171. Limits to gauge coupling in the dark sector set by the nonobservation of instanton-induced decay of super-heavy dark matter in the Pierre Auger Observatory dataP. Abreu, Andrej Filipčič, Jon Paul Lundquist, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2023, original scientific article Keywords: ultra-high energy cosmic rays, UHE photon flux upper limits, super-heavy dark matter models, instantons, Pierre Auger Observatory
Published in RUNG: 09.02.2023; Views: 1017; Downloads: 0
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172. Cosmological implications of photon-flux upper limits at ultrahigh energies in scenarios of Planckian-interacting massive particles for dark matterP. Abreu, Andrej Filipčič, Jon Paul Lundquist, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2023, original scientific article Keywords: ultra-high energy, cosmic rays, Pierre Auger Observatory, UHE photon flux upper limits, super-heavy dark matter models
Published in RUNG: 09.02.2023; Views: 1105; Downloads: 0
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173. A catalog of the highest-energy cosmic rays recorded during Phase I of operation of the Pierre Auger ObservatoryA. Abdul Halim, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, original scientific article Abstract: A catalog containing details of the highest-energy cosmic rays recorded through the detection of extensive air
showers at the Pierre Auger Observatory is presented with the aim of opening the data to detailed examination.
Descriptions of the 100 showers created by the highest-energy particles recorded between 2004 January 1 and 2020
December 31 are given for cosmic rays that have energies in the range 78–166 EeV. Details are also given on a
further nine very energetic events that have been used in the calibration procedure adopted to determine the energy
of each primary. A sky plot of the arrival directions of the most energetic particles is shown. No interpretations of
the data are offered.
Keywords: ultra-high-energy cosmic rays, cosmic ray air showers, experimental data, catalogs, Pierre Auger Observatory
Published in RUNG: 09.02.2023; Views: 1138; Downloads: 16
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174. Iron phosphides as efficient electrocatalyst for hydrogen evolution and energy conversion : abstractSaim Emin, Takwa Chouki, 2021, published scientific conference contribution abstract Abstract: Transition metal phosphides have been demonstrated as outstanding multifunctional catalysts in a broad range of energy conversion technologies. We developed a solvothermal synthesis approach for iron phosphide electrocatalystsusing a low-cost phosphorus precursor.The synthetic protocol allows for the preparation of a Fe2P phase at 300°C and FeP phase at 350°C. The obtained compounds were coated on conductive substrates to prepare catalysts thin films. Here, we exploited different phases of iron phosphide as counter electrodes (CEs) in dye-sensitized solar cells (DSSCs) with an I−/I3− based electrolyte [2]. The solar-to-current conversion efficiency of the solar cells assembled with the Fe2P material reached 3.96±0.06%,which is comparable to the device assembled with a platinum (Pt) CE. In addition to DSSC
applications, the iron phosphides were used as electrocatalyst for H2 evolution (Fig. 1). To enhance the catalytic activities of obtained iron phosphide particles, heat-treatments were carried out at elevated temperatures.Annealing at 500°C induced structural changes in the samples: (i) Fe2P provided a pure Fe3P phase (Fe3P−500°C) and (ii) FeP transformed into a mixture of iron phosphide phases (Fe2P/FeP−500°C). The electrocatalytic activities for H2 evolution of heat-treated catalysts were studied in 0.5 M sulfuric acid (H2SO4). The HER activities of the iron phosphide catalyst were found to be phase dependent. The lowest recorded overpotential of 110 mV at 10 mA cm−2 vs. a reversible hydrogen electrode was achieved with Fe2P/FeP−500°C catalyst. The developed procedure is an elegant approach to tune the composition of iron phosphide catalyst and control the morphology of particles.
Keywords: Iron phosphides
electrocatalyst
hydrogen evolution
energy conversion
Published in RUNG: 06.02.2023; Views: 988; Downloads: 0
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175. Searches for Ultra-High-Energy Photons at the Pierre Auger ObservatoryP. Abreu, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2022, review article Abstract: The Pierre Auger Observatory, being the largest air-shower experiment in the world, offers an unprecedented exposure to neutral particles at the highest energies. Since the start of data taking more than 18 years ago, various searches for ultra-high-energy (UHE, E > 10[sup]17 eV) photons have been performed: either for a diffuse flux of UHE photons, for point sources of UHE photons or for UHE photons associated with
transient events like gravitational wave events. In the present paper, we summarize these searches and review
the current results obtained using the wealth of data collected by the Pierre Auger Observatory.
Keywords: photons, ultra-high energies, air showers, Pierre Auger Observatory, upper limits, transients
Published in RUNG: 03.01.2023; Views: 1245; Downloads: 0
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176. Recent results from the Pierre Auger ObservatorySerguei Vorobiov, 2022, published scientific conference contribution abstract (invited lecture) Abstract: Ultra-high-energy cosmic rays (UHECRs) are mostly protons and heavier nuclei arriving on Earth from space and producing particle cascades in the atmosphere, ”extensive air showers”. As of today, the most precise and high-statistics data set of the rare (≤ 1 particle per sq.km per year above 10[sup]19 eV) UHECR events is obtained by the Pierre Auger Observatory, a large area (~3000 sq.km) hybrid detector in Argentina. The Auger Observatory determines the arrival directions and energies of the primary UHECR particles and provides constraints for their masses.
