| 1. |
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| 2. |
- Azhar, Shoaib, 1980-, et al.
(författare)
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Extraction of hemicelluloses from fiberized spruce wood
- 2015
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 117, s. 19-24
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Tidskriftsartikel (refereegranskat)abstract
- A novel mechanical pre-treatment method was used to separate the wood chips into fiber bundles in order to extract high molecular weight wood polymers. The mechanical pre-treatment involved chip compression in a conical plug-screw followed by defibration in a fiberizer. The fiberized wood was treated with hot water at various combinations of time and temperature in order to analyze the extraction yield of hemicelluloses at different conditions. Nearly 6 mg/g wood of galactoglucomannan was obtained at 90◦C/120min which was about three times more than what could be extracted from wood chips. The extracted carbohydrates had molecular weight ranging up to 60 kDa. About 10% of each of the extracted material had a molecular weight above 30 kDa. The extraction liquor could also be reused for consecutive extractions with successive increase in the extraction yield of hemicelluloses.
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| 3. |
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| 4. |
- Berglund, Jennie, et al.
(författare)
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A molecular dynamics study of the effect of glycosidic linkage type in the hemicellulose backbone on the molecular chain flexibility
- 2016
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Ingår i: The Plant Journal. - : John Wiley & Sons Ltd.. - 0960-7412 .- 1365-313X. ; 88:1, s. 56-70
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Tidskriftsartikel (refereegranskat)abstract
- The macromolecular conformation of the constituent polysaccharides in lignocellulosic biomass influences their supramolecular interactions, and therefore their function in plants and their performance in technical products. The flexibility of glycosidic linkages from the backbone of hemicelluloses was studied by evaluating the conformational freedom of the φ and ψ dihedral angles using molecular dynamic simulations, additionally selected molecules were correlated with experimental data by NMR spectroscopy. Three types of β-(1→4) glycosidic linkages involving the monosaccharides (Glcp, Xylp and Manp) present in the backbone of hemicelluloses were defined. Different di- and tetrasaccharides with combinations of such sugar monomers from hemicelluloses were simulated and free energy maps of the φ - ψ space and hydrogen bonding patterns were obtained. The glycosidic linkage between Glc-Glc or Glc-Man (C-type) was the stiffest with mainly one probable conformation; the linkage from Man-Man or Man-Glc (M-type) was similar but with an increased probability for an alternative conformation making it more flexible, and the linkage between two Xyl-units (X-type) was the most flexible with two almost equally populated conformations. Glycosidic linkages of the same type showed essentially the same conformational space in both disaccharides and in the central region of tetrasaccharides. Different probabilities of glycosidic linkage conformations in the backbone of hemicelluloses can be directly estimated from the free energy maps, which to a large degree affect the overall macromolecular conformations of these polymers. The information gained contributes to an increased understanding of hemicelluloses’ function both in the cell wall and in technical products.
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| 5. |
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| 6. |
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| 7. |
- Berglund, Jennie, et al.
(författare)
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The structure of galactoglucomannan impacts the degradation under alkaline conditions
- 2018
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Ingår i: Cellulose. - : Springer. - 0969-0239 .- 1572-882X.
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Tidskriftsartikel (refereegranskat)abstract
- Galactoglucomannan (GGM) from sprucewas studied with respect to the degradation behavior inalkaline solution. Three reference systems includinggalactomannan from locust bean gum, glucomannanfrom konjac and the linear water-soluble carboxymethylcellulose were studied with focus onmolecular weight, sugar composition, degradationproducts, as well as formed oligomers, to identifyrelative structural changes in GGM. Initially allmannan polysaccharides showed a fast decrease inthe molecular weight, which became stable in the laterstage. The degradation of the mannan polysaccharidescould be described by a function corresponding to thesum of two first order reactions; one slow that wasascribed to peeling, and one fast that was connectedwith hydrolysis. The galactose side group wasstable under conditions used in this study (150 min,90 C, 0.5 M NaOH). This could suggest that, apartfrom the covalent connection to C6 in mannose, thegalactose substitutions also interact non-covalentlywith the backbone to stabilize the structure againstdegradation. Additionally, the combination of differentbackbone sugars seems to affect the stability of thepolysaccharides. For carboxymethyl cellulose thedegradation was linear over time which furthersuggests that the structure and sugar composition playan important role for the alkaline degradation. Moleculardynamics simulations gave details about theconformational behavior of GGM oligomers in watersolution, as well as interaction between the oligomersand hydroxide ions.
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| 8. |
- Berglund, Jennie
(författare)
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Wood Hemicelluloses - Fundamental Insights on Biological and Technical Properties
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Hemicelluloses are a group of heterogeneous polysaccharides representing around 30 % of wood where the dominating types are xylans, glucomannans and xyloglucans. Hemicelluloses complex molecular structure makes it difficult to understand the relationship between structure and properties entirely, and their biological role is not yet fully verified. Additionally, hemicelluloses are sensitive to chemical processing and are not utilized to their full potentials for production of value-added products such as materials, additives to food and pharmaceutical products, etc. Increased knowledge regarding their functions is important for the development of both processes and products. The aim with this work has therefore been to increase the fundamental understanding about how the structure and properties of wood hemicelluloses are correlated, and properties such as flexibility, interaction with cellulose, solubility, resistance to chemical-, thermal-, and enzymatic degradation have been explored.Molecular dynamics (MD) simulations were used to, in detail, study the structures found in wood hemicelluloses. The flexibility was evaluated by comparing the impact of backbone sugars on the conformational space and also the impact of side groups was considered. Based on the conformational space of backbone glycosidic linkages the flexibility order of hemicelluloses in an aqueous environment was determined to be: xylan > glucomannan > xyloglucan. Additionally, the impact of xylan structure on cellulose interaction was evaluated by MD methods.Hemicelluloses were extracted from birch and spruce, and were used to fabricate different composite hydrogels with bacterial cellulose. These materials were studied with regards to mechanical properties, and it was shown that galactoglucomannans mainly contributed to an increased modulus in compression, whereas the most significant effect from xylan was increased strain under uniaxial tensile testing. Besides, other polysaccharides of similar structure as galactoglucomannans were modified and used as pure, well defined, models. Acetyl groups are naturally occurring decorations of wood hemicelluloses and can also be chemically introduced. Here, mannans with different degrees of acetylation were prepared and the influence of structure on solubility in water and the organic solvent DMSO were evaluated. Furthermore, the structure and water solubility influenced the interaction with cellulose. Acetylation also showed to increase the thermal and biological stability of mannans.With chemical pulping processes in mind, the degradability of spruce galactoglucomannans in alkaline solution were studied with regards to the structure, and the content of more or less stable structural regions were proposed.
