Class Of Bursts Research Articles

A comparative study of outflow structures of two classes of gamma-ray bursts

ABSTRACT The outflow structures of gamma-ray bursts (GRBs) can provide insights into the origins and radiation mechanisms of these cosmic explosions. We systematically study the GRB outflow structures by modelling their afterglow light curves and check if the structures of long gamma-ray bursts (LGRBs) and short gamma-ray bursts (SGRBs) are different. The sample consists of Swift-XRT afterglows with sufficient coverage and known redshift, which includes 195 well-fit LGRBs and 13 well-fit SGRBs. The model we use is a two-parameter ‘boosted fireball’ model, which consists of a family of outflows, with shapes varying smoothly from a quasi-spherical outflow to a highly collimated jet. We use the jetfit package to fit afterglow light curves and obtain the jet parameters. We find that there are no statistical differences in the distributions of jet parameters between LGRBs and SGRBs by performing K–S test and 74 per cent of the ratios of the observer angle to jet opening angle are in the range of 0.2 to 1. Our analysis indicates that the majority of GRB afterglows are viewed off-axis and there has no statistical difference between LGRBs and SGRBs. We also find that both the LGRBs and SGRBs exhibit two similar correlations: the jet opening angle is positively correlated with the observer angle, with the correlation coefficient 0.61 for LGRBs and 0.63 for SGRBs; the circumburst density is inversely correlated with the explosion energy with the correlation coefficient −0.89 for LGRBs and −0.69 for SGRBs. Our results suggest that the outflow structures are similar for the LGRBs and SGRBs.

The Accretion History of EX Lup: A Century of Bursts, Outbursts, and Quiescence

EX Lup is the archetype for the class of young stars that undergoes repeated accretion outbursts of ∼5 mag at optical wavelengths that last for months. Despite extensive monitoring that dates back 130 yr, the accretion history of EX Lup remains mostly qualitative and has large uncertainties. We assess historical accretion rates of EX Lup by applying correlations between optical brightness and accretion, developed on multi-band magnitude photometry of the ∼2 mag optical burst in 2022. Two distinct classes of bursts occur: major outbursts (ΔV ∼ 5 mag) have year-long durations, are rare, reach accretion rates of M ⊙ yr−1 at peak, and have a total accreted mass of around 0.1 Earth mass. The characteristic bursts (ΔV ∼ 2 mag) have durations of ∼2–3 months, are more common, reach accretion rates of M ⊙ yr−1 at peak, and have a total accreted mass of around 10−3 Earth masses. The distribution of total accreted mass in the full set of bursts is poorly described by a power law, which suggests different driving causes behind the major outburst and characteristic bursts. The total mass accreted during two classes of bursts is around 2 times the masses accreted during quiescence. Our analysis of the light curves reveals a color-dependent time lag in the 2022 post-burst light curve, attributed to the presence of both hot and cool spots on the stellar surface.

A guide towards optimal detection of transient oscillatory bursts with unknown parameters

Objectives. Recent event-based analyses of transient neural activities have characterized the oscillatory bursts as a neural signature that bridges dynamic neural states to cognition and behaviors. Following this insight, our study aimed to (1) compare the efficacy of common burst detection algorithms under varying signal-to-noise ratios and event durations using synthetic signals and (2) establish a strategic guideline for selecting the optimal algorithm for real datasets with undefined properties. Approach. We tested the robustness of burst detection algorithms using a simulation dataset comprising bursts of multiple frequencies. To systematically assess their performance, we used a metric called ‘detection confidence’, quantifying classification accuracy and temporal precision in a balanced manner. Given that burst properties in empirical data are often unknown in advance, we then proposed a selection rule to identify an optimal algorithm for a given dataset and validated its application on local field potentials of basolateral amygdala recorded from male mice (n=8) exposed to a natural threat. Main Results. Our simulation-based evaluation demonstrated that burst detection is contingent upon event duration, whereas accurately pinpointing burst onsets is more susceptible to noise level. For real data, the algorithm chosen based on the selection rule exhibited superior detection and temporal accuracy, although its statistical significance differed across frequency bands. Notably, the algorithm chosen by human visual screening differed from the one recommended by the rule, implying a potential misalignment between human priors and mathematical assumptions of the algorithms. Significance. Therefore, our findings underscore that the precise detection of transient bursts is fundamentally influenced by the chosen algorithm. The proposed algorithm-selection rule suggests a potentially viable solution, while also emphasizing the inherent limitations originating from algorithmic design and volatile performances across datasets. Consequently, this study cautions against relying solely on heuristic-based approaches, advocating for a careful algorithm selection in burst detection studies.

