| 1. |
- Berg, Jan-Erik, 1957-, et al.
(författare)
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Refining gentleness - a key to bulky CTMP
- 2022
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Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 37:2, s. 349-355
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Tidskriftsartikel (refereegranskat)abstract
- Chemithermomechanical pulp (CTMP) is often used in middle layers of multiply paperboards due to its high bulk at specified strength. Such a CTMP should consist of well-separated undamaged fibres with sufficient bonding capacity. The basic objective of this work is to examine the effect of refining on bulk, taking into account conditions such as temperature, sulphonation, refining gap and refiner size. First stage CTMP made from Norway spruce (Picea abies) were produced in pilot and mill scale trials. Two new parameters, Equivalent temperature related to softness and Refining gentleness are introduced that take into account refining conditions as actual temperature, softening temperature, bound sulphonate content, refining gap and refiner diameter. The results show that bulk increases linearly with refining gentleness.
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| 2. |
- Kehoe, Laura, et al.
(författare)
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Make EU trade with Brazil sustainable
- 2019
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 364:6438, s. 341-
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 3. |
- Alimohammadzadeh, Rana, et al.
(författare)
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Improving the mechanical properties of CTMP fibers by combining synergistic organocatalytic/polyelectrolyte complex surface engineering with sulfite pretreatment
- 2022
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Ingår i: Proceedings of the International Mechanical Pulping Conference. ; , s. 149-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Fabrication of paper-based packaging materials is increasing and the challenge is developing a sustainable process to manufacture the materials that can compete with plastics. Employing stronger fiber in production of fiber-based materials improves the efficiency of fabrication process by using a reduced amount of biomass. Cationic starch is a well-known polysaccharide that has been introduced to paper and paperboard fibers to improve the mechanical properties of lignocellulosic fibers. The polyelectrolyte (PE) multilayer method has been popularized as a new and interesting technique to enhance the adsorption of cationic starch on the fiber for improving the strength properties of chemi-thermomechanical pulp (CTMP), chemical and kraft pulps. We have shown in our previous work that the synergistic combination of organocatalysis and PE complexes improved the mechanical properties of CTMP and TMP. In this work, we chose to expand this concept by integrating it with low-dose sulfite pretreatment of wood chips in preparation of CTMP. Thus, CTMP produced by initial sulfite pre-treatment was next surface engineered by synergistic combination of organocatalysis and PE complexes using organic acids as catalysts. The CTMP pulps, which contains 0.1-0.24 wt.% sulfur, produced by our novel pulp-engineering strategy shows a dramatic strength increase (Z- strength: up to 100 %) as compared to no surface engineering. While only sulfite pre-treatment and PE-complex surface engineering were able to improve the strength properties, it was only when the organic catalysts was present that the highest strength improvements were reached. Thus, a clear synergistic effect of the catalyst was observed.
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| 4. |
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| 5. |
- Augustsson, Nils-Petter, 1972-, et al.
(författare)
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The character of a VR -visualization
- 2003
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Ingår i: Proceedings of the 26th International Systems Research in Scandinavia (IRIS)Conference.
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Konferensbidrag (refereegranskat)abstract
- When we humans are dealing with complex things in our daily lives, for example an artifact, we tend to ascribe different characters to it. This is our way of getting a quick overview of the artifact and makes it understandable to us. The ascribing of character is not based on thorough examination of the object at hand though, but rather on a certain thing, i.e. a characteristic that catches our attention. This characteristic gives us a certain feeling about the artifact and makes it possible for us to make a judgment about it, even if it is a snap one. With this as a starting point we try to identify the different characteristics, which constitute the overall character, i.e. realism. In many visualisations with this objective, realism is juxtaposed with copying static structures, i.e. buildings and streets. This is also a strong contributor to the realism character in the Botnia-track visualisation. In our opinion this is not enough to get a realistic character. We have identified a few other prominent characteristics that also are important contributors to the realism character, for example landmarks, sound, moving objects and narrator voice. Our main conclusion is that if a realistic character is desirable, more than visualisation of static structures is necessary. We found at least five additional characteristics that influence people’s perception of a virtualisation; landmarks, sound, moving objects and narrator voice. In our opinion, all of these are important for a realistic character to emerge and something that designers have to take in to consideration to reach the intended goal.
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| 6. |
- Berntsson, Thore, 1947, et al.
