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Microwave radiation is an effective method to weaken the strength of hard rock, but this weakening effect is not obvious enough for weak microwave-absorbing rocks. This work focuses on the role of water in amplifying the effect of microwaves on weak microwave-absorbing rocks, by examining the bursting characteristics of the rocks as well as their physical and mechanical properties before blasting. The experimental results show that when subjected to microwave irradiation, and the time taken for this bursting decreases with higher microwave power. In addition, the surface temperature of saturated sandstone gradually rises with increased irradiation power and duration. Under high microwave power, the uniaxial compressive strength (UCS) of heated saturated sandstone notably decreases within the same irradiation duration. When the microwave power is low, the UCS of saturated sandstone remains relatively unchanged over time. The UCS of dry sandstone exhibits no significant alteration under identical irradiation power and duration. In conclusion, sandstone shows no significant change in its physical and mechanical properties during brief exposure to low-power microwave irradiation in its dry state. As water within the sandstone undergoes a phase transition from liquid to gas due to microwave irradiation, the resulting steam pressure causes the sandstone to rupture. [ABSTRACT FROM AUTHOR]

The bursting with long burst duration of the pancreatic β-cells related to the diabetes is helpful to maintain the normal blood glucose concentration. Then, nonlinear dynamics underlying burst duration is an important issue, which is investigated in a theoretical model containing two slow variables (s and z) in the present paper. For the deterministic case, different shapes and sizes of the bursting trajectory show that the slow bursting is modulated by s, z, and s-nullcline in wide ranges, the medium bursting by s and z in medium ranges, and the fast bursting mainly by s in narrow ranges. Through two-parameter bifurcation analysis, the burst of the three bursting patterns terminates at saddle homoclinic orbit (SH) bifurcation curve. For the slow and medium bursting patterns, the latter part of the burst mainly runs along z-direction and closely to the saddle surface. Then, noise can induce the burst to terminate earlier than the SH via passage through the saddle surface, resulting in decreased burst duration. Compared with the drastic decrease for the medium bursting, slow bursting exhibits small reduction, since the large size induces two phases insensitive to noise. One is the latter part of the quiescent state, which runs along the s-nullcline to exhibit extra-stable dynamics, and the other is the former part of the burst, which runs far from the saddle surface. However, the fast bursting mainly runs along s-direction and far from the saddle surface exclusive the SH, then, noise can only induce small changes. Then, the different changing trends of the stochastic slow, medium, and fast bursting patterns are well explained with the different stochastic responses around different bifurcation points or critical phases. The results present dynamical mechanism for the long burst duration which is favor for the maintenance of the normal blood glucose concentration. [ABSTRACT FROM AUTHOR]

This paper aims to report a novel route to bursting by frequency switching for the slowly forced Duffing system. Typical fast-slow oscillations, i.e., the relaxation oscillations, can be observed in the slowly forced Duffing system. We find that when the slow forcing switches between two frequencies with a 2:1 ratio modulated by the velocity term, the equilibrium branches of the subsystems will alternate quickly. Accordingly, the trajectory will undergo fast transitions between the stable equilibrium branches of the subsystems. As a result, clusters of fast oscillations are created in the original relaxation oscillations. This way, the route to bursting by frequency switching is explained. Then, the effects of system parameters on the bursting are investigated. We show that whether the system produces slow motions or bursting is decided by the forcing amplitude, while the number of the fast oscillations in the clusters of bursting is dependent on the damping. Our results enrich the routes to bursting, and provide a reference for exploring bursting dynamics related to frequency switching modulated by the velocity term in other nonlinear dynamical systems. [ABSTRACT FROM AUTHOR]

Oscillation activities are widely observed in neurons and are critical to the brain's physiological functions. A significant phenomenon among these activities is the simultaneous presence of multiple oscillations at different frequencies, referred to as compound oscillations, which are particularly evident in epileptiform activity. However, the dynamical mechanisms underlying compound oscillations remain unknown. In this study, we develop and analyze a three-compartment pyramidal neuron model to address this problem. The model incorporates Na + , Ca 2 + , and N-methyl-D-aspartate (NMDA)-mediated firing behaviors in the soma, apical dendrite, and basal dendrite, respectively, capturing the multi-timescale dynamics essential for understanding compound oscillations. Phase-plane analysis reveals that Ca 2 + firing behaviors in the apical dendrite are relaxation oscillations, characterized by two timescales. Using geometric singular perturbation theory, we show that NMDA and Na + firing behaviors involve three timescales. Specifically, NMDA firing behaviors in the basal dendrite manifest as square-wave bursting, accompanied by Na + action potentials in the soma. Moreover, bifurcation analysis indicates that Ca 2 + firing behaviors lead to the alternation of homoclinic bifurcation and saddle-node bifurcation on an invariant cycle (SNIC), which causes the occurrence and disappearance of bursting in the basal dendrite. We also explore the impact of NMDA receptor conductance on these oscillatory patterns. Simulation results validate that impairment or excessive activation of NMDA receptors can lead to pathological compound oscillations, which have significant physiological implications. These insights gained from this model not only advance our understanding of neuronal function but also have potential implications for developing therapeutic strategies for neurological disorders characterized by compound oscillations. [ABSTRACT FROM AUTHOR]

Gamma oscillations (30-120 Hz) in the brain are not periodic cycles, but they typically appear in short-time windows, often called oscillatory bursts. While the origin of this bursting phenomenon is still unclear, some recent studies hypothesize its origin in the external or endogenous noise of neural networks. We demonstrate that an exact neural mass model of excitatory and inhibitory quadratic-integrate and fire-spiking neurons theoretically predicts the emergence of a different regime of intrinsic bursting gamma (IBG) oscillations without any noise source, a phenomenon due to collective chaos. This regime is indeed observed in the direct simulation of spiking neurons, characterized by highly irregular spiking activity. IBGoscillations are distinguished by higher phase-amplitude coupling to slower theta oscillations concerning noise-induced bursting oscillations, thus indicating an increased capacity for information transfer between brain regions. We demonstrate that this phenomenon is present in both globally coupled and sparse networks of spiking neurons. These results propose a new mechanism for gamma oscillatory activity, suggesting deterministic collective chaos as a good candidate for the origin of gamma bursts. [ABSTRACT FROM AUTHOR]

