High-energy Events Research Articles

Sources of Low-Energy Events in Low-Threshold Dark-Matter and Neutrino Detectors

We discuss several low-energy backgrounds to sub-GeV dark matter searches, which arise from high-energy particles of cosmic or radioactive origin that interact with detector materials. We focus in particular on Cherenkov radiation, transition radiation, and luminescence or phonons from electron-hole pair recombination, and show that these processes are an important source of backgrounds at both current and planned detectors. We perform detailed analyses of these backgrounds at several existing and proposed experiments based on a wide variety of detection strategies and levels of shielding. We find that a large fraction of the observed single-electron events in the SENSEI 2020 run originate from Cherenkov photons generated by high-energy events in the Skipper Charge Coupled Device, and from recombination photons generated in a phosphorus-doped layer of the same instrument. In a SuperCDMS HVeV 2020 run, Cherenkov photons produced in printed-circuit-boards located near the sensor likely explain the origin of most of the events containing 2 to 6 electrons. At SuperCDMS SNOLAB, radioactive contaminants inside the Cirlex located inside or on the copper side walls of their detectors will produce many Cherenkov photons, which could dominate the low-energy backgrounds. For the EDELWEISS experiment, Cherenkov or luminescence backgrounds are subdominant to their observed event rate, but could still limit the sensitivity of their future searches. We also point out that Cherenkov radiation, transition radiation, and recombination could be a significant source of backgrounds at future experiments aiming to detect dark-matter via scintillation or phonon signals. We also discuss the implications of our results for the development of superconducting qubits and low-threshold searches for coherent neutrino scattering, and comment on design strategies that can be implemented to mitigate these backgrounds.

Short-term effects of hurricane events on the bioindicator species Ocypode quadrata inhabiting an island in essence free of anthropogenic disturbances

The effects of high-energy weather events may be most dramatic on coast dominated by sandy beaches, characteristic habitat of the Atlantic ghost crab. This study evaluates the impact of two hurricanes over Ocypode quadrata populations based on the hypothesis that natural disturbances may bring on a decrease in crab burrow size (population structure) and/or a significant decline in the burrow density (relative abundance). Densities of crabs, estimated via burrow counts and their size, evaluated according to burrow opening diameter, were quantified at six sites around Isla de Aves, before (July) and after (November) two major hurricanes (Irma and Maria) that hit the coastal areas on islands of the Caribbean Sea in 2017. Six 2 × 2 m areas were sampled at each site. The results reveal an effect on the size structure, while the population density did not present any evident change between the pre and post-hurricane moments. The decrease in the diameter of the burrows after the passage of the hurricanes, suggests that the larger crabs could have been removed during this event followed by an arrival of new recruits into the ghost crab population. The results suggest a short-term resilience to the impact of extreme climatic events in terms of population density, a scenario that could had been favored by several conditions. Isla de Aves has sandy beaches exposed to ocean currents, which favor the transport of larvae and the recruitment of juveniles. The availability and quality of food, due to its characteristics of being a main nesting site for sea turtles (mainly green turtle); therefore, it offers various resources in abundance (e.g., turtle eggs). As well as the characteristic of being an island practically free of anthropogenic disturbances.

Stratigraphic architecture of a mixed clastic-carbonate succession and 87Sr/86Sr-based chronostratigraphy along the margin of a synorogenic extensional basin (Hochmoos Formation, upper Santonian, Northern Calcareous Alps)