(författare)
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Towards Sustainabel Oil Refinery - Pre-study for larger co-operation project
- 2008
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In this report, the Chalmers EnergiCentrum (CEC) presents the results of a pre-study commissioned by Preem relating to the effective production of future vehicle fuels.This pre-study was made up of three studies focusing on energy streamlining, the utilisation of waste heat and carbon-dioxide separation and biorefinement relating to the gasification and hydration of vegetable oils. One of the common starting points for these studies was the current situation at the Preem refineries in Göteborg and Lysekil from where the measurement data were obtained and analysed. The report summarises the knowledge situation based on current research in the individual technical fields. The results present some interesting future opportunities for developing the sustainable production of future vehicle fuels. The sections vary, as the areas that have been examined differ and the sections have been written by different people. The reports ends with some joint conclusions and a number of questions which could be included and answered in a more extensive future main study, as part of a developed research partnership between Preem and the Chalmers University of Technology. The preliminary results of this work were analysed with the client at workshops on 1 October and 29 November 2007. The report is written in English combined with an extensive summary in Swedish including a proposal on a future main study. The study was conducted by the Chalmers EnergiCentrum (CEC), in collaboration with a number of researchers in the CEC’s network. They included Thore Berntsson, Jessica Algehed, Erik Hektor and Lennart Persson Elmeroth, all from Heat and Power Technology, Börje Gevert, Chemical and Biological Engineering, Tobias Richards, Forest Products and Chemical Engineering, Filip Johnsson and Anders Lyngfelt, Energy Technology, and Per-Åke Franck and Anders Åsblad, CIT Industriell Energianalys AB. The client, Preem, was represented by Bengt Ahlén, Sören Eriksson, Johan Jervehed, Bertil Karlsson, Gunnar Olsson, Ulf Kuylenstierna, Stefan Nyström, Martin Sjöberg and Thomas Ögren. Tobias Richards was responsible for compiling the report and Bertil Pettersson was the project manager.
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| 7. |
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| 8. |
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| 9. |
- Carlsson, Per-Anders, 1972, et al.
(författare)
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Periodic control for improved low-temperature catalytic activity
- 2001
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Ingår i: Topics in Catalysis. - 1572-9028 .- 1022-5528. ; 16-17:1-4, s. 343-347
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Tidskriftsartikel (refereegranskat)abstract
- The influence of transient changes in the gas composition on the low-temperature activity of a commercial three-way catalyst and a Pt/Al2O3 model catalyst has been studied. By introducing well-controlled periodic O2 pulses to simple gas mixtures of CO or C3H6 (in N2), a substantial improvement of the low temperature oxidation activity was observed for both catalysts. The reason for low activity at low temperatures is normally attributed to self-poisoning by CO or hydrocarbons. The improved catalytic performance observed here is suggested to origin from the transients causing a surface reactant composition that is favourable for the reaction rate.
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| 10. |
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| 11. |
- Carlsson, Per-Anders, 1972, et al.
(författare)
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Periodic control for low-temperature ignition
- 2000
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Ingår i: Proceedings of the 5th International Congress on Catalysis and Automotive Pollution Control (CAPoC5), Brussels, Belgium, April 12-14.
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Konferensbidrag (refereegranskat)
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| 12. |
- Cornelius Chukwu, Eugenia, et al.
(författare)
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Engineered Aldolases Catalyzing Stereoselective Aldol Reactions Between Aryl-Substituted Ketones and Aldehydes
- 2023
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Ingår i: Catalysis Science & Technology. - : Royal Society of Chemistry. - 2044-4753 .- 2044-4761.
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Tidskriftsartikel (refereegranskat)abstract
- An A129G/R134V/S166G triple mutant of fructose 6-phosphate aldolase (FSA) from Escherichia coli was further engineered with the goal to generate new enzyme variants capable of catalyzing aldol reactions between aryl substituted ketones and aldehydes. Residues L107 and L163 were subjected to saturation mutagenesis and the resulting library of FSA variants was screened for catalytic activity with 2-hydroxyacetophenone and phenylacetaldehyde as substrates. A selection of aldolase variants was identified that catalyze the synthesis of 2,3-dihydroxy-1,4-diphenylbutanone. The most active enzyme variants contained an L163C substitution. An L107C/L163C variant was further tested for activity with substituted phenylacetaldehydes, and was shown to afford the production of the corresponding diphenyl substituted butanones with good diastereoselectivities (anti : syn dr of 10 to 30) and reasonable to good enantioselectivities of syn enantiomers (er of 5 to 25).
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| 13. |
- Gustafsson, Erik, 1993-, et al.
