1. Extraction of bioactive metabolites from Achillea millefolium L. with choline chloride based natural deep eutectic solvents: a study of the antioxidant and antimicrobial activityMilena Ivanović, Dragana Grujić, Janez Cerar, Maša Islamčević Razboršek, Ljiljana Topalić-Trivunović, Aleksandar Savić, Drago Kočar, Mitja Kolar, 2022, original scientific article Abstract: In this study, the extraction efficiency of natural deep eutectic solvents (NADES) based on choline chloride as a hydrogen bond acceptor (HBA) and five different hydrogen bond donors (HBD; lactic acid, 1,4-butanediol, 1,2-propanediol, fructose and urea) was evaluated for the first time for the isolation of valuable bioactive compounds from Achillea millefolium L. The phytochemical profiles of NADES extracts obtained after ultrasound-assisted extraction were evaluated both spectrophotometrically (total phenolic content (TPC) and antioxidant assays) and chromatographically (UHPLC-MS and HPLC-UV). The results were compared with those obtained with 80% ethanol, 80% methanol, and water. The highest TPC value was found in the lactic acid-based NADES (ChCl-LA), which correlated with the highest antioxidant activity determined by the FRAP analysis. On the other hand, the highest antiradical potential against ABTS$^{+•}$ was determined for urea-based NADES. Phenolic acids (chlorogenic acid and dicaffeoylquinic acid isomers), flavones (luteolin and apigenin), and their corresponding glucosides were determined as the dominant individual phenolic compounds in all extracts. The antibacterial and antifungal properties of the extracts obtained against four bacterial cultures and two yeasts were evaluated using two methods: the agar dilution method to obtain the minimum inhibitory concentration (MIC) and the minimum bactericidal or fungicidal concentration (MBC or MFC), and the disc diffusion method. ChCl-LA had the lowest MIC and MBC/MFC with respect to all microorganisms, with an MIC ranging from 0.05 mg mL$^{−1}$ to 0.8 mg mL$^{−1}$, while the water extract had the weakest inhibitory activity with MIC and MBC/MFC higher than 3.2 mg mL$^{−1}$.
Keywords: viskoznost, fenoli, antioksidanti, natural deep eutectic solvents (NADES), density and viscosity, yarrow, phenolic compounds, antioxidant activity, antimicrobial activity
Published in DKUM: 09.04.2025; Views: 0; Downloads: 2
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2. Magnetic flux density measurement platform for an inductive wireless power transmitter coil designNataša Prosen, Miro Milanovič, Jure Domajnko, 2022, original scientific article Abstract: This paper presents a platform developed for automated magnetic flux density measurement. The platform was designed to be used to measure the magnetic flux density of the
transmitter/receiver coil of an inductive wireless power transfer system. The magnetic flux density
of a transmitter was measured using a small, 3-axis search coil. The search coil was positioned in
the 3D space above the transmitter coil using a 3D positioning mechanism and used to measure
the magnetic flux density at a specific point. The data was then sent to a computer application to
visualize the magnetic flux density. The measured magnetic field could be used in combination with
electromagnetic field solvers to design and optimize transmitter coils for inductive wireless power
transfer systems.
Keywords: magnetic field, magnetic flux density, IPT, transmitter coil design, EM solver
Published in DKUM: 01.04.2025; Views: 0; Downloads: 1
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3. Experimental and mathematical investigation of anaerobic granulate density via settling velocityAljaž Klasinc, Gregor Drago Zupančič, Matjaž Hriberšek, Aleš Hribernik, Aleksandra Lobnik, Matej Zadravec, 2022, original scientific article Abstract: The objective of this study was to determine the density of anaerobic granules on different
heights of a full-scale Upflow Anaerobic Sludge Bed reactor. The density was defined through the
settling velocities of anaerobic granules, measured in a full-scale Upflow Anaerobic Sludge Bed
reactor. In this study, granular density was calculated with the measured settling velocities and
developed mathematical model. The developed mathematical model is based on the Stokes model.
In the experiment, granules were taken from different heights of an Upflow Anaerobic Sludge Bed
reactor, from 0.6 to 7.6 m. The granules’ diameters varied between 1 and 5 mm. The granules were
taken from six different heights through the reactor. The settling velocity of the active granules
(with gas in the granule pore and on the surface of the granule) was measured first. After the active
granules’ settling velocity measurement, the granules were placed in a vortex to obtain degassed
granules (granules without any gas in the pores or on the surface), for which the settling velocities
were also measured later. It is shown that granules’ densities at different heights are independent of
the reactor height.
