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1051 - 1060 / 2000
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1057.
Effect of sucrose concentration on streptococcus mutans adhesion to dental material surfaces
Anamarija Zore, Franc Rojko, Nives Matijaković Mlinarić, Jona Veber, Aleksander Učakar, Roman Štukelj, Andreja Pondelak, Andrijana Sever Škapin, Klemen Bohinc, 2024, original scientific article

Abstract: Enamel demineralization, known as dental caries, is instigated by the bacterium Streptococcus mutans, which generates acid during carbohydrate metabolism. Among carbohydrates, sucrose is the most cariogenic and capable of biofilm formation. This study aimed to explore and comprehend Streptococcus mutans’ adherence to two prevalent dental material surfaces, i.e., a cobalt–chromium(Co-Cr) alloy and a resin-based composite, under the influence of various sucrose concentrations. To understand bacterial adhesion, the surfaces were characterized using profilometry, tensiometry, and surface charge measurements. Bacterial adhesion was evaluated using scanning electron microscopy and crystal violet dye methods. Results revealed that the composite surface exhibited greater rough-ness compared with the Co-Cr alloy surface. Both surfaces displayed hydrophilic properties and a negative surface charge. Bacterial adhesion experiments indicated lower bacterial adherence to the Co-Cr alloy than to the composite surface before the addition of sucrose. However, the introduction of sucrose resulted in biofilm development on both surfaces, showcasing a similar increase in bacterial adhesion, with the highest levels being observed at a 5% sucrose concentration in the bacterial suspension. In conclusion, the findings suggest sucrose-rich foods could facilitate bacterial adaptation despite less favorable surface characteristics, thereby promoting biofilm formation.
Keywords: bacterial adhesion, streptococcus mutans, dental material surfaces, sucrose concentration
Published in DiRROS: 31.01.2024; Views: 306; Downloads: 127
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1058.
The influence of different fibres quantity on mechanical and microstructural properties of alkali-activated foams
Katja Traven, Mark Češnovar, Barbara Horvat, Vilma Ducman, 2022, published scientific conference contribution

Abstract: Alkali activated foams (AAFs) were produced using electric arc furnace steel slag (EAF) and ladle furnace basic slag (LS), obtained from two metallurgical companies in Slovenia. They were activated with a mixture of sodium water glass (Na2SiO3) and solid NaOH and foamed with hydrogen peroxide (H2O2). Pores were stabilized with the addition of Triton as a surfactant. Four types of fibres were added to the studied mixture (polypropylene (PP), polyvinyl-alcohol (PVA), basalt (B), and glass wool (GW)) in five different quantities: 0.5, 1.0, 1.25, 1.5 and 2.0 vol % in order to additionally stabilize the structure and thus improve its mechanical properties. The results of mechanical properties showed, that compressive strength was increased in all 20 specimens, partially due to the increased density as well as to the fibre addition. Flexural strength on the other hand was the most improved in the samples where PP and PVA fibres were added. The samples with the addition of B and GW fibres on the other hand showed only small or no improvement in flexural strength in comparison to the referenced sample. Additionally, the microstructure of used fibres and selected foams was also investigated by the means of SEM analysis.
Keywords: fibers, alkali activated foams, properties
Published in DiRROS: 31.01.2024; Views: 257; Downloads: 117
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1059.
Bio-solution for global sand crisis and sustainable organic agriculture in desert states
Darina Štyriaková, Iveta Štyriakova, Jaroslav Šuba, Felix Föhre, 2022, published scientific conference contribution

Abstract: Sand is an important component of many everyday items, and currently sand is the second most extracted resource on earth after water, but it is not sustainable: we are running out of sand! The black market is booming, and the sand mafia is mining sand at any price. Desert sand is unusable, even Dubai must import it. The smooth surface and iron impurities prevent its industrial use. In this study, bacteria in the bioleaching test attacked the surface of the mineral grains and dissolved impurities including iron through organic acids. Furthermore, the liquid residue containing dissolved iron, organic acids and bacteria stimulated the growth plant what can be a valuable biofertilizer and biostimulant for organic agriculture. Desert states have fertility problems. Despite this, Qatar, for example, is aiming for self-sufficiency in vegetables “in five years”. Results showed that bioleaching combined with magnetic separation resulted in iron removal of 73.23%. The sand after treatment can be suitable to produce clear flat glass, coloured container glass, insulating glass fibres or ceramics. The integrated technology based ecological study revealed overall as utilization potential of the desert sand and the liquid residue could support glass and food production in desert states.
Keywords: materials, sand, bioleaching, sustainable organic agriculture, desert states
Published in DiRROS: 31.01.2024; Views: 301; Downloads: 173
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1060.
Rejuvenator obtained by pyrolysis of waste tires for use in asphalt mixtures with added reclaimed asphalt
Lidija Ržek, Mojca Ravnikar Turk, Marjan Tušar, 2022, independent scientific component part or a chapter in a monograph

Abstract: Although in recent years, big progress has been made in the field of recovering waste tires, they still represent an unwanted waste and their production is constantly increasing. We can use waste tires as a raw material for a new product. In our study, multiple liquid products were produced by pyrolysis of waste tires. After extensive testing of their properties, we selected the most suitable pyrolytic product for the purpose of rejuvenation. Rejuvenators are designed to soften the old, brittle and stiff aged bitumen in reclaimed asphalt. Bitumen with its viscoelastic characteristics is the most important component of asphalt and dictates its behaviour. Commonly bitumen, after adding rejuvenator, becomes less viscous, more ductile and its coating properties are restored. By using a pyrolytic rejuvenator, the proportion of reclaimed asphalt added to the asphalt mixture was increased. The reuse of reclaimed asphalt and waste tires means a reduction in waste material and is therefore important for the preservation of the environment and sustainable development.
Keywords: pyrolyse, rejuvenator, bitumen, reclaimed asphalt, waste tires
Published in DiRROS: 31.01.2024; Views: 302; Downloads: 128
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