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Povzetek: Orthotic and prosthetic materials should have good mechanical and antibacterial properties. Therefore, in our study, we consider four common foamed closed-cells and two solid polymeric materials regarding their mechanical behaviour and tendency for bacterial adhesion. For all materials, the surface roughness, hydrophobicity, zeta potential, tensile properties, hardness and CIE color parameters were measured. We found that foamed polymeric materials have higher roughness, higher hydrophobicity, lower Young's modulus, lower maximum tensile strength and lower hardness than solid materials. Bacterial adhesion test measurements based on observation by scanning electron microscopy show much a lower adhesion extent of S. aureus on solid materials than on foamed materials. The measured biophysical properties could be the key data for users to select the optimal materials.
Ključne besede: surface characterization, bacterial adhesion, foamed materials, prosthetic and orthotic material, surfaces
Objavljeno v DiRROS: 22.05.2023; Ogledov: 321; Prenosov: 200
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Povzetek: Pri nedrobnoceličnem raku pljuč (NDPR) so možganski zasevki prisotni v 30 do 44 %. Prognoza bolnikov z možganskimi (CŽS) zasevki je odvisna od različnih prognostičnih dejavnikov, ki vplivajo na odločitev o zdravljenju in posledično na dolžino preživetja. Glavni prognostični dejavniki so starost, telesna zmogljivost po Karnofskem, razširjenost bolezni zunaj CŽS in število zasevkov. Srednje preživetje za NDPR je glede na stopenjsko prognostično ocenjevalno lestvico z molekularnimi označevalci (Lung- molGPA) od 5 do 46 mesecev. Pri bolnikih s številnimi možganskimi zasevki je srednje preživetje krajše. Pri teh bolnikih je v prvi vrsti indicirano zdravljenje z obsevanjem cele glave. Pri boljši prognozi pride v poštev tudi obsevanje cele glave z dodatkom doze s stereotaktično radiokirurgijo (SRK) predvsem večjih zasevkov, ki povzročajo nevrološko simptomatiko.
Ključne besede: pljučni rak, onkološko zdravljenje, bolniki
Objavljeno v DiRROS: 12.05.2023; Ogledov: 404; Prenosov: 91
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Povzetek: Hybrid phenol-formaldehyde (PF) resins represent one of the most important niche groups of binding systems for composites. New industrial needs, environmental requirements, and price fluctuations have led to further research on materials with enhanced mechanical and thermal properties. The preparation of novel hybrid materials can be achieved by inclusion of various elements or functional groups in the organic polymer phenolic framework. Herein, we report the synthesis and characterization of a PF-based hybrid material with different nanoscale silicone species and ZnAl-layered double hydroxide (LDH). The main goals of this study were to improve the synthetic pathways of hybrid resin, as well as to prepare granulated composite materials and test samples and determine their characterization. Added inorganic species increased the glass-transition temperature by a minimum of 8 °C, which was determined using differential scanning calorimetry (DSC). Rheological properties (melting viscosity and flow distance) of the hybrid resin were measured. The homogeneity of distribution of added species across the organic matrix was evaluated with scanning electron microscopy (SEM). With synthesized new hybrid-binding systems, we prepared different granulated composite materials and evaluated them with the measurements of rheological properties (flow curing characteristics). Tensile strength of samples, prepared from granulated composite material, improved by more than 5%.
Ključne besede: phenol-formaldehyde hybrid resins, nano-SiO2, ZnAl-LDH, composites, glass-transition temperature, mechanical properties
Objavljeno v DiRROS: 03.05.2023; Ogledov: 423; Prenosov: 184
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Povzetek: This paper presents an experimental investigation of the compressive behavior of highstrength self-compacting concrete exposed to temperatures up to 600 C. Ten different concrete compositions were tested, in which part of the cement (by weight) was replaced by three different mineral additives (5–15% metakaolin, 20–40% fly ash and 5–15% limestone). The stress–strain curves, compressive strength, modulus of elasticity and strain at peak stress were evaluated from uniaxial compression tests. Scanning electron microscope micrographs were also taken to evaluate the damage caused by the high temperatures. A sharp decrease in mechanical properties and an increase in peak strain were observed already after 200 C for all mixes tested. The different mineral additives used in this study affected the variations of residual compressive strength by 24% and peak strain by 38%, while the variations of residual modulus elasticity were 14%. Comparing the obtained results with the recommendations for compressive strength given in regulatory code EN 1992-1-2 for high strength concrete, it can be concluded that the strength loss observed in EN 1992-1-2 at temperatures up to 400 C is too conservative. The Popovics model for the relationship between stress and strain provided a good approximation for the experimentally determined stress–strain curves at different temperatures.
Ključne besede: self-compacting concrete, mineral additives, high temperatures, residual mechanical properties, open access
Objavljeno v DiRROS: 28.04.2023; Ogledov: 382; Prenosov: 187
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Objavljeno v DiRROS: 26.04.2023; Ogledov: 387; Prenosov: 100
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