Fast Bursts Research Articles

Different bifurcations and slow dynamics underlying different stochastic dynamics of slow, medium, and fast bursting of β-cell

Different bifurcations and slow dynamics underlying different stochastic dynamics of slow, medium, and fast bursting of β-cell

The variable radio jet of the accreting neutron star the Rapid Burster

ABSTRACT The Rapid Burster is a unique neutron star low-mass X-ray binary system, showing both thermonuclear v-I and accretion-driven Type-II X-ray bursts. Recent studies have demonstrated how coordinated observations of X-ray and radio variability can constrain jet properties of accreting neutron stars – particularly when the X-ray variability is dominated by discrete changes. We present a simultaneous very large array, Swift, and INTErnational Gamma-Ray Astrophysics Laboratory observing campaign of the Rapid Burster to investigate whether its jet responds to Type-II bursts. We observe the radio counterpart of the X-ray binary at its faintest-detected radio luminosity, while the X-ray observations reveal prolific, fast X-ray bursting. A time-resolved analysis reveals that the radio counterpart varies significantly between observing scans, displaying a fractional variability of $38 \pm 5$ per cent. The radio faintness of the system prevents the robust identification of a causal relation between individual Type-II bursts and the evolution of the radio jet. However, based on a comparison of its low-radio luminosity with archival Rapid Burster observations and other accreting neutron stars, and on a qualitative assessment of the X-ray and radio light curves, we explore the presence of a tentative connection between bursts and jet: i.e. the Type-II bursts may weaken or strengthen the jet. The former of those two scenarios would fit with magnetorotational jet models; we discuss three lines of future research to establish this potential relation between Type-II bursts and jets more confidently.

Characterizing the aggregated encoding method utilizing bursts activated by a VCSEL-neuron with a feedback structure

The rapid advancement of photonic technologies has facilitated the development of photonic neurons that emulate neuronal functionalities akin to those observed in the human brain. Neuronal bursts frequently occur in behaviors where information is encoded and transmitted. Here, we present the demonstration of the bursting response activated by an artificial photonic neuron. This neuron utilizes a single vertical-cavity surface-emitting laser (VCSEL) and encodes multiple stimuli effectively by varying the spike count during a burst based on the polarization competition in the VCSEL. By virtue of the modulated optical injection in the VCSEL employed to trigger the spiking response, we activate bursts output in the VCSEL with a feedback structure in this scheme. The bursting response activated by the VCSEL-neuron exhibits neural signal characteristics, promising an excitation threshold and the refractory period. Significantly, this marks the inaugural implementation of a controllable integrated encoding scheme predicated on bursts within photonic neurons. There are two remarkable merits; on the one hand, the interspike interval of bursts is distinctly diminished, amounting to merely one twenty-fourth compared to that observed in optoelectronic oscillators. Moreover, the interspike period of bursts is about 70.8% shorter than the period of spikes activated by a VCSEL neuron without optical feedback. Our results may shed light on the analogy between optical and biological neurons and open the door to fast burst encoding-based optical systems with a speed several orders of magnitude faster than their biological counterparts.

A proposal for a fast infrared bursts detector

The gravitational wave GW170817 from a binary neutron star merger and the simultaneous electromagnetic detection of the GRB170717A by Fermi Gamma-Ray Space Telescope, opened a new era in the multi-messenger astronomy. Furthermore, the GRBs (Gamma-Ray Bursts) and the mysterious FRBs (Fast Radio Bursts) have sparked interest in the development of new detectors and telescopes dedicated to the time-domain astronomy across the electromagnetic spectrum. Time-domain astronomy aims to acquire fast astronomical bursts in temporal range between a few seconds down to 1 ns. Fast InfraRed Bursts (FIRB's) have been relatively understudied, often due to the lack of appropriate tools for observation and analysis. In this scientific scenario, the present contribution proposes a new detection system for ground-based reflecting telescopes working in the mid-infrared (mid-IR) range to search for astronomical FIRB's. Experience developed in the diagnostics for lepton circular accelerators can be used to design temporal devices for astronomy. Longitudinal diagnostic instruments acquire bunch-by-bunch particle shifts in the direction of flight, that is equivalent to temporal. Transverse device integrates the beam signal in the horizontal and vertical coordinates, as standard telescopes. The proposed instrument aims to work in temporal mode. Feasibility study tests have been carried out at SINBAD, the infrared beam line of DAFNE, the e+e- collider of INFN. SINBAD releases pulsed infrared synchrotron light with 2.7 ns separation. The front-end detector system has been evaluated to detect temporal fast infrared signals with 2–12 μm wavelengths and 1 ns rise times. The present contribute aims to be a step toward a feasibility study report.

