1. Incorporation of recombinant proteins into extracellular vesicles by Lactococcus cremorisTina Vida Plavec, Kristina Žagar, Giulia Della Pelle, Špela Zupančič, Robert Vidmar, Aleš Berlec, 2025, original scientific article Abstract: Extracellular vesicles (EVs) are nanosized lipid bilayer particles released by various cellular organisms that carry an array of bioactive molecules. EVs have diagnostic potential, as they play a role in intercellular interspecies communication, and could be applied in drug delivery. In contrast to mammalian cell-derived EVs, the study of EVs from bacteria, particularly Gram-positive bacteria, received less research attention. This study aimed to investigate the production of EVs by lactic acid bacterium Lactococcus cremoris NZ9000 and to examine the impact of recombinant protein expression on their formation and protein content. Four different recombinant proteins were expressed in L. cremoris NZ9000, in different forms of expression and combinations, and the produced EVs were isolated using the standard ultracentrifugation method. The presence of vesicular structures (50–200 nm) in the samples was confirmed by transmission electron microscopy and by flow cytometry using membrane-specific stain. Mass spectrometry analyses confirmed the presence of recombinant proteins in the EVs fraction, with amounts ranging from 13.17 to 100%, highlighting their significant incorporation into the vesicles, together with intrinsic L. cremoris NZ9000 proteins that were either more abundant in the cytoplasm (ribosomal proteins, metabolic enzymes) or present in the membrane. The presence of the most abundant lactococcal proteins in EVs fraction suggests that protein cargo-loading of EVs in L. cremoris NZ9000 is not regulated. However, our data suggests that L. cremoris NZ9000 genetically engineered to express recombinant proteins can produce EVs containing these proteins in scalable manner. As L. cremoris NZ9000 is considered safe bacterium, EVs from L. cremoris NZ9000 could have several advantages over EVs from other bacteria, implying possible biotechnological applications, e.g. in therapeutic protein delivery.
Keywords: Lactococcus cremoris, extracellular vesicles, recombinant proteins, delivery vehicle
Published in DiRROS: 16.01.2025; Views: 8; Downloads: 4
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2. Corrosion of household mixer headsJaka Burja, 2024, published scientific conference contribution Abstract: Household appliances often utilize polymer-metal bonding, typically achieved through adhesive bonding or press-fitting techniques. Corrosion resistance is a major factor in household appliances, as corrosion can compromise the functionality and aesthetics of household appliances. Stainless steels are a natural choice. However, the nature of polymer-stainless steel bonds can cause susceptibility to crevice corrosion. Crevice corrosion, a localized attack on stainless steel in confined spaces. This study investigates crevice corrosion in mixer heads fabricated with two different grades of stainless steel (1.4016 and 1.4021). Metallographic analysis revealed a ferritic microstructure with higher chromium content for 1.4016, contributing to its superior corrosion resistance compared to the martensitic structure of 1.4021. Both materials exhibited a critical crevice width of 9-10 μm between the plastic head and the steel shaft, facilitating the entrapment of corrosive solutions (confirmed by EDS analysis) and subsequent crevice corrosion. The PREN (pitting resistance equivalent number) calculation further supported the observed behavior, with 1.4016 boasting a higher value (16-18) compared to 1.4021 (12-14). While PREN offers a valuable indicator, it highlights the importance of design considerations to minimize crevice formation. Here, eliminating the gap between plastic and steel through improved design or sealants emerges as a crucial preventive strategy. This study emphasizes the interplay between material selection and design in mitigating crevice corrosion in household appliances. By understanding the factors influencing corrosion susceptibility, manufacturers can optimize material choices and implement design solutions to ensure the longevity and performance of their products.