Abstract The Gosau Group (Turonian to Ypresian) of the Eastern Alps is a synorogenic wedge-top succession that accumulated in active depocenters in an oblique-convergent plate tectonic setting. Due to high morphological differentiation of depocenters by tectonism, the Gosau Group displays a wide range of facies as well as marked facies heteropy and thickness variations over short lateral distances. In the area of the locations Gosau and Russbach, the Hochmoos Formation along the SE basin margin near Gosauschmied comprises coastal to shallow-marine deposits and small rudist bioconstructions and was investigated by way of field mapping, profile descriptions, microfacies analysis, isotope measurements and assessment of fossil content. Strontium isotope ratios (87Sr/86Sr) from 0.707485 (oldest) to 0.707549 (youngest) indicate a latest Santonian age, with the youngest parts of the Hochmoos Formation possibly extending into the Campanian. On the west side of the study area, the succession of lithologies and fossil content record transgression of a fan-delta to marginal-marine environment (lowstand to transgressive systems tract), followed by shallow neritic deposition (part of the transgressive systems tract) and, finally, by progradational stacking of limestone beds in the highstand systems tract, culminating in growth of rudist thickets in an inner shelf and partially protected ‘lagoonal’ milieu. Eventually, at the inception of the following falling stage systems tract, input of large clasts of Dachstein Limestone, quartz and chert record a recurrence of the subaqueous part of a fan-delta. On the east side of the study area, a preponderance of rudist-clastic limestones over a few rudist biostromes preserved in situ indicate a normal-marine environment punctuated by high-energy events, such as storms or tsunami. The scarcity of benthic foraminifera and the presence of only isolated specimens of colonial corals underscore a habitat with a calcarenitic substrate frequently shifted by currents. Several lines of evidence indicate that the western part of the study area was more proximal relative to the eastern one. With a maximum thickness of 68 m, the Hochmoos Formation at Gosauschmied is slightly thicker and more distal than outcrops located nearer to the basin margin and farther towards the SE (Schmiedsippl, Katzhofgraben), but significantly thinner than the nearly 300 m at Gosau Pass-Gschütt, or the thickness of 170 m observed in the area of Rigaus-Abtenau farther in the West. These thickness variations are interpreted as a result of extensional syndepositional tectonism. At Gosauschmied, the vertical arrangement of facies records a cycle of relative sea-level change that may have been tectonically enhanced.

Habitats in the Pre-Taghanic (Givetian, Middle Devonian) muddy carbonate ramp at Miłoszów (Holy Cross Mountains, Poland): geochemical and microfacies evidence

The well-known fossiliferous and lithologically variable Middle Devonian Shaly-Calcareous Skały Formation in the Łysogóry Region (northern part of the Holy Cross Mountains, central Poland) was studied for the first time in terms of elemental geochemistry, carbon isotope stratigraphy and limestone microfacies. Three Lower to Middle Givetian marly-limestone successions, exposed at Miłoszów, represent middle to outer facies belts of the vast carbonate ramp, characterized by very rich epifaunal and infaunal benthic life in muddy, oxic, eutrophic, and photic zone habitats. Brachiopods and occasionally corals (in mesophotic association), erect branching bryozoans, and tiny crinoids played a leading role among flourishing sessile suspension-feeders. High-energy storm events, possibly even a tsunami, during the brief Early Givetian time strengthened a prolific carbonate ooze delivery system from shallow ramp areas, including restricted back-ramp lagoons and a variety of organic buildups, populated by corals and stromatoporoids. The ecologically mixed skeletal grain association is characterized by the rich occurrence of a typical lagoonal biota, calcispheres and amphiporoids. The effective carbonate factory declined stepwise regionally during the Middle Givetian because of an intermittent progradation of the deltaic system of the Świętomarz Beds, linked with climate cooling and the activation of block movements. The regional carbonate crisis resulted in the demise of diverse benthic life, including the prolific calcified microbiota. The higher Skały Formation succession, deposited between the important Kačák and Taghanic bioevents, is noticeable for a background carbon-isotope pattern in carbonate and organic matter signatures, with the baseline δ 13 C carb values between 1‰ and 2‰. The microfacies and chemostratigraphic data confirm that at least the lower pumilio bioevent was not recorded in the Łysogóry Region.

