) and their use in smart, responsive filters capable of regulating flow and retaining nanoscale particles. By combining direct and indirect characterization methods with polyelectrolyte swelling theories, it was shown that introduction of charges and decreased supramolecular order in the fiber wall were responsible for the exceptional swelling and nanofibrillation of SFFs. Different microscopy techniques were used to visualize the swelling of SFFs before, during, and after nanofibrillation. Through filtration and pH adjustment, smart filters prepared via in situ nanofibrillation showed an ability to regulate the flow rate through the filter and a capacity of retaining 95% of 300 nm (diameter) silica nanoparticles. This exceptionally rapid and efficient approach for making smart filters directly addresses the challenges associated with dewatering of CNFs and bridges the gap between science and technology, making the widespread use of CNFs in high-performance materials a not-so-distant reality.
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| 4. |
- Aldaeus, Fredrik, et al.
(författare)
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Characterization of pulp with high enzymatic hydrolyzability
- 2014
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Ingår i: 13th European Workshop on Lignocellulosics and Pulp (EWLP 2014) book of abstracts.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Conversion of biomass to biofuels is currently an area that attracts large interest, and lignocellulosic biomass offers the abundance and environmental attributes that can potentially support large-scale biofuel production as an alternative to petroleum-based transportation fuel.In a recent project, Innventia has developed wood based pulps optimized for conversion to biofuels. These novel pulps were produced to target a high level of enzymatic hydrolyzability. To assess the hydrolyzability of these pulps, a laboratory protocol has been established usingan enzyme mixture containing Celluclast 1.5L and Novozyme 188 with an activity of 10 FPU/g pulp (Andersen 2007). Results obtained using this protocol are assumed to be relevant for industrial conditions. In addition to assessment of the produced pulps, the results havebeen compared to commercial cellulose substrates and pulps of a variety of grades.Furthermore, supramolecular properties – specific surface area and average pore size – were determined by an in-house method utilizing solid state nuclear magnetic resonance (Larsson et al. 2013). Kappa numbers, limiting viscosities, ISO-brightness and carbohydrate compositions were determined using standard methods. Molecular mass distributions of cellulose tricarbanilates were determined by size exclusion chromatography with tetrahydrofuran mobile phase (Drechsler et al. 2000).The presentation will discuss the influence of chemical, macromolecular and supramolecular properties of commercial and novel pulp grades on the enzymatic hydrolyzability. Theprotocol used to assess of enzymatic hydrolyzability will be proposed as a benchmark test.
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| 5. |
- Aldaeus, Fredrik, et al.
(författare)
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The supramolecular structure of cellulose-rich wood and wheat straw pulps can be a determinative factor for enzymatic hydrolysability
- 2016
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Ingår i: The 7th Workshop on cellulose, regenerated cellulose and cellulose derivatives. ; , s. 39-39
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Conversion of biomass to biofuels and other products is a research area that is currently attracting a great amount of interest, particularly because such production may be envisaged as a key part of any bio-based economy. Lignocellulosic biomass is abundant and sustainable, and can therefore potentially support large-scale production of biofuel as an alternative to petroleum-based fuel.The enzymatic hydrolysability of three industrial pulps, five lab made pulps, and one microcrystalline cellulose powder was assessed using commercial cellulolytic enzymes. To gain insight into the factors that influence the hydrolysability, a thorough characterization of the samples was done, including their chemical properties (cellulose content, hemicellulose content, lignin content, and kappa number), their macromolecular properties (peak molar mass, number-average molar mass, weight-average molar mass, polydispersity, and limiting viscosity) and their supramolecular properties (fibre saturation point, specific surface area, average pore size, and crystallinity). The hydrolysability was assessed by determination of initial conversion rate and final conversion yield, with conversion yield defined as the amount of glucose in solution per unit of glucose in the substrate. Multivariate data analysis revealed that for the investigated samples the conversion of cellulose to glucose was mainly dependent on the supramolecular properties, such as specific surface area and average pore size. The molar mass distribution, the crystallinity, and the lignin content of the pulps had no significant effect on the hydrolysability of the investigated samples.In addition, experiments were carried out aiming at identifying suitable conditions for pre-treatment of wheat straw, for the purpose of making cellulose rich pulps with improved enzymatic reactivity. Two sets of conditions for pre-treatment of wheat straw were identified; a combination of low temperature alkaline washing and acid pre-hydrolysis, or high temperature acid pre-hydrolysis. Both bleached wheat straw pulps showed similar enzymatic reactivity. However, the enzymatic reactivity of both bleached wheat straw pulps was found to be significantly less than what has been achieved for wood pulps. A probable explanation for the low enzymatic reactivity of the bleached wheat straw pulp can be the small pore size, limiting the access for enzymes to the cellulose surfaces in the fibre wall interior.Text, figures and tables in an extended abstract (< 4 pages with title and references).
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| 6. |
- Beecham, Ashley H, et al.
(författare)
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Analysis of immune-related loci identifies 48 new susceptibility variants for multiple sclerosis.
- 2013
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Ingår i: Nature genetics. - : Springer Science and Business Media LLC. - 1546-1718 .- 1061-4036. ; 45:11, s. 1353-60
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Tidskriftsartikel (refereegranskat)abstract
- Using the ImmunoChip custom genotyping array, we analyzed 14,498 subjects with multiple sclerosis and 24,091 healthy controls for 161,311 autosomal variants and identified 135 potentially associated regions (P < 1.0 × 10(-4)). In a replication phase, we combined these data with previous genome-wide association study (GWAS) data from an independent 14,802 subjects with multiple sclerosis and 26,703 healthy controls. In these 80,094 individuals of European ancestry, we identified 48 new susceptibility variants (P < 5.0 × 10(-8)), 3 of which we found after conditioning on previously identified variants. Thus, there are now 110 established multiple sclerosis risk variants at 103 discrete loci outside of the major histocompatibility complex. With high-resolution Bayesian fine mapping, we identified five regions where one variant accounted for more than 50% of the posterior probability of association. This study enhances the catalog of multiple sclerosis risk variants and illustrates the value of fine mapping in the resolution of GWAS signals.
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| 7. |
- Bergenstråhle-Wohlert, Malin, et al.
(författare)
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Concentration enrichment of urea at cellulose surfaces : results from molecular dynamics simulations and NMR spectroscopy
- 2012
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Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 19:1, s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- A combined solid-state NMR and Molecular Dynamics simulation study of cellulose in urea aqueous solution and in pure water was conducted. It was found that the local concentration of urea is significantly enhanced at the cellulose/solution interface. There, urea molecules interact directly with the cellulose through both hydrogen bonds and favorable dispersion interactions, which seem to be the driving force behind the aggregation. The CP/MAS (13)C spectra was affected by the presence of urea at high concentrations, most notably the signal at 83.4 ppm, which has previously been assigned to C4 atoms in cellulose chains located at surfaces parallel to the (110) crystallographic plane of the cellulose I beta crystal. Also dynamic properties of the cellulose surfaces, probed by spin-lattice relaxation time (13)CT (1) measurements of C4 atoms, are affected by the addition of urea. Molecular Dynamics simulations reproduce the trends of the T (1) measurements and lends new support to the assignment of signals from individual surfaces. That urea in solution is interacting directly with cellulose may have implications on our understanding of the mechanisms behind cellulose dissolution in alkali/urea aqueous solutions.
