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1.
Study of ▫$Ni/Y_2O_3/polylactic$▫ acid composite
Tilen Švarc, Matej Zadravec, Žiga Jelen, Peter Majerič, Blaž Kamenik, Rebeka Rudolf, 2023, original scientific article

Abstract: This study demonstrates the successful synthesis of Ni/Y2O3 nanocomposite particles through the application of ultrasound-assisted precipitation using the ultrasonic spray pyrolysis technique. They were collected in a water suspension with polyvinylpyrrolidone (PVP) as the stabiliser. The presence of the Y2O3 core and Ni shell was confirmed with transmission electron microscopy (TEM) and with electron diffraction. The TEM observations revealed the formation of round particles with an average diameter of 466 nm, while the lattice parameter on the Ni particle’s surface was measured to be 0.343 nm. The Ni/Y2O3 nanocomposite particle suspensions were lyophilized, to obtain a dried material that was suitable for embedding into a polylactic acid (PLA) matrix. The resulting PLA/Ni/Y2O3 composite material was extruded, and the injection was moulded successfully. Flexural testing of PLA/Ni/Y2O3 showed a slight average decrease (8.55%) in flexural strength and a small decrease from 3.7 to 3.3% strain at the break, when compared to the base PLA. These findings demonstrate the potential for utilising Ni/Y2O3 nanocomposite particles in injection moulding applications and warrant further exploration of their properties and new applications in various fields.
Keywords: ultrasound spray pyrolysis, Ni/Y2O3, lyophilization, PLA, extrusion, injection moulding
Published in DKUM: 05.04.2024; Views: 98; Downloads: 7
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Recovery study of gold nanoparticle markers from lateral flow immunoassays
Tilen Švarc, Peter Majerič, Darja Feizpour, Žiga Jelen, Matej Zadravec, Timi Gomboc, Rebeka Rudolf, 2023, original scientific article

Abstract: Lateral flow immunoassays (LFIAs) are a simple diagnostic device used to detect targeted analytes. Wasted and unused rapid antigen lateral flow immunoassays represent mass waste that needs to be broken down and recycled into new material components. The aim of this study was to recover gold nanoparticles that are used as markers in lateral flow immunoassays. For this purpose, a dissolution process with aqua regia was utilised, where gold nanoparticles were released from the lateral flow immunoassay conjugate pads. The obtained solution was then concentrated further with gold chloride salt (HAuCl4) so that it could be used for the synthesis of new gold nanoparticles in the process of ultrasonic spray pyrolysis (USP). Various characterisation methods including scanning electron microscopy, transmission electron microscopy, ultraviolet-visible spectroscopy and optical emission spectrometry with inductively coupled plasma were used during this study. The results of this study showed that the recovery of gold nanoparticles from lateral flow immunoassays is possible, and the newly synthesised gold nanoparticles represent the possibility for incorporation into new products.
Keywords: gold nanoparticles, recovery, LFIA, ultrasonic spray pyrolysis, characterisation
Published in DKUM: 09.02.2024; Views: 202; Downloads: 14
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5.
Reconstruction of a fluid bed device for separating granular material from the grinding process of rapid antigen tests
Miha Jordan, Tilen Švarc, Peter Majerič, Rebeka Rudolf, Matej Zadravec, 2023, original scientific article

Abstract: The article includes the study and reconstruction of a fluid bed device with the purpose of separating the granular material from the grinding process of rapid antigen tests. The following techniques were performed, with the purpose of characterisation of the ground particles: sieve analysis, X-ray fluorescence spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and transmission electron microscopy. The paper includes experimental testing of a simplified separation process with zeolite spheres and paper strips, supported by a numerical model. The flow conditions’ impact on the behaviour and interactions of particles of the considered problem were simulated using coupled computational fluid dynamics (CFD) and the discrete element method (DEM) approach. The separation process of zeolite spheres and paper strips was found to be efficient. The simulation results showed the appropriate behaviour of the particles during the process. We explained the results’ deviations, and we also presented the shortcomings and possible improvements. Further research is required to define the adequacy of the process, while using actual ground material of rapid antigen tests.
Keywords: rapid antigen tests, nanomaterials, fluidised bed, computational fluid dynamics, discrete element method, characterisation
Published in DKUM: 05.01.2024; Views: 257; Downloads: 22
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6.
Melting point of dried gold nanoparticles prepared with ultrasonic spray pyrolysis and lyophilisation
Žiga Jelen, Marcin Krajewski, Franc Zupanič, Peter Majerič, Tilen Švarc, Ivan Anžel, Jernej Ekar, Sz-Chian Liou, Jerzy Kubacki, Mateusz Tokarczyk, Rebeka Rudolf, 2023, original scientific article