Human (boot) tracks preserved in volcanic deposits of Surtsey Island, Iceland

Several human boot tracks and trackways are preserved in palagonitized tuff in Surtsey Island, south Iceland. The underlying palagonitized substrate is made of reworked tephra debris talus and slump material that lies partly on top of lava flows erupted in 1964–1965 in Surtungur tuff crater and 1966–1967 in Surtur tuff crater. This stratigraphic information along with other evidence from the nature of the sediments, alteration history of the deposits and the record of human presence on the island indicate the tracks were formed in the years between 1967 and 1970. The exquisite preservation and consolidation of the tracks coincide with a period of rapid geomorphic changes in the early stages of development of the island, when the newly formed tephra was still unconsolidated and easily mobilized by mass movements, wind and runoff. Furthermore, cooling magmatic intrusions generated hydrothermal activity on the island speeding up diagenesis of the tephra and the cementation of the boot tracks in the substrate. Expulsion rims preserved in some of the boot tracks suggests the tracks were formed in moderately cohesive substrate, followed by rapid burial of the prints in heavy wind and/or storm. Three boot sizes were identified suggesting the tracks were made by at least three persons, and documentation of the boot anatomy, measurements on angle of gait, stride and pace reveal the direction of movement for each trackway. Intense erosion of the tuff cones has exhumed the tracks to the surface that stand today as a testimony to impressively rapid geological cycles for preservation and exhumation and the role of unstable and rapidly changing environments, the aftermath of high-energy events, in capturing and preserving ichnites. These boot tracks are the first fossil tracks described for Iceland and the first record in the world of boot tracks preserved in sedimentary rocks.

Human (boot) tracks preserved in volcanic deposits of Surtsey Island, Iceland

Several human boot tracks and trackways are preserved in palagonitized tuff in Surtsey Island, south Iceland. The underlying palagonitized substrate is made of reworked tephra debris talus and slump material that lies partly on top of lava flows erupted in 1964–1965 in Surtungur tuff crater and 1966–1967 in Surtur tuff crater. This stratigraphic information along with other evidence from the nature of the sediments, alteration history of the deposits and the record of human presence on the island indicate the tracks were formed in the years between 1967 and 1970. The exquisite preservation and consolidation of the tracks coincide with a period of rapid geomorphic changes in the early stages of development of the island, when the newly formed tephra was still unconsolidated and easily mobilized by mass movements, wind and runoff. Furthermore, cooling magmatic intrusions generated hydrothermal activity on the island speeding up diagenesis of the tephra and the cementation of the boot tracks in the substrate. Expulsion rims preserved in some of the boot tracks suggests the tracks were formed in moderately cohesive substrate, followed by rapid burial of the prints in heavy wind and/or storm. Three boot sizes were identified suggesting the tracks were made by at least three persons, and documentation of the boot anatomy, measurements on angle of gait, stride and pace reveal the direction of movement for each trackway. Intense erosion of the tuff cones has exhumed the tracks to the surface that stand today as a testimony to impressively rapid geological cycles for preservation and exhumation and the role of unstable and rapidly changing environments, the aftermath of high-energy events, in capturing and preserving ichnites. These boot tracks are the first fossil tracks described for Iceland and the first record in the world of boot tracks preserved in sedimentary rocks.

Linking oceanographic processes to contourite features: Numerical modelling of currents influencing a contourite depositional system on the northern South China Sea margin

