1811. Zagotavljanje in preverjanje kakovosti v mamografijiUrban Zdešar, 1998, review article Abstract: Mamografija je zaradi specifičnih lastnosti sprememb v dojki, ki jih poskušamoodkriti, tehnično ena najbolj zahtevnih radioloških preiskav. Kakovostna mamografija ne pomeni samo dobrega mamograma temveč tudi čim nižjo možno dozo sevanja, ki jo pri preiskavi prejme preiskovana dojka. Zato kriteriji za ocenjevanje kakovosti poleg diagnostičnih zahtev vsebujejo tudi kriterije, ki se nanašajo na obsevanost pacientk. Osnovni pogoji za kakovostnoizvajanje mamografije so izurjeno osebje, ustrezna oprema in dobra organiziranost. Sem sodi tudi program preverjanja kakovosti. Ta je v prvi vrsti namenjen zdravniku, ki mu informacije s slike pomagajo določiti diagnozo. Nekatere parametre kakovosti lahko preverjamo kar na samih mamogramih, fizikalno-tehnične parametre, ki najbolj vplivajo tako na kakovostslik kot tudi na prejeto dozo, pa preverjamo z rednimi poizkusi posameznih delov mamografskega diagnostičnega sistema. V prispevku je opisanihnekaj preprostih preskusov, ki naj bi se izvajali pogosteje (dnevno, tedensko), in našteta oprema, ki bi jo za to potrebovali.
Published in DiRROS: 22.11.2023; Views: 296; Downloads: 117
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1812. Tehnologija mamografijLucijan Miklavčič, 1998, review article Abstract: Za optimatizacijo tehnologije v mamografiji je potrebno kvantitativno preverjanje, ki ga mora obvladati radiolog. Menim, da marsikateri radiolog, kise ukvarja z mamografijo ne pozna zadovoljivo tega dela stroke. V prispevku so bile pregledno nakazane le tiste osnove, ki so po mojem mnenju najpomembnejše; nekatera področja so bila zaradi prostorske stiske namenoma izpuščena (priprave za kompresijo in pozicioniranje, naprava za avtomatsko ekspozicijo v radiografiji, kontrola in zagotavljanje kvalitete mamografa). Zapoglobitev osnov in za specifične tehnične rešitve se moramo posluževati s sodobnimi strokovnimi viri, ki so bogato zastopani v strokovni literaturi.
Published in DiRROS: 22.11.2023; Views: 290; Downloads: 83
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1813. Hydrothermal synthesis of rare-earth modified titania : influence on phase composition, optical properties, and photocatalytic activityNejc Rozman, David Maria Tobaldi, Uroš Cvelbar, Harinarayanan Puliyalil, Joao Antonio Labrincha, Andraž Legat, Andrijana Sever Škapin, 2019, original scientific article Abstract: In order to expand the use of titania indoor as well as to increase its overall performance, narrowing the band gap is one of the possibilities to achieve this. Modifying with rare earths (REs) has been relatively unexplored, especially the modification of rutile with rare earth cations. The aim of this study was to find the influence of the modification of TiO2 with rare earths on its structural, optical, morphological, and photocatalytic properties. Titania was synthesized using TiOSO4 as the source of titanium via hydrothermal synthesis procedure at low temperature (200 °C) and modified with selected rare earth elements, namely, Ce, La, and Gd. Structural properties of samples were determined by X-ray powder diffraction (XRD), and the phase ratio was calculated using the Rietveld method. Optical properties were analyzed by ultraviolet and visible light (UV-Vis) spectroscopy. Field emission scanning electron microscope (FE-SEM) was used to determine the morphological properties of samples and to estimate the size of primary crystals. X-ray photoelectron spectroscopy (XPS) was used to determine the chemical bonding properties of samples. Photocatalytic activity of the prepared photocatalysts as well as the titania available on the market (P25) was measured in three different setups, assessing volatile organic compound (VOC) degradation, NOx abatement, and water purification. It was found out that modification with rare earth elements slows down the transformation of anatase and brookite to rutile. Whereas the unmodified sample was composed of only rutile, La- and Gd-modified samples contained anatase and rutile, and Ce-modified samples consisted of anatase, brookite, and rutile. Modification with rare earth metals has turned out to be detrimental to photocatalytic activity. In all cases, pure TiO2 outperformed the modified samples. Cerium-modified TiO2 was the least active sample, despite having a light absorption tail up to 585 nm wavelength. La- and Gd-modified samples did not show a significant shift in light absorption when compared to the pure TiO2 sample. The reason for the lower activity of modified samples was attributed to a greater Ti3+/Ti4+ ratio and a large amount of hydroxyl oxygen found in pure TiO2. All the modified samples had a smaller Ti3+/Ti4+ ratio and less hydroxyl oxygen