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| 8. |
- Caraballo, Remi, et al.
(författare)
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Structure-activity relationships for lipoprotein lipase agonists that lower plasma triglycerides in vivo
- 2015
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Ingår i: European Journal of Medicinal Chemistry. - : Elsevier. - 0223-5234 .- 1768-3254. ; 103, s. 191-209
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Tidskriftsartikel (refereegranskat)abstract
- The risk of cardiovascular events increases in individuals with elevated plasma triglyceride (TG) levels, therefore advocating the need for efficient TG-lowering drugs. In the blood circulation, TG levels are regulated by lipoprotein lipase (LPL), an unstable enzyme that is only active as a non-covalently associated homodimer. We recently reported on a N-phenylphthalimide derivative (1) that stabilizes LPL in vitro, and moderately lowers triglycerides in vivo (Biochem. Biophys. Res. Common. 2014, 450, 1063). Herein, we establish structure activity relationships of 51 N-phenylphthalimide analogs of the screening hit 1. In vitro evaluation highlighted that modifications on the phthalimide moiety were not tolerated and that lipophilic substituents on the central phenyl ring were functionally essential. The substitution pattern on the central phenyl ring also proved important to stabilize LPL However, in vitro testing demonstrated rapid degradation of the phthalimide fragment in plasma which was addressed by replacing the phthalimide scaffold with other heterocyclic fragments. The in vitro potency was retained or improved and substance 80 proved stable in plasma and efficiently lowered plasma TGs in vivo. 2015 The Authors. Published by Elsevier Masson SAS.
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| 9. |
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| 10. |
- Karlsson, Rose-Marie Pernilla, et al.
(författare)
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Thermodynamics of the Water-Retaining Properties of Cellulose-Based Networks
- 2019
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Ingår i: Biomacromolecules. - : American Chemical Society. - 1525-7797 .- 1526-4602. ; 20:4, s. 1603-1612
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Tidskriftsartikel (refereegranskat)abstract
- Noncrystalline cellulose-based gel beads were used as a model material to investigate the effect of osmotic stress on a cellulosic network. The gel beads were exposed to osmotic stress by immersion in solutions with different concentrations of high molecular mass dextran and the equilibrium dimensional change of the gel beads was studied using optical microscopy. The volume fraction of cellulose was calculated from the volume of the gel beads in dextran solutions and their dry content and the relation between the cellulose volume fraction and the total osmotic pressure was thus obtained. The results show that the contribution to the osmotic pressure from counterions increases the water-retaining capacity of the beads at high osmotic pressures but also that the main factor controlling the gel bead collapse at high osmotic strains is the resistance to the deformation of the polymer chain network within the beads. Furthermore, the osmotic pressure associated with the deformation of the polymer network, which counteracts the deswelling of the beads, could be fitted to the Wall model indicating that the response of the cellulose polymer networks was independent of the charge of the cellulose. The best fit to the Wall model was obtained when the Flory-Huggins interaction parameter (Ç) of the cellulose-water system was set to 0.55-0.60, in agreement with the well-established insolubility of high molecular mass β-(1,4)-d-glucan polymers in water.
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| 11. |
- Larsson, Per Tomas, et al.
(författare)
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Characterization of cellulose supramolecular structure using solid-state NMR
- 2014
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Ingår i: Analysdagarna book of abstracts.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Cellulose I isolated from wood in the form of cellulose-rich fibres, i.e. as a pulp, is a widely used raw material that holds a potential for further and more versatile use. Due to its abundance cellulose can be a benign replacement for many materials used in everydaycommodities.Isolated cellulose I is associated with a complex supramolecular structure (in the nanometresdimensional range), and in the case of cellulose-richfibres it is also associated with a complex fibre wall morphology (typical wood fibres are millimetres long and tenths of micrometres wide).The main advantage of using cellulose-rich fibres is an existence of a worldwide industry which has the processing equipment and the know-how necessary for efficient handling and processing of wood-based pulps.Utilization of cellulose I is dependent on the reactivity of the cellulose substrate, here the term reactivity is used in a broad sense. Enzymatic conversion of cellulose-rich fibres to sugars or the dissolution of cellulose for textile fibre manufacture is two examples where different aspects of the cellulosereactivity are important for efficient processing.Several methods for characterizing various aspects of cellulose are available. The degree of polymerization and the degree of cellulose crystallinity are two examples. In the case of cellulose-rich fibres its carbohydrate composition can be of importance. Traditionally lessattention has been paid to the supramolecular characteristics of cellulose although they are in a dimensional range that could exert an influence on the chemistry used.The present work deals with the characterization of the supramolecular properties of cellulose and cellulose-rich fibres and illustrates some examples where the supramolecular structure of the cellulose is a controlling factor for its reactivity. Most of the presented work is based on CP/MAS 13 C-NMR measurements. Using this technique it has been shown that robust measurements of cellulose nanostructures such aslateral fibril dimensions and lateral fibril aggregate dimensions can be obtained and how subsequently the specific surface area of the cellulose in a water-swollen state can be estimated. Moreover, by combining NMR resultswith measurements of the amount of water located inside a water-swollen fibre wall, estimates of the average fibre wall pore size can be obtained. Such results have beenrelated to data from enzymatic hydrolysis of cellulose-richfibres to illustrate the influence of supramolecular structure on enzymatic reactivity.
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| 12. |
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| 13. |
- Larsson, Per Tomas, et al.
(författare)
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Internal Structure of Isolated Cellulose I Fibril Aggregates in the Water Swollen State
- 2017
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Ingår i: Nanocelluloses: Their Preparation, Properties and Applications. - Washington, DC : American Chemical Society (ACS). ; , s. 91-112, s. 91-112
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Bokkapitel (refereegranskat)abstract
- By combining H-2-NMRD and CP/MAS C-13-NMR measurements of water-based cellulose gels and of water swollen pulps it was possible to estimate the nature of the interior structure of cellulose fibril aggregates. A set of samples with high cellulose purity and low charge was used. The interpretation of data was based on a relaxation model describing the exchange dynamics for deuterium exchange between water molecules and cellulose hydroxyl groups. The theoretical model used made it possible to calculate cellulose surface-to-volume ratios (q-values) from both H-2-NMRD and CP/MAS C-13-NMR data. Good consistency between H-2-NMRD and CP/MAS C-13-NMR data was found. In all investigated samples the cellulose fibril aggregates showed a different degree of "openness" interpreted as the presence of interstitial water inside fibril aggregates. One result also showed that an increased degree of fibril aggregate openness results from the TEMPO-oxidation. Common to all samples was that in the water swollen state water molecules could access part of the fibril aggregate interior.
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| 14. |
- Larsson, Per Tomas, et al.