(författare)
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Comparison of Design Automation and Machine Learning algorithms for creation of easily modifiable splines
- 2020
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Ingår i: Proceedings of NordDesign 2020, Lyngby, Denmark, 12th - 14th August 2020. - : The Design Society. - 9781912254088
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Konferensbidrag (refereegranskat)abstract
- In order to enable easy modification of results from a design optimization process in a CAD tool, a flexible representation of the geometry is needed. This is not always trivial however, since many file formats are not importable as modifiable geometry into the CAD tool, and if they are, they might not represent the geometry in a way that enables easy modification. To mitigate this problem a design automation (DA) and a machine learning (ML) approach are developed and compared using a test case from an optimization process used to optimize hose routing in tight spaces. In the test case used, the geometry from the optimization process consists of center curves represented as a large number of points. To enable easy modification a more flexible representation is needed such as a spline with a few well-placed control points. Both the DA and ML approach can approximate center curves from the optimization process as splines containing a varying number of control points but do show different properties. The DA approach is considerably slower than the ML but adds a lot of flexibility regarding accuracy and the number of control points used.
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| 14. |
- Gustafsson, Erik, 1993-
(författare)
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Exploring Data-Driven Methods to Enhance Usability of Design Optimization
- 2022
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Developing high-performing products at a low cost while keeping development time down is increasingly important in today’s competitive market. The current state presents a need for efficient product development processes. One of the challenges is knowledge often being limited in early stages where the cost of making changes is still relatively low. As the process progresses more knowledge is gained to better support decisions; however the cost of making changes increases, limiting the design freedom. To increase knowledge while retaining design freedom, several computer-based tools are available to both generate and evaluate designs in order to make iterations faster and more accurate.Design Optimization (DO) can be utilized to explore the design space and find optimal designs. A Computer-Aided Design (CAD) model is often required as input to analysis tools evaluating the designs. By utilizing Design Automation (DA) several tasks involved in creation and modification of CAD models can be automated. For this reason, DA is sometimes considered an enabler for DO although its use is far wider, covering several aspects of the design process mainly focusing on automating repetitive and routine tasks.Machine Learning and other data-driven methods are becoming increasingly viable in the context of DO and DA. This thesis explores the use of data-driven methods to enhance the usability of DO in different ways such as a faster process, new use-cases, or a more integrated and automated process. Literature in the area is reviewed, identifying applications, trends and challenges. Furthermore, two support tools are developed, incorporating data-driven methods tied to an industrial case. The applications focus on parameterizing geometry and predicting design performance respectively. Potential benefits, limitations, and challenges are discussed based on the literature review and insights from the two support tools. The focus of the thesis is mainly on how data-driven methods can facilitate automation and integration in the design process, specifically for complex products requiring significant engineering efforts.
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| 15. |
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| 16. |
- Joelsson, Tove, et al.
(författare)
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The impact of sulfonation and hot-pressing of low-energy high temperature chemi-thermomecanical pulp
- 2022
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Ingår i: Holzforschung. - : Walter de Gruyter. - 0018-3830 .- 1437-434X. ; 76:5, s. 463-472
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Tidskriftsartikel (refereegranskat)abstract
- Hot-pressing high yield pulp-based paper, well above softening temperature of lignin, increases paper density and paper strength. It has been investigated whether improved paper strength can be achieved and if lower pressing temperatures can be used in combination with increased sulfonation of HTCTMP (high temperature chemi-thermomechanical pulp).Moist paper sheets from low-energy Norway Spruce HTCTMP were hot-pressed up to 270°C. Sulfite charges from 25 to 120 kg/bdt were used during impregnation, preheating, and refining at 180°C with an electric energy demand of 370–500 kWh/bdt to a shive content of 1%. The pulps were mixed with 20% bleached unrefined kraft pulp to ensure that the sheet formation would not be hampered by the coarseness of the pulps. A tensile index of 70 kNm/kg was reached with highest sulfite dosage at only 150°C in pressing temperature which can be compared to 60 kNm/kg for the corresponding market CTMP. To obtain high wet strength, the highest temperature was required, while the sulfite charge was found to be of minor importance. This study has shown that it is possible to obtain strong and wet-stable paper products from HTCTMP, having a yield of 94-96% and a low energy demand at reduced pressing temperature.
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| 17. |
- Langenskiöld, Marcus, 1972, et al.
