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21.
22.
New air fluorescence detectors employed in the Telescope Array experiment
H. Tokuno, Jon Paul Lundquist, 2012, izvirni znanstveni članek

Opis: Since 2007, the Telescope Array (TA) experiment, based in Utah, USA, has been observing ultra high energy cosmic rays to understand their origins. The experiment includes a surface detector (SD) array and three fluorescence detector (FD) stations. The FD stations, installed surrounding the SD array, measure the air fluorescence light emitted from extensive air showers (EASs) for precise determination of their energies and species. The detectors employed at one of the three FD stations were relocated from the High Resolution Fly's Eye (HiRes) experiment. At the other two stations, newly designed detectors were constructed for the TA experiment. An FD consists of a primary mirror and a camera equipped with photomultiplier tube pixels. To obtain the EAS parameters with high accuracy, understanding the FD optical characteristics is important. In this paper, we report the characteristics and installation of the new FDs and the performances of the FD components. The results of the monitored mirror reflectance during the observation time are also described in this report.
Ključne besede: Ultra high energy cosmic rays, Extensive air showers, Air fluorescence light detectors
Objavljeno v RUNG: 19.05.2020; Ogledov: 2423; Prenosov: 0
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23.
SnO2-Containing Clinoptilolite as a Composite Photocatalyst for Dyes Removal fromWastewater under Solar Light
Andraž Šuligoj, Jelena Pavlovič, Iztok Arčon, Nevenka Rajić, Nataša Novak Tušar, 2020, izvirni znanstveni članek

Opis: Due to their adsorbent, ion exchange and catalytic properties zeolites are suitable for a variety of applications. We report on the photocatalytic activity of a readily available and inexpensive natural zeolite clinoptilolite (Z) containing SnO2 (Sn-Z). The Sn-Z samples with 3–15 wt. % of Sn were prepared by using a precipitation–deposition method. Powder X-ray diffraction analysis showed that the zeolite structure was unaffected by the introduction of the Sn-phase. Diffuse reflectance UV/VIS spectra of the Sn-Z samples confirmed the presence of SnO2 and X-Ray absorption spectroscopy analyses suggested that the SnO2 particles mainly resided on the surface of the clinoptilolite, while ATR-FTIR analysis gave some clues that part of the SnO2 phase was incorporated in the pores of the zeolite. The presence of SnO2 in Sn-Z increased both adsorption capacity and photocatalytic performance which could be partially explained by higher surface area and partially with an increased negative potential of the surface. Adsorption and total degradation of methylene blue (MB) for the Sn-Z with the highest amount of Sn (15 wt.%) was about 30% and 45%, respectively, suggesting a synergetic effect between SnO2 and the clinoptilolite lattice. Reusability tests showed that these catalysts present a promising material for water purification.
Ključne besede: SnO2, zeolite, SnO2-clinoptilolite composite, photocatalysis, solar light, methylene blue removal, wastewater treatment
Objavljeno v RUNG: 25.02.2020; Ogledov: 2902; Prenosov: 131
.pdf Celotno besedilo (3,50 MB)

24.
25.
First attempt to start fighting light pollution in Macedonia
Tanja Petrushevska, Andrej Mohar, 2018, objavljeni povzetek znanstvenega prispevka na konferenci (vabljeno predavanje)

Ključne besede: light pollution, Macedonia
Objavljeno v RUNG: 14.01.2019; Ogledov: 2960; Prenosov: 14
URL Povezava na celotno besedilo
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26.
A gamma-ray determination of the Universe ’ s star formation history
Gabrijela Zaharijas, Marco Ajello, 2018, izvirni znanstveni članek

Ključne besede: gamma rays, Fermi LAT, Extragalactic Background LIght
Objavljeno v RUNG: 05.12.2018; Ogledov: 3061; Prenosov: 0
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27.
FIRST EFFORT TO FIGHT LIGHT POLLUTION IN MACEDONIA
Tanja Petrushevska, 2018, strokovni članek

