| 1. |
- Berglund, Linn, et al.
(author)
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Production potential of cellulose nanofibers from industrial residues : Efficiency and nanofiber characteristics
- 2016
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In: Industrial crops and products (Print). - : Elsevier BV. - 0926-6690 .- 1872-633X. ; 92, s. 84-92
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Journal article (peer-reviewed)abstract
- The aim of this study was to evaluate the production potential of cellulose nanofibers from two different industrial bio-residues: wastes from the juice industry (carrot) and the beer brewing process (BSG). The mechanical separation of the cellulose nanofibers was by ultrafine grinding. X-ray diffraction (XRD) and Raman spectroscopy revealed that the materials were mechanically isolated without significantly affecting their crystallinity. The carrot residue was more easily bleached and consumed less energy during grinding, using only 0.9 kWh/kg compared to 21 kWh/kg for the BSG. The carrot residue also had a 10% higher yield than the BSG. Moreover, the dried nanofiber networks showed high mechanical properties, with an average modulus and strength of 12.9 GPa and 210 MPa, respectively, thus indicating a homogeneous nanosize distribution. The study showed that carrot residue has great potential for the industrial production of cellulose nanofibers due to its high quality, processing efficiency, and low raw material cost
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| 2. |
- Corvo Alguacil, Marina, 1992-
(author)
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Circularity in Thermal Recycling for Sustainable Carbon Fibers
- 2023
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Licentiate thesis (other academic/artistic)abstract
- The research field of composite materials is particularly fascinating due to the design freedom they offer and the infinite number of constituent combinations, including those that are already explored, and many more that are yet to be tried. One composite material that holds great potential contains carbon in its fiber shape. Carbon fibers possess unique properties that excel in mechanical aspects, as well as interesting electrical and thermal properties that are yet to be fully explored. These fibers are readily available on the market and can be introduced as reinforcement in various lengths and orientations, yielding diverse results depending on the intended effect. Although carbon fiber reinforced polymer composites (CFRP) are present on the market for quite some time, specifically in high-performance applications, they are predominantly used when their performance outweighs their cost. Meanwhile, carbon fiber composite waste is starting to cumulate in noticeable amounts. This waste originates from both, production scrap and end-of-life scenarios, as components introduced in service life in the past 30 years are being decommissioned and discarded. Unfortunately, the prevalent solution for handling this waste is landfilling, due to its ease, affordability, and accessibility. Consequently, substantial amounts of composite waste are accumulating worldwide. Furthermore, it has finally come to our attention that our planet's resources are finite. Our exploitation of these resources has been largely devoid of consideration for the needs of future generations. As a result, recently, sustainability has emerged as a key enabler for a circular economy, driven by increasing environmental concerns and demands from customers and users for market transformation. The implementation of sustainable practices is now underway, albeit at a gradual pace. In summary, we find ourselves facing a trifold predicament: a splendid material being underutilized due to production costs, the cumulative generation of CFRP waste resulting from a lack of foresight and suitable alternatives, and the urgent need to transition towards a circular economy due to resource depletion. This research work aims to address all three challenges by developing an integrated solution. The current work demonstrates that it is possible to recycle carbon fiber model composites through a two-step pyrolysis treatment, a fully mature recycling technology. The study has been done in two stages which are presented in two journal papers included in the thesis. The primary objective of the first paper is to identify and optimize process parameters that maximize the retention of mechanical properties in the recovered fibers. The overall results achieved show good retention value; with over 90% retention on stiffness and 90% on strength. Encouraging results from initial experimental work, have spurred the research focus towards further investigation. Thus, the second paper reports on repetitive manufacturing and recycling cycles of two sets of identical model composites by using the two most effective recycling treatments identified through the parameter optimization. The mechanical performance and structural changes of the recycled fibers are characterized and analyzed. Although further analysis is required, current mechanical behavior shows recovered fibers suitable for secondary applications after two recycling cycles, with an abrupt decay in fiber properties after the third cycle. With the waste challenge under control, through successful recycling of composite waste, it is time to find concrete applications for this research. Having recycled carbon fibers (rCF) with comparable performance to virgin carbon fibers (vCF) opens up opportunities for rCF mats and other intermediate products to compete in previously inaccessible markets.