(författare)
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Deep Femoral Vein Reconstruction for Abdominal Aortic Graft Infections is Associated with Low Aneurysm Related Mortality and a High Rate of Permanent Discontinuation of Antimicrobial Treatment
- 2021
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Ingår i: European Journal of Vascular and Endovascular Surgery. - : Elsevier. - 1078-5884 .- 1532-2165. ; 62:6, s. 927-934
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Aortic prosthesis infection is a devastating complication of aortic surgery. In situ reconstruction with the neo-aorto-iliac system (NAIS) bypass technique has become increasingly used and is recommended in recent treatment guidelines. The main aim was to evaluate NAIS procedural outcomes when undertaken after previous open or endovascular aortic repair in Sweden.Methods: In this retrospective study, The National Quality Registry for Vascular Surgery (Swedvasc) was used to identify Swedish centres that offered the NAIS bypass procedure for aortic prosthesis infection between 2008 and 2018. Variables of special interest were procedural details, short and long term survival, renal and other complications, and the durtion of antimicrobial treatment.Results: Forty patients (36 males, four females [mean age 69 years], 32 open repairs, seven endovascular aortic repairs [EVAR] and one fenestrated EVAR; 21 presented with aorto-enteric fistula) operated on with NAIS bypass were reviewed. The median time from the primary aortic intervention to the NAIS bypass procedure was 32 months (range 0 – 252 months). Mean ± standard deviation operating time was 645 ± 160 minutes, mean blood loss was 6 277 ± 6 525 mL, mean length of intensive care unit stay was 5.3 ± 3.7 days, and mean length of overall hospital stay was 21.2 ± 11.4 days. Thirty-five patients (88%) had a positive microbial culture; the most commonly isolated pathogen was Candida spp. The majority of patients survived for 30 days (n = 35 [88%]), and 33 (83%) and 32 (80%) patients survived for 90 days and one year, respectively. The number of surviving patients free from antimicrobial treatment at 90 days, six months, and one year was 19 (58%), 29 (88%), and 30 (94%). After a mean long term follow up of 69.9 ± 44.7 months, 20 patients were still alive.Conclusion: The NAIS bypass procedure offered reasonable survival and functional outcomes, and was associated with a high cure rate, defined as freedom from any antimicrobial treatment.
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| 18. |
- Persson, Erik, 1972-, et al.
(författare)
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Utilization of the natural variation in wood properties–a comparison between pilot plant and mill scale trials
- 2003
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Ingår i: Proceedings of International Mechanical Pulping Conference, Quebec City. - 1896742866 ; , s. 83-90
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Konferensbidrag (refereegranskat)abstract
- Four different pulpwood classes of Norway spruce (Picea abies (L.) Karst). were tested in mill scale production of TMP at Hallsta Papermill. The objectives of the trial were to evaluate both rather extreme and more traditional roundwood classes in a full-scale TMP-plant with respect to pulp properties and energy requirements. The experiment was partly based on the results from the proceeding pilot plant trial within the EuroFiber project. The results generally confirmed the findings in the pilot plant trial. Young wood with a high proportion of juvenile wood gave a pulp with attractive optical properties, but somewhat lower tear index and higher energy consumption. The other extreme, sawmill chips from old trees of heavy dimensions, required lower energy input and gave higher tear index, but inferior optical properties. The two more traditional classes gave pulps with properties between the two extremes.
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| 19. |
- Persson, Erik, 1972-, et al.
(författare)
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Very Low Energy High Yield Pulping
- 2022
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Ingår i: Proceedings of the International Mechanical Pulping Conference. ; , s. 41-46
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The project goal was to efficiently separate spruce fibers with preserved fiber stiffness and a low content of unsepa-rated fibers (shive content max~1%) using minimal amounts of electricity. The project tested process variants based on the .HT-CTMP-process concept. Above room temperature, the mechanical properties of water saturated wood are pri-marily determined by the lignin, which softens with increas-ing temperature and water content. The lignin is not evenly distributed in the wood structure, and the pattern of fiber separation in wood will therefore to a large extent be de-pendent on the properties of the lignin. The relative softening temperature increases with increasing strain rate. In me-chanical defibration at temperatures below the lignin soften-ing temperature, a large proportion of the fibers will frac-ture across the fiber direction. At elevated temperatures, above the lignin softening interval, an increasing proportion of the fibers will be separated in the middle lamella along the fiber axis, i.e. with a higher fiber separation selectivity. Sulfonation of wood reduces the degree of crosslinking in lignin and increases the charge. The structural change makes the wood softer at a certain temperature. In a pilot trial Norway spruce (Picea abies (L.) Karst.) chips were re-fined at 130, 160 or 180 degrees C after impregnation with 25 or 50 kg/ton sodium sulfite in a pH range from 4,5 to 12. The temperature was the most important factor affecting the shives/energy relation. The sulfite charge and the pH-level also affect the results, but less than the temperature within the evaluated range. The results show there is a potential to produce pulps with a shive content of about 1% using less than 200 kWh/ton at 180 °C in the pre-heater and inlet of the refiner. Producing a high yield, fiber material with pre-served fiber dimensions and low content of shives using a few hundred kWh/ton opens for new opportunities both in paper and board production, but also in new applications where the bonding between fibers is achieved by other means than in traditional paper and paperboard products.
