Energy Estimation of Cosmic Rays with the Engineering Radio Array of the Pierre Auger Observatory

The Auger Engineering Radio Array (AERA) is part of the Pierre Auger Observatory and is used to detect the radio emission of cosmic-ray air showers. These observations are compared to the data of the surface detector stations of the Observatory, which provide well-calibrated information on the cosmic-ray energies and arrival directions. The response of the radio stations in the 30 to 80 MHz regime has been thoroughly calibrated to enable the reconstruction of the incoming electric field. For the latter, the energy deposit per area is determined from the radio pulses at each observer position and is interpolated using a two-dimensional function that takes into account signal asymmetries due to interference between the geomagnetic and charge-excess emission components. The spatial integral over the signal distribution gives a direct measurement of the energy transferred from the primary cosmic ray into radio emission in the AERA frequency range. We measure 15.8 MeV of radiation energy for a 1 EeV air shower arriving perpendicularly to the geomagnetic field. This radiation energy -- corrected for geometrical effects -- is used as a cosmic-ray energy estimator. Performing an absolute energy calibration against the surface-detector information, we observe that this radio-energy estimator scales quadratically with the cosmic-ray energy as expected for coherent emission. We find an energy resolution of the radio reconstruction of 22% for the data set and 17% for a high-quality subset containing only events with at least five radio stations with signal.Comment: Replaced with published version. Added journal reference and DO

Measurement of the Radiation Energy in the Radio Signal of Extensive Air Showers as a Universal Estimator of Cosmic-Ray Energy

We measure the energy emitted by extensive air showers in the form of radio emission in the frequency range from 30 to 80 MHz. Exploiting the accurate energy scale of the Pierre Auger Observatory, we obtain a radiation energy of 15.8 \pm 0.7 (stat) \pm 6.7 (sys) MeV for cosmic rays with an energy of 1 EeV arriving perpendicularly to a geomagnetic field of 0.24 G, scaling quadratically with the cosmic-ray energy. A comparison with predictions from state-of-the-art first-principle calculations shows agreement with our measurement. The radiation energy provides direct access to the calorimetric energy in the electromagnetic cascade of extensive air showers. Comparison with our result thus allows the direct calibration of any cosmic-ray radio detector against the well-established energy scale of the Pierre Auger Observatory.Comment: Replaced with published version. Added journal reference and DOI. Supplemental material in the ancillary file

Measurement of the cosmic ray spectrum above 4×10184{\times}10^{18} eV using inclined events detected with the Pierre Auger Observatory

A measurement of the cosmic-ray spectrum for energies exceeding $4{\times}10^{18}$ eV is presented, which is based on the analysis of showers with zenith angles greater than $60^{\circ}$ detected with the Pierre Auger Observatory between 1 January 2004 and 31 December 2013. The measured spectrum confirms a flux suppression at the highest energies. Above $5.3{\times}10^{18}$ eV, the "ankle", the flux can be described by a power law $E^{-\gamma}$ with index $\gamma=2.70 \pm 0.02 \,\text{(stat)} \pm 0.1\,\text{(sys)}$ followed by a smooth suppression region. For the energy ($E_\text{s}$) at which the spectral flux has fallen to one-half of its extrapolated value in the absence of suppression, we find $E_\text{s}=(5.12\pm0.25\,\text{(stat)}^{+1.0}_{-1.2}\,\text{(sys)}){\times}10^{19}$ eV.Comment: Replaced with published version. Added journal reference and DO

Multiple Scenario Generation of Subsurface Models:Consistent Integration of Information from Geophysical and Geological Data throuh Combination of Probabilistic Inverse Problem Theory and Geostatistics

Neutrinos with energies above 1017 eV are detectable with the Surface Detector Array of the Pierre Auger Observatory. The identification is efficiently performed for neutrinos of all flavors interacting in the atmosphere at large zenith angles, as well as for Earth-skimming \u3c4 neutrinos with nearly tangential trajectories relative to the Earth. No neutrino candidates were found in 3c 14.7 years of data taken up to 31 August 2018. This leads to restrictive upper bounds on their flux. The 90% C.L. single-flavor limit to the diffuse flux of ultra-high-energy neutrinos with an E\u3bd-2 spectrum in the energy range 1.0 7 1017 eV -2.5 7 1019 eV is E2 dN\u3bd/dE\u3bd < 4.4 7 10-9 GeV cm-2 s-1 sr-1, placing strong constraints on several models of neutrino production at EeV energies and on the properties of the sources of ultra-high-energy cosmic rays

Biphasic short time heat degradation of the blue microalgae protein phycocyanin from Arthrospira platensis