Unbonded flexible risers have been widely used in the field of offshore engineering in recent years due to their excellent performance in extreme dynamic marine environments, structural compliance, low installation cost, and low quality. And, the internal pressure capacity of unbonded flexible risers is an important indicator of the mechanical performance of unbonded flexible risers. Based on a 2.5-inch, 8-layer typical unbonded flexible riser model, this paper examines the burst failure of the pressure armor layer. Firstly, the balance equation of each separate cylindrical layer and helical layer is derived by functional principle, and then the overall theoretical modeling of an unbonded flexible riser under axisymmetric loads is established by additionally considering the geometric relation between adjacent layers. Secondly, fully considering the complex cross-sectional geometric characteristics and the interlayer's contact with the unbonded flexible riser, a simplified numerical 7-layer model is established by Abaqus, and the material with elastic-plastic properties is conferred. Finally, the validity of the proposed theoretical and numerical methods is verified through the axisymmetric behavior of the test data. Then the burst failure of the pressure armor layer is analyzed based on the material. At an internal pressure of 42 MPa, the pressure armor layer reached its yield stress of 300 MPa, with the entire cross-section yielding between 42 MPa and 42.5 MPa. Additionally, the effect of the friction coefficient is examined. [ABSTRACT FROM AUTHOR]

We believe our poly(lactic acid) (PLA) microbubbles are well suited for therapeutic delivery to spinal cord injury (SCI) using ultrasound-triggered bursting. We investigated the feasibility of clinical ultrasound bursting in situ , the optimal bursting parameters in vitro and the loading and release of a model bio-active DNA. Microbubbles were tested using clinical ultrasound in a rat cadaver SCI model. Burst pressure thresholds were determined using the change in enhancement after ultrasound exposure. Resonance frequency, acoustic enhancement, sizing and morphology were evaluated by comparing two microbubble porogens, ammonium carbonate and ammonium carbamate. Oligonucleotides were loaded into the shell and released using the found optimized ultrasound bursting parameters. In situ imaging and bursting were successful. In vitro bursting thresholds using frequencies 1, 2.25 and 5 MHz were identified between peak negative pressures 0.2 and 0.5 MPa, believed to be safe for spinal cord. The pressure threshold decreased with decreasing frequencies. PLA bursting was optimized near the resonance frequency of 2.5 to 3.0 MHz using 2.25 MHz and not at lower frequencies. PLA microbubbles, initially with a mean size of approximately 2 µm, remained in one piece, collapsed to between 0.5 and 1 µm and did not fragment. Significantly more oligonucleotide was released after ultrasound bursting of loaded microbubbles. Microbubble-sized debris was detected when using ammonium carbamate, leading to inaccurate microbubble concentration measurements. PLA microbubbles made with ammonium carbonate and burst at appropriate parameters have the potential to safely improve intrathecal therapeutic delivery to SCI using targeted ultrasound. [ABSTRACT FROM AUTHOR]

This paper presents an in-depth analysis of an excitable membrane of a biological system by proposing a novel approach that the cells of the excitable membrane can be modeled as the networks of memristors. We provide compelling evidence from the Chay neuron model that the state-independent mixed ion channel is a nonlinear resistor, while the state-dependent voltage-sensitive potassium ion channel and calcium-sensitive potassium ion channel function as generic memristors from the perspective of electrical circuit theory. The mechanisms that give rise to periodic oscillation, aperiodic (chaotic) oscillation, spikes, and bursting in an excitable cell are also analyzed via a small-signal model, a pole-zero diagram of admittance functions, local activity, the edge of chaos, and the Hopf bifurcation theorem. It is also proved that the zeros of the admittance functions are equivalent to the eigen values of the Jacobian matrix, and the presence of the positive real parts of the eigen values between the two bifurcation points lead to the generation of complicated electrical signals in an excitable membrane. The innovative concepts outlined in this paper pave the way for a deeper understanding of the dynamic behavior of excitable cells, offering potent tools for simulating and exploring the fundamental characteristics of biological neurons. [ABSTRACT FROM AUTHOR]

The post‐movement beta rebound has been studied extensively using magnetoencephalography (MEG) and is reliably modulated by various task parameters as well as illness. Our recent study showed that rebounds, which we generalise as "post‐task responses" (PTRs), are a ubiquitous phenomenon in the brain, occurring across the cortex in theta, alpha, and beta bands. Currently, it is unknown whether PTRs following working memory are driven by transient bursts, which are moments of short‐lived high amplitude activity, similar to those that drive the post‐movement beta rebound. Here, we use three‐state univariate hidden Markov models (HMMs), which can identify bursts without a priori knowledge of frequency content or response timings, to compare bursts that drive PTRs in working memory and visuomotor MEG datasets. Our results show that PTRs across working memory and visuomotor tasks are driven by pan‐spectral transient bursts. These bursts have very similar spectral content variation over the cortex, correlating strongly between the two tasks in the alpha (R2 =.89) and beta (R2 =.53) bands. Bursts also have similar variation in duration over the cortex (e.g., long duration bursts occur in the motor cortex for both tasks), strongly correlating over cortical regions between tasks (R2 =.56), with a mean over all regions of around 300 ms in both datasets. Finally, we demonstrate the ability of HMMs to isolate signals of interest in MEG data, such that the HMM probability timecourse correlates more strongly with reaction times than frequency filtered power envelopes from the same brain regions. Overall, we show that induced PTRs across different tasks are driven by bursts with similar characteristics, which can be identified using HMMs. Given the similarity between bursts across tasks, we suggest that PTRs across the cortex may be driven by a common underlying neural phenomenon. [ABSTRACT FROM AUTHOR]