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| 20. |
- Rahman, Hafizur, Researcher, 1978-, et al.
(författare)
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Characterization of impregnation depth in wood fibers related manufacturing of advanced fiber materials replacing fossil-based materials
- 2022
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Ingår i: Proceedings International mechanical Pulping Conference. ; , s. 162-165
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- An underestimated problem in the rapidly growing CTMP industry is uneven sulphonation. Optimizing the unit operations before chip refining, chip washing, steaming, impregnation, and preheating improves efficiency, provides smoother fiber properties, and reduces the cost of certain properties in the final product. Impregnation is crucial to the CTMP quality, and a further improvement in its smoothness requires a careful study of the optimization of pulpwood chipping and the chipping process with reduction technology at sawmills. The CTMP system, however, is difficult to optimize due to the lack of rapid measurement methods for determining the smoothness of the impregnation at the fiber level. The ability to study how the processing system can be optimized requires a robust method of measuring the degree of sulphonation at the fiber level. It is possible to study CTMP's degree of sulphonation at the fiber level by measuring the distribution of elemental sulphur and counterions of the sulphonate groups, such as sodium or calcium. Thus, we are developing an XRF (x-ray fluorescence) technology based on scanning imaging and energy-resolved X-ray spectrum from a collimated X-ray source. The measurement technology is developed so that it can be used in pulp industry laboratories.
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| 21. |
- Rahman, Hafizur, Researcher, 1978-, et al.
(författare)
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Development of improved CTMP with even sulphonate distribution at fibre level using XRF analysis
- 2022
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Ingår i: Transactions of the 17th Fundamental Research Symposium held in Cambridge: August/September 2022. - 9780992616366 ; , s. 3-11
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Konferensbidrag (refereegranskat)abstract
- Optimizing the fiber property distribution could increase the pulp properties as well as the process efficiency of chemimechanical pulps (CMP/CTMP). This can only be achieved with a better understanding of how evenly distributed sulphonate concentrations are between the individual CTMP fibres. Given that the quality of wood chips varies with the chipping methods used in pulpwood processing and sawmill processing, as well as with the chip screening system, it is a challenge to develop an impregnation process that ensures even distribution of sodium sulphite (Na2SO3) in the liquid used to impregnate the chemimechanical pulp (CMP/CTMP). Therefore, the distribution of sulphonate groups within wood chips and individual fibers must be measured at the microscale level. On a micro level, the degree of unevenness, ie, the amount of fiber sulphonation and softening before defibration, cannot be determined due to the use of excessively robust or complex processing methods. By having it, we could better understand how sulphonation occurs before defibration, so we could improve impregnation. Developing a laboratory-scale miniaturized energy dispersive X-ray fluorescence (ED-XRF) method that measures sulfur distribution at the fiber level can enable us to study the influence of impregnation on improving processes.
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| 22. |
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| 23. |
- Rahman, Hafizur, Research Engineer, 1978-, et al.
(författare)
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Improve the competitive advantages of pulp fiber-based products over fossil-based materials
- 2021
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Ingår i: Accelerating the progress towards the 2030 SDGs in times of crisis. - Östersund : Mid Sweden University. - 9789189341173 ; , s. 2133-2145
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Konferensbidrag (refereegranskat)abstract
- To improve the competitive advantages of pulp fibre based materials such as tissue and packaging products over the fossil-based products, it is of key importance to improve the knowledge of the selectivity of the cooking process. There is also demand to expand the fundamental scientific understanding of pulp and paper manufacturing systems because of growing demand for replacing plastics. However, it is challenged to improve the selectivity of the cooking process by optimizing unit operation such as impregnation, cooking and refining. For pulp production based on chips regardless of chemical (kraft or sulphite) or high-yield (chemimechanical or semi-chemical pulp) pulping process, the efficiency of the impregnation is always crucial. To improve impregnation uniformity, we need to study how even distribution of lignin releases down to fibre level via easily impregnated wood chips. It can be achieved, using classic measures such as; equalized hydroxide ion concentration, increased initial sulphide ion concentration, low sodium ion concentration and low boiling temperature combined with the oxidative and reductive environment to understand how the chemicals quickly enter and distribute in the chips. However, we have studied the uniformity of impregnation at fibre level by the possibility of accurately measuring S and Na content by collimating the X-ray beam into a ~200 µm spot in diameter using energy-dispersive X-ray fluorescence (ED-XRF) spectrometry. In addition, we have also studied improved impregnation by selective cooking systems for sulphate pulp in oxidative (polysulfide) and reductive (sodium borohydride, NaBH4) environments. Our aim is to develop standard measurement methods to improve the smoothness of fibre properties for tissue and packaging products to reach the sustainable development goal (SDG) stated by the UN at target 9.5 “Enhance research and upgrade industrial technologies”.