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| 3. |
- Haglund, Ellinor, et al.
(author)
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The HD-exchange motions of ribosomal protein S6 are insensitive to reversal of the protein-folding pathway
- 2009
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In: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 106:51, s. 21619-21624
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Journal article (peer-reviewed)abstract
- An increasing number of protein structures are found to encompass multiple folding nuclei, allowing their structures to be formed by several competing pathways. A typical example is the ribosomal protein S6, which comprises two folding nuclei (sigma1 and sigma2) defining two competing pathways in the folding energy landscape: sigma1 --> sigma2 and sigma2 --> sigma1. The balance between the two pathways, and thus the order of folding events, is easily controlled by circular permutation. In this study, we make use of this ability to manipulate the folding pathway to demonstrate that the dynamic motions of the S6 structure are independent of how the protein folds. The HD-exchange protection factors remain the same upon complete reversal of the folding order. The phenomenon arises because the HD-exchange motions and the high-energy excitations controlling the folding pathway occur at separated free-energy levels: the Boltzmann distribution of unproductive unfolding attempts samples all unfolding channels in parallel, even those that end up in excessively high barriers. Accordingly, the findings provide a simple rationale for how to interpret native-state dynamics without the need to invoke fluctuations off the normal unfolding reaction coordinate.
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| 4. |
- Hedenström, Mattias, et al.
(author)
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Identification of lignin and polysaccharide modifications in Populus wood by chemometric analysis of 2D NMR spectra from dissolved cell walls
- 2009
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In: Molecular Plant. - : Elsevier BV. - 1674-2052 .- 1752-9867. ; 2:5, s. 933-942
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Journal article (peer-reviewed)abstract
- 2D (13)C-(1)H HSQC NMR spectroscopy of acetylated cell walls in solution gives a detailed fingerprint that can be used to assess the chemical composition of the complete wall without extensive degradation. We demonstrate how multivariate analysis of such spectra can be used to visualize cell wall changes between sample types as high-resolution 2D NMR loading spectra. Changes in composition and structure for both lignin and polysaccharides can subsequently be interpreted on a molecular level. The multivariate approach alleviates problems associated with peak picking of overlapping peaks, and it allows the deduction of the relative importance of each peak for sample discrimination. As a first proof of concept, we compare Populus tension wood to normal wood. All well established differences in cellulose, hemicellulose, and lignin compositions between these wood types were readily detected, confirming the reliability of the multivariate approach. In a second example, wood from transgenic Populus modified in their degree of pectin methylesterification was compared to that of wild-type trees. We show that differences in both lignin and polysaccharide composition that are difficult to detect with traditional spectral analysis and that could not be a priori predicted were revealed by the multivariate approach. 2D NMR of dissolved cell wall samples combined with multivariate analysis constitutes a novel approach in cell wall analysis and provides a new tool that will benefit cell wall research.
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| 5. |
- Janhäll, Sara, 1965-, et al.