Brain flexibility increases during the peri-ovulatory phase as compared to early follicular phase of the menstrual cycle

The brain operates in a flexible dynamic regime, generating complex patterns of activity (i.e. neuronal avalanches). This study aimed at describing how brain dynamics change according to menstrual cycle (MC) phases. Brain activation patterns were estimated from resting-state magnetoencephalography (MEG) scans, acquired from women at early follicular (T1), peri-ovulatory (T2) and mid-luteal (T3) phases of the MC. We investigated the functional repertoire (number of brain configurations based on fast high-amplitude bursts of the brain signals) and the region-specific influence on large-scale dynamics across the MC. Finally, we assessed the relationship between sex hormones and changes in brain dynamics. A significantly larger number of visited configurations in T2 as compared to T1 was specifically observed in the beta frequency band. No relationship between changes in brain dynamics and sex hormones was evident. Finally, we showed that the left posterior cingulate gyrus and the right insula were recruited more often in the functional repertoire during T2 as compared to T1, while the right pallidum was more often part of the functional repertoires during T1 as compared to T2. In summary, we showed hormone-independent increased flexibility of the brain dynamics during the ovulatory phase. Moreover, we demonstrated that several specific brain regions play a key role in determining this change.

A neutron fluence map of the Los Alamos National Laboratory Godiva IV critical assembly

A neutron fluence map and a total ionizing dose map of the Los Alamos National Laboratory Godiva IV fast burst critical assembly was generated using passive reactor dosimetry, comprised of sulfur pellets and thermoluminescent dosimeters. Godiva IV is an unmoderated, fast burst, critical assembly constructed of approximately 65 kg of highly enriched uranium fuel alloyed with 1.5 % molybdenum for strength. [1] The mapping was performed during a single 75.6 ºC temperature rise burst operation, with the top and sides of the cylindrical Godiva-IV Top Hat covered in passive dosimetry. Dosimetry was placed in a symmetric pattern around the Top Hat, with higher concentrations near the control rods and burst rod. A specific portion of the lower quadrant of the burst rod was mapped to confirm a testing region where the neutron fluence varied by no more than ± 5%. The results will be used to assess the neutron, gamma, and total ionizing dose environment in three-dimensional space around the assembly for higher fidelity experiment placement, active dosimetry positioning, and radiation field characterization.

Transverse MHD Waves as Signatures of Braiding-induced Magnetic Reconnection in Coronal Loops

A major coronal heating theory based on magnetic reconnection relies on the existence of braided magnetic field structures in the corona. In this small-angle reconnection scenario, numerical simulations indicate that the reconnected magnetic field lines are driven sideways by magnetic tension and can overshoot from their new rest position, thereby leading to low-amplitude transverse MHD waves. This provides an efficient mechanism for transverse MHD wave generation, and the direct causality also constitutes substantial evidence of reconnection from braiding. However, this wave-generation mechanism has never been directly observed. Recently, the telltale signature of small-angle reconnection in a sheared coronal structure has been identified through nanojets, which are small, short-lived, and fast jetlike bursts in the nanoflare range transverse to the guide field. We present for the first time Interface Region Imaging Spectrograph and Solar Dynamics Observatory observations of transverse MHD waves in a coronal loop that directly result from braiding-induced reconnection. The reconnection is identified by the presence of nanojets at the loop apex that release nanoflare-range energy. We find that the oscillations have an energy flux on the order of 106–108 erg cm−2 s−1, which is within the budget to power active region loops. The estimated kinetic and thermal energy from the nanojets is also sufficient to power the transverse waves and sustain the observed heating at the loop apex. This discovery provides major support to (a) existing theories that transverse MHD waves can be a signature of reconnection, (b) the existence of braiding in coronal structures, and (c) the coronal reconnection scenario identified by nanojets.

