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The core mass function in the galactic center
(2024) Kinman, Alva; Chalmers tekniska högskola / Institutionen för rymd-, geo- och miljövetenskap; Chalmers University of Technology / Department of Space, Earth and Environment; Tan, Jonathan; Petkova, Maya
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Catalytic Activity of α-Synuclein Amyloid Fibers
(2024) Rehnberg, Nikita; Chalmers tekniska högskola / Institutionen för life sciences; Chalmers University of Technology / Department of Life Sciences; Wittung-Stafshede, Pernilla; Horvath, Istvan
Amyloid fibers play a significant role in neurodegenerative diseases such as Alzheimer’s Disease (AD) and Parkinson’s Disease (PD). They have for long been considered nonreactive dead-end products of protein aggregation. Recent research show that amyloid fibers, but not monomers, exhibit enzymatic catalytic activity in vitro. This project investigates the catalytic activity of α-Synuclein (aS) amyloid fibers. First, homogeneous aS amyloid fibers were made in a two-step seeding process and amyloids confirmed through ThT-fluorescence, far UV circular dichroism (CD) and atomic force microscopy (AFM). Then, an already established esterase activity assay, in vitro, was used to study ester bond cleavage of WT and A53T (disease-causing mutant) aS amyloid fibers. Another in vitro enzymatic assay was developed to study ATPase activity of WT, A53T and H50A (model of disease-causing mutants with altered residue 50) aS amyloid fibers. Results indicate that there is catalytic activity when aS amyloid fibers are incubated with both ester-bond and ATP substrates. However, the results are only qualitatively interpreted due to large variability in obtained kinetic parameters. To draw firm conclusions regarding the difference between the investigated aS mutants, additional experiments are needed.
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Characterisation of Recycled Plastics for Automotive Radar Applications at 77 GHz
(2023) Nourjoo, Mohammad; Ameerudeen, Mohamed Azad; Chalmers tekniska högskola / Institutionen för mikroteknologi och nanovetenskap (MC2); Chalmers University of Technology / Department of Microtechnology and Nanoscience (MC2); Stake, Jan; Bevilacqua, Stella
This work investigates the potential of various recycled plastic materials for use in bumper areas which are in closer proximity to automotive radar systems operating at 77 GHz. The study focuses on both experimental and analytical calculation approaches to assess the electromagnetic properties of these materials, specifically focusing on their complex permittivity and loss tangent characteristics at 77 GHz. For this purpose, a quasi-optical measurement setup which utilises metallic reflective mirrors to narrow and collimate the beam of waves produced by WR12 frequency extenders in the 65-90 GHz range is used. The S-parameters measured by the Vector Network Analyzer (VNA) of the samples are utilised to calculate the complex refractive index. This procedure allows for the determination of the permittivity and loss tangent for each specific sample material. To ensure the robustness of the calculation method, the known permittivity and loss tangent values at 77 GHz from a reference non-recycled material provided by the supplier are utilised to calculate theoretical S-parameters, which are then employed in the same method to re-evaluate the permittivity and loss tangent. This process enables a direct comparison with the initial VNA-derived results. This round-trip verification process confirms the reliability of the calculation method used in the analysis. From the analysis of all test materials, a particular recycled plastic material is chosen, suggesting its potential suitability for use in automotive bumper production. Overall, this research offers significant insights into the development of radar-compatible recycled plastics for bumper design and manufacturing.
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Cyclic carbonates as green reactants for improving thermoplastic properties of lignocellulosic materials
(2023) Tansatien, Rattanapon; Chalmers tekniska högskola / Institutionen för kemi och kemiteknik; Chalmers University of Technology / Department of Chemistry and Chemical Engineering; Larsson, Anette; Henrik-Klemens, Åke; Jonasson, Katarina
Lignocellulosic materials are attractive raw materials for producing thermoplastics with more sustainable manufacturing. They come from a renewable source that can reduce the dependency on conventional fossil-based feedstock and has good tensile properties. However, their polymeric chains have poor mobility because of the multiple hydrogen bonds of their hydroxyl groups, which is an essential obstacle for thermoplastic processing. To improve their thermoplasticity, their hydroxyl groups can be converted by chemical modifications that introduce the side groups that can increase the flowability of their chains. In this study, unbleached softwood kraft pulp was oxyalkylated with cyclic carbonates (propylene carbonate and ethylene carbonate), acting as a reactant and medium. These two reactants create low environmental impacts because of their biodegradability and low toxicity. In addition, they are also safer compounds from their high boiling point, flash point, and vapor pressure. The influence of temperature, catalysts, and reaction time were investigated. The molecular structures, purity, and thermal properties of the modified products were also evaluated. The chemical modification with ethylene carbonate provides the highest yields and appears to be the most effective pathway to substitute hydroxyl groups with the alkyl side chains. In addition, the products from the chemical modifications with ethylene carbonate have a higher purity and are easier to separate than the products from the chemical modifications with propylene carbonate. Increasing the temperature and amount of catalyst promotes the substitutions on the hydroxyl group. Finally, the modified pulp from chemical modification with ethylene carbonate at a higher temperature and amount of catalyst has better thermal properties than the unmodified pulp. The glass-transition temperature (Tg) of the modified pulp can be detected at approximately 180 °C while the Tg of its raw material is above 220 °C, so the polymeric chains of modified pulp become more flowable.
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In situ synthesis of gold nanorods on SiO₂-substrates
(2023) Wilson, Sean; Chalmers tekniska högskola / Institutionen för kemi och kemiteknik; Chalmers University of Technology / Department of Chemistry and Chemical Engineering; Andersson, Martin; Hulander, Mats; Uusitalo, Maja
The implantation of a medical device introduces a high risk of infection and bacterial biofilm formation on the device surface. These biomaterials-associated infections (BAI) are difficult to treat using conventional methods, such as high dosages of antibiotic treatments, as the bacteria are protected by the biofilm. A promising treatment is to modify the implant surfaces with gold nanorods, which can photothermally eradicate bacteria beneath the biofilm with heat generated from localized surface plasmon resonance (LSPR). As such there is a need to develop methods that reliably produce gold nanorods of a size that produces LSPR at wavelengths within the biological window and that stably bind the particles to the material surface homogeneously. In this thesis, a method has been developed to grow gold nanorods in situ on SiO2-glass and silicon wafers by binding gold nanoparticle seeds to surfaces using (3-Mercaptopropyl)- trimethoxysilane (MPTMS) as a linking molecule. The seeds were then grown into rods using a modified growth solution. The method has also been adapted to surface sensitive analysis to demonstrate the increased possibility to study anisotropic nanoparticles this method brings. In situ quartz crystal microbalance (QCM-D) analysis was used to study the formation of the self-assembled monolayer of MPTMS, the chemisorption of gold nanoparticle seeds, and how the growth rates of the particles vary over time, possibly due to both their increasing size as well as variations in solution concentrations. The developed method produced nanorods with a demonstrated rod yield of ~69% directly on SiO2-glass surfaces. The rods had an aspect ratio (AR) that could be customised to tune the wavelength of LSPR. The ability to tune the optical properties of the rods could allow this method to be used to grow gold nanorods for other applications, such as sensing, as well. Here the tuning was used to demonstrate the effect of silver ions within the growth solution and to produce nanorods with LSPR at the near infrared (NIR) wavelength of ~800nm in the biological window.