(författare)
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Line shapes in CP/MAS 13C NMR spectra of cellulose I
- 2005
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Ingår i: Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. - : Elsevier BV. - 1386-1425. ; 62:1-3, s. 539-46
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Tidskriftsartikel (refereegranskat)abstract
- The CP/MAS 13C NMR line shape of cellulose I has been qualitatively analyzed by direct simulations using the Ornstein–Uhlenbeck stochastic process and the Kubo model. Both approaches describe a anhydroglucose C4 carbon as a oscillator with fluctuating Larmor frequency. The NMR resonance frequency is written , where the fluctuating part with zero mean was modelled as a stationary Markov diffusion process.The simulation results both motivates the use of multiple line shapes when fitting CP/MAS 13C NMR spectra recorded on cellulose I and gives some insights into why signals from crystalline cellulose I give rise to Lorentzian line shapes.
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| 15. |
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| 16. |
- Sawcer, Stephen, et al.
(författare)
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Genetic risk and a primary role for cell-mediated immune mechanisms in multiple sclerosis
- 2011
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 476:7359, s. 214-219
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Tidskriftsartikel (refereegranskat)abstract
- Multiple sclerosis is a common disease of the central nervous system in which the interplay between inflammatory and neurodegenerative processes typically results in intermittent neurological disturbance followed by progressive accumulation of disability. Epidemiological studies have shown that genetic factors are primarily responsible for the substantially increased frequency of the disease seen in the relatives of affected individuals, and systematic attempts to identify linkage in multiplex families have confirmed that variation within the major histocompatibility complex (MHC) exerts the greatest individual effect on risk. Modestly powered genome-wide association studies (GWAS) have enabled more than 20 additional risk loci to be identified and have shown that multiple variants exerting modest individual effects have a key role in disease susceptibility. Most of the genetic architecture underlying susceptibility to the disease remains to be defined and is anticipated to require the analysis of sample sizes that are beyond the numbers currently available to individual research groups. In a collaborative GWAS involving 9,772 cases of European descent collected by 23 research groups working in 15 different countries, we have replicated almost all of the previously suggested associations and identified at least a further 29 novel susceptibility loci. Within the MHC we have refined the identity of the HLA-DRB1 risk alleles and confirmed that variation in the HLA-A gene underlies the independent protective effect attributable to the class I region. Immunologically relevant genes are significantly overrepresented among those mapping close to the identified loci and particularly implicate T-helper-cell differentiation in the pathogenesis of multiple sclerosis.
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| 17. |
- Abitbol, Tiffany, et al.
(författare)
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Cellulose nanocrystal/low methoxyl pectin gels produced by internal ionotropic gelation.
- 2021
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 260
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Tidskriftsartikel (refereegranskat)abstract
- The biotechnological applications of cellulose nanocrystals (CNCs) continue to grow due to their sustainable nature, impressive mechanical, rheological, and emulsifying properties, upscaled production capacity, and compatibility with other materials, such as protein and polysaccharides. In this study, hydrogels from CNCs and pectin, a plant cell wall polysaccharide broadly used in food and pharma, were produced by calcium ion-mediated internal ionotropic gelation (IG). In the absence of pectin, a minimum of 4 wt% CNC was needed to produce self-supporting gels by internal IG, whereas the addition of pectin at 0.5 wt% enabled hydrogel formation at CNC contents as low as 0.5 wt%. Experimental data indicate that CNCs and pectin interact to give robust and self-supporting hydrogels at solid contents below 2.5 %. Potential applications of these gels could be as carriers for controlled release, scaffolds for cell growth, or wherever else distinct and porous network morphologies are required.
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| 18. |
- Adeboye, Peter, 1982, et al.
(författare)
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In situ conversion of phenolic compounds as a tool to phenolic tolerance development by S. cerevisiae
- 2015
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Phenolic compounds in hydrolysates are degradation products from the lignin component of wood. They are diverse in nature and they account for some of the inhibitory activities observed during lignocellulosic fermentation. S. cerevisiae possesses the ability to convert some phenolic compounds. We are currently studying the interaction between S. cerevisiae and selected phenolic compounds namely; coniferyl aldehyde, ferulic acid and p-coumaric acid to understand the ability of S. cerevisiae to convert the selected compounds. Preliminary results show that the three phenolic compounds are being converted into several other less inhibitory phenolic compounds common to the three compounds. We hypothesised a conversion route and engineered S. cerevisiae strains to test the hypothesis, the preliminary result shows faster conversion in an engineered strain.
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| 19. |
- Al Mukhtar, Ali, et al.
(författare)
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The epidemiology of and management of pediatric patients with head trauma : a hospital-based study from Southern Sweden
- 2022
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Ingår i: Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine. - : Springer Science and Business Media LLC. - 1757-7241. ; 30:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: Traumatic brain injury (TBI) is a common cause of morbidity and mortality in children worldwide. In Scandinavia, the epidemiology of pediatric head trauma is poorly documented. This study aimed to investigate and compare the epidemiology and management of pediatric patients with isolated head trauma (IHT) and head trauma in connection with multitrauma (MHT). Methods: We conducted a retrospective review of medical records of patients < 18 years of age who attended any of the five emergency departments (ED) in Scania County in Sweden in 2016 due to head trauma. Clinical data of patients with IHT were analyzed and compared with those of patients with MHT. Results: We identified 5046 pediatric patients with head trauma, 4874 with IHT and 186 with MHT, yielding an incidence of ED visits due to head trauma of 1815/100,000 children/year. There was male predominance, and the median age was four years. Falls were the dominating trauma mechanism in IHT patients, while motor vehicle accidents dominated in MHT patients. The frequencies of CT head-scans, ward admissions and intracranial injuries (ICI) were 5.4%, 11.1% and 0.7%, respectively. Four patients (0.08%) required neurosurgical intervention. The relative risks for CT-scans and admissions to a hospital ward and ICI were 10, 4.5 and 19 times higher for MHT compared with IHT patients. Conclusion: Head trauma is a common cause of ED visits in our study. Head-CTs and ICIs were less frequent than in previous studies. MHT patients had higher rates of CT-scans, admissions, and ICIs than IHT patients, suggesting that they are separate entities that should ideally be managed using different guidelines to optimize the use of CT-scans of the head.
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| 20. |
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| 21. |
- Andersson, Linnéa, et al.
(författare)
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Evaluating pore space in macroporous ceramics with water-based porosimetry
- 2013
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Ingår i: Journal of The American Ceramic Society. - : Wiley. - 0002-7820 .- 1551-2916. ; 96:6, s. 1916-1922
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Tidskriftsartikel (refereegranskat)abstract
- We show that water-based porosimetry (WBP), a facile, simple, and nondestructive porosimetry technique, accurately evaluates both the pore size distribution and throat size distribution of sacrificially templated macroporous alumina. The pore size distribution and throat size distribution derived from the WBP evaluation in uptake (imbibition) and release (drainage) mode, respectively, were corroborated by mercury porosimetry and X-ray micro-computed tomography (μ-CT). In contrast with mercury porosimetry, the WBP also provided information on the presence of “dead-end pores” in the macroporous alumina.
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| 22. |
- Ansari, Farhan, et al.