Godiva IV central cavity neutron environment characterization with threshold neutron detectors

Godiva IV is a cylindrical fast burst reactor comprised of approximately 65 kg of highly enriched uranium that is operated by Los Alamos National Laboratory and sited at the National Criticality Experiments Research Center at the Nevada National Security Site in Nevada in the United States. Godiva IV is typically operated at delayed critical and in the regime spanning from sub-prompt to super-prompt bursts. Godiva IV is used for sample irradiations, criticality safety demonstrations, dosimetry studies, and for studying super-prompt behavior. In preparation for both an upcoming experiment to reduce uncertainties in the prompt fission spectrum for 235U using threshold neutron detectors, and for future research using Godiva IV, it was desired to exercise the process of the selection of threshold neutron detectors/activation foils, radiation metrology, and the subsequent adjustment of the neutron spectrum. For this exercise, nine high purity threshold neutron detectors/activation foils were irradiated in a Godiva IV burst. The foils were then analyzed using a high-purity germanium detector in the NCERC counting laboratory to determine end of irradiation specific activities for available IRDFF-II reactions. This work summarizes the Godiva IV foil irradiation, radiation metrology results, and adjusted neutron spectrum. The results of this exercise ultimately characterized the neutron environment inside the sample irradiation cavity inside Godiva IV to a higher degree than previously performed, informed decisions for the upcoming larger scale experiment, and will inform future neutron spectrum characterizations at NCERC.

Radiation characterization summary for the WSMR fast burst reactor environment at the 6-inch location

The characterization of the neutron, prompt gamma-ray, and delayed gamma-ray radiation fields for the White Sands Missile Range (WSMR) Fast Burst Reactor, also known as molybdenum-alloy Godiva (Molly-G) has been assessed at the 6-inch irradiation location. The neutron energy spectra, uncertainties, and common radiation metrics are presented. Code-dependent recommended constants are given to facilitate the conversion of various dosimetry readings into radiation metrics desired by experimenters. The Molly-G core was designed and configured similarly to Godiva II, as an unreflected, unmoderated, cylindrical annulus of uranium-molybdenum-alloy fuel with molybdenum loading of 10%. At the 6-inch position, the axial fluence maximum is about 2.4×1013 n/cm2 per MJ of reactor energy; about 0.1% of the neutron fluence is below 1 keV and 96% is above 100 keV. The 1-MeV Damage-Equivalent Silicon (DES) fluence is estimated at 2.2×1013 n/cm2 per MJ of reactor energy. The prompt gamma-ray dose is roughly 2.5E+03 rad(Si) per MJ and the delayed gamma-ray dose is about 1.3E+03 rad(Si) per MJ.

Complex adaptive learning cortical neural network systems for solving time-fractional difference equations with bursting and mixed-mode oscillation behaviours

Complex networks have been programmed to mimic the input and output functions in multiple biophysical algorithms of cortical neurons at spiking resolution. Prior research has demonstrated that the ineffectual features of membranes can be taken into account by discrete fractional commensurate, non-commensurate and variable-order patterns, which may generate multiple kinds of memory-dependent behaviour. Firing structures involving regular resonator chattering, fast, chaotic spiking and chaotic bursts play important roles in cortical nerve cell insights and execution. Yet, it is unclear how extensively the behaviour of discrete fractional-order excited mechanisms can modify firing cell attributes. It is illustrated that the discrete fractional behaviour of the Izhikevich neuron framework can generate an assortment of resonances for cortical activity via the aforesaid scheme. We analyze the bifurcation using fragmenting periodic solutions to demonstrate the evolution of periods in the framework’s behaviour. We investigate various bursting trends both conceptually and computationally with the fractional difference equation. Additionally, the consequences of an excitable and inhibited Izhikevich neuron network (INN) utilizing a regulated factor set exhibit distinctive dynamic actions depending on fractional exponents regulating over extended exchanges. Ultimately, dynamic controllers for stabilizing and synchronizing the suggested framework are shown. This special spiking activity and other properties of the fractional-order model are caused by the memory trace that emerges from the fractional-order dynamics and integrates all the past activities of the neuron. Our results suggest that the complex dynamics of spiking and bursting can be the result of the long-term dependence and interaction of intracellular and extracellular ionic currents.

