| 1. |
- Muzamal, Muhammad, 1986
(författare)
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Steam Explosion of Wood
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The rising price of petroleum and environmental concerns regarding CO2 emissions has increased interest in alternative renewable resources. Biomass can be considered as an excellent alternative raw material. A biorefinery uses biomass and produces fuel, energy and value-added chemicals. The biorefinery is an emerging field and requires much development to compete with already established petroleum-based industries. One of the greatest challenges to the biorefinery is that the raw material; biomass, has a complex chemical composition and physical structure. A pretreatment process is necessary to induce physico-chemical changes in the biomass and transform it into easily digestible material. The main factor limiting enzymatic digestion of biomass is accessibility to chemical constituents. Steam Explosion (SE) pretreatment is a promising process that has many potential benefits compared to the alternatives, e.g. it has less hazardous process chemicals and conditions, less environmental impact, fewer energy requirements and lower capital investment.Existing literature on the SE process mainly concerns products obtained after the process. Knowledge about the physical processes that take place during the SE pretreatment is limited. This licentiate thesis is based on experimental and modelling studies performed with the aim of gaining knowledge of the basic mechanisms of this process. The SE is a three-step process that involves; (i) treatment of wood with pressurized steam for a specific period of time, (ii) explosion of wood chips through the rapid release of pressure, and (iii) impact of softened wood chips with other chips and vessel walls. In the experimental part these steps have been carefully isolated and the effects of these steps on internal and external structures of single spruce wood pieces have been studied. The effect of vapour expansion and the creation of stresses during the explosion step on a single cell of spruce wood (with four layers; P, S1, S2 and S3) at high temperature and moisture content have been modelled using the Finite Element Method.The study reveals that all the steps of the SE process contribute to structural changes in the wood material and increase pore size which increases the accessibility of chemical reagents and enzymes. A wood piece disintegrates into smaller pieces during the impact step. The vapour expansion inside cells during the explosion step causes each cell to expand in all directions and creates high stress and strain fields perpendicular to the cell direction. In general, cell wall damage is more likely to occur in cells with thin walls, i.e. earlywood; damaged P, S1 and S3 layers; low MFAs; irregular cross-sections and sharp corners.
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| 2. |
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| 3. |
- Tamminen, T., et al.
(författare)
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Mobile and flexible processing of biomass – EU project Mobile Flip
- 2015
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Ingår i: VTT Technology. - 2242-1211. ; , s. 28-41
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Konferensbidrag (refereegranskat)abstract
- EU project MOBILE FLIP in the SPIRE program aims at developing and demonstrating mobile processes for the treatment of underexploited agro- and forest based biomass resources into products and intermediates. The processes are evaluated in terms of raw material flexibility, as the biomass resources are typically scattered and seasonal. Process concepts have been designed around the key technologies pelletizing, torrefaction, slow pyrolysis, hydrothermal pretreatment and carbonisation. The products vary depending on the process concept, being typically fuels as such or for co-combustion (pellets, torrefied pellets, biocoals), biochars for soil remediation, biodegradable pesticides for agricultural or forestry use or chemicals for wood panel industry and sugars and hydrolysable cellulose as intermediate for the sugar platform. The concept evaluations are supported both by research and industrial (SME and large industries) partners in the whole value chains. Dissemination, communication and exploitation activities are an integral part of the project. Life-cycle analysis and a wide sustainability evaluation (economic, environmental and social assessment) are carried out for the process concepts in order to clarify their potential for flexible raw material valorisation. The partners are represented by the coauthors in this presentation: four SMEs, two large companies, six research organizations. The project duration is four years and total budget approximately EUR 10 million.
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| 4. |
- Zackrisson, Martin, et al.
(författare)
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Scan-o-matic: High-Resolution Microbial Phenomics at a Massive Scale
- 2016
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Ingår i: G3: Genes, Genomes, Genetics. - : Oxford University Press (OUP). - 2160-1836. ; 6:9, s. 3003-3014
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Tidskriftsartikel (refereegranskat)abstract
- The capacity to map traits over large cohorts of individuals—phenomics—lags far behind the explosive development in genomics. For microbes, the estimation of growth is the key phenotype because of its link to fitness. We introduce an automated microbial phenomics framework that delivers accurate, precise, and highly resolved growth phenotypes at an unprecedented scale. Advancements were achieved through the introduction of transmissive scanning hardware and software technology, frequent acquisition of exact colony population size measurements, extraction of population growth rates from growth curves, and removal of spatial bias by reference-surface normalization. Our prototype arrangement automatically records and analyzes close to 100,000 growth curves in parallel. We demonstrate the power of the approach by extending and nuancing the known salt-defense biology in baker’s yeast. The introduced framework represents a major advance in microbial phenomics by providing high-quality data for extensive cohorts of individuals and generating well-populated and standardized phenomics databases
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| 5. |
- Apelgren, Peter, et al.