Quantitative assessment of burst suppression as a predictor of seizure recurrence in refractory status epilepticus

ObjectiveTo determine whether quantitative EEG analysis of burst suppression can predict seizure recurrence in patients with refractory status epilepticus (RSE) being treated with anesthetic doses of continuous IV antiseizure medications (cIVASM). MethodsQuantitative assessment of burst suppression (including epileptiform discharges [EDs] and evolution) in 31 occasions (from 27 patients), and correlation with seizure recurrence up to 48 hours post sedative wean. ResultsOccasions resulting in seizure recurrence (vs. no seizure recurrence) had lower burst (8.4 vs. 10.6 µV) and interburst interval (IBI) (4.2 vs. 4.8 µV) average amplitude, duration (bursts 2.8 vs. 3.6 s: IBIs 3.6 vs. 4.4 s); and burst total power (0.4 vs. 0.7 µV2). Bursts (0.86 vs. 0.60) and IBIs (0.28 vs. 0.07) with EDs, higher number of EDs within bursts (mean 2.1 vs. 1.4) and IBIs (0.6 vs. 0.2), and positive evolution measures all predicted seizure recurrence, although EDs had the greatest adjusted odds ratio on multivariate analysis. ConclusionsFor patients in burst suppression, successful wean of cIVASM was not determined by classical burst suppression measures, but instead how “epileptiform” bursts and IBIs were, as determined by EDs in both bursts and IBIs and surrogates for evolution within bursts. SignificanceIf confirmed, these objective measures could be used during clinical care to help determine when to wean cIVASM in patients with RSE.

Classification of BATSE, Swift, and Fermi Gamma-Ray Bursts from Prompt Emission Alone

Although it is generally assumed that there are two dominant classes of gamma-ray bursts (GRBs) with different typical durations, it has been difficult to classify GRBs unambiguously as short or long from summary properties such as duration, spectral hardness, and spectral lag. Recent work used t-distributed stochastic neighborhood embedding (t-SNE), a machine-learning algorithm for dimensionality reduction, to classify all Swift GRBs as short or long. Here, the method is expanded, using two algorithms, t-SNE and UMAP, to produce embeddings that are used to provide a classification for 1911 BATSE bursts, 1321 Swift bursts, and 2294 Fermi bursts for which both spectra and metadata are available. Although the embeddings appear to produce a clear separation of each catalog into short and long bursts, a resampling-based approach is used to show that a small fraction of bursts cannot be robustly classified. Further, three of the 304 bursts observed by both Swift and Fermi have robust but conflicting classifications. A likely interpretation is that in addition to the two predominant classes of GRBs, there are additional, uncommon types of bursts which may require multiwavelength observations in order to separate them from more typical short and long GRBs.

Distribution of gamma-ray bursts on the T90–HR plane and their classification revisited

ABSTRACT Using four mixed bivariate distributions (Normal distribution, Skew-Normal distribution, Student distribution, Skew-Student distribution) and bootstrap re-sampling analysis. We analyse the samples of CGRO/BATSE, Swift/BAT, and Fermi/GBM gamma-ray bursts in detail on the T90–HR (Hardness Ratio) plane. The Bayesian information criterion is used to judge the goodness of fit for each sample, comprehensively. It is found that all the three samples show a symmetric (either Normal or Student) distribution. It is also found that the existence of three classes of gamma-ray bursts is preferred by the three samples, but the strength of this preference varies with the sample size: when the sample size of the data set is larger, the preference of three classes scheme becomes weaker. Therefore, the appearance of an intermediate class may be caused by a small sample size and the possibility that there are only two classes of gamma-ray bursts still cannot be expelled yet. A further bootstrap re-sampling analysis also confirms this result.