Stochastic oscillations in individual cells are usually characterized by a nonmonotonic power spectrum with an oscillatory autocorrelation function. Here we develop an analytical approach to stochastic oscillations in a minimal hybrid model of stochastic gene expression including promoter state switching, protein synthesis and degradation, as well as a genetic feedback loop. The oscillations observed in our model are noise-induced since the deterministic theory predicts stable fixed points. The autocorrelated function, power spectrum, and steady-state distribution of protein concentration fluctuations are computed in closed form. Using the exactly solvable model, we illustrate sustained oscillations as a circular motion along a stochastic hysteresis loop induced by gene state switching. A triphasic stochastic bifurcation upon the increasing strength of negative feedback is observed, which reveals how stochastic bursts evolve into stochastic oscillations. In our model, oscillations tend to occur when the protein is relatively stable and when gene switching is relatively slow. Translational bursting is found to enhance the robustness and broaden the region of stochastic oscillations. These results provide deeper insights into R. Thomas's two conjectures for single-cell gene expression kinetics. [ABSTRACT FROM AUTHOR]

Large-span, post-tensioned (PT) beams play a crucial role in maximizing the benefits of post-tensioning techniques. Bonded and unbonded systems are prevalent, with the latter being more widespread in the United States. While bonded systems are advantageous for creating long spans when multiple tendons are grouped in ducts, limited studies in the literature exist on their demolition. With a case study, this paper addresses the unique challenge of demolishing large-span-bonded, post-tensioned beams that occurs due to a building's functional change. Emphasizing insights for engineers, it explores the use of cutting and dismantling methods, thereby considering the presence of prestressed cables. The demolition process is distinctive due to the presence of numerous prestressed cables along the beams, necessitating a specialized and cautious cutting approach. This is accomplished through the use of a drilling technique that selectively distresses the tendons, ensuring they are not all affected simultaneously. An intriguing observation discussed in this paper pertains to the occurrence of horizontal cracks accompanied by loud sounds following the drilling process, thereby offering insights from the design perspective of PT systems. This paper details an innovative method for safely demolishing large-span, bonded PT beams using ground-penetrating radar and computer models to navigate structural complexities and ensure nearby structures' safety. [ABSTRACT FROM AUTHOR]

Gamma oscillations (30–120 Hz) in the brain are not periodic cycles, but they typically appear in short-time windows, often called oscillatory bursts. While the origin of this bursting phenomenon is still unclear, some recent studies hypothesize its origin in the external or endogenous noise of neural networks. We demonstrate that an exact neural mass model of excitatory and inhibitory quadratic-integrate and fire-spiking neurons theoretically predicts the emergence of a different regime of intrinsic bursting gamma (IBG) oscillations without any noise source, a phenomenon due to collective chaos. This regime is indeed observed in the direct simulation of spiking neurons, characterized by highly irregular spiking activity. IBG oscillations are distinguished by higher phase-amplitude coupling to slower theta oscillations concerning noise-induced bursting oscillations, thus indicating an increased capacity for information transfer between brain regions. We demonstrate that this phenomenon is present in both globally coupled and sparse networks of spiking neurons. These results propose a new mechanism for gamma oscillatory activity, suggesting deterministic collective chaos as a good candidate for the origin of gamma bursts.

Parkinson's disease is associated with bursting of the thalamic (TC) neuron, which receives the inhibitory synaptic current of the basal ganglia composed of multiple nuclei; deep brain stimulation (DBS) applied to the basal ganglia can eliminate the bursting to recover to the normal state. In this paper, the complex nonlinear dynamics for the appearance and disappearance of the bursting are obtained in a widely used theoretical model of a neuronal network. First, through a bifurcation analysis, isolated TC neurons exhibit paradoxical bursting induced from the resting state by enhanced inhibitory effect, which is different from the common view that the enhanced inhibitory effect should suppress the electrical behaviors. Second, the mechanism for the appearance of bursting is obtained by analyzing the electrical activities of the basal ganglia. The inhibitory synaptic current from the external segment of the globus pallidus (GPe) induces a reduced firing rate of the subthalamic nucleus (STN); then, an excitatory synaptic current from the STN induces the bursting behaviors of the GPe. The excitatory current of STN neurons and the inhibitory current of the GPe cause bursting behaviors of the internal segment of the globus pallidus (GPi), thus resulting in an enhanced inhibition from the GPi to the TC, which can induce the paradoxical bursting similar to the isolated TC neurons. Third, the cause for the disappearance of paradoxical bursting is acquired.The high frequency pulses of DBS induces enhanced firing activity of the STN and GPe neurons and enhanced inhibitory synaptic current from the GPe to the GPi, resulting in a reduced inhibitory effect from the GPi to the TC, which can eliminate the paradoxical bursting. Finally, the fast-slow dynamics of the paradoxical bursting of isolated TC neurons are acquired, which is related to the saddle-node and saddle-homoclinic orbit bifurcations of the fast subsystem of the TC neuron model. The results provide theoretical support for understanding the mechanism of Parkinson's disease and treatment methods such as DBS.