Keywords: crevice corrosion, stainless steel, mixer heads
Published in DiRROS: 16.01.2025; Views: 14; Downloads: 9
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3. Optimization of partial stainless steel melt oxidation in the EAFAnže Bajželj, Jaka Burja, 2024, published scientific conference contribution Abstract: Stainless steel production typically follows the duplex process, beginning with the electric arc furnace (EAF) and proceeding to the vacuum oxygen decarburizer (VOD) or argon oxygen decarburizer (AOD). The EAF's role is to melt the charge and heat it up for further processing, reducing tap-to-tap times through partial oxidation. However, this partial oxidation in the EAF leads to chromium losses as oxygen interacts with the high chromium steel melt. To address this issue, parameters affecting chromium burn-off have been identified and presented. A primary challenge in EAF steel production with elevated chromium content is to lower carbon levels while maximizing chromium yield in the melt. Unlike VOD and AOD processes, which permit low carbon and high chromium levels through vacuum or argon blowing, the EAF provides limited protection, mainly through silicon. At higher temperatures, carbon oxidation predominates, hence it is important to limit oxygen input into the system in the initial stages, while “protecting” the chromium with silicon. During the oxidation phase of the steel melt, carbon content decreases; however, attention must be paid to ensure that the concentration is not too low, as this increases chromium activity in the melt, leading to more intense oxidation. A practical model, derived from thermodynamic calculations, has been developed to guide carbon, chromium, and other element oxidation during scrap melting. This model, validated through industrial trials, aids in optimizing steel melt oxidation to minimize chromium losses effectively.
Keywords: EAF, stainless steel scrap, carbon oxidation, chromium oxidation, thermodynamics
Published in DiRROS: 16.01.2025; Views: 13; Downloads: 9
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4. AISI H13 tool steel - comparison between powder bed fused and classically produced partsSamo Tome, Irena Paulin, Matjaž Godec, 2024, published scientific conference contribution Abstract: AISI H13 Is very commonly used in the hot-work category of steels. Whether it is used as a forging die, a hotcutting tool, or a mold in injection molding or die casting, it is always on the table, as the material of choice. However, its potential has not yet been fully realized. New manufacturing techniques such as additive manufacturing (AM) broaden the horizon of the material’s application, and promise improved performance, through optimized geometry, unobtainable by traditional means, and heightened mechanical properties. One of the more widespread AM processes is Powder Bed Fusion (PBF) where a laser or electron beam constructs the model, by meting a thin coating of metal powder applied to a base plate. By repeatedly applying and melting powder, the end result is a layer-by-layer produced part. However, the techniques for producing such parts are not yet refined enough and require further research. Problems like porosities, part deflection, and crack formation due to residual stress are commonplace, while comparably low mechanical properties in the asprocessed state call for post-production treatments. Naturally, every technique has its boons and drawbacks, and that is what this work aims to analyze - How do the PBF parts compare to classically produced ones, and what are the difficulties in producing the later-mentioned parts.
Keywords: powder bed fusion, tool steel, additive manufacturing, mechanical properties
Published in DiRROS: 16.01.2025; Views: 13; Downloads: 9
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5. Detecting geodesic circles in hyperbolic surfaces with persistent homologyBlaž Jelenc, Žiga Virk, 2025, original scientific article Abstract: In this paper we provide conditions under which a geodesic circle on a hyperbolic surface admits arbitrarily small geodesically convex neighborhoods. This implies that persistent homology using selective Rips complexes detects the length and the position of such a loop via persistent homology in dimensions one, two, or three. In particular, if a surface has a unique systole, then the systole can always be detected with persistent homology. The existential results of the paper are complemented by the corresponding quantitative treatments which explain the choice of parameters of selective Rips complexes as well as conditions, under which the detection occurs via the standard Rips complexes. In particular, if a surface has a unique systole, then the parameters depend on the first spectral gap in the length spectrum.
Keywords: simple closed geodesic, Rips complexes, persistent homology, hyperbolic surfaces, systole
Published in DiRROS: 15.01.2025; Views: 43; Downloads: 16
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7. Novel methodology of general scaling-approach normalization of impedance parameters of insertion battery electrodes – case study on Ni-rich NMC cathode : Experimental and preliminary analysisMarko Firm, Jože Moškon, Gregor Kapun, Sara Drvarič Talian, Ana Rebeka Kamšek, Mateja Štefančič, Samo B. Hočevar, Robert Dominko, Miran Gaberšček, 2024, original scientific article Published in DiRROS: 14.01.2025; Views: 58; Downloads: 24
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