1. Integrating in situ measurements and city scale modelling to assess the COVID–19 lockdown effects on emissions and air quality in Athens, GreeceGeorgios Grivas, Eleni Athanasopoulou, Anastasia Kakouri, Jennifer Bailey, Eleni Liakakou, Iasonas Stavroulas, Panayiotis Kalkavouras, Aikaterini Bougiatioti, Dimitris G. Kaskaoutis, Michel Ramonet, 2020, original scientific article Abstract: The lockdown measures implemented worldwide to slow the spread of the COVID–19 pandemic have allowed for a unique real-world experiment, regarding the impacts of drastic emission cutbacks on urban air quality. In this study we assess the effects of a 7-week (23 March–10 May 2020) lockdown in the Greater Area of Athens, coupling in situ observations with estimations from a meteorology-atmospheric chemistry model. Measurements in central Athens during the lockdown were compared with levels during the pre- and post-lockdown 3-week periods and with respective levels in the four previous years. We examined regulatory pollutants as well as CO2, black carbon (BC) and source-specific BC components. Models were run for pre-lockdown and lockdown periods, under baseline and reduced-emissions scenarios. The in-situ results indicate mean concentration reductions of 30–35% for traffic-related pollutants in Athens (NO2, CO, BC from fossil fuel combustion), compared to the pre-lockdown period. A large reduction (53%) was observed also for the urban CO2 enhancement while the reduction for PM2.5 was subtler (18%). Significant reductions were also observed when comparing the 2020 lockdown period with past years. However, levels rebounded immediately following the lift of the general lockdown. The decrease in measured NO2 concentrations was reproduced by the implementation of the city scale model, under a realistic reduced-emissions scenario for the lockdown period, anchored at a 46% decline of road transport activity. The model permitted the assessment of air quality improvements on a spatial scale, indicating that NO2 mean concentration reductions in areas of the Athens basin reached up to 50%. The findings suggest a potential for local traffic management strategies to reduce ambient exposure and to minimize exceedances of air quality standards for primary pollutants.
Keywords: pandemic, urban air pollution, traffic, chemical transport model, TAPM, mapping
Published in RUNG: 10.05.2024; Views: 1374; Downloads: 4
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2. Ambient carbonaceous aerosol levels in Cyprus and the role of pollution transport from the Middle EastAliki Christodoulou, Iasonas Stavroulas, Mihalis Vrekoussis, Maximillien Desservettaz, Michael Pikridas, Elie Bimenyimana, Jonilda Kushta, Matic Ivančič, Martin Rigler, Philippe Goloub, 2023, original scientific article Abstract: Abstract. The geographical origin and source apportionment of submicron carbonaceous aerosols (organic aerosols, OAs, and black carbon, BC) have been investigated here for the first time, deploying high time-resolution measurements at an urban background site of Nicosia, the capital
city of Cyprus, in the eastern Mediterranean. This study covers a half-year
period, encompassing both the cold and warm periods with continuous
observations of the physical and chemical properties of PM1 performed
with an Aerosol Chemical Speciation Monitor (ACSM), an aethalometer,
accompanied by a suite of various ancillary offline and online measurements. Carbonaceous aerosols were dominant during both seasons (cold and warm periods), with a contribution of 57 % and 48 % to PM1, respectively, and exhibited recurrent intense nighttime peaks (> 20–30 µg m−3) during the cold period, associated with local domestic heating. The findings of this study show that high concentrations of sulfate (close to 3 µg m−3) were continuously recorded, standing among the highest ever reported for Europe and originating from the Middle East region. Source apportionment of the OA and BC fractions was performed using the
positive matrix factorization (PMF) approach and the combination of two
models (aethalometer model and multilinear regression), respectively. Our
study revealed elevated hydrocarbon-like organic aerosol (HOA)
concentrations in Nicosia (among the highest reported for a European urban
background site), originating from a mixture of local and regional
fossil fuel combustion sources. Although air masses from the Middle East had
a low occurrence and were observed mostly during the cold period, they were
shown to strongly affect the mean concentrations levels of BC and OA in
Nicosia during both seasons. Overall, the present study brings to our
attention the need to further characterize primary and secondary
carbonaceous aerosols in the Middle East, an undersampled region
characterized by continuously increasing fossil fuel (oil and gas) emissions
and extreme environmental conditions, which can contribute to photochemical
ageing.
Keywords: PM1, BC, source apportionment, Cyprus, long range transport
Published in RUNG: 10.05.2024; Views: 891; Downloads: 6
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4. Measuring thermal diffusivity of azoheteroarene thin layers by photothermal beam deflection and photothermal lens methodsAmeneh Mikaeeli, Dorota Korte, Humberto Cabrera, Dariusz Chomicki, Dariusz Dziczek, Oksana Kharchenko, Peng Song, Junyan Liu, Andreas D. Wieck, Michal Pawlak, 2023, original scientific article Keywords: thin films, photothermal spectroscopy, thermal transport, thermal wave, thermal conductivity, thermal diffusivity
Published in RUNG: 21.09.2023; Views: 2216; Downloads: 6
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5. CR-ENTREES - Cosmic-Ray ENergy TRansport in timE-Evolving astrophysical SettingsAnita Reimer, Lukas Merten, Margot Boughelilba, Paolo Da Vela, Serguei Vorobiov, Jon Paul Lundquist, 2023, published scientific conference contribution Abstract: In order to understand observable signatures from putative cosmic-ray (CR) sources in-source
acceleration of particles, their energy and time-dependent transport including interactions in an
evolving environment and their escape from source have to be considered, in addition to sourceto-
Earth propagation.
