| 1. |
- Segerholm, Kristoffer, 1979-
(författare)
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Characteristics of wood plastic composites based on modified wood : Moisture properties, biological performance and micromorphology
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Biobased materials made from renewable resources, such as wood, play an important role in the sustainable development of society. One main challenge of biobased building materials is their inherent moisture sensitivity, a major cause for fungal decay, mold growth and dimensional instability, resulting in decreased service life as well as costly maintenance. A new building material known as wood-plastic composites (WPCs) has emerged. WPCs are a combination of a thermoplastic matrix and a wood component, the former is usually recycled polyethylene or polypropylene, and the latter a wood processing residual, e.g. sawdust and wood shavings.The objective of this thesis was to gain more insight about characteristics of WPCs containing a modified wood component. The hypothesis was that a modified wood component in WPCs would increase the moisture resistance and durability in outdoor applications. The study comprises both injection molded and extruded WPC samples made with an unmodified, acetylated, thermally modified or furfurylated wood component in a polypropylene (PP), high density polyethylene (HDPE), cellulose ester (CAP, a cellulose ester containing both acetate and propionate substituents) or polylactate (PLA) matrix. The WPCs were prepared with 50-70 weight-% wood. The emphasis was on studying the moisture sorption, fungal resistance and micromorphological features of these new types of composites. Water sorption in both liquid and vapor phases was studied, and the biological performance was studied both in laboratory and in long term outdoor field tests. Micromorphological features were assessed by analyzing of the wood component prior to and after processing, and by studying the composite microstructure by means of a new sample preparation technique based on UV excimer laser ablation combined with scanning electron microscopy (SEM).Results showed that the WPCs with a modified wood component had a distinctly lower hygroscopicity than the WPCs with unmodified wood, which resulted in less wood-plastic interfacial cracks when subjected to a moisture soaking-drying cycle. Durability assessments in field and marine tests showed that WPCs with PP or CAP as a matrix and 70 weight-% unmodified wood degraded severely within a few years, whereas the corresponding WPCs with a modified wood component were sound after 7 years in field tests and 6 years in marine tests. Accelerated durability tests of WPCs with PLA as a matrix showed only low mass losses due to decay. However, strength losses due to moisture sorption suggest that the compatibility between the PLA and the different wood components must be improved. The micromorphological studies showed that WPC processing distinctly reduces the size and changes the shape of the wood component. The change was most pronounced in the thermally modified wood component which became significantly reduced in size. The disintegration of the modified wood components during processing also creates a more homogeneous micromorphology of the WPCs, which may be beneficial from a mechanical performance perspective. Future studies are suggested to include analyses of the surface composition, the surface energy and the surface energy heterogeneity of both wood and polymer components in order to tailor new compatible wood-polymer combinations in WPCs and biocomposites.
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| 2. |
- Asayama, Shinichiro, et al.
(författare)
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Three institutional pathways to envision the future of the IPCC
- 2023
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Ingår i: Nature Climate Change. - : Nature Portfolio. - 1758-678X .- 1758-6798. ; 13:9, s. 877-880
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Tidskriftsartikel (refereegranskat)abstract
- The IPCC has been successful at building its scientific authority, but it will require institutional reform for staying relevant to new and changing political contexts. Exploring a range of alternative future pathways for the IPCC can help guide crucial decisions about redefining its purpose.
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| 3. |
- Broadaway, K Alaine, et al.
(författare)
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Loci for insulin processing and secretion provide insight into type 2 diabetes risk.
- 2023
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Ingår i: American Journal of Human Genetics. - : Elsevier. - 0002-9297 .- 1537-6605. ; 110:2, s. 284-299
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Tidskriftsartikel (refereegranskat)abstract
- Insulin secretion is critical for glucose homeostasis, and increased levels of the precursor proinsulin relative to insulin indicate pancreatic islet beta-cell stress and insufficient insulin secretory capacity in the setting of insulin resistance. We conducted meta-analyses of genome-wide association results for fasting proinsulin from 16 European-ancestry studies in 45,861 individuals. We found 36 independent signals at 30 loci (p value < 5 × 10-8), which validated 12 previously reported loci for proinsulin and ten additional loci previously identified for another glycemic trait. Half of the alleles associated with higher proinsulin showed higher rather than lower effects on glucose levels, corresponding to different mechanisms. Proinsulin loci included genes that affect prohormone convertases, beta-cell dysfunction, vesicle trafficking, beta-cell transcriptional regulation, and lysosomes/autophagy processes. We colocalized 11 proinsulin signals with islet expression quantitative trait locus (eQTL) data, suggesting candidate genes, including ARSG, WIPI1, SLC7A14, and SIX3. The NKX6-3/ANK1 proinsulin signal colocalized with a T2D signal and an adipose ANK1 eQTL signal but not the islet NKX6-3 eQTL. Signals were enriched for islet enhancers, and we showed a plausible islet regulatory mechanism for the lead signal in the MADD locus. These results show how detailed genetic studies of an intermediate phenotype can elucidate mechanisms that may predispose one to disease.