Combining high-resolution bathymetry and 2-D seismic data with 3-D hydrodynamic numerical simulation results to identify Quaternary plastered contourite drifts in the South China Sea northern margin (i.e., the Jianfeng and Yitong slopes), this study aims to disentangle the impacts of bottom currents associated with the intermediate and deep water masses.Upslope parts of plastered drifts (~1000–1200 mwd) are smooth and gentle (up to 1°) surfaces, which can also be classified as contourite terraces. They are characterised by non-deposition and sheeted deposition that indicate dominant flow conditions capable of transporting sediments. The responsible hydrodynamic forcing here is the anticyclonic South China Sea Intermediate Water currents, which flow eastward with a mean velocity of 2–3 cm/s. These are sporadically enhanced and can exceed 6 cm/s during high-energy intermittent events such as deep-reaching eddies.The central parts of the plastered drifts, located seaward of the terraces, present a subtle mounded morphology (1°–2°, ~1200–1500 mwd) partly perturbated by wavy bedforms. The downslope parts of the plastered drifts feature step-forming slides/slumps with steep slope gradients (1°–5°, ~1500–2000 mwd). According to our simulation results, the depth range of the plastered drifts overlaps the transition zone between the intermediate and deep water masses, wherein the simulated mean current velocity is 0–2 cm/s with variable directions, suggesting its deposition-favourable environment.Steep (>2°) slopes beneath the plastered drifts (below ~2000 mwd) present along-slope truncations, including contourite channels and moats that indicate enforced currents capable of erosion. Responsible hydrodynamic forcing is the cyclonic South China Sea Deep Water currents, which flow westward with a mean velocity of 3–5 cm/s and exceed 15 cm/s during high-energy intermittent events.The results of this study show a clear link between bottom currents' behaviours (e.g., mean flow condition and variability) and contouritic depositional patterns, which suggest that continental slopes can be effectively shaped by large-scale ocean circulations through the topography-current interaction. The weakest hydrodynamic condition and highest sediment accumulation rate, occurring in the ~800 m thick transition domain between two water masses in the study area, facilitate the development of plastered drifts at the seaward side of contourite terraces. The outcomes of our study may have broad implications for understanding the relationship between processes and products in continental margins.

Electron–phonon coupling factor and electron heat capacity of 6H-SiC

ABSTRACT For high-energy single ion events, the relationship between electronic energy loss mechanism and atomic processes is generally described by the inelastic thermal spike model. However, the parameters required for the model are not accurately known and are often estimated from a free electron gas model. To ensure this model is more reliable and predictive, a more accurate calculation for the parameters should be taken. In this paper, the temperature dependence of the electronic heat capacity and electron–phonon coupling factor (e-ph) has been calculated, using density functional theory (DFT). The calculation results demonstrate that the effect of electron thermal excitation on the thermodynamic parameters is sensitive to the bandgap, and these parameters vary immensely with the electron temperature. Besides, to verify the accuracy of obtained parameters, both the swift heavy ions (SHI) irradiation in crystalline 6H-SiC and amorphous 6H-SiC are simulated, using the inelastic thermal spike model. And the results are more consistent with the experiment conclusion, for the obtained parameters by DFT. Hence, the calculated temperature-dependent parameters are more suitable for the inelastic thermal spike model.

Mechanism of Rock Bursts Induced by the Synthetic Action of “Roof Bending and Rock Pillar Prying” in Subvertical Extra-Thick Coal Seams

When studying the rock burst mechanism in subvertical extra-thick coal seams in the Wudong coal mine in Xinjiang, China, most studies focus on rock pillars, while the effect of the roof on rock bursts is usually ignored. In this paper, a rock burst mechanism in subvertical extra-thick coal seams under the control of a “roof-rock pillar” is proposed. A theoretical analysis is first performed to explain the effect of roof-rock pillar combinations on rock bursts in coal seams. Numerical modeling and microseismic analysis are implemented to further study the mechanism of rock burst. The main conclusions are as follows: 1) During the mining of the B3+6 coal seam, an obvious microseismic concentration phenomenon is found in both the roof and rock pillar of B3+6. The rock bursts exhibited obvious directionality, and its main failure characteristics are floor heave and sidewall heave, but there will also be some failures such as shoulder socket subsidence in some parts. 2) The stress transfer caused by rock pillar prying is the main reason for the large difference in rock burst occurrence near the vertical and extra thick adjacent coal seams under the same mining depth. 3) Under the same cantilever length, the elastic deformation energy of the roof is much greater than that of the rock pillar, which makes it easier to produce high-energy microseismic events. With an increasing mining depth, the roof will become the dominant factor controlling the occurrence of rock bursts. 4) The high-energy event produced by the rock mass fracture near the coal rock interface easily induces rock bursts, while the high-energy event produced by the fracture at the far end of the rock mass is less likely to induce rock burst. 5) Roof deformation extrusion and rock pillar prying provide high static stress conditions for the occurrence of rock bursts in the B3+6 coal seam. The superposition of the dynamic disturbance caused by roof and rock pillar failure and the high static stress of the coal seam is the main cause of rock burst in the B3+6 coal seam.