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| 9. |
- Dogaris, Ioannis, et al.
(författare)
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Critical parameters for tall oil separation I : The importance of the ratio of fatty acids to rosin acids
- 2019
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Ingår i: TAPPI Journal. - : TECH ASSOC PULP PAPER IND INC. - 0734-1415. ; 18:9, s. 547-555
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Tidskriftsartikel (refereegranskat)abstract
- Tall oil is a valuable byproduct in chemical pulping of wood, and its fractions have a large spectrum of applications as chemical precursors, detergents, and fuel. High recovery of tall oil is important for the economic and environmental profile of chemical pulp mills. The purpose of this study was to investigate critical parameters of tall oil separation from black liquor. To investigate this in a controlled way, we developed a model test system using a "synthetic" black liquor (active cooking chemicals OH- and HS- ions), a complete process for soap skimming, and determination of recovered tall oil based on solvent extraction and colorimetric analysis, with good reproducibility. We used the developed system to study the effect of the ratio of fatty acids to rosin acids on tall oil separation. When high amounts of rosin acids were present, tall oil recovery was low, while high content of fatty acids above 60% significantly promoted tall oil separation. Therefore, manipulating the content of fatty acids in black liquor before the soap skimming step can significantly affect the tall oil solubility, and hence its separation. The findings open up chemical ways to improve the tall oil yield. Application: Controlling the ratio of fatty acids to rosin acids in kraft pulping can significantly affect the tall oil separation and improve its yield and quality.
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| 10. |
- Dogaris, Ioannis, et al.
(författare)
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Study on tall oil solubility for improved resource recovery in chemical pulping of wood
- 2019
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Ingår i: Abstracts of Papers of the American Chemical Society. - : American Chemical Society (ACS). - 0065-7727. ; 257
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Tall oil is one of the most valuable by products in chemical pulpingof wood and is considered an important renewable alternative to petroleum.Its fractions have a large spectrum of applications including chemicalprecursors, detergents and energy. High recovery of tall oil is important forthe economic, sustainability, and environmental profile of industrial chemicalpulping. The purpose of this study was to develop ways to increase the yieldof tall oil based on its solubility in black liquors.To investigate this in a controlled way, a model system with a “synthetic”black liquor and a complete methodology for soap skimming anddetermination of recovered tall oil was developed based on solvent extractionand colorimetric analysis with good reproducibility. This model system allowsinvestigations of different parameters in small scale with high control overdifferent conditions.The developed system was used to study the effect of fatty acid addition andthe effect of lignin content on improving tall oil recovery. The presence ofrosin acids in the black liquor significantly reduced soap separation, whileincreasing the fatty acid content up to 60-70% greatly improved soaprecovery. Addition of lignin reduced tall oil recovery in the case of liquors withmore than 50% fatty acids, but slightly increased recovery in liquors withmore than 50% rosin acids. Furthermore, the presence of some ligninseemed to promote separation of the tall oil (reduced its solubility), while highamounts led to inhibition of its recovery.The experimental results clearly indicated that manipulating the content offatty acids and/or lignin before the soap skimming step significantly affect thetall oil solubility, opening up for chemical ways to improve its recovery.However, experiments in real industrial liquors and pulp mill conditions shouldbe considered to assess the actual tall oil yield improvement and processeconomics.
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| 11. |
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| 12. |
- Giummarella, Nicola, et al.
(författare)
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Lignin Prepared by Ultrafiltration of Black Liquor : Investigation of Solubility, Viscosity, and Ash Content
- 2016
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Ingår i: BioResources. - : North Carolina State University. - 1930-2126. ; 11:2, s. 3494-3510
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Tidskriftsartikel (refereegranskat)abstract
- Technical lignin, which can be potentially obtained in large amounts as a by-product from kraft pulping, represents a potential resource for manufacturing fuels and chemicals. Upgrading of lignin, by lowering its molecular weight, is a valuable alternative to precipitation from black liquor, which occurs in the Lignoboost process. The solubility properties of Lignoboost lignin and filtered lignin in a number of technically feasible solvents were compared, and it was found that both lignins were dissolved in similar solvents. With the exception of furfural, the best lignin solvents generally were organic solvents miscible with water, such as methanol. It was possible to dissolve more filtered lignin in higher concentrations than Lignoboost lignin; additionally, the viscosities of the filtered lignin solutions were also considerably lower than those of Lignoboost lignin, especially at higher concentrations. Methods for non-organic component removal from filtrated lignin were tested, and it was concluded that several cold acidic treatments after dewatering can lower the ash content to values below 0.5% by weight.
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| 13. |
- Gruber, Hans, 1983, et al.
(författare)
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Effect of Powder Recycling in Electron Beam Melting on the Surface Chemistry of Alloy 718 Powder
- 2019
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Ingår i: Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science. - : Springer Science and Business Media LLC. - 1073-5623. ; 50:9, s. 4410-4422
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Tidskriftsartikel (refereegranskat)abstract
- Process-induced degradation of the powder feedstock in additive manufacturing may have a negative influence on the final properties of built components. Consequently, it may lower the cost-effectiveness of powder bed additive manufacturing, which relies on recycling of the nonconsumed powder. This is especially the case for production of high-performance aero engine components where high material and process reliability is required. This study comprises a detailed investigation on the degradation of Alloy 718 powder during multicycle electron beam melting (EBM). The surface-sensitive analysis methods, X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES), were combined with scanning electron microscopy (SEM) to depict the differences in surface morphology, and surface composition of powder samples exposed to varying numbers of re-use cycles. The results show a significant change in surface characteristics after exposing the powder to the process and the environment in the build chamber. The virgin powder is covered mainly by a relatively thin and homogeneous oxide layer. The re-used powder, however, has undergone transformation to a heterogeneous oxide layer, rich in thermodynamically stable Al-rich oxide particulates, which started already during the first build cycle. Significant growth of the Al-rich oxide occurs via selective oxidation of Al under the conditions in the build chamber, including both pick-up of oxygen from the process atmosphere and redistribution of initial surface-bound oxygen from less-stable products like Ni-oxide and/or hydroxide.
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| 14. |
- Hansson, Martin, et al.