(författare)
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Hierarchical wood cellulose fiber/epoxy biocomposites : Materials design of fiber porosity and nanostructure
- 2015
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Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 74, s. 60-68
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Tidskriftsartikel (refereegranskat)abstract
- Delignified chemical wood pulp fibers can be designed to have a controlled structure of cellulose fibril aggregates to serve as porous templates in biocomposites with unique properties. The potential of these fibers as reinforcement for an epoxy matrix (EP) was investigated in this work. Networks of porous wood fibers were impregnated with monomeric epoxy and cured. Microscopy images from ultramicrotomed cross sections and tensile fractured surfaces were used to study the distribution of matrix inside and around the fibers - at two different length scales. Mechanical characterization at different relative humidity showed much improved mechanical properties of biocomposites based on epoxy-impregnated fibers and they were rather insensitive to surrounding humidity. Furthermore, the mechanical properties of cellulose-fiber biocomposites were compared with those of cellulose-nanofibril (CNF) composites; strong similarities were found between the two materials. The reasons for this, some limitations and the role of specific surface area of the fiber are discussed.
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| 23. |
- Bergenstråhle, Malin, 1977-, et al.
(författare)
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Dynamics of Cellulose-Water Interfaces : NMR Spin-Lattice Relaxation Times Calculated from Atomistic Computer Simulations
- 2008
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Ingår i: Journal of Physical Chemistry B. - Washington : ACS Publications. - 1520-6106 .- 1520-5207. ; 112:9, s. 2590-2595
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Tidskriftsartikel (refereegranskat)abstract
- Solid-state nuclear magnetic resonance (CP/MAS 13C NMR) spectroscopy has often been used to study cellulose structure, but some features of the cellulose NMR spectrum are not yet fully understood. One such feature is a doublet around 84 ppm, a signal that has been proposed to originate from C4 atoms at cellulose fibril surfaces. The two peaks yield different T1, differing by approximately a factor of 2 at 75 MHz. In this study, we calculate T1 from C4-H4 vector dynamics obtained from molecular dynamics computer simulations of cellulose Iβ-water interfacial systems. Calculated and experimentally obtained T1 values for C4 atoms in surface chains fell within the same order of magnitude, 3-20 s. This means that the applied force field reproduces relevant surface dynamics for the cellulose-water interface sufficiently well. Furthermore, a difference in T1 of about a factor of 2 in the range of Larmor frequencies 25-150 MHz was found for C4 atoms in chains located on top of two different crystallographic planes, namely, (110) and (10). A previously proposed explanation that the C4 peak doublet could derive from surfaces parallel to different crystallographic planes is herewith strengthened by computationally obtained evidence. Another suggested basis for this difference is that the doublet originates from C4 atoms located in surface anhydro-glucose units with hydroxymethyl groups pointing either inward or outward. This was also tested within this study but was found to yield no difference in calculated T1.
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| 24. |
- Boge, Lukas, 1987, et al.
(författare)
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Cubosomes for topical delivery of the antimicrobial peptide LL-37
- 2019
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Ingår i: European Journal of Pharmaceutics and Biopharmaceutics. - : Elsevier BV. - 1873-3441 .- 0939-6411. ; 134, s. 60-67
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the use of cubosomes for topical delivery of the antimicrobial peptide (AMP) LL-37 was investigated. Topical delivery of AMPs is of great interest for treatment of skin infections caused by bacteria, such as Staphylococcus aureus. AMP containing cubosomes were produced by three different preparation protocols and compared: (i) pre-loading, where LL-37 was incorporated into a liquid crystalline gel, which thereafter was dispersed into nanoparticles, (ii) post-loading, where LL-37 was let to adsorb onto pre-formed cubosomes, and (iii) hydrotrope-loading, where LL-37 was incorporated during the spontaneously formed cubosomes in an ethanol/glycerol monooleate mixture. Particle size and size distribution were analyzed using dynamic light scattering (DLS), liquid crystalline structure by small angle x-ray scattering (SAXS) and release of LL-37 by a fluorescamine assay. Proteolytic protection of LL-37 as well as bactericidal effect after enzyme exposure was investigated. The skin irritation potential of cubosomes was examined by an in vitro epidermis model. Finally, the bacterial killing property of the cubosomes was examined by an ex vivo pig skin wound infection model with Staphylococcus aureus. Data showed that a high loading of LL-37 induced formation of vesicles in case of cubosomes prepared by sonication (pre-loading). No release of LL-37 was observed from the cubosomes, indicating strong association of the peptide to the particles. Proteolysis studies showed that LL-37 was fully protected against enzymatic attacks while associated with the cubosomes, also denoting strong association of the peptide to the particles. As a consequence, bactericidal effect after enzyme exposure remained, compared to pure LL-37 which was subjected to proteolysis. No skin irritation potential of the cubosomes was found, thus enabling for topical administration. The ex vivo wound infection model showed that LL-37 in pre-loaded cubosomes killed bacteria most efficient.
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| 25. |
- Boge, Lukas, et al.
(författare)
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Cubosomes for topical delivery of the antimicrobial peptide LL-37
- 2019
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Ingår i: European journal of pharmaceutics and biopharmaceutics. - : Elsevier BV. - 0939-6411 .- 1873-3441. ; 134, s. 60-67
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the use of cubosomes for topical delivery of the antimicrobial peptide (AMP) LL-37 was investigated. Topical delivery of AMPs is of great interest for treatment of skin infections caused by bacteria, such as Staphylococcus aureus. AMP containing cubosomes were produced by three different preparation protocols and compared: (i) pre-loading, where LL-37 was incorporated into a liquid crystalline gel, which thereafter was dispersed into nanoparticles, (ii) post-loading, where LL-37 was let to adsorb onto pre-formed cubosomes, and (iii) hydrotrope-loading, where LL-37 was incorporated during the spontaneously formed cubosomes in an ethanol/glycerol monooleate mixture. Particle size and size distribution were analyzed using dynamic light scattering (DLS), liquid crystalline structure by small angle x-ray scattering (SAXS) and release of LL-37 by a fluorescamine assay. Proteolytic protection of LL-37 as well as bactericidal effect after enzyme exposure was investigated. The skin irritation potential of cubosomes was examined by an in vitro epidermis model. Finally, the bacterial killing property of the cubosomes was examined by an ex vivo pig skin wound infection model with Staphylococcus aureus. Data showed that a high loading of LL-37 induced formation of vesicles in case of cubosomes prepared by sonication (pre-loading). No release of LL-37 was observed from the cubosomes, indicating strong association of the peptide to the particles. Proteolysis studies showed that LL-37 was fully protected against enzymatic attacks while associated with the cubosomes, also denoting strong association of the peptide to the particles. As a consequence, bactericidal effect after enzyme exposure remained, compared to pure LL-37 which was subjected to proteolysis. No skin irritation potential of the cubosomes was found, thus enabling for topical administration. The ex vivo wound infection model showed that LL-37 in pre-loaded cubosomes killed bacteria most efficient.
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| 26. |
- Borg, Tomas, 1963-, et al.
