322,878 research outputs found
Dynamics of aluminum use in the global passenger car system: Challenges and solutions of recycling and material substitution
No full textThis thesis analyzes the relationship between the design of vehicles, end-of-life vehicle (ELV) management, and global material production using aluminum as an example. Vehicle manufacturing, material industries and ELV management face different challenges. An important challenge for vehicle manufacturers is the design of lightweight vehicles to reduce energy use and greenhouse gas (GHG) emissions in the use phase for which an increased use of aluminum of different alloys is an attractive option. The aluminum industry has an interest in reducing energy consumption and GHG emissions, which can be accomplished effectively through recycling. ELV management must be improved to enable the first two systems to use aluminum scrap in a sustainable manner. Today, the sorting of different alloys is limited. As a result of having mixed scrap at the ELV phase and limited opportunities for aluminum refining, there may be a future scrap surplus that cannot be absorbed by the aluminum-recycling sink, which is passenger cars. These three sectors are connected through material flows, and a change in one of the sectors can severely affect the others\u27 options for reaching their goals. This thesis addresses the following questions: 1) How are the dynamics of the global vehicle stock changing the boundary condition for aluminum recycling? 2) What are the most effective interventions to minimize a future aluminum scrap surplus? 3) What are the options for material substitution in vehicles to reduce direct and indirect GHG emissions over time? To answer these questions, a system approach is employed to analyze how these three sectors are linked and to explore options for all sectors to reach their objectives in the long term. This thesis employs global bottom-up stock-driven models of the aluminum cycle. A basic model was used to identify the scrap surplus problem. A refined model with segments, components and alloys resolution combined with a source-sink diagram was used to evaluate different solution options. In addition, a global dynamic fleetrecycling MFA model was developed to simulate the future impacts of material substitutions of conventional steel with high-strength steel (HSS) and aluminum on material cycles, energy use and GHG emissions related to the global passenger vehicle fleet. The main findings in this thesis are: i) a continuation of the current practice of cascadic use would eventually result in a scrap surplus because this practice depends on the continuous and fast growth of the secondary casting stock in the global vehicle fleet, a condition that is unlikely to be met. Model simulation indicated a non-recyclable scrap surplus by approximately 2018\ub15 if no alloy sorting is introduced. The surplus is potentially substantial and could grow to reach a level of 0.4-2 kg/cap/yr by 2050, thereby significantly reducing the option of the aluminum industry to reduce its energy consumption through recycling. ii) Drastic changes in ELV management practices are necessary to make use of the growing scrap flow in the future, including further dismantling and efficient component-to-component recycling, alloy sorting of mixed shredded scrap, and designing recycling-friendly alloys that function as alternative sinks for aluminum scrap. iii) Light-weighting has the potential to substantially reduce global emissions of vehicles (9-18 gigatons cumulative CO2-eq. between 2010 and 2050). In the medium term (5-15 years), global emissions reductions from substituting standard steel with aluminum are similar to those achievable by HSS; however, over a longer term (after 15-20 years), substitution with aluminum can reduce total emissions more effectively, provided that the wrought aluminum will be recycled back into automotive wrought aluminum. The environmental consequences of products in general and passenger cars in particular have led to an increasing awareness of the dependencies between the shaping of vehicles and the shaping of the environment. Governments and intergovernmental bodies have formulated quality goals for the environment, such as the 2-degree target, and have introduced emissions standards, thereby extending the responsibility of automobile manufacturers to the use phase. On the materials side, legislation has been introduced to extend producer responsibility, mainly with the goal of avoiding toxic substances and reducing the amount of waste, as is noted in different end-of-life vehicle (ELV) legislation and directives. The current ELV directives do not sufficiently address the management of material systems as a whole or quality issues related to material recovery. To harmonize ELV management with goals for the global aluminum cycle and its impacts for the environment, it is essential to understand how the above-mentioned systems interact.Has partsPaper 1: Modaresi, Roja; M\ufcller, Daniel B.. The Role of Automobiles for the Future of Aluminum Recycling. Environmental Science and Technology 2012 ;Volum 46.