VLBI observations of GRB 201015A, a relatively faint GRB with a hint of very high-energy gamma-ray emission

Context. A total of four long-duration gamma-ray bursts (GRBs) have been confirmed at very high-energy (≥100GeV) with high significance, and any possible peculiarities of these bursts will become clearer as the number of detected events increases. Multi-wavelength follow-up campaigns are required to extract information on the physical conditions within the jets that lead to the very high-energy counterpart, hence they are crucial to reveal the properties of this class of bursts. Aims. GRB 201015A is a long-duration GRB detected using the MAGIC telescopes from ~40 s after the burst. If confirmed, this would be the fifth and least luminous GRB ever detected at these energies. The goal of this work is to constrain the global and microphysical parameters of its afterglow phase, and to discuss the main properties of this burst in a broader context. Methods. Since the radio band, together with frequent optical and X-ray observations, proved to be a fundamental tool for overcoming the degeneracy in the afterglow modelling, we performed a radio follow-up of GRB 201015A over 12 different epochs, from 1.4 days (2020 October 17) to 117 days (2021 February 9) post-burst, with the Karl G. Jansky Very Large Array, e-MERLIN, and the European VLBI Network. We include optical and X-ray observations, performed respectively with the Multiple Mirror Telescope and the Chandra X-ray Observatory, together with publicly available data, in order to build multi-wavelength light curves and to compare them with the standard fireball model. Results. We detected a point-like transient, consistent with the position of GRB 201015A until 23 and 47 days post-burst at 1.5 and 5 GHz, respectively. No emission was detected in subsequent radio observations. The source was also detected in optical (1.4 and 2.2 days post-burst) and in X-ray (8.4 and 13.6 days post-burst) observations. Conclusions. The multi-wavelength afterglow light curves can be explained with the standard model for a GRB seen on-axis, which expands and decelerates into a medium with a homogeneous density. A circumburst medium with a wind-like profile is disfavoured. Notwithstanding the high resolution provided by the VLBI, we could not pinpoint any expansion or centroid displacement of the outflow. If the GRB is seen at the viewing angle θ that maximises the apparent velocity βapp (i.e. θ ~ βapp-1), we estimate that the Lorentz factor for the possible proper motion is Гα ≤ 40 in right ascension and Гδ ≤ 61 in declination. On the other hand, if the GRB is seen on-axis, the size of the afterglow is ≤5pc and ≤16pc at 25 and 47 days. Finally, the early peak in the optical light curve suggests the presence of a reverse shock component before 0.01 days from the burst.

Two Classes of Gamma-ray Bursts Distinguished within the First Second of Their Prompt Emission

Studies of Gamma-Ray Burst (GRB) properties, such as duration and spectral hardness, have found evidence for additional classes, beyond the short/hard and long/soft prototypes, using model-dependent methods. In this paper, a model-independent approach was used to analyse the gamma-ray light curves of large samples of GRBs detected by BATSE, Swift/BAT and Fermi/GBM. All the features were extracted from the GRB time profiles in four energy bands using the Stationary Wavelet Transform and Principal Component Analysis. t-distributed Stochastic Neighbourhood Embedding (t-SNE) visualisation of the features revealed two distinct groups of Swift/BAT bursts using the T100 interval with 64 ms resolution data. When the same analysis was applied to 4 ms resolution data, two groups were seen to emerge within the first second (T1) post-trigger. These two groups primarily consisted of short/hard (Group 1) and long/soft (Group 2) bursts, and were 95% consistent with the groups identified using the T100 64 ms resolution data. Kilonova candidates, arising from compact object mergers, were found to belong to Group 1, while those events with associated supernovae fell into Group 2. Differences in cumulative counts between the two groups in the first second, and in the minimum variability timescale, identifiable only with the 4 ms resolution data, may account for this result. Short GRBs have particular significance for multi-messenger science as a distinctive EM signature of a binary merger, which may be discovered by its gravitational wave emissions. Incorporating the T1 interval into classification algorithms may support the rapid classification of GRBs, allowing for an improved prioritisation of targets for follow-up observations.

