Onset Of Burst Research Articles

Probability of Spring Frosts, Not Growing Degree-Days, Drives Onset of Spruce Bud Burst in Plantations at the Boreal-Temperate Forest Ecotone.

Climate warming-driven early leaf-out is expected to increase forest productivity but concurrently increases leaf exposure to spring frosts, which could reduce forests' net productivity. We hypothesized that due to their damaging effect on buds, spring frosts exert a stronger control on bud phenology than do growing degree-days. We monitored bud flush phenology of three white spruce seed sources (one local seed source from the boreal mixedwood forest and two seed sources from the temperate forest), one black spruce seed source originating from the boreal mixedwood forest and four nonlocal Norway spruce seed sources in 2016 and 2017 in two plantations located on both sides of the temperate-boreal mixedwood forest ecotone in eastern Canada (Quebec). We aimed to determine inter- and intraspecies variations in bud break timing and sensitivity to air temperature and photoperiod. We expected that bud break timing for boreal species and seed sources would be better synchronized with the decrease in frost probability than for nonlocal species and seed sources. We used mixed binomial regressions and AICc model selection to determine the best environmental variables predicting each transition from one stage of bud phenology to the next. At both plantation sites, white spruce bud flush began and ended earlier compared to black and Norway spruce. Buds of all spruce species were sensitive to frost probability for early phenological stages, whereas growing degree-days controlled the remaining stages. Photoperiod sensitivity was higher for white spruce compared to black and Norway spruce and reached its maximum in the temperate forest. At intraspecies level, the two southern white spruce seed sources opened their buds earlier than the local source and were more sensitive to photoperiod, which increased their exposure to spring frosts. Onset of spruce bud flush is driven by spring frosts and photoperiod, but once started, bud phenology responds to temperature. The high photoperiod sensitivity in white spruces could counterbalance climate warming and limit future premature leaf-out, whereas the low photoperiod sensitivity in black spruce should not restrain leaf-out advancement with climate warming. Our results call for adapting the temperature-driven hypotheses of ecophysiological models predicting leaf-out to include spring frost probability.

D-serine regulation of the timing and architecture of the inspiratory burst in neonatal mice

d-serine, released from mouse medullary astrocytes in response to increased CO2 levels, boosts the respiratory frequency to adapt breathing to physiological demands. We analyzed in mouse neonates, the influence of d-serine upon inspiratory/expiratory durations and the architecture of the inspiratory burst, assessed by pwelch's power spectrum density (PSD) and continuous wavelet transform (CWT) analyses. Suction electrode recordings were performed in slices from the ventral respiratory column (VRC), site of generation of the respiratory rhythm, and in brainstem-spinal cord (en bloc) preparations, from the C5 ventral roots, containing phrenic fibers that in vivo innervate and drive the diaphragm, the main inspiratory muscle.In en bloc and slice preparations, d-serine (100 μM) reduced the expiratory, but not the inspiratory duration, and increased the frequency and the regularity of the respiratory rhythm. In en bloc preparations, d-serine (100 μM) also increased slightly the amplitude of the integrated inspiratory burst and the area under the curve of the integrated inspiratory burst, suggesting a change in the recruitment or the firing pattern of neurons within the burst. Time-frequency analyses revealed that d-serine changed the burst architecture of phrenic roots, widening their frequency spectrum and shifting the position of the core of firing frequencies towards the onset of the inspiratory burst. At the VRC, no clear d-serine induced changes in the frequency-time domain could be established. Our results show that d-serine not only regulates the timing of the respiratory cycle, but also the recruitment strategy of phrenic motoneurons within the inspiratory burst.

Lactate Attenuates Synaptic Transmission and Affects Brain Rhythms Featuring High Energy Expenditure.

SummaryLactate shuttled from blood, astrocytes, and/or oligodendrocytes may serve as the major glucose alternative in brain energy metabolism. However, its effectiveness in fueling neuronal information processing underlying complex cortex functions like perception and memory is unclear. We show that sole lactate disturbs electrical gamma and theta-gamma oscillations in hippocampal networks by either attenuation or neural bursts. Bursting is suppressed by elevating the glucose fraction in substrate supply. By contrast, lactate does not affect electrical sharp wave-ripple activity featuring lower energy use. Lactate increases the oxygen consumption during the network states, reflecting enhanced oxidative ATP synthesis in mitochondria. Finally, lactate attenuates synaptic transmission in excitatory pyramidal cells and fast-spiking, inhibitory interneurons by reduced neurotransmitter release from presynaptic terminals, whereas action potential generation in the axon is regular. In conclusion, sole lactate is less effective and potentially harmful during gamma-band rhythms by omitting obligatory ATP delivery through fast glycolysis at the synapse.