Next steps in high-repetition-rate laser development for Thomson scattering

Design of a next generation high-rep-rate laser system is underway, aiming for a maximum rep rate of 100 kHz for 1 ms. This will be a “pulse-burst” laser, which is a type of heat-capacity laser. Heat-capacity laser operation is characterized by a burst of pulses of limited duration, with burst length ≤100 ms and pulse rep rate ≥1 kHz. Waste heat accumulates in the laser rod during the burst. This heat is deposited evenly throughout the rod volume, with very little heat removed during the burst, such that temperature rises evenly across the rod radius. Thus beam distortion due to thermal gradients is small. Heat is removed from the rodafter the burst, with typically tens of seconds between bursts. Pulse-burst operation of flashlamp pumped Nd:YAG lasers is a cost-effective route to high-rep-rate capability. Pulse-burst laser systems with “fast burst” rep rates in the range of 10–20 kHz have been built for the Thomson scattering diagnostics on MST, NSTX-U, and LHD. For Thomson scattering diagnostic application, the typical requirements are 1064 nm, 1–2 J/pulse, ≤30 ns FWHM pulse, with a top-hat beam profile. A major requirement for this next generation laser system is flexibility in burst sequence programs, ranging from 1 kHz for 100 ms to 100 kHz for 1 ms, and a variety of scenarios in between so that operation can be tailored to plasma experiment requirements. Flashlamp pumping will be used for this next generation laser because it is inexpensive and flexible. A new switch-regulated flashlamp driver will provide improved flashlamp control at lower cost. Additional design issues such as the optimum flashlamp pumping spectrum and optimum Nd doping will be addressed. The use of commercial off-the-shelf components will be maximized in this laser system so that pulse-burst systems can be developed and built by others for new applications.

Silk Fibroin/PLA 3D Printed Composite Stent Fabricated through Direct Ink Write Technology

Bioresorbable alternatives are emerging on the market as alternatives to the cardiovascular stents that are implanted nowadays. Permanent drug-eluting stents are no longer the only viable option during an angioplasty surgical procedure. The new generation of medical stents aims to degrade the device within the artery walls after its function has been completed. In this context, biological materials that degrade inside the body without creating toxic residues such as silk fibroin (SF) are very promising materials for such applications. Moreover, SF has been reported to have non-thrombogenic properties and to reduce the immune response compared to other synthetic polymers, making it ideal for this application. SF has been printed through additive manufacturing techniques such as direct ink write. This study proposes to fabricate a composite stent by combining polylactic acid (PLA) and SF. In this way, it is expected to obtain a stent with potential for a two-phase drug release. A fast burst with the degradation of the SF and a slower drug release period with the degradation of the PLA. For this purpose, stents were fabricated with a PLA and chloroform ink (24.5 % w/v). The last layer of the stent was fabricated with a SF water-based ink at 56.69-60.09 % w/w. Finally, the stents were immersed at different times in ethanol and exposed to 30' of ultraviolet light for sterilization purposes. The degradation results indicate that 24h is sufficient to degrade almost completely the last layer of SF. These results are significant as the SF layer could potentially be used as a carrier for drug delivery, providing biocompatibility and drug release at the earliest post-intervention stage.