Implementing neuron circuit using memristor can be more effective thanks to some properties of memristor such as nonlinearity. For this reason, many memristor-based neuron circuits have been found in the literature. This study presents a memristor-based floating neuron circuit that exhibits different types of spikes. In the proposed circuit, two classical memristors and one special memristor are utilized. The special memristor is designed to exhibit various pinched hysteresis loops and plays an important role in producing different spike types. The proposed special memristor can also be controlled using only one voltage source. Using memristors, we implemented a neuron circuit which can produce regular spike, bursting spike and fast spike. Also, neuron circuit has a floating structure, and so there is no restriction on using it with other circuit elements. All simulations are implemented in the SPICE simulation program with TSMC 0.18- μ m CMOS process parameters. [ABSTRACT FROM AUTHOR]

Gene expression comprises many asymmetric and complex processes. Transcriptional details revealed by the whole genome indicate that genes resort to transcriptional bursting and accumulate molecular memory. However, it is still unclear how the interplay of transcriptional bursting and memory regulates robustness and expression noise. Here, we consider a model of multiple coupled processes of protein polymerization to focus on decoding the effect of molecular memory. Using non-Markovian transformation technology, we first define the memory index to measure the correlation window of expression to decipher the mechanism of regulation. The results indicate that memory from synthesis can amplify expression noise, while memory originating from polymerization can reduce the lower bound of the noise of gene products; that is, the memory from different sources plays distinct regulatory roles to induce non-symmetry. Moreover, it is counterintuitive that the dual regulation from memory and bursting expression can directly suppress system noise, violating the principle that transcriptional bursting enhances noise. Our results not only provide a theoretical framework for investigating the function of memory but also imply that expression noise is not part of a half-power relationship with, nor mediated by, memory. [ABSTRACT FROM AUTHOR]

Parkinson's disease is associated with bursting of the thalamic (TC) neuron, which receives the inhibitory synaptic current of the basal ganglia composed of multiple nuclei; deep brain stimulation (DBS) applied to the basal ganglia can eliminate the bursting to recover to the normal state. In this paper, the complex nonlinear dynamics for the appearance and disappearance of the bursting are obtained in a widely used theoretical model of a neuronal network. First, through a bifurcation analysis, isolated TC neurons exhibit paradoxical bursting induced from the resting state by enhanced inhibitory effect, which is different from the common view that the enhanced inhibitory effect should suppress the electrical behaviors. Second, the mechanism for the appearance of bursting is obtained by analyzing the electrical activities of the basal ganglia. The inhibitory synaptic current from the external segment of the globus pallidus (GPe) induces a reduced firing rate of the subthalamic nucleus (STN); then, an excitatory synaptic current from the STN induces the bursting behaviors of the GPe. The excitatory current of STN neurons and the inhibitory current of the GPe cause bursting behaviors of the internal segment of the globus pallidus (GPi), thus resulting in an enhanced inhibition from the GPi to the TC, which can induce the paradoxical bursting similar to the isolated TC neurons. Third, the cause for the disappearance of paradoxical bursting is acquired.The high frequency pulses of DBS induces enhanced firing activity of the STN and GPe neurons and enhanced inhibitory synaptic current from the GPe to the GPi, resulting in a reduced inhibitory effect from the GPi to the TC, which can eliminate the paradoxical bursting. Finally, the fast-slow dynamics of the paradoxical bursting of isolated TC neurons are acquired, which is related to the saddle-node and saddle-homoclinic orbit bifurcations of the fast subsystem of the TC neuron model. The results provide theoretical support for understanding the mechanism of Parkinson's disease and treatment methods such as DBS. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Parametric resonance can induce an instability at half the excitation frequency, which has been comprehensively utilized in energy harvesting. However, the vibration energy harvesting with parametric excitation frequency far away from the natural frequency has received less report. To implement this issue, this paper considers a novel bursting energy harvesting under parametric excitation, the harvester is realized by employing a parametrically excited buckled beam, and the bursting phenomenon of the system is discussed. Based on the method of fast-slow dynamics analysis, the behaviors of bursting response under monostable and bistable configurations are presented, the multiple-frequency oscillation is devoted to observing the complex bursting patterns, and then the jump multi-value phenomena are evaluated. Furthermore, the bursting harvesting performances of the monostable and the bistable configurations are compared, and it is found that the bistable configuration generates more average voltage in a period, so the bistable configuration is much superior to the monostable case. [ABSTRACT FROM AUTHOR]

Background: Lumbar synovial cysts (LSC), best diagnosed on MR studies, may cause symptoms/signs ranging from unilateral radiculopathy to cauda equina compressive syndromes. Attempts at percutaneous treatment of LSC typically fail. Rather, greater safety/efficacy is associated with direct surgical resection with/without fusion. Methods: Treatment of LSC with percutaneous techniques, including cyst aspiration/perforation, injection (i.e., with/without steroids, saline/other), dilatation, and/or disruption/bursting, classically fail. This is because LSCs' tough, thickened, and adherent fibrous capsules cause extensive thecal sac/nerve root compression, and contain minimal central "fluid" (i.e., "crank-case" and non-aspirable). Multiple percutaneous attempts at decompression, therefore, typically cause several needle puncture sites risking dural tears (DT)/cerebrospinal fluid (CSF) leaks, direct root injuries, failure to decompress the thecal sac/nerve roots, infections, hematomas, and over the longerterm, adhesive arachnoiditis. Results: Alternatively, many studies document the success of direct or even partial resection of LSC (i.e., partial removal with marked cyst/dural adhesions with shrinking down the remnant of capsular tissue). Surgical decompressions of LSC, ranging from focal laminotomies to laminectomies, may or may not warrant additional fusions. Conclusions: Symptomatic LSC are best managed with direct or even partial operative resection/decompression with/without fusion. The use of varying percutaneous techniques classically fails, and increases multiple perioperative risks. [ABSTRACT FROM AUTHOR]

Transient synchronization of bursting activity in neuronal networks, which occurs in patterns of metastable itinerant phase relationships between neurons, is a notable feature of network dynamics observed in vivo. However, the mechanisms that contribute to this dynamical complexity in neuronal circuits are not well understood. Local circuits in cortical regions consist of populations of neurons with diverse intrinsic oscillatory features. In this study, we numerically show that the phenomenon of transient synchronization, also referred to as metastability, can emerge in an inhibitory neuronal population when the neurons’ intrinsic fast-spiking dynamics are appropriately modulated by slower inputs from an excitatory neuronal population. Using a compact model of a mesoscopic-scale network consisting of excitatory pyramidal and inhibitory fast-spiking neurons, our work demonstrates a relationship between the frequency of pyramidal population oscillations and the features of emergent metastability in the inhibitory population. In addition, we introduce a method to characterize collective transitions in metastable networks. Finally, we discuss potential applications of this study in mechanistically understanding cortical network dynamics.