Grapevine Latent Bud Dormancy and Shoot Development

Grapevine development comprises different phenological stages from bud break to berry maturation which are mainly temperature and water dependent. Pre bud break, there is a crucial stage called dormancy which can be divided in two periods: endodormancy and ecodormancy. Climate change (increase in average temperatures and drought) may accelerate the onset of bud burst, however with greater heterogeneity, thus increasing the risk of shoot exposure to abiotic and biotic constraints. Obviously, this could lead to yield and quality issues. In this regard, the ability to assess when climatic conditions are suitable for dormancy release and to predict the date of bud break is important.

Automated Detection of Onset and Offset of Multiunit Inspiratory Burst Activity Using a Threshold and Window Independent Approach

In animal models, inspiratory electromyogram (EMG) or neurogram (ENG) multiunit activity recorded with various electrode configurations are commonly used for assessing multiple aspects of central respiratory network control. The cyclic inspiratory electrogram ‘bursts’ are complex, and generally characterized by an augmenting fast‐oscillatory amplitude pattern that begins to decrement after peak activity. Accurate automated capture of the bounds of these bursts in time would allow for in‐depth analysis of intra‐burst features, but is difficult to achieve due to high stochasticity of the underlying network interactions, particularly at the decrementing phase of the burst. Common approaches to estimate these bounds often use threshold and/or window‐based smoothing or binning methods that minimize signal variance around the overall trend. These approaches rely on conservation of burst‐to‐burst characteristics to maintain accuracy and consistency; however, features underlying the onset and/or offset of the burst may be obscured and not be adequately captured. To overcome this limitation, we present an unbiased method for automated estimation of burst bounds that is not dependent on thresholding or windowing methods, and assess the capabilities of this method on rectified diaphragm EMG and phrenic ENG time‐series bursts recorded from urethane anesthetized Sprague‐Dawley rats. For our method, each burst is initially identified and approached using an arbitrary time point between adjacent bursts that contains the burst onset and extends toward the center of the burst. A multidimensional time‐invariant distribution is then achieved using time‐delay embedding of all amplitude values that occur at time‐series slope inversions. The variability and magnitude of the distribution are grouped using spectral clustering to identify potential timings for transitions from non‐burst to burst activity, and the maximum second differential of a running variance is identified as the most likely transition and established as the burst onset. The entire process is then repeated from an arbitrary point containing the burst offset to similarly identify the most likely offset transition, after which the next burst is identified and evaluated. This process is then repeated for each burst in the time‐series. The algorithm was evaluated by comparing automated and manual selection of burst bounds in both phrenic nerve ENG and diaphragm EMG recordings. Preliminary comparisons show a mean difference of inspiratory burst onset: 9.0±6.2 ms, offset: 16.6±8.7 ms, and duration: 24.2±11.8 ms in phrenic ENG, and a mean difference of inspiratory burst onset: 7.2±2.8 ms, offset: 36.4±7.3 ms, and duration 37.4±5.8 ms in diaphragm EMG, which is similar to that observed for manual bounds selection between individuals. This algorithm rapidly processes data (approximately 25 bursts/s) and maintains accuracy despite changes in burst amplitude and/or frequency; thus, it presents an efficient and consistent method for high throughput burst identification that may facilitate burst analysis for long duration time series data.Support or Funding InformationNIH NS101737; Thomas Hartman Center for Parkinson’s Disease Research at Stony Brook University

