| 1. |
- Cai, Yixiao, 1986-
(författare)
-
Bio-Nano Interactions : Synthesis, Functionalization and Characterization of Biomaterial Interfaces
- 2016
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Current strategies for designing biomaterials involve creating materials and interfaces that interact with biomolecules, cells and tissues. This thesis aims to investigate several bioactive surfaces, such as nanocrystalline diamond (NCD), hydroxyapatite (HA) and single crystalline titanium dioxide, in terms of material synthesis, surface functionalization and characterization.Although cochlear implants (CIs) have been proven to be clinically successful, the efficiency of these implants still needs to be improved. A CI typically only has 12-20 electrodes while the ear has approximately 3400 inner hair cells. A type of micro-textured NCD surface that consists of micrometre-sized nail-head-shaped pillars was fabricated. Auditory neurons showed a strong affinity for the surface of the NCD pillars, and the technique could be used for neural guidance and to increase the number of stimulation points, leading to CIs with improved performance.Typical transparent ceramics are fabricated using pressure-assisted sintering techniques. However, the development of a simple energy-efficient production method remains a challenge. A simple approach to fabricating translucent nano-ceramics was developed by controlling the morphology of the starting ceramic particles. Translucent nano-ceramics, including HA and strontium substituted HA, could be produced via a simple filtration process followed by pressure-less sintering. Furthermore, the application of such materials as a window material was investigated. The results show that MC3T3 cells could be observed through the translucent HA ceramic for up to 7 days. The living fluorescent staining confirmed that the MC3T3 cells were visible throughout the culture period.Single crystalline rutile possesses in vitro bioactivity, and the crystalline direction affects HA formation. The HA growth on (001), (100) and (110) faces was investigated in a simulated body fluid in the presence of fibronectin (FN) via two different processes. The HA layers on each face were analysed using different characterization techniques, revealing that the interfacial energies could be altered by the pre-adsorbed FN, which influenced HA formation.In summary, micro textured NCD, and translucent HA and FN functionalized single crystalline rutile, and their interactions with cells and biomimetic HA were studied. The results showed that controlled surface properties are important for enhancing a material’s biological performance.
|
|
| 2. |
- Dandan, Kinan, 1976-
(författare)
-
Enabling Surface Cleaning Robot for Large Food Silo
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Working conditions in the dry cleaning and sanitation of confined interior spaces are often extreme, and workers need overall protection with tight clothing, helmets, face mask, earmuffs, and respirators. The environment is dirty, noisy with bad visibility and heavy with a high static work load. Dry cleaning is mainly practised in silos for grain, foodstuff and flour, etc. The inside of the silo is a hazardous environment due to many factors such as an unsafe oxygen level, engulfment, biological, mechanical, electrical, and atmospheric hazards. The requirements of the EU norms related to hygiene and food quality indicate that silos should be cleaned frequently and cleaning is obligatory after a silo is totally emptied. Therefore, there is an increased societal need for silo cleaning and a natural necessity to replace humans by robot manipulators in executing this risky and dangerous job.This thesis presents a new concept of a flexible crawling mechanism for an industrial food cleaning robot, which is evaluated from the viewpoint of the capability to work inside a large food silo, scanning the desired surface, and performing the cleaning task. The main research questions investigated in this thesis are about: how to select the most important characteristics in designing a robot to fulfil the surface cleaning operation of a large confined space; how the crawling movement affects the dynamic behaviour of the robot mechanism; how the cleaning process affects the dynamic behaviour of the robot mechanism; how to develop the control of the robot to realize the locomotion and the cleaning process.The structure of the robot and the cleaning technology are well defined after an overview of the existing technologies and solutions for cleaning large confined spaces. The robot design is based on a suspension and crawling system, using minimal actuators, where the force of gravity is well used to simplify the control system and to stabilise the robot. Further, the static and dynamic analysis of the mechanical system is studied. In addition, the control architecture of the system is performed, where the required sensors and control algorithm are given. A scale model testing has also been used to verify the locomotion of the concept, while simple controllers and algorithms are used to manage the motions of the prototype.
|
|
| 3. |
- Börjeson, Natasja
(författare)
-
Toxic Textiles : Towards Responsibility in Complex Supply Chains
- 2017
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The governance of the environmental and health problems that follow in the wake of globalised trade is one of the great contemporary challenges. One of these challenges is the management of chemical pollution and associated risks, and one sector facing this challenge is the textile industry, which has complex supply chains spread across continents. At the same time the role of actors on the playing field are changing and market actors are being called on to responsibly manage the issue of chemical risks and associated challenges. However, governance and control are often obstructed due to complexity and considerable knowledge uncertainty. This situation complicates responsibility-taking and makes it difficult to ascribe liabilities to specific actors, as it is not obvious who is responsible for what. This thesis is concerned with the process of how a group of market actors – private and public textile buyers – assume responsibility of chemical risks in their supply chains in a situation that is characterized by uncertainty and complexity. This thesis aims to contribute to an understanding of what happens when market actors are called on to manage the negative side effects of globalisation. The focus is on Swedish textile-buying private and public organisations. The thesis constructs an analytical model based on the key concepts responsible governance, responsibilisation, and responsible supply chain management (RSCM). The thesis explores the barriers, challenges and opportunities that exist for buyers seeking to assume RSCM and whether a process of responsibilisation can be observed in the textile sector. The thesis uses an exploratory approach and interviews, participatory observations and literature studies, as well as case studies to understand the process and to investigate barriers, challenges, opportunities. In summary, the thesis shows that a process of responsibilisation is ongoing on the organisational and sector levels. Further, it is shown that due to the complex structures of the chains, there are more barriers and challenges than opportunities for buyers striving for RSCM. However, it is argued that cooperation, stronger public and private policy, and a reflexive approach could be ways forward towards RSCM and increased responsibilisation in the textile sector.