Abstract: A coupled process of ultrasonic spray pyrolysis and lyophilisation was used for the synthesis of dried gold nanoparticles. Two methods were applied for determining their melting temperature: uniaxial microcompression and differential scanning calorimetry (DSC) analysis. Uniaxial microcompression resulted in sintering of the dried gold nanoparticles at room temperature with an activation energy of 26–32.5 J/g, which made it impossible to evaluate their melting point. Using DSC, the melting point of the dried gold nanoparticles was measured to be around 1064.3°C, which is close to pure gold. The reason for the absence of a melting point depression in dried gold nanoparticles was their exothermic sintering between 712 and 908.1°C.
Keywords: gold nanoparticles, melting point, ultrasonic spray pyrolysis, characterisation
Published in DKUM: 08.12.2023; Views: 279; Downloads: 22
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7.
Physicochemical properties of gold nanoparticles for skin care creams
Peter Majerič, Zorana Jović, Tilen Švarc, Žiga Jelen, Andrej Horvat, Djuro Koruga, Rebeka Rudolf, 2023, original scientific article

Abstract: Gold nanoparticles (AuNPs) have now been used in skin care creams for several years, with marketed anti-aging, moisturizing, and regenerative properties. Information on the harmful effects of these nanoparticles is lacking, a concern for the use of AuNPs as cosmetic ingredients. Testing AuNPs without the medium of a cosmetic product is a typical method for obtaining this information, which is mainly dependent on their size, shape, surface charge, and dose. As these properties depend on the surrounding medium, nanoparticles should be characterized in a skin cream without extraction from the cream’s complex medium as it may alter their physicochemical properties. The current study compares the sizes, morphology, and surface changes of produced dried AuNPs with a polyvinylpyrrolidone (PVP) stabilizer and AuNPs embedded in a cosmetic cream using a variety of characterization techniques (TEM, SEM, DLS, zeta potential, BET, UV–vis). The results show no observable differences in their shapes and sizes (spherical and irregular, average size of 28 nm) while their surface charges changed in the cream, indicating no major modification of their primary sizes, morphology, and the corresponding functional properties. They were present as individually dispersed nanoparticles and as groups or clusters of physically separated primary nanoparticles in both dry form and cream medium, showing suitable stability. Examination of AuNPs in a cosmetic cream is challenging due to the required conditions of various characterization techniques but necessary for obtaining a clear understanding of the AuNPs’ properties in cosmetic products as the surrounding medium is a critical factor for determining their beneficial or harmful effects in cosmetic products.
Keywords: gold nanoparticles, ultrasonic spray pyrolysis, freeze drying, characterization, creams
Published in DKUM: 19.04.2023; Views: 606; Downloads: 53
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8.
Proces sinteze nanokompozita Ni/Y2O3 z ultrazvočno razpršilno pirolizo in liofilizacijo : magistrsko delo
Tilen Švarc, 2022, master's thesis

Abstract: Magistrsko delo obsega proces sinteze nanokompozita Ni/Y2O3 z ultrazvočno razpršilno pirolizo in liofilizacijo, študijo vpliva tehnoloških parametrov na sestavo delcev nanokompozita Ni/Y2O3 in vpliva stabilizatorja na potek sušenja. Za karakterizacijo nanokompozita so bile uporabljene naslednje tehnike: analiza z induktivno sklopljeno plazmo z masnim spektrometrom, vrstična elektronska mikroskopija, energijsko disperzijska spektroskopija, presevna elektronska mikroskopija, CIELAB meritve barve in optična mikroskopija. Suspenzija nanokompozita je bila analizirana s pomočjo dinamičnega sipanja svetlobe. Raziskan je bil vpliv koncentracije vhodnih surovin itrijeva in nikljeva nitrata pri nespremenjenih procesnih pogojih na kemijsko sestavo in velikost delcev nanokompozita Ni/Y2O3. Ugotovljeno je bilo, da povečana koncentracija stabilizatorja v procesu ultrazvočne razpršilne pirolize vpliva na bolj homogeno porazdelitev delcev nanokompozita Ni/Y2O3 v končnem osušenem materialu. Povečanje koncentracije stabilizatorja vpliva na daljši čas sušenja v procesu liofilizacije, saj so eksperimenti potrdili, da se suspenzija delcev nanokompozita Ni/Y2O3 z nižjo koncentracijo stabilizatorja posuši bistveno hitreje.
Keywords: ultrazvočna razpršilna piroliza, liofilizacija, nanokompozit, karakterizacija
Published in DKUM: 07.09.2022; Views: 608; Downloads: 112
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9.
Primerjava managementskih funkcij v profitnih in neprofitnih organizacijah
Ana Švarc, 2020, undergraduate thesis