Spectropolarimetric Imaging of Metric Type III Solar Radio Bursts

We present low-frequency (80 – 240 MHz) radio observations of circular polarization in 16 isolated type III solar radio bursts using the Murchison Widefield Array (MWA) between August 2014 and November 2015. For most of the bursts, near burst onset, we find on average $9\%$ circular polarization at 80 MHz and $22\%$ at 240 MHz whereas these percentages are $5\%$ and $20\%$ near burst maximum. The polarization fractions are neither constant in time nor uniform over the spatial extents of the bursts. We measure polarization fractions as a function of burst source’s position. On average, near both burst onset and maximum, we find higher polarization near the disk center and lower polarization when the burst source is near the limb. We study total intensity (Stokes $I$), circularly polarized intensity (Stokes $V$), and polarization fraction ($| V| /I$) profiles for type III bursts with and without source motion as a function of position at times when the intensity of bursts is maximum. For the burst event with no source motion, we find symmetric profiles for Stokes $I$, $V$, and $| V| /I$. We find symmetric $I$ and $V$ but asymmetric $| V| /I$ profiles for burst events which have source motion. We argue that this is due to the fundamental emission at the front of a type III electron beam and motion of the burst source. We then perform spectropolarimetric imaging studies of moving burst sources and analyze their motion. At burst onset, we obtain relatively higher polarization fractions, which is considered to be due to a large contribution from fundamental plasma emission at the front of the beam. At burst maximum, the polarization fraction is lower due to the combination of fundamental and harmonic components. After peak intensity, the emission is dominated again by the fundamental component that decays until the end of a burst with lesser polarization fraction than earlier. We argue that the fundamental radiation that decays over time after peak burst intensity is strongly scattered. This pattern of fundamental, fundamental and harmonic, and then fundamental emission with time at each frequency is consistent with the interpretations of Dulk, Suzuki, and Sheridan (Astron. Astrophys.130, 39, 1984), Robinson, Cairns, and Willes (Astrophys. J.422, 870, 1994), and Robinson and Cairns (Solar Phys.181, 363, 1998). We propose that scattering effects can be a viable reason for low polarization fractions in type III events. Finally, we investigate the variations of the decay time ($t_{d}$) for three events with frequency ($f$), finding that $t_{d} \propto f^{-2.0\pm 0.1}$ and decreases more rapidly with increasing $f$ compared with previous lower-frequency observations ($t_{d} \propto f^{-1.1\pm 0.1}$). This is interpreted in terms of radial variations of the turbulence properties.

The effects of transcranial static magnetic fields stimulation over the supplementary motor area on anticipatory postural adjustments

We investigated the influence of transcranial static magnetic field stimulation (tSMS) over the supplementary motor area (SMA) on anticipatory postural adjustments (APAs), in which the activation of the postural muscles of the legs and trunk that control standing posture precedes the activation of the prime mover muscles during rapid shoulder flexion movement. Eighteen subjects performed a self-paced rapid shoulder flexion task before, during, and after tSMS. Electromyogram (EMG) activity was recorded from the deltoid anterior (AD) as the prime mover muscle and the biceps femoris (BF) as the postural muscle during the task. The EMG latency difference (ΔEMG onset) between the two muscles was calculated by subtracting the EMG burst onset of the BF from that of the AD. The ΔEMG onset was significantly shortened, but center-of-pressure parameters were not affected after tSMS stimulation. These findings suggest that tSMS applied over the SMA could inhibitively modulate APAs function.

Rate dependent transition to thermoacoustic instability via intermittency in a turbulent afterburner

Experiments were conducted to study the rate dependent transition to thermoacoustic instability in a turbulent afterburner rig. The afterburner rig contains v-gutters as flame stabilizers and simulates elevated inlet gas temperature using a preheater. Under quasi-static increase in flow Reynolds number of the afterburner, screech is not observed; on the contrary, screech onsets when the Reynolds number is increased at a higher rate. Such a phenomenon is known as rate induced tipping or R-tipping. When the Reynolds number is increased at a lower rate, screech appears as a few bursts of high-amplitude periodic oscillations amidst low-amplitude aperiodic oscillations, a state known as intermittency. As the rate of change of Reynolds number is increased, more bursts appear and with further increase in the rate, the proportion of periodic oscillations of the bursts increases in the time series of pressure fluctuations, approaching a state of limit-cycle oscillations. We show for the first time, a rate-dependent transition to thermoacoustic instability in a turbulent afterburner happening through intermittency, with respect to increasing the rate of change of Reynolds number. The onset of burst occurs earlier, i.e. bursts occurring at a lower Reynolds number as the rate of change of Reynolds number is increased. The amplitude of bursts during intermittency is higher than that of the limit cycle oscillations. The rate dependent transition to screech through intermittency is analyzed by studying the variation of probability density function (PDF) of the amplitude of pressure, variation of the amplitude of bursts, variation of the number of bursts of periodic oscillations, and the inlet conditions corresponding to the onset of bursts, with respect to different rates of change of Reynolds number. Rate dependent transition observed in the model afterburner suggests that combustion system of a gas turbine engine should be subjected to different engine throttling rates to define the thermoacoustic stability map.

