Rare Bursts Research Articles

GRB 211211A-like Events and How Gravitational Waves May Tell Their Origins

GRB 211211A is a rare burst with a genuinely long duration, yet its prominent kilonova association provides compelling evidence that this peculiar burst was the result of a compact binary merger. However, the exact nature of the merging objects, whether they were neutron star pairs, neutron star–black hole systems, or neutron star–white dwarf systems, remains unsettled. This Letter delves into the rarity of this event and the possibility of using current and next-generation gravitational wave detectors to distinguish between the various types of binary systems. Our research reveals an event rate density of for GRB 211211A-like gamma-ray bursts (GRBs), which, assuming GRB 211211A is the only example of such a burst, is significantly smaller than that of typical long- and short-GRB populations. We further calculated that if the origin of GRB 211211A is a result of a neutron star–black hole merger, it would be detectable with a significant signal-to-noise ratio (S/N), given the LIGO-Virgo-KAGRA designed sensitivity. On the other hand, a neutron star–white dwarf binary would also produce a considerable S/N during the inspiral phase at decihertz and is detectable by next-generation spaceborne detectors DECIGO and the Big Bang Observer. However, to detect this type of system with millihertz spaceborne detectors like LISA, Taiji, and TianQin, the event must be very close, approximately 3 Mpc in distance or smaller.

The ultra-long GRB 220627A at z = 3.08

Context. GRB 220627A is a rare burst with two distinct γ-ray emission episodes separated by almost 1000 s that triggered the Fermi Gamma-ray Burst Monitor twice. High-energy GeV emission was detected by the Fermi Large Area Telescope coincident with the first emission episode but not the second. The discovery of the optical afterglow with MeerLICHT led to MUSE observations which secured the burst redshift to z = 3.08, making this the most distant ultra-long gamma-ray burst (GRB) detected to date. Aims. The progenitors of some ultra-long GRBs have been suggested in the literature to be different to those of normal long GRBs. Our aim is to determine whether the afterglow and host properties of GRB 220627A agree with this interpretation. Methods. We performed empirical and theoretical modelling of the afterglow data within the external forward shock framework, and determined the metallicity of the GRB environment through modelling the absorption lines in the MUSE spectrum. Results. Our optical data show evidence for a jet break in the light curve at ∼1.2 days, while our theoretical modelling shows a preference for a homogeneous circumburst medium. Our forward shock parameters are typical for the wider GRB population, and we find that the environment of the burst is characterised by a sub-solar metallicity. Conclusions. Our observations and modelling of GRB 220627A do not suggest that a different progenitor compared to the progenitor of normal long GRBs is required. We find that more observations of ultra-long GRBs are needed to determine if they form a separate population with distinct prompt and afterglow features, and possibly distinct progenitors.

How Fast or How Many? Sources of Intermittent Sediment Transport

AbstractNear the threshold of grain motion, sediment transport is “on‐off” intermittent, characterized by large but rare bursts separated by long periods of low transport. Without models that can account for the effects of intermittency, measurements of average sediment flux can be in error by up to an order of magnitude. Despite its known presence and impact, it is not clear whether on‐off intermittency arises from the grain activity (the number of moving grains) or grain velocities, which together determine the sediment flux. We use laboratory flume experiments to show that the on‐off intermittency has its origins in the velocity distributions of grains that move by rolling along the bed, whereas grain activity is not on‐off intermittent. Incorporating the types of intermittency we identify into stochastic models of sediment transport could yield improved predictions of sediment flux, including physically based estimates of the uncertainty in time‐averaged sediment flux.

Rapid acquisition of microorganisms and microbial genes can help explain punctuated evolution

The punctuated mode of evolution posits that evolution occurs in rare bursts of rapid evolutionary change followed by long periods of genetic stability (stasis). The accepted cause for the rapid changes in punctuated evolution is special ecological circumstances – selection forces brought about by changes in the environment. This article presents a complementary explanation for punctuated evolution by the rapid formation of genetic variants in animals and plants by the acquisition of microorganisms from the environment into microbiomes and microbial genes into host genomes by horizontal gene transfer. Several examples of major evolutionary events driven by microorganisms are discussed, including the formation of the first eukaryotic cell, the ability of some animals to digest cellulose and other plant cell-wall complex polysaccharides, dynamics of root system architecture, and the formation of placental mammals. These changes by cooperation were quantum leaps in the evolutionary development of complex bilolgical systems and can contribute to an understanding of the mechanisms underlying punctuated evolution.

