Burst Behavior Research Articles

Big data for smart cities with KNIME a real experience in the SmartSantander testbed

SummaryBig data techniques are conceived as the powerful tool to exploit all the potential of the Internet of Things and the smart cities. A new dimension of understanding about the human behaviours is expected to be reached through all the gathered data in the emerging smart environment. The described potential, so‐called Human Dynamics, pursues to describe in real‐time the human behaviours and activities. This work presents our experiences for big data analytics in smart cities, in terms of sensors data management, data fusion and knowledge discovery from the data. The data used is from the European Project SmartSantander, where the traffic behaviour has been correlated with respect to the temperature in the Santander City. The evolution of both flows present a similar behaviour, in detail, a fine grain correlation is discovered. On the one hand, the traffic distribution, aggregated by temperature bins, follows up a Poisson distribution model. The Poisson modelling allows to interpolate and predict complex behaviours based on simple measures such as the temperature. At the same time, on the other hand, the isolated traffic density distribution, without taking into account the temperature‐based aggregation has been analysed. The traffic distribution has presented a burst behaviour, which presents a closer model to the human dynamics. Therefore, this work presents as the smart cities data can be modelled as Poisson or Human Dynamics (burst models). Finally, reference data analytics process, data sets and models are offered for the Open Source Data analytics platform Konstanz Information Miner (KNIME). Copyright © 2014 John Wiley & Sons, Ltd.

DETAILED INVESTIGATIONS OF THE DIMMEST BURSTS FROM TWO MAGNETARS, SGR J0501+4516 AND SGR J1550–5418

We applied the Bayesian blocks representation technique to search for the dimmest bursts from two magnetars: we identified 320 events from SGR J0501+4516 using a deep XMM-Newton observation and 404 bursts from SGR J1550-5418 using two Swift/XRT pointings. The fluence level of our sample for both sources are about 1-2 orders of magnitude lower than earlier studies. We systematically investigated morphological characteristics and duration distributions of these bursts, as these properties are directly obtained from their Bayesian blocks profiles. We also studied the spectral behavior of the dimmest bursts, which were grouped based on the morphological types and fluences. Our results helped us further differentiate the spectral nature of very dim bursts from that of the persistent emission, both fitted with physically motivated continuum emission models. Moreover, we generated the differential burst fluence distribution for these two magnetars in the lowest fluence regime.

SUPREME LOCAL LYAPUNOV EXPONENTS AND CHAOTIC IMPULSIVE SYNCHRONIZATION

Impulsively synchronized chaos with criterion from conditional Lyapunov exponent is often interrupted by desynchronized bursts. This is because the Lyapunov exponent cannot characterize local instability of synchronized attractor. To predict the possibility of the local instability, we introduce a concept of supreme local Lyapunov exponent (SLLE), which is defined as supremum of local Lyapunov exponents over the attractor. The SLLE is independent of the system trajectories and therefore, can characterize the extreme expansion behavior in all local regions with prescribed finite-time interval. It is shown that the impulsively synchronized chaos can be kept forever if the largest SLLE of error dynamical systems is negative and then the burst behavior will not appear. In addition, the impulsive synchronization with negative SLLE allows large synchronizable impulsive interval, which is significant for applications.

Indications for a slow rotator in the Rapid Burster from its thermonuclear bursting behaviour

We perform time-resolved spectroscopy of all the type I bursts from the Rapid Burster (MXB 1730-335) detected with the Rossi X-ray Timing Explorer. Type I bursts are detected at high accretion rates, up to \sim 45% of the Eddington luminosity. We find evidence that bursts lacking the canonical cooling in their time-resolved spectra are, none the less, thermonuclear in nature. The type I bursting rate keeps increasing with the persistent luminosity, well above the threshold at which it is known to abruptly drop in other bursting low-mass X-ray binaries. The only other known source in which the bursting rate keeps increasing over such a large range of mass accretion rates is the 11 Hz pulsar IGR J17480$-$2446. This may indicate a similarly slow spin for the neutron star in the Rapid Burster.