(författare)
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In Vivo Human Cartilage Formation in Three-Dimensional Bioprinted Constructs with a Novel Bacterial Nanocellulose Bioink
- 2019
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Ingår i: Acs Biomaterials Science & Engineering. - : American Chemical Society (ACS). - 2373-9878. ; 5:5, s. 2482-2490
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Tidskriftsartikel (refereegranskat)abstract
- Bacterial nanocellulose (BNC) is a 3D network of nanofibrils exhibiting excellent biocompatibility. Here, we present the aqueous counter collision (ACC) method of BNC disassembly to create bioink with suitable properties for cartilage-specific 3D-bioprinting. BNC was disentangled by ACC, and fibril characteristics were analyzed. Bioink printing fidelity and shear-thinning properties were evaluated. Cell-laden bioprinted grid constructs (5 X 5 X 1 mm(3)) containing human nasal chondrocytes (10 M mL(-1)) were implanted in nude mice and explanted after 30 and 60 days. Both ACC and hydrolysis resulted in significantly reduced fiber lengths, with ACC resulting in longer fibrils and fewer negative charges relative to hydrolysis. Moreover, ACC-BNC bioink showed outstanding printability, postprinting mechanical stability, and structural integrity. In vivo, cell-laden structures were rapidly integrated, maintained structural integrity, and showed chondrocyte proliferation, with 32.8 +/- 13.8 cells per mm(2) observed after 30 days and 85.6 +/- 30.0 cells per mm(2) at day 60 (p = 0.002). Furthermore, a full-thickness skin graft was attached and integrated completely on top of the 3D-bioprinted construct. The novel ACC disentanglement technique makes BNC biomaterial highly suitable for 3D-bioprinting and clinical translation, suggesting cell-laden 3D-bioprinted ACC-BNC as a promising solution for cartilage repair.
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| 6. |
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| 7. |
- Singh, Shikha, et al.
(författare)
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Orientation of Polylactic Acid–Chitin Nanocomposite Films via Combined Calendering and Uniaxial Drawing: Effect on Structure, Mechanical, and Thermal Properties
- 2021
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Ingår i: Nanomaterials. - : MDPI. - 2079-4991. ; 11:12
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Tidskriftsartikel (refereegranskat)abstract
- The orientation of polymer composites is one way to increase the mechanical properties of the material in a desired direction. In this study, the aim was to orient chitin nanocrystal (ChNC)-reinforced poly(lactic acid) (PLA) nanocomposites by combining two techniques: calendering and solid-state drawing. The effect of orientation on thermal properties, crystallinity, degree of orientation, mechanical properties and microstructure was studied. The orientation affected the thermal and structural behavior of the nanocomposites. The degree of crystallinity increased from 8% for the isotropic compression-molded films to 53% for the nanocomposites drawn with the highest draw ratio. The wide-angle X-ray scattering results confirmed an orientation factor of 0.9 for the solid-state drawn nanocomposites. The mechanical properties of the oriented nanocomposite films were significantly improved by the orientation, and the pre-orientation achieved by film calendering showed very positive effects on solid-state drawn nanocomposites: The highest mechanical properties were achieved for pre-oriented nanocomposites. The stiffness increased from 2.3 to 4 GPa, the strength from 37 to 170 MPa, the elongation at break from 3 to 75%, and the work of fracture from 1 to 96 MJ/m3. This study demonstrates that the pre-orientation has positive effect on the orientation of the nanocomposites structure and that it is an extremely efficient means to produce films with high strength and toughness.
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| 8. |
- Sämfors, Sanna, 1987, et al.