Multi-chip front-end electronics LYRA for X and γ Ray detector for HERMES mission

We present the experimental results of the Application Specific Integrated Circuit (ASIC), called LYRA, specifically designed for the High-Energy Rapid Modular Ensemble of Satellites (HERMES) mission concept, a constellation of nano-satellites able to detect and localize high-energy rapid transient events (up to 2.2 MeV) as the Gamma Ray Bursts (GRBs) from the deep space. LYRA has been desied for the detection system composed by a combination of Gadolinium Aluminum Gallium Garnet (GAGG) scintillators for high-energy photons, coupled to a matrix of 120 silicon drift detectors (SDD), used for detecting both scintillation light and low-energy photons. The LYRA ASIC has been conceived with a multi-chip architecture: 120 LYRA Front-End chips (LYRA-FE) are placed in close proximity to the anodes of the SDD matrix for a first processing of the detector signals and trasmit them in current mode to four 32-channel LYRA Back-End chips (LYRA-BE) to complete the elaboration. The requirements that the LYRA ASIC have to fulfill for the HERMES project are challenging: the maximum input energy measured in Silicon must reach 120 keV — corresponding to 2.2 MeV on GAGG — with a linearity error below 1%, the electronic noise must be less then 30 el. r.m.s. and the power consumption less then 1 mW per channel in a system with 120 channels working in parallel. The characterization of LYRA has been carried out on a dedicated test board, coupling one channel of the ASIC with a 25 mm2 SDD. An input full scale range of 5.2 fC and an electronic noise of 22 el. r.m.s. have been measured at -33∘C with a power consumption of 745 µW per channel.

Natural vs. trawling-induced water turbidity and suspended sediment transport variability within the Palamós Canyon (NW Mediterranean)

Increases of water turbidity and suspended sediment transport in submarine canyons have been associated with high-energy events such as storms, river floods and dense shelf water cascading (DSWC), and occasionally with bottom trawling along canyon flanks and rims. To assess the variations on the water column turbidity and sediment transport in the Palamós Canyon linked to both natural and trawling-induced processes, an autonomous hydrographic profiler, as well as a near-bottom current meter and a turbidimeter were deployed in the canyon axis (929 m depth) from February to June 2017, covering a trawling closure (February) and trawling activities (March-June). Periods of enhanced water turbidity during the trawling closure were mostly associated with storms and DSWC events, transporting turbid dense waters into the canyon. In absence of such events, the water column displayed low suspended sediment concentrations (~ 0.3 mg L− 1) until the trawling season began, when particulate matter detachments, ranging between > 1 mg L− 1 and 3.8 mg L− 1, were observed at the water depths where the trawling grounds are found. During the trawling closure, high near-bottom suspended sediment fluxes (35–44 g m− 2 s− 1) were sporadically registered at ~ 920 m depth associated with a major storm and DSWC event. Smaller but more frequent increases of near-bottom suspended sediment fluxes (0.1–1.4 g m− 2 s− 1) were recorded during trawling activities. Despite these smaller trawling-induced suspended sediment fluxes, 30 days of continuous bottom trawling activity transported a total amount of 40 kg m− 2, of similar magnitude to that generated by a major DSWC event (50 kg m− 2). Since bottom trawling in Palamós Canyon is practiced on a daily basis throughout the year, a much larger contribution of anthropogenically derived water turbidity and suspended sediment transport can be expected.