Radio frequency emissions driven by energetic ions from neutral beam in KSTAR low confinement mode plasma

The tangential neutral beam injection in KSTAR low confinement mode plasma is rapidly accompanied by the electromagnetic emissions in radio frequency (RF) range (0.1–1 GHz). The RF emission is initially onset within 1 ms from the beam injection, at discrete frequencies with steadily increasing intensity. The frequency spacing for these discrete emission lines corresponds to the deuteron cyclotron frequency, at a location midway between the magnetic axis and the edge. Further, the observed discrete frequencies lie in the lower hybrid frequency (fLH) range in a broad region on the low field side (LFS). As the initial RF emission becomes saturated, there is another onset of intense RF bursts occurring at discrete frequencies, broadening the emission frequency range further, either at higher or lower frequencies. In some cases, the time interval of the intense RF bursts at the dominant frequency is comparable with the toroidal rotation period at the radial location where fLH ∼ dominant frequency. The rapid rise and saturation of RF emission intensity in a broad frequency range indicate that a small population of fast ions is sufficient for the growth of energetic particle driven instabilities on the LFS. The multiple onsets in RF emission and the intense RF burst repetition frequency comparable with toroidal rotation frequency indicate the possibility that reorganization in the anisotropic fast ion population results in localized growth of the above instabilities. A gradual decay of RF emission intensity over few tens of milliseconds indicate that enhanced population of fast ions has damping effect on these instabilities.

The Cumulative Effect of Transient Synchrony States on Motor Performance in Parkinson's Disease

Bursts of beta frequency band activity in the basal ganglia of patients with Parkinson's disease (PD) are associated with impaired motor performance. Here we test in human adults whether small variations in the timing of movement relative to beta bursts have a critical effect on movement velocity and whether the cumulative effects of multiple beta bursts, both locally and across networks, matter. We recorded local field potentials from the subthalamic nucleus (STN) in 15 PD patients of both genders OFF-medication, during temporary lead externalization after deep brain stimulation surgery. Beta bursts were defined as periods exceeding the 75th percentile amplitude threshold. Subjects performed a visual cued joystick reaching task, with the visual cue being triggered in real time with different temporal relationships to bursts of STN beta activity. The velocity of actions made in response to cues prospectively triggered by STN beta bursts was slower than when responses were not time-locked to recent beta bursts. Importantly, slow movements were those that followed multiple bursts close to each other within a trial. In contrast, small differences in the delay between the last burst and movement onset had no significant impact on velocity. Moreover, when the overlap of bursts between the two STN was high, slowing was more pronounced. Our findings suggest that the cumulative, but recent, history of beta bursting, both locally and across basal ganglia networks, may impact on motor performance.SIGNIFICANCE STATEMENT Bursts of beta frequency band activity in the basal ganglia are associated with slowing of voluntary movement in patients with Parkinson's disease. We show that slow movements are those that follow multiple bursts close to each other and bursts that are coupled across regions. These results suggest that the cumulative, but recent, history of beta bursting, both locally and across basal ganglia networks, impacts on motor performance in this condition. The manipulation of burst dynamics may be a means of selectively improving motor impairment.

