Burst Length Research Articles

Normative amplitude-integrated EEG measures in preterm infants.

ObjectiveAssessing qualitative patterns of amplitude integrated EEG (aEEG) maturation of preterm infants requires personnel with training in interpretation and an investment of time. Quantitative algorithms provide a method for rapidly and reproducibly assessing an aEEG recording independent of provider skill level. Although there are several qualitative and quantitative normative datasets in the literature, this study provides the broadest array of quantitative aEEG measures in a carefully selected and followed cohort of preterm infants with mild or no visible injury on term equivalent MRI and subsequently normal neurodevelopment at 2 and 7 years of age.Study DesignA two-channel aEEG recording was obtained on days 4,7,14, and 28 of life for infants born ≤30 weeks EGA. Measures of amplitude and continuity, spectral edge frequency, percentage of trace in interburst interval, interburst interval length, and frequency counts of smooth delta waves, delta brushes and theta bursts were obtained. MRI was obtained at term-equivalent age (TEA) and neurodevelopmental testing was conducted at 2 and 7 years of corrected age.ResultCorrelations were found between increasing post-menstrual age (PMA) and decreasing maximum amplitude (R=−0.23, p=0.05), increasing minimum amplitude (R=0.46, p=0.002), and increasing spectral edge frequency (R=0.78, p=4.17x10−14). Negative correlations were noted between increasing PMA and counts of smooth delta waves (R=−0.39, p=0.001), delta brushes (R=−0.37, p=0.003), and theta bursts (R=−0.61, p=5.66x10−8). Increasing PMA was also associated with a decreased amount of time spent in the interburst interval (R=−0.38, p=0.001) and a shorter length of the maximum IBI (R=−0.27, p=0.03).ConclusionThis analysis supports a strong correlation between quantitatively determined aEEG measures and PMA, in a cohort of preterm infants with normal TEA neuroimaging and neurodevelopmental outcomes at 7 years of age, which is both predictable and reproducible. These “normative” quantitative values support the pattern of maturation previously identified by qualitative analysis.

An energy-efficient video transport protocol for personal cloud-based computing

Recently, we are surrounded by a collection of heterogeneous computing devices such as desktop computers, laptops, smart phones, smart televisions, and tablet PCs. Each device is operated with its own host operating system, has its own internal architecture, and performs its independent tasks with its own applications and data. A common property amongst these devices, namely that of internet-connectivity, allows them to configure personal virtual cloud system by interconnecting each other through an intermediate switching device. The personal cloud service should provide a seamlessly unified computing environment across multiple devices with synchronized data and application programs. As such, it allows users to freely switch their workspace from one device to another while continuing the interaction with the available applications. In order to support video applications, the cloud system should provide seamless video synchronization among the multiple devices. However, we note that the current cloud services do not provide efficient data flow among devices. In this paper, we propose and develop a new reliable transport protocol to support video synchronization for the personal virtual cloud system. In order to cope with battery limitation of many mobile devices in personal virtual cloud system, the proposed protocol is designed to provide energy efficient video communications. Our simulation results show that the proposed protocol can reduce end users power consumption up to 25 % compared to the legacy TCP with given packet loss probabilities and the average length of error bursts.

Exploiting flow to control the in vitro spatiotemporal distribution of microbubble-seeded acoustic cavitation activity in ultrasound therapy

Focused ultrasound and microbubbles have been extensively used to generate therapeutic bioeffects. Despite encouraging in vivo results, there remains poor control of the magnitude and spatial distribution of these bioeffects due to the limited ability of conventional pulse shapes and sequences to control cavitation dynamics. Thus current techniques are restricted by an efficacy-safety trade-off. The primary aim of the present study was to incorporate the presence of flow in the design of new short pulse sequences, which can more uniformly distribute the cavitation activity. Microbubbles flowing (fluid velocity: 10 mm s−1) through a 300 μm tube were sonicated with a focused 0.5 MHz transducer while acoustic emissions were captured with an inserted focused 7.5 MHz passive cavitation detector. The two foci were co-axially aligned and their focal points were overlapped. Whereas conventional sequences are composed of a long burst (>10 000 cycles) emitted at a low burst repetition frequency (<10 Hz), we decomposed this burst into short pulses by adding intervals to facilitate inter-pulse microbubble movement. To evaluate how this sequence influenced cavitation distribution, we emitted short pulses (peak-rarefactional pressure (PRP): 40–366 kPa, pulse length (PL): 5–25 cycles) at high pulse repetition frequencies (PRF: 0.625–10 kHz) for a burst length of 100 ms. Increased cavitation persistence, implied by the duration of the microbubble acoustic emissions, was a measure of improved distribution due to the presence of flow. Sonication at lower acoustic pressures, longer pulse intervals and lower PLs improved the spatial distribution of cavitation. Furthermore, spectral analysis of the microbubble emissions revealed that the improvement at low pressures is due to persisting stable cavitation. In conclusion, new short-pulse sequences were shown to improve spatiotemporal control of acoustic cavitation dynamics during physiologically relevant flow. This could lead to adjustable distribution of the generated in vivo bioeffect and therefore efficient and safe treatment of a wide range of pathologies.