(författare)
-
Health-related quality of life and life satisfaction in patients following surgically treated pelvic ring fractures. A prospective observational study with two years follow-up
- 2010
-
Ingår i: Injury. - : Elsevier. - 0020-1383 .- 1879-0267. ; 41:4, s. 400-404
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Pelvic ring fractures caused by high-energy trauma are severe injuries with well described radiological and clinical outcomes, whereas description from the patient's perspective is less well documented. The purpose of this study was to investigate patient-reported outcome following surgical treatment of pelvic fractures using quality of life instruments.METHODS: All 54 patients (28 male/26 female, ages 16-68) with pelvic fractures referred to our institution for surgical treatment 2003-2005 were prospectively included. The most common trauma was motor vehicle accident (44%). Additional injuries were seen in 74% and in 31% the ISS was >or=16. There were 31 B and 23 C type fractures. Patients were followed for two years using two validated questionnaires, SF-36 and LiSat-11, the latter an instrument consisting of 11 questions for evaluation of satisfaction with different aspects of life.RESULTS: 45 patients could be followed according to the study protocol for two years while 2 were untraceable and 1 died from unrelated causes. Of 6 nonresponders, 5 were unable due to psychiatric disorder. At two years pelvic fracture patients scored lower than the reference population in both physical and mental domains (SF-36). Highest mean score, 68, was in the domain Social Function (norm 89) while lowest mean score, 38, was in the domain Role Physical (norm 86). The mean score closest to the normative was for general health with 61 for patients and 78 for the normative group. In LiSat-11 pelvic fracture patients scored lower than the reference population in all areas. Satisfaction with life as a whole was 31% compared with 60% in the normative group.CONCLUSIONS: Two years after surgical treatment of pelvic ring fractures, patients reported substantially lower quality of life for both physical and mental domains, when compared with a reference population, even when radiological and clinical outcomes were considered favourable.
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| 27. |
- Borg, Tomas, et al.
(författare)
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Quality of Life After Operative Fixation of Displaced Acetabular Fractures
- 2012
-
Ingår i: Journal of Orthopaedic Trauma. - : Lippincott Williams & Wilkins. - 0890-5339 .- 1531-2291. ; 26:8, s. 445-450
-
Tidskriftsartikel (refereegranskat)abstract
- Objective: The aim of this study was to determine quality of life (QoL) changes over time after internal fixation of acetabular fractures.Design: This pertains to a prospective cohort study, which was single centered.Setting: The study was conducted at the University Hospital.Patients: One hundred thirty-six patients (108 men, 28 women), age 17-83 years operated for an acetabular fracture during 2004-2008 were prospectively included and followed up for 2 years.Main Outcome Measures: QoL was evaluated via Short Form-36 (SF-36) and Life Satisfaction-11 at 6, 12, and 24 months. Radiographs were evaluated according to Matta at 2 years.Results: The most frequent fracture types were posterior wall (n31), associated anterior-posterior hemitransverse (n34), and associated both column (n29). One hundred twenty-nine patients could be assessed at 2 years, 4 did not respond, and 3 had died. The patients scored lower than norms in all 8 SF-36 domains with improvement over time for Physical Function (P < 0.0001) and Role Physical (P < 0.0001). The patients with postop reduction 0-1 mm scored better (P < 0.001-0.039) in 7 domains, all except vitality (P = 0.07), when compared with patients with residual displacement of >= 2 mm. Life satisfaction did not change with time and showed lower scores than normative in 9 of 11 items. Nineteen patients had undergone total hip replacement, and the strongest predictor was acetabular or femoral head impaction.Conclusions: QoL in surgically treated patients with displaced acetabular fracture keeps improving in physical SF-36 domains over a 2-year period although still lower than norms, and anatomical reduction results in better QoL outcome in most dimensions.
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| 28. |
- Borrega, Marc, et al.
(författare)
-
Birch wood pre-hydrolysis vs pulp post-hydrolysis for the production of xylan-based compounds and cellulose for viscose application
- 2018
-
Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 190, s. 212-221
-
Tidskriftsartikel (refereegranskat)abstract
- Hydrothermal treatments of birch wood and kraft pulp were compared for their ability to extract the xylan and produce viscose-grade pulp. Water post-hydrolysis of kraft pulp produced a high-purity cellulosic pulp with lower viscosity but higher cellulose yield than traditional pre-hydrolysis kraft pulping of wood. Post-hydrolysis of pulp also increased the crystallite dimensions and degree of crystallinity in cellulose, and promoted a higher extent of fibril aggregation. The lower specific surface area in post-hydrolyzed pulps, derived from their larger fibril aggregates, decreased the accessibility of –OH groups. However, this lower accessibility did not seem to decrease the pulp reactivity to derivatizing chemicals. In the aqueous side-stream, the xylose yield was similar in both pre- and post-hydrolysates, although conducting post-hydrolysis of pulp in a flow-through system enabled the recovery of high purity and molar mass (∌10 kDa) xylan for high-value applications.
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| 29. |
- Butchosa, Nuria, et al.
(författare)
-
Nanocomposites of bacterial cellulose nanofibers and chitin nanocrystals : fabrication, characterization and bactericidal activity
- 2013
-
Ingår i: Green Chemistry. - : Royal Society of Chemistry (RSC). - 1463-9262 .- 1463-9270. ; 15:12, s. 3404-3413
-
Tidskriftsartikel (refereegranskat)abstract
- An environmentally friendly approach was implemented for the production of nanocomposites with bactericidal activity, using bacterial cellulose (BC) nanofibers and chitin nanocrystals (ChNCs). The antibacterial activity of ChNCs prepared by acid hydrolysis, TEMPO-mediated oxidation or partial deacetylation of a-chitin powder was assessed and the structure of the ChNC nanoparticles was characterized by X-ray diffraction, atomic force microscopy, and solid-state C-13-NMR. The partially deacetylated ChNCs (D-ChNC) showed the strongest antibacterial activity, with 99 +/- 1% inhibition of bacterial growth compared to control samples. Nanocomposites were prepared from BC nanofibers and D-ChNC by (i) in situ biosynthesis with the addition of D-ChNC nanoparticles in the culture medium of Acetobacter aceti, and (ii) post-modification by mixing D-ChNC with disintegrated BC in an aqueous suspension. The structure and mechanical properties of the BC/D-ChNC nanocomposites were characterized by Fourier transform infrared spectroscopy, elemental analysis, field-emission scanning electron microscopy, and an Instron universal testing machine. The bactericidal activity of the nanocomposites increased with the D-ChNC content, with a reduction in bacterial growth by 3.0 log units when the D-ChNC content was 50%. D-ChNC nanoparticles have great potential as substitutes for unfriendly antimicrobial compounds such as heavy metal nanoparticles and synthetic polymers to introduce antibacterial properties to cellulosic materials.
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| 30. |
- Bågenholm-Ruuth, Edvin, et al.
(författare)
-
Transforming post-consumer cotton waste textiles into viscose staple fiber using hydrated zinc chloride
- 2024
-
Ingår i: Cellulose. - : Springer Science and Business Media B.V.. - 0969-0239 .- 1572-882X. ; 31:2, s. 737-748
-
Tidskriftsartikel (refereegranskat)abstract
- Large amounts of cellulose-based waste textiles are generated every year, yet little is done to recycle this waste. Alternatives such as fiber-to-fiber recycling, where a significant part of the value of the waste textiles is recovered, are attractive possibilities. In this study, we have investigated the viability of using hydrated zinc chloride (ZnCl2·4H2O) as a solvent and swelling agent to convert cotton waste textiles (the most abundant cellulose-based waste textile) into a dissolving pulp that can be used as raw material for the production and spinning of viscose fibers. The solvent produced an accessible dissolving pulp and exhibited excellent recyclability, maintaining good dissolving power even after repeated recycling. The dissolving pulp was subsequently used to produce viscose dope, a spinning solution which was spun and cut into viscose staple fibers. The viscose dope exhibited good properties (moderate filter clogging value and gamma number), and the resulting staple fibers were strong and of good quality (high linear density, elongation, and tenacity). These results illustrate the potential of using hydrated zinc chloride for the production of viscose grade dissolving pulp from cotton waste textiles.