(16) s. 8587-8594 http://dx.doi.org/10.1021/es300648w Copyright \ua9 2012 American Chemical SocietyPaper 2: Rombach, Georg; Modaresi, Roja; M\ufcller, Daniel B.. Aluminium Recycling- Raw Material Supply from a Volume and Quality Constraint System. World of Metallurgy - ERZMETALL 2012 ;Volum 65.(3) s. 157-162Paper 3: Modaresi, Roja; L\uf8vik, Amund Nordli; M\ufcller, Daniel Beat. Component- and Alloy-Specific Modeling for Evaluating Aluminum Recycling Strategies for Vehicles. JOM: The Member Journal of TMS 2014 ;Volum 66.(11) s. 2262-2271., The article is not included due to copyright available at http://dx.doi.org/10.1007/s11837-014-0900-8 Paper 4: L\uf8vik, Amund Nordli; Modaresi, Roja; M\ufcller, Daniel Beat. Long-term strategies for increased recycling of automotive aluminum and its alloying elements. Environmental Science and Technology 2014 ;Volum 48.(8) s. 4257-4265 http://dx.doi.org/10.1021/es405604g Copyright \ua9 2014 American Chemical SocietyPaper 5: Modaresi, Roja; Pauliuk, Stefan; L\uf8vik, Amund Nordli; M\ufcller, Daniel Beat. Global Carbon Benefits of Material Substitution in Passenger Cars until 2050 and the Impact on the Steel and Aluminum Industries. Environmental Science and Technology 2014 ;Volum 48. s. 10776-10784 http://dx.doi.org/10.1021/es502930w Copyright \ua9 2014 American Chemical Society PublisherNTNU SeriesDoctoral thesis at NTNU;2015:11
Deciphering the role of substrate stiffness to enhance internalization efficiency of plasmid DNA in stem cells using lipid-based nanocarriers
No full textThis study investigates the role of substrate stiffness on non-viral transfection of human adipose-derived stem cells (hASCs) with the aim to maximize hASCs expression of vascular endothelial growth factor (VEGF). The results confirm the direct effect of substrate stiffness in regulating cytoskeletal remodeling and corresponding plasmid internalization
The role of substrate stiffness in stem cell transfection of plasmid DNA using lipid-based nanocarriers
No full textStatement of Purpose: Human adipose-derived stem cells (hASCs) express vascular endothelial growth factor (VEGF) as one of the regulators of their proliferation and differentiation. To enhance the expression of this growth factor in hASCs, non-viral transfection methods such as cationic polymers, lipids, and peptide conjugates are attractive candidates. Aside from the type of carrier, internalization of plasmid DNA encoded for VEGF is also dependent on the elasticity of the cell’s substrate which controls the cytoskeletal remodeling. This study investigates the role of substrate stiffness on non-viral transfection of hASCs with the aim to maximize hASCs expression of VEGF
Dynamics of aluminum use in the global passenger car system: Challenges and solutions of recycling and material substitution [Elektronisk resurs]
No full textThis thesis analyzes the relationship between the design of vehicles, end-of-life vehicle (ELV) management, and global material production using aluminum as an example. Vehicle manufacturing, material industries and ELV management face different challenges. An important challenge for vehicle manufacturers is the design of lightweight vehicles to reduce energy use and greenhouse gas (GHG) emissions in the use phase for which an increased use of aluminum of different alloys is an attractive option. The aluminum industry has an interest in reducing energy consumption and GHG emissions, which can be accomplished effectively through recycling. ELV management must be improved to enable the first two systems to use aluminum scrap in a sustainable manner. Today, the sorting of different alloys is limited. As a result of having mixed scrap at the ELV phase and limited opportunities for aluminum refining, there may be a future scrap surplus that cannot be absorbed by the aluminum-recycling sink, which is passenger cars. These three sectors are connected through material flows, and a change in one of the sectors can severely affect the others' options for reaching their goals. This thesis addresses the following questions: 1) How are the dynamics of the global vehicle stock changing the boundary condition for aluminum recycling? 2) What are the most effective interventions to minimize a future aluminum scrap surplus? 