Localized Bursts Research Articles

Search for the Hawking radiation of primordial black holes: prospective sensitivity of LHAASO

Primordial black holes (PBHs), more generally, BHs, undergo evaporation and, in principle, will end their lives in bursts of very high-energy gamma rays. The notable aspect of the PBHs with an initial mass of ∼ 1014 g is that they are expected to end their lives today. In this work, we assess the potential sensitivity of the Large High Altitude Air Shower Observatory (LHAASO) in detecting the local burst rate density of PBHs. Our results suggest that LHAASO is capable of probing for PBH bursts within a proximity of ∼ 0.1 pc from the Sun, measuring a local burst rate density of ∼ 1200 (or 700)pc-3 yr-1 with 99% confidence during a 3-year (or 5-year) observational campaign. This level of sensitivity surpasses the most rigorous observational constraint provided by the High Altitude Water Cherenkov Observatory (HAWC) by an order of magnitude. Additionally, we propose data analysis strategies for LHAASO to optimize the search for PBHs and reach its potential detection limits.

From cell intercalation to flow, the importance of T1 transitions

T1 transitions, also called cell intercalations, are important sources of fluidization of epithelial cell monolayers. We use a multiphase field model to quantify this tissue fluidization in terms of the relative dispersion of cells and characterize the T1 flow profile. We show that the ensemble-averaged flow profile of a T1 transition has a saddle-point pattern accompanied by a localized burst in cell speed. Although the temporal evolution of the relative dispersion of cells depends on specific model details, the different dispersion curves collapse robustly onto a linear function of the number of T1 transitions, implying an important connection between T1 transitions and mixing in dense systems. Published by the American Physical Society 2024

Multiscale interaction underlying 2022 concurrent extreme precipitation in Pakistan and heatwave in Yangtze River Valley

Unprecedentedly extreme precipitation occurred in Pakistan (PAK), and mega heat waves persisted along the Yangtze River Valley (YRV) from July to August 2022. Using the advanced multiscale window transform-based canonical transfer attribution framework, we quantitatively delineated intra-scale and inter-scale interactions leading to record-breaking spatially concurrent extremes in 2022 and comprehensively revealed differences in dynamic processes affecting extreme events in July and August. The basic flow scale window lost the available potential energy (APE), and through APE canonical transfers to the intraseasonal-scale and synoptic-scale windows, the inter-scale dynamic processes and barotropic instability of the basic flow scale preserved the concurrent extreme in July. In August, the eruptive synoptic-scale kinetic energy convergence provided dynamic conditions for the sinking motion of the YRV and its advection to PAK from the Indian Ocean. Consequently, the interaction between high- and low-frequency processes drove atmospheric circulation in summer, but the high-frequency process in August played a vital role in extreme events. Additionally, the heat source in the tropical western-central Pacific is considered one of the key drivers for localized repetitive bursts of energy. This study emphasizes both the interactions between multiple scales of atmospheric dynamics and reveals the driving mechanisms behind the impacts of warming on extreme events, linking the external forcing issue with the free problem of atmospheric internal instability.

DEM analysis on diffuse failure of soil slope triggered by earthquakes

Earthquake-induced diffuse landslide can cause considerable harm. This study used discrete element modeling (DEM) to investigate the diffuse failure of soil slopes triggered by earthquakes. Initially, the DEM was validated through demonstrating satisfactory agreement with the experimental results of a shaking table test. Subsequently, the time and most realistic location of diffuse failure occurrence was quantified using discrete second-order work. Diffuse failure was associated with abrupt fluctuation of the second-order work and a local burst of kinetic energy. Within the context of second-order analysis, the frictional resistance of the slope was analyzed. Both the in-phase and the out-of-phase evolutions of frictional resistance and seismic loading were captured. The distinctive in-phase response was identified as an important feature of diffuse failure. Moreover, the predominant influence of particle rolling behavior on frictional resistance development during diffuse failure progression was highlighted. The magnitude and anisotropy of the contact force are profoundly influenced by the input vibration amplitude, resulting in variations in frictional resistance, which suggests that stress-induced anisotropy plays a crucial role in diffuse failure. The results of this study shed light on the grain-scale failure mechanisms of earthquake-induced landslides, and serve as the basis for elucidating the failure behavior of seismic-induced landslides.

Multi-scale modelling of location- and frequency-dependent synaptic plasticity induced by transcranial magnetic stimulation in the dendrites of pyramidal neurons.