Keywords: Upflow Anaerobic Sludge Bed reactor, microstructure, anaerobic granular sludge, settling velocity, density
Published in DKUM: 26.03.2025; Views: 0; Downloads: 4
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4. Exploring antioxidative properties of xanthohumol and isoxanthohumol : an integrated experimental and computational approach with isoxanthohumol pKa determinationJelena Tošović, Zala Kolenc, Gregor Hostnik, Urban Bren, 2025, original scientific article Abstract: This study explores the antioxidative activities of xanthohumol (XN) and isoxanthohumol (IXN), prenylated flavonoids from Humulus lupulus (family Cannabaceae), utilizing the oxygen radical absorption capacity (ORAC) and ferric reducing antioxidant power (FRAP) assays along with computational Density Functional Theory methods. Experimentally, XN demonstrated significantly higher antioxidative capacities than IXN. Moreover, we determined IXN pKa values using the UV/Vis spectrophotometric method for the first time, facilitating its accurate computational modeling under physiological conditions. Through a thermodynamic approach, XN was found to efficiently scavenge HOO• and CH3O• radicals via Hydrogen Atom Transfer (HAT) and Radical Adduct Formation (RAF) mechanisms, while CH3OO• scavenging was feasible only through the HAT pathway. IXN exhibited its best antioxidative activity against CH3O• via both HAT and RAF mechanisms and could also scavenge HOO• through RAF. Both Single Electron Transfer (SET) and Sequential Proton Loss-Electron Transfer (SPLET) mechanisms were thermodynamically unfavorable for all radicals and both compounds.
Keywords: antioxidative activity, bio-active membranes, xanthohumol, isoxanthohumol, ORAC and FRAP assays, pKa determination, density functional theory, DFT
Published in DKUM: 31.01.2025; Views: 0; Downloads: 5
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5. Combined effect of build orientation and energy density on density and mechanical properties of selectively laser melted Co-Cr-W-SiSnehashis Pal, Igor Drstvenšek, 2022, original scientific article Abstract: The selective laser melting (SLM) process for manufacturing metals continues to be
challenging in terms of achieving the maximum metallurgical properties that the process can
provide. There are a variety of manufacturing parameters in the process that have individual
characteristics, and when combined with other variables, the characteristics can be varied.
However, in this study, the two most important manufacturing parameters, namely build direction
and laser power, were considered to investigate their effects on density and tensile properties.
Previously, the best scanning speed, hatch spacing, and layer thickness were determined, which
directly affect the volumetric energy density in the SLM process. In this study, three different
orientations and three different laser powers were selected, namely the X, Y, and Z directions and
55 W, 75 W, and 95 W laser power, respectively. Significant differences in product density were
observed for the samples fabricated in the different orientations and with the different laser
powers. The specimens fabricated in the Z direction always exhibit higher strength and ductility,
which are significantly different from the specimens fabricated in the X and Y directions, while
the laser power was 75 W and 95 W, respectively
Keywords: cobalt-chromium alloy, orientation, density, tensile strength, ductility, selective laser melting
Published in DKUM: 25.09.2024; Views: 0; Downloads: 8
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6. Motor unit discharge rate modulation during isometric contractions to failure is intensity- and modality-dependentTamara Valenčič, Paul Ansdell, Callum G. Brownstein, Padraig M. Spillane, Aleš Holobar, Jakob Škarabot, 2024, original scientific article Abstract: The physiological mechanisms determining the progressive decline in the maximal muscle torque production capacity during isometric contractions to task failure are known to depend on task demands. Task-specificity of the associated adjustments in motor unit discharge rate (MUDR), however, remains unclear. This study examined MUDR adjustments during different submaximal isometric knee extension tasks to failure. Participants performed a sustained and an intermittent task at 20% and 50% of maximal voluntary torque (MVT), respectively (Experiment 1). High-density surface EMG signals were recorded from vastus lateralis (VL) and medialis (VM) and decomposed into individual MU discharge timings, with the identified MUs tracked from recruitment to task failure. MUDR was quantified and normalised to intervals of 10% of contraction time (CT). MUDR of both muscles exhibited distinct modulation patterns in each task. During the 20% MVT sustained task, MUDR decreased until ∼50% CT, after which it gradually returned to baseline. Conversely, during the 50% MVT intermittent task, MUDR remained stable until ∼40–50% CT, after which it started to continually increase until task failure. To explore the effect of contraction intensity on the observed patterns, VL and VM MUDR was quantified during sustained contractions at 30% and 50% MVT (Experiment 2). During the 30% MVT sustained task, MUDR remained stable until ∼80–90% CT in both muscles, after which it continually increased until task failure. During the 50% MVT sustained task the increase in MUDR occurred earlier, after ∼70–80% CT. Our results suggest that adjustments in MUDR during submaximal isometric contractions to failure are contraction modality- and intensity-dependent.