(author)
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Release of carbon nanotubes during combustion of polymer nanocomposites in a pilot-scale facility for waste incineration
- 2021
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In: NanoImpact. - : Elsevier BV. - 2452-0748. ; 24
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Journal article (peer-reviewed)abstract
- Nanocomposites, formed by incorporating nanoparticles into a matrix of standard materials, are increasing on the market. Little focus has been directed towards safe disposal and recycling of these new materials even though the disposal has been identified as a phase of the products' life cycle with a high risk of uncontrolled emissions of nanomaterials. In this study, we investigate if the carbon nanotubes (CNTs), when used as a filler in two types of polymers, are fully destructed in a pilot-scale combustion unit designed to mimic the combustion under waste incineration. The two polymer nanocomposites studied, polycarbonate (PC) with CNT and high-density polyethylene (HDPE) with CNT, were incinerated at two temperatures where the lower temperature just about fulfilled the European waste incineration directive while the upper was chosen to be on the safe side of fulfilling the directive. Particles in the flue gas were sampled and analysed with online and offline instrumentation along with samples of the bottom ash. CNTs could be identified in the flue gas in all experiments, although present to a greater extent when the CNTs were introduced in PC as compared to in HDPE. In the case of using PC as polymer matrix, CNTs were identified in 3–10% of the analysed SEM images while for HDPE in only ~0.5% of the images. In the case of PC, the presence of CNTs decreased with increasing bed temperature (from 10% to 3% of the images). The CNTs identified were always in bundles, often coated with remnants of the polymer, forming particles of ~1–4 μm in diameter. No CNTs were identified in the bottom ash, likely explained by the difference in time when the bottom ash and fly ash are exposed to high temperatures (~hours compared to seconds) in the pilot facility. The results suggest that the residence time of the fly ash in the combustion zone is not long enough to allow full oxidation of the CNTs. Thus, the current regulation on waste incineration (requiring a residence time of the flue gas >850 °C during at least 2 s) may not be enough to obtain complete destruction of CNTs in polymer composites. Since several types of CNTs are known to be toxic, we stress the need for further investigation of the fate and toxicity of CNTs in waste treatment processes.
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| 6. |
- Strunk, Peter, et al.
(author)
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Characterization of dissolving pulp by multivariate data analysis of FT-IR and NMR spectra
- 2011
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In: Nordic Pulp & Paper Research Journal. - Stockholm : AB Svensk papperstidning. - 0283-2631 .- 2000-0669. ; 26:4, s. 398-409
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Journal article (peer-reviewed)abstract
- Several grades of dissolving pulps have been analyzed using FT-IR, solid state13C NMR and two dimensional1H-13C HSQC NMR spectroscopy to obtain an extensive data set for further characterization. The selection of the dissolving pulps with high cellulose purity was based on pulping process, wood type and, intrinsic pulp viscosity. Multivariate data analysis was used to investigate how information derived from the spectroscopic data correlate to each of the selection criterion: wood type, process type and viscosity. The spectroscopic methods were also compared with common dissolving pulp analyses to see to what extent spectroscopy can predict pulp analyses.Correlations were found between the spectroscopic data and the pulp characteristics process type and wood type, but not for intrinsic viscosity. A reason for a good correlation to wood type appears to be the hemicelluloses composition, expressed as the xylose:mannose ratio by 2D NMR spectroscopy. For process type, 2D NMR showed the most characteristic property to be the amount of reducing ends in the cellulosic samples, which in turn strongly correlates to lower molecular weight for the sulfite samples as determined by molecular weight distribution.Many common, yet expensive and time consuming, pulp analyses could also be predicted by the achieved models. It can be concluded that investigations of dissolving pulp characteristics, especially concerning different wood and process types, can take advantage of the methods and models presented in this study.
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| 7. |
- Öhman, Anders, et al.
(author)
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Solution structures and backbone dynamics of the ribosomal protein S6 and its permutant P54-55
- 2010
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In: Protein Science. - : Wiley. - 0961-8368 .- 1469-896X. ; 19:1, s. 183-189
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Journal article (peer-reviewed)abstract
- The ribosomal protein S6 from Thermus thermophilus has served as a model system for the study of protein folding, especially for understanding the effects of circular permutations of secondary structure elements. This study presents the structure of a permutant protein, the 96-residue P54-55, and the structure of its 101-residue parent protein S6wt in solution. The data also characterizes the effects of circular permutation on the backbone dynamics of S6. Consistent with crystallographic data on S6wt, the overall solution structures of both P54-55 and S6wt show a β-sheet of four antiparallel β-strands with two α-helices packed on one side of the sheet. In clear contrast to the crystal data, however, the solution structure of S6wt reveals a disordered loop in the region between β-strands 2 and 3 (Leu43-Phe60) instead of a well-ordered stretch and associated hydrophobic mini-core observed in the crystal structure. Moreover, the data for P54-55 show that the joined wild-type N- and C-terminals form a dynamically robust stretch with a hairpin structure that complies with the in silico design. Taken together, the results explain why the loop region of the S6wt structure is relatively insensitive to mutational perturbations, and why P54-55 is more stable than S6wt: the permutant incision at Lys54-Asp55 is energetically neutral by being located in an already disordered loop whereas the new hairpin between the wild-type N- and C-termini is stabilizing.