Neuronal bursting patterns are nonlinear behaviors related to various brain functions and diseases. Bursting modulated by two slow variables manifest more complex dynamics than that with one slow variable, due to involved with more bifurcations of fast subsystem. The traditional dissection method or singular perturbation method often fails to analyze the bursting with two slow variables, for instance, a complex mixed-mode oscillation (MMO) bursting observed in the immature inner hair cell related to the development of auditory function. The MMO bursting exhibits alternation between a single spike with large amplitude and a pseudo-plateau burst behaving as fast burst with small oscillations. In the present paper, the MMO bursting is successfully analyzed using a novel dissection process. With two slow variables c and h regarded as bifurcation parameters of the fast subsystem, various dynamical behaviors and bifurcation curves are obtained. By identifying real intersections between the bursting trajectory and bifurcation curves in the (c, h, V) space instead of (c, h) plane, the pseudo-plateau burst is built relationships to the depolarization block and subcritical Hopf bifurcation of the fast subsystem, and the spike is associated with coexisting firing and limit point bifurcation of cycles. Interestingly, no quiescent state is identified to be related to the resting state or saddle-node bifurcation on an invariant cycle (SNIC), due to that c is not slow enough. As c becomes sufficiently slow, the bursting pattern is associated with the resting state and the SNIC. In addition, the bursting trajectory exhibits a narrow shape around an oblique line in the (c, h) plane, and the bifurcations along the line presents a simple and effective candidate to characterize the bursting. The results present effective process of dissection method and deep understanding of the MMO bursting, which are helpful for modulating the development of auditory functions related to the inner hair cell. [ABSTRACT FROM AUTHOR]

Abstract Despite the recent rise of RNA-seq datasets combining single-cell (sc) resolution with 4-thiouridine (4sU) labelling, analytical methods exploiting their power to dissect transcriptional bursting are lacking. Here, we present a mathematical model and Bayesian inference implementation to facilitate genome-wide joint parameter estimation and confidence quantification (R package: burstMCMC). We demonstrate that, unlike conventional scRNA-seq, 4sU scRNA-seq resolves temporal parameters and furthermore boosts inference of dimensionless parameters via a synergy between single-cell resolution and 4sU labelling. We apply our method to published 4sU scRNA-seq data and linked with ChIP-seq data, we uncover previously obscured associations between different parameters and histone modifications.

Unbonded flexible risers have been widely used in the field of offshore engineering in recent years due to their excellent performance in extreme dynamic marine environments, structural compliance, low installation cost, and low quality. And, the internal pressure capacity of unbonded flexible risers is an important indicator of the mechanical performance of unbonded flexible risers. Based on a 2.5-inch, 8-layer typical unbonded flexible riser model, this paper examines the burst failure of the pressure armor layer. Firstly, the balance equation of each separate cylindrical layer and helical layer is derived by functional principle, and then the overall theoretical modeling of an unbonded flexible riser under axisymmetric loads is established by additionally considering the geometric relation between adjacent layers. Secondly, fully considering the complex cross-sectional geometric characteristics and the interlayer’s contact with the unbonded flexible riser, a simplified numerical 7-layer model is established by Abaqus, and the material with elastic-plastic properties is conferred. Finally, the validity of the proposed theoretical and numerical methods is verified through the axisymmetric behavior of the test data. Then the burst failure of the pressure armor layer is analyzed based on the material. At an internal pressure of 42 MPa, the pressure armor layer reached its yield stress of 300 MPa, with the entire cross-section yielding between 42 MPa and 42.5 MPa. Additionally, the effect of the friction coefficient is examined.

This paper presents an in-depth analysis of an excitable membrane of a biological system by proposing a novel approach that the cells of the excitable membrane can be modeled as the networks of memristors. We provide compelling evidence from the Chay neuron model that the state-independent mixed ion channel is a nonlinear resistor, while the state-dependent voltage-sensitive potassium ion channel and calcium-sensitive potassium ion channel function as generic memristors from the perspective of electrical circuit theory. The mechanisms that give rise to periodic oscillation, aperiodic (chaotic) oscillation, spikes, and bursting in an excitable cell are also analyzed via a small-signal model, a pole-zero diagram of admittance functions, local activity, the edge of chaos, and the Hopf bifurcation theorem. It is also proved that the zeros of the admittance functions are equivalent to the eigen values of the Jacobian matrix, and the presence of the positive real parts of the eigen values between the two bifurcation points lead to the generation of complicated electrical signals in an excitable membrane. The innovative concepts outlined in this paper pave the way for a deeper understanding of the dynamic behavior of excitable cells, offering potent tools for simulating and exploring the fundamental characteristics of biological neurons.