Cervical and ocular vestibular evoked myogenic potential: A comparison of narrowband chirp, broadband chirp, tone burst and click stimulation

Objectives To compare the response rate and response parameters of cervical and ocular vestibular evoked myogenic potentials (c&oVEMP) elicited by narrowband (NB) and broadband (BB) CE-Chirp, with the more classical tone burst (TB) and click VEMPs. Design The response rate, latency, amplitude and asymmetry ratio of c&oVEMPs elicited by 95 dB nHL air conducted (AC) 500 Hz NB CE-chirp, BB CE-chirp, 500 Hz TB and click stimuli were recorded bilaterally. Study sample 20 male and 38 female participants (19–39 years). Results For the cVEMP, the highest response rate was found for NB chirp (100%), followed by TB (91%), BB chirp (87%) and finally click (85%). A similar order was seen for oVEMP with percentages of 100%; 57%, 57%, and 43%. The 500 Hz NB CE-Chirp elicited significantly shorter cVEMP P1 and N1 latencies and significantly larger c&oVEMP amplitudes compared to all other stimuli. BB CE-Chirp elicited significantly shorter c&oVEMP P1 and N1 latencies with smaller amplitudes compared to TB. Asymmetry ratios were not statistically significant for all comparisons. Conclusion The 500 Hz NB CE-chirp provides the highest response rates, shorter latencies and larger amplitudes, and therefore seem a promising stimulus for reliably measuring c&oVEMPs in clinical practice.

Shock-wave Radio Probing of Solar Wind Sources in Coronal Magnetic Fields

Abstract The space weather effects in the near-Earth environment as well as in atmospheres of other terrestrial planets arise by corpuscular radiation from the Sun, known as the solar wind. The solar magnetic fields govern the solar corona structure. Magnetic-field strength values in the solar wind sources—key information for modeling and forecasting the space weather climate—are derived from various solar space- and ground-based observations, but so far not accounting for specific types of radio bursts. These are “fractured” type II radio bursts attributed to collisions of shock waves with coronal structures emitting the solar wind. Here, we report on radio observations of two “fractured” type II bursts to demonstrate a novel tool for probing of magnetic-field variations in the solar wind sources. These results have a direct impact on interpretations of this class of bursts and contribute to the current studies of the solar wind emitters.

Burst control: Synaptic conditions for burst generation in cortical layer 5 pyramidal neurons.

The output of neocortical layer 5 pyramidal cells (L5PCs) is expressed by a train of single spikes with intermittent bursts of multiple spikes at high frequencies. The bursts are the result of nonlinear dendritic properties, including Na+, Ca2+, and NMDA spikes, that interact with the ~10,000 synapses impinging on the neuron’s dendrites. Output spike bursts are thought to implement key dendritic computations, such as coincidence detection of bottom-up inputs (arriving mostly at the basal tree) and top-down inputs (arriving mostly at the apical tree). In this study we used a detailed nonlinear model of L5PC receiving excitatory and inhibitory synaptic inputs to explore the conditions for generating bursts and for modulating their properties. We established the excitatory input conditions on the basal versus the apical tree that favor burst and show that there are two distinct types of bursts. Bursts consisting of 3 or more spikes firing at < 200 Hz, which are generated by stronger excitatory input to the basal versus the apical tree, and bursts of ~2-spikes at ~250 Hz, generated by prominent apical tuft excitation. Localized and well-timed dendritic inhibition on the apical tree differentially modulates Na+, Ca2+, and NMDA spikes and, consequently, finely controls the burst output. Finally, we explored the implications of different burst classes and respective dendritic inhibition for regulating synaptic plasticity.