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| 31. |
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| 32. |
- Carlsson, Linn, et al.
(författare)
-
Surface characteristics of cellulose nanoparticles grafted by surface-initiated ring-opening polymerization of epsilon-caprolactone
- 2015
-
Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 22:2, s. 1063-1074
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, surface-initiated ring-opening polymerization has been employed for the grafting of epsilon-caprolactone from cellulose nanoparticles, made by partial hydrolysis of cellulose cotton linters. A sacrificial initiator was employed during the grafting reactions, to form free polymer in parallel to the grafting reaction. The degree of polymerization of the polymer grafts, and of the free polymer, was varied by varying the reaction time. The aim of this study was to estimate the cellulose nanoparticle degree of surface substitution at different reaction times. This was accomplished by combining measurement results from spectroscopy and chromatography. The prepared cellulose nanoparticles were shown to have 3.1 (+/- 0.3) % of the total anhydroglucose unit content present at the cellulose nanoparticle surfaces. This effectively limits the amount of cellulose that can be targeted by the SI-ROP reactions. For a certain SI-ROP reaction time, it was assumed that the resulting degree of polymerization (DP) of the grafts and the DP of the free polymer were equal. Based on this assumption it was shown that the cellulose nanoparticle surface degree of substitution remained approximately constant (3-7 %) and seemingly independent of SI-ROP reaction time. We believe this work to be an important step towards a deeper understanding of the processes and properties controlling SI-ROP reactions occurring at cellulose surfaces.
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| 33. |
- Carrick, Christopher, et al.
(författare)
-
Hollow cellulose capsules from CO2 saturated cellulose solutions - Their preparation and characterization
- 2013
-
Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 3:7, s. 2462-2469
-
Tidskriftsartikel (refereegranskat)abstract
- A new material consisting of mm-sized hollow cellulose spheres, for biomedical applications or for the preparation of low weight porous materials has been prepared by a unique solution precipitation (SP) method. The technique is based on three separate steps. In the first step, high molecular mass, non-modified cellulose is dissolved in a suitable solvent. This cellulose solution is then saturated with a suitable gas (CO2 or N2 in the present work) and finally this gas-saturated solution is drop-wise added to a water reservoir. In this step, the cellulose is precipitated and a gas bubble is nucleated in the center of the cellulose sphere. When stored in water, the hollow center is filled with water, indicating that the capsule wall is porous in nature. This was also supported by BET-area measurements as well as by high resolution SEM-images of broken capsule walls. The internal void volume of a capsule was about 5 μl and the wall volume was about 8 μl. It was also established that the properties of the cellulose capsules, i.e. wall and void volume, the specific surface area, the average pore size of the capsule wall, the wall density, and the compressive load capacity could be tuned by the choice of cellulose concentration in the solution before precipitation. The capsule wall volume and void volume were also affected by the choice of gas, the gas pressure and the gas dissolution time during the gas saturation step. The response of the cellulose wall of the prepared capsules to changes in pH and ion concentration in the surrounding solution was also investigated. The swelling-shrinking behavior was further investigated by introducing more charges to the capsule wall, via carboxymethylation of the cellulose. This was achieved by using carboxymethylated cellulose which increased the swelling-shrinking effect. The results show a typical polyelectrolyte gel behavior of the capsule wall and the wet modulus of the cellulose wall was determined to be between 0.09-0.2 MPa depending on the charge of the cellulose in the capsule wall. Furthermore, the freeze dried cellulose spheres had a modulus of 1.9-7.4 MPa, depending on the cellulose concentration during the preparation of the spheres. These cellulose capsules are suitable both for the preparation of porous materials, where these larger spheres are joined together in 3D-shaped materials, and for controlled release where the interior of the capsules is filled with active substances and these substances are released by controlling the pores in the capsule walls.
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| 34. |
- Carrick, Christopher, et al.
(författare)
-
Lightweight, Highly Compressible, Noncrystalline Cellulose Capsules
- 2014
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 30:26, s. 7635-7644
-
Tidskriftsartikel (refereegranskat)abstract
- We demonstrate how to prepare extraordinarily deformable, gas-filled, spherical capsules from nonmodified cellulose. These capsules have a low nominal density, ranging from 7.6 to 14.2 kg/m(3), and can be deformed elastically to 70% deformation at 50% relative humidity. No compressive strain-at-break could be detected for these dry cellulose capsules, since they did not rupture even when compressed into a disk with pockets of highly compressed air. A quantitative constitutive model for the large deformation compression of these capsules is derived, including their high-frequency mechanical response and their low-frequency force relaxation, where the latter is governed by the gas barrier properties of the dry capsule. Mechanical testing corroborated these models with good accuracy. Force relaxation measurements at a constant compression rendered an estimate for the gas permeability of air through the capsule wall, calculated to 0.4 mL mu m/m(2) days kPa at 50% relative humidity. These properties taken together open up a large application area for the capsules, and they could most likely be used for applications in compressible, lightweight materials and also constitute excellent model materials for adsorption and adhesion studies.
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| 35. |
- Cervin, Nicholas Tchang, et al.
(författare)
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Ultra porous nanocellulose aerogels as separation medium for mixtures of oil/water liquids
- 2012
-
Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 19:2, s. 401-410
-
Tidskriftsartikel (refereegranskat)abstract
- A novel type of sponge-like material for the separation of mixed oil and water liquids has been prepared by the vapour deposition of hydrophobic silanes on ultra-porous nanocellulose aerogels. To achieve this, a highly porous (> 99%) nanocellulose aerogel with high structural flexibility and robustness is first formed by freeze-drying an aqueous dispersion of the nanocellulose. The density, pore size distribution and wetting properties of the aerogel can be tuned by selecting the concentration of the nanocellulose dispersion before freeze-drying. The hydrophobic light- weight aerogels are almost instantly filled with the oil phase when selectively absorbing oil from water, with a capacity to absorb up to 45 times their own weight in oil. The oil can also be drained from the aerogel and the aerogel can then be reused for a second absorption cycle.
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| 36. |
- Chunilall, V., et al.