Opis: Light pollution is a serious problem in majority of European countries, with negative effects on the environment, animal life and human health. Not only light pollution is causing unnecessary electricity consumption, it also prevents the citizens to enjoy the dark night sky. Following the experience in Slovenia and Friuli Venezia Giulia, Italy with approaching this problem, we proposed a joined effort to perform field measurements of the light pollution, increase the awareness of this issue to the public and the policy makers in Macedonia. Light pollution is a very interdisciplinary field that necessitates the collaboration of policy makers, environmentalist, amateur and professional astronomers. The proposal was submitted to proESOF initiative in Trieste, Italy. This initiative consists of the organisation of collaborative events in North East Italy and the Balkan countries where the objective is to spread science for the benefit to the citizens. ProESOF events will happen before 2020, after which the main event “Trieste – European City of Science” will follow. Our proposal has been positively judged by the proESOF evaluators, and currently we are waiting for their decision regarding the financial support they will provide. The first step will to train a group of people to perform field measurements of light pollution. The second step is to share these results, so the target is the general public in Macedonia. To successfully fight light pollution, anti-light pollution laws have to be made and enforced, so relevant politicians and law makers in Macedonia will be included. We will use the local team who has experience and contacts with the media, so that this event gets covered well. This will be a first meeting of this kind in Skopje, Macedonia which will join experts of the region and offer new ideas to fight light pollution in Macedonia and the Balkans. Macedonia is one of the few countries that is lacking any initiative when it comes to light pollution. It is very important to act timely, also because in Macedonia there are still some regions with dark sky that can be saved. Italy and Slovenia have collaborated previously on several occasion regarding light pollution: the purpose of the project Public Lighting of the Future that was running from 2011 to 2014 was to create a common methodology and database. After our proposed workshop and measurement, the aim will be to include Macedonia in this common effort to fight light light pollution.
Ključne besede: light pollution
Objavljeno v RUNG: 11.09.2018; Ogledov: 2944; Prenosov: 0
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28.
Amorphous nanocomposite of polycarbosilanes and aluminum oxide
Andraž Mavrič, 2018, doktorska disertacija

Opis: This work presents a paradigm for high temperature stabilization of bulk amorphous aluminium oxide. The thermodynamic stabilization is achieved by preparing a nanocomposite, where polymethylsilane dendritic molecules are dispersed in an aluminium hydroxide gel. Upon heat-treatment the gel transforms to the amorphous aluminium oxide that is stable up to 900°C. The dispersion of the macromolecules and their covalent bonding to the alumina matrix induce homogeneously distributed strain fields that keep the alumina amorphous. The first part of the thesis focuses on the synthesis, characterization and solubility properties of the dendritic polymethylsilane. The polymethylsilane is synthetized by electrochemical polymerization from trichloromethylsilane monomer. The polymerization mechanism, involving a single polymerization pathway, is identified. The polymer growth proceeds through reduction of the monomers to the silyl anions and their addition to the growing polymer. The solubility of three chemically related but topologically different polysilanes (linear, dendritic and network) were studied by dynamic light scattering. At room temperature the agglomerates in a range from 500 to 1300 nm are present. They undergo de-agglomeration at slightly elevated temperatures of around 40°C. The de-agglomeration results in formation of stable solutions, where a hydrodynamic diameter of the individual polymer molecules was measured to be in a range from 20 to 40 nm. The obtained diameters of two dendritic polymethylsilane macromolecules, synthesized under different electrolysis conditions, are much larger than the theoretical size estimated for an ideal dendrimer. We determined by 29Si NMR that the reason for this is in a large number of branching irregularities (defects) contained in the molecular structure. Combining the experimental values obtained by DLS and density measurements with a structural model that considers the branching irregularities, it is shown that the inclusion of the defects allows the dendritic polymer to exceed the sterical limitations and form the hyperbranched dendritic structure. The final size depends on a relative amount of the branching defects. In the second part, the synthetized polymethylsilane molecules were successfully used for the nanocomposite formation. The aluminium hydroxide gel with the dispersed polymethylsilane molecules was prepared as a precursor. Upon heat-treatment it gives the amorphous aluminium oxide stable up to 900°C. The dispersed macromolecules induce homogeneously distributed strain fields that keep the aluminium oxide amorphous during the thermal treatment the dispersed macromolecules covalently bind to the matrix, inducing the interface strain. The amorphous state was confirmed by the presence of penta-coordinated aluminium detected by 27Al NMR and a low bandgap measured by UV-vis absorption spectroscopy.
Ključne besede: amorphous aluminium oxide, polymethylsilane, nanocomposite, electropolymerization, solubility, agglomeration, de-agglomeration, dendrimer, hyperbranched dendritic structure, dynamic light scattering, thermal analysis, transmission electron microscopy, scanning electron microscopy, X-ray diffraction, infrared spectroscopy, UV-Vis spectroscopy
Objavljeno v RUNG: 19.07.2018; Ogledov: 6010; Prenosov: 210
.pdf Celotno besedilo (5,07 MB)