Are there radio-loud and radio-quiet gamma-ray bursts?

ABSTRACT The potential existence of two separate classes of Long-duration Gamma-Ray Bursts (LGRBs) with and without radio afterglow emission, corresponding to radio-bright/loud and radio-dark/quiet populations, has been recently argued and favoured in the GRB literature. The radio-quiet LGRBs have been found to have, on average, lower total isotropic gamma-ray emissions (Eiso) and shorter intrinsic prompt gamma-ray durations (e.g. T90z). In addition, a redshift −T90z anticorrelation has been discovered among the radio-loud LGRBs, which is reportedly missing in the radio-quiet class. Here, we discuss the significance of the differences between the energetics and temporal properties of the two proposed classes of radio-loud and radio-quiet LGRBs. We show that much of the proposed evidence in support of the two distinct radio populations of LGRBs can be explained away in terms of selection effects and sample incompleteness. Our arguments are based on the recent discovery of the relatively strong, highly significant positive correlation between the total isotropic emission (Eiso) and the intrinsic prompt duration (T90z) that is present in both populations of short-hard and long-soft GRBs, predicted, quantified, and reported for the first time by Shahmoradi (2013a;2013b) and Shahmoradi &amp; Nemiroff (2015).

Characteristic for long GRBs with high energy component presence, which not required cosmological corrections

Several thousands of gamma-ray bursts were observed by various experiments. During several GRBs very high-energy photons were detected both in space and ground-based experiments (up to some tens of GeV and up to some TeV, respectively). Usually 2 classes of bursts are considered: short and long GRBs separated by t90~2s. Because of several hundreds of GRBs located at high redshift, its sources’ origins nature concluding as cosmological. Therefore correction to cosmological dilation of GRBs t90 should be considered during any analysis of bursts duration. Firstly very high-energy component was observed during GRB 970417a: 18 photons with energy ~650 GeV were registered by Milagrito within t90 interval of this burst. Now several tens of GRBs reveal activity in energy bands up to some tens of GeV and up to some TeV accordingly data of space and ground-based experiments correspondingly. Unfortunately redshift is unknown approximately for half of GRBs with high energy component presence. Here we introduce new parameter Rt is ratio of maximum energy photon arrival time to burst duration and it not required cosmological correction. At least 2 groups of long GRBs could be separated using parameter Rt: for 25% events highest energy gammas detected within t 90 interval, but for other 75% of bursts it registered more than 10 sec. later than one. Moreover, preliminary results of analysis allow concluding 2 subtypes of second group GRBs. For one μ-quantum with maximum energy arrived within t90. For other such photon was registered later than t90. Therefore, the results of preliminary analyses allow conclude long GRBs population inhomogeneity.

Multivariate Analysis of BATSE Gamma-Ray Burst Properties Using Skewed Distributions

Abstract The number of classes of gamma-ray bursts (GRBs), besides the well-established short and long ones, remains a debatable issue. It was already shown, however, that when invoking skewed distributions, the and spaces are adequately modeled with mixtures of only two such components, implying two GRB types. Herein, a comprehensive multivariate analysis of several multidimensional parameter spaces is conducted for the BATSE sample of GRBs, with the usage of skewed distributions. It is found that the number of extracted components varies between the examined parameter sets, and ranges from 2 to 4, with higher-dimensional spaces allowing for more classes. Monte Carlo testing implies that these additional components are likely to be artifacts owing to the finiteness of the data and to be a result of examining a particular realization of the data as a random sample, resulting in spurious identifications.