Structurally Stable Astigmatic Vortex Beams with Super-High Orbital Angular Momentum (ABCD Matrix Approach)

We have demonstrated efficiency of employing the ABCD matrix approach to transform higher-order structured Laguerre–Gaussian (sLG) beams into structurally stable astigmatic sLG (asLG) beams, highlighting their dynamics at propagating. Radical transformations of the beam structure by a cylindrical lens form not only orbital angular momentum (OAM) fast oscillations and bursts, but also make the asLG beams structurally unstable in propagation through cylindrical and spherical lenses when focusing paraxially. But, if the spherical lens performs a Fourier transform of the asLG beam after a cylindrical lens, the symmetric beam emerges at the lens focal plane with a sharp OAM dip; then, the OAM restores its former astigmatism, becoming structurally stable at the far diffraction domain. By investigating the beam structure at the focal area, we have showed that the OAM sharp dip is associated with nothing less than the process of dividing the OAM into the vortex and astigmatic constitutes predicted by Anan’ev and Bekshaev.

Integrating biomechanics with stakeholder perspectives to inform safety in grassroots dirt track racing

Grassroots dirt track racing is a foundational part of motorsports with a high risk of severe injury. This study aimed to gather perspectives and experiences of motorsports drivers surrounding safety and head acceleration events experienced during grassroots dirt track racing to inform strategies to improve driver safety. Thirteen drivers (n=9 who primarily race on dirt tracks; n=4 who primarily race on pavement tracks) with prior dirt track racing experience participated in separate, group-specific focus groups and/or one-on-one interviews where video, simulations of head motion, and head acceleration data were shared. Peak kinematics of laps and crash contact scenarios were recorded, and head perturbations (i.e., deviations in head motion relative to its moving-average trajectory) were quantified for each lap and presented through guided discussion. Responses were summarized using Rapid Assessment Process. Audio recordings and field notes were collected from focus groups and interviews and analyzed across 25 domains. Drivers described dirt track racing as short, fast bursts of racing. Benefits of dirt track racing for driver development were described, including learning car control. Drivers acknowledged risks of racing and expressed confidence in safety equipment but identified areas for improvement. Drivers observed lateral bouncing of the head in video and simulations but recognized that such motions were not noticed while racing. Track conditions and track type were identified as factors influencing head perturbations. Mean PLA (5.5 g) and PRV (3.07 rad/s) of perturbations experienced during racing laps and perturbation frequencies of 5 and 7 perturbations per second were reported. Generally, drivers accurately estimated the head acceleration magnitudes but were surprised by the frequency and maximum magnitude of perturbations. Maximum perturbation magnitudes (26.8 g and 19.0 rad/s) were attributed to hitting a “rut” in the dirt. Drivers described sudden stops, vertical loads due to landing from a large height, and impacts to the vehicle frame as crash events they physically feel the most. Summary statistics for crashes (medians = 7.30 g, 6.94 rad/s) were reported. Typical impact magnitudes measured in other sports (e.g., football) were provided for context. Upon reviewing the biomechanics, drivers were surprised that crash accelerations were relatively low compared to other contact/collision sports. Pavement drivers noted limited safety features in dirt track racing compared to pavement, including rigidity of vehicle frames, seat structure, seatbelt integration, and lack of oversight from sanctioning bodies. Most drivers felt seat inserts and head and neck restraints are important for injury prevention; however, usage of seat inserts and preferred head and neck restraint system differed among drivers. Drivers described their perspectives and experiences related to safety and identified strategies to improve safety in grassroots dirt track racing. Drivers expressed support for future safety research.

Prompt Detection of Fast Optical Bursts with the Vera C. Rubin Observatory

The transient optical sky has remained largely unexplored on very short timescales. While there have been some experiments searching for optical transients from minutes to years, none have had the capability to distinguish millisecond fast optical bursts (FOBs). Such very fast transients could be the optical counterparts of fast radio bursts, the prompt emission from γ-ray bursts, or other previously unknown phenomena. Here, we investigate a novel approach to the serendipitous detection of FOBs, which relies on searching for anomalous spatial images. In particular, due to their short duration, the seeing-distorted images of FOBs should look characteristically different than those of steady sources in a standard optical exposure of finite duration. We apply this idea to simulated observations with the Vera C. Rubin Observatory, produced by tracing individual photons through a turbulent atmosphere, and down through the optics and camera of the Rubin telescope. We compare these simulated images to steady-source star simulations in 15 s integrations, the nominal Rubin exposure time. We report the classification accuracy results of a neural network classifier for distinguishing FOBs from steady sources. From this classifier, we derive constraints in duration–intensity parameter space for unambiguously identifying FOBs in Rubin observations. We conclude with estimates of the total number of detections of FOB counterparts to FRBs expected during the 10 yr Rubin Legacy Survey of Space and Time.