|
|
| 4. |
- Karlsson, Joakim, 1984-
(författare)
-
Optimization of Electron Beam Melting for Production of Small Components in Biocompatible Titanium Grades
- 2015
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Additive manufacturing (AM), also called 3D-printing, are technologies where parts are formed from the bottom up by adding material layer-by-layer on top of each other. Electron Beam Melting (EBM) is an AM technique capable of manufacturing fully solid metallic parts, using a high-intensity electron beam to melt powder particles in layers to form finished components. Compared to conventional machining, EBM offers enhanced efficiency for production of customized and patient specific parts such as e.g. dental prosthetics. However, dental prosthetics are challenging to produce by EBM, as their small sizes mean that mechanical and surface properties may be altered as part sizes decreases.The aim of this thesis is to gain new insights that could lead to optimization for production of small sized components in the EBM. The work is focused to understand the process-property relationships for small size components production.To improve the surface resolution and part detailing, a smaller sized powder was used for production and compared to parts made with standard sized powder. The surface-, chemical and mechanical properties were evaluated for parts produced with both types of powders. The results indicate that the surface roughness may be influenced by powder and build layer thickness size, whereas the mechanical properties showed no influence of the layer-wise production. However, the mechanical properties are dependent on part size. The outermost surface of the parts consists of a surface oxide dominated by TiO2, formed as a result of reaction between the surface and residual gases in the EBM build chamber. The surface oxide thickness is comparable to that of a conventionally machined surface, but is dependent on build height.This work concludes that the surface resolution and component detailing can be improved by various measures. Provided that proper process themes are used, the EBM manufactured material is homogenous with properties comparable to conventional produced titanium. It has also been shown that the material properties will be altered for small components. The results point towards different ways of optimizing manufacturing of dental prosthetics by EBM, which will make dental prosthetics available for an increased number of patients.
|
|
| 5. |
- Kolan, Shrikant S, 1983-
(författare)
-
Defining the role of CD47 and SIRPα in murine B cell homeostasis
- 2015
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- B cell development is a highly organized process, which commences in the fetal liver during embryogenesis and in the bone marrow (BM) after birth. Surface IgM+ immature B cells emigrate from the BM via the blood stream to the spleen and finally differentiate into conventional mature follicular B (FoB) cells and marginal zone (MZ) B cells. Conversely, some sIgM+ immature B cells can also mature into IgD+ FoB cells in the BM.The ubiquitously expressed cell surface glycoprotein CD47 and its receptor signal regulatory protein α (SIRPα) are members of the immunoglobulin superfamily. Both individually and upon their interaction, CD47 and SIRPα have been found to play important role in the homeostasis of T lymphocytes or CD8 conventional dendritic cells (cDCs) in secondary lymphoid organs. However, their role in regulating B cell homeostasis has remained unknown.The present study describes important roles of CD47 and SIRPα in B cell homeostasis. Lack of SIRPα signaling in adult SIRPα mutant (MT - cytoplasmic domain deletion) mice resulted in an impaired B cell maturation in the BM and spleen, which was also reflected in the blood. In the BM and spleen of SIRPα MT mice, reduced numbers of semi-mature IgD+IgMhi follicular type-II (F-II) and mature IgD+IgMlo follicular type-I (F-I) B cells were observed, while earlier BM B cell progenitors or splenic transitional B cells remained unaltered. In SIRPα MT mice, maturing B cells in BM and spleen were found to express higher levels of the pro-apoptotic protein BIM and contained an increased level of apoptotic cells.In contrast to that for FoB cells, the splenic MZ B cell population was increased with age in SIRPα MT mice without showing an increased level of activation markers. Immunohistochemical analysis revealed an increased follicular localization of MZ B cells in the spleens of SIRPα MT mice. In addition, MZ macrophages and marginal metallophilic macrophages were not restricted to their normal position in SIRPα MT spleens. Interestingly, CD47-deficient (CD47-/-) mice mimicked the FoB cell phenotype observed in SIRPα MT mice and had a reduced number of FoB cells in the BM, blood and the spleen at 56 months of age, but not in younger mice. Similar to SIRPα MT mice, CD47-/- mice also displayed an increased number of splenic MZ B cells. Sera form both mouse strains did not show any signs of an increased production of autoantibodies or antinuclear antigens.BM reconstitution experiments identified a requirement for non-hematopoietic SIRPα signaling for normal B cell maturation in the BM and to maintain normal numbers and retention of MZ B cells in the splenic MZ. On the contrary, hematopoietic SIRPα signaling appeared to be important for FoB cell maturation in the spleen. Interestingly, hematopoietic SIRPα was required for normal MZ retention of MZ macrophages while normal distribution of metallophilic macrophages required nonhematopoietic SIRPα signaling. Collectively, these findings revealed an important role of CD47 and of SIRPα signaling in B cell homeostasis in different lymphoid organs.
