1621. Antibacterial and antibiofouling activities of carbon polymerized dots/polyurethane and c[sub]60/polyurethane composite filmsZoran M. Marković, Milica D. B. Filimonović, Dušan Milivojević, Janez Kovač, Biljana Todorović-Marković, 2024, original scientific article Abstract: The cost of treatment of antibiotic-resistant pathogens is on the level of tens of billions of dollars at the moment. It is of special interest to reduce or solve this problem using antimicrobial coatings, especially in hospitals or other healthcare facilities. The bacteria can transfer from medical staff or contaminated surfaces to patients. In this paper, we focused our attention on the antibacterial and antibiofouling activities of two types of photodynamic polyurethane composite films doped with carbon polymerized dots (CPDs) and fullerene C60. Detailed atomic force, electrostatic force and viscoelastic microscopy revealed topology, nanoelectrical and nanomechanical properties of used fillers and composites. A relationship between the electronic structure of the nanocarbon fillers and the antibacterial and antibiofouling activities of the composites was established. Thorough spectroscopic analysis of reactive oxygen species (ROS) generation was conducted for both composite films, and it was found that both of them were potent antibacterial agents against nosocomial bacteria (Klebsiela pneumoniae, Proteus mirabilis, Salmonela enterica, Enterococcus faecalis, Enterococcus epidermis and Pseudomonas aeruginosa). Antibiofouling testing of composite films indicated that the CPDs/PU composite films eradicated almost completely the biofilms of Pseudomonas aeruginosa and Staphylococcus aureus and about 50% of Escherichia coli biofilms
Published in DiRROS: 11.07.2025; Views: 399; Downloads: 138
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1622. Phloroglucinol-based carbon quantum dots/polyurethane composite films : how structure of carbon quantum dots affects antibacterial and antibiofouling efficiency of composite filmsZoran M. Marković, Dušan Milivojević, Janez Kovač, Biljana Todorović-Marković, 2024, original scientific article Abstract: Nowadays, bacteria resistance to many antibiotics is a huge problem, especially in clinics and other parts of the healthcare system. This critical health issue requires a dynamic approach to produce new types of antibacterial coatings to combat various pathogen microbes. In this research, we prepared a new type of carbon quantum dots based on phloroglucinol using the bottom-up method. Polyurethane composite films were produced using the swell–encapsulation–shrink method. Detailed electrostatic force and viscoelastic microscopy of carbon quantum dots revealed inhomogeneous structure characterized by electron-rich/soft and electron-poor/hard regions. The uncommon photoluminescence spectrum of carbon quantum dots core had a multipeak structure. Several tests confirmed that carbon quantum dots and composite films produced singlet oxygen. Antibacterial and antibiofouling efficiency of composite films was tested on eight bacteria strains and three bacteria biofilms.
Published in DiRROS: 11.07.2025; Views: 423; Downloads: 126
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1623. Značilnosti lesnih prirastkov v deblu in vejah oljke (Olea europaea L.)Jožica Gričar, Klemen Eler, 2025, original scientific article Abstract: Oljka (Olea europaea L.) je gospodarsko zelo pomembna vednozelena kulturna rastlina, a je zelo malo znanega o njeni strukturi lesa v različnih delih drevesa, ki je ključna za dolgoročno preživetje drevesa. V pričujočem prispevku smo primerjali značilnosti lesnih prirastkov v deblu in vejah pri oljki v Dekanih v rastni sezoni 2016. Analizirali smo tudi prevodne elemente v lesu (traheje) v posameznih tretjinah lesnih branik. Razlike v značilnostih trahej na začetku in koncu rastne sezone ter v različnih delih drevesa smo interpretirali z vidika njihove prevajalne vloge v drevesu. V ta namen smo vzorce lesa odvzeli po zaključku rastne sezone 2016, pripravili preparate prečnih prerezov in opravili histometrične analize s pomočjo svetlobnega mikroskopa in sistema za analizo slike. Ugotovili smo, da se širine lesnih prirastkov in značilnosti trahej v deblu in vejah oljk razlikujejo. Prirastki 2016 so bili v vejah približno 54 % ožji kot v deblu, površine trahej pa od 25 % (prva tretjina) do 34 % (zadnja tretjina) manjše. Površine trahej so bile primerljive v prvi in drugi tretjini branike, medtem ko je bila v zadnji tretjini površina značilno manjša, in sicer v povprečju za 17,6 % v deblu in 25,4 % v vejah. V vseh tretjinah lesnih branik v deblu in vejah smo zabeležili negativno zvezo med povprečnimi vrednostmi površine trahej in gostoto trahej. Pri oljkah se je to odražalo v primerljivih vrednostih hidravlične prevodnosti v vseh tretjinah v deblu in vejah. Ožji prevodni elementi v vejah oljk kot posledica hormonske regulacije so v skladu z univerzalno pozitivno zvezo med velikostjo trahej in oddaljenostjo od apeksa in so povezani z večjo tenzijsko napetostjo vodnih stolpcev v trahejah vej v primerjavi z deblom. Različna struktura lesa v deblu in vejah nakazuje na različno vlogo tega tkiva v različnih delih drevesa.