Physiological experiments have demonstrated that M-current ( I M ) and persistent sodium current ( I NaP ) expressed in rhythm-generating neurons play a key role in the generation and regulation of locomotor rhythms. However, the intrinsic mechanisms by which these two ionic currents control the locomotor rhythms are poorly understood. Here, a computational model is constructed to investigate the roles of I M and I NaP in regulating locomotor rhythms and explain the underlying ionic mechanisms. The simulation results show that decreasing I M or increasing I NaP facilitates the generation of the bursting activity; during the bursting activity, the burst frequency of the model has a positive dependence on I M , and the flexion-extension as well as left-right coordination are not affected by varying I M . These results accurately reproduce the experimental results. In addition, the results also show that the dependence of burst frequency- I NaP is similar to that of burst frequency- I M , but with distinct regulation mechanisms, i.e. I M regulates the burst frequency by affecting the burst and interburst durations, whereas I NaP regulates the burst frequency via manipulating the interburst duration. Finally, a dynamical analysis is given to reveal the intrinsic neural mechanisms of I M and I NaP in regulating the burst properties. Our study provides new insights into how outward and inward currents work in tandem to set the speed of locomotion, and provides testable predictions for biological experimental studies. [ABSTRACT FROM AUTHOR]

The network activity of the pre-Bötzinger complex (pre-BötC) in the mammalian brainstem controls the inspiratory phase of the respiratory rhythm. Because fluctuations in the action potentials of neurons can generate a magnetic field in the medium, we consider a flux-controlled memristor in the model of the isolated embryonic pre-BötC neuron featuring two distinct bursting mechanisms: depolarization block (DB) bursting and mixed bursting in this work. As the slow variables h and Ca i are at almost the same time scale, we combine two fast–slow analyses with the codimension-2 bifurcation analysis of these variables to identify the dynamical mechanisms of DB bursting and mixed bursting. We precisely define the bursting discharges according to topology by determining the bifurcations ranging from the resting state to the spiking state and vice versa, as well as bifurcations of the hysteresis loop for the upper and lower states with bistability. Our analysis provides a new perspective on the fast–slow analysis of the bursting mechanism. The results not only provide a reference for research on the effects of magnetic current on the firing patterns of neurons, but also offer insights for further exploring bursting from a dynamic perspective. [ABSTRACT FROM AUTHOR]

The paradoxical phenomena that excitatory modulation does not enhance but reduces or inhibitory modulation not suppresses but promotes neural firing activities have attracted increasing attention. In the present study, paradoxical phenomena induced by both fast excitatory and inhibitory autapses in a "Fold/Big Homoclinic" bursting are simulated, and the corresponding nonlinear and biophysical mechanisms are presented. Firstly, the enhanced conductance of excitatory autapse induces the number of spikes per burst and firing rate reduced, while the enhanced inhibitory autapse cause both indicators increased. Secondly, with fast-slow variable dissection, the burst of bursting is identified to locate between a fold bifurcation and a big saddle-homoclinic orbit bifurcation of the fast subsystem. Enhanced excitatory or inhibitory autapses cannot induce changes of both bifurcation points, i.e., burst width. However, width of slow variable between two successive spikes within a burst becomes wider for the excitatory autapse and narrower for the inhibitory autapse, resulting in the less and more spikes per burst, respectively. Last, the autaptic current of fast autapse mainly plays a role during the peak of action potential, differing from the slow autaptic current with exponential decay, which can play roles following the peak of action potential. The fast excitatory autaptic current enhances the amplitude of the action potential and reduces the repolarization of the action potential to lengthen the interspike interval (ISI) of the spiking of the fast subsystem, resulting in the wide width of slow variable between successive spikes. The fast inhibitory autaptic current reduces the amplitude of action potential and ISI of spiking, resulting in narrow width of slow variable. The novel example of the paradoxical responses for both fast modulations and nonlinear mechanism extend the contents of neurodynamics, which presents potential functions of the fast autapse. [ABSTRACT FROM AUTHOR]

Classical gene expression models assume exponential switching time distributions between the active and inactive promoter states. However, recent experiments have shown that many genes in mammalian cells may produce nonexponential switching time distributions, implying the existence of multiple promoter states and molecular memory in the promoter switching dynamics. Here we analytically solve a gene expression model with random bursting and complex promoter switching, and derive the time-dependent distributions of the mRNA and protein copy numbers, generalizing the steady-state solution obtained in [T. Zhou and J. Zhang, SIAM J. Appl. Math., 72 (2012), pp. 789--818] and [U. Herbach, SIAM J. Appl. Math., 79 (2019), pp. 1007--1029]. Using multiscale simplification techniques, we find that molecular memory has no influence on the time-dependent distribution when promoter switching is very fast or very slow, while it significantly affects the distribution when promoter switching is neither too fast nor too slow. By analyzing the dynamical phase diagram of the system, we also find that molecular memory in the inactive gene state weakens transient and stationary bimodality of the copy number distribution, while molecular memory in the active gene state enhances such bimodality. [ABSTRACT FROM AUTHOR]

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The purpose is to study the periodic regimes of the dynamics for two non-identical predator–prey communities coupled by migrations, associated with the partial synchronization of fluctuations in the abundance of communities. The combination of fluctuations in neighboring sites leads to the regimes that include both fast bursts (bursting oscillations) and slow oscillations (tonic spiking). These types of activity are characterized by a different ratio of synchronous and non-synchronous dynamics of communities in certain periods of time. In this paper, we describe scenarios of the transition between different types of burst activity. These types of dynamics differ from each other not so much in size, shape, and number of spikes in a burst, but in the order of these bursts relative to the slow-fast cycle. Methods. To study the proposed model, we use the bifurcation analysis methods of dynamic systems, as well as geometric methods based on the division of the full system into fast and slow equations (subsystems). Results. We showed that the dynamics of the first subsystem with a slow-fast limit cycle directly determines the dynamics of the second one with burst activity through a smooth dependence of regime on the number of predators and a non-smooth dependence on the number of prey. We constructed the invariant manifolds on which there are parts of dynamics with tonic (slow manifold) and burst (fast manifold) activity of the full system. Conclusion. We described the scenario for bursting with different waveforms, which are determined by the appearance of the fast invariant manifold and the location of its parts relative to the slow-fast cycle. The transitions between different types of burst are accompanied by a change in the oscillation period, the degree of synchronization, and, as a result, the dynamics becomes quasi-periodic when both communities are not synchronous with each other.