(författare)
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Björketorpstenen, Vång och en helig förbannelse
- 2016
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Ingår i: Vikten av Vång : en järnåldersplats tar form - en järnåldersplats tar form. - 9789198259827 ; , s. 23-32
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Bokkapitel (populärvet., debatt m.m.)
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| 15. |
- Henriksson, Emma, et al.
(författare)
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SIK2 regulates CRTCs, HDAC4 and glucose uptake in adipocytes
- 2015
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Ingår i: Journal of Cell Science. - : The Company of Biologists. - 0021-9533 .- 1477-9137. ; 128:3, s. 472-486
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Tidskriftsartikel (refereegranskat)abstract
- Salt-inducible kinase 2 (SIK2) is an AMP-activated protein kinase (AMPK) related kinase abundantly expressed in adipose tissue. Our aim was to identify molecular targets and functions of SIK2 in adipocytes, and to address the role of PKA-mediated phosphorylation of SIK2 on Ser358. Modulation of SIK2 in adipocytes resulted in altered phosphorylation of CREB-regulated transcription co-activator 2 (CRTC2), CRTC3 and class IIa histone deacetylase 4 (HDAC4). Furthermore, CRTC2, CRTC3, HDAC4 and protein phosphatase 2A (PP2A) interacted with SIK2, and the binding of CRTCs and PP2A to wild-type but not Ser358Ala SIK2, was reduced by cAMP elevation. Silencing of SIK2 resulted in reduced GLUT4 (also known as SLC2A4) protein levels, whereas cells treated with CRTC2 or HDAC4 siRNA displayed increased levels of GLUT4. Overexpression or pharmacological inhibition of SIK2 resulted in increased and decreased glucose uptake, respectively. We also describe a SIK2-CRTC2-HDAC4 pathway and its regulation in human adipocytes, strengthening the physiological relevance of our findings. Collectively, we demonstrate that SIK2 acts directly on CRTC2, CRTC3 and HDAC4, and that the cAMP-PKA pathway reduces the interaction of SIK2 with CRTCs and PP2A. Downstream, SIK2 increases GLUT4 levels and glucose uptake in adipocytes.
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| 16. |
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| 17. |
- Henriksson, Mikael, et al.
(författare)
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A novel statistical model of the dual pathway atrioventricular node during atrial fibrillation
- 2016
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Ingår i: Computing in Cardiology. - 9781509006854 ; 42, s. 473-476
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Konferensbidrag (refereegranskat)abstract
- The atrioventricular (AV) node plays an important role during atrial fibrillation (AF). In particular, the refractoriness of its cells influences the conduction of atrial impulses to the ventricles and, thus, the ventricular response. This study introduces a novel statistical model of the AV node, accounting for pathway switching, which can be used for non-invasive assessment of the refractory properties of the slow and the fast AV nodal pathway during AF, using the atrial fibrillatory rate and the series of RR intervals obtained from the ECG. A number of simulated histograms is presented, illustrating that even though only four parameters are used to characterize the AV node, the model is capable of representing a wide range of different RR interval series. Estimation of model parameters is evaluated with simulated RR interval series. It is shown that a signal consisting of 2400 RR intervals is sufficient for accurate parameter estimation, with an average estimation error less than 50 ms in all parameters. It is concluded that the model offers a novel way to obtain information regarding AV nodal refractoriness from the ECG.
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| 18. |
- Henriksson, Mikael, et al.
(författare)
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A Statistical Atrioventricular Node Model Accounting for Pathway Switching During Atrial Fibrillation
- 2016
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Ingår i: IEEE Transactions on Biomedical Engineering. - 1558-2531. ; 63:9, s. 1842-1849
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Tidskriftsartikel (refereegranskat)abstract
- Objective: The atrioventricular (AV) node plays a central role in atrial fibrillation (AF) as it influences the conduction of impulses from the atria into the ventricles. In the present paper, the statistical dual pathway AV node model, previously introduced by us, is modified so that it accounts for atrial impulse pathway switching even if the preceding impulse did not cause a ventricular activation. Methods: The proposed change in model structure implies that the number of model parameters subjected to maximum likelihood estimation is reduced from five to four. The model is evaluated using the data acquired in the RATe control in Atrial Fibrillation (RATAF) study, involving 24- h ECG recordings from 60 patients with permanent AF. Results: When fitting the models to the RATAF database, similar results were obtained for both the present and the previous model, with a median fit of 86%. The results show that the parameter estimates characterizing refractory period prolongation exhibit considerably lower variation when using the present model, a finding that may be ascribed to fewer model parameters. Conclusion: The new model maintains the capability to model RR intervals, while providing more reliable parameters estimates. Significance: The model parameters are expected to convey novel clinical information, and may be useful for predicting the effect of rate control drugs.
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| 19. |
- Henriksson, Mikael
(författare)
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Arkeologiska förväntningar i mötet med ett landskap : Stenålderns Blekinge ur ett kunskapsperspektiv
- 2019
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This study is about archaeological knowledge production. It is also about what kind of impact such knowledge may have on an antiquarian/archaeological practice as well as on society as a whole. The work focuses broadly on Stone Age archaeology and specifically on the middle-Mesolithic Age in the county of Blekinge in the South East of Sweden.Until the late 1990’s, large-scale archaeological excavations in this region were rare. In particular, there were significant gaps in early- and middle-Mesolithic archaeology of other regions. In particular, the study brings up the relationship with the defined Kongemose culture's settlements in Southern Scandinavia. From a knowledge perspective the study discusses how different kinds of methodological practices are important for both archaeology and society, to be able to see and understand a more complete historical picture. Based on this, the focus shifts the role of museums within regional archaeology. The study here argues for a more strategically executed dissemination and presentation of archaeological knowledge towards different stakeholders.
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| 20. |
- Henriksson, Mikael, et al.
(författare)
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Changes in f-wave characteristics during cryoballoon catheter ablation
- 2018
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Ingår i: Physiological Measurement. - : IOP Publishing. - 0967-3334 .- 1361-6579. ; 39:10
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: Changes in ECG-derived parameters are studied in atrial fibrillation (AF) patients undergoing cryoballoon catheter ablation.APPROACH: Parameters characterizing f-wave frequency, morphology by phase dispersion, and amplitude are estimated using a model-based statistical approach. These parameters are studied before, during, and after ablation, as well as for AF type (paroxysmal/persistent). Seventy-seven (49/28 paroxysmal/persistent) AF patients undergoing de novo catheter ablation are included in the study, out of which 31 (16/15 paroxysmal/persistent) were in AF during the whole procedure. A signal quality index (SQI) is used to identify analyzable segments.MAIN RESULTS: f-wave frequency decreased significantly during ablation (p = 0.001), in particular after ablation of the inferior right pulmonary vein (p < 0.05). Frequency and phase dispersion differed significantly between paroxysmal and persistent AF (p = 0.001 and p < 0.05, respectively).SIGNIFICANCE: This study demonstrates that a decrease in f-wave frequency can be distinguished during catheter ablation. The use of an SQI ensures reliable analysis and produces results significantly different from those obtained without an SQI.