Repetitive transcranial magnetic stimulation (rTMS) induces long-term changes of synapses, but the mechanisms behind these modifications are not fully understood. Although there has been progress in the development of multi-scale modeling tools, no comprehensive module for simulating rTMS-induced synaptic plasticity in biophysically realistic neurons exists.. We developed a modelling framework that allows the replication and detailed prediction of long-term changes of excitatory synapses in neurons stimulated by rTMS. We implemented a voltage-dependent plasticity model that has been previously established for simulating frequency-, time-, and compartment-dependent spatio-temporal changes of excitatory synapses in neuronal dendrites. The plasticity model can be incorporated into biophysical neuronal models and coupled to electrical field simulations. We show that the plasticity modelling framework replicates long-term potentiation (LTP)-like plasticity in hippocampal CA1 pyramidal cells evoked by 10-Hz repetitive magnetic stimulation (rMS). This plasticity was strongly distance dependent and concentrated at the proximal synapses of the neuron. We predicted a decrease in the plasticity amplitude for 5 Hz and 1 Hz protocols with decreasing frequency. Finally, we successfully modelled plasticity in distal synapses upon local electrical theta-burst stimulation (TBS) and predicted proximal and distal plasticity for rMS TBS. Notably, the rMS TBS-evoked synaptic plasticity exhibited robust facilitation by dendritic spikes and low sensitivity to inhibitory suppression. The plasticity modelling framework enables precise simulations of LTP-like cellular effects with high spatio-temporal resolution, enhancing the efficiency of parameter screening and the development of plasticity-inducing rTMS protocols.

MiR-7 controls glutamatergic transmission and neuronal connectivity in a Cdr1as-dependent manner

The circular RNA (circRNA) Cdr1as is conserved across mammals and highly expressed in neurons, where it directly interacts with microRNA miR-7. However, the biological function of this interaction is unknown. Here, using primary cortical murine neurons, we demonstrate that stimulating neurons by sustained depolarization rapidly induces two-fold transcriptional upregulation of Cdr1as and strong post-transcriptional stabilization of miR-7. Cdr1as loss causes doubling of glutamate release from stimulated synapses and increased frequency and duration of local neuronal bursts. Moreover, the periodicity of neuronal networks increases, and synchronicity is impaired. Strikingly, these effects are reverted by sustained expression of miR-7, which also clears Cdr1as molecules from neuronal projections. Consistently, without Cdr1as, transcriptomic changes caused by miR-7 overexpression are stronger (including miR-7-targets downregulation) and enriched in secretion/synaptic plasticity pathways. Altogether, our results suggest that in cortical neurons Cdr1as buffers miR-7 activity to control glutamatergic excitatory transmission and neuronal connectivity important for long-lasting synaptic adaptations.

Correction to: An 8 per cent determination of the Hubble constant from localized fast radio bursts

Correction to: An 8 per cent determination of the Hubble constant from localized fast radio bursts

Effect of Phosphatidylethanolamine on Pore Formation Induced by the Antimicrobial Peptide PGLa.

Most antimicrobial peptides (AMPs) induce pore formation and a burst of lipid bilayers and plasma membranes. This causes severe leakage of the internal contents and cell death. The AMP PGLa forms nanopores in giant unilamellar vesicles (GUVs) comprising dioleoylphosphatidylcholine (DOPC) and dioleoylphosphatidylglycerol (DOPG). We here elucidated the effect of the line tension of a prepore rim on PGLa-induced nanopore formation by investigating the interaction of PGLa with single GUVs comprising dioleoylphosphatidylethanolamine (DOPE)/DOPG (6:4) in buffer using the single GUV method. We found that PGLa forms nanopores in the GUV membrane, which evolved into a local burst and burst of GUVs. The rate of pore formation in DOPE/DOPG-GUVs was smaller than that in DOPC/DOPG-GUVs. PGLa is located only in the outer leaflet of a GUV bilayer just before a fluorescent probe AF647 leakage from the inside, indicating that this asymmetric distribution induces nanopore formation. PGLa-induced local burst and burst of GUVs were observed at 10 ms-time resolution. After nanopore formation started, dense particles and small vesicles appeared in the GUVs, followed by a decrease in the GUV diameter. The GUV was finally converted into smaller GUV or lipid membrane aggregates. We discuss the mechanisms of PGLa-induced nanopore formation and its direct evolution to a GUV burst.

Unravelling the jerky glide of dislocations in body-centred cubic crystals.

