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| 2. |
- Frodeson, Stefan, Universitetsadjunkt, 1968-, et al.
(författare)
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Compression of Biomass Substances-A Study on Springback Effects and Color Formation in Pellet Manufacture
- 2019
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Ingår i: Applied Sciences. - : MDPI. - 2076-3417. ; 9:20
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Tidskriftsartikel (refereegranskat)abstract
- In order to increase the use of a variated raw material base for pellet production with a maintained density level, knowledge of the biomaterials' ability to counteract any springback effects is essential. In this study, the springback effects were investigated for single press produced pellets from cellulose, hemicelluloses, pectin, and two woods at different moisture contents. The change in pellet coloring was also tested through a spectrophotometer for both xylan and carboxymethyl cellulose (CMC) pellets. The results show that the density of xylan pellets is much higher than glucomannan, for both green and cured pellets, and that the length of the pellets, as well as springback contribution, differ between the hemicelluloses. The study also presents results showing that both xylan and CMC pellets have a mutually identical spectrum and that the changes in the structure of xylan are not only related to moisture content, but are also pressure-related. The study also postulates that the color difference of the xylan pellets is a result of physical changes in the structure, as opposed to being of a chemical nature.
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| 3. |
- Giummarella, Nicola, et al.
(författare)
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Fractional profiling of kraft lignin structure : Unravelling insights on lignin reaction mechanisms
- 2019
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485.
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Tidskriftsartikel (refereegranskat)abstract
- The kraft process is the main process used for the production of chemical pulps. In this process, an efficient delignification is achieved, yielding bleachable grade pulps. In recent years, there has been interest in valorization of the dissolved lignins, prompted by the development of technically feasible processes to retrieve it from the black liquor. However, the structural-, functional-, and size-related heterogeneities of lignin present both analytical challenges and challenges in developing new applications. Hence, refining of the crude product is essential. Herein, advanced NMR characterization (13C NMR, APT/DEPT NMR, 31P NMR, HSQC, HMBC, HSQC-TOCSY) was applied to profile the detailed molecular structures of refined kraft lignins and unravel mechanistic insights on important lignin reactions during kraft pulping. From this structural analysis of the lignins, a model oligomer was synthesized and analyzed to provide support to the effect that a retro-aldol reaction in combination with radical recombination reactions play a significant role in the formation of the reconstituted fraction of kraft lignin. In this regard, a new type of linkage accounting for approximately 10% of the interunits in kraft lignin is reported.
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| 4. |
- Karlsson, Maria, et al.
(författare)
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Toward a Consolidated Lignin Biorefinery : Preserving the Lignin Structure through Additive-Free Protection Strategies.
- 2020
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Ingår i: ChemSusChem. - : Wiley. - 1864-5631 .- 1864-564X. ; 13:17, s. 4666-4677
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Tidskriftsartikel (refereegranskat)abstract
- As part of the continuing efforts in lignin-first biorefinery concepts, this study concerns a consolidated green processing approach to obtain high yields of hemicelluloses and lignin with a close to native molecular structure, leaving a fiber fraction enriched in crystalline cellulose. This is done by subcritical water extraction of hemicelluloses followed by organosolv lignin extraction. This initial report focuses on a detailed characterization of the lignin component, with the aim of unravelling processing strategies for the preservation of the native linkages while still obtaining good yields and high purity. To this effect, a static cycle process is developed as a physical protection strategy for lignin, and advanced NMR analysis is applied to study structural changes in lignin. Chemical protection mechanisms in the cyclic method are also reported and contrasted with the mechanisms in a reference batch extraction process where the role of homolytic cleavage in subsequent repolymerization reactions is elucidated.
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| 5. |
- Lindén, Louise, et al.