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| 21. |
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| 22. |
- Henriksson, Mikael, et al.
(författare)
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Model-based Assessment of f-Wave Signal Quality in Patients with Atrial Fibrillation
- 2018
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Ingår i: IEEE Transactions on Biomedical Engineering. - 1558-2531. ; 65:11, s. 2600-2611
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Tidskriftsartikel (refereegranskat)abstract
- Objective: The detection and analysis of atrial fibrillation (AF) in the ECG is greatly influenced by signal quality. The present study proposes and evaluates a model-based f-wave signal quality index (SQI), denoted S, for use in the QRST-cancelled ECG signal. Methods: S is computed using a harmonic f-wave model, allowing for variation in frequency and amplitude. The properties of S are evaluated on both f-waves and P-waves using 378 12-lead ECGs, 1875 single-lead ECGs, and simulated signals. Results: S decreases monotonically when noise is added to f-wave signals, even for noise which overlaps spectrally with f-waves. Moreover, S is shown to be closely associated with the accuracy of AF frequency estimation, where S>0.3 implies accurate estimation. When S is used as a measure of f-wave presence, AF detection performance improves: the sensitivity increases from 97.0% to 98.1% and the specificity increases from 97.4% to 97.8% when compared to the reference detector. Conclusion: The proposed SQI represents a novel approach to assessing f-wave signal quality, as well as to determining whether f-waves are present. Significance: The use of S improves the detection of AF and benefits the analysis of noisy ECGs.
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| 23. |
- Henriksson, Mikael
(författare)
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Modelling and Quality Assessment of Atrial Fibrillatory Waves
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This doctoral thesis revolves around the analysis of electrocardiogram (ECG) signals during atrial fibrillation (AF). Special emphasis is put on the atrial fibrillatory waves, sometimes called the f-waves, which is the ECG component reflecting the electrical activity of the atria. The thesis comprises an introduction and five papers that introduce and apply methods on ECG-based analysis of AF. Paper~I deals with modelling of the relationship between atrial and ventricular activity while papers~II--V deal with the modeling, analysis and quality assessment of the f-waves, the atrial activity component of the ECG.Paper~I presents a novel statistical dual pathway model of the atrioventricular (AV) node during AF. The model accounts for pathway switching, meaning that atrial impulses may alternate between arriving at the slow and the fast pathway, even if the preceding impulse did not cause a ventricular activation. Comparison between the present model, defined by four parameters, and a reference model, defined by five parameters, does not reveal any difference in modelling capability. However, parameter estimates of the present model exhibit considerably lower variation, a finding that may be ascribed to the reduction of model parameters. Paper~II proposes an f-wave signal quality index (SQI). The SQI is computed using a harmonic f-wave model which allows for variation in frequency and amplitude. Unlike the noise level estimator used for comparison, the f-wave SQI reflects signal quality adequately also when the spectral content of the noise overlaps with that of the observed f-waves. The SQI is shown to be highly associated with f-wave presence, obtaining considerably smaller values when computed from non-AF signals, which is exploited to improve the performance of an AF detector.Paper~III investigates the signal quality aspects of 24h tracking of the dominant atrial frequency (DAF), using the f-wave SQI from Paper~II. The use of the SQI reveals that 40\% of all 5-s signal segments of the database should be excluded due to poor quality, with the recordings of some patients being completely removed. Removal of the noisy segments reduced the variation of the DAF trend during both day- and night-time . A decrease in signal quality is observed during veloergometry exercise, with the quality restored immediately afterwards. Paper~IV investigates the f-wave changes occurring during pulmonary vein isolation, a treatment option for AF patients. Three f-wave parameters, derived from the harmonic f-wave model from Paper~II, are included -- the DAF, the f-wave amplitude, and a novel regularity parameter named the phase dispersion. All three f-wave parameters correlate with clinical characteristics, but none of them can predict AF recurrence. However, the DAF decreases significantly during the procedure. Paper~V investigates the reproducibility of f-wave parameters, including the three from paper~IV as well as the spectral organization index and spatiotemporal variability, which have been included in previous studies on f-wave analysis. For each parameter, the variance ratio between the inter- and intrapatient variance, is computed, a larger ratio corresponding to better parameter stability and reproducibility. A substantial difference in inter- and intrapatient variation is found among different parameters, with the DAF and f-wave amplitude obtaining considerably larger variance ratios than the rest.In summary, this thesis presents and evaluates tools for ECG-based AF analysis with special attention on robustness and quality control. The SQI presented in Paper~II is applied in Paper~III--V, and it is concluded that some kind of quality assessment should be considered in all future studies involving f-wave analysis.
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| 24. |
- Henriksson, Mikael, et al.
(författare)
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Signal quality assessment of f-waves in atrial fibrillation
- 2017
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Ingår i: 2017 Computing in Cardiology (CinC). - 2325-8861. - 9781538645550 - 9781538666302
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Konferensbidrag (refereegranskat)abstract
- Ambulatory ECG recordings are frequently corrupted by artifacts caused by, e.g., muscle activity or moving electrodes, which complicates the analysis of f-waves and motivates signal quality assessment to improve the reliability of f-wave analysis. Although many methods have been developed for assessing the quality of ECG signals in general, no method deals specifically with f-waves. This study proposes a novel signal quality index (SQI), using a modelbased approach for assessment of f-wave signal quality. To evaluate the performance of the SQI, 189 5-s recordings of f-waves from AF patients are studied, as is the same number of recordings with motion artifacts and electrode movements taken from the MIT-BIH Noise Stress Test Database. The signal quality index is capable of discriminating between f-waves and noisy recordings with an accuracy of 98%. The results suggest that the proposed signal quality index correctly identifies noisy recordings, and can be used to improve the reliability of f-wave analysis.
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| 25. |
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| 26. |
- Karlsson, Terese, 1979-, et al.