Keywords: les, branika, difuzno-porozna vrsta, traheja, anatomija lesa, prevodnost, svetlobna mikroskopija
Published in DiRROS: 10.07.2025; Views: 333; Downloads: 172
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1624. Biocompatible carbon dots/polyurethane composites as potential agents for combating bacterial biofilms : N-doped carbon quantum dots/polyurethane and gamma ray-modified graphene quantum dots/polyurethane compositesZoran Marković, Slađana Dorontić, Svetlana P. Jovanović, Janez Kovač, Dušan Milivojević, Dragana Marinković, Marija Mojsin, Biljana Todorović-Marković, 2024, original scientific article Abstract: Pathogen bacteria appear and survive on various surfaces made of steel or glass. The existence of these bacteria in different forms causes significant problems in healthcare facilities and society. Therefore, the surface engineering of highly potent antimicrobial coatings is highly important in the 21st century, a period that began with a series of epidemics. Methods: In this study, we prepared two types of photodynamic polyurethane-based composite films encapsulated by N-doped carbon quantum dots and graphene quantum dots irradiated by gamma rays at a dose of 50 kGy, respectively. Further, we investigated their structural, optical, antibacterial, antibiofouling and biocompatibility properties. Results: Nanoelectrical and nanomechanical microscopy measurements revealed deviations in the structure of these quantum dots and polyurethane films. The Young’s modulus of elasticity of the carbon and graphene quantum dots was several times lower than that for single-walled carbon nanotubes (SWCNTs) with chirality (6,5). The electrical properties of the carbon and graphene quantum dots were quite similar to those of the SWCNTs (6,5). The polyurethane films with carbon quantum dots were much more elastic and smoother than the films with graphene quantum dots. Antibacterial tests indicated excellent antibacterial activities of these films against a wide range of tested bacteria, whereas the antibiofouling activities of both composite films showed the best results against the Staphylococcus aureus and Escherichia coli biofilms. Biocompatibility studies showed that neither composite film exhibited any cytotoxicity or hemolysis. Conclusions: Obtained results indicate that these composite films could be used as antibacterial surfaces in the healthcare facilities.
Published in DiRROS: 10.07.2025; Views: 411; Downloads: 135
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1625. Temperature-driven shifts in spatiotemporal stability of climate-growth responses of Douglas-fir (Pseudotsuga menziesii) from the southern Baltic Sea regionMarcin Miroslav Klisz, Radosław Puchałka, Mariusz Gławenda, M. Koprowski, Roberts Matisons, Sandra Metslaid, Aleksei Potapov, Tobias Scharnweber, Eric Andreas Thurm, Rita Verbylaite, Adomas Vitas, Martin Wilmking, Jernej Jevšenak, 2025, original scientific article Abstract: The southern Baltic region spans a significant part of the European continent with its forests under significant pressure due to climate changes. The implications of these changes are crucial for both native and non-native tree species. Under future climate scenarios, most native conifer populations might lose their climatic optima in the region. In contrast, for non-native Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), climatic conditions are expected to become optimal in the Baltic Sea region. Therefore, understanding the acclimatisation trajectory of Douglas-fir over the last century is essential to assess its potential to supplement retreating species and reduce pressure on local habitats. To study the region-wide acclimatisation in the secondary distribution, we established a network of 27 Douglas-fir tree-ring chronologies along the south Baltic Sea. We determined the spatio-temporal stability of the climate signal in tree rings and the potential coastal effect on the plasticity of the growth response. We found a region-wide trend of climate-growth relationships, with a dominant effect of the early-growth season temperatures being more pronounced for mature than young stands. Sites with higher mean annual temperatures exhibit a stronger positive temperature–growth correlation, demonstrating the sensitivity of Douglas-fir to climate warming. Douglas-fir could serve as a more heat-tolerant alternative to the declining European species of the Pinaceae family and contribute to the preservation of functionally comparable coniferous forest communities. However, forest practitioners should be aware that Douglas-fir may alter habitat conditions affecting microclimate and influencing species diversity.
Keywords: climate warming, climate–growth relationships, dendroecology, Europe, tree growth
Published in DiRROS: 09.07.2025; Views: 441; Downloads: 366
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1628. Capacity-building for gender awareness and competences in forestry educationNike Krajnc, Darja Stare, Polona Hafner, Katarina Flajšman, Mateja Karničnik, Tatjana Pavlič, Ema Šumenjak, Sabina Majerič, Špela Pezdevšek Malovrh, Zala Uhan, 2025, treatise, preliminary study, study Keywords: forestry, gender equality, youth employment, employment, sustainable development, environmental education
Published in DiRROS: 09.07.2025; Views: 414; Downloads: 253
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1629. Good practice examples of career orientation in forestry : collection of good practice examples that help to counteract stereotypes and spark curiosity about the world of forestryNike Krajnc, Darja Stare, Polona Hafner, Katarina Flajšman, Mateja Karničnik, Tatjana Pavlič, Ema Šumenjak, Sabina Majerič, Špela Pezdevšek Malovrh, Zala Uhan, 2025, treatise, preliminary study, study Keywords: forestry, gender equality, youth employment, employment, sustainable development, environmental education
Published in DiRROS: 09.07.2025; Views: 475; Downloads: 256
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1630. Compilation of good practice examples of career orientation in forestryNike Krajnc, Darja Stare, Polona Hafner, Katarina Flajšman, Mateja Karničnik, Tatjana Pavlič, Ema Šumenjak, Sabina Majerič, Špela Pezdevšek Malovrh, Zala Uhan, 2025, treatise, preliminary study, study Keywords: forestry, gender equality, youth employment, employment, sustainable development, environmental education
Published in DiRROS: 09.07.2025; Views: 532; Downloads: 273
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