The significance of dynamical architecture for adaptive responses to mechanical loads during rhythmic behavior.

Many behaviors require reliably generating sequences of motor activity while adapting the activity to incoming sensory information. This process has often been conceptually explained as either fully dependent on sensory input (a chain reflex) or fully independent of sensory input (an idealized central pattern generator, or CPG), although the consensus of the field is that most neural pattern generators lie somewhere between these two extremes. Many mathematical models of neural pattern generators use limit cycles to generate the sequence of behaviors, but other models, such as a heteroclinic channel (an attracting chain of saddle points), have been suggested. To explore the range of intermediate behaviors between CPGs and chain reflexes, in this paper we describe a nominal model of swallowing in Aplysia californica. Depending upon the value of a single parameter, the model can transition from a generic limit cycle regime to a heteroclinic regime (where the trajectory slows as it passes near saddle points). We then study the behavior of the system in these two regimes and compare the behavior of the models with behavior recorded in the animal in vivo and in vitro. We show that while both pattern generators can generate similar behavior, the stable heteroclinic channel can better respond to changes in sensory input induced by load, and that the response matches the changes seen when a load is added in vivo. We then show that the underlying stable heteroclinic channel architecture exhibits dramatic slowing of activity when sensory and endogenous input is reduced, and show that similar slowing with removal of proprioception is seen in vitro. Finally, we show that the distributions of burst lengths seen in vivo are better matched by the distribution expected from a system operating in the heteroclinic regime than that expected from a generic limit cycle. These observations suggest that generic limit cycle models may fail to capture key aspects of Aplysia feeding behavior, and that alternative architectures such as heteroclinic channels may provide better descriptions.

Modeling and Analysis of Frame-Level Forward Error Correction for MPEG Video over Burst-Loss Channels

Forward error correction (FEC) is a common error control technique to improve the quality of video streaming over lossy channels. To optimize the data recovery performance, frame-level FEC schemes have been proposed for streaming video to maximize playable frame rate (PFR) within transmission rate constraint on a random binary symmetric channel (BSC). However, burst loss is a commonplace in current Internet architecture, and the FEC efficacy c an be degraded since the burst data losses easily exceed the error correction capacity of FEC. Accordingly, an estimated video quality model over burst loss channels is proposed in this paper to evaluate the impact of burst loss for FEC-based video applications. In addition to th e model analysis, the simulation experiments on the NS-2 network simulator are conducted at a given estimate of the packet loss probability and average burst length. The results suggest a useful reference in designing the FEC scheme for video applications, and as the video coding and channel parameters are given, the proposed model can provide the optimal FEC solution to achieve a better reconstructed video quality than the FEC model based on a random BSC channel.

On a Mathematical Model for Low-Rate Shrew DDoS

The shrew distributed denial of service (DDoS) attack is very detrimental for many applications, since it can throttle TCP flows to a small fraction of their ideal rate at very low attack cost. Earlier works mainly focused on empirical studies of defending against the shrew DDoS, and very few of them provided analytic results about the attack itself. In this paper, we propose a mathematical model for estimating attack effect of this stealthy type of DDoS. By originally capturing the adjustment behaviors of victim TCPs congestion window, our model can comprehensively evaluate the combined impact of attack pattern (i.e., how the attack is configured) and network environment on attack effect (the existing models failed to consider the impact of network environment). Henceforth, our model has higher accuracy over a wider range of network environments. The relative error of our model remains around 10% for most attack patterns and network environments, whereas the relative error of the benchmark model in previous works has a mean value of 69.57%, and it could be more than 180% in some cases. More importantly, our model reveals some novel properties of the shrew attack from the interaction between attack pattern and network environment, such as the minimum cost formula to launch a successful attack, and the maximum effect formula of a shrew attack. With them, we are able to find out how to adaptively tune the attack parameters (e.g., the DoS burst length) to improve its attack effect in a given network environment, and how to reconfigure the network resource (e.g., the bottleneck buffer size) to mitigate the shrew DDoS with a given attack pattern. Finally, based on our theoretical results, we put forward a simple strategy to defend the shrew attack. The simulation results indicate that this strategy can remarkably increase TCP throughput by nearly half of the bottleneck bandwidth (and can be higher) for general attack patterns.