Emergence of spiral wave induced by defects block

The development of spiral wave in the regular network of Hindmarsh–Rose neurons with nearest-neighbor connection is investigated under no-flux and/or periodical boundary condition, respectively. At first, specific initial values are selected to detect the formation of spiral wave, it is found that the developed state is controlled by the bifurcation s, which controls the electric activity of neuron from spiking to burst behavior, and different developed states are observed. Furthermore, the formation of ordered wave induced by the defect block in the network of neurons is also investigated. In the numerical studies, the first step is to generate target-like wave by imposing a discrepant forcing current (not periodical signal) on a local region, the second step is to produce an artificial defect by setting the variables in a local area to zero. The supposed defect is used to block the propagation of target wave in the network, and the condition for spiral wave emergence is investigated in a numerical way. It indicates that the existence of defect in the media accounts for the emergence of spiral wave though most of the previous works used to simulate the development of spiral wave by using specific initial values. A statistical factor of synchronization in the two-dimensional space is defined to detect the appearance and robustness of spiral wave in the network of neurons. It is confirmed that the contour profile of the developed pattern is dependent on the intensity of coupling and defects block.

Scale-free behavior of displacement bursts: Lower limit and scaling exponent

Plastic flow of micro-samples proceeds in an intermittent displacement bursts, showing a scale-free power-law distribution. Using maximum likelihood estimator and the Kolmogorov-Smirnov statistic, we investigate the statistics of displacement bursts such as lower limit and scaling exponent, for selected micro-samples from previous researches. The results of lower limit indicate that all the crystals considered share a common lower limit, the magnitude of which is found to be comparable to the largest burst size governed by short-range interactions (i.e., junctions). Additionally, the calculated results of the scaling exponents challenge those observed in many previous studies where other statistical techniques are employed. We demonstrate that our results are consistently manifested in the experimental data.

Huge thick conglomerate movement induced by full thick longwall mining huge thick coal seam

A discrete elemental method was used to study the thickness of conglomerate layer in a full thick seam mining activities under the influence of the law, pointing out the thickness of the conglomerate at different seam mining, and during the destruction and instability of existing state of laws. At 21141 thick seam mining, the face toward the direction of separation between the thick layer of conglomerate rock and the next bit after reaching its maximum capacity due to pull from the bottom of the plastic zone, formed a stratified and hierarchical down collapse. The shape of caving area is a “triangular block”, the length of the plastic zone and face advancement from the linear fit between the height of the plastic zone and the advancing face is a quadratic function of distance, while the top layer of thick gravel layer is the overall bending subsidence trend. Tilting the direction of the face, a thick gob of collapsed conglomerate layer is formed in the coal gob entity on both sides of the thick conglomerate at the top of the overall fracture morphology performance, thus forming a mutual extrusion of articulated block structure. The instability, separation and balance of the thick conglomerate layer in the hinged block stope stress leads to abnormal occurrence of rock burst induced by face as the major factor in the accident. This research reveals the form of stress distribution in the destroyed layer of the thick conglomerate rock, analyzes the stope law of coupling for the pressure burst behavior law for the mining work face, and the choice of preventive measures to provide a theoretical basis and implementation.