In this talk, I will present and discuss the recent results, including the detailed measurements of the cosmic-ray energy spectrum features, the study of the anisotropies in the UHECR arrival directions at large and intermediate angular scales, the multi-messenger searches, and the inferred cosmic-ray mass composition. Finally, the progress of the current upgrade of the Observatory, "AugerPrime" which is aimed at improving the sensitivity to the mass composition of ultra-high-energy cosmic rays, will be presented.
Keywords: ultra-high-energy cosmic rays, Pierre Auger Observatory, UHECR mass composition, energy spectrum, anisotropies, AugerPrime upgrade
Published in RUNG: 23.12.2022; Views: 1331; Downloads: 7
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177. Metal hydroxides for energy conversion and energy storageAndraž Mavrič, invited lecture at foreign university Abstract: Electrocatalysts, electrochromic devices, and pseudo-capacitors based on transition metal (oxy)hydroxides depend on the reversibility of the reduction-oxidation process of metal cations. Rapid switching between different redox states is often involved, particularly in electrocatalysis where redox metal sites act as active centers for electron transfer to the reactant. To ensure long-term durability, the reversibility of the redox metal sites should be robust. Nickel hydroxide is a model catalyst for the oxygen evolution reaction (OER) and the basic representative of the layered double hydroxides. It is frequently combined with other transition metals (e.g. Fe, Co, Mn), forming some of the most active OER electrocatalysts in alkaline media. [1] I will present the use of in-situ spectroscopy to track the reversibility of redox states of the Ni(OH)2 during its lifetime. During the operation at 200 mA cm-2 in 1 M KOH electrolyte, the catalytic activity of Ni(OH)2 gradually degrades until lastly, the catalyst breaks down. During the catalyst lifetime, the reduction-oxidation reversibility of the Ni2+/3+ redox couple is lost and the catalyst converts into an inactive phase. The reversibility of the redox couple is monitored by the in-situ UV/Vis spectroscopy. During the catalyst lifetime, the reversibility of the redox peak is lost. The activity collapse is attributed to the structural amorphization/disordering of the layered Ni(OH)2 catalyst, as confirmed by TEM investigations and in-situ Raman spectroscopy. [2]
Similarly, the redox reversibility of metal sites is also important for long cycle life in supercapacitors, based on the pseudo-capacitance mechanism. Contrary to catalysts, for supercapacitors, the water oxidation needs to be suppressed to increase the working voltage range. I will discuss the mechanisms for the deactivation of transition metal hydroxides to serve as capacitors and approaches to increase power density.
Finally, I will discuss the use of mixed metal hydroxides to serve as precursors for a copper oxide-based catalytic system for CO2 hydrogenation to methanol. Thermal decomposition of hydrotalcite-based hydroxide precursor is followed by in-situ x-ray diffraction. The conditions to prepare disordered oxide in contact with catalytical active Cu metal are identified and the catalytic performance of catalysts with crystalline and disordered oxide phases are compared.
[1] A. Mavrič, C. Cui, (2021), Advances and Challenges in Industrial-Scale Water Oxidation on Layered Double Hydroxides, ACS Appl. Energy Mater., 4, 12032-12055.
[2] A. Mavrič, M. Fanetti, Y. Lin, M. Valant, C. Cui, (2020), Spectroelectrochemical Tracking of Nickel Hydroxide Reveals Its Irreversible Redox States upon Operation at High Current Density, ACS Catal., 10, 9451-9457.
Keywords: electrochemistry, energy storage, CO2 hydrogenation, methnaol
Published in RUNG: 13.10.2022; Views: 1156; Downloads: 0
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178. Correlation between FeCl2 electrolyte conductivity and electrolysis efficiencyUroš Luin, Matjaž Valant, Iztok Arčon, 2022, published scientific conference contribution abstract Abstract: The electrolysis efficiency is an important aspect of the Power-to-Solid energy storage technology (EST) based
on the iron chloride electrochemical cycle [1]. This cycle employs an aqueous FeCl2 catholyte solution for the
electro-reduction of iron. The metal iron deposits on the cathode. The energy is stored as a difference in the
redox potential of iron species. Hydrogen, as an energy carrier, is released on demand over a fully controlled
hydrogen evolution reaction between metallic Fe0 and HCl (aq) [1]. Due to these characteristics, the cycle is
suitable for long-term high-capacity and high-power energy storage. In a previous work [2] we revealed that
the electrolyte conductivity linearly increases with temperature. Contrary, the correlation between the
electrolyte concentration and efficiency is not so straightforward. Unexpectedly small efficiency variations were
found between 1 and 2.5 mol dm-3 FeCl2 (aq) followed by an abrupt efficiency drop at higher concentrations.
