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Characterization of the antibacterial properties of human amyloid proteins and antimicrobial peptides based on bacterial membrane-binding domains.
(2023) Qvist, August; Chalmers tekniska högskola / Institutionen för life sciences; Chalmers University of Technology / Department of Life Sciences; Wenzel, Michaela; Wenzel, Michaela
Antibiotic resistance is one of the largest current threats to public health and food security, being directly responsible for 1.27 million deaths worldwide in 2019 and is estimated to rise to 10 million deaths per year by 2050. Therefore, there is an urgent need to find new treatments against resistant infections. This can be done by finding new antibiotic compounds with new mechanisms of action or through optimizing and potentiating existing antibiotics. The antimicrobial mechanisms of action for the human proteins S100A12 and α-synuclein, and 18 peptides derived from peripheral membrane proteins of Mycobacterium tuberculosis were investigated. Antimicrobial activity of each protein and peptide was assayed by determining the minimal inhibitory concentration (MIC). The 18 peptides derived from M. tuberculosis were screened for outer membrane permeabilization effects on Gram-negative bacteria (Escherichia coli) and mycobacteria (Mycolicibacterium smegmatis and Mycobacterium marinum) using the fluorescence probe 1-N-phenylnaphtylamine (NPN). The NPN assay was adapted from the E. coli protocol and investigated for use in mycobacteria. The fluorescent probe 3,3′- dipropylthiadicarbocyanine (DiSC35) was used in a single cell fluorescence microscopy assay to investigate effects on membrane polarization, which can indicate activity toward the plasma membrane. To determine the resistance frequency of the peptides a disk diffusion assay was used. The disk diffusion plates were checked for colonies inside of the inhibition zone after 24 and 48 hours. For S100A12 and α-synuclein-treated Bacillus subtilis grown in a minimal medium, no MIC or significant change in growth could be observed at the tested concentrations. Addition of calcium ions or copper ions to the proteins did not change the growth or MIC. This suggests that these proteins do not have any antimicrobial effect on B. subtilis under the tested conditions. However, some older batches of the S100A12 protein showed a decrease in growth rate suggesting some antimicrobial activity, likely caused by a degradation product or toxic oligomer formation. The antimicrobial activity of the OMPPs ranged from no activity to relatively high activity. The NPN assay in E. coli showed that out of the eighteen peptides, six showed no outer membrane permeabilization, and six peptides showed outer membrane permeabilization of 20% or higher at 10 μg/ml. With the DiSC35 assay, treating E. coli with the peptides for 15 minutes before imaging, an increase in fluorescence emission could be seen for the peptides that also showed a higher outer membrane permeabilization. However, no significant change in fluorescence of the dye could be seen for most peptides. The increased fluorescence of DiSC35 is likely caused by an increase in uptake of the dye due to increased permeability of the outer membrane. The disk diffusion assay showed no colonies within the inhibition zone after 24 or 48 hours indicating low frequency of resistance development towards the peptides. The collective results of the screenings in E. coli showed that two peptides may be selective outer membrane permeabilizers and should be investigated further at different concentrations. The rest of the peptides showed other or unspecific modes of action that may be of interest as antimicrobials and should also be investigated further. In mycobacteria, using NPN to assess outer membrane permeabilization needs to be further developed and optimized to produce proper results, as no reliable positive control is known. Further assays should be used to evaluate the activity of these peptides in mycobacteria.
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Effect of rheology and crystallinity on processing and barrier properties of PHA
(2023) Siva Kumar, Amit Kumar; Chalmers tekniska högskola / Institutionen för industri- och materialvetenskap; Chalmers University of Technology / Department of Industrial and Materials Science; Kádár, Roland; Kádár, Roland
Plastic pollution is one of the major problems that the world is facing at present. Different industrial sectors contribute to this and the packaging sector is one of the main contributors. According to the statistics, the packaging sector alone contributes to 60% of the total plastic pollution. This creates the need for the packaging industry to become more sustainable and produce more environmentally friendly products. There are various types of packaging products and this thesis is focused on food packaging. In food packaging a plastic layer is used to act as a barrier against, for example, gases, such as oxygen and carbon dioxide, and sunlight, as these can decrease the shelf life of the packaged food. However, the plastic film is produced from fossil-based resources and is not biodegradable. The replacement of the conventional plastic barriers with a bio-based polymer is one possible solution to move towards more sustainable packaging materials. For this purpose, a class of bio-based polymers named polyhydroxyalkanoates (PHAs) have been studied in this project. Four different types of PHAs have been characterized using techniques such as DSC, TGA, and DMA, among others. Rheological characteristics were also studied to improve the PHA processing and coating onto paperboard at a pilot scale. Additionally, water vapor barrier properties of the different PHA samples and PHA-coated paperboard were measured and the effect of PHA molecular weight and crystallinity on these was also assessed. From this study, it was observed that PHA with higher molecular weight showed better performance in terms of mechanical properties and barrier properties. Moreover, PHA crystallinity has also been shown to play an important role in terms of barrier properties alongside molecular weight. Regarding rheological properties, it was verified that PHA with higher molecular weight has higher melt viscosity, which makes the material stable at higher temperatures but at the same time, hinders the production of proper coating onto the paper-board. For a better understanding of how PHA processing through extrusion coating can be improved in practice, further studies are required, for instance, the change of processing parameters and the compounding of PHA with other components/ polymers.