Defibrillation test in paediatric patients: should be done?

Abstract Funding Acknowledgements Type of funding sources: None. The defibrillation test (DFT) of an implantable cardioverter-defibrillator (ICD) is performed to evaluate ventricular fibrillation detection and termination. In adults, routine defibrillation testing for transvenous ICD is less usually done as some studies found no advantages but some potentially risks associated with. On the other hand, implantation of ICDs in paediatric patients has different characteristics than in adults. The position of the defibrillation coil will change with the body’s growth and could reflect changes in the defibrillation vector. Also, the reasons of implantation of an ICD are different (ventricular arrhythmias frequently associated with adult’s myocardial infarction vs channelopathies, non-ischemic myocardiopathies and congenital heart defects in children and young). There is still lack of information about the utility of the DFT in paediatric patients. Objective To describe the characteristics of paediatric patients who underwent implantation of an ICD , results of DFT and follow-up. Methodology Retrospective cohort study of patients less than 21 years old who underwent implantation of an ICD in the lasts 10 years at a reference paediatric hospital. In DFT, VF was induced by T wave shock, fast burst pacing or continuous direct current. Response of ICD to VF was evaluated. Patients with failure to terminate VF by ICD were defibrillated with external defibrillator. Results 68 patients with 73 ICD implantations (five replacements). Median age was 13 years old. The youngest patient was 2 years old and the oldest 21 years old. 72.6% (53/73) of patients underwent DFT. In 90.6% (48/53) of them, a VF was induced. In two patients (4%, 2/48) the ICD did not terminate the VF. One of these patients had Danon syndrome and the VF did not terminate despite of maximum energy discharged and changes in the vector of defibrillation; the problem was fixed with replacement of the single coil lead by a dual coil system. The other patient had arrhythmogenic cardiomyopathy and the ICD did not detect the VF. During the follow up, there were 20 shocks in 13 patients. 13 shocks were appropriate (and successful). One patient died because of non-arrhythmic illness. Conclusions In paediatric patients, the defibrillation test is useful to ensure both adequate detection of malignant ventricular arrhythmias, as well as their ability to reverse them. Its lack of performance could affect 4% of the implants. Therefore, its performance in paediatric patients is recommended. There could be greater utility in patients with hypertrophic cardiomyopathy.

Neutron calorimeter development at fission and fusion pulsed neutron sources

A neutron calorimeter fielded in pulsed neutron irradiation experiments at the National Ignition Facility (NIF) and White Sands Missile Range Fast Burst Reactor (WSMR FBR) is described, and results are provided and discussed. The calorimeter is modular in design to allow fielding of various neutron absorber materials and thicknesses, as well as use at both fission and fusion sources, all of which has been done. Neutron calorimeters designed for fission sources have been fielded at fusion sources as well, but these instances are not documented in available literature—making this work novel. The functional calorimeter consists of a neutron absorber and two sheathed, grounded thermocouples secured within a subassembly made of thermally insulating materials. This subassembly is placed into a sealed vessel for material and facility safety considerations. The device was fielded at NIF in four polar-direct-drive exploding pusher shots and eleven WSMR FBR pulses. Calorimeter data from NIF experiments show a discernable thermal response accredited to neutron heating within the first 10 s, but the data are dominated by noise from ambient X-ray heating after time = 10 s post-pulse. This response is highly consistent between shots and linearly related to incident neutron fluence and neutron absorber thickness. A temperature rise of 1.1E−2 K/(1013 neutrons/cm2) per millimeter of absorber thickness was determined for both 0.4 mm and 1 mm thick depleted uranium absorbers with linear best fit R2 of 0.97 and 0.98 for each thickness and y-axis offsets of 8.8E−3 and 1.3E−2, respectively. WSMR FBR experiment data show a temperature rise of 6.2E−2 K/(1013 neutrons/cm2) with linear best fit R2 of 0.14 and y-axis offset of 7.6E−3 for a calorimeter with a 1 mm thick enriched boron carbide (10B4C) absorber, though it must be noted that device-to-device variability is significant at both facilities. These data are also affected by noise on a similar timescale as at NIF, though the noise is significantly lesser in magnitude but oscillatory.