Human Midbrain Auditory Evoked Potentials Do Not Differ Between Bursts and Suppressions of Cortex Activity in Propofol Anesthesia: Case Report

Propofol, the most widely administered anesthetic agent, is used for sedation and general anesthesia. During general anesthesia it can induce bursts and suppressions of cortex activity, which exact mechanism of generation has not been identified yet. The aim of study was to investigate the difference between midbrain auditory evoked potentials recorded during bursts and suppressions of cortex activity. These potentials were registered from the drainage-electrode implanted in the cerebral aqueduct of an adult patient with an obstructive hydrocephalus who had undergone pineal region tumor removal through anterior interhemispheric transcallosal approach. The cortex activity was divided into rare bursts of alpha activity (total length of 9 seconds) and prolonged suppressions (total length of 104 seconds). Midbrain auditory evoked potentials included long latency peaks with no statistically significant difference in their amplitudes and latencies between bursts and suppressions of cortex activity. The results suggest that human midbrain auditory evoked potentials do not differ between bursts and suppressions of cortex activity in propofol anesthesia. Therefore, for clear midbrain auditory evoked potentials cognitive but not the total electrical activity of the cortex should be suppressed.

Dix-sept ans by Éric Fottorino

Reviewed by: Dix-sept ans by Éric Fottorino William Cloonan Fottorino, Éric. Dix-sept ans. Gallimard, 2018. ISBN 978-2-07-014112-8. Pp. 263. If you rearrange the letters in the name Éric, you can create crié (169), a word which effectively captures the tone of this novel. Lina was seventeen years old when she [End Page 232] gave birth to an illegitimate child, Éric, who narrates the story. At the time of her son's birth, she was so naïve that there are hints she might not even have known how children are produced. The news of her pregnancy horrifies Lina's pious mother, and the discovery that the father is Jewish sends the older woman over the top. Her anger is further fueled by a bigoted curé and the heartless nuns who deliver the baby. The plan is to give the unwanted child away, but in a rare burst of anger, Lina insists on keeping him. Their early years together are trying financially, but mother and child are extremely close. Eventually, however, Éric finds it increasingly difficult to express his feelings for her, and when the story opens, the middle-aged narrator is emotionally stymied before the woman he calls Lina. Only in the final sections, during a car ride from Bordeaux to Nice, do Éric's feelings begin to break free, and in the final scene, where Lina lies in a coma, the son takes the mother's hand and allows himself to begin telling her how much he loves her. Dix-sept ans really has two parts. The first focuses on Éric's complicated and confounding feelings, which flirt with nombrilisme. It is never clear what precipitated his distancing himself from Lina. His attempts at explanation lack coherence, as do his occasional epiphanies. When a woman explains to him that he is Jewish because,"Être juif, c'est avoir des enfants juifs" (151), this appears to be a revelation for Éric, if not for anyone else. The second, somewhat more interesting part of the novel concerns Lina, her family, and her social milieu. Despite coming from a hardscrabble background, Lina lives primarily in a dreamlike world. She can occasionally express, but never sustain anger. Her mother is certainly a religious bigot, but during the Occupation her then-husband and she sheltered a Jewish family. Lina's brother, Paul, is a taciturn, rather unstable figure. Yet during Éric's early years he is a worthy surrogate father. Later, Paul accepts his identity as a gay man, finds a loving partner and a talent for horticulture. Unfortunately, the relationship and the business flounder, and Paul takes his life. Lina's beloved father left his family and moved to Madagascar where he fell in love with une Malgache. In order to marry her, the father had to renounce seeing his daughter ever again. Lina's story is more compelling than Éric's, and her family's complexity of greater interest than the narrator's ceaseless soul-searching. While Dix-sept ans is finally a rather average novel, it contains the potential for a quite good one. William Cloonan Florida State University, emeritus Copyright © 2019 American Association of Teachers of French

Stochastic gravitational wave background from smoothed cosmic string loops

We do a complete calculation of the stochastic gravitational wave background to be expected from cosmic strings. We start from a population of string loops taken from simulations, smooth these by Lorentzian convolution as a model of gravitational back reaction, calculate the average spectrum of gravitational waves emitted by the string population at any given time, and propagate it through a standard model cosmology to find the stochastic background today. We take into account all known effects, including changes in the number of cosmological relativistic degrees of freedom at early times and the possibility that some energy is in rare bursts that we might never have observed.

Phenotypic evolution: the ongoing synthesis (American Society of Naturalists address).