The asymmetric memristive diode bridge-based Sallen-Key Filter (AMSKF) achieved by introducing an asymmetry diode bridge connected with a capacitor and an inductor to the Sallen-Key Filter, is studied in this paper. Through the analysis of equilibrium point, the stability of the circuit is discussed. Combined with the bifurcation diagram, it can be seen that the negative feedback gain of the Sallen-Key Filter greatly affects the dynamics of the circuit. Diverse dynamical behaviors are discovered by means of phase portraits and Lyapunov exponents, which include six types of typical oscillating behaviors: Period, Quasi-period, Quasi-periodic bursting, Period-2 bursting, Chaotic bursting and Period-1 bursting. Especially, bifurcation mechanisms of various bursting oscillating behaviors are researched by separating the formal equations into two parts, consisting of the fast spiking subsystem and the slow spiking subsystem, based on the fast-slow analysis method. Finally, Multisim experiments are carried out to validate the results of numerical simulations. Compared with the Sallen-Key Filter cascaded with the symmetric memristive diode bridge, the bursting oscillation with larger amplitude and the wider periodic bursting range by adjusting the negative feedback gain are detected.

Fast and slow inhibitory synapses, respectively, induce anti- and in-phase synchronizations, showing different roles of synapse with different time scales. In the present paper, the opposite roles of inhibitory autapses with fast and slow time scales on modulating bursting activities are investigated in a theoretical model, which present a novel viewpoint on the inhibitory autapse and bursting observed in the brain neurons. Firstly, the inhibitory autapses with fast and slow decay time constant are identified to induce enhancement and reduction of bursting activities, respectively, which presents a paradoxical phenomenon and a common phenomenon. Secondly, the bifurcation mechanisms for the paradoxical and common responses are acquired. As autaptic conductance increases, for fast autapse, saddle-node (SN) bifurcation point of the fast subsystem is nearly fixed, while saddle-homoclinic orbit (SH) bifurcation point moves to right to widen the burst region and enhance the bursting activities, while more left shift of SN bifurcation curve than SH bifurcation curve to shorten the burst region and reduce the bursting activities, which is acquired by a novel fast–slow variable dissection method with two slow variables (slow variable C of the model and gating variable of autapse S). Finally, fast and slow dynamics of autaptic current underlying the bifurcation mechanisms are acquired. For the fast autapse, the autaptic current is negative during spike to reduce the spike amplitude to shift the SH point, while it exhibits fast decay to zero between spikes (i.e., node), which cannot influence the SN point. For the slow autapse, the autaptic current exhibits negative value during both the burst and quiescent (between burst) due to slow decay, which induces left shift of both the SN and SH bifurcation curves. The results of the opposite response of bursting to fast and slow autaptic currents present potential functions and diverse dynamics of autapse with different time scales in brain neurons, a novel case of counterintuitive phenomenon related to inhibitory self-feedback, and a novel performance process of analysis method to complex bursting with two slow variables. [ABSTRACT FROM AUTHOR]

β-cells within the endocrine pancreas are fundamental for glucose, lipid and protein homeostasis. Gap junctions between cells constitute the primary coupling mechanism through which cells synchronize their electrical and metabolic activities. This evidence is still only partially investigated through models and numerical simulations. In this contribution, we explore the effect of combined electrical and metabolic coupling in β-cell clusters using a detailed biophysical model. We add heterogeneity and stochasticity to realistically reproduce β-cell dynamics and study networks mimicking arrangements of β-cells within human pancreatic islets. Model simulations are performed over different couplings and heterogeneities, analyzing emerging synchronization at the membrane potential, calcium, and metabolites levels. To describe network synchronization, we use the formalism of multiplex networks and investigate functional network properties and multiplex synchronization motifs over the structural, electrical, and metabolic layers. Our results show that metabolic coupling can support slow wave propagation in human islets, that combined electrical and metabolic synchronization is realized in small aggregates, and that metabolic long-range correlation is more pronounced with respect to the electrical one.

Gene expression comprises many asymmetric and complex processes. Transcriptional details revealed by the whole genome indicate that genes resort to transcriptional bursting and accumulate molecular memory. However, it is still unclear how the interplay of transcriptional bursting and memory regulates robustness and expression noise. Here, we consider a model of multiple coupled processes of protein polymerization to focus on decoding the effect of molecular memory. Using non-Markovian transformation technology, we first define the memory index to measure the correlation window of expression to decipher the mechanism of regulation. The results indicate that memory from synthesis can amplify expression noise, while memory originating from polymerization can reduce the lower bound of the noise of gene products; that is, the memory from different sources plays distinct regulatory roles to induce non-symmetry. Moreover, it is counterintuitive that the dual regulation from memory and bursting expression can directly suppress system noise, violating the principle that transcriptional bursting enhances noise. Our results not only provide a theoretical framework for investigating the function of memory but also imply that expression noise is not part of a half-power relationship with, nor mediated by, memory.

Cholinergic interneurons in the striatum, also known as tonically active interneurons or TANs, are thought to have a strong effect on corticostriatal plasticity and on striatal activity and outputs, which in turn play a critical role in modulating downstream basal ganglia activity and movement. Striatal TANs can exhibit a variety of firing patterns and responses to synaptic inputs; furthermore, they have been found to display various surges and pauses in activity associated with sensory cues and reward delivery in learning as well as with motor tic production. To help explain the factors that contribute to TAN activity patterns and to provide a resource for future studies, we present a novel conductance-based computational model of a striatal TAN. We show that this model produces the various characteristic firing patterns observed in recordings of TANs. With a single baseline tuning associated with tonic firing, the model also captures a wide range of TAN behaviors found in previous experiments involving a variety of manipulations. In addition to demonstrating these results, we explain how various ionic currents in the model contribute to them. Finally, we use this model to explore the contributions of the acetylcholine released by TANs to the production of surges and pauses in TAN activity in response to strong excitatory inputs. These results provide predictions for future experimental testing that may help with efforts to advance our understanding of the role of TANs in reinforcement learning and in motor disorders such as Tourette's syndrome. [ABSTRACT FROM AUTHOR]