Comparing ion conductance recordings of synthetic lipid bilayers with cell membranes containing TRP channels

In this article we compare electrical conductance events from single channel recordings of three TRP channel proteins (TRPA1, TRPM2 and TRPM8) expressed in human embryonic kidney cells with channel events recorded on synthetic lipid membranes close to melting transitions. Ion channels from the TRP family are involved in a variety of sensory processes including thermo- and mechano-reception. Synthetic lipid membranes close to phase transitions display channel-like events that respond to stimuli related to changes in intensive thermodynamic variables such as pressure and temperature. TRP channel activity is characterized by typical patterns of current events dependent on the type of protein expressed. Synthetic lipid bilayers show a wide spectrum of electrical phenomena that are considered typical for the activity of protein ion channels. We find unitary currents, burst behavior, flickering, multistep-conductances, and spikes behavior in both preparations. Moreover, we report conductances and lifetimes for lipid channels as described for protein channels. Non-linear and asymmetric current–voltage relationships are seen in both systems. Without further knowledge of the recording conditions, no easy decision can be made whether short current traces originate from a channel protein or from a pure lipid membrane.

Succinylated Pullulan Acetate Microspheres for Protein Delivery

【In order to develop new protein carrier replacing poly(DL-lactic acid-co-glycolic acid) (PLGA) microspheres, succinylated pullulan acetate (SPA) was investigated to fabricate a long term protein delivery carrier. SPA microspheres loaded with lysozyme (Lys) as a model protein drug were prepared by a water/oil/water (W/O/W) double emulsion method. An acidity test of SPA copolymers after hydrolysis was performed to estimate the change of protein stability during releasing proteins from the microspheres. There was no pH change of SPA copolymers, but pH of PLGA polymers after hydrolysis was significantly decreased to around pH 2, indicating that the long-term stability of proteins released from SPA microspheres can be guaranteed. Loading efficiency of proteins into SPA microspheres was three times higher than those into conventional PLGA microspheres, indication of inducing stronger charge interaction between proteins and succinyl groups in SPA microspheres. Although initial burst behaviors were monitored in Lys-loaded SPA microspheres due to relatively strong hydrophilic succinyl segments in SPA microspheres, initial burst issues would be circumvented if the ratio of charge density of succinyl moieties and hydrophobic acetate groups is harmonically controlled. Therefore, in this study, a new attempt of protein delivery system was made and functional SPA was successfully confirmed as a new protein carrier.】

The 2008 outburst of IGR J17473–2721: evidence for a disk corona?

The 2008 outburst of the atoll source IGR J17473--2721 was observed by INTEGRAL, RXTE and Swift. Tens of type-I X-ray bursts were found in this outburst. Joint observations provide sufficient data to look into the behavior of IGR J17473--2721 at the rising part of the outburst. We find that the joint energy spectra can be well fitted with a model composed of a blackbody and a cutoff power-law, with a cutoff energy decreasing from $ \sim$ 150 keV to $\sim$ 40 keV as the source leaves the quiescent state toward the low hard state. This fits into a scenario in which the corona is cooled by the soft X-rays along the outburst evolution, as observed in several other atoll sources. By using the flux measured in the 1.5--30 keV band of the type-I bursts during the outburst, we find that the linear relationship between the burst duration and the flux still holds for those bursts that occur at the decaying part of the low hard state, but with a different slope than the overall one that was estimated with the bursts happening in the whole extent of, and for the rest of the low hard state. The significance of such a dichotomy in the type-I X-ray bursts is $\sim$ 3 $\sigma$ under an F-test. Similar results are hinted at as well with the broader energy-band that was adopted recently. This dichotomy may be understood in a scenario where part of the accreting material forms a corona on the way of falling onto the surface of the neutron star during the decaying part of the low hard state. Based on the accretion rates of the preceding LHS, estimated from type-I X-ray bursts and from persistent emission, at least for IGR J17473-2721, most of the accretion material may fall on the neutron star (NS) surface in the LHS. Considering the burst behavior in the context of the outburst indicates a corona formed on top of the disk rather than on the NS surface.