I explore the proposition that evolutionary biology is currently in the midst of its greatest period of synthesis. This period, which I call the Ongoing Synthesis, began in 1963 and continues at the present time. I use analysis of citations, conduct, and content to compare the Ongoing Synthesis to widely recognized periods of synthesis in the nineteenth and twentieth centuries. To compare content, I focus on phenotypic evolution and compare current efforts with George Gaylord Simpson's struggle to understand evolution in deep geological time. The essence of current effort is captured by the question, What is the best model for phenotypic evolution? Although many investigators are actively engaged in answering this question, I single out two examples of my own collaborative work for emphasis here. These two studies share three important characteristics: diagnosis of evolutionary pattern using massive data sets, validation of model parameter values using compilations of estimates (e.g., heritability, stabilizing selection, distance to an intermediate optimum), and identification of evolutionary process using alternative models of stochastic evolution. Our primary findings (discovery of the blunderbuss pattern and the result that rare bursts of evolution carry lineages out of established adaptive zones) compare favorably with important insights from the Modern Synthesis.

Bridging the gap: Bargaining with interdependent values

We study dynamic bargaining with asymmetric information and interdependent values. We base our analysis on the equilibria characterized by Deneckere and Liang (2006) for the gap case. We show that as the gap between the cost and value of the weakest type shrinks to zero, the continuous time limit of equilibria changes dramatically from rare bursts of trade with long periods of inactivity to smooth screening over time. In the double limit prices are independent of the shape of the distribution of values. When the uninformed agentʼs ability to commit to prices disappears so do her rents, yet trade still exhibits delay.

Transient Periodicity in a Morris-Lecar Neural System

The dynamical complexity of a system of ordinary differential equations (ODEs) modeling the dynamics of a neuron that interacts with other neurons through on-off excitatory and inhibitory synapses in a neural system was investigated in detail. The model used Morris-Lecar (ML) equations with an additional autonomous variable representing the input from interaction of excitatory neuronal cells with local interneurons. Numerical simulations yielded a rich repertoire of dynamical behavior associated with this three-dimensional system, which included periodic, chaotic oscillation and rare bursts of episodic periodicity called the transient periodicity.

Complex mixed-mode oscillations in a Bonhoeffer–van der Pol oscillator under weak periodic perturbation

In this paper, we elucidate the extremely complicated bifurcation structure of a weakly driven relaxation oscillator by focusing on chaos, and notably, on complex mixed-mode oscillations (MMOs) generated in a simple dynamical model. Our model uses the Bonhoeffer–van der Pol (BVP) oscillator subjected to a weak periodic perturbation near a subcritical Andronov–Hopf bifurcation (AHB). The mechanisms underlying the chaotic dynamics can be explained using an approximate one-dimensional map. The MMOs that appear in this forced dynamical model may be more sophisticated than those appearing in three-variable slow–fast autonomous dynamics because the approximate one-dimensional mapping of the dynamics used herein is a circle map, whereas the one-dimensional first-return map that is derived from the three-variable slow–fast autonomous dynamics is usually a unimodal map. In this study, we generate novel bifurcations such as an MMO-incrementing bifurcation (MMOIB) and intermittently chaotic MMOs. MMOIBs trigger an MMO sequence that, upon varying a parameter, is followed by another type of MMO sequence. By constructing a two-parameter bifurcation diagram, we confirmed that MMOIBs occur successively. According to our numerical results, MMOIBs are often observed between two neighboring MMOs. Numerically, MMOIBs may occur as many times as desired. We also derive the universal constant of the associated successive MMOIBs. The existence of the universal constant suggests that MMOIBs could occur infinitely many times. Furthermore, intermittently chaotic MMOs appear in this dynamical circuit. The intermittently chaotic MMOs relate to a type of intermittent chaos that resembles MMOs at first glance, but includes rare bursts over a long time interval. Complex intermittently chaotic MMOs of various types are observed, and we clarify that the intermittently chaotic MMOs are generated by crisis-induced intermittency.

The million-year wait for macroevolutionary bursts.

We lack a comprehensive understanding of evolutionary pattern and process because short-term and long-term data have rarely been combined into a single analytical framework. Here we test alternative models of phenotypic evolution using a dataset of unprecedented size and temporal span (over 8,000 data points). The data are body-size measurements taken from historical studies, the fossil record, and among-species comparative data representing mammals, squamates, and birds. By analyzing this large dataset, we identify stochastic models that can explain evolutionary patterns on both short and long timescales and reveal a remarkably consistent pattern in the timing of divergence across taxonomic groups. Even though rapid, short-term evolution often occurs in intervals shorter than 1 Myr, the changes are constrained and do not accumulate over time. Over longer intervals (1-360 Myr), this pattern of bounded evolution yields to a pattern of increasing divergence with time. The best-fitting model to explain this pattern is a model that combines rare but substantial bursts of phenotypic change with bounded fluctuations on shorter timescales. We suggest that these rare bursts reflect permanent changes in adaptive zones, whereas the short-term fluctuations represent local variations in niche optima due to restricted environmental variation within a stable adaptive zone.