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| 24. |
- Rahman, Hafizur, Research Engineer, 1978-, et al.
(författare)
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Maximized wood chip impregnation efficiency validated by new miniaturized X-ray fluorescence techniques
- 2019
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Konferensbidrag (refereegranskat)abstract
- Manufacturing of chemi-thermomechanical pulp (CTMP) is increasing due to increased demand for packaging materials such as cardboard as well as tissue and other hygiene products. Today high yield pulp (HYP) is produced from different wood species. It is well-known that chip-refining is normally responsible for more than 60% of the electric energy consumption in most high yield pulping process. There are opportunities to improve energy efficiency and quality stability in defibration processes by means of optimizing impregnation. Impregnation is a key unit operation in CTMP production as well as in all chemical pulping and biorefinery systems. The efficiency of the impregnation is known to be crucial (Ferritsius et al. 1985; Gorski et al. 2010). Early research showed difficulties to achieve even distribution of sulphite and sodium ions in wood chips resulting in inhomogeneous fibre properties (Bengtsson et al. 1988). Increased and homogenous sulphonation leads to reduced shive content, which is a key factor in all end product applications. To address this issue developing a new type miniaturized X-ray based technique (XRF) to measure local concentration of sulphur and sodium across wood chips and in individual fibres could become a key tool. The presence of elements as sulphur and sodium can be detected by X-ray fluorescence (XRF) or spectral absorption. At the XRF, images the surface of the sample using specific energies from K-shell or L-shell fluorescence. This method is investigated at the X-ray laboratory in Mid Sweden University research centre STC (Sensitive Things that Communicate) (Norlin et al. 2018). At the spectral absorption, images specific K-shell absorption energies in transmission X-ray images of the sample, a method widely used in medical diagnosis. This transmission method might also be further investigated for this application in the future (Frojdh et al. 2013; Reza et al. 2013). Both methods can be validated by using monoenergetic radiation from synchrotron facilities. An XRF imaging system uses a collimated X-ray source and a spectroscopic detector. The sample is scanned to make an image of the content of the substances of interest. A specific challenge in this case is that the low energy fluorescence photons from sulphur (S) and sodium (Na) are easily absorbed in air, which makes imaging in a different atmosphere necessary. The measurement setup has been simulated using MCNP (C. J. Werner, 2017) to validate the system setup and to select the correct, geometry, shielding, filtering and atmosphere for the measurement. The solution was to use a titanium box flooded with helium to minimise the absorption of fluorescence photons and to shield from scattered photons that might disturb the measurement, fig 1. A filter has been added to the X-ray source to make it nearly monoenergetic and to avoid emission of photons with energies close to the expected fluorescence. The system has been used to estimate sodium and sulphur content in low grammage handsheet (CTMP) or single wood chip samples. It is possible to build a laboratory instrument similar to the prototype setup to obtain the distribution of sodium and sulphur in XRF imaging. Figure 1: Photograph of XRF measurement setup with of moveable Helium atmosphere Ti boxHowever, the technique we are developing can become useful in mills to improve and control process efficiency, product properties and to find solutions to process problems in future. In addition, a more even distribution of the sulphonation can reduce specific energy demand in chip refining at certain shive content. References 1. Bengtsson, G., Simonson, R., Heitner, C., Beatson, R., and Ferguson, C. (1988): Chemimechanical pulping of birch wood chips, Part 2: Studies on impregnation of wood blocks using scanning electron microscopy and energy dispersive x-ray analysis, Nord. Pulp Paper Res. J. 3 (3), 132-138.2. C. J. Werner, (2017): MCNP User's manual, Code Version 6.2, Los Alamos National Laboratory report, LA-UR-17-29981.3. Ferritsius, O., and Moldenius, S. (1985): The effect of impregnation method on CTMP properties. In International Mechanical Pulping Conference Proceedings, SPCI, Stockholm (p. 91).4. Frojdh, C., Norlin, B. and Frojdh, E. (2013): Spectral X-ray imaging with single photon processing detectors, Journal of Instrumentaion, Volume 8, Article number C02010. 5. Gorski, D., Hill, J., Engstrand, P., and Johansson, L. (2010): Reduction of energy consumption in TMP refining through mechanical pre-treatment of wood chips, Nord. Pulp Paper Res. J, 25(2), 156-161.6. Norlin, B., Reza, S., Fröjdh, C. and Nordin, T. (2018): Precision scan-imaging for paperboard quality inspection utilizing X-ray fluorescence, Journal of Instrumentation, Volume: 13, Article number C01021.7. Reza, S., Norlin, B. and Thim, J. (2013): Non-destructive method to resolve the core and the coating on paperboard by spectroscopic x-ray imaging, Nord. Pulp Paper Res. J. 28 (3), 439-442.