Attentional Modulation of Firing Rate Varies with Burstiness across Putative Pyramidal Neurons in Macaque Visual Area V4

One of the most well established forms of attentional modulation is an increase in firing rate when attention is directed into the receptive field of a neuron. The degree of rate modulation, however, can vary considerably across individual neurons, especially among broad spiking neurons (putative pyramids). We asked whether this heterogeneity might be correlated with a neuronal response property that is used in intracellular recording studies to distinguish among distinct neuronal classes: the burstiness of the neuronal spike train. We first characterized the burst spiking behavior of visual area V4 neurons and found that this varies considerably across the population, but we did not find evidence for distinct classes of burst behavior. Burstiness did, however, vary more widely across the class of neurons that shows the greatest heterogeneity in attentional modulation, and within that class, burstiness helped account for differences in attentional modulation. Among these broad spiking neurons, rate modulation was primarily restricted to bursty neurons, which as a group showed a highly significant increase in firing rate with attention. Furthermore, every bursty broad spiking neuron whose firing rate was significantly modulated by attention exhibited an increase in firing rate. In contrast, non-bursty broad spiking neurons exhibited no net attentional modulation, and, although some individual neurons did show significant rate modulation, these were divided among neurons showing increases and decreases. These findings show that macaque area V4 shows a range of bursting behavior and that the heterogeneity of attentional modulation can be explained, in part, by variation in burstiness.

A simple integrative electrophysiological model of bursting GnRH neurons

In this paper a modular model of the GnRH neuron is presented. For the aim of simplicity, the currents corresponding to fast time scales and action potential generation are described by an impulsive system, while the slower currents and calcium dynamics are described by usual ordinary differential equations (ODEs). The model is able to reproduce the depolarizing afterpotentials, afterhyperpolarization, periodic bursting behavior and the corresponding calcium transients observed in the case of GnRH neurons.

Puzzling thermonuclear burst behaviour from the transient low-mass X-ray binary IGR J17473−2721

We investigate the thermonuclear bursting behaviour of IGR J17473-2721, an X-ray transient that in 2008 underwent a six month long outburst, starting (unusually) with an X-ray burst. We detected a total of 57 thermonuclear bursts throughout the outburst with AGILE, Swift, RXTE, and INTEGRAL. The wide range of inferred accretion rates (between <1% and about 20% of the Eddington accretion rate m-dot_Edd) spanned during the outburst allows us to study changes in the nuclear burning processes and to identify up to seven different phases. The burst rate increased gradually with the accretion rate until it dropped (at a persistent flux corresponding to about 15% of m-dot_Edd) a few days before the outburst peak, after which bursts were not detected for a month. As the persistent emission subsequently decreased, the bursting activity resumed with a much lower rate than during the outburst rise. This hysteresis may arise from the thermal effect of the accretion on the surface nuclear burning processes, and the timescale is roughly consistent with that expected for the neutron star crust thermal response. On the other hand, an undetected superburst, occurring within a data gap near the outburst peak, could have produced a similar quenching of burst activity.

Analysis of distinct short and prolonged components in rebound spiking of deep cerebellar nucleus neurons

Deep cerebellar nucleus (DCN) neurons show pronounced post-hyperpolarization rebound burst behavior, which may contribute significantly to responses to strong inhibitory inputs from cerebellar cortical Purkinje cells. Thus, rebound behavior could importantly shape the output from the cerebellum. We used whole-cell recordings in brain slices to characterize DCN rebound properties and their dependence on hyperpolarization duration and depth. We found that DCN rebounds showed distinct fast and prolonged components, with different stimulus dependence and different underlying currents. The initial depolarization leading into rebound spiking was carried by hyperpolarization-activated cyclic nucleotide-gated current, and variable expression of this current could lead to a control of rebound latency. The ensuing fast rebound burst was due to T-type calcium current, as previously described. It was highly variable between cells in strength, and could be expressed fully after short periods of hyperpolarization. In contrast, a subsequent prolonged rebound component required longer and deeper periods of hyperpolarization before it was fully established. We found using voltage-clamp and dynamic-clamp analyses that a slowly inactivating persistent sodium current fits the conductance underlying this prolonged rebound component, resulting in spike rate increases over several seconds. Overall, our results demonstrate that multiphasic DCN rebound properties could be elicited differentially by different levels of Purkinje cell activation, and thus create a rich repertoire of potential rebound dynamics in the cerebellar control of motor timing.