The Impact of Nuclear Architecture on EGFP Diffusion Revealed by Pair Correlation Analysis

The diffusion of molecules within the nucleus is obstructed by the steric constraints imposed by the nuclear environment. The extent to which nuclear architecture directs the diffusive route taken by these molecules is of significant interest. No methods proposed thus far have the capability to measure overall molecular flow in the nucleus of living cells. Here we apply the pair correlation function analysis (pCF) to measure molecular anisotropic diffusion in the interphase and mitotic nucleus of live cells. In the pCF method we cross correlate fluctuations at several distances and locations within the nucleus, enabling us to define migration paths and barriers to diffusion. We use monomeric EGFP as a prototypical inert molecule and measure its flow in and between the different nuclear environments. For the interphase nucleus we observe two disconnect molecular flows associated with high and low DNA density, which cause the chromatin to behave as a channeled network. Upon more detailed analysis in time, rare bursts of EGFP molecules are detected crossing the channel barriers. The intermittent nature of this transit suggests an intrinsic localized change in chromatin structure which periodically turns on and off. For the mitotic nucleus we observe the chromosomes to impart a markedly different mechanism toward regulation of the equivalent transit. That is, we found EGFP flow between the different nuclear environments of a mitotic nucleus to be continuous and delayed. The continuity of obstruction in time suggests the chromosomes to regulate diffusion by acting as a physical barrier. These two distinct diffusive routes were concomitantly observed in the C. elegans germ line. This is the first in vivo demonstration of cell cycle dependent diffusion of an inert molecule as regulated by nuclear architecture with high spatial and temporal resolution.

Increased bursting in layer 2/3 neurones of awake neocortex

Increased bursting in layer 2/3 neurones of awake neocortex

Bracing for a solor superstorm

The article discusses solar superstorms, rare bursts of intense solar activity which hit the earth with a blast of solar particles. One recorded in 1859 created intense aurora light effects as far south as the Caribbean, and wreaked havoc with magnetic compasses and electric telegraph systems. The importance of guarding satellites and the power grid against major damage from such an event is emphasized. INSETS: Impact of a Coronal Mass Ejection;The 1859 Superstorm;IT'S RAINING PROTONS.

Martian dunes form in rare bursts

Martian dunes form in rare bursts

Interaction Intimacy Affects Structure and Coevolutionary Dynamics in Mutualistic Networks

The structure of mutualistic networks provides clues to processes shaping biodiversity [1-10]. Among them, interaction intimacy, the degree of biological association between partners, leads to differences in specialization patterns [4, 11] and might affect network organization [12]. Here, we investigated potential consequences of interaction intimacy for the structure and coevolution of mutualistic networks. From observed processes of selection on mutualistic interactions, it is expected that symbiotic interactions (high-interaction intimacy) will form species-poor networks characterized by compartmentalization [12, 13], whereas nonsymbiotic interactions (low intimacy) will lead to species-rich, nested networks in which there is a core of generalists and specialists often interact with generalists [3, 5, 7, 12, 14]. We demonstrated an association between interaction intimacy and structure in 19 ant-plant mutualistic networks. Through numerical simulations, we found that network structure of different forms of mutualism affects evolutionary change in distinct ways. Change in one species affects primarily one mutualistic partner in symbiotic interactions but might affect multiple partners in nonsymbiotic interactions. We hypothesize that coevolution in symbiotic interactions is characterized by frequent reciprocal changes between few partners, but coevolution in nonsymbiotic networks might show rare bursts of changes in which many species respond to evolutionary changes in a single species.

Field Deployment of Prototype Antenna Tiles for the Mileura Widefield Array Low Frequency Demonstrator

Experiments were performed with prototype antenna tiles for the Mileura Widefield Array Low Frequency Demonstrator (MWA LFD) to better understand the wide-field, wide-band properties of their design and to characterize the radio-frequency interference (RFI) between 80 and 300 MHz at the site in Western Australia. Observations acquired during the 6 month deployment confirmed the predicted sensitivity of the antennas, sky-noise-dominated systemtemperatures,andphase-coherentinterferometricmeasurements.Theradiospectrumisremarkablyfreeofstrong terrestrial signals, with the exception of two narrow frequency bands allocated to satellite downlinks, and rare bursts duetoground-based transmissionsbeingscatteredfrom aircraft andmeteortrails. Resultsindicatethepotential ofthe MWA LFD to make significant achievements in its three key science objectives: epoch of reionization science, heliospheric science, and radio transient detection.