(författare)
-
A CP/MAS 13C-NMR study of cellulose fibril aggregation in eucalyptus dissolving pulps during drying and the correlation between aggregate dimensions and chemical reactivity
- 2010
-
Ingår i: Holzforschung. - 0018-3830 .- 1437-434X. ; 64:6, s. 693-698
-
Tidskriftsartikel (refereegranskat)abstract
- Changes in supramolecular properties of cellulose I, namely its lateral fibril aggregate dimension (LFAD), in bleached hardwood acid bisulphite pulp during drying was studied using cross-polarization/magic angle spinning carbon-13 nuclear magnetic resonance (CP/MAS 13C-NMR) in combination with spectral fitting. A significant change in aggregate dimensions was noticed when each of the pulp grades were oven dried. The effect of drying was further investigated with pulp samples subjected to different drying methods. A comparison of a harsh oven drying, mild and rapid air drying, and a very mild and slow condition drying showed that the LFAD of the material decreases in the following order: oven drying > air drying > condition drying. The correlation between the total extractable material S10 (%) and LFAD and also the LFAD increment (ΔLFAD in %) are presented and shown to be intimately related. This means that the method of drying influences the size of the fibril aggregate dimensions and depends on the presence of extractable material within the fibre cell wall. Reactivity studies were carried out based on the acetylation of cotton linters and commercial 96α pulp. Results indicate that the initial reaction rate is proportional to the specific surface area of the two cellulose pulp samples. Accordingly, the specific surface area is directly related to initial reactivity of the performed acetylation. We demonstrated that it is possible to control the LFAD and hence specific surface area in laboratory-produced pulps 91α, 92α, and 96α by the drying method. Thus controlling LFAD can probably be one viable route for controlling the initial reactivity of dissolving pulp towards acetylation.
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| 37. |
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| 38. |
- Cortes Ruiz, Maria F., et al.
(författare)
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Structure-properties relationships of defined CNF single-networks crosslinked by telechelic PEGs
- 2024
-
Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 339
-
Tidskriftsartikel (refereegranskat)abstract
- The high structural anisotropy and colloidal stability of cellulose nanofibrils' enable the creation of self-standing fibrillar hydrogel networks at very low solid contents. Adding methacrylate moieties on the surface of TEMPO oxidized CNFs allows the formation of more robust covalently crosslinked networks by free radical polymerization of acrylic monomers, exploiting the mechanical properties of these networks more efficiently. This technique yields strong and elastic networks but with an undefined network structure. In this work, we use acrylate-capped telechelic polymers derived from the step-growth polymerization of PEG diacrylate and dithiothreitol to crosslink methacrylated TEMPO-oxidized cellulose nanofibrils (MATO CNF). This combination resulted in flexible and strong hydrogels, as observed through rheological studies, compression and tensile loading. The structure and mechanical properties of these hydrogel networks were found to depend on the dimensions of the CNFs and polymer crosslinkers. The structure of the networks and the role of individual components were evaluated with SAXS (Small-Angle X-ray Scattering) and photo-rheology. A thorough understanding of hybrid CNF/polymer networks and how to best exploit the capacity of these networks enable further advancement of cellulose-based materials for applications in packaging, soft robotics, and biomedical engineering.
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| 39. |
- Coseri, Sergiu, et al.
(författare)
-
Correction : One-shot carboxylation of microcrystalline cellulose in the presence of nitroxyl radicals and sodium periodate
- 2015
-
Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 5:117, s. 96927-
-
Tidskriftsartikel (refereegranskat)abstract
- Correction for ‘One-shot carboxylation of microcrystalline cellulose in the presence of nitroxyl radicals and sodium periodate’ by Sergiu Coseri et al., RSC Adv., 2015, 5, 85889–85897.The authors regret that the images presented for Fig. 1 and 3 in the original article present incorrect carbohydrate structures. The amended versions of these images, in which the 3-position hydroxyl groups are equatorial rather than axial, are presented below.
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| 40. |
- Coseri, Sergiu, et al.
(författare)
-
One-shot carboxylation of microcrystalline cellulose in the presence of nitroxyl radicals and sodium periodate
- 2015
-
Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 5:104, s. 85889-85897
-
Tidskriftsartikel (refereegranskat)abstract
- Water soluble cellulose derivatives are highly required products for many practical purposes, expanding the limited applications of pure cellulose caused by the highly ordered hydrogen bond network and high crystallinity. In this connection, this paper, presents a new approach to obtain water soluble carboxyl-functionalized cellulosic materials, combining two of the most common selective oxidation protocols for cellulose, i.e. nitroxyl mediated reaction and periodate oxidation, in a one-shot reaction. It was found that, under specific reaction conditions, fully oxidized, 2,3,6-tricarboxy cellulose can be obtained in large amounts. The other valuable oxidized fractions were found to possess large amounts of carboxylic groups, as determined by potentiometric titration. 13C-NMR evidenced the presence of three distinctive carboxylic groups in the fully oxidized product, whereas for the partially oxidized samples, 13C CP-MAS solid-state NMR did not detect any carbonyl signals. The oxidized products were characterized by means of FTIR and X-ray photoelectron spectroscopy (XPS). Moreover, the changes of the degree of polymerization occurring after oxidative treatments were viscometrically determined.
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| 41. |
- Cunha, Ana Gisela, et al.
(författare)
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Topochemical acetylation of cellulose nanopaper structures for biocomposites : mechanisms for reduced water vapour sorption
- 2014
-
Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 21:4, s. 2773-2787
-
Tidskriftsartikel (refereegranskat)abstract
- Moisture sorption decreases dimensional stability and mechanical properties of polymer matrix biocomposites based on plant fibers. Cellulose nanofiber reinforcement may offer advantages in this respect. Here, wood-based nanofibrillated cellulose (NFC) and bacterial cellulose (BC) nanopaper structures, with different specific surface area (SSA), ranging from 0.03 to 173.3 m(2)/g, were topochemically acetylated and characterized by ATR-FTIR, XRD, solid-state CP/MAS C-13-NMR and moisture sorption studies. Polymer matrix nanocomposites based on NFC were also prepared as demonstrators. The surface degree of substitution (surface-DS) of the acetylated cellulose nanofibers is a key parameter, which increased with increasing SSA. Successful topochemical acetylation was confirmed and significantly reduced the moisture sorption in nanopaper structures, especially at RH = 53 %. BC nanopaper sorbed less moisture than the NFC counterpart, and mechanisms are discussed. Topochemical NFC nanopaper acetylation can be used to prepare moisture-stable nanocellulose biocomposites.
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| 42. |
- Eggers, Kai M., 1962-, et al.
(författare)
-
Prevalence and pathophysiological mechanisms of elevated cardiac troponin 1 levels in a population-based sample of elderly subjects
- 2008
-
Ingår i: European Heart Journal. - : Oxford University Press (OUP). - 0195-668X .- 1522-9645. ; 29:18, s. 2252-2258
-
Tidskriftsartikel (refereegranskat)abstract
- AIMS: To evaluate the prevalence of cardiac troponin I (cTnI) elevation in an elderly community population and the association of cTnI levels with cardiovascular risk factors, vascular inflammation, atherosclerosis, cardiac performance, and areas indicative of infarcted myocardium identified by cardiac magnetic resonance imaging. METHODS AND RESULTS: cTnI elevation defined as cTnI levels >0.01 microg/L (Access AccuTnI, Beckman Coulter) was found in 21.8% of the study participants (n = 1005). cTnI > 0.01 microg/L was associated with cardiovascular high-risk features, the burden of atherosclerosis in the carotid arteries, left-ventricular mass, and impaired left-ventricular systolic function. No associations were found between cTnI and inflammatory activity, diastolic dysfunction, or myocardial scars. Male gender (OR 1.6; 95% CI 1.1-2.4), ischaemic ECG changes (OR 1.7; 95% CI 1.1-2.7), and NT-pro-brain natriuretic peptide levels (OR 1.4; 95% CI 1.1-1.7) independently predicted cTnI > 0.01 microg/L. cTnI > 0.01 microg/L correlated also to an increased cardiovascular risk according to the Framingham risk score. CONCLUSION: cTnI > 0.01 microg/L is relatively common in elderly subjects and is associated with cardiovascular high-risk features and impaired cardiac performance. Cardiac troponin determined by a highly sensitive assay might thus serve as an instrument for the identification of subjects at high cardiovascular risk in general populations.