Tracking burst patterns in hippocampal cultures with high-density CMOS-MEAs

In this work, we investigate the spontaneous bursting behaviour expressed by in vitro hippocampal networks by using a high-resolution CMOS-based microelectrode array (MEA), featuring 4096 electrodes, inter-electrode spacing of 21 µm and temporal resolution of 130 µs. In particular, we report an original development of an adapted analysis method enabling us to investigate spatial and temporal patterns of activity and the interplay between successive network bursts (NBs). We first defined and detected NBs, and then, we analysed the spatial and temporal behaviour of these events with an algorithm based on the centre of activity trajectory. We further refined the analysis by using a technique derived from statistical mechanics, capable of distinguishing the two main phases of NBs, i.e. (i) a propagating and (ii) a reverberating phase, and by classifying the trajectory patterns. Finally, this methodology was applied to signal representations based on spike detection, i.e. the instantaneous firing rate, and directly based on voltage-coded raw data, i.e. activity movies. Results highlight the potentialities of this approach to investigate fundamental issues on spontaneous neuronal dynamics and suggest the hypothesis that neurons operate in a sort of ‘team’ to the perpetuation of the transmission of the same information.

Evaluation of succinylated pullulan for long-term protein delivery in poly(lactide-co-glycolide) microspheres

Two types of pullulan with different succinylations were synthesized for an evaluation as additives for long-term protein delivery in poly(lactide-co-glycolide) microspheres (PLGA MS). Negatively charged succinylated pullulan (SP) forms an ionic complex with cationic protein (lysozyme; Lys) via an ionic interaction. SP2 (2 succinyl groups per 10 glucose units in pullulan) constructed a better nano-size complex with lysozyme (Lys) in distilled water (DW) than SP1 (1 succinyl group per 10 glucose units in pullulan). To assess the long-term delivery capability, PLGA MS complexes with different Lys:SP2 ratios (1:1 (LMS 1), 1:2 (LMS 2) and 1:3 (LMS 3), as wt% of Lys:SP2) were prepared with water in oil in water (W/O/W). The complex loaded PLGA MS showed a higher loading efficiency and a lower insoluble Lys content than PLGA without SP (LMS 0), indicating that SP helps stabilize Lys at the organic/water (O/W) interface. In evaluating the release pattern of Lys, LMS 1, 2, and 3 all demonstrated a low initial burst and complete release behavior (reaching almost 100% after 27 days), whereas the total amount of Lys released from LMS 0 did not reach 80% during the same time period. During a 14-day release test, the stability of Lys was confirmed by RP-HPLC. In the case of LMS 0, an unexpected peak (retention time 9.2 min) was created, which was not observed in LMS 1, 2, and 3. This suggests that SP suppresses the denaturation of Lys in PLGA MS. These results show that SP, as an additive in PLGA MS, has potential for the long-term delivery of therapeutic proteins. Open image in new window

XTE J1701–462 AND ITS IMPLICATIONS FOR THE NATURE OF SUBCLASSES IN LOW-MAGNETIC-FIELD NEUTRON STAR LOW-MASS X-RAY BINARIES