무선 센서 네트워크에서 전송 효율과 에너지 소비에 대한 블록 FEC 심볼 크기 영향 분석

본 논문에서는 저속의 무선 센서 네트워크(WSN: Wireless Sensor Network)에서 블록 FEC(Forward Error Correction) 알고리즘의 심볼 크기의 변화에 따른 802.11 MAC 프로토콜의 전송 효율과 전송 에너지를 해석적으로 분석한다. 블록 FEC 알고리즘은 심볼(symbol) 단위로 오류를 복원하므로, 주어진 무선 센서 채널에서 같은 FEC 체크 비트(check bit) 량을 사용하더라도 블록 FEC 알고리즘의 오류 패킷 복원률은 블록 FEC 심볼 크기에 의존적이다. 즉, 같은 양의 FEC 체크 비트를 사용하는 경우에, 연속된 군집 오류 길이는 작으면서 군집 오류가 자주 발생하는 채널에서는 작은 FEC 심볼이, 이에 반해 군집 오류의 길이는 크고 군집 오류 개수가 작은 군집적 분포를 보이는 채널에서 큰 FEC 심볼이 효율적이다. 심볼 크기의 영향을 평가하기 위해서 본 논문에서는 센서 노드 TIP50CM을 사용하는 WSN에서 수집한 패킷 트레이스를 기반으로 WSN 채널을 Gilbert 모델로 모델링하고, 심볼 크기가 다른 RS(Reed-Solomon) 코드를 생성하고 해석하기 위한 에너지를 측정하였다. 이러한 모델링된 채널과 각 RS 코드 생성과 해석 에너지를 이용하여 FEC 심볼 크기에 따른 RS FEC 코드를 채택한 802.11 MAC 프로토콜의 전송 효율과 전송 에너지를 계산하였다. 실제 측정 데이터와 해석적으로 계산한 데이터를 결합한 계산에 의하면 비슷한 FEC 체크 비트 량을 사용하더라도 FEC 심볼 크기에 따라 전송 효율은 최대 4.2%, 그리고 소요 에너지는 최대 35%의 차이가 발생한다. This paper analytically evaluates the FEC(Forward Error Correction) symbol size's effect on the performance and energy consumption of 802.11 protocol with the block FEC algorithm over WSN(Wireless Sensor Network). Since the basic recovery unit of block FEC algorithms is symbols not bits, the FEC symbol size affects the packet correction rate even with the same amount of FEC check bits over a given WSN channel. Precisely, when the same amount of FEC check bits are allocated, the small-size symbols are effective over channels with frequent short bursts of propagation errors while the large ones are good at remedying the long rare bursts. To estimate the effect of the FEC symbol site, the paper at first models the WSN channel with Gilbert model based on real packet traces collected over TIP50CM sensor nodes and measures the energy consumed for encoding and decoding the RS (Reed-Solomon) code with various symbol sizes. Based on the WSN channel model and each RS code's energy expenditure, it analytically calculates the transmission efficiency and power consumption of 802.11 equipped with RS code. The computational analysis combined with real experimental data shows that the RS symbol size makes a difference of up to 4.2% in the transmission efficiency and 35% in energy consumption even with the same amount of FEC check bits.

Probabilistic kinetic model of slow oxidation of low-density lipoprotein: I. Theory

The microscopic probabilistic model has been introduced to explain the kinetics of very slow oxidation of low-density lipoprotein (LDL) from human plasma. The LDL oxidation, carried out in very unfavorable conditions, is assumed to be initiated by the traces of the transition-metal ions associated with the lipoprotein. The substrates for the metal-ion attack are α-tocopherol and the pre-formed lipid hydroperoxide. The theory assumes oscillation of the metal ions and α-tocopherol from the oxidized to the reduced states. In this model α-tocopherol acts as a pro-oxidant. The entire oxidation process consists of rare bursts of events in individual LDL particles. The reactions within the particles are treated in terms of probabilities of individual active species to participate in a specified reaction. The circular flow of the radical reactions could be visualized as circular flow of microscopic probabilities. The empirical, macroscopic quantities are quantitatively related with the microscopic probabilities, determined by a set of five adjustable parameters. The differential equations describing the initial radical generation rate and the rates of change of concentration of oxygen, hydroperoxide, co-antioxidant and trapped radicals in an LDL system are numerically solved in a finite difference approach.