| 1. |
- Idström, Alexander, et al.
(författare)
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Dissolution of cellulose in tetrabutylammonium acetate/dimethyl sulfoxide
- 2016
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Ingår i: The 7th workshop on cellulose, regenerated cellulose and cellulose derivatives.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The dissolution of cellulose in tetrabutylammonium acetate (TBAAc)/dimethyl sulfoxide (DMSO) was studied combining experimental and simulation techniques. It was found that the dissolution limit at 40 °C corresponded to a molar ratio close to one acetate per cellulose anhydroglucose units. MD simulations suggested that the acetate ions bind to cellulose by dual hydrogen bonds. This effectively turns cellulose into a polyelectrolyte, attracting the bulky tetrabutylammonium (TBA+) counter ions, which prevent close contact between chains in the dissolved state. This hypothesis was tested by 1H- and 13C-NMR spectroscopy, which confirmed that acetate forms hydrogen bonds to cellulose, and by diffusion NMR spectroscopy, which demonstrated a strong dynamic correlation between bound acetate and tetrabutylammonium in near-quantitative agreement with simulation. The present results suggest that offering hydrogen bonding to the acetate ions is the main driving force for dissolving cellulose and that the TBA+ counter ions form a diffuse layer around the acetate-decorated cellulose chains.
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| 2. |
- Idström, Alexander, et al.
(författare)
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On the dissolution of cellulose in tetrabutylammonium acetate/dimethyl sulfoxide : a frustrated solvent
- 2017
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Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 24:9, s. 3645-3657
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Tidskriftsartikel (refereegranskat)abstract
- We have found that the dissolution of cellulose in the binary mixed solvent tetrabutylammonium acetate/dimethyl sulfoxide follows a previously overlooked near-stoichiometric relationship such that one dissolved acetate ion is able to dissolve an amount of cellulose corresponding to about one glucose residue. The structure and dynamics of the resulting cellulose solutions were investigated using small-angle X-ray scattering (SAXS) and nuclear magnetic resonance techniques as well as molecular dynamics simulation. This yielded a detailed picture of the dissolution mechanism in which acetate ions form hydrogen bonds to cellulose and causes a diffuse solvation sheath of bulky tetrabutylammonium counterions to form. In turn, this leads to a steric repulsion that helps to keep the cellulose chains apart. Structural similarities to previously investigated cellulose solutions in aqueous tetrabutylammonium hydroxide were revealed by SAXS measurement. To what extent this corresponds to similarities in dissolution mechanism is discussed.
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| 6. |
- Berntsson Svensson, Richard, et al.
(författare)
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An investigation of how quality requirements are specified in industrial practice
- 2013
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Ingår i: Information and Software Technology. - : Elsevier BV. - 0950-5849 .- 1873-6025. ; 55:7, s. 1224-1236
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Tidskriftsartikel (refereegranskat)abstract
- Context: This paper analyses a sub-contractor specification in the mobile handset domain. Objective: The objective is to understand how quality requirements are specified and which types of requirements exist in a requirements specification from industry. Method: The case study is performed in the mobile handset domain, where a requirements specification was analyzed by categorizing and characterizing the pertaining requirements. Results: The requirements specification is written in structured natural language with unique identifiers for the requirements. Of the 2178 requirements, 827 (38%) are quality requirements. Of the quality requirements, 56% are quantified, i.e., having a direct metric in the requirement. The variation across the different sub-domains within the requirements specification is large. Conclusion: The findings from this study suggest that methods for quality requirements need to encompass many aspects to comprehensively support working with quality requirements. Solely focusing on, for example, quantification of quality requirements might overlook important requirements since there are many quality requirements in the studied specification where quantification is not appropriate. (C) 2013 Elsevier B.V. All rights reserved.
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| 7. |
- Bjurhager, Ingela, et al.
(författare)
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Ultrastructure and Mechanical Properties of Populus Wood with Reduced Lignin Content Caused by Transgenic Down-Regulation of Cinnamate 4-Hydroxylase
- 2010
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 11:9, s. 2359-2365
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Tidskriftsartikel (refereegranskat)abstract
- Several key enzymes in lignin biosynthesis of Populus have been down-regulated by transgenie approaches to investigate their role in wood lignification and to explore their potential for lignin modification. Cinnamate 4-hydroxylase is an enzyme in the early phenylpropanoid pathway that has not yet been functionally analyzed in Populus. This study shows that down-regulation of cinnamate 4-hydroxylase reduced Klason lignin content by 30% with no significant change in syringyl to guaiacyl ratio. The lignin reduction resulted in ultrastructural differences of the wood and a 10% decrease in wood density. Mechanical properties investigated by tensile tests and dynamic mechanical analysis showed a decrease in stiffness, which could be explained by the lower density. The study demonstrates that a large modification in lignin content only has minor influences on tensile properties of wood in its axial direction and highlights the usefulness of wood modified beyond its natural variation by transgene technology in exploring the impact of wood biopolymer composition and ultrastructure on its material properties.
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| 8. |
- Gambäck, Björn, et al.
(författare)
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Active Learning for Dialogue Act Classification
- 2011. - 9
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Konferensbidrag (refereegranskat)abstract
- Active learning techniques were employed for classification of dialogue acts over two dialogue corpora, the English human-human Switchboard corpus and the Spanish human-machine Dihana corpus. It is shown clearly that active learning improves on a baseline obtained through a passive learning approach to tagging the same data sets. An error reduction of 7% was obtained on Switchboard, while a factor 5 reduction in the amount of labeled data needed for classification was achieved on Dihana. The passive Support Vector Machine learner used as baseline in itself significantly improves the state of the art in dialogue act classification on both corpora. On Switchboard it gives a 31% error reduction compared to the previously best reported result.
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| 9. |
- Gambäck, Björn, et al.
(författare)
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Experiences of Language Engineering Algorithm Reuse
- 2000. - 1
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Konferensbidrag (refereegranskat)abstract
- Abstract Traditionally, the level of reusability of language processing resources within the research community has been very low. Most of the recycling of linguistic resources has been concerned with reuse of data, e.g., corpora, lexica, and grammars, while the algorithmic resources far too seldom have been shared between dierent projects and institutions. As a consequence, researchers who are willing to reuse somebody else's processing components have been forced to invest major eorts into issues of integration, inter-process communication, and interface design. In this paper, we discuss the experiences drawn from the svensk project regarding the issues on reusability of language engineering software as well as some of the challenges for the research community which are prompted by them. Their main characteristics can be laid out along three dimensions; technical/software challenges, linguistic challenges, and `political' challenges. In the end, the unavoidable conclusion is that it denitely is time to bring more aspects of engineering into the Computational Linguistic community!
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| 10. |
- Gambäck, Björn, et al.
(författare)
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Methods for Amharic part-of-speech tagging
- 2009. - 1
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Ingår i: Proceedings of the 12th Conference of the European Chapter of the Association for Computational Linguistics.
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Konferensbidrag (refereegranskat)abstract
- The paper describes a set of experiments involving the application of three state-of- the-art part-of-speech taggers to Ethiopian Amharic, using three different tagsets. The taggers showed worse performance than previously reported results for Eng- lish, in particular having problems with unknown words. The best results were obtained using a Maximum Entropy ap- proach, while HMM-based and SVM- based taggers got comparable results.
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