In situ straining tests in high purity α-Fe thin foils at low temperatures1 have demonstrated that crystal line defects, called dislocations, have a jerky type of motion made of intermittent long jumps of several nanometres. This observation conflicts with the standard Peierls mechanism for plastic deformation in body-centred cubic crystals, where the screw dislocation jumps are limited by inter-reticular distances, that is, distances of a few angstroms. Employing atomic-scale simulations, we show that although the short jumps are initially more favourable, their realization requires the propagation of a kinked profile along the dislocation line, which yields coherent atomic vibrations acting as travelling thermal spikes. Such local heat bursts favour the thermally assisted nucleation of new kinks in the wake of primary ones. The accumulation of new kinks leads to long dislocation jumps like those observed experimentally. Our study constitutes an important step towards predictive atomic-scale theory for materials deformation.

FRB 20210405I: a nearby Fast Radio Burst localized to sub-arcsecond precision with MeerKAT

ABSTRACT We present the first sub-arcsecond localized Fast Radio Burst (FRB) detected using MeerKAT. FRB 20210405I was detected in the incoherent beam using the MeerTRAP pipeline on 2021 April 05 with a signal to noise ratio of 140.8 and a dispersion measure of 565.17 pc cm−3. It was detected while MeerTRAP was observing commensally with the ThunderKAT large survey project, and was sufficiently bright that we could use the ThunderKAT 8 s images to localize the FRB. Two different models of the dispersion measure in the Milky Way and halo suggest that the source is either right at the edge of the Galaxy, or outside. This highlights the uncertainty in the Milky Way dispersion measure models, particularly in the Galactic Plane, and the uncertainty of Milky Way halo models. Further investigation and modelling of these uncertainties will be facilitated by future detections and localizations of nearby FRBs. We use the combined localization, dispersion measure, scattering, specific luminosity, and chance coincidence probability information to find that the origin is most likely extra-galactic and identify the likely host galaxy of the FRB: 2MASS J1701249−4932475. Using SALT spectroscopy and archival observations of the field, we find that the host is a disc/spiral galaxy at a redshift of z = 0.066.

Intermittent tensile deformation of silver microcastings: Influence of the strain rate

We compare the uniaxial tensile behavior of µm-scale cast silver tensile specimens at strain rates of 10−3 s−1 and 2 s−1 to find no major impact of the strain rate on either of the flow stress, work hardening, or strain to fracture. Plastic deformation progresses at both strain rates mainly through local slip bursts of variable amplitude. Within uncertainty in higher strain rate data, the complementary cumulative distribution function of the slip burst amplitudes remains unchanged. A statistical analysis of the time and strain increments between consecutive events suggests that slip bursts are predominantly triggered, not by time elapsed between events, but rather by the progression of deformation expressed in terms of stress and strain.

Investigating Cosmological Models and the Hubble Tension Using Localized Fast Radio Bursts

We use the dispersion measure (DM) and redshift measurements of 24 localized fast radio bursts (FRBs) to compare cosmological models and investigate the Hubble tension. Setting a flat prior on the DM contribution from the Milky Way’s halo, , the best fit for flat ΛCDM is obtained with a Hubble constant and a median matter density Ωm ≈ 0.66. The best fit for the R h = ct universe is realized with . We emphasize that the H 0 measurement depends sensitively on the prior. Since flat ΛCDM has one more free parameter, R h = ct is favored by the Bayesian Information Criterion (BIC) with a likelihood of ∼73% versus ∼27%. Through simulations, we find that if the real cosmology is ΛCDM, a sample of ∼1150 FRBs in the redshift range 0 < z < 3 would be sufficient to rule out R h = ct at a 3σ confidence level, while ∼550 FRBs would be necessary to rule out ΛCDM if the real cosmology is instead R h = ct. The required sample sizes are different, reflecting the fact that the BIC imposes a severe penalty on the model with more free parameters. We further adopt a straightforward method of deriving an upper limit to H 0, without needing to consider the poorly known probability distribution of the DM contributed by the host galaxy. The theoretical DM contribution from the intergalactic medium (DMIGM) at any z is proportional to H 0. Thus, requiring the extragalactic DMext to be larger than DMIGM delimits H 0 to the upside. Assuming flat ΛCDM, we have H 0 < 89.0 km s−1 Mpc−1 at a 95% confidence level.

Evaporation-Driven Cellular Patterns in Confined Hyperelastic Hydrogels.