Classification of gamma-ray bursts observed with Konus-Wind

We present the analysis of duration and spectral-hardness distributions of ∼ 3000 gamma-ray bursts (GRBs) detected by Konus-Wind (KW) between November 1994 and early February 2019. We analyse burst T50 and T90 durations (the time intervals which contain the central 50% to 90% of the total burst count fluence, respectively) and argue that T50 is more robust duration measure than T90. Using a two log-normal component fit to the T50 distribution we pick the boundary between the overlapping classes of short-duration and long-duration bursts to be at T50 = 0.7 s, which implies the fraction of short GRBs (T50 < 0.7 s) to be ∼ 17%. Using Gaussian mixture model fits we show that hardness-duration distribution can be well described by three Gaussian components, with two components corresponding to short/hard and long/soft GRB population, and the third component covering the softest GRBs with intermediate durations. This classification suggests that ∼ 14% KW GRBs are from short/hard population.Finally we discuss a possibility to discriminate between physically distinct Type I and Type II GRBs with the help of hardness-duration distribution.

Selectively Oxidized Cellulose with Adjustable Molecular Weight for Controlled Release of Platinum Anticancer Drugs.

The synthesis of selectively oxidized cellulose, 2,3-dicarboxycellulose (DCC), is optimized for preparation of highly oxidized material for biological applications, which includes control over the molecular weight of the product during its synthesis. Conjugates of DCC and cisplatin simultaneously offer a very high drug binding efficiency (>90%) and drug loading capacity (up to 50 wt %), while retaining good aqueous solubility. The adjustable molecular weight of the DCC together with variances in drug feeding ratio allows to optimize cisplatin release profiles from delayed (<2% of cisplatin released during 6 h) to classical burst release with more than 60% of cisplatin released after 24 h. The release rates are also pH-dependent (up to 2 times faster release at pH 5.5 than at pH 7.4), which allows to exploit the acidic nature of tumor microenvironment. Extensive in vitro studies were performed on eight different cell lines for two cisplatin-DCC conjugates with different release profiles. In comparison with free cisplatin, both cisplatin-DCC conjugates demonstrated considerably lower cytotoxicity toward healthy cells. Conjugates with burst release profiles were found more effective against prostate cell lines, while DCC conjugates with slower release were more cytotoxic against ovarian and lung carcinoma cell lines. In vivo studies indicated a significantly longer survival rate, a reduction in tumor volume, and a higher accumulation of platinum in tumors of mice treated with the cisplatin-DCC conjugate in comparison to those treated by free cisplatin.

Analysis of the Duration–Hardness Ratio Plane of Gamma-Ray Bursts Using Skewed Distributions

Abstract The two widely accepted classes of gamma-ray bursts (GRBs), short and long, are with confidence ascribed to mergers of compact objects and collapse of massive stars, respectively. A third, intermediate/soft class, remains putative. Its existence was claimed based on univariate and bivariate analyses of GRB observables modeled with Gaussian distributions. This, however, may not be the appropriate approach, as it has already been shown that the univariate distributions of durations are better described by mixtures of two skewed components rather than three Gaussian ones. This paper investigates whether data in the duration–hardness ratio plane is better modeled by mixtures of skewed bivariate distributions than by normal ones. The archival data set of the Compton Gamma-Ray Observatory/BATSE and Fermi/Gamma-ray Burst Monitor data from the most recent catalog release are examined. The preferred model is chosen based on two information criteria, Akaike and Bayesian. It is found that the best description is given by a two-component mixture of skewed Student-t distributions, which outperforms any other model considered. This implies that the distribution of the studied parameters is intrinsically skewed, introducing spurious Gaussian components, and hence the third class is unlikely to be a real phenomenon. Its existence, based on statistical inference, is therefore rejected as unnecessary to explain the observations.

Occurrence of the specific long spike burst pattern in the ovine proximal gallbladder as an indication of myoelectric regional variability.