Stability of colorants is concerning for food coloring matrices, particularly for the only natural blue food coloring, phycocyanin. The Spirulina-based microalgal extract is mainly comprised of heat sensitive protein-chromophore complexes, C-phycocyanin and allophycocyanin. Although frequently encountered in food processing, the impact of short time heat treatments has not been studied systematically. Here, phosphate buffered phycocyanin solution was heated in batch and emerging continuous processing systems, both characterized with high surface-to-volume ratios allowing isothermal conditions with residence times down to 5 s. Absorption scans revealed biphasic degradation of phycocyanin color activity to about 30% within 30 s at T ≥ 70 °C. Kinetic modelling of the color decay via an nth order approach contradicts previously assumed linear first order kinetics with a best fitting empirical reaction order of n = 6. It shows that decay in phycocyanin color activity is not a single process but encompasses C-phycocyanin and allophycocyanin aggregate disintegration and denaturation. Industrial relevance Central to this study is the color stability of phycocyanin, which is a high value component, derived from the emerging food source microalgae. It is also the only naturally obtained blue food coloring available to the food industry. Insights could be gained on the color degradation kinetics by treating an industry relevant formulation in batch and emerging scalable continuous systems via micro process engineering. This data will directly support food research and development activities to optimize and minimize blue color losses within multiple product categories.ISSN:1466-856

Effects of dopamine D2/3 and opioid receptor antagonism on the trade-off between model-based and model-free behaviour in healthy volunteers

Human behaviour requires flexible arbitration between actions we do out of habit and actions that are directed towards a specific goal. Drugs that target opioid and dopamine receptors are notorious for inducing maladaptive habitual drug consumption; yet, how the opioidergic and dopaminergic neurotransmitter systems contribute to the arbitration between habitual and goal-directed behaviour is poorly understood. By combining pharmacological challenges with a well-established decision-making task and a novel computational model, we show that the administration of the dopamine D2/3 receptor antagonist amisulpride led to an increase in goal-directed or 'model-based' relative to habitual or 'model-free' behaviour, whereas the non-selective opioid receptor antagonist naltrexone had no appreciable effect. The effect of amisulpride on model-based/model-free behaviour did not scale with drug serum levels in the blood. Furthermore, participants with higher amisulpride serum levels showed higher explorative behaviour. These findings highlight the distinct functional contributions of dopamine and opioid receptors to goal-directed and habitual behaviour and support the notion that even small doses of amisulpride promote flexible application of cognitive control.ISSN:2050-084

Recent ground thermo-hydrological changes in a Tibetan endorheic catchment and implications for lake level changes

International audienceAbstract. Climate change modifies the water and energy fluxes between the atmosphere and the surface in mountainous regions. This is particularly true over the Qinghai-Tibet Plateau (QTP), a major headwater region of the world, which has shown substantial hydrological changes over the last decades. Among them, the rapid lake level variations observed throughout the plateau remain puzzling and much is still to be understood regarding the spatial distribution of lake level trends (increase/decrease) and paces. The ground across the QTP hosts either permafrost or seasonally frozen ground and both are affected by climate change. In this environment, the ground thermal regime influences liquid water availability, evaporation and runoff. Therefore, climate-driven modifications of the ground thermal regime may contribute to lake level variations. For now, this hypothesis has been overlooked by modelers because of the scarcity of field data and the difficulty to account for the spatial variability of the climate and its influence on the ground thermo-hydrological regime in a numerical framework. This study focuses on the cryo-hydrology of the catchment of Lake Paiku (Southern Tibet) for the 1980–2019 period. We use TopoSCALE and TopoSUB to downscale ERA5 data and capture the spatial variability of the climate in our forcing data. We use a distributed setup of the CryoGrid community model (version 1.0) to quantify thermo-hydrological changes in the ground during the period. Forcing data and simulation outputs are validated with weather station data, surface temperature logger data and the lake level variations. We show that both seasonal frozen ground and permafrost have warmed (1.7 °C per century 2 m deep), increasing the availability of liquid water in the ground and the duration of seasonal thaw. Both phenomena promote evaporation and runoff but ground warming drives a strong increase in subsurface runoff, so that the runoff/(evaporation + runoff) ratio increases over time. Summer evaporation is an important energy sink and we find active layer deepening only where evaporation is limited. The presence of permafrost is found to promote evaporation at the expense of runoff, consistent with recent studies. Yet, this relationship seems to be climate dependent and we show that a colder and wetter climate produces the opposite effect. This ambivalent influence of permafrost may help to understand the contrasting lake level variations observed between the south and north of the QTP, opening new perspectives for future investigations