We report on an analysis of RXTE data of the transient neutron star low-mass X-ray binary (NS-LMXB) XTE J1701-462, obtained during its 2006-2007 outburst. The X-ray properties of the source changed between those of various types of NS-LMXB subclasses. At high luminosities the source switched between two types of Z source behavior and at low luminosities we observed a transition from Z source to atoll source behavior. These transitions between subclasses primarily manifest themselves as changes in the shapes of the tracks in X-ray color-color and hardness-intensity diagrams, but they are accompanied by changes in the kHz quasi-periodic oscillations, broad-band variability, burst behavior, and/or X-ray spectra. We find that the low-energy X-ray flux is a good parameter to track the gradual evolution of the tracks in color-color and hardness-intensity diagrams, allowing us to resolve the evolution of the source in greater detail than before and relate the observed properties to other NS-LMXBs. We further find that during the transition from Z to atoll, characteristic behavior known as the atoll upper banana can equivalently be described as the final stage of a weakening Z source flaring branch, thereby blurring the line between the two subclasses. Our findings strongly suggest that the wide variety in behavior observed in NS-LXMBs with different luminosities can be linked through changes in a single variable parameter, namely the mass accretion rate, without the need for additional differences in the neutron star parameters or viewing angle. We briefly discuss the implications of our findings for the spectral changes observed in NS LMXBs and suggest that, contrary to what is often assumed, the position along the color-color tracks of Z sources is not determined by the instantaneous mass accretion rate.

Computational modeling of the external tufted cell of the mammalian olfactory bulb

We explore the model’s parameter space using detailed parameter sweeps and Latin hypercube sampling, demarcating regions of bursting, tonic, and excitable behavior. To study the sensitivity of various functional characteristics to changes in parameter values, we employ specialized smooth optimization methods for bursting neural models [8]. We find that the half-activation voltages for ICaT and INaP are most critical for control of interburst period and duty cycle. We also investigate the phase response properties of the ET cell model and its responses to periodic input.

What ignites on the neutron star of 4U 0614+091?

[abridged] The LMXB 4U 0614+091 is a source of sporadic thermonuclear (type I) X-ray bursts. We find bursts with a wide variety of characteristics in serendipitous wide-field X-ray observations by EURECA/WATCH, RXTE/ASM, BeppoSAX/WFC, HETE-2/FREGATE, INTEGRAL/IBIS/ISGRI, and Swift/BAT, as well as pointed observations by RXTE/PCA and HEXTE. Most of them reach a peak flux of ~15 Crab, but a few only reach a peak flux below a Crab. One of the bursts shows a very strong photospheric radius-expansion phase. This allows us to evaluate the distance to the source: 3.2 kpc. The burst durations are between 10 sec to 5 min. However, after one of the intermediate-duration bursts, a faint tail is seen to at least ~2.4 hours after the start of the burst. One very long burst lasted for several hours. This superburst candidate was followed by a normal type-I burst only 19 days later. This is, to our knowledge, the shortest burst-quench time among the superbursters. A superburst in this system is difficult to reconcile if it accretes at ~1% L_Edd. The intermediate-duration bursts occurred when 4U 0614+091's persistent emission was lowest and calm, and when bursts were infrequent (on average one every month to 3 months). The average burst rate increased significantly after this period. The maximum average burst recurrence rate is once every week to 2 weeks. The burst behaviour may be partly understood if there is at least an appreciable amount of helium present in the accreted material from the donor star. If the system is an ultra-compact X-ray binary with a CO white-dwarf donor, as has been suggested, this is unexpected. If the bursts are powered by helium, we find that the energy production per accumulated mass is about 2.5 times less than expected for pure helium matter.

Synthesis and Drug Delivery Property of Calcium Phosphate Cement with Special Crystal Morphology

In this work, the drug‐release behavior was achieved by controlling the hydration crystal morphology formed during the setting reaction of cement. Two kinds of calcium phosphate cement (CPC) matrix with different and typical crystal morphology were prepared, and the cumulative percentage of gentamicin sulfate (GS) released from the hydrated bone cements was characterized in vitro. The relation between the cumulative percentage and the releasing time showed that both systems exhibited a reasonable low initial GS burst (about 20% and 30% for CPC‐1 and CPC‐2 in about 4 days, respectively) and sustained release behavior with different drug‐release rates. CPC‐1 and CPC‐2 showed a different drug‐releasing ratio after 30 days: 40% and 80%, respectively.