Measurement of phagocyte activity in heterotherms

The heterotherm immune system undergoes significant variation in response to life cycle periodicity and torpor. As heterothermic bats are important reservoirs of zoonotic agents and modulation of immune activity can affect host-pathogen interactions, this work aimed at developing a suitable method for assessing heterotherm phagocyte activity. Chemiluminescence measurements were evaluated by mathematical and mechanistic approaches, both of which yielded comparable results in time-related parameters of phagocyte activity. Using a mathematical method, however, we developed a model that can be applied to particular specimens. The proposed equation offers a simple and reliable tool for comparing phagocyte activity, the values of which can be used for further analysis. While time-related parameters of bat phagocyte activity varied with measurement temperature, with the onset of respiratory burst at 38 °C being quicker than at 25 °C, quantitative values ​​of phagocyte activity were not influenced by measurement temperature. Further, homeotherm phagocyte activity parameters were more variable at 25 °C. Considering there was no influence of measurement temperature on the total volume of heterotherm phagocyte activity, we suggest that parameters measured at 25 °C are more representative of the immune status adapted to physiological extremes at low body temperatures.

Auditory Perceptual History Is Propagated through Alpha Oscillations.

SummaryPerception is a proactive, “predictive” process, in which the brain relies, at least in part, on accumulated experience to make best guesses about the world to test against sensory data, updating the guesses as new experience is acquired. Using novel behavioral methods, the present study demonstrates the role of alpha rhythms in communicating past perceptual experience. Participants were required to discriminate the ear of origin of brief sinusoidal tones that were presented monaurally at random times within a burst of uncorrelated dichotic white noise masks. Performance was not constant but varied with delay after noise onset in an oscillatory manner at about 9 Hz (alpha rhythm). Importantly, oscillations occurred only for trials preceded by a target tone to the same ear, either on the previous trial or two trials back. These results suggest that communication of perceptual history generates neural oscillations within specific perceptual circuits, strongly implicating behavioral oscillations in predictive perception and with formation of working memory.

Inhaling Hydrogen Ameliorates Early Postresuscitation EEG Characteristics in an Asphyxial Cardiac Arrest Rat Model.

Background Electroencephalography (EEG) is commonly used to assess the neurological prognosis of comatose patients after cardiac arrest (CA). However, the early prognostic accuracy of EEG may be affected by postresuscitation interventions. Recent animal studies found that hydrogen inhalation after CA greatly improved neurological outcomes by selectively neutralizing highly reactive oxidants, but the effect of hydrogen inhalation on EEG recovery and its prognostication value are still unclear. The present study investigated the effects of hydrogen inhalation on early postresuscitation EEG characteristics in an asphyxial CA rat model. MethodsCardiopulmonary resuscitation was initiated after 5 min of untreated CA in 40 adult female Sprague-Dawley rats. Animals were randomized for ventilation with 98% oxygen plus 2% hydrogen (H2) or 98% oxygen plus 2% nitrogen (Ctrl) under normothermia for 1 h. EEG characteristics were continuously recorded for 4 h, and the relationships between quantitative EEG characteristics and 96 h neurological outcomes were investigated. ResultsNo differences in baseline and resuscitation data were observed between groups, but the survival rate was significantly higher in the H2 group than in the Ctrl group (90% vs. 40%, P < 0.01). Compared to the Ctrl group, the H2 group showed a shorter burst onset time (21.85 [20.00–23.38] vs. 25.70 [22.48–30.05], P < 0.01) and time to normal trace (169.83 [161.63–208.55] vs. 208.39 [186.29–248.80], P < 0.01). Additionally, the burst suppression ratio (0.66 ± 0.09 vs. 0.52 ± 0.17, P < 0.01) and weighted‐permutation entropy (0.47 ± 0.16 vs. 0.34 ± 0.13, P < 0.01) were markedly higher in the H2 group. The areas under the receiver operating characteristic curves for the 4 EEG characteristics in predicting survival were 0.82, 0.84, 0.88, and 0.83, respectively. ConclusionsIn this asphyxial CA rat model, the improved postresuscitation EEG characteristics for animals treated with hydrogen are correlated with the better 96 h neurological outcome and predicted survival.

Cluster burst synchronization in a scale-free network of inhibitory bursting neurons.