When a hyperelastic hydrogel confined between two parallel glass plates begins to dry from a lateral boundary, the volume lost by evaporation is accommodated by an inward displacement of the air-hydrogel interface that induces an elastic deformation of the hydrogel. Once a critical front displacement is reached, we observe intermittent fracture events initiated by a geometric instability resulting in localized bursts at the interface. These bursts relax the stresses and irreversibly form air cavities that lead to cellular networks. We show that the spatial extent of the strain field prior to a burst, influenced by the air-hydrogel interfacial tension and the confinement of the gel, determines the characteristic size of the cavities.

The unseen host galaxy and high dispersion measure of a precisely localized fast radio burst suggests a high-redshift origin

ABSTRACT FRB 20210912A is a fast radio burst (FRB), detected and localized to subarcsecond precision by the Australian Square Kilometre Array Pathfinder. No host galaxy has been identified for this burst despite the high precision of its localization and deep optical and infrared follow-up, to 5σ limits of R = 26.7 mag and Ks = 24.9 mag with the Very Large Telescope. The combination of precise radio localization and deep optical imaging has almost always resulted in the secure identification of a host galaxy, and this is the first case in which the line of sight is not obscured by the Galactic disc. The dispersion measure of this burst, DMFRB = 1233.696 ± 0.006 pc cm−3, allows for a large source redshift of z &amp;gt; 1 according to the Macquart relation. It could thus be that the host galaxy is consistent with the known population of FRB hosts, but is too distant to detect in our observations (z &amp;gt; 0.7 for a host like that of the first repeating FRB source, FRB 20121102A); that it is more nearby with a significant excess in DMhost, and thus dimmer than any known FRB host; or, least likely, that the FRB is truly hostless. We consider each possibility, making use of the population of known FRB hosts to frame each scenario. The fact of the missing host has ramifications for the FRB field: even with high-precision localization and deep follow-up, some FRB hosts may be difficult to detect, with more distant hosts being the less likely to be found. This has implications for FRB cosmology, in which high-redshift detections are valuable.

A stochastic stability equation for unsteady turbulence in the stable boundary layer

AbstractThe atmospheric boundary layer is particularly challenging to model in conditions of stable stratification, which can be associated with intermittent or unsteady turbulence. We develop a modelling approach to represent unsteady mixing possibly associated with turbulence intermittency and with unresolved fluid motions, called sub‐mesoscale motions. This approach introduces a stochastic parametrisation by randomising the stability correction used in the classical Monin–Obhukov similarity theory. This randomisation alters the turbulent momentum diffusion and accounts for sporadic events that cause unsteady mixing. A data‐driven stability correction equation is developed, parametrised, and validated with the goal to be modular and easily combined with existing Reynolds‐averaged Navier–Stokes models. Field measurements are processed using a statistical model‐based clustering technique, which simultaneously models and classifies the non‐stationary stable boundary layer. The stochastic stability correction obtained includes the effect of the static stability of the flow on the resolved flow variables, and additionally includes random perturbations that account for localised intermittent bursts of turbulence. The approach is general and effectively accounts for the stochastic mixing effects of unresolved processes of possibly unknown origin.

Research on a Typical Casing Failure during Drilling of Cement Plugs in Ultradeep Wells

Summary Among the casing failures in 46 ultradeep wells in a particular block, 11 ultradeep wells had the same casing failure forms occur during the drilling of cement plugs. The casing failure forms are local bending deformation and local internal pressure damage, which eventually led to a local burst failure of the casing in the 11 typical ultradeep wells. Therefore, a casing strength checking model is established to investigate the primary reasons for the local burst failure of the casing and the local burst failure mechanism of the casing. A case study is performed on casing in typical ultradeep wells with force conditions to evaluate the safety state of the casing and make necessary recommendations to improve its safety. The obtained results indicate that an abnormally high dogleg (AHD), a decrease in the temperature at the bottom of the casing, and an annulus trap space are the characteristics of typical ultradeep wells, and the local burst failure of the casing is caused by the coupled superposition impact of a decrease in the annulus pressure buildup (APB), the casing temperature effect, and the magnification effect of the casing bending stress. The safety factor of the casing can be increased by changing the operation parameters and the material properties of the casing. To address the casing failure problems during the drilling of cement plugs in typical ultradeep wells, the protection and monitoring of the seal quality of the cement sheath should be improved to avoid expansion of the well diameter and formation of the annulus trap space. The casing strength and the injection temperature of the drilling fluid can be increased, and the drilling fluid displacement can be decreased.