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| 4. |
- Cristescu, Carmen
(författare)
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Self-bonding of beech veneers
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents studies on the self-bonding of veneers, and investigations into the properties of boards obtained by hot-pressing beech veneers without adhesives. The raw material is pressed at temperatures from 200 to 250ºC, at pressures from 4 to 6 MPa and pressing times from 240 to 360 s. The hot-pressing of five layers of veneers results in a self-bonded, compressed, densified board, darker than the raw material. The manufacturing process was optimised using a statistical analysis, the response surface experimental design method. The input factors were the pressing parameters and the output factors were characteristics of the product, the raw material properties being kept constant. The results showed correlations between the pressing parameters, especially temperature, as input data and the physical and mechanical properties as responses. Resistance to water absorption and swelling as well as shear strength, bending strength, and hardness were all enhanced by more severe pressing conditions. All the samples pressed at 250ºC became water-resistant while samples pressed at 200ºC delaminated rapidly in water. It was found that the colour of the edges can be used as an indication of the hardness. Chemical investigations were performed on samples taken from veneers (raw material), bond-lines and inner parts of pressed veneer. A High-Performance Liquid Chromatography (HPLC) analysis was used to detect and compare the levels of water-soluble monosaccharides (glucose and fructose) in the veneer before pressing and the levels of 5-hydroxymethyl-furfural (HMF) and furfural in boards. From the results obtained in this thesis it is suggested, that besides other degraded compounds of hemicelluloses, the monosaccharides were transformed into hydroxymethyl-furfural during hot-pressing that could further participate in forming new browning compounds that are related to the bonding phenomenon. The UV spectroscopic analysis to evaluate the content of water-soluble phenols showed that the bond-line had a higher amount of conjugated phenols than the inner veneer suggesting a migration of degraded lignin towards the veneer surfaces during pressing. A CP/MAS 13C NMR study on the solid material showed that the presence of β-ether structures and methoxyl groups in lignin was higher in the bond-line, supporting the hypothesis of a migration of lignin and possibly a condensation reaction occurring at higher temperatures, explaining the water-resistance property acquired by the boards.In a comparative study, oxidative activation with hydrogen peroxide and ferrous sulfate as a catalyst was performed before pressing. Boards made from beech veneer subjected to the pre-treatment step showed a greater mass loss, a lower thickness swelling but also a somewhat lower shear strength. For beech veneers such an oxidative pre-treatment step could be used to gain water-resistant boards pressed at lower pressing temperatures or shorter times than those needed to bond untreated veneers. Scots pine veneers were found to be less suitable for self-bonding than beech veneers. Boards of Scots pine hot-pressed without the oxidative pre-treatment delaminated in water, whereas, under the same pressing conditions, boards made from pre-treated veneers showed a water-resistant bond-line.
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| 5. |
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| 6. |
- van Blokland, Joran
(författare)
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Thermally Modified Timber : Novel Aspects of Bending Behaviour Towards Grading and Structural Applications
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Thermally modified timber (TMT) has gained market share in Europe as an environmentally friendly and durable building material. Unfortunately, TMT products are currently prohibited for use in structural applications as there is insufficient data to estimate the loss in strength due to thermal modification. This thesis work explored the fundamentals related to the static 4-point bending (4PB) behaviour of TMT needed to expand its use in the construction sector.The effect of treatment on checks in and around knots, and their combined effect on the 4PB behaviour of TMT, was studied with digital image correlation on 9 Norway spruce boards. For 190 matched board pairs of Norway spruce, one board was modified according to the ThermoWood® Thermo-D process, and the other remained untreated for comparison. One-hundred (100) board pairs were used to assess the effect of treatment on the 4PB properties and behaviour, and on indicating properties (IPs): density, longitudinal resonance and ultrasonic wave speed. The remaining 90 board pairs were weathered for 30 months to evaluate differences in the degree of checking, the IPs and the 4PB properties and behaviour. Fibre angle was measured on all board surfaces using a WoodEye 5 high-resolution laser scanner to study the location of failure in TMT, and to potentially improve bending strength predictions.Thermal modification decreased the bending strength by approximately 40%; however, the presence of knots still determined the type and location of failure. Thermal modification and weathering play a critical role in the formation of severe checks in timber, but their presence had no significant influence on the bending properties. TMT could be graded using acoustic-type grading machines already available at most sawmills, and these principles could be applied to predict the presence of internal checks. Scanning the fibre direction improved strength predictions of TMT and enabled the failure location to be predicted. Grading timber before thermal modification could reduce the rejection rate of TMT if manufacturers select raw material that is resistant to internal checking and is of a suitable grade.
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| 7. |
- Watts, Nick, et al.
(författare)
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The 2020 report of The Lancet Countdown on health and climate change : responding to converging crises
- 2021
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Ingår i: The Lancet. - : Elsevier. - 0140-6736 .- 1474-547X. ; 397:10269, s. 129-170
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Forskningsöversikt (refereegranskat)abstract
- The Lancet Countdown is an international collaboration established to provide an independent, global monitoring system dedicated to tracking the emerging health profile of the changing climate.The 2020 report presents 43 indicators across five sections: climate change impacts, exposures, and vulnerabilities; adaptation, planning, and resilience for health; mitigation actions and health co-benefits; economics and finance; and public and political engagement. This report represents the findings and consensus of the 35 leading academic institutions and UN agencies that make up The Lancet Countdown, and draws on the expertise of climate scientists, geographers, engineers, experts in energy, food, and transport, economists, social, and political scientists, data scientists, public health professionals, and doctors.
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