We consider a scale-free network of inhibitory Hindmarsh-Rose (HR) bursting neurons, and make a computational study on coupling-induced cluster burst synchronization by varying the average coupling strength . For sufficiently small , non-cluster desynchronized states exist. However, when passing a critical point , the whole population is segregated into 3 clusters via a constructive role of synaptic inhibition to stimulate dynamical clustering between individual burstings, and thus 3-cluster desynchronized states appear. As is further increased and passes a lower threshold , a transition to 3-cluster burst synchronization occurs due to another constructive role of synaptic inhibition to favor population synchronization. In this case, HR neurons in each cluster make burstings every 3rd cycle of the instantaneous burst rate of the whole population, and exhibit burst synchronization. However, as passes an intermediate threshold , HR neurons fire burstings intermittently at a 4th cycle of via burst skipping rather than at its 3rd cycle, and hence they begin to make intermittent hoppings between the 3 clusters. Due to such intermittent intercluster hoppings via burst skippings, the 3 clusters become broken up (i.e., the 3 clusters are integrated into a single one). However, in spite of such break-up (i.e., disappearance) of the 3-cluster states, (non-cluster) burst synchronization persists in the whole population, which is well visualized in the raster plot of burst onset times where bursting stripes (composed of burst onset times and indicating burst synchronization) appear successively. With further increase in , intercluster hoppings are intensified, and bursting stripes also become dispersed more and more due to a destructive role of synaptic inhibition to spoil the burst synchronization. Eventually, when passing a higher threshold a transition to desynchronization occurs via complete overlap between the bursting stripes. Finally, we also investigate the effects of stochastic noise on both 3-cluster burst synchronization and intercluster hoppings.

Discovery of millihertz quasi-periodic oscillations in the X-ray binary EXO 0748−676

Abstract We report the discovery of millihertz quasi-periodic oscillations (mHz QPOs) from the bursting, high-inclination atoll neutron star low-mass X-ray binary (NS LMXB) EXO 0748−676 with the Rossi X-ray Time Explorer (RXTE). This class of QPO, originally discovered in three NS LMXBs, has been interpreted as a consequence of a special mode of nuclear burning on the NS surface. Using all the RXTE archival observations of the source, we detected significant (&amp;gt;3σ) mHz QPOs in 11 observations. The frequency of the oscillations was between ∼5 and ∼13 mHz. We also found a decrease of the QPO frequency with time in two occasions; in one of these the oscillations disappeared with the onset of an X-ray burst, similar to what was reported in other sources. Our analysis of the X-ray colours revealed that EXO 0748−676 was in a soft spectral state when it exhibited the QPOs. This makes EXO 0748−676 the sixth source with mHz oscillations associated with marginally stable burning, and the second one that shows a systematic frequency drift. Our results suggest that the mechanism that produces the drift might always be present if the mHz QPOs are observed in the so-called intermediate state.

Characterization of strain bursts in high density polyethylene by means of a novel nano creep test

Recent nanoindentation experiments have shown that in semi-crystalline polymers, strain bursts emerge during creep experiments. A shortcome of nanoindentation is that due to the inhomogeneous stress field, a critical stress for the onset of strain bursts cannot be determined, and the resolution of the method seems to be limited. Since the strain bursts in polymers are in the nm range, an extremely high resolution in deformation measurement is necessary. Such a resolution is provided by modern solid state rheometers having a resolution < 10−6 rad. With such a facility, in this work single strain bursts in PE-HD have been investigated in creep mode at stresses as low as < 0.5 MPa. As the strain bursts only occur rarely, hundreds of creep experiments were carried out and evaluated statistically. Through variation of the temperature and the stress, the activation energy for the strain bursts was determined as 0.65 (±0.06) eV. In addition, negative strain bursts (contrary to the direction of deformation) with an activation energy of 0.49 (±0.08) eV and post-oscillations after strain bursts could be observed for the first time. In summary the new method represents a powerful tool for a quantitative characterization of strain bursts and gives a new insight to dislocation kinetics in semi-crystalline polymers.

How can no change in an auditory stimulus generate an N2b-P3a?

The purpose of this study was to investigate the occurrence of an endogenously-evoked no-go N2b. Previous literature focused on the N2b being evoked by exogenous auditory stimuli. In this study, no-go stimuli were the absence of a gap in a 1000-ms noise burst (i.e., no-gap trials). ERPs were measured from 35 participants while performing a gap-detection task and passively listening to the same stimuli. Participants were asked to press a button when they heard a gap in the noise burst (go trials) and to withhold their button press when they did not perceive a gap in the noise burst (no-go trials). The current study’s gap-detection task had predictable timing (gaps always occurred at 500 ms after noise burst onset) and high probability of gaps occurring (10:1); therefore, participants built up an expectancy that gaps would occur on most trials at 500 ms. For no-gap trials, this meant that a participant’s expectancy was violated and thus a N2b-P3a response was generated. We found that all participants had N2b-P3a responses to no-gap trials. Overall, this study demonstrated that the no-go N2b-P3a response can be evoked by an endogenous signal in the form of the omission of an expected gap in noise.

