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Abstract: In this study, the influence of voids on corrosion process at the steel-concrete interface was investigated, as the exact influence of these features on corrosion processes under various environmental conditions is not entirely understood. Coupled multi electrode arrays and electrical resistance probes were implemented to monitor the evolution of corrosion under cyclic exposure to chlorides and carbonation. MicroCT was used to determine the location and volume of corrosion damage. It was found that, in most cases, corrosion damage initiated outside the voids. During initiation and the early propagation phase, the steel beneath the voids rarely participated in the redox reaction. In following phases, various kinds of corrosion evolution were observed. Specific corrosion mechanisms were proposed and discussed to explain these corrosion processes.
Keywords: microtomography, corrosion, coupled multi-electrode array, steel-concrete interface
Published in DiRROS: 06.06.2024; Views: 364; Downloads: 414
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Abstract: The prevalence of bacterial infections presents a significant challenge in the medical field, demanding effective strategies to impede bacterial adhesion and growth on various surfaces. The conducted study investigates the efficacy of polyelectrolyte multilayers─comprising poly(allylamine hydrochloride) (PAH) and alginate (ALG)─embedded with zinc oxide (ZnO) and copper oxide (CuO) nanoparticles (NPs) to inhibit bacterial adhesion on stainless-steel surfaces. Surface characterization involved zeta potential, contact angle, and roughness assessments. The effect of NP composition, size, and morphology in conjunction with polycation or polyanion terminating multilayers was evaluated against planktonic and surface-adhered Escherichia coli (E. coli) cells. Surfaces with the positively charged PAH-terminating multilayer displayed higher water contact angles (≈ 63°) than the negatively charged ALG-terminating multilayers (≈ 45°). Multilayers containing ZnO NPs showed a significant inhibition of planktonic E. coli growth, >99%. Moreover, complete growth inhibition of surface-adhered E. coli was achieved for multilayers containing both ZnO and CuO. Due to their larger specific surface area, rod-like ZnO NPs displayed higher antibacterial activity. The samples with ALG as the terminating layer showed more substantial antibacterial properties than samples with PAH as the terminating layer. Biocompatibility tests on immortalized human keratinocyte cells revealed good compatibility with multilayers incorporating NPs. In summary, this study underscores the potential of ZnO and CuO NPs within PAH/ALG multilayers for antibacterial applications without compromising their cytocompatibility.
Keywords: polyelectrolyte multilayers, alginate, poly(allylamine hydrochloride), CuO, ZnO, nanoparticles, Escherichia coli
Published in DiRROS: 06.06.2024; Views: 399; Downloads: 332
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Abstract: Imunoterapija je preoblikovala zdravljenje metastatskih rakov, saj je izboljšala preživetje in kakovost življenja bolnikov. Kljub temu povzroča imunsko pogojene neželene učinke, ki zahtevajo prekinitev zdravljenja. Njihovo zgodnje odkrivanje je zato ključnega pomena, njihova diagnoza pa temelji predvsem na kliničnih simptomih in laboratorijskih izvidih. Razmah razvoja umetne inteligence v preteklih letih je omogočil bolj kvantitativno analizo 18F-FDG PET/CT slik. Prvi korak, kjer umetna inteligenca pripomore k hitrejši diagnozi imunsko pogojenih neželenih učinkov, so nevronske mreže, razvite za segmentacijo organov na CT-slikah. Uporaba takšnih avtomatskih orodij za segmentacijo organov je hitrejša in bolj natančna v primerjavi z ročno segmentacijo. Omogoča tudi razvoj kvantitativnih slikovnih bioloških označevalcev, izvlečenih iz PET-slik s pomočjo pridobljenih segmentacij, kar je pripomoglo tudi k razmahu razvoja napovednih modelov. V retrospektivni raziskavi, ki je vključevala 58 bolnikov z metastatskim melanomom, so se percentili porazdelitve FDG v ščitnici, črevesju in pljučih izkazali kot orodje za ločevanje med bolniki, ki bodo razvili imunsko pogojene neželene učinke, in tistimi, ki jih ne bodo. Validacija teh kvantitativnih slikovnih bioloških označevalcev (angl. Quantitative Imaging Biomarkers, QIB) za napovedovanje imunsko pogojenih neželenih učinkov trenutno poteka v prospektivni neinterventni klinični raziskavi na Onkološkem inštitutu Ljubljana. Prvi izsledki kažejo, da so razviti označevalci v pomoč klinikom pri zgodnji diagnozi imunsko pogojenih neželenih učinkov, kar omogoči hitrejše ukrepanje pred razvojem kliničnih simptomov, a včasih tudi lažno napovedo možen razvoj neželenih učinkov. Naslednji koraki so razvoj modela za napoved časa razvoja imunsko pogojenih neželenih učinkov, a je za razvoj takšnih modelov potrebno večje število podatkov, za kar so potrebne multicentrične klinične raziskave. 18 Ključne besede: imunoterapija, neželeni učinki, kvantifikacija, FDG-PET/CT, napovedovanje neželenih učinkov, kvantitativni slikovni biološki označevalci