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| 25. |
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| 26. |
- Rahman, Hafizur, Research Engineer, 1978-, et al.
(författare)
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Measurement of S and Na distribution in impregnated wood chip by XRF
- 2021
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Ingår i: TAPPICon Virtual 2021. - : TAPPI Press. - 9781713829683 ; , s. 547-553
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Konferensbidrag (refereegranskat)abstract
- As there are increasing demands to replace plastics especially as packaging material with renewable, easy to recycle and compostable materials as those produced by paper industry, there is an increasing demand also to improve the fundamental scientific understanding of pulp and paper manufacturing systems. High yield pulping (HYP) processes, such as CTMP, are increasingly interesting for packaging material as well as manufacturing of hygiene paper. The yield from wood chips to final fiber is about 90%-98% and due to that, the lignin (28% of coniferous wood) plays a key role when designing properties of packing materials. A key unit operation when producing CTMP is the pre-treatment of wood chips before defibration. In order to separate the wood to individual fibers with a minimum amount of electricity it is necessary to soften the lignin. The lignin is softened by means of a combination of sulphonation at high pH and elevated temperatures in the preheater and in the refiner, where the fiber separation occurs. As the size of wood chips is normally about 20 mm in length, 3-4 mm in thickness at the same time the fiber size is 20-40 μm in width with 1.5-5 mm in length, it is challenging to create a process technology that gives an even distribution across the wood chips of the sodium sulphite (Na2SO3) containing liquid used for impregnation. In order to improve the impregnation technology, it is valuable to measure the sulphonation degree on a detailed level. Our XRF imaging system using a collimated X-Ray source and an energy-dispersive X-Ray spectroscopy can make an image of sulphur (S) and sodium (Na) across wood chips or in individual fibers.
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| 27. |
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| 28. |
- Rahman, Hafizur, Researcher, 1978-, et al.
(författare)
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On-Site X-ray Fluorescence Spectrometry Measurement Strategy for Assessing the Sulfonation to Improve Chemimechanical Pulping Processes
- 2022
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Ingår i: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 7:51, s. 48555-48563
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Tidskriftsartikel (refereegranskat)abstract
- Minimizing the fiber property distribution would have the potential to improve the pulp properties and the process efficiency of chemimechanical pulp. To achieve this, it is essential to improve the level of knowledge of how evenly distributed the sulfonate concentration is between the individual chemimechanical pulp fibers. Due to the variation in quality between pulpwood and sawmill chips, as well as the on-chip screening method, it is difficult to develop an impregnation system that ensures the even distribution of sodium sulfite (Na2SO3) impregnation liquid. It is, therefore, crucial to measure the distribution of sulfonate groups within wood chips and fibers on a microscale. Typically, the degree of unevenness, i.e., the amount of fiber sulfonation and softening prior to defibration, is unknown on a microlevel due to excessively robust or complex processing methods. The degree of sulfonation at the fiber level can be determined by measuring the distribution of elemental sulfur and counterions of sulfonate groups, such as sodium or calcium. A miniaturized energy-dispersive X-ray fluorescence (ED-XRF) method has been developed to address this issue, enabling the analysis of sulfur distributions. It is effective enough to be applied to industrial laboratories for further development, i.e., improved image resolution and measurement time.
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| 29. |
- Sedin, John, 1982-, et al.
