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41.
Household and road dust as indicators of airborne particulate matter elemental composition : dissertation
Klemen Teran, 2020, doctoral dissertation

Abstract: Household dust (HD) and road dust (RD) are widespread and easily accessible urban sediments, which are influenced by deposition of airborne particulate matter (PM). Since airborne PM is considered to be one of the most important pollutants in urban areas, with significant adverse effects on human health, a better understanding of its elemental composition and dispersion mechanisms is needed. The present study examines whether the HD and RD elemental composition can be used as a quick alternative method for the determination of corresponding PM elemental composition over a selected area. In summer 2016, HD, RD, and topsoil samples were collected from 249 sampling locations distributed across rural, urban, and industrial areas in Slovenia. The collected samples were sieved for particle diameters below 63 μm and analysed for 53 elements with ICP-MS after aqua regia digestion. SEM/EDS analyses were applied for the determination of characteristic particles at the microlevel. Finally, the elemental composition of HD and RD was compared with the PM10 elemental composition obtained from National Network for Ambient Air Quality Monitoring governed by Slovenian Environmental Agency (ARSO) to determine any potential connection between them. The results show that HD and RD are considerably enriched with a large set of elements compared to the topsoil. Correlations and factor analyses show that spatial distribution of factor scores in RD revealed strong regional trends, connected with soil resuspension (Al, Ce, Ga, K, La, Li, P, Rb, Sc and Y) or with anthropogenic sources such as traffic (Ag, Bi, Cu, Sb and Sn), steel mill emissions (Cr, Mo, Mn, Ni and W) and construction material decomposition (Ca and Sr). In contrast, HD elemental composition was highly variable between sampling locations. Variability was probably caused by indoor sources, such as smoking (Ce and La), biomass combustion (K, P and Rb), construction material decomposition (Ca and Sr) and residents’ professional occupation: dental care employees (Ag, Au, Pd) and employees in the metal-processing industry (Cr, Mo, Ni). Among deposited particles in RD, urbanization processes, such as fossil fuel combustion and traffic emissions, including brake pad abrasion and tyre wear, contributed the largest share of particles with anomalous elemental composition. Brake pad abrasion, for instance, contributed Ba-, Cu-, Sn-, and Zn-enriched irregular, angular and tabular particles, while tyre wear produced elongated rubber particles with traces of Ba, Cu, and Zn. RD from urban areas showed significantly higher elemental levels of Ag, Bi, Ca, Cd, Cr, Cu, Hg, Fe, Mo, Nb, Pb, Pt, Sb, Sn, Sr, Ti, Zn, and W in comparison to the rural environment, indicating the strong impact of urbanization on RD elemental composition. Another important anthropogenic source of deposited particles in RD were steel mills. Strong anomalies of Cr, Mo and Ni were detected in their vicinity. Their elemental levels decreased with distancing from the plan location, reaching urban background levels between 15 and 20 km from the mills. SEM/EDS analyses identified enrichments of Cr, Mn, Mo, Ni, V, and W in spherical particles and particles with partially melted surfaces, which were found only in the proximity of steel mills, indicating their influence of the PM deposition. Comparison of RD and the corresponding PM10 elemental composition showed that the RD fraction with particle diameters below 63 μm reflects PM10 elemental composition for the last 30 to 90 days for Cr, Cu, Mo and Zn and can be used as a predictor for PM10 elemental levels. This is not true for HD, as indoor particle sources prevail over the deposition of ambient PM10.
Keywords: household dust, road dust, particulate matter, PM10, pollution, Slovenia, steel mills, topsoil, traffic, urbanization
Published in RUNG: 02.12.2020; Views: 3798; Downloads: 186
.pdf Full text (17,40 MB)

42.
Optical setup for two-colour experiments at the low density matter beamline of FERMI
Paola Finetti, Giovanni De Ninno, 2017, original scientific article

Keywords: Oprics, low-density matter, free-electron laser
Published in RUNG: 27.10.2020; Views: 2382; Downloads: 0
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43.
Slow interatomic Coulombic decay of multiply excited neon clusters
Denis Iablonskyi, Giovanni De Ninno, 2016, original scientific article

Abstract: Ne clusters (∼ 5000 atoms) were resonantly excited (2 p→ 3 s) by intense free electron laser (FEL) radiation at FERMI. Such multiply excited clusters can decay nonradiatively via energy exchange between at least two neighboring excited atoms. Benefiting from the precise tunability and narrow bandwidth of seeded FEL radiation, specific sites of the Ne clusters were probed. We found that the relaxation of cluster surface atoms proceeds via a sequence of interatomic or intermolecular Coulombic decay (ICD) processes while ICD of bulk atoms is additionally affected by the surrounding excited medium via inelastic electron scattering. For both cases, cluster excitations relax to atomic states prior to ICD, showing that this kind of ICD is rather slow (picosecond range). Controlling the average number of excitations per cluster via the FEL intensity allows a coarse tuning of the ICD rate.
Keywords: Clusters, low-denisty matter, free-electron laser
Published in RUNG: 27.10.2020; Views: 2153; Downloads: 0
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44.
45.
A study of stellar debris dynamics during a tidal disruption event
Aurora Clerici, 2020, doctoral dissertation