Follow-up of the IceCube alerts with the Baikal-GVD telescope

The high-energy muon neutrino events of the IceCube telescope, that are triggered as neutrino alerts in one of two probability ranks of astrophysical origin, “gold” and “bronze”, have been followed up by the Baikal-GVD in a fast quasi-online mode since September 2020. Search for correlations between alerts and GVD events reconstructed in two modes, muon-track and cascades (electromagnetic or hadronic showers), for the time windows ±1 h and ±12 h does not indicate statistically significant excess of the measured events over the expected number of background events. Upper limits on the neutrino fluence will be presented for each alert.

Energy characteristics of acoustic emission under various modes of uniaxial loading

Acoustic emissions were recorded in the process of uniaxial compression of samples of various geomaterials. The experiments were carried out on a low-noise lever setup with water leakage; the maximum load on the sample did not exceed 250 kN. Some of the samples were tested at a continuously increasing load, the other at its stepwise change. The energy distribution of acoustic emission signals was investigated. The energy characteristic of acoustic emission was the square of the maximum signal amplitude. The flow of AE events is considered from the standpoint of nonequilibrium thermodynamics and Tsallis statistics. A decrease in the steepness of the linear part of the repeatability plots for a particular geomaterial was revealed when changing the loading mode from linear to stepwise, which means an increase in the proportion of higher-energy events with a stepwise change in load.

Evolution of a high latitude high-energy beach system (Maastrichtian–Eocene, Magallanes/Austral Basin, Chilean Patagonia)

Studies on the environmental dynamics of high energy beach systems have to deal with factors as diverse as wave energy, coastal currents and tidal amplitude. Their interaction produces complex and often poorly understood sedimentary architectures. As a rule, the results achieved do not allow us to understand the depositional architectures associated with each of these processes. In this article, we analyze a high-energy beach system describing geometries, textures, paleocurrents, ichnological associations and taphonomic aspects seeking to define the associated environmental parameters. Detailed analyses of sedimentary facies, and analyses of paleocurrents, ichnological and taphonomic associations were performed in a high resolution sequence stratigraphy. The integrated analyses demonstrate the evolution of a high-energy beach system with a general north-south direction in a meso- to macrotidal regime, built by waves from the northwest, generating longshore currents to the south. A subordinate pattern, with waves coming from the southeast, generating longshore currents to the north, was also interpreted. Due to the high wave energy, evidence of tide action is sporadic, but the wide dominance of upper shoreface deposits with low angle dips, indicating an extension in the continent-offshore section, are compatible with a meso- to macrotidal setting. Taphonomic analysis shows that skeletons of marine invertebrates and vertebrates were significantly reworked and redistributed by strong wave action and longshore currents marking high energy events related to scour surfaces. Changes in the pattern of ichnofauna and bioturbation intensity are associated with variations in environmental energy and probably in salinity. The ichnological data helps to indicate progressive environmental stress towards the Cretaceous/Paleogene (K/Pg) boundary. Paleocurrent data, measured in trough cross-bedding of the upper shoreface deposits, suggest a complex atmospheric circulation pattern and water circulation of an inland sea. The resultant climatic pattern is compatible with modern atmospheric circulation at a similar latitude. The excellent exposure and abundant fossil records at K-Pg interval make this region an important source for studies of environmental dynamics and their interaction with biota at middle-high latitudes.