DESIGN AND VERIFICATION ENVIRONMENT FOR AMBA AXI PROTOCOL FOR SOC INTEGRATION

Advanced microcontroller bus architecture (AMBA) protocol family provides a metric-driven verification of protocol compliance, enabling the comprehensive testing of interface intellectual property (IP) blocks and system-on-chip (SoC) design. The AMBA advanced extensible interface 4 (AXI4) update to AMBA AXI3 includes: the support for burst lengths up to 256 beats. It is updated write response requirements and removal of locked transactions. Verification has become the dominant cost in the design process. This paper proposes a work, how to build up the verification environment of AXI bus using SystemVerilog is introduced. Functional coverage, score-boarding and assertions is implemented with the proposed integrated verification environment.

An in vivo, MRI-integrated real-time model of active contrast extravasation in acute intracerebral hemorrhage.

The "spot sign" or contrast extravasation is strongly associated with hematoma formation and growth. An animal model of contrast extravasation is important to test existing and novel therapeutic interventions to inform present and future clinical studies. The purpose of this study was to create an animal model of contrast extravasation in acute intracerebral hemorrhage. Twenty-eight hemispheres of Yorkshire male swine were insonated with an MR imaging-guided focused sonography system following lipid microsphere infusion and mean arterial pressure elevation. The rate of contrast leakage was quantified by using dynamic contrast-enhanced MR imaging and was classified as contrast extravasation or postcontrast leakage by using postcontrast T1. Hematoma volume was measured on gradient recalled-echo MR imaging performed 2 hours postprocedure. Following this procedure, sacrificed brain was subjected to histopathologic examination. Power level, burst length, and blood pressure elevation were correlated with leakage rate, hematoma size, and vessel abnormality extent. Median (intracerebral hemorrhage) contrast extravasation leakage was higher than postcontrast leakage (11.3; 6.3-23.2 versus 2.4; 1.1-3.1 mL/min/100 g; P<.001). Increasing burst length, gradient recalled-echo hematoma (ρ=0.54; 95% CI, 0.2-0.8; P=.007), and permeability were correlated (ρ=0.55; 95% CI, 0.1-0.8; P=.02). Median permeability (P=.02), gradient recalled-echo hematoma (P=.02), and dynamic contrast-enhanced volumes (P=.02) were greater at 1000 ms than at 10 ms. Within each burst-length subgroup, incremental contrast leakage was seen with mean arterial pressure elevation (ρ=0.2-0.8). We describe a novel MR imaging-integrated real-time swine intracerebral hemorrhage model of acute hematoma growth and contrast extravasation.

Pre-Deflection Routing with Blocking Probability Estimation Scheme in Optical Burst Switch Networks

Optical burst switching (OBS) technology has been proposed as a promising switching solution for the terabit bandwidth utilization in next-generation wavelength division multiplexing (WDM) optical transport network. Control architecture and Contention resolution are the main issues faced by the Optical Burst Switching networks. This paper only taking care of the Contention problem and to overcome this issue we propose Pre-Deflection Routing with blocking probability estimation Scheme for Optical Burst Switch Networks. In this paper Pre-deflection routing approach has been proposed in which routing is carried out in two ways, Shortest Path First (SPF) and Least Hop First (LHF) Routing to forward the clusters and canoes respectively. Hereafter blocking probability estimation Scheme has been proposed where a forward control packet collects the congestion price and contention price along its paths. If the contention is very high at some particular core nodes then it drops that node and thereafter source node uses this information to revise its burst length and offset time.

Nonuniform Temperature Rise in In Vitro Osteoblast Ultrasound Exposures With Associated Bioeffect

There is a growing interest to use ultrasound to stimulate cellular material in vitro conditions for the treatment of musculoskeletal disorders. However, the beneficial effect resulting from ultrasound exposure is not accurately specified. Many in vitro ultrasound setups are very vulnerable to temperature elevation due to sound absorption, sound reflections, and inadequate heat transfer. The objective of this study is to show that temperature variations capable of modifying biological results may exist in common in vitro exposure system. Human osteoblastic MG-63 cells plated on a 24-well cell plate were treated with pulsed ultrasound in 37°C water bath (10min, frequency= 1.035MHz, burst length= 200μs, pulse repetition frequency= 1kHz, duty cycle= 0.2, temporal-average acoustic power= 2W, and peak pressure= 670-730kPa) and the activation of heat-dependent canonical Wnt cell signaling was measured. The ultrasound-induced temperature rise was measured with thermocouples and infrared imaging. Chamber-to-chamber comparison showed substantial temperature variation (41.6°C versus 49.1°C) among the different chambers. The chamber walls were the most susceptible to heating. The variations in the chamber temperatures correlated to variations in the cell signaling levels (1.3-fold versus 11.5-fold increase). These observations underline the need for system-specific temperature measurements during in vitro exposures.