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| 8. |
- Öman, Tommy, 1974-, et al.
(author)
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Identification of metabolites from 2D 1H-13C HSQC NMR using peak correlation plots
- 2014
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In: BMC Bioinformatics. - : Springer Science and Business Media LLC. - 1471-2105. ; 15
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Journal article (peer-reviewed)abstract
- Background: Identification of individual components in complex mixtures is an important and sometimes daunting task in several research areas like metabolomics and natural product studies. NMR spectroscopy is an excellent technique for analysis of mixtures of organic compounds and gives a detailed chemical fingerprint of most individual components above the detection limit. For the identification of individual metabolites in metabolomics, correlation or covariance between peaks in 1H NMR spectra has previously been successfully employed. Similar correlation of 2D 1H-13C Heteronuclear Single Quantum Correlation spectra was recently applied to investigate the structure of heparine. In this paper, we demonstrate how a similar approach can be used to identify metabolites in human biofluids (post-prostatic palpation urine).Results: From 50 1H-13C Heteronuclear Single Quantum Correlation spectra, 23 correlation plots resembling pure metabolites were constructed. The identities of these metabolites were confirmed by comparing the correlation plots with reported NMR data, mostly from the Human Metabolome Database.Conclusions: Correlation plots prepared by statistically correlating 1H-13C Heteronuclear Single Quantum Correlation spectra from human biofluids provide unambiguous identification of metabolites. The correlation plots highlight cross-peaks belonging to each individual compound, not limited by long-range magnetization transfer as conventional NMR experiments.
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| 9. |
- Öman, Tommy, 1974-
(author)
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Multivariate Analysis of 2D-NMR Spectroscopy : Applications in wood science and metabolomics
- 2013
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Doctoral thesis (other academic/artistic)abstract
- Wood is our most important renewable resource. We need better quality and quantity both according to the wood itself and the processes that are using wood as a raw material. Hence, the understanding of the chemical composition of the wood is of high importance. Improved and new methods for analyzing wood are important to achieve better knowledge about both refining processes and raw material. The combination of NMR and multivariate analyses (MVA) is a powerful method for these analyses but so far it has been limited mainly to 1D NMR. In this project, we have developed methods for combining 2D NMR and MVA in both wood analysis and metabolomics. This combination was used to compare samples from normal wood and tension wood, and also trees with a down regulation of a pectin responsible gene. Dissolving pulp was also examined using the same combination of 2D-NMR and MVA, together with FT-IR and solid state 13C CP-MAS NMR. Here we focused on the difference between wood type (softwood and hardwood), process type (sulfite and sulfate) and viscosity. These methods confirmed and added knowledge about the dissolving pulp. Also reactivity was compared in relation to morphology of the cellulose and pulp composition. Based on the method and software used in the wood analysis projects, a new method called HSQC-STOCSY was developed. This method is especially suited for assignment of substances in complex mixtures. Peaks in 2D NMR spectra that correlate between different samples are plotted in correlation plots resembling regular NMR spectra. These correlation plots have great potential in identifying individual components in complex mixtures as shown here in a metabolic data set. This method could potentially also be used in other areas such as drug/target analyses, protein dynamics and assignment of wood spectra.
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| 10. |
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