Relativistic fireball reprise: radio suppression at the onset of short magnetar bursts

There is growing evidence that a clear distinction between magnetars and radio pulsars may not exist, implying the population of neutron stars that exhibit both radio pulsations and bursting activities could be potentially large. In this situation, new insights into the burst mechanism could be gained by combining the temporal behavior of radio pulsations. We present a general model for radio suppression by relativistic $e^{\pm}$ plasma outflows at the onset of magnetar flares. A sudden ejection of magnetic energy into the magnetosphere would generate a fireball plasma, which is promptly driven to expand at relativistic speed. This would make the plasma cutoff frequency significantly higher than the rest frame radio frequency, resulting in the suppression of radio waves. We analytically show that any GHz radio emission arising from the magnetosphere is suppressed for $\sim100\ {\rm s}$, depending on the total fireball energy. On the other hand, thermal radiation is expected from the hot spot(s) on the stellar surface created by an inflow of dense plasma, which could be the origin of short bursts. Since our hypothesis predicts radio suppression in coincidence with short bursts, this could be an indirect method to constrain the occurrence rate of short bursts at the faint end that remain undetected by X-ray detectors. Furthermore, ultra-fast gamma-ray flashes from the fireball photosphere is also expected as a smoking gun, although the onboard detection is challenging due to its extremely short duration $\sim\mu$s. Finally, our model is applied to the radio pulsar with magnetar-like activities, PSR J1119-6127 in light of recent observations. Implications for fast radio bursts and the possibility of plasma lensing are also discussed.

Triggered superradiance and fast radio bursts

In this paper we develop a model for fast radio bursts (FRBs) based on triggered superradiance (SR) and apply it to previously published data of FRB 110220 and FRB 121102. We show how a young pulsar located at ~100 pc or more from an SR/FRB system could initiate the onset of a powerful burst of radiation detectable over cosmological distances. Our models using the OH$^2\Pi_{3/2}$ $\left(J=3/2\right)$ 1612 MHz and $^2\Pi_{3/2}$ $\left(J=5/2\right)$ 6030 MHz spectral lines match the light curves well and suggest the entanglement of more than $10^{30}$ initially inverted molecules over lengths of approximately 300 au for a single SR sample. SR also accounts for the observed temporal narrowing of FRB pulses with increasing frequency for FRB 121102, and predicts a scaling of the FRB spectral bandwidth with the frequency of observation, which we found to be consistent with the existing data.

Delayed burst of a gel balloon

When inflating a rubber balloon, it is commonly concluded that a sudden expansion in balloon size (i.e., the burst) occurs once the inner pressure reaches a critical threshold, the instantaneous burst pressure. Such burst phenomena are usually attributed to the snap-through instability. In this work, we demonstrate that when a hydrogel balloon is subject to a subcritical pressure lower than the instantaneous burst pressure, the hydrogel balloon may remain stable for a span of time, and then burst suddenly. We refer to such burst phenomena as the delayed burst of the gel balloon. When subject to such a subcritical inner pressure, a hydrogel balloon slowly and continuously absorbs solvent and swells. We find the instantaneous burst pressure of the hydrogel balloon to be a decreasing function of swelling ratio. The criterion for the onset of burst is that the swelling-related instantaneous burst pressure drops to the applied inner pressure. The delayed burst can, therefore, be attributed to the time needed for the hydrogel swelling to reduce the instantaneous burst pressure to the level of applied pressure. We further delineate a map indicating three distinct deformation modes of gel balloons, i.e., instantaneous burst, delayed burst, and steady deformation without burst (safe mode), in the parameter space of applied pressure and mechanical properties of the hydrogel. The delayed burst of a hydrogel balloon is counterintuitive and a crucial aspect in developing hydrogel-shell-based soft actuators and soft machines. The research findings may shed light on the understanding of the complex failure mechanisms of hydrogel actuators and also facilitate the design of hydrogel-based tissue delivery capsules.