(författare)
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LMO7 and LIMCH1 interact with LRIG proteins in lung cancer, with prognostic implications for early-stage disease
- 2018
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Ingår i: Lung Cancer. - : Elsevier BV. - 0169-5002 .- 1872-8332. ; 125, s. 174-184
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: The human leucine-rich repeats and immunoglobulin-like domains (LRIG) protein family comprises the integral membrane proteins LRIG1, LRIG2 and LRIG3. LRIG1 is frequently down-regulated in human cancer, and high levels of LRIG1 in tumor tissue are associated with favorable clinical outcomes in several tumor types including non-small cell lung cancer (NSCLC). Mechanistically, LRIG1 negatively regulates receptor tyrosine kinases and functions as a tumor suppressor. However, the details of the molecular mechanisms involved are poorly understood, and even less is known about the functions of LRIG2 and LRIG3. The aim of this study was to further elucidate the functions and molecular interactions of the LRIG proteins.Materials and methods: A yeast two-hybrid screen was performed using a cytosolic LRIG3 peptide as bait. In transfected human cells, co-immunoprecipitation and co-localization experiments were performed. Proximity ligation assay was performed to investigate interactions between endogenously expressed proteins. Expression levels of LMO7 and LIMCH1 in normal and malignant lung tissue were investigated using qRT-PCR and through in silico analyses of public data sets. Finally, a clinical cohort comprising 355 surgically treated NSCLC cases was immunostained for LMO7.Results: In the yeast two-hybrid screen, the two paralogous proteins LMO7 and LIMCH1 were identified as interaction partners to LRIG3. LMO7 and LIMCH1 co-localized and co-immunoprecipitated with both LRIG1 and LRIG3. Endogenously expressed LMO7 was in close proximity of both LRIG1 and LRIG3. LMO7 and LIMCH1 were highly expressed in normal lung tissue and down-regulated in malignant lung tissue. LMO7 immunoreactivity was shown to be a negative prognostic factor in LRIG1 positive tumors, predicting poor patient survival.Conclusion: These findings suggest that LMO7 and LIMCH1 physically interact with LRIG proteins and that expression of LMO7 is of clinical importance in NSCLC.
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| 27. |
- Kvarnbrink, Samuel, et al.
(författare)
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LRIG1 is a prognostic biomarker in non-small cell lung cancer
- 2015
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Ingår i: Acta Oncologica. - : Taylor & Francis. - 1651-226X .- 0284-186X. ; 54:8, s. 1113-1119
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Tidskriftsartikel (refereegranskat)abstract
- Background. The leucine-rich repeats and immunoglobulin-like domains (LRIG) family of transmembrane proteins are involved in the regulation of cellular signal transduction. LRIG1 is an endogenous inhibitor of receptor tyrosine kinases (RTKs) and an emerging tumor suppressor. In the lung epithelium, the expression of LRIG1 is downregulated by tobacco smoking, and further downregulated in lung squamous cell carcinoma. Material and methods. The expression of LRIG proteins were analyzed in 347 cases of non-small cell lung cancer (NSCLC) by immunohistochemistry, and LRIG1 mRNA expression was evaluated in 807 lung cancer samples in silico in the Oncomine database. Potential associations between the expression data and the clinical parameters, including patient survival, were investigated. Results. Expression of the LRIG1 protein was found to be an independent prognostic factor in NSCLC, whereas expression of LRIG2 or LRIG3 did not correlate with patient survival. The levels of LRIG1 mRNA also correlated with the survival of NSCLC patients. Conclusion. These findings demonstrate that LRIG1 is an independent prognostic factor in patients with NSCLC that could be important in future decision-making algorithms for adjuvant lung cancer treatment.
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| 28. |
- Lilja, Mona, 1971, et al.
(författare)
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(Re)thinking the Precarity of Swedish Migrants: Governing through Decelerations and Timescapes
- 2019
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Ingår i: Journal of Refugee Studies. - : Oxford University Press (OUP). - 0951-6328 .- 1471-6925. ; 32:1, s. 144-161
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Tidskriftsartikel (refereegranskat)abstract
- This article uses the concept of ‘time’ in order to better understand the situation of precarious migrants in Sweden. Through analysing a number of reports and interviews undertaken with newly arrived migrants in Sweden, it displays how different temporal understandings of the migrants are linked to and managed by governing bodies, laws and regulations. The article centres around two related research questions: (i) What constructions of time are used in the governing of precarious migrants? and (ii) How do these migrants understand their own and society’s time?
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| 29. |
- Mao, Feng, et al.
(författare)
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Lrig1 is a haploinsufficient tumor suppressor gene in malignant glioma
- 2018
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Ingår i: Oncogenesis. - : Nature Publishing Group. - 2157-9024. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Recently, a genome-wide association study showed that a single nucleotide polymorphism (SNP) —rs11706832—in intron 2 of the human LRIG1 (Leucine-rich repeats and immunoglobulin-like domains 1) gene is associated with susceptibility to glioma. However, the mechanism by which rs11706832 affects glioma risk remains unknown; additionally, it is unknown whether the expression levels of LRIG1 are a relevant determinant of gliomagenesis. Here, we investigated the role of Lrig1 in platelet-derived growth factor (PDGF)-induced experimental glioma in mice by introducing mono-allelic and bi-allelic deletions of Lrig1 followed by inducing gliomagenesis via intracranial retroviral transduction of PDGFB in neural progenitor cells. Lrig1 was expressed in PDGFB-induced gliomas in wild-type mice as assessed using in situ hybridization. Intriguingly, Lrig1-heterozygous mice developed higher grade gliomas than did wild-type mice (grade IV vs. grade II/III, p = 0.002). Reciprocally, the ectopic expression of LRIG1 in the TB107 high-grade human glioma (glioblastoma, grade IV) cell line decreased the invasion of orthotopic tumors in immunocompromised mice in vivo and reduced cell migration in vitro. Concomitantly, the activity of the receptor tyrosine kinase MET was downregulated, which partially explained the reduction in cell migration. In summary, Lrig1 is a haploinsufficient suppressor of PDGFB-driven glioma, possibly in part via negative regulation of MET-driven cell migration and invasion. Thus, for the first time, changes in physiological Lrig1 expression have been linked to gliomagenesis, whereby the SNP rs11706832 may affect glioma risk by regulating LRIG1 expression.
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| 30. |
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| 31. |
- Martinez-Abad, Antonio, et al.