Keywords: muscle contractions, high-density EMG signals, electromyiograms
Published in DKUM: 23.08.2024; Views: 117; Downloads: 10
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7. Traffic density-related black carbon distribution : impact of wind in a basin townBorut Jereb, Brigita Gajšek, Gregor Šipek, Špela Kovše, Matevž Obrecht, 2021, original scientific article Abstract: Black carbon is one of the riskiest particle matter pollutants that is harmful to human health. Although it has been increasingly investigated, factors that depend on black carbon distribution and concentration are still insufficiently researched. Variables, such as traffic density, wind speeds, and ground levels can lead to substantial variations of black carbon concentrations and potential exposure, which is even riskier for people living in less-airy sites. Therefore, this paper "fills the gaps" by studying black carbon distribution variations, concentrations, and oscillations, with special emphasis on traffic density and road segments, at multiple locations, in a small city located in a basin, with frequent temperature inversions and infrequent low wind speeds. As wind speed has a significant impact on black carbon concentration trends, it is critical to present how low wind speeds influence black carbon dispersion in a basin city, and how black carbon is dependent on traffic density. Our results revealed that when the wind reached speeds of 1 ms-1 , black carbon concentrations actually increased. In lengthy wind periods, when wind speeds reached 2 or 3 ms-1 , black carbon concentrations decreased during rush hour and in the time of severe winter biomass burning. By observing the results, it could be concluded that black carbon persists longer in higher altitudes than near ground level. Black carbon concentration oscillations were also seen as more pronounced on main roads with higher traffic density. The more the traffic decreases and becomes steady, the more black carbon concentrations oscillate.
Keywords: black carbon, black carbon concentration, traffic pollution, air pollution, wind, traffic density, logistics, basin city
Published in DKUM: 20.08.2024; Views: 44; Downloads: 8
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8. Investigation of the best manufacturing orientation of Co-Cr-W-Si dental prosthetic elements in the selective laser melting processSnehashis Pal, Janez Gotlih, Igor Drstvenšek, 2022, original scientific article Abstract: It is well known that Selective Laser Melting (SLM) does not provide the same mechanical
properties in all directions of the part. This is due to the microstructural grain orientation and
pore shape in SLM products. Therefore, depending on the direction of the pressure applied to the
SLM product, a different manufacturing orientation is required to achieve the best mechanical
properties. Changing the microstructural grain orientation is difficult through SLM, but a process
to reduce the size and number of the pores can be discovered through different combinations
of manufacturing parameters. In prosthodontics, pressure is usually applied in the vertical
direction, which leads to compression and bending of crowns with bridges. The compressive
load can be easily absorbed in the crowns, but the bending force has a significant effect here.
Therefore, a product with high tensile strength and high ductility is needed to survive longer.
Considering these requirements, this study determined the best parameters for laser processing
by SLM method to reduce porosity and improve mechanical strength and ductility of Co-CrW-Si alloy products. The result is a relative product density of 100% for cubic specimens and a
yield strength, ultimate tensile strength, and elongation at break of the tensile specimens of 900
MPa, 1200 MPa, and 15%, respectively, obtained in specimen build-up in the Z direction with a
laser power of 60 W and a scanning speed of 450 mm/s. Eventually, the best orientation for the
production of dental prosthetic elements using the SLM process was determined.
Keywords: cobalt-chromium alloy, dental implant, density, tensile strength, ductility, selective laser melting
Published in DKUM: 03.07.2024; Views: 78; Downloads: 12
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9. Motor unit identification in the M waves recorded by high-density electromyMiloš Kalc, Jakob Škarabot, Matjaž Divjak, Filip Urh, Matej Kramberger, Matjaž Vogrin, Aleš Holobar, 2023, original scientific article Keywords: M wave, high-density surface EMG, firing identification, motor unit
Published in DKUM: 13.06.2024; Views: 144; Downloads: 15
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10. Identification of motor unit firings in H-reflex of soleus muscle recorded by high-density surface electromyographyMiloš Kalc, Jakob Škarabot, Matjaž Divjak, Filip Urh, Matej Kramberger, Matjaž Vogrin, Aleš Holobar, 2023, original scientific article Keywords: motor units identification, high-density surface EMG, decomposition, H-reflex
Published in DKUM: 13.06.2024; Views: 133; Downloads: 15
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