Keywords: TiO2, photocatalytic activity, rare earths, modification, visible light activity
Published in DiRROS: 22.11.2023; Views: 397; Downloads: 184
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1814. Particle size manipulation as an influential parameter in the development of mechanical properties in electric arc furnace slag-based AAMKatja Traven, Mark Češnovar, Vilma Ducman, 2019, original scientific article Abstract: Alkali-activated materials (AAM) have gained recognition as a promising alternative to technical ceramic and building materials owing to the lower energy demands for production and the potential to use slag as a precursor. In the present study, five sets of slag-based AAM pastes were prepared with different particle sizes (fractions d < 63, 63 < d < 90, and 90 < d < 125 μm in different mass ratios) under the same curing regime and using a fixed precursor to activator (water) mass ratio. Precursors and the hardened AAM are evaluated using BET, XRD, XRF, SEM, FTIR, reactivity of precursors by leaching, and mercury intrusion porosimetry (MIP). Chemical analysis indicated only marginal differences among the different-sized fractions of input materials, whereas the BET surface area and reactivity among the precursors differed significantly-smaller particles had the largest surface area, and thus, higher reactivity. The mineralogical differences between the precursors and hardened AAM were negligible. The results revealed that compressive strength was significantly influenced by particle size, i.e., a threefold increase in strength when the particle size was halved. Microstructural evaluation using MIP confirmed that the porosity was the lowest in AAM with the smallest particle size. The low porosity and high reactivity of the fine fractions led to the highest compressive strength, confirming that manipulation of particle size can significantly influence the mechanical properties.
Keywords: alkalijsko aktivirani materiali, žlindra iz obločne peči, mehanska aktivacija, mehanske lastnosti, poroznost, alkali-activated materials (AAM), electric arc furnace steel slag, mechanical activation, mechanical properties, porosity
Published in DiRROS: 22.11.2023; Views: 407; Downloads: 172
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1815. The role of relative humidity on crystallization of calcium carbonate from calcium acetoacetate precursorAndreja Pondelak, Francesca Rosi, Celeste Maurich, Costanza Miliani, Srečo D. Škapin, Andrijana Sever Škapin, 2019, original scientific article Abstract: Calcium acetoacetate, Ca(OAcAc)2, was exposed 7, 30 and 365 days to different values of relative humidity (33%, 48%, 75% and 96%) at 40 °C in order to study its transformation to CaCO3. The resulting Ca(OAcAc)2 decomposition and the time dependence of the phase transformations were monitored and critically evaluated by Fourier transform infrared spectroscopy, field emission scanning electron microscopy and X-ray powder diffraction. The impact of relative humidity on CaCO3 polymorph formation was thoroughly assessed. In all of the conditions used and for all ageing periods, the formed crystal structure is found to be vaterite. At the lowest relative humidity (33%), the amorphous CaCO3 remains more or less almost untransformed even after one year of exposure. It is proposed that the reason for the stability of amorphous CaCO3 is due to the limited amount of physisorbed water on the surfaces of the particles, which is considered the driving force for its transformation. However, the carbonation process is faster in the case of the highest humidity (96%). The findings are not only important for better solutions in the field of cultural heritage, but also shed new light on the fundamental mechanism of CaCO3 crystallization.
