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. Experimental and numerical investigation of Rayleigh-Benard convection in rectangular cavity with motor oilPredrag Živković, Mladen A. Tomić, Sadoon Ayed, Cristian Barz, Drago Sever, 2023, original scientific article Abstract: Naturally flows have been the scope of the scientific research for centuries, Rayleigh-Benard convection being one of the leading. Many researchers have considered the flow patterns, boundary conditions, various cavities, nanofluids, theoretically, numerically, and experimentally. The flow was investigated in atmosphere and in nanofluids, in air, water, molten metals, non-Newtonian fluids. Almost all research focuses on 2-D or 3-D analysis of flow in laterally unlimited enclosures, as parallel plates or coaxial cylinders. In technical practice, only limited enclosures exist. This paper presents numerical and real experimental results for the test chamber with ratio 4×2×1 in x-, y-, and z direction, respectfully. The measurements were taken at fifteen different positions on the faces of the tank. Probes used are PT100 elements. As the chamber is limited in all directions, the results have shown strong influence of the lateral walls. The results are compared with the those obtained by IR camera. Various fluids were tested, and results for motor oil will be presented.
Keywords: Rayleigh-Bénard convection, temperature profile, PT100 probe, motor oil, numerical simulation
Published in DKUM: 27.03.2025; 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. Assessment of Dangerous Goods Transport: Case Western Balkan CountriesMarko Renčelj, Osman Lindov, Miloš Pljakić, Drago Sever, 2025, original scientific article Abstract: The transportation of dangerous goods (TDG) is a critical component of economic systems, especially in regions such as the Western Balkans (WB), where infrastructure and regulatory frameworks face significant challenges. This study assesses the current state of transportation of dangerous goods in Albania, Montenegro, Bosnia and Herzegovina, and Kosovo*, focusing on the alignment of national regulations with international standards such as the ADR agreement. Using a structured questionnaire distributed to 847 stakeholders, key barriers are identified, including inadequate infrastructure, insufficient training, limited oversight and low public awareness. Statistical analyses, including paired t-tests, reveal significant differences in perceptions across the countries surveyed, indicating inequalities in implementation and enforcement. Despite these challenges, there are opportunities to close gaps through targeted investments in infrastructure, increased training programs, stricter compliance and regional cooperation. The findings underscore the need for comprehensive data collection systems and advanced risk assessment tools to improve safety and efficiency. This study contributes to a deeper understanding of TDG issues in the WB countries and provides actionable recommendations for policy makers and practitioners to promote safer and more sustainable practices. The region can improve its TDG framework by addressing these challenges and ensuring economic growth and public safety while minimizing environmental risks.
Keywords: transport of dangerous goods, transportation, dangerous goods transport, risk assessment, ADR standards compliance, Western Balkan countries, sustainable transportation
Published in DKUM: 03.03.2025; Views: 0; Downloads: 4
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5. Properties of large 2-crossing-critical graphsDrago Bokal, Markus Chimani, Alexander Nover, Jöran Schierbaum, Tobias Stolzmann, Mirko H. Wagner, Tilo Wiedera, 2022, original scientific article Keywords: crossing number, crossing-critical graph, chromatic number, chromatic index, treewidth
Published in DKUM: 04.02.2025; Views: 0; Downloads: 4
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6. Zahteve za invalide in funkcionalno ovirane osebe na železniški infrastrukturiStefan Varešić, 2024, undergraduate thesis Abstract: V diplomski nalogi so obravnavani zakonski predpisi in regulative, ki se nanašajo na invalide in funkcionalno ovirane osebe ter njihove potrebe na železniški infrastrukturi. Predstavljeni so najbolj pomembni zakoni o pravicah, potrebah in obveznostih invalidov in funkcionalno oviranih oseb v železniškem sistemu. Raziskava vsebuje teoretični del in pregled opremljenosti železniških postaj v Sloveniji s poudarkom na železniški postaji Maribor. Na podlagi preučenih evropskih in nacionalnih zakonskih predpisov, pregleda obstoječe železniške infrastrukture na železniški postaji in pričakovanja invalidov ter funkcionalno oviranih oseb so podane ugotovitve s ciljem pridobivanja sistematičnega prikaza uporabnosti in prilagojenosti železniške infrastrukture za invalide in funkcionalno ovirane osebe. V zadnjem poglavju naloge pa so podani predlogi za izboljšave železniške infrastrukture in omogočanje enostavne ter neovirane dostopnosti za invalide in funkcionalno ovirane osebe na železniški infrastrukturi.
Keywords: Funkcionalno ovirane osebe, invalidi, železniška infrastruktura, dostopnost
Published in DKUM: 05.09.2024; Views: 38; Downloads: 24
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7. Uporaba alternativnih pogonov v avtomobilskem prometu : diplomsko delo univerzitetnega študijskega programaSašo Tadina, 2011, undergraduate thesis Abstract: Osebni avtomobili so najpogostejša oblika prevoza. Večina teh avtomobilov pa poganjajo fosilna goriva, ki povzročajo polucijo zraka in globalno segrevanje. Poleg tega pojenjajo tudi zaloge nafte. Fosilna goriva imajo, ekološko in ekonomsko gledano, številne negativne učinke tako na posameznika kot tudi na celotno družbo. Rešitve se ponujajo v obliki alternativnih goriv, kot so biogoriva, utekočinjen naftni plin in električna vozila.
Keywords: obremenjevanje okolja, globalno segrevanje, zaloge nafte, biogoriva, utekočinjen naftni plin, električna vozila
Published in DKUM: 05.07.2024; Views: 120; Downloads: 10
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8. Motivacija učiteljev za izobraževanje in usposabljanje v Biotehniškem centru NakloTamara Teršek, 2024, undergraduate thesis Abstract: V diplomskem delu je poudarjeno, da je izobraževanje temeljnega pomena za razvijanje kompetenc in prilagajanje spreminjajočim se potrebam učencev in družbe. Za udeležitev učiteljev na izobraževanjih ima veliko vlogo motivacija. Z diplomskim delom smo želeli pridobiti informacije, kako so učitelji zadovoljni z dodatnim usposabljanjem, kolikšna je njihova motivacija za pridobivanje dodatnega znanja in kakšno je njihovo zaupanje v sistem nadgrajevanja. Odločili smo se uporabiti opisno in kvantitativno metodo ter korelacijsko analizo. Pri raziskovalnem delu smo uporabili anketni vprašalnik, ki je bil razdeljen med učitelje v Biotehniškem centru Naklo. Za analizo podatkov le-tega smo si pomagali s programoma Microsoft Excel in SPSS. Raziskava je pokazala, da se učitelji želijo udeleževati različnih izobraževanj in usposabljanj. K dodatnemu izobraževanju jih motivira želja po dodatnem znanju. Največja ovira pa je pomanjkanje časa.
Keywords: Motivacija, izobraževanje, usposabljanje, učitelj, opisna statistika
Published in DKUM: 03.07.2024; Views: 189; Downloads: 38
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