Calibration and Assessment of Bed Evolution Model in an Embayed Beach with Submerged Breakwaters

Cho, M.; Yoon, H.-D.; Do, K., and Kim, I., 2021. Calibration and assessment of bed evolution model in an embayed beach with submerged breakwaters. In: Lee, J.L.; Suh, K.-S.; Lee, B.; Shin, S., and Lee, J. (eds.), Crisis and Integrated Management for Coastal and Marine Safety. Journal of Coastal Research, Special Issue No. 114, pp. 514–518. Coconut Creek (Florida), ISSN 0749-0208. An embayed beach is a common beach around the world and relatively stable over longer timescale except for high-energy wave event. A submerged breakwater is a structure that is effective in reducing coastal erosion by dissipating wave energy. Typhoon Lingling, which occurred in September 2019, affected the shoreline change in Korea. XBeach, process-based model, has been used to simulate nearshore hydrodynamics and morphological response to storm condition. XBeach has a variety of parameters, and provides default settings. However, parameter calibration is a process that must be performed to apply to a specific site. Parameter calibration has been carried out depending on the researchers' experience or through traditional trial-and-error, but more rigorous and systematic methods are required. In this study, parameter calibration in XBeach is performed for an embayed beach with submerged breakwaters under storm conditions. Seven hundred (700) parameter groups were generated using Monte-Carlo sampling and 700 simulations were performed for calibration and assessment using the Root Mean Square Error (RMSE) statistical method. The retreat distance of 20 cross-shore section extracted from the surveyed shoreline, and RMSE was calculated through comparison with the simulation results. As a result, there are difference between the default setting and the optimal setting, and the accuracy in the optimal setting was improved by about 30% compared to the default setting.

Radio Observations of an Ordinary Outflow from the Tidal Disruption Event AT2019dsg

Abstract We present detailed radio observations of the tidal disruption event (TDE) AT2019dsg, obtained with the Karl G. Jansky Very Large Array (VLA) and the Atacama Large Millimeter/submillimeter Array (ALMA), and spanning 55–560 days post disruption. We find that the peak brightness of the radio emission increases until ∼200 days and subsequently begins to decrease steadily. Using a standard equipartition analysis, including the effects of synchrotron cooling as determined by the joint VLA–ALMA spectral energy distributions, we find that the outflow powering the radio emission is in roughly free expansion with a velocity of ≈0.07 c, while its kinetic energy increases by a factor of about 5 from 55 to 200 days and plateaus at ≈4.4 × 1048 erg thereafter. The ambient density traced by the outflow declines as radius ≈R −1.7 on a scale of ≈(1–4) × 1016 cm (≈6300–25,000 R s ), followed by a steeper decline to ≈7 × 1016 cm (≈44,000 R s ). Allowing for a collimated geometry, we find that to reach even mildly relativistic velocities (Γ = 2) the outflow requires an opening angle of θ j ≈ 2°, which is narrow even by the standards of gamma-ray burst jets; a truly relativistic outflow requires an unphysically narrow jet. The outflow velocity and kinetic energy in AT2019dsg are typical of previous non-relativistic TDEs, and comparable to those from type Ib/c supernovae, raising doubts about the claimed association with a high-energy neutrino event.

Search for a diffuse flux of cosmic neutrinos with the ANTARES neutrino telescope

An excess of high-energy events has been found in previous ANTARES searches for a diffuse flux of cosmic neutrinos, consistent in spectral slope and normalisation with the cosmic neutrino signal detected by the IceCube Neutrino Observatory. The analysis of ANTARES data can provide valuable information in the study of this high-energy neutrino signal, especially in the case of soft-spectra solutions. To improve previous ANTARES results, a new event selection has been developed for cascade-like events, relying on a boosted decision tree multivariate-analysis technique. This yields a 5-fold increase in event statistics, while also reducing the surviving foregrounds and the related systematic uncertainties. This contribution will report on the status of the analysis and the prospects emerging from the use of this new event sample in the search for a diffuse flux of cosmic neutrinos.