Abstract: The number of observed tidal disruption events is increasing rapidly with the advent of new surveys. Thus, it is becoming increasingly important to improve TDE models using different stellar and orbital parameters. We study the dynamical behaviour of tidal disruption events produced by a massive black hole like Sgr A* by changing different initial orbital parameters, taking into account the observed orbits of S stars. Investigating different types of orbits and penetration factors is important since their variations lead to different timescales of the tidal disruption event debris dynamics, making mechanisms such as self-crossing and pancaking act strongly or weakly, thus affecting the circularisation and accretion disk formation. We have performed smoothed particle hydrodynamics simulations. Each simulation consists in modelling the star with $10^5$ particles, and the density profile is described by a polytrope with $\gamma$ = 5/3. The massive black hole is modelled with a generalised post-Newtonian potential, which takes into account relativistic effects of the Schwarzschild space-time. Our analyses find that mass return rate distributions of solar-like stars and S-like stars with same eccentricity have similar durations, but S-like stars have higher mass return rate, as expected due to their larger mass. Regarding debris circularisation, we identify four types of evolution, related to the mechanisms and processes involved during circularisation: in type 1 the debris does not circularise efficiently, hence a disk is not formed or is formed after relatively long time; in type 2 the debris slowly circularises and eventually forms a disk with no debris falling back; in type 3 the debris relatively quickly circularises and forms a disk while there is still debris falling back; finally, in type 4 the debris quickly and efficiently circularises, mainly through self-crossings and shocks, and forms a disk with no debris falling back. Finally, we find that the standard relation of circularisation radius $r_{\rm circ} = 2r_{\rm t}$ holds only for $\beta = 1$ and eccentricities close to parabolic.
Keywords: 07.05.Tp Computer modeling and simulation, 95.30.Lz Hydrodynamics, 98.35.Jk Galactic center, bar, circumnuclear matter, and bulge, 98.62.Js Galactic nuclei (including black holes), circumnuclear matter, and bulges, 98.62.Mw Infall, accretion, and accretion disks
Published in RUNG: 29.09.2020; Views: 3681; Downloads: 78
.pdf Full text (37,55 MB)

46.
The new instrument using a TC–BC (total carbon–black carbon) method for the online measurement of carbonaceous aerosols
Martin Rigler, Luka Drinovec, Gašper Lavrič, Anastasia Vlachou, André S. H. Prévôt, Jean-Luc Jaffrezo, Iasonas Stavroulas, Jean Sciare, Judita Burger, Irena Krajnc, Janja Turšič, Anthony D. A. Hansen, Griša Močnik, 2020, original scientific article

Abstract: We present a newly developed total carbon analyzer (TCA08) and a method for online speciation of carbonaceous aerosol with a high time resolution. The total carbon content is determined by flash heating of a sample collected on a quartz-fiber filter with a time base between 20 min and 24 h. The limit of detection is approximately 0.3 µg C, which corresponds to a concentration of 0.3 µg C m−3 at a sample flow rate of 16.7 L min−1 and a 1 h sampling time base. The concentration of particulate equivalent organic carbon (OC) is determined by subtracting black carbon concentration, concurrently measured optically by an Aethalometer®, from the total carbon concentration measured by the TCA08. The combination of the TCA08 and Aethalometer (AE33) is an easy-to-deploy and low-maintenance continuous measurement technique for the high-time-resolution determination of equivalent organic and elemental carbon (EC) in different particulate matter size fractions, which avoids pyrolytic correction and the need for high-purity compressed gases. The performance of this online method relative to the standardized off-line thermo-optical OC–EC method and respective instruments was evaluated during a winter field campaign at an urban background location in Ljubljana, Slovenia. The organic-matter-to-organic-carbon ratio obtained from the comparison with an aerosol chemical speciation monitor (ACSM) was OM/OC=1.8, in the expected range.
Keywords: total carbon, aeroosl, black carbon, carbonaceous matter
Published in RUNG: 17.08.2020; Views: 2975; Downloads: 76
.pdf Full text (226,45 KB)

47.
Search for Axionlike-Particle-Induced Prompt γ -Ray Emission from Extragalactic Core-Collapse Supernovae with the Fermi Large Area Telescope
Manuel Meyer, Tanja Petrushevska, 2020, original scientific article

Abstract: During a core-collapse supernova (SN), axionlike particles (ALPs) could be produced through the Primakoff process and subsequently convert into γ rays in the magnetic field of the Milky Way. We do not find evidence for such a γ-ray burst in observations of extragalactic SNe with the Fermi Large Area Telescope (LAT). The SN explosion times are estimated from optical light curves and we find a probability of about ∼90% that the LAT observed at least one SN at the time of the core collapse. Under the assumption that at least one SN was contained within the LAT field of view, we exclude photon-ALP couplings ≳2.6×10−12 GeV−1 for ALP masses ma≲3×10−10 eV, improving previous limits from SN1987A by a factor of 2.
Keywords: darn matter, axions, axion-like particles, core-collapse supernovae
Published in RUNG: 15.06.2020; Views: 2629; Downloads: 77
.pdf Full text (30,47 MB)

48.
Towards ultrafast X-ray condensed matter physics with MHz repetition rate HHG sources
Jurij Urbančič, 2015, published scientific conference contribution abstract

Abstract: In recent years, an increasing number of ultrafast material science experiments are based on the use of table-top high-harmonic generation (HHG) lightsources [1,2]. Despite the huge success of these first experiments, a major drawback has been the limited repetition rate of these lightsources, in particular with respect to all types of photoemission experiments. Here, we combine newly developed high-repetition rate HHG sources [3,4] with state-of-the-art element-specific magneto-optical Kerr experiments. The chances and prospects for future ultrafast materials science experiments with these lightsources will be discussed.
Keywords: High Harmonic Generation, X-Rays, Condensed Matter
Published in RUNG: 22.05.2020; Views: 3314; Downloads: 0

49.
The Dark Side of the Matter
Gabrijela Zaharijas, 2019, other component parts

Keywords: Dark matter, cosmology
Published in RUNG: 17.05.2020; Views: 2855; Downloads: 0
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50.
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