To explain the behavior of the observed trends and elucidate the role of FeCl2 (aq) complex ionic species we
performed in situ X-ray absorption studies. We made a dedicated experimental setup, consisting of a tubular
oven and PMMA liquid absorption cell, and performed the measurements at the DESY synchrotron P65
beamline. The XAS investigation covered XANES and EXAFS analyses of FeCl2 (aq) at different
concentrations (1 - 4 molL-1) and temperatures (25 - 80 °C). We found that at low temperature and low FeCl2
concentration the octahedral first coordination sphere around Fe is occupied by one Cl ion at a distance of 2.33
(±0.02) Å and five water molecules at a distance of 2.095 (±0.005) Å [3]. The structure of the ionic complex
gradually changes with an increase in temperature and/or concentration. The apical water molecule is
substituted by a chlorine ion to yield a neutral Fe[Cl2(H2O)4]0. The transition from the single charged
Fe[Cl(H2O)5]+ to the neutral Fe[Cl2(H2O)4]0 causes a significant drop in the solution conductivity, which well
correlates with the existing conductivity models [3].
[1] M. Valant, “Procedure for electric energy storage in solid matter. United States Patent and
Trademark Office. Patent No. US20200308715,” Patent No. US20200308715, 2021.
[2] U. Luin and M. Valant, “Electrolysis energy efficiency of highly concentrated FeCl2 solutions
for power-to-solid energy storage technology,” J. Solid State Electrochem., vol. 26, no. 4, pp.
929–938, Apr. 2022, doi: 10.1007/S10008-022-05132-Y.
[3] U. Luin, I. Arčon, and M. Valant, “Structure and Population of Complex Ionic Species in
FeCl2 Aqueous Solution by X-ray Absorption Spectroscopy,” Molecules, vol. 27, no. 3, 2022,
doi: 10.3390/molecules27030642.
Keywords: Iron chloride electrochemical cycle, Power-to-Solid energy storage, XANES, EXAFS, electrical
conductivity, electrolyte complex ionic species structure and population
Published in RUNG: 26.09.2022; Views: 1488; Downloads: 0 (1 vote)
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179. Investigation of the effective transmittance of Mach-Zehnder interferometer in the multi-longitudinal-mode high-spectral-resolution lidarFei Gao, Fengjia Gao, Xiao Yang, Gaipan Li, Li Wang, Meng Wang, Dengxin Hua, Griša Močnik, Samo Stanič, 2022, original scientific article Abstract: Effective transmittance is an important parameter of Mach-Zehnder interferometer in the retrieval of aerosol optical properties using the multi-longitudinal-mode high-spectral-resolution lidar, which is a function of the complex degree of coherence. In this paper, we retrieve the parameter of the complex degree of coherence for the multi-longitudinal-mode laser from the theoretical analysis, optical simulation and experimental measurements, which are 0.726, 0.678 and 0.453 using the Mach-Zehnder interferometer with the optimal optical path difference of two times of laser optical cavity length (∼1000 mm) and under the light illumination of the high power Nd:YAG laser with the mode number of 101 and mode interval of 300 MHz under the condition of laser linewidth of 1 cm−1 (30 GHz). The preliminary measurement results of aerosol optical properties using the constructing multi-longitudinal-mode high-spectral-resolution lidar show that the difference of the complex degree of coherence retrieved from the presented methods results in the relative error of 40% in the aerosol backscattering coefficient with thin cloud layer and 90% with the presence of dense aerosol layer.
Keywords: effective transmittance, Mach-Zehnder interferometer, Multi-logitudinal-mode laser, High-spectral-resolution lidar
Published in RUNG: 20.09.2022; Views: 1408; Downloads: 0
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180. The conformational plasticity of the selectivity filter methionines controls the in-cell Cu(I) uptake through the CTR1 transporterPavel Janoš, Jana Aupič, Sharon Ruthstein , Alessandra Magistrato, 2022, original scientific article Abstract: Copper is a trace element vital to many cellular functions. Yet its abnormal levels are toxic to cells, provoking a variety of severe diseases. The high affinity copper transporter 1 (CTR1), being the main in-cell copper [Cu(I)] entry route, tightly regulates its cellular uptake via a still elusive mechanism. Here, all-atoms simulations unlock the molecular terms of Cu(I) transport in eukaryotes disclosing that the two methionine (Met) triads, forming the selectivity filter, play an unprecedented dual role both enabling selective Cu(I) transport and regulating its uptake rate thanks to an intimate coupling between the conformational plasticity of their bulky side chains and the number of bound Cu(I) ions. Namely, the Met residues act as a gate reducing the Cu(I) import rate when two ions simultaneously bind to CTR1. This may represent an elegant autoregulatory mechanism through which CTR1 protects the cells from excessively high, and hence toxic, in-cell Cu(I) levels. Overall, our outcomes resolve fundamental questions in CTR1 biology and open new windows of opportunity to tackle diseases associated with an imbalanced copper uptake.
Keywords: copper, membrane transporter, molecular dynamics, QM/MM, free energy
Published in RUNG: 15.09.2022; Views: 1350; Downloads: 0
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