Marine and marginal marine Ostracoda as proxies in geoarchaeology

Ostracoda, minute aquatic crustaceans with calcitic shells, are highly versatile proxies in geoarchaeological contexts. Their species-specific ecological preferences and ranges allow the reconstruction of palaeoenvironments and anthropogenic impacts in detail. Environmentally driven morphological variability and shell chemistry signatures as stable isotope and trace element values can provide additional palaeoenvironmental information. Ostracods can be used for provenance analyses and stratigraphical investigations as well. Their small size and high abundance in most water bodies makes them ideal for studying sediment cores and smaller samples from trenches or outcrops, especially in coastal areas where they show a high diversity and abundance compared to other groups of meiofauna. In archaeological contexts, fossil ostracods may provide information about climate, sea level and hydrography, high energy events like storms or tsunamis, ocean currents, land use, pollution, water constructions, stratigraphy, trade connections or the origin of sediment material.We give an overview on the state of ostracod-based research in geoarchaeology today and present some European case studies to illustrate concepts and methods of such field of study.

Modification of Coal Samples with Bursting Liability Subjected to Microwave Irradiation

This paper introduces the innovative technique to release the bursting liability of coal seam via microwave irradiation. To verify the feasibility of this environment-friendly technique, a series of laboratory tests incorporating acoustic emission (AE) investigation were carried out. Test results indicated that both the uniaxial compressive strength (UCS) and bursting energy index of raw and water-soaked coal samples were significantly reduced. In particular, the bursting liability was reduced by one level when the values of UCS were compared, the evidence of which is the variation of wave velocities of tested coal samples. It can also be found from the events and hits in the complete stress-strain curve and the cumulative curve of acoustic emission that the elastic modulus of the raw and water-soaked coal samples subjected to microwave irradiation decreased by 58.42% and 29.63%, respectively. This facilitates the entry into the stage of stable crack propagation more quickly, the growth rate and size of the cracks were slower and more uniform, and there were no smaller coal fragments ejecting during the failure process of the coal samples. Meanwhile, the proportion of high-energy events released in coal samples experienced a decline after the treatment of the microwave. Moreover, microwave heating principally promoted the initiation and expansion of microcracks in coal samples under the influence of microwave power of 1 kW and a heating time of 120s, which may cause the overall damage of large fractures to break into multiple small and medium cracks. Based on the experimental results, the conceptual process of using microwave in weakening the bursting liability of coal seam was then proposed, which will be the meaningful reference for microwave-assisted oil recovery and coal bed methane production.

Study on the Mechanical Behavior and Acoustic Emission Properties of Granite under Triaxial Compression

To study the rock mechanical behaviors and damage process mechanism of granite samples under triaxial stress, conventional triaxial compression tests were carried out on an RMT-150B rock mechanics testing machine and acoustic emission detector. The test results show that the strength of the granite sample has a good linear relationship with the confining pressure, the cohesion force c of the granite samples is 29.37 MPa, and the internal friction angle is 54.23° by calculation based on the Mohr-Coulomb strength criterion. The larger the initial confining pressure of the rock sample is, the larger the crack initiation stress ( σ ci ) and dilatancy stress ( σ cd ) of the granite specimen are, the larger the energy values at the crack initiation point and dilatancy point are, and the larger the peak energy storage and energy release rate at the failure are. In the case of a small initial confining pressure, the AE ringdowning counts and the cumulative AE ringing counts increase to their maximum instantaneously at the peak stress point, and the damage of the sample develops rapidly. While the initial confining pressure is high, the AE ringing counts and the cumulative AE ringing counts of the granite specimens increase evenly, and the deformation damage of the granite specimens is slow. Before the crack initiation point, AE signals are mainly low-energy and low-frequency friction-type AE events, while after the dilatation point, AE signals of samples are mainly high-frequency and high-energy fracture-type AE events. The failure mode of granite samples judged by acoustic emission parameters according to the distribution of characteristic values of AE parameters RA and AF is consistent with the reality. The AE b value of the granite sample is large when the confining pressure is low, and there will be a sudden drop, the decrease time is late, and the decrease rate is large. Under the same stress level, the larger the confining pressure is, the larger the damage variable D is.