Abstract: Vsako podjetje ne glede na to, ali je profitno ali neprofitno, potrebuje dobrega managerja. Management pri svojem delu opravlja predvsem štiri funkcije. V tem delu bomo predstavili in razložili planiranje, organiziranje, vodenje in kontroling. Podrobneje bomo predstavili profitne in neprofitne organizacije, za kaj katero deluje, v dobrobit koga deluje, kako deluje. Za praktični primer profitne organizacije bomo uporabili podjetje Geberit proizvodnja d. o. o., ki je vodilno podjetje v sanitarni tehniki. Osrednja tema oziroma naloga tega dela je, primerjava opravljanja managementskih funkcij v profitnih in neprofitnih organizacijah. Tukaj se bomo posvetili vsaki funkciji posebej in navedli razlike. Glavna ugotovitev te naloge je, ugotovitev razlik med managentskimi funkcijami v obeh primerih organizacije. Kje se pojavlja največ in najmanj razlik in podobnosti.
Keywords: Managementske funkcije, profitne organizacije, neprofitne organizacije, primerjava funkcij.
Published in DKUM: 28.10.2021; Views: 902; Downloads: 66
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10.
Povezanost organizacijske kulture podjetja in osebnosti zaposlenih
Rok Švarc, 2021, master's thesis

Abstract: V pričujočem magistrskem delu iščemo odgovor na vprašanji, ali organizacijska kultura vpliva na osebnost zaposlenih ter ali osebnost zaposlenih vpliva na organizacijsko kulturo. V prvem delu magistrskega dela razdelamo pojma organizacijske kulture in osebnosti. Organizacijska kultura je celovit sistem vrednot, norm, prepričanj, predstav in simbolov, ki določa na kak način se bodo vsi zaposleni obnašali in odzivali na probleme. Tvori jo zunanja plast, ki predstavlja vidne sestavine organizacijske kulture (legende, rituali, jezik, simboli) in nevidna plast (norme, vrednote, temeljne predpostavke). Funkcije organizacijske kulture so preprečevanje konfliktnih situacij, koordinacija in nadzor, povečanje motivacije, zmanjšanje negotovosti in konkurenčna prednost. Opisali smo več teorij, na podlagi katerih opredelimo tipe organizacijske kulture. To je Hofstedov model, Handyjeva tipologija, Dealova in Kennedyjeva tipologija in Ansoffova tipologija. Prav tako opišemo, kako se organizacijska kultura spreminja. Osebnost je celovit sistem relativno trajnih duševnih, vedenjskih in telesnih značilnosti, po katerih se razlikujemo med seboj. Osebnost tako zajema duševne značilnosti (osebnostne lastnosti, značilnosti duševnih procesov), telesne značilnosti (značilnosti telesnega videza, značilnosti bioloških procesov) in vedenjske značilnosti, zato se osebnost tudi definira kot psihofizična celota. Dejavniki, ki najbolj vplivajo na človekovo osebnost so dedni dejavniki, družinski dejavniki, kulturni dejavniki, družbeni dejavniki, pomembna pa je tudi samodejavnost. Najpomembnejše teorije osebnosti so Freudova teorija osebnosti, Allportova teorija osebnosti ter socialne teorije osebnosti. Med področja osebnostne strukture uvrščamo temperament, značaj, sposobnosti ter telesne značilnosti. Tipe osebnosti zaposlenih delimo glede na različne kategorije: glede na temperament razločujemo med sangvinikom, flegmatikom, melanholikom in kolerikom, glede na izbrane osebne pa so pomembni lokus kontrole, makiavelizem, samoučinkovitost in kreativnost. Prav tako lahko tipe zaposlenih delimo na 5 temeljnih dimenzij osebnosti in pri tem razločujemo med naslednjimi tipi: ekstravertnost, prijetnost, vestnost, nevroticizem in odprtost do sprememb. Organizacijska kultura vpliva na oblikovanje stališč in pogledov zaposlenih, stopnjo inovativnosti, motiviranosti in številne druge in s tem vpliva na določene segmente osebnosti. Tudi osebnost vpliva na organizacijsko kulturo podjetja. Ob ustanovitvi organizacije je organizacijska kultura odraz njenih ustanoviteljev. Ko organizacija raste, postane organizacijska kultura sestavljena iz skupka vseh osebnosti zaposlenih. Organizacija prenaša organizacijsko kulturo in tako spreminja svoje zaposlene v procesu socializacije. V procesu socializacije, ki je lahko usmerjena institucionalno ali individualno, se tako zaposleni seznanijo s prevladujočimi vrednotami in normami organizacije in jih prevzamejo. Organizacijska kultura tako vpliva na spremembe posameznikov in pridobivanje novih osebnostnih lastnosti, vendar so te manjše in niso tako velike, da bi se spremenila celotna osebnostna struktura posameznikov. Tudi osebnost zaposlenih spreminja organizacijsko kulturo, saj vsako njihovo spreminjanje organizacijske kulture, ne glede na to, ali organizacijsko kulturo spreminja vodstvo ali pa zaposleni, izhaja prav iz njihovih sposobnostih, značaja, pa tudi temperamenta.
Keywords: organizacijska kultura, osebnost, vpliv osebnosti na organizacijsko kulturo, vpliv organizacijske kulture na osebnost
Published in DKUM: 05.07.2021; Views: 1262; Downloads: 178
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