(författare)
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High Resolution Intravital Imaging of the Renal Immune Response to Injury and Infection in Mice
- 2019
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Ingår i: Frontiers in Immunology. - : Frontiers Media S.A.. - 1664-3224. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- We developed an experimental set up that enables longitudinal studies of immune cell behavior in situ in the challenged as well as unchallenged kidney of anesthetized mice over several hours. Using highly controlled vacuum to stabilize the kidney, the superficial renal cortex could continuously be visualized with minimal disruption of the local microenvironment. No visible changes in blood flow or neutrophils and macrophages numbers were observed after several hours of visualizing the unchallenged kidney, indicating a stable tissue preparation without apparent tissue damage. Applying this set up to monocyte/macrophage (CX(3)CR1(GFP/+)) reporter mice, we observed the extensive network of stellate-shaped CX(3)CR1 positive cells (previously identified as renal mononuclear phagocytes). The extended dendrites of the CX(3)CR1 positive cells were found to bridge multiple capillaries and tubules and were constantly moving. Light induced sterile tissue injury resulted in rapid neutrophil accumulation to the site of injury. Similarly, microinfusion of uropathogenic Escherichia coli into a single nephron induced a rapid and massive recruitment of neutrophils to the site of infection, in addition to active bacterial clearance by neutrophils. In contrast, the kidney resident mononuclear phagocytes were observed to not increase in numbers or migrate toward the site of injury or infection. In conclusion, this model allows for longitudinal imaging of responses to localized kidney challenges in the mouse.
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| 30. |
- Sediqi, Ehsan, et al.
(författare)
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Laparoscopic Heller myotomy or pneumatic dilatation in achalasia: results of a prospective, randomized study with at least a decade of follow-up
- 2021
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Ingår i: Surgical Endoscopy. - : Springer Science and Business Media LLC. - 0930-2794 .- 1432-2218. ; 35, s. 1618-1625
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Tidskriftsartikel (refereegranskat)abstract
- Background and objectives: The most efficient long-term treatment strategy for achalasia has yet to be established. This study compared the long-term results (≥ 10years) after either pneumatic dilatations or laparoscopic myotomy using treatment failure as the primary outcome. Secondary objectives were; the frequency and degree of dysphagia and effects on health-related quality of life (QoL). Patients and methods: Out of the 53 patients with achalasia who were initially randomized to either laparoscopic myotomy with a posterior partial fundoplication (LM) or repetitive pneumatic dilatation (PD), 43 remained for scrutiny after a median observation period of 170months (LM; n = 20 and PD; n = 23). Results: At the follow-up of 60months, 10 patients (36%) in the PD group and two patients (8%) in the LM group were classified as treatment failures (p = 0.016). At the latest follow-up time point (≥ 10years), the corresponding numbers were 13 (57%) and 4 (20%), respectively. The Kaplan–Meier analysis of the cumulative incidence of treatment failure revealed a significant advantage of LM over the dilatation strategy (p = 0.036)). QoL assessed by the generic instrument PGWB and the more disease-specific instrument GSRS revealed scores which were similar in the two study groups with no obvious changes over time. Reflux was better controlled in the LM group (p = 0.02 regarding PPI consumption). Conclusions: After more than a decade of follow-up, laparoscopic myotomy reinforces its superiority over repetitive pneumatic dilatation treatment strategy in the management of newly diagnosed achalasia. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.
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| 31. |
- Sörstedt, Erik, 1980-, et al.
(författare)
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Computed tomographic colonography : Comparison of two workstations
- 2005
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Ingår i: Acta Radiologica. - : SAGE Publications. - 0284-1851 .- 1600-0455. ; 46:7, s. 671-678
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To compare two commercially available computed tomography (CT) colonography systems with respect to interobserver variability, the influence of level of expertise, and the gradual reduction of reviewing time for each system. Material and Methods: Two residents and two radiologists using Siemens CTAPP Colography software and Viatronix V3DColon software reviewed supine and prone CT acquisitions from 24 patients in a primary 3D endoluminal view. The observers graded each case with respect to technical quality and diagnostic value, assessed the presence of pathology, and indicated the time spent on the viewing. Results: Significant differences were found in technical quality ( P <0.001) and diagnostic value ( P <0.001) depending on which system was used, with higher scores for the Viatronix software. The agreement between specialists tended to be higher than that between residents (κ = 0.63 (0.30-0.95) vs. κ = 0.51 (0.21-0.81)), and the residents gave significantly ( P <0.001) higher scores of technical quality. However, the level of expertise had no significant impact on the assessments. We noted extensive variability in pathological lesions found by the different observers. The number of findings did not differ between workstations, but the viewers tended to report larger polyp sizes with the Viatronix software. The time needed for viewing decreased significantly from the first to the last examination viewed by each observer. Conclusion: Both the evaluated systems present trustworthy images of the human colon, but in a primary 3D setting the Viatronix software is favored owing to the userfriendly interface, higher experienced technical quality, and better diagnostic value. © 2005 Taylor & Francis.
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