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| 43. |
- Ehn, Andreas, et al.
(författare)
-
Setup for microwave stimulation of a turbulent low-swirl flame
- 2016
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Ingår i: Journal of Physics D: Applied Physics. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 49:18
-
Tidskriftsartikel (refereegranskat)abstract
- An experimental setup for microwave stimulation of a turbulent flame is presented. A low-swirl flame is being exposed to continuous microwave irradiation inside an aluminum cavity. The cavity is designed with inlets for laser beams and a viewport for optical access. The aluminum cavity is operated as a resonator where the microwave mode pattern is matched to the position of the flame. Two metal meshes are working as endplates in the resonator, one at the bottom and the other at the top. The lower mesh is located right above the burner nozzle so that the low-swirl flame is able to freely propagate inside the cylinder cavity geometry whereas the upper metal mesh can be tuned to achieve good overlap between the microwave mode pattern and the flame volume. The flow is characterized for operating conditions without microwave irradiation using particle imaging velocimetry (PIV). Microwave absorption is simultaneously monitored with experimental investigations of the flame in terms of exhaust gas temperature, flame chemiluminescence (CL) analysis as well as simultaneous planar laser-induced fluorescence (PLIF) measurements of formaldehyde (CH2O) and hydroxyl radicals (OH). Results are presented for experiments conducted in two different regimes of microwave power. In the high-energy regime the microwave field is strong enough to cause a breakdown in the flame. The breakdown spark develops into a swirl-stabilized plasma due to the continuous microwave stimulation. In the low-energy regime, which is below plasma formation, the flame becomes larger and more stable and it moves upstream closer to the burner nozzle when microwaves are absorbed by the flame. As a result of a larger flame the exhaust gas temperature, flame CL and OH PLIF signals are increased as microwave energy is absorbed by the flame.
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| 44. |
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| 45. |
- Ek, Monica, et al.
(författare)
-
Production of dissolving grade pulps from non-wood paper grade pulps using enzymatic and chemical pre-treatments for the viscose process
- 2010
-
Konferensbidrag (refereegranskat)abstract
- Cellulose is the most abundant biorenewable material, constitutes an important polymer since it is used as raw material for several products, e.g. Paper and board but also cellulose-based products which have many important applications in the pharmaceutical, textile, food and paint industries. A raw material with high cellulose content and low content of hemicelluloses, residual lignin, extractives and minerals is required for the prodn. of these products, e.g. Cotton and dissolving grade pulp are used. However, the high cost prodn. of dissolving grade pulps has aroused the possibility of upgrading paper grade pulps into dissolving pulps by selective removal of hemicelluloses and subsequent activation of the pulps. This study reports the feasibility to produce dissolving grade pulps from different pulps, i.e. Non-wood paper grade pulps and conventional hardwood kraft pulps, employing enzymic and chem. pretreatments. A monocomponent endoglucanase and a xylanase followed by alk. extn. were tested in order to increase the accessibility and reactivity of the cellulose pulp and decrease the hemicellulose content, resp. An optimization of these treatments in terms of enzyme dosage, incubation time and a possible combination of them was investigated. The treatment effects on reactivity according to Fock's method, viscosity, hemicellulose content and mol. wt. distribution, using size exclusion chromatog. (SEC), were analyzed. The characterization of cellulose structure after the enzymic and chem. treatments was investigated by different techniques.
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| 46. |
- Ekbom, Tomas, et al.
(författare)
-
Methanol production from steel-work off-gases and biomass based synthesis gas
- 2012
-
Ingår i: International Conference on Applied Energy, ICAE 2012.
-
Konferensbidrag (refereegranskat)abstract
- The main objective has been to describe different cases of the methanol production from steel-work off gases (Coke oven gas and Basic oxygen furnace gas) and biomass based synthesis gas. The SSAB steel mill in the town of Luleå, Sweden has been used as a basis to analyze four different methanol production cases.The studied biomass gasification technology is based on a fluidized bed gasifier unit, where the production capacity is determined from case to case coupled to the heat production required to satisfy the local district heating demand. Critical factors are the integration of the gases with availability to the synthesis unit, to balance the steam system of the biorefinery and to meet the district heat demand of Luleå.For each case, the annual production potential of methanol, the overall production efficiencies and the effects on the total steel plant have been estimated.
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| 47. |
- Engström, Gunnar, et al.
(författare)
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Pulmonary function and atherosclerosis in the general population : causal associations and clinical implications
- 2024
-
Ingår i: European Journal of Epidemiology. - : Springer Nature. - 0393-2990 .- 1573-7284. ; 39:1, s. 35-49
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Tidskriftsartikel (refereegranskat)abstract
- Reduced lung function is associated with cardiovascular mortality, but the relationships with atherosclerosis are unclear. The population-based Swedish CArdioPulmonary BioImage study measured lung function, emphysema, coronary CT angiography, coronary calcium, carotid plaques and ankle-brachial index in 29,593 men and women aged 50–64 years. The results were confirmed using 2-sample Mendelian randomization. Lower lung function and emphysema were associated with more atherosclerosis, but these relationships were attenuated after adjustment for cardiovascular risk factors. Lung function was not associated with coronary atherosclerosis in 14,524 never-smokers. No potentially causal effect of lung function on atherosclerosis, or vice versa, was found in the 2-sample Mendelian randomization analysis. Here we show that reduced lung function and atherosclerosis are correlated in the population, but probably not causally related. Assessing lung function in addition to conventional cardiovascular risk factors to gauge risk of subclinical atherosclerosis is probably not meaningful, but low lung function found by chance should alert for atherosclerosis.
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| 48. |
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| 49. |
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- Eriksson, Henrik, 1974, et al.
(författare)
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Full-Custom vs. Standard-Cell Design Flow - An Adder Case Study
- 2003
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Ingår i: Proceedings of Asia South-Pacific Design Automation Conference (ASPDAC), Kitakyushu, 21-24 January 2003. - 0780376595 ; 2003-January, s. 507-510
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Konferensbidrag (refereegranskat)abstract
- Full-custom design is considered superior to standard-cell design when a high-performance circuit is requested. The structured routing of critical wires is considered to be the most important contributor to this performance gap. However, this is only true for bitsliced designs, such as ripple-carry adders, but not for designs with inter-bitslice interconnections spanning several bitslices, such as tree adders and reduction-tree multipliers. It is found that standard-cell design techniques scale better with the data width than full-custom bitsliced layouts for designs dominated by inter-bitslice interconnections.
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