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Wear characteristics of normal compressive crushing rings
(2023) Babaahmadi, Ahmadreza; Chalmers tekniska högskola / Institutionen för industri- och materialvetenskap; Chalmers University of Technology / Department of Industrial and Materials Science; Cao, Emmy Yu; Cao, Emmy Yu; Evertsson, Magnus
This thesis examines the wear characteristics of a promising new rock-crushing technology. This novel method employs a normal compressive force to comminute rocks between two rotating rings. To further understand the wear mechanism of these rings and the ring materials response to this type of wear, a variety of ring materials, including Hardox600, two types of sintered Tungsten Carbide (WC)/Cobalt (Co) matrix, identified as X1 and X2 - where X1 has less WC compared to X2 was used. This range of materials enabled a comparative study of wear patterns under the same operating conditions. The thesis was carried out through a set of surface studies using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), and Backscatter Electron (BE) imaging. These tools were used to closely examine the worn features on the surfaces of the tested materials. These detailed methods provided a clear view of wear patterns, enabling a better understanding of how the ring materials behave during rock crushing. After a comprehensive analysis of the crushing principle and surface wear, the high stress three-body abrasive wear was identified as the primary wear mode for this application. In response to this type of wear, the tested materials displayed contrasting material removal mechanisms. Hardox600, being the softest of the materials, primarily experienced cutting (Ploughing) and repeated plastic deformations, evidenced by slivers on the worn surface. Conversely, the sintered WC materials exhibited completely different post-wear surface topography. For these materials, most material removal was due to WC particle breakage and subsequent dislodging from the matrix. Of the two sintered materials tested, the one with a higher WC content percentage demonstrated superior wear resistance, underscoring the significance of hardness in relation to the hardness of the abrasives. The superior wear can also be explained by the smaller and more uniform WC used in the Sintered X2 compared to X1. Based on the wear resistance and hardness of the evaluated materials, we conclude that for optimal wear resistance in this wear application, materials should resist plastic deformation, as it leads to severe wear. To control wear, materials should have a hardness that is on par with that of the abrasives to minimize the severity of wear.
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Kartläggning och energieffektivisering vid renovering av byggnadskonstruktion från Miljonprogrammet
(2023) Bergsten, Axel; Muziramaj, Jetmir; Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Adl-Zarrabi, Bijan; Sasic Kalagasidis, Angela
Ambitionen för energieffektivisering har ökat de senaste åren inom Sverige och i EU-länder. Sverige och andra EU-länder har satt höga mål att reducera sina totala utsläppsnivåer och reducera energianvändningen i bostadsbeståndet. För att minska energiförbrukningen och därmed också bidra till minskad miljöpåverkan är energieffektivisering av flerbostadshus en viktig del i helheten för unionen. Syftet med denna studie var att undersöka ett flerbostadshus som är i behov av renovering. Byggnaden är från miljonprogrammet och studien ska kartlägga nuvarande energiprestanda samt föreslå åtgärder för energieffektivisering. Studien började med platsbesök för att undersöka renoveringsbehovet på flera byggnader från miljonprogrammet samt för att välja ett referensobjekt. Därefter genomfördes följande metoder: litteraturstudier, numeriska och analytisk modellering för att kartlägga byggnadens nuvarande energiförbrukning. Utifrån dessa metoder antogs förslag på åtgärder på hur man kan sänka byggnadens uppvärmningsbehov. Med fokus på energieffektivisering föreslogs olika åtgärder. Förarbeten avgränsade utifrån att man studerade klimatskal, ventilation och tätheten i konstruktionen. Den projekterade energieffektiviseringen presenteras i form av tre olika åtgärdsförslag. En energikartläggning utfördes av det valda referensobjektet för att jämföra med och mellan de olika åtgärdsförslag. Nästa steg var att ta reda på energibesparingar från de tre olika åtgärdsförslag genom att utföra beräkningar för byggnadens värmeenergibehov. Därefter beräknades all värme som tillförs och bortförs från byggnaden och sedan uppskattades effekt och energibehovet för uppvärmningen. I slutet gjordes en BIM-energiberäkning vilken användes för att jämföra med den befintliga förbrukningen och med beräkningarna. Slutsatsen är att åtgärdsförslag erbjuder bra alternativ och resultat. Ytterligare åtgärder föreslås för att nå ett optimalt resultat i syfte att energieffektivisera byggnaden. Där målet för ytterligare åtgärder är att reducera energibehovet för uppvärmning av fastigheten, minska miljöpåverkan och bidra till en hållbar framtid.
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Evaluating concepts for automated tool handling
(2023) Abbas, Hussein; Broström Vedin, Albin; Chalmers tekniska högskola / Institutionen för industri- och materialvetenskap; Chalmers University of Technology / Department of Industrial and Materials Science; Skoogh, Anders; Skoogh, Anders
Production of aircraft parts undergoes processes where tough materials are pro cessed with high-quality requirements. Today’s increased demand for production places higher demands on the tool handling that exists within these productions, which leads to the purpose of this report. The master thesis has been carried out to see if there are other methods to improve tool handling within a part of production at GKN Aerospace. The work was carried out with a background study where important data collection was acquired to then use a simulation tool to see possible results. The background study showed that automated solutions were of interest as they can increase accu racy and productivity. The execution of these months of work has led to the conclusion that automated solutions can be beneficial. The simulation has given results such as increased productivity, reduced costs, and improved ergonomics, but also how good results a simulation tool can provide to test possible and new solutions.