We present the code CR-ENTREES (Cosmic-Ray ENergy TRansport in timE-Evolving astrophysical
Settings) that evolves the coupled time- and energy-dependent kinetic equations for cosmicray
nucleons, pions, muons, electrons, positrons, photons and neutrinos in a one-zone setup of
(possibly) non-constant size, with user-defined particle and photon injection laws. All relevant
interactions, particle/photon escape and adiabatic losses are considered in a radiation-dominated,
magnetized astrophysical environment that is itself evolving in time. Particle and photon interactions
are pre-calculated using event generators assuring an accurate interactions and secondary
particle production description. We use the matrix multiplication method for fast radiation and
particle energy transport which allows also an efficient treatment of transport non-linearities due
to the produced particles/photons being fed back into the simulation chain.
Examples for the temporal evolution of the non-thermal emission from AGN jet-like systems with
focus on proton-initiated pair cascades inside an expanding versus straight jet emission region, are
further presented.
Keywords: cosmic rays, CR energy transport, CR interactions
Published in RUNG: 24.08.2023; Views: 1808; Downloads: 4
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6. Efficient modeling of heavy cosmic rays propagation in evolving astrophysical environmentsLukas Merten, Paolo Da Vela, Anita Reimer, Jon Paul Lundquist, Margot Boughelilba, Serguei Vorobiov, J. Becker Tjus, 2023, published scientific conference contribution Abstract: We present a new energy transport code that models the time dependent and non-linear evolution
of spectra of cosmic-ray nuclei, their secondaries, and photon target fields. The software can inject
an arbitrary chemical composition including heavy elements up to iron nuclei. Energy losses and
secondary production due to interactions of cosmic ray nuclei, secondary mesons, leptons, or
gamma-rays with a target photon field are available for all relevant processes, e.g., photo-meson
production, photo disintegration, synchrotron radiation, Inverse Compton scattering, and more.
The resulting x-ray fluxes can be fed back into the simulation chain to correct the initial photon
targets, resulting in a non-linear treatment of the energy transport. The modular structure of the
code facilitates simple extension of interaction or target field models.
We will show how the software can be used to improve predictions of observables in various
astrophysical sources such as jetted active galactic nuclei (AGN). Since the software can model
the propagation of heavy ultrahigh-energy cosmic rays inside the source it can precisely predict
the chemical composition at the source. This will also refine predictions of neutrino emissions
–– they strongly depend on the chemical composition. This helps in the future to optimize the
selection and analyses of data from the IceCube neutrino observatory with the aim to enhance the
sensitivity of IceCube and reduce the number of trial factors.
Keywords: cosmic rays, low-luminosity jetted AGNCR energy transport, CR interactions
Published in RUNG: 24.08.2023; Views: 1623; Downloads: 5
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7. Time-of-flight photoconductivity investigation of high charge carrier mobility in ▫$Ti_3C_2T_x$▫ MXenes thin-filmJurij Urbančič, Erika Tomsic, Manisha Chhikara, Nadiia Pastukhova, Vadym Tkachuk, Alex Dixon, Andraž Mavrič, Payam Hashemi, Davood Sabaghi, Ali Shaygan Nia, Gvido Bratina, Egon Pavlica, 2023, original scientific article Abstract: Charge transport through a randomly oriented multilayered network of two-dimensional (2D) Ti3C2Tx (where Tx is the surface termination and corresponds to O, OH and F) was studied using time-of-flight photoconductivity (TOFP) method, which is highly sensitive to the distribution of charge carrier velocities. We prepared samples comprising Ti3C2Tx with thickness of 12 nm or 6-monolayers. MXene flakes of size up to 16 μm were randomly deposited on the surface by spin-coating from water solution. Using TOFP, we have measured electron mobility that reached values up to 279 cm2/Vs and increase with electric-field in a Poole-Frenkel manner. These values are approximately 50 times higher than previously reported field-effect mobility. Interestingly, our zero-electric-field extrapolate approaches electron mobility measured using terahertz absorption method, which represents intra-flake transport. Our data suggest that macroscopic charge transport is governed by two distinct mechanisms. The high mobility values are characteristic for the intra-flake charge transport via the manifold of delocalized states. On the other hand, the observed Poole-Frenkel dependence of charge carrier mobility on the electric field is typical for the disordered materials and suggest the existence of an important contribution of inter-flake hopping to the overall charge transport.
Keywords: charge transport, multilayered network, flakes, time-of-flight photoconductivity, MXene exfoliation, high-mobility solution-cast thin-film, semiconducting MXene
Published in RUNG: 31.03.2023; Views: 2126; Downloads: 9
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8. Hidroelektrarna Sava KranjDrago Papler, 2020, professional article Keywords: električna energija, proizvodnja, hidroelektrarne, avtomatizacija, inovacije, čistilni stroji, obnova, transport, jez, hidromehanska oprema, agregati, turbine, generatorji, transformatorji, upravljalni sistemi, center vodenja
Published in RUNG: 29.03.2023; Views: 1800; Downloads: 0
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10. Van der Waals heterostructuresVadym Tkachuk, doctoral dissertation Keywords: Graphene, hexagonal boron nitride, PDI8-CN2, organic semiconductor, heterostructure, charge transport, electronic properties, 2D crystal, 2D crystal transfer, tunneling.
Published in RUNG: 24.10.2022; Views: 2440; Downloads: 91
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