Keywords: metastatski melanom, imunoterapija, neželeni učinki
Published in DiRROS: 06.06.2024; Views: 363; Downloads: 161
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Abstract: We investigated micro-threaded stem taper surface and its impact on premature failures, aseptic loosening, and infection in cementless hip endoprostheses. Our study focused on the fretting, and crevice corrosion of micro-threaded tapers, as well as the characterization of the microstructure and surface properties of two new and three retrieved Zweymüller stem tapers. The retrieved samples were selected and examined based on the head–stem taper interface being the sole source of modularity with a metallic component, specifically between the Ti alloy taper stem and the ceramic head. To determine the surface chemistry and microstructures of both new and retrieved hip endoprostheses stem taper titanium alloy, scanning -electron microscopy (SEM) was employed for morphological and microstructural analyses. Energy dispersive spectroscopy (EDS) was utilized for characterizing chemical element distribution, and electron backscattered diffraction (EBSD) was used for phase analysis. The roughness of the micro-threated stem tapers from different manufacturers was investigated using an optical profilometer, with standard roughness parameters Ra (average surface roughness) and Rz (mean peak to valley height of the roughness profile) being measured. Electrochemical studies revealed no fretting corrosion in retrieved stem tapers with ceramic heads. Consequently, three retrieved tapers and two new ones for comparison underwent potentiodynamic measurements in Hank’s solution to determine the corrosion rate of new and retrieved stem taper surfaces. The results showed a low corrosion rate for both new and prematurely failed retrieved samples due to aseptic loosening. However, the corrosion rate was higher in infected and low-grade infected tapers. In conclusion, our study suggests that using ceramic heads reduces taper corrosion and subsequently decreases the incidence of premature failures in total hip arthroplasty.
Keywords: total hip arthroplasty, stem micro-threaded taper, taper surface morphology, microstructure, corrosion, Ti implant alloy
Published in DiRROS: 06.06.2024; Views: 363; Downloads: 305
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Abstract: The pedunculate oak (Quercus robur L.) is economically and ecologically one of the most significant tree species in Serbia, however, little is known about the influence of the riverbed distance and its water supply on ecophysiological responses of this species. Given the limited information on the light-response curve of photosynthesis for oaks in southwest Srem, Serbia, the aim of this paper is to enhance understanding of their ecophysiological responses in this context. Maximum assimilation rate (Amax), the quantum yield (Ф), and light compensation point (LCP) were compared in adult trees situated along the transect from the river: (1) close to the river, (2) intermediate, (3) farthest from the river, and (4) forest reserve (second closest), with the first three transects being managed forests and the last one being an unmanaged forest reserve. The measurements were conducted in July during the first evidence of drought. The highest Amax rates were measured in all light intensities on the site closest to the river and the smallest on the site that was most distant to the water source. The most efficient were trees close to the river and the ones in the forest reserve. No significant difference between compensation points was confirmed for the studied groups of trees, although the forest reserve trees showed slightly higher values. The results demonstrated clear response between transects, which followed the distance from the riverbed. Pedunculate oak's reliance on groundwater is in tight relation with ecophysiological processes in trees; groundwater depletion may threaten its survival in areas distant from the river.
Keywords: Quercus robur L., floodplain forest, drought, light-response curves, transects
Published in DiRROS: 05.06.2024; Views: 1454; Downloads: 211
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