Tidal Stripping of a White Dwarf by an Intermediate-mass Black Hole

During the inspiralling of a white dwarf (WD) into an intermediate-mass black hole (∼102−5 M ⊙), both gravitational waves (GWs) and electromagnetic (EM) radiation are emitted. Once the eccentric orbit’s pericenter radius approaches the tidal radius, the WD would be tidally stripped upon each pericenter passage. The accretion of this stripped mass would produce EM radiation. It is suspected that the recently discovered new types of transients, namely the quasiperiodic eruptions and the fast ultraluminous x-ray bursts, might originate from such systems. Modeling these flares requires a prediction of the amount of stripped mass from the WD and the details of the mass supply to the accretion disk. We run hydrodynamical simulations to study the orbital parameter dependence of the stripped mass. We find that our results match the analytical estimate that the stripped mass is proportional to z 5/2, where z is the excess depth by which the WD overfills its instantaneous Roche lobe at the pericenter. The corresponding fallback rate of the stripped mass is calculated, which may be useful in interpreting the individual flaring light curve in candidate EM sources. We further calculate the long-term mass-loss evolution of a WD during its inspiral and the detectability of the GW and EM signals. The EM signal from the mass-loss stage can be easily detected: the limiting distance is ∼320(M h/104 M ⊙) Mpc for the Einstein Probe. The GW signal, for space-borne detectors such as Laser Interferometer Space Antenna or TianQin, can be detected only within the Local Supercluster (∼33 Mpc).

MeV neutrino flash from neutron star mergers viar-process nucleosynthesis

AbstractDetection of kilonova AT2017gfo proves that binary neutron star mergers can be the dominant contributor to the production of heavy elements in our Universe. Neutrinos from the radioactive decay of heavy elements would be the most direct messengers of merger ejecta. Based on r-process nucleosynthesis calculations, we study the neutrinos emitted from the β-decay of r-process elements and find that about half of the β-decay energy is carried away by neutrinos. The neutrino energy generation rate remains approximately constant at the early stage (t ≲ 1 s) and then decays as a power-law function with an index of −1.3. This powers a short-lived fast neutrino burst with a peak luminosity of ∼1049 erg s−1 in the early stage. Observation of neutrinos from neutron star mergers will be an important step towards understanding the properties of extremely neutron-rich nuclei and r-process nucleosynthesis, since the dominant contribution to the early time neutrino production is from nuclides near the r-process path. The typical neutrino energy is ≲8 MeV, which is within the energy ranges of the water-Cherenkov neutrino detectors such as Super-Kamiokande and future Hyper-Kamiokande, but the extremely low neutrino flux and event rate in our local Universe challenge the detection of the neutrino flashes.

Fractal resistive–capacitive–inductive shunted Josephson junction: Theoretical investigation and microcontroller implementation

The paper captures the analytical and numerical investigations of the fractal resistive–capacitive–inductive shunted Josephson junction (FRCLSJJ) and its microcontroller implementation (MCI). The rate equations of FRCLSJJ are established and based on the Routh–Hurwitz criterion, two equilibrium points are reported with one unconditionally stable and the other unstable for the direct current used for junction excitation less than or equal to one. When this current is greater than one, the FRCLSJJ exhibits no equilibrium point. The contribution of fractal parameters to the dynamics of FRCLSJJ is investigated on fast bursting, regular spiking, relaxation behaviors, and periodic bursting. The FRCLSJJ is characterized by fine dynamics such as different presentations of complex behaviors, the coexistence of periodic and chaotic hidden attractors, chaotic hidden attractors, antimonotonicity, periodic attractors, and periodic and chaotic bubble hidden attractors for varying system parameters. And in the last section of the investigation, the MCI of FRCSJJ is realized with the results establishing a qualitative agreement with numerically simulated results.