|
|
| 6. |
- Majal, Ghulam, 1991-
(författare)
-
On the Agglomeration of Particles in Exhaust Gases
- 2018
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Particulate emissions from road transportation are known to have an adverse impact on human health as well the environment. As the effects become more palpable, stricter legislation have been proposed by regulating bodies. This puts forward a challenge for the automotive industry to develop after treatment technologies to fulfil the progressively stricter legislation. At present, the most common after-treatment technologies used for particulates are the diesel and gasoline particulate filters. The typical size distribution of the particles is such that the smallest particles in terms of size are in numbers the largest, although they are not influencing the total particle mass significantly. The most recent legislation have included restrictions on the particle number as well as particle mass. In this thesis numerical tools for studying the transport and interaction of particles in an exhaust flow are evaluated. The specific application is particle agglomeration as a mean to reduce the number of particles and manipulate the size distribution. As particles agglomerate the particle number distribution is shifted and larger sized agglomerates of particles are created reducing the number of ultra-fine particles. The particle agglomeration is obtained by forcing sudden acceleration and deceleration of the host gas carrying the particles by variations in the cross sectional areas of the geometry it is passing through. Initially, a simplified one dimensional model is utilized to assess the governing parameters of particle grouping. Grouping here means that the particles form and are transported in groups, thus increasing the probability for agglomeration. The lessons learned from the 1D-model are also used to design the three dimensional geometry: an axisymmetric corrugated pipe. Two different geometries are studied, they both have the same main pipe diameter but different diameter on the corrugations. The purpose is to find the potential onset of flow instabilities and the influence of 3D-effects such as recirculation on the agglomeration. The CFD simulations are performed using DES methodology. First the simulations are run without particles in a non pulsatile flow scenario. Later particles are added to the setup in a one way coupled approach (no particle-particle interaction). The main results were: 1) An additional criterion for grouping to the ones given in previous work on the 1D model is proposed. It is found that grouping is more likely if the combination of the pulse frequency and geometric wavelength is large. Furthermore, smooth pulse forms (modelling the modulation in the flow due to the geometry) yielded more grouping than other more abrupt pulse shapes. However, idealised inlet pulses underestimate the extent of grouping compared to actual engine pulses. 2) For the geometry with larger maximum cross sectional area stronger flow separation was observed along with higher turbulent kinetic energy. 3) Particles were added in the flow field and a reduction in the particle count was observed in the initial simulations for particles going from the first corrugated segment to the last. Natural extensions of the present work would be to consider pulsatile flow scenarios, particle-particle interaction and a polydisperse setup for the particles
|
|
| 7. |
- Vargas Catalan, Ernesto, 1988-
(författare)
-
Microfabrication of Optical Components in Synthetic Diamond : Infrared Optics for Applications in Astronomy and Spectroscopy
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Infrared optics is a broad general term, relevant to a range of fields. The manufactured diamond optical components utilized within this thesis were applied to both astronomy, in which direct imaging of star system using large ground-based telescopes and diamond coronagraphs was performed, and in absorption spectroscopy probing solvents and proteins using a tuneable quantum cascade laser and diamond waveguides.The optical components presented in this thesis are all made from diamond, as it is one of few materials that is transparent in the infrared regime. Furthermore, diamond has other unique properties that include high thermal conductivity, low thermal expansion and chemically inertness. In this thesis synthetic diamond grown by chemical vapor deposition has been used, using commercially available components and equipment.The focus of this thesis was to produce optical gratings for different applications using plasma etching. The first steps involved understanding the etch process and optimizing the plasma etch parameters to enable the fabrication of new types of nano/micro meter sized structures in diamond. Optimization of the etch masks is also included in the work. With this newfound knowledge, deeper and narrower optical gratings than before could be realized.Optical evaluation of the gratings in special designed optical test benches was used to determine the coronagraphic performance of the manufactured diamond coronagraphs. Most often the designed etch depth could not be reached in the first attempt and therefore a post-fabrication method for tuning the etch depth was developed. This showed to be vital to realising high performing diamond coronagraphs. Diamond coronagraphs were also installed in several ground based telescopes and discovery of new astronomical objects are presented. With deeper understanding of the etch process more complex coronagraphs in diamond were manufactured opening up for use in the next generation of giant telescopes.In the second part of this thesis, fabrication of diamond waveguides for sensitive analysis of solvents and proteins using infrared spectroscopy is presented. Different designs of diamond waveguides are demonstrated and initial analysis of organic compounds and glucose using a quantum cascade laser as the light source is presented. This type of biosensor will be used to study the secondary structure of proteins relevant for different diseases.
|
|