(författare)
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Regular Motifs in Xylan Modulate Molecular Flexibility and Interactions with Cellulose Surfaces
- 2017
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Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 1532-2548 .- 0032-0889. ; 175:4, s. 1579-1592
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Tidskriftsartikel (refereegranskat)abstract
- Xylan is tightly associated with cellulose and lignin in secondary plant cell walls, contributing to its rigidity and structural integrity in vascular plants. However, the molecular features and the nanoscale forces that control the interactions among cellulose microfibrils, hemicelluloses, and lignin are still not well understood. Here, we combine comprehensive mass spectrometric glycan sequencing and molecular dynamics simulations to elucidate the substitution pattern in softwood xylans and to investigate the effect of distinct intramolecular motifs on xylan conformation and on the interaction with cellulose surfaces in Norway spruce (Picea abies). We confirm the presence of motifs with evenly spaced glycosyl decorations on the xylan backbone, together with minor motifs with consecutive glucuronation. These domains are differently enriched in xylan fractions extracted by alkali and subcritical water, which indicates their preferential positioning in the secondary plant cell wall ultrastructure. The flexibility of the 3-fold screw conformation of xylan in solution is enhanced by the presence of arabinofuranosyl decorations. Additionally, molecular dynamic simulations suggest that the glycosyl substitutions in xylan are not only sterically tolerated by the cellulose surfaces but that they increase the affinity for cellulose and favor the stabilization of the 2-fold screw conformation. This effect is more significant for the hydrophobic surface compared with the hydrophilic ones, which demonstrates the importance of nonpolar driving forces on the structural integrity of secondary plant cell walls. These novel molecular insights contribute to an improved understanding of the supramolecular architecture of plant secondary cell walls and have fundamental implications for overcoming lignocellulose recalcitrance and for the design of advanced wood-based materials.
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| 32. |
- Mattsson, Tuve, et al.
(författare)
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The Development of a Wood-based Materials-biorefinery
- 2017
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Ingår i: BioResources. - : North Carolina State University. - 1930-2126. ; 12:4, s. 9152-9182
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Tidskriftsartikel (refereegranskat)abstract
- Several different methods for the extraction, separation, and purification of wood constituents were combined in this work as a unified process with the purpose of achieving a high overall efficiency of material extraction and utilization. This study aimed to present a laboratory-scale demonstrator biorefinery that illustrated how the different wood constituents could be separated from the wood matrix for later use in the production of new bio-based materials and chemicals by combining several approaches. This study builds on several publications and ongoing activities within the Wallenberg Wood Science Center (WWSC) in Sweden on the theme "From wood to material components." Combining the approaches developed in these WWSC projects - including mild steam explosion, membrane and chromatographic separation, enzymatic treatment and leaching, ionic liquid extraction, and fractionation together with Kraft pulping - formed an outline for a complete materials-biorefinery. The process steps involved were tested as integral steps in a linked process. The scale of operations ranged from the kilogram-scale to the gram-scale. The feasibility and efficiency of these process steps in a biorefinery system were assessed, based on the data, beginning with whole wood.
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| 33. |
- Mattsson, Tuve, et al.
(författare)
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Towards a wood based material biorefinery - A demonstrator
- 2015
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Ingår i: 6th Nordic Wood Biorefinery Conference, NWBC 2015. - : VTT Technical Research Centre of Finland. - 9789513883539 ; , s. 92-101
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Konferensbidrag (refereegranskat)abstract
- Wood, the most abundant ligno-cellulosic raw material available, is a key potential feedstock for production of more sustainable alternatives to fossil-based materials. However advances within the fields of extraction and treatment processes within what is often referred to as the biorefinery concept is essential to allow for such transition. In this study, several different methods for the extraction and separation of wood constituents have been combined in a single process with the purpose of achieving a high overall efficiency of material extraction and utilisation. The work builds on several activities within the Wallenberg Wood Science Center (WWSC). The aim is to present a laboratory-scale demonstrator that illustrates how the different constituents can be separated from the wood matrix for later use in the production of bio-based materials and chemicals. The process steps involved have been tested as integral steps in a linked process for a scale of operations that range from the kilogram-scale down to the gram-scale. Industrially chipped softwood, containing mainly spruce with some pine, was used as raw material.
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| 34. |
- Moser, Carl, 1987-, et al.
(författare)
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Improved dispersibility of once-dried cellulose nanofibers in the presence of glycerol
- 2018
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Ingår i: Nordic Pulp & Paper Research Journal. - Berlin : De Gruyter Open. - 0283-2631 .- 2000-0669. ; 33:4, s. 647-650
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Tidskriftsartikel (refereegranskat)abstract
- To investigate the dispersibility of dried cellulose nanofibers (CNFs), various additions (glycerol, octanol, glycol, and sodium perchlorate) were added to CNFs prior to drying. Glycerol was the only species to show any significant effect on re-dispersibility. The sedimentation was slower, and the transmittance of the solution was comparable to that of its undried counterpart. Increasing the amount of glycerol showed a clear trend with regard to dispersibility. The mechanical properties of films were maintained for samples that were dried and redispersed in the presence of glycerol.
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| 35. |
- Moser, Carl, 1987-
(författare)
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Manufacturing and Characterization of Cellulose Nanofibers
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The usage of wood has been a dominant driving force during the evolution of the human species. It allowed us to cook food, build tools, put roofs over our head and explore the world. The fibers making up the tree has been the most important way to store and transmit knowledge in the form of paper for centuries. It may not be considered as the most interesting or hi-tech of fields, although, nothing could be further from the truth. One of society's most significant issue is how to live sustainably, which is coincidentally exactly what trees can solve. We can live in tall buildings made from wood, locking up vast amounts of carbon dioxide - we can replace many of the plastics we use today with sustainable alternative from the components making up the tree - we could even make clothes from our trees and stop being reliant on the untenable cotton production - only our imagination is holding us back from what can be made from trees.Cellulose is the structural component in trees, the molecule arranges itself in a complex hierarchical structure that forms the wood-cells, or fibers. Breaking down this hierarchical structure down to its smallest structural units leaves us with tiny fibers, no longer than a few micrometers and with a width of merely four nanometers. These are cellulose nanofibers, and this work has aimed to understand how and what it takes to liberate these fine fibers from the larger fiber that they make up. Two main pathways exist to liberate the nanofibers, either chemically by introducing negatively charged groups on the surface of the cellulose, making the fibrils repel each other, or mechanically, simply by intense processing of the fibers. However, these processes are associated with certain flaws in that (i) vast amount of energy is required unless the fibers are pretreated, (ii) disintegration is performed in instruments that do not scale well, (iii) disintegration is carried out at a low concentration of fibers, typically below 5%. Additionally, what comes out of a process is difficult to characterize in terms of quality due to an inherent inhomogeneity and the small size of the nanofibers.These issues in combination with a greater understanding of the processes are the foundation of this thesis.Decreased energy consumption and scalability was explored via the steam explosion concept Nanopulp. In order to avoid issues associated with the low concentration, a method was developed for drying cellulose nanofibers to a paste without causing hornification using glycerol. A variety of cellulose nanofibers from different sources were prepared and characterization techniques were compared and expanded upon, including the development of a method for better describing the surface area of cellulose nanofibers. Finally, an environmentally friendly composite was made using cheap and available resources in combination with cellulose nanofibers.
