1. Microscopy of crustacean cuticle : formation of a flexible extracellular matrix in moulting sea slaters Ligia pallasiiJasna Štrus, Magda Tušek-Žnidarič, Urška Repnik, Andrej Blejec, Adam P. Summers, 2019, original scientific article Abstract: Structural and functional properties of exoskeleton in moulting sea slaters Ligia pallasii from the Eastern Pacific coast were investigated with CT scanning and electron microscopy. Ultrastructure of preecdysial and postecdysial cuticular layers was described in premoult, intramoult and postmoult animals. Cuticle is a flexible extracellular matrix connected to the epidermal cells through pore channels. During premoult epicuticle and exocuticle are formed and during intramoult and postmoult endocuticular lamellae are deposited and the cuticle is progressively constructed by thickening and mineralization. Cuticle permeability, flexibility and waterproofing capacity change accordingly. Elaboration of epicuticular scales connected to an extensive network of nanotubules, establish its anti-adhesive and hydrophobic properties. Labelling with gold conjugated WGA lectins on Tokuyashu thawed cryosections exposes differences in chitin content between exocuticle and endocuticle. Histochemical staining of cuticle shows presence of acidic carbohydrates/glycoconjugates and lipoproteins in epicuticular layer. Chitin microfibrils are formed at the microvillar border of epidermal cells with abundant Golgi apparatus and secretory vesicles. Numerous spherules associated with nanotubules were observed in the ecdysial space in intramoult animals. The mineral component of the cuticle as visualized with CT scanning indicates progressive mineral resorption from the posterior to the anterior half of the body in premoult animals, its translocation from the anterior to posterior part during intramoult and its progressive deposition in the posterior and anterior exoskeleton during postmoult. Cuticle of sea slaters is a unique biocomposite and biodynamic material constantly reconstructed during frequent moults, and adapted to specific physical and biotic conditions of the high intertidal rocky zone. Keywords: cuticle ultrastructure, micro CT scanning, moult cycle, SEM, TEM, terrestrial isopods Published in DiRROS: 23.07.2024; Views: 227; Downloads: 218
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2. Characterization of micro-threaded stem taper surface of cementless hip endoprosthesesDrago Dolinar, Boštjan Kocjančič, Klemen Avsec, Barbara Šetina, Aleksandra Kocijan, Matjaž Godec, Marko Sedlaček, Mojca Debeljak, John T. Grant, Timon Zupanc, Monika Jenko, 2024, original scientific article 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: 210; Downloads: 206
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3. A numerical study of gas focused non-Newtonian micro-jetsRizwan Zahoor, Saša Bajt, Božidar Šarler, 2024, original scientific article Keywords: serial crystallography, micro jets, multiphase flow, fluid rheology, non-Newtonian fluid, flow focusing Published in DiRROS: 28.02.2024; Views: 342; Downloads: 176
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4. An experimental study of liquid micro-jets produced with a gas dynamic virtual nozzle under the influence of an electric fieldBor Zupan, Gisel Esperanza Peña-Murillo, Rizwan Zahoor, Jurij Gregorc, Božidar Šarler, Juraj Knoška, Alfonso M. Gañán-Calvo, Henry N. Chapman, Saša Bajt, 2023, original scientific article Abstract: The results of an experimental study of micro-jets produced with a gas dynamic virtual nozzle (GDVN) under the influence of an electric field are provided and discussed for the first time. The experimental study is performed with a 50% volume mixture of water and ethanol, and nitrogen focusing gas. The liquid sample and gas Reynolds numbers range from 0.09–5.4 and 0–190, respectively. The external electrode was positioned 400–500 μm downstream of the nozzle tip and an effect of electric potential between the electrode and the sample liquid from 0–7 kV was investigated. The jetting parametric space is examined as a function of operating gas and liquid flow rates, outlet chamber pressure, and an external electric field. The experimentally observed jet diameter, length and velocity ranged from 1–25 μm, 50–500 μm and 0.5–10 m/s, respectively. The jetting shape snapshots were processed automatically using purposely developed computer vision software. The velocity of the jet was calculated from the measured jet diameter and the sample flow rate. It is found that micro-jets accelerate in the direction of the applied electric field in the downstream direction at a constant acceleration as opposed to the standard GDVNs. New jetting modes were observed, where either the focusing gas or the electric forces dominate, encouraging further theoretical and numerical studies towards optimized system design. The study shows the potential to unlock a new generation of low background sample delivery for serial diffraction measurements of weakly scattering objects. Keywords: micro jet, electric field, experimental study, flow focusing, Taylor cone, gas dynamic virtual nozzles Published in DiRROS: 07.02.2024; Views: 484; Downloads: 184
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5. Degradation and Stabilization of Polymer MaterialsBranka Mušič, Andrijana Sever Škapin, 2023, other scientific articles Keywords: polymer-based materials, nano, micro, and macro composites, effects on (micro) organisms and toxicity, impact on the ecosystem, mechanisms and products of accelerated aging and degradation, physical, chemical, mechanical, thermal, and morphological, analysis, biodegradability, sustainability, life cycle, renewable and recycled resources and the circular economy Published in DiRROS: 21.12.2023; Views: 533; Downloads: 180
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6. Characterization of fly ash alkali activated foams obtained using sodium perborate monohydrate as a foaming agent at room and elevated temperaturesLidija Korat, Vilma Ducman, 2020, original scientific article Abstract: Alkali activated foams have been extensively studied in recent years, due to their high performance and low environmental footprint compared to foams produced via other methods. Three types of fly ash differing in chemical and mineralogical composition and specific surface were used to synthesize alkali activated foams. Sodium perborate monohydrate was added as a foaming agent and sodium dodecyl sulphate as a stabilizing agent. Foams were characterized at room temperature and after exposure to an elevated temperature (1,000 °C). Densities from 1.2 down to 0.3 g/cm 3 were obtained, depending on the type of fly ash and quantity of foaming agent added. Correspondingly, compressive strength ranged from 1 to 6 MPa. Comparing all three fly ashes the most favorable results, in terms of density and corresponding compressive strength, were achieved from the fly ash with the highest amounts of SiO 2 and Al2 O 3 , as well as the highest amorphous phase content i.e., RI fly ash. Furthermore, after firing to 1,000 °C, the density of samples prepared using fly ash RI remained approximately the same, while the compressive strength increased on average by 50%. In the other two types of fly ash the density increased slightly after firing, due to significant shrinkage, and compressive strength increased by as much as 800%. X-ray powder diffraction analysis confirmed the occurrence of a crystallization process after firing to 1,000 ° C, which resulted in newly formed crystal phases, including nepheline, sodalite, tridymite, and gehlenite. Keywords: foamed alkali activated materials, geopolymers, properties, micro-CT Published in DiRROS: 22.08.2023; Views: 431; Downloads: 267
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9. Multiscale modeling of (hemi)cellulose hydrolysis and cascade hydrotreatment of 5-hydroxymethylfurfural, furfural, and levulinic acidRok Šivec, Miha Grilc, Matej Huš, Blaž Likozar, 2019, review article Keywords: micro-kinetic multi-scale modelling, catalytic hydrodeoxygenation reactions, 5-hydroxymethylfurfural, furfural, levulinic acid Published in DiRROS: 23.11.2020; Views: 1471; Downloads: 1089
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