(författare)
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Biofabrication of bacterial nanocellulose scaffolds with complex vascular structure
- 2019
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Ingår i: Biofabrication. - : IOP Publishing. - 1758-5082 .- 1758-5090. ; 11:4
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Tidskriftsartikel (refereegranskat)abstract
- Bacterial nanocellulose (BNC) has proven to be an effective hydrogel-like material for different tissue engineering applications due to its biocompatibility and good mechanical properties. However, as for all biomaterials, in vitro biosynthesis of large tissue constructs remains challenging due to insufficient oxygen and nutrient transport in engineered scaffold-cell matrices. In this study we designed, biofabricated and evaluated bacterial nanocellulose scaffolds with a complex vascular mimetic lumen structure. As a first step a method for creating straight channeled structures within a bacterial nanocellulose scaffold was developed and evaluated by culturing of Human Umbilical Vein Endothelial Cells (HUVECs). In a second step, more complex structures within the scaffolds were produced utilizing a 3D printer. A print mimicking a vascular tree acted as a sacrificial template to produce a network within the nanoporous bacterial nanocellulose scaffolds that could be lined with endothelial cells. In a last step, a method to produce large constructs with interconnected macro porosity and vascular like lumen structure was developed. In this process patient data from x-ray computed tomography scans was used to create a mold for casting a full-sized kidney construct. By showing that the 3D printing technology can be combined with BNC biosynthesis we hope to widen the opportunities of 3D printing, while also enabling the production of BNC scaffolds constructs with tailored vascular architectures and properties.
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| 9. |
- Apelgren, Peter, et al.
(författare)
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Skin Grafting on 3D Bioprinted Cartilage Constructs In Vivo
- 2018
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Ingår i: Plastic and Reconstructive Surgery - Global Open. - 2169-7574. ; 6:9
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Tidskriftsartikel (refereegranskat)abstract
- Background: Three-dimensional (3D) bioprinting of cartilage is a promising new technique. To produce, for example, an auricle with good shape, the printed cartilage needs to be covered with skin that can grow on the surface of the construct. Our primary question was to analyze if an integrated 3D bioprinted cartilage structure is a tissue that can serve as a bed for a full-thickness skin graft. Methods: 3D bioprinted constructs (10x10x1.2mm) were printed using nanofibrillated cellulose/alginate bioink mixed with mesenchymal stem cells and adult chondrocytes and implanted subcutaneously in 21 nude mice. Results: After 45 days, a full-thickness skin allograft was transplanted onto the constructs and the grafted construct again enclosed subcutaneously. Group 1 was sacrificed on day 60, whereas group 2, instead, had their skin-bearing construct uncovered on day 60 and were sacrificed on day 75 and the explants were analyzed morphologically. The skin transplants integrated well with the 3D bioprinted constructs. A tight connection between the fibrous, vascularized capsule surrounding the 3D bioprinted constructs and the skin graft were observed. The skin grafts survived the uncovering and exposure to the environment. Conclusions: A 3D bioprinted cartilage that has been allowed to integrate in vivo is a sufficient base for a full-thickness skin graft. This finding accentuates the clinical potential of 3D bioprinting for reconstructive purposes.
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| 10. |
- Apelgren, Peter, et al.
(författare)
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Vascularization of tissue engineered cartilage-Sequential in vivo MRI display functional blood circulation
- 2021
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Ingår i: Biomaterials. - : Elsevier BV. - 0142-9612 .- 1878-5905. ; 276
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Tidskriftsartikel (refereegranskat)abstract
- Establishing functional circulation in bioengineered tissue after implantation is vital for the delivery of oxygen and nutrients to the cells. Native cartilage is avascular and thrives on diffusion, which in turn depends on proximity to circulation. Here, we investigate whether a gridded three-dimensional (3D) bioprinted construct would allow ingrowth of blood vessels and thus prove a functional concept for vascularization of bioengineered tissue. Twenty 10 x 10 x 3-mm 3Dbioprinted nanocellulose constructs containing human nasal chondrocytes or cell-free controls were subcutaneously implanted in 20 nude mice. Over the next 3 months, the mice were sequentially imaged with a 7 T small-animal MRI system, and the diffusion and perfusion parameters were analyzed. The chondrocytes survived and proliferated, and the shape of the constructs was well preserved. The diffusion coefficient was high and well preserved over time. The perfusion and diffusion patterns shown by MRI suggested that blood vessels develop over time in the 3D bioprinted constructs; the vessels were confirmed by histology and immunohistochemistry. We conclude that 3D bioprinted tissue with a gridded structure allows ingrowth of blood vessels and has the potential to be vascularized from the host. This is an essential step to take bioengineered tissue from the bench to clinical practice.
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