29.
Surface modified titanium dioxide using transition metals : nickel as a winning transition metal for solar light photocatalysis
Andraž Šuligoj, Iztok Arčon, Matjaž Mazaj, Goran Dražić, Denis Arčon, Pegie Cool, Urška Lavrenčič Štangar, Nataša Novak Tušar, 2018, izvirni znanstveni članek

Opis: Titanium dioxide has been widely used as an antimicrobial agent, UV-filter and catalyst for pollution abatement. Herein, surface modifications with selected transition metals (Me) over colloidal TiO2 nanoparticles and immobilization with a colloidal SiO2 binder as composite films (MeTiO2/SiO2) on a glass carrier were used to enhance solar-light photoactivity. Colloidal TiO2 nanoparticles were modified by loading selected transition metals (Me ¼ Mn, Fe, Co, Ni, Cu, and Zn) in the form of chlorides on their surface. They were present primarily as oxo-nanoclusters and a portion as metal oxides. The structural characteristics of bare TiO2 were preserved up to an optimal metal loading of 0.5 wt%. We have shown in situ that metal-oxo-nanoclusters with a redox potential close to that of O2/O2 were able to function as co-catalysts on the TiO2 surface which was excited by solar-light irradiation. The materials were tested for photocatalytic activity by two opposite methods; one detecting O2 (reduction, Rz ink test) while the other detecting OH (oxidation, terephthalic acid test). It was shown that the enhancement of the solar-light activity of TiO2 by the deposition of transition metal oxo-nanoclusters on the surface depends strongly on the combination of the reduction potential of such species and appropriate band positions of their oxides. The latter prevented excessive self-recombination of the photogenerated charge carriers by the nanoclusters in Ni and Zn modification, which was probably the case in other metal modifications. Overall, only Ni modification had a positive effect on solar photoactivity in both oxidation and reduction reactions.
Ključne besede: surface modified TiO2, XANES, EXAFS, Nickel, solar light photocatalyst
Objavljeno v RUNG: 01.06.2018; Ogledov: 3421; Prenosov: 0
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30.
Polymer Nanoparticle Sizes from Dynamic Light Scattering and Size Exclusion Chromatography: The Case Study of Polysilanes.
Artem Badasyan, Andraž Mavrič, Irena Kralj Cigić, Tim Bencik, Matjaž Valant, 2018, izvirni znanstveni članek

Opis: Dynamic Light Scattering (DLS) and Size Exclusion Chromatography (SEC) are among the most popular methods for determining polymer sizes in solution. Taking dendritic and network polysilanes as a group of least soluble polymer substances, we critically compare and discuss the difference between nanoparticle sizes, obtained by DLS and SEC. Polymer nanoparticles are typically in poor solution conditions below the theta point and are in globular conformation therefore. Determination of particle sizes in presence of attractive interactions is not a trivial task. The only possibility to measure aggregation-free, a true molecular size of polymer nanoparticles in such regime of solution, is to operate with the dilute solution of globules (below theta point and above the miscibility line). Basing on results of our polysilane measurements, we come to a conclusion that DLS provides more reliable results than SEC for the dilute solution of globules. General implications for the size measurements of polymer nanoparticles in solutions are discussed.
Ključne besede: Polymer Nanoparticle, Dynamic Light Scattering, Size Exclusion Chromatography, Polysilanes
Objavljeno v RUNG: 16.05.2018; Ogledov: 4203; Prenosov: 16
.pdf Celotno besedilo (3,17 MB)

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