(författare)
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Ultrasonography- and doppler-guided surgical treatment for insertional Achilles tendinopathy : results from a case series in a Southern Sweden county hospital
- 2023
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Ingår i: Foot and Ankle Orthopaedics. - : Sage Publications. - 2473-0114. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: Treatment with ultrasonography (US)- and color Doppler (CD)-guided mini surgery for insertional Achilles tendinopathy has shown good clinical results in a sports medicine setting. The aim in this study was to introduce this new methodology at a county hospital and study the clinical results on a traditional orthopaedic population.Methods: Twenty-six consecutive patients (12 men, mean age 61 years; 14 women, mean age 56 years) with a long duration (>12 months) of pain symptoms from insertional Achilles tendinopathy (a combination of bursae, bone, and tendon pathology) were included. US- and CD-guided surgical removal of bursae, bone, and tendon pathology, performed with local anaesthesia, was used. After surgery, there was immediate weightbearing loading without immobilization, followed by a structured rehabilitation protocol for 12 weeks. The VISA-A and SEFAS scores plus a questionnaire evaluating satisfaction with treatment and activity level was used for evaluation.Results: At the 1-year follow-up, there were 3 dropouts. Twenty-one patients were satisfied. Their VISA-A score had increased significantly from 26 to 81 (P <.001), and the SEFAS score from 17 to 38 (P <.001). Two patients were not satisfied. There were 3 complications, 2 superficial skin infections, and 1 wound rupture.Conclusion: For patients with chronic painful insertional Achilles tendinopathy, the US- and CD-guided surgical treatment method followed by immediate weightbearing loading showed a high satisfaction rate and improved functional scores at the 1-year follow-up in a majority of the patients. There are advantages using this method compared to other more tendon invasive surgical methods in use for this condition.Level of Evidence: Level IV, case series.
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| 6. |
- Lindén, Pär A., et al.
(författare)
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Adapting the kraft cooking process in glycerol media. Studies of impregnation kinetics
- 2023
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Ingår i: Nordic Pulp & Paper Research Journal. - : De Gruyter Open Ltd. - 0283-2631 .- 2000-0669. ; 38:1, s. 9-18
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Tidskriftsartikel (refereegranskat)abstract
- Although organosolv processes using high-boiling solvents have been investigated in recent decades for developing novel industrial processes, there are potential benefits of using high-boiling point solvents for traditional sulphate-based cooking processes, both from an industrial perspective and from a laboratory perspective. Using high-boiling solvents, experiments can be done under atmospheric conditions, thus making it easier to continually monitor laboratory experiments and extracting aliquots at desired intervals. Using such a system, alkaline consumption was monitored during impregnation of spruce chips in glycerol media using chemical charges of 1 M NaOH and 0.1 M NaHS, i. e., kraft pulping conditions, and compared to a similar investigation of alkaline consumption in water media using steel autoclaves. The resulting data was fitted to a first order kinetic model, with an apparent activation energy of 22 kJ mol-1 in glycerol media. Finally, a "normal quality pulp"of kappa number 28 and a viscosity of 1113 ml g-1 was successful produced using a cooking process with an impregnation step at 140 °C for 3 h and a cooking step at 160 °C for 4 h. A nuclear magnetic resonance study on the dissolved lignin produced for said experiment showed characteristics typical of other kraft lignins.
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| 7. |
- Lindén, Pär A., et al.
(författare)
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Stabilising mannose using sodium dithionite at alkaline conditions
- 2020
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Ingår i: Holzforschung. - : Walter de Gruyter. - 0018-3830 .- 1437-434X. ; 74:2, s. 131-140
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Tidskriftsartikel (refereegranskat)abstract
- The kraft process remains the dominant-chemical pulping process but still struggles with extensive hemicellulose degradation. Such degradation has previously been mitigated through the use of anthraquinone; but due to it recently being found to have carcinogenic properties, anthraquinone is now being phased out. One alternative, sodium dithionite, was initially investigated in the 1950s but was found to be unviable. The present study investigated whether sodium dithionite could be made viable through the use of different processing parameters, using mannose as a model compound and measuring the yield of mannitol in the various systems using gas chromatography with flame ionization detection (GC-FID) and nuclear magnetic resonance (NMR). Alkalinity was found to be crucial; at pH 14 as well as pH 7, dithionite indeed proved unviable, but if pH was kept at either 8 or 10 significant reduction was seen to occur. The best results were obtained at pH 10 when a lower temperature (70 degrees C) was used to compensate for alkaline degradation of the mannose reactant.