Keywords: calcium acetoacetate, relative humidity, carbonation, amorphous carbonate, vaterite, mechanism
Published in DiRROS: 22.11.2023; Views: 502; Downloads: 204
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1816. Epidemiologija raka dojk in presejanjeMaja Primic-Žakelj, Vera Pompe-Kirn, 1998, review article Abstract: Rak dojk je v Sloveniji najpogostejši rak pri ženskah. Leta 1995 je za njim zbolelo 784 žensk (76,7/100.000), pričakujemo pa , da se bo v prihodnjih desetih letih incidenca še večala. Delež rakov, odkritih v omejenem stadiju se povečuje; leta 1995 je bilo takih 44% vseh primerov. Čeprav se je preživetjolnic izboljšalo (67-odstotno 5-letno relativno preživetje bolnic z rakritim v letih 1988-92), ostaja rak dojk pri ženskah na prvem mestu med vzroki smrti zaradi raka. Med dikazane nevarnostne dejavnike sodijo poleg spola in starosti še poprejšnji rak dojk , nekatere benigne bolezni dojk, družinska obremenitev, ionizirajoče sevanje, nekateri reproduktivni dejavniki in debelost. V primarni preventivi zaenkrat ni posebnih priporočil, so le splošna: vzdrževanje normalne telesne teže, pravilna prehrana, telesna dejavnost in zmernost pri pitju alkoholnih pijač. Ocenjujejo, da presejanje, redno mamografsko pregledovannje žensk po 50. letu starosti z dodatnim kliničnim pregledom ali brez njega, zmanjša umrljivost za rakom dojk med pregledanimi za okrog 30%. Populacijsko presejanje priporočajo večinoma po 50.letu starosti. Problem raka dojk je mogoče reševati celostno, s primarno preventivo, zgodnjim odkrivanjem in dostopnostjo do užinkovitega zdravljenja, predvsem pa z vlaganjem sredstev tja, kjer je razmerje med stroški in koristjonajugodnejše.
Published in DiRROS: 21.11.2023; Views: 319; Downloads: 123
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1819. Stanje slovenskih gozdov : poročilo o rezultatih nacionalne gozdne inventure 2022Mitja Skudnik, Luka Krajnc, Gal Kušar, Anže Martin Pintar, 2023, treatise, preliminary study, study Keywords: monitoring, nacionalna gozdna inventura, odmrla lesna biomasa, temeljnica, površina gozda, lesna zaloga, vzorčne ploskve, poročila
Published in DiRROS: 21.11.2023; Views: 443; Downloads: 0 |
1820. Discretionary capitalization of development expendituresPrimož Petek, Mateja Jerman, Sandra Janković, 2023, original scientific article Abstract: The paper examines the discretionary nature of (non)capitalizing development expenditures in financial statements. A review of the literature shows that companies may have different motives and factors for (non)capitalizing development expenditures. This study analyzes a sample of 547 companies from the information and communications technology (ICT) sector listed on the Frankfurt Stock Exchange in the period 2009-2018. The ICT sector was selected because it represents an industry with high R&D (research and development) expenditures. The results of the probit regression analysis made on 3,718 observations show that the capitalization of development expenditures is significantly positively related to the size and return on assets of the firm and negatively related to the age of the firm. Larger and more profitable firms are more likely to capitalize development expenditures, while older firms are less likely to capitalize development expenditures. Our results contribute to the literature in the field of positive accounting theory providing additional insights into factors associated with decisions to (non)capitalize development expenditures.
Keywords: capitalization, development expenditures, discretion, incentives, intangible assets
Published in DiRROS: 21.11.2023; Views: 354; Downloads: 225
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