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| 36. |
- Moser, Carl, 1987-, et al.
(författare)
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Specific surface area increase during cellulose nanofiber manufacturing related to energy input
- 2016
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Ingår i: BioResources. - : North Carolina State University. - 1930-2126. ; 11:3, s. 7124-7132
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Tidskriftsartikel (refereegranskat)abstract
- Softwood fibers pretreated with a monocomponent endoglucanase were used to prepare a series of cellulose nanofiber qualities using a microfluidizer and 2 to 34 MWh ton-1 of energy input. The specific surface area was determined for the series using critical point drying and gas adsorption. Although the specific surface area reached a maximum of 430 m2 g-1 at 11 MWh ton-1, the nanofiber yield and transmittance continued to increase beyond this point, indicating that more energy is required to overcome possible friction caused by an interwoven nanofiber network unrelated to the specific surface area. A new method for estimating the surface area was investigated using xyloglucan adsorption in pure water. With this method it was possible to follow the disintegration past the point of maximum specific surface area. The technical significance of these findings is discussed.
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| 37. |
- Moser, Carl, 1987-, et al.
(författare)
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Structural aspects on the manufacturing of cellulose nanofibers from wood pulp fibers
- 2019
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Ingår i: BioResources. - : North Carolina State University. - 1930-2126. ; 14:1, s. 2269-2276
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Tidskriftsartikel (refereegranskat)abstract
- The exact mechanism behind the disintegration of chemical pulp fiber into cellulose nanofibers is poorly understood. In this study, samples were subjected to various homogenization cycles, indicating that the mechanism is a stepwise process. In the earlier stages of the mechanical process, a large amount of macrofibrils were created as the larger structures disappeared. Upon mechanical treatment these macrofibrils disappeared despite the increasing yield of cellulose nanofibers. The proposed model expands the understanding of the disintegration pathway and may provide additional insight as to how wood cells are converted into microfibrils.
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| 38. |
- Moser, Carl, et al.
(författare)
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Toward Industrially Feasible Methods for Following the Process of Manufacturing Cellulose Nanofibers
- 2015
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Ingår i: BioResources. - : BioResources. - 1930-2126. ; 10:2, s. 2360-2375
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Tidskriftsartikel (refereegranskat)abstract
- Nanocellulose is a recently developed form of cellulose that has the potential to be used in many different industries, ranging from food to high-performance applications. This material is commercially manufactured through the homogenization of chemical pulps, but the process is energy-consuming and is still an important subject for development. Simple, robust methods are required for the quality control and optimization of industrial nanocellulose production. In this study, a number of different methods, based on different principles of monitoring the manufacture of cellulose nanofibers were evaluated and compared for five different nanocellulose qualities, both for their resolution and robustness/ease. Methods based on microscopy, light scattering, centrifugation, and viscosity were examined and all appeared useful for observing the manufacturing process during its initial stage. However, only methods based on centrifugation, turbidity, and transmittance yielded reliable data for the entire manufacturing process. Of these methods, transmittance measurement may be the best candidate for routine use because the method is simple, rapid, and only requires spectrophotometer equipment.
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| 39. |
- Moser, Carl, 1987-, et al.
(författare)
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Xyloglucan adsorption for measuring the specific surface area on various never-dried cellulose nanofibers
- 2018
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Ingår i: Nordic Pulp & Paper Research Journal. - Berlin : De Gruyter Open. - 0283-2631 .- 2000-0669. ; 33:2, s. 186-193
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we explore xyloglucan adsorption to cellulose nanofibers as a method for the evaluation of their quality (i. e., the degree of disintegration) and the accessible surface area in the wet state and at low ionic strength. This method was shown to be capable of estimating the surface areas of 14 different cellulose nanofiber qualities from both hardwood and softwood with different pretreatments, including enzymatic hydrolysis using a monocomponent endoglucanase, TEMPO-mediated oxidation, and carboxymethylation. The cellulose surface measured using this method showed a correlation with the degree of disintegration expressed as transmittance for different concentrations of xyloglucan.
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| 40. |
- Moser, Carl, 1987-, et al.
(författare)
-
Xyloglucan for estimating the surface area of cellulose fibers
- 2018
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Ingår i: Nordic Pulp & Paper Research Journal. - Berlin : De Gruyter Open. - 0283-2631 .- 2000-0669. ; 33:2, s. 194-199
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Tidskriftsartikel (refereegranskat)abstract
- The hemicellulose xyloglucan can be utilized to measure exposed cellulose surfaces for pulp fibers. This was shown by correlating a refining series with the adsorbed amount of xyloglucan, and by swelling cellulose fibers to various degrees by increasing the charge density. The method is specific to cellulose and could be used to quantify refining or to determine hornification.
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| 41. |
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| 42. |
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| 43. |
- Paliakaitė, Birutė, et al.
(författare)
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Atrial fibrillation frequency tracking in ambulatory ECG signals : The significance of signal quality assessment
- 2018
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Ingår i: Computers in Biology and Medicine. - : Elsevier BV. - 0010-4825. ; 102, s. 227-233
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Tidskriftsartikel (refereegranskat)abstract
- An approach to atrial fibrillation (AF) frequency tracking in long-term ambulatory ECG recordings is presented, comprising f-wave extraction, dominant atrial frequency (DAF) tracking, and signal quality assessment. Since poor signal quality is commonly encountered in ambulatory monitoring, a recently proposed index is employed to assess f-wave signal quality in a database containing 38 patients with permanent AF. The index ensures that DAF outliers, typically associated with poor-quality segments, are excluded from further analysis. 40% of all 5-s signal segments were excluded from the database due to poor quality. The exclusion of DAF outliers significantly reduces the standard deviation of the frequency estimates (p≤0.01), allowing more reliable evaluation of the difference between day- and night-time DAF. The results show that signal quality assessment plays a central role in DAF tracking, and therefore should be employed in ambulatory monitoring.