3) What are the options for material substitution in vehicles to reduce direct and indirect GHG emissions over time? To answer these questions, a system approach is employed to analyze how these three sectors are linked and to explore options for all sectors to reach their objectives in the long term. This thesis employs global bottom-up stock-driven models of the aluminum cycle. A basic model was used to identify the scrap surplus problem. A refined model with segments, components and alloys resolution combined with a source-sink diagram was used to evaluate different solution options. In addition, a global dynamic fleetrecycling MFA model was developed to simulate the future impacts of material substitutions of conventional steel with high-strength steel (HSS) and aluminum on material cycles, energy use and GHG emissions related to the global passenger vehicle fleet. The main findings in this thesis are: i) a continuation of the current practice of cascadic use would eventually result in a scrap surplus because this practice depends on the continuous and fast growth of the secondary casting stock in the global vehicle fleet, a condition that is unlikely to be met. Model simulation indicated a non-recyclable scrap surplus by approximately 2018±5 if no alloy sorting is introduced. The surplus is potentially substantial and could grow to reach a level of 0.4-2 kg/cap/yr by 2050, thereby significantly reducing the option of the aluminum industry to reduce its energy consumption through recycling. ii) Drastic changes in ELV management practices are necessary to make use of the growing scrap flow in the future, including further dismantling and efficient component-to-component recycling, alloy sorting of mixed shredded scrap, and designing recycling-friendly alloys that function as alternative sinks for aluminum scrap. iii) Light-weighting has the potential to substantially reduce global emissions of vehicles (9-18 gigatons cumulative CO2-eq. between 2010 and 2050). In the medium term (5-15 years), global emissions reductions from substituting standard steel with aluminum are similar to those achievable by HSS; however, over a longer term (after 15-20 years), substitution with aluminum can reduce total emissions more effectively, provided that the wrought aluminum will be recycled back into automotive wrought aluminum. The environmental consequences of products in general and passenger cars in particular have led to an increasing awareness of the dependencies between the shaping of vehicles and the shaping of the environment. Governments and intergovernmental bodies have formulated quality goals for the environment, such as the 2-degree target, and have introduced emissions standards, thereby extending the responsibility of automobile manufacturers to the use phase. On the materials side, legislation has been introduced to extend producer responsibility, mainly with the goal of avoiding toxic substances and reducing the amount of waste, as is noted in different end-of-life vehicle (ELV) legislation and directives. The current ELV directives do not sufficiently address the management of material systems as a whole or quality issues related to material recovery. To harmonize ELV management with goals for the global aluminum cycle and its impacts for the environment, it is essential to understand how the above-mentioned systems interact. Has parts Paper 1: Modaresi, Roja; Müller, Daniel B.. The Role of Automobiles for the Future of Aluminum Recycling. Environmental Science and Technology 2012 ;Volum 46.(16) s. 8587-8594 http://dx.doi.org/10.1021/es300648w Copyright © 2012 American Chemical Society Paper 2: Rombach, Georg; Modaresi, Roja; Müller, Daniel B.. Aluminium Recycling- Raw Material Supply from a Volume and Quality Constraint System. World of Metallurgy - ERZMETALL 2012 ;Volum 65.(3) s. 157-162 Paper 3: Modaresi, Roja; Løvik, Amund Nordli; Müller, Daniel Beat. Component- and Alloy-Specific Modeling for Evaluating Aluminum Recycling Strategies for Vehicles. JOM: The Member Journal of TMS 2014 ;Volum 66.(11) s. 2262-2271., The article is not included due to copyright available at http://dx.doi.org/10.1007/s11837-014-0900-8 Paper 4: Løvik, Amund Nordli; Modaresi, Roja; Müller, Daniel Beat. Long-term strategies for increased recycling of automotive aluminum and its alloying elements. Environmental Science and Technology 2014 ;Volum 48.(8) s. 4257-4265 http://dx.doi.org/10.1021/es405604g Copyright © 2014 American Chemical Society Paper 5: Modaresi, Roja; Pauliuk, Stefan; Løvik, Amund Nordli; Müller, Daniel Beat. Global Carbon Benefits of Material Substitution in Passenger Cars until 2050 and the Impact on the Steel and Aluminum Industries. Environmental Science and Technology 2014 ;Volum 48. s. 10776-10784 http://dx.doi.org/10.1021/es502930w Copyright © 2014 American Chemical Society Publisher NTNU Series Doctoral thesis at NTNU;2015:11
Mechanobiologically-activated, scaffold-free transplantation of stem cells to repair injured cardiac tissues