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| 8. |
- Nilsson, Emma, 1982, et al.
(författare)
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On-to-off-path gaze shift cancellations lead to gaze concentration in cognitively loaded car drivers: A simulator study exploring gaze patterns in relation to a cognitive task and the traffic environment
- 2020
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Ingår i: Transportation Research Part F: Traffic Psychology and Behaviour. - : Elsevier BV. - 1369-8478. ; 75, s. 1-15
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Tidskriftsartikel (refereegranskat)abstract
- Appropriate visual behaviour is necessary for safe driving. Many previous studies have found that when performing non-visual cognitive tasks, drivers typically display an increased amount of on-path glances, along with a deteriorated visual scanning pattern towards potential hazards at locations outside their future travel path (off-path locations). This is often referred to as a gaze concentration effect. However, what has not been explored is more precisely how and when gaze concentration arises in relation to the cognitive task, and to what extent the timing of glances towards traffic-situation relevant off-path locations is affected. To investigate these specific topics, a driving simulator study was carried out. Car drivers’ visual behaviour during execution of a cognitive task (n-back) was studied during two traffic scenarios; one when driving through an intersection and one when passing a hidden exit. Aside from the expected gaze concentration effect, several novel findings that may explain this effect were observed. It was found that gaze shifts from an on-path to an off-path location were inhibited during increased cognitive load. However, gaze shifts in the other direction, that is, from an off-path to an on-path location, remained unaffected. This resulted in on-path glances increasing in duration, while off-path glances decreased in number. Furthermore, the inhibited off-path glances were typically not compensated for later. That is, off-path glances were cancelled, not delayed. This was the case both in relation to the cognitive task (near-term) and the traffic environment (far-term). There was thus a general reduction in the number of glances towards situationally relevant off-path locations, but the timing of the remaining glances was unaffected. These findings provide a deeper understanding of the mechanism behind gaze concentration and can contribute to both understanding and prediction of safety relevant effects of cognitive load in car drivers.
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| 9. |
- Nordin, Pär, et al.
(författare)
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Choice of anesthesia and risk of reooperation for recurrence in groin hernia repair
- 2004
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Ingår i: Annals of Surgery. - : Ovid Technologies (Wolters Kluwer Health). - 0003-4932 .- 1528-1140. ; 240:1, s. 187-192
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To analyze the relative risk of reoperation for recurrence using 3 anesthetic alternatives, general anesthesia (GA), regional (spinal-, epidural-) anesthesia (RA), and local anesthesia (LA), and to study time trends for various anesthetic and operative methods, as well as other risk factors regarding reoperation for recurrence.Background: The method of anesthesia used for hernia repair is generally assumed not to affect the long-term outcome. The few studies on the topic have rendered conflicting results.Methods: Data from the Swedish Hernia Register was used. Relative risk was first estimated using univariate analysis for assumed risk variables and then selecting variables with the highest or lowest univariate risk for multivariate analysis.Results: From 1992 through 2001, 59,823 hernia repairs were recorded. Despite the fact that univariate analysis showed a somewhat lower risk for reoperation in the LA group, the multivariate analysis showed that LA was associated with a significantly increased risk for reoperation in primary but not in recurrent hernia repair. The Lichtenstein technique carried a significantly lower reoperation risk than any other method of operation.Conclusions: LA was associated with a higher risk of reoperation for recurrence after primary hernia repair. The use of mesh techniques has increased considerably, and among these the Lichtenstein repair was associated with a significantly lower risk for reoperation than any other repair.
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