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| 44. |
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| 45. |
- Simaityte, Monika, et al.
(författare)
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Quantitative Evaluation of Temporal Episode Patterns in Paroxysmal Atrial Fibrillation
- 2018
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Ingår i: Computing in Cardiology Conference, CinC 2018. - 9781728109589 ; 45
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Konferensbidrag (refereegranskat)abstract
- Flow velocity in left atrial appendage decreases when paroxysmal atrial fibrillation (PAF) progresses to longer episodes, suggesting that the temporal PAF episode pattern may be related to risk of thrombus formation. This study investigates the feasibility of discriminating episode patterns based on two descriptors: the aggregation characterizes the temporal distribution of PAF episodes, whereas the Gini coefficient characterizes differences in episode duration. The descriptors were studied on three PhysioNet databases with annotated PAF episodes, resulting in a total of 102 recordings. Three types of patterns were defined: congregation of several episodes in a single and multiple clusters, and episodes dispersed over the entire monitoring period. The results show that the aggregation descriptor achieves large values for patterns with a single and multiple clusters (0.76± 0.07 and 0.60± 0.08, respectively). In contrast, much lower values are obtained for dispersed episode patterns (0.10± 0.05). The Gini coefficient is better suited for discriminating among the patterns with high PAF burden and, therefore, represents a descriptor which is complementary to aggregation. Both descriptors may have relevance when studying the relationship between episode pattern and the risk of thrombus formation.
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| 46. |
- Säll, Johanna, et al.
(författare)
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Salt-inducible kinase 2 and -3 are downregulated in adipose tissue from obese or insulin-resistant individuals : implications for insulin signalling and glucose uptake in human adipocytes
- 2017
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Ingår i: Diabetologia. - : Springer Science and Business Media LLC. - 1432-0428 .- 0012-186X. ; 60:2, s. 314-323
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Tidskriftsartikel (refereegranskat)abstract
- AIMS/HYPOTHESIS: Salt-inducible kinases (SIKs) are related to the metabolic regulator AMP-activated protein kinase (AMPK). SIK2 is abundant in adipose tissue. The aims of this study were to investigate the expression of SIKs in relation to human obesity and insulin resistance, and to evaluate whether changes in the expression of SIKs might play a causal role in the development of disturbed glucose uptake in human adipocytes.METHODS: SIK mRNA and protein was determined in human adipose tissue or adipocytes, and correlated to clinical variables. SIK2 and SIK3 expression and phosphorylation were analysed in adipocytes treated with TNF-α. Glucose uptake, GLUT protein levels and localisation, phosphorylation of protein kinase B (PKB/Akt) and the SIK substrate histone deacetylase 4 (HDAC4) were analysed after the SIKs had been silenced using small interfering RNA (siRNA) or inhibited using a pan-SIK-inhibitor (HG-9-91-01).RESULTS: We demonstrate that SIK2 and SIK3 mRNA are downregulated in adipose tissue from obese individuals and that the expression is regulated by weight change. SIK2 is also negatively associated with in vivo insulin resistance (HOMA-IR), independently of BMI and age. Moreover, SIK2 protein levels and specific kinase activity display a negative correlation to BMI in human adipocytes. Furthermore, SIK2 and SIK3 are downregulated by TNF-α in adipocytes. Silencing or inhibiting SIK1-3 in adipocytes results in reduced phosphorylation of HDAC4 and PKB/Akt, less GLUT4 at the plasma membrane, and lower basal and insulin-stimulated glucose uptake in adipocytes.CONCLUSION/INTERPRETATION: This is the first study to describe the expression and function of SIKs in human adipocytes. Our data suggest that SIKs might be protective in the development of obesity-induced insulin resistance, with implications for future treatment strategies.
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| 47. |
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| 48. |
- Wang, Yan, et al.
(författare)
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Stabilisation of polysaccharides during alkaline pretreatment of wood combined with enzyme-supported extractions in a biorefinery
- 2015
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Ingår i: Journal of wood chemistry and technology. - : Informa UK Limited. - 0277-3813 .- 1532-2319. ; 35:2, s. 91-101
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Tidskriftsartikel (refereegranskat)abstract
- Specific enzymes have been demonstrated to increase the possibilities for extracting wood polymers. Enzymatic treatment requires an open wood structure, which was achieved by extended impregnation of the wood. However, some of the hemicelluloses, primarily glucomannan, and lignin were lost during the impregnation. To improve the carbohydrate yield, three glucomannan modification agents: sodium borohydride, polysulphide and anthraquinone, were used, which increased the yields of the impregnated materials from 76.6% to 89.6%, 81.3% and 80.0%, respectively. Through the use of additives, most of the glucomannan could be retained in the wood while still allowing the enzymes to penetrate the wood and attack the polymers. The additives also increased the extraction yield from 9 to 12% w/w wood. Gamanase treatment prior to the extraction increased the extraction yield to 14%. Of the three stabilising agents, sodium borohydride was the most efficient, providing the highest extraction yields.
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| 49. |
- Zhao, Yadong, et al.
(författare)
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Cellulose Nanofibers from Softwood, Hardwood, and Tunicate : Preparation-Structure-Film Performance Interrelation
- 2017
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 9:15, s. 13508-13519
-
Tidskriftsartikel (refereegranskat)abstract
- This work reveals the structural variations of cellulose nanofibers (CNF) prepared from different cellulose sources, including softwood (Picea abies), hardwood (Eucalyptus grandis × E. urophylla), and tunicate (Ciona intestinalis), using different preparation processes and their correlations to the formation and performance of the films prepared from the CNF. Here, the CNF are prepared from wood chemical pulps and tunicate isolated cellulose by an identical homogenization treatment subsequent to either an enzymatic hydrolysis or a 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-mediated oxidation. They show a large structural diversity in terms of chemical, morphological, and crystalline structure. Among others, the tunicate CNF consist of purer cellulose and have a degree of polymerization higher than that of wood CNF. Introduction of surface charges via the TEMPO-mediated oxidation is found to have significant impacts on the structure, morphology, optical, mechanical, thermal, and hydrophobic properties of the prepared films. For example, the film density is closely related to the charge density of the used CNF, and the tensile stress of the films is correlated to the crystallinity index of the CNF. In turn, the CNF structure is determined by the cellulose sources and the preparation processes. This study provides useful information and knowledge for understanding the importance of the raw material for the quality of CNF for various types of applications.
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| 50. |
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