No full textStatement of Purpose: Stem cell-based therapies represent a valid approach to restore cardiac function due to their beneficial effect in reducing scar area formation and promoting angiogenesis. However, their translation into the clinic is limited by the poor differentiation and inability to secrete sufficient therapeutic factors. To address this issue, several strategies such as genetic modification and biophysical pre-conditioning have been used to enhance the efficacy of stem cells for cardiac tissue repair
Fabrication of a Double-Cross-Linked Interpenetrating Polymeric Network (IPN) Hydrogel Surface Modified with Polydopamine to Modulate the Osteogenic Differentiation of Adipose-Derived Stem Cells
No full textHydrogel surface properties can be modified to form bioactive interfaces to modulate the osteogenic differentiation of stem cells. In this work, a hydrogel made of gelatin methacrylamide (GelMA) and alginate was designed and tested as a scaffold to control stem-cell osteogenic differentiation. The hydrogel's surface was treated with polydopamine (pDA) to create an adhesive layer for the adsorption of the osteoinductive drug dexamethasone (Dex). The presence of the pDA coating enhanced Dex adsorption and retention over 21 days. This effect resulted in a delay in the osteogenic differentiation of hASCs cultured on the hydrogel treated with a pDA layer
Diffusive author(s), cohesive author: Analysis of S/N (1994)
No full textThis study indicates the ways in which various aspects of the author(s) are brought forth in Dumb type’s performance art, the S/N production. Previous research has suggested a non-hierarchical organization of Dumb type and the absence of a “privileged author” in Dumb type’s collaborative work, S/N. However, the results that I have investigated from member’s interviews on the creative process of S/N along with my analysis of the recorded images of S/N, indicate a different aspect of the author(s). First, S/N was created through, so to speak, the collective ideas of the members of Dumb type. Further, S/N has at least nine quotations from previous performances, installations, and printed writings, besides the work-in-progress technique. Explicating one of the “author functions” as given by Michel Foucault, each text has plural subjects of the author. However, it has been revealed from members’ interviews that Teiji Furuhashi had a decision-making role in selecting the members’ ideas within the performance. Since then, S/N has had plural subjects of creation; however, Furuhashi is one of the subjects of creation along with the “privileged author.” S/N has plural authors (diffusive authors) yet at the same time, it has a “privileged author,” Teiji Furuhashi (cohesive author)
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Pre-Conditioning Stem Cells in a Biomimetic Environment for Enhanced Cardiac Tissue Repair: In Vitro and In Vivo Analysis
No full textIntroduction: Stem cell-based therapies represent a valid approach to restore cardiac function due to their beneficial effect in reducing scar area formation and promoting angiogenesis. However, their translation into the clinic is limited by the poor differentiation and inability to secrete sufficient therapeutic factors. To address this issue, several strategies such as genetic modification and biophysical pre-conditioning have been used to enhance the efficacy of stem cells for cardiac tissue repair. Methods: In this study, a biomimetic approach was used to mimic the natural mechanical stimulation of the myocardium tissue. Specifically, human adipose-derived stem cells (hASCs) were cultured on a thin gelatin methacrylamide (GelMA) hydrogel disc and placed on top of a beating cardiomyocyte layer. qPCR studies and metatranscriptomic analysis of hASCs gene expression were investigated to confirm the correlation between mechanical stimuli and cardiomyogenic differentiation. In vivo intramyocardial delivery of pre-conditioned hASCs was carried out to evaluate their efficacy to restore cardiac function in mice hearts post-myocardial infarction. Results: The cyclic strain generated by cardiomyocytes significantly upregulated the expression of both mechanotransduction and cardiomyogenic genes in hASCs as compared to the static control group. The inherent angiogenic secretion profile of hASCs was not hindered by the mechanical stimulation provided by the designed biomimetic system. Finally, in vivo analysis confirmed the regenerative potential of the pre-conditioned hASCs by displaying a significant improvement in cardiac function and enhanced angiogenesis in the peri-infarct region. Conclusion: Overall, these findings indicate that cyclic strain provided by the designed biomimetic system is an essential stimulant for hASCs cardiomyogenic differentiation, and therefore can be a potential solution to improve stem-cell based efficacy for cardiovascular repair
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