Consistent constraints on the equivalence principle from localized fast radio bursts

ABSTRACT Fast radio bursts (FRBs) are short astrophysical transients of extragalactic origin. Their burst signal is dispersed by the free electrons in the large-scale-structure (LSS), leading to delayed arrival times at different frequencies. Another potential source of time delay is the well known Shapiro delay, which measures the space–space and time–time metric perturbations along the line-of-sight. If photons of different frequencies follow different trajectories, i.e. if the universality of free fall guaranteed by the weak equivalence principle (WEP) is violated, they would experience an additional relative delay. This quantity, however, is not observable at the background level as it is not gauge independent, which has led to confusion in previous papers. Instead, an imprint can be seen in the correlation between the time delays of different pulses. In this paper, we derive robust and consistent constraints from twelve localized FRBs on the violation of the WEP in the energy range between 4.6 and 6 meV. In contrast to a number of previous studies, we consider our signal to be not in the model, but in the covariance matrix of the likelihood. To do so, we calculate the covariance of the time delays induced by the free electrons in the LSS, the WEP breaking terms, the Milky Way and host galaxy. By marginalizing both host galaxy contribution and the contribution from the free electrons, we find that the parametrized post-Newtonian parameter γ characterizing the WEP violation must be constant in this energy range to 1 in 1013 at 68 per cent confidence. These are the tightest constraints to-date on Δγ in this low-energy range.

1777-P: Three-Dimensional Imaging Reveals Pancreatic Islet Fast Calcium Wave Origin Formation

Pulsatile insulin secretion triggered by global calcium waves within pancreatic β cells is essential to blood glucose homeostasis. The calcium wave propagation forms by gap junction coupling among beta cells, but the emergence of wave origins is still unclear. We developed a 3D islet calcium imaging system and adapted data processing methods to observe and analyze islet calcium wave propagation quantitatively. A global fast-traveling calcium wave identifies in all kinds of oscillation modes. The calcium waves could initiate by multiple conserved β-cell clusters. We showed that the beta cell subpopulation, which first responded to high glucose stimulation, would partially contribute to calcium wave origin formation. To determine whether the spatial distribution of alpha or delta cells affects wave origin formation, we developed transgenetic mice that all islet cells were directly labeled with GCaMP6f, and alpha cells or delta cells were marked with tdTomato by Cre-Loxp strategy. Our data suggested that delta cells in the periphery modulated wave origins by electrical coupling and inhibitory paracrine interaction. Population oscillator models based on natural islet 3D structures reproduce the wave propagation observed in experiments. Interestingly, 3D imaging showed only local calcium wave bursts in ob/ob mice islets, and Immunofluorescence staining showed those sporadic bursts also correlated to delta cells. Disclosure Y.Yu: None.

Cosmological-model-independent Determination of Hubble Constant from Fast Radio Bursts and Hubble Parameter Measurements

We establish a cosmological-model-independent method to determine the Hubble constant H 0 from the localized fast radio bursts (FRBs) and the Hubble parameter measurements from cosmic chronometers and obtain a first such determination H 0 = 71 ± 3 km s−1 Mpc−1, with an uncertainty of 4%, from the eighteen localized FRBs and nineteen Hubble parameter measurements in the redshift range 0 < z ≤ 0.66. This value, which is independent of the cosmological model, is consistent with the results from the nearby Type Ia supernovae (SNe Ia) data calibrated by Cepheids and the Planck cosmic microwave background radiation observations at the 1σ and 2σ confidence level, respectively. Simulations show that the uncertainty of H 0 can be decreased to the level of that from the nearby SNe Ia when mock data from 500 localized FRBs with 50 Hubble parameter measurements in the redshift range of 0 < z ≤ 1 are used. Since localized FRBs are expected to be detected in large quantities, our method will be able to give a reliable and more precise determination of H 0 in the very near future, which will help us to figure out the possible origin of the Hubble constant disagreement.

Dynamic length scale and weakest link behavior in crystal plasticity

Irreversible deformation of crystals is often characterized by stochastic scale-free distributed intermittent local plastic bursts. Quenched obstacles with short-range interaction were found to limit the size of these events, which was termed as a transition from wild to mild fluctuations. Here, we show by analyzing the local yield thresholds in a discrete dislocation model that a dynamic length scale can be introduced based on weakest link principles, and this scale characterizes the extension of plastic events. The interplay between long-range dislocation interactions and short-range quenched disorder is found to destroy scale-free dynamical correlations, thus leading to event localization (that is, shortening of the length scale) which explains the crossover between the wild and mild regimes. Several methods are presented to determine the dynamic length scale which can be generalized to other types of heterogeneous materials.