In this manuscript, considering a piezoelectric buckled beam system under fast–slow excitation, the energy harvesting with bursting regimes is discussed analytically and numerically. For the fast sub-system, the averaging process with the generalized harmonic balancing method shows that pitchfork bifurcations will result in small amplitude buckled configurations and large-amplitude configuration centering around the trivial branch. Meanwhile, folds of cycle initiate additional coexisting branches. The structures of the numerical bifurcation diagram are consistent with the analytical results. Moreover, when the amplitude of the fast excitation is relatively large, long-term chaotic transients can be observed. Considering two cases of low-frequency excitation, i.e., the quasi-static one and non-static one, the corresponding bursting patterns are discussed. For the quasi-static case, the fast–slow analysis shows that the fractal basin of the fast sub-system evokes the snap-through transition of the fast–slow flow. Particularly, when the fast sub-system possesses strong transients, the fast–slow flow presents distinct long-term snap-through behaviors. While for the non-static case, the motions of the fast–slow flow are totally dominated by the transient effects. Analysis about the averaged output power shows that introducing the low-frequency excitation to the buckled beam harvester can help broadening the output bandwidth. Moreover, when the transient effects of the fast sub-system are relatively weak, the non-static slow excitation always provides better output performance. However, if the fast sub-system possesses strong transients, there exists a band within which the quasi-static slow excitation provides higher output power. [ABSTRACT FROM AUTHOR]

This study investigates the distributions of velocity and Reynolds stress in an artificial pool-riffle sequence for two entrance slopes of 5° and 20° in a laboratory and compares the results with a similar pool-riffle sequence in a gravel-bed river in central Iran. Quadrant analysis is applied to find out the contributions of different events on turbulent flow structures. At an entrance slope of 5°, the velocity distribution follows an exponential trend without flow separation, but for the entrance slope of 20°, the velocity distribution indicates a S-shaped pattern with flow separation. Variation of entrance slope does not influence the convex form of Reynolds stress (RS) distribution, but it influences the location of the maximum value of RS and the flow separation zone length. The results reveal that outward and ejection are the dominant events for both field and laboratory settings. The sweep displays a decreasing trend from near the bed toward the water surface, however, the outward contribution indicates an increasing trend from the bed toward the water surface. The agreement between laboratory and field results in velocity and Reynolds stress will help the river engineers to better manage complex fluvial processes. Bursting process events depend on the aspect ratio for the same entrance pool slope. The agreement in the results of velocity and Reynolds stress distributions and the dominant events of bursting process in the laboratory and field are encouraging for better restoration of rivers and decreasing the cost of projects. [ABSTRACT FROM AUTHOR]

The bursting discharge behaviour of neurons is affected by many factors, among which temperature is one of the more important factors. In this work, we study the bursting discharge behaviour and dynamics process of two different temperature-sensitive ion channels, the temperature-sensitive potassium current and the temperature-sensitive calcium current. In the case of the temperature-sensitive potassium current, the bursting discharge waveforms, codimension-1 bifurcations and trajectory plots at different temperatures indicate that five different types of bursting discharge (Hopf/Flip, Hopf/Homoclinic, Fold/Homoclinic, Fold/Fold Cycle, Circle/Big Homoclinic) appear with increasing temperature. In the case of temperature-sensitive calcium current, two types of bursting discharge (Circle/Big Homoclinic, Fold/Fold Cycle) emerge. According to the bursting discharge waveforms, the rise in temperature can promote the generation of bursting discharge at the beginning, and finally, the bursting discharge phenomenon disappears. This is consistent with the experimental results that blocking potassium and calcium currents can promote the bursting of Purkinje neurons. Then, it can be seen from the codimension-2 bifurcation and the waveform area distribution diagrams that even if the dynamic paths are consistent, the bursting discharge types and the waveforms may be different. In contrast, even if the bursting discharge type is the same, the dynamic paths and the waveform may be different. These results provide insight into the effect of temperature on the neuronal dynamics and bursting behaviour of temperature-sensitive ion channels. [ABSTRACT FROM AUTHOR]

Mechanical properties of textile fabric are one of the most important parameters of fabric in the selection of appropriate fabric for clothing industries. The main aim of this paper is to study the effect of the tension applied during weaving on tear, tensile, and bursting strength of plain woven cotton fabric. Five plain woven cotton fabrics were produced on an air-jet loom at different tension levels (0.9KN, 1.3KN, 1.6KN, 2KN, and 2.3KN). The results obtained from ANOVA and bar chart showed that as the tension of the warp yarn and the fabric increase during weaving, the tear strength, tensile strength, and bursting strength of the plain cotton woven fabric decreased significantly. The effect is more noticeable in the warp direction of the fabric for tear and tensile strength as the tension was applied in the warp direction.

Transcription is an episodic process characterized by probabilistic bursts, but how the transcriptional noise from these bursts is modulated by cellular physiology remains unclear. Using simulations and single-molecule RNA counting, we examined how cellular processes influence cell-to-cell variability (noise). The results show that RNA noise is higher in the cytoplasm than the nucleus in ∼85% of genes across diverse promoters, genomic loci, and cell types (human and mouse). Measurements show further amplification of RNA noise in the cytoplasm, fitting a model of biphasic mRNA conversion between translation- and degradation-competent states. This multi-state translation-degradation of mRNA also causes substantial noise amplification in protein levels, ultimately accounting for ∼74% of intrinsic protein variability in cell populations. Overall, the results demonstrate how noise from transcriptional bursts is intrinsically amplified by mRNA processing, leading to a large super-Poissonian variability in protein levels.