The myoelectrical activity of the ovine gallbladder has not been fully recognised. Five rams were fitted with six small intestinal and three gallbladder electrodes and a strain gauge force transducer was mounted near the gallbladder fundic electrode. In two series of successive experiments, the electromyographical and mechanical recordings were recorded over a period of 5–7 hours. The occurrence of the slow waves in the small bowel was regular, unlike those in the gallbladder. In the gallbladder infundibulum, the specific pattern, called the long spike burst pattern (LSBP), was observed. It comprised usually one or two parts of prolonged duration. The first part resembled the classical (short lasting) spike burst in the small bowel, and its amplitude was lower than that of the second part. The spike burst frequency of the second part was 2–3 times lower than that of the first part. During phase 1-like and phase 2a-like activities, the intensity of the gallbladder LSBP was reduced while enhanced after feeding. In fasted rams, the duration of a specific pattern, observed in the gallbladder infundibulum, was longer than in non-fasted animals and its amplitude was low. Similar events were recorded in the gallbladder corpus, but the specific pattern was shorter and irregular. In the gallbladder fundus, mostly irregular short spike bursts were recorded. It is concluded that in sheep, specific types of the long-lasting groups of spikes occur in the upper gallbladder areas exhibiting myoelectrical regional variability. The character of an LSBP depends on feeding conditions.

IPTF 16asu: A Luminous, Rapidly Evolving, and High-velocity Supernova

Abstract Wide-field surveys are discovering a growing number of rare transients whose physical origin is not yet well understood. Here we present optical and UV data and analysis of intermediate Palomar Transient Factory (iPTF) 16asu, a luminous, rapidly evolving, high-velocity, stripped-envelope supernova (SN). With a rest-frame rise time of just four days and a peak absolute magnitude of mag, the light curve of iPTF 16asu is faster and more luminous than that of previous rapid transients. The spectra of iPTF 16asu show a featureless blue continuum near peak that develops into an SN Ic-BL spectrum on the decline. We show that while the late-time light curve could plausibly be powered by 56Ni decay, the early emission requires a different energy source. Nondetections in the X-ray and radio strongly constrain the energy coupled to relativistic ejecta to be at most comparable to the class of low-luminosity gamma-ray bursts (GRBs). We suggest that the early emission may have been powered by either a rapidly spinning-down magnetar or by shock breakout in an extended envelope of a very energetic explosion. In either scenario a central engine is required, making iPTF 16asu an intriguing transition object between superluminous SNe, SNe Ic-BL, and low-luminosity GRBs.

The specific long spike burst pattern indicates the presence of regional variability in the ovine gallbladder motor function

AbstractThe myoelectrical activity of ovine gallbladder is incompletely recognized. Accordingly, each of five rams was fitted with six small intestinal and three gallbladder electrodes. The strain gauge force transducer was also mounted near the gallbladder fundic electrode. In two series of chronic experiments the electromyographical and mechanical recordings were conducted during 5–7 h in fasted or non-fasted animals, with or without feeding. The occurrence of the slow waves in the small bowel was common, unlike those in the gallbladder. In the small bowel myoelectrical records both the migrating motility complex and minute rhythm pattern were observed regularly. In the gallbladder, both the migrating motility complex-like activity and the minute rhythm were also denoted in the same time as in the small bowel. In gallbladder infundibulum, and often also in the gallbladder corpus, the specific pattern, called the long spike burst pattern (LSBP) was observed. It comprised usually one or two parts of prolonged duration. The first part resembled the classical (short lasting) spike burst in the small bowel and its amplitude was lower than that of the second part. The spike burst frequency of the second part of the pattern was 2–3 times lower than that of the first part. During phase 1 – and phase 2a-like activity, the frequency of the gallbladder LSBP was reduced in fasted rams. The LSBP amplitude was relatively high and not further enhanced after feeding. In fasted rams, the duration of specific pattern, observed in gallbladder infundibulum, was longer than that in non-fasted animals and its amplitude was low. Similar events were recorded in the gallbladder corpus, but the LSBP was shorter and not regular. In the gallbladder fundus, mostly irregular short spike bursts were recorded. It is concluded that in sheep, specific types of the long-lasting groups of spikes occur in the upper gallbladder areas forming the specific pattern that indicates the presence of the regional variability of the gallbladder motor activity. The character of LSBP depends mostly on feeding conditions.