Experimental Investigation of Reed-Solomon Error Correction Technique for Wireless Sensor Network

In this paper, we propose a Reed-Solomon (RS) error correction code with an error correction capability of 32 bytes for IEEE 802.15.4 wireless sensor network (WSN). This code is chosen based on our experimental investigation and the analysis of error pattern, which revealed that although there are as much as 82% of burst errors out of the total errors are present at WSN, the rate of occurrence of the burst errors decreases when the burst length increases. Experimental results show that the proposed error correction code is able to reduce the packet error rate (PER) significantly for distances shorter than 40 m. At the target PER of 10-3, the proposed technique is able to improve either the transmission distance by about 10 m or the received signal strength indication (RSSI) by about 8 dB compared to the WSN without error correction.

Hybrid approach for loss recovery mechanism in OBS networks

This letter reports a study of a hybrid burst assembly and a hybrid burst loss recovery scheme (delay-based burst assembly and hybrid loss recovery (DBAHLR)) which selectively employs proactive or reactive loss recovery techniques depending on the classification of traffic into short term and long term, respectively. Traffic prediction and segregation of optical burst switching network flows into the long term and short term are conducted based on predicted link holding times using the hidden Markov model (HMM). The hybrid burst assembly implemented in DBAHLR uses a consecutive average-based burst assembly to handle jitter reduction necessary in real-time applications, with variations in burst sizes due to the non-monotonic nature of the average delay handled by additional burst length thresholding. This dynamic hybrid approach based on HMM prediction provides overall a lower blocking probability and delay and more throughput when compared with forward segment redundancy mechanism or purely HMM prediction-based adaptive burst sizing and wavelength allocation (HMM-TP).

Two-dimensional image reconstruction with spectrally-randomized ultrasound signals

An ultrasound imaging method using unfocused frequency-randomized transmissions and image reconstruction from data received by a single element is experimentally demonstrated. The elements of an ultrasound imaging array are randomly assigned different frequencies and driven by a multicycle sinusoidal burst. The resulting acoustic field is spectrally unique and target localization is possible based on the a priori knowledge of this field. A 64-element phased array driven by arbitrary waveform generators is used in the experiments. Transmission frequencies range from 2.00 to 2.64 MHz with 10 kHz resolution. One element of the array is reserved for receiving backscattered signals and an image is reconstructed from the signals received by this single element. Reconstruction is based on cross-correlation of the received data with transmitted bursts to obtain radial elliptical projections. Multiple projections are obtained from single received data, which are back-projected to obtain an image. Successful target localization is made possible through multiple frequency-randomized acquisitions. The performance of the method is measured using images of a single point target. These images are quantified and analyzed in terms of their point spread function (PSF) and SNR. Optimum imaging parameters, such as the number of acquisitions, transmit burst length, and number of possible receivers, are obtained through further analysis of SNR. Images obtained with the frequency-randomized transmission method compared well with the performance measurements of a typical B-mode acquisition. It is demonstrated that the frequency-randomized method provides images superior to B-mode images in terms of PSF. The two-point discrimination threshold is measured to be 2 mm in the lateral and azimuth directions.

Intercomparison of radiation protection instrumentation in a pulsed neutron field

In the framework of the EURADOS working group 11, an intercomparison of active neutron survey meters was performed in a pulsed neutron field (PNF). The aim of the exercise was to evaluate the performances of various neutron instruments, including commercially available rem-counters, personal dosemeters and instrument prototypes. The measurements took place at the cyclotron of the Helmholtz-Zentrum Berlin für Materialien und Energie GmbH. The cyclotron is routinely used for proton therapy of ocular tumours, but an experimental area is also available. For the therapy the machine accelerates protons to 68MeV. The interaction of the proton beam with a thick tungsten target produces a neutron field with energy up to about 60MeV. One interesting feature of the cyclotron is that the beam can be delivered in bursts, with the possibility to modify in a simple and flexible way the burst length and the ion current. Through this possibility one can obtain radiation bursts of variable duration and intensity. All instruments were placed in a reference position and irradiated with neutrons delivered in bursts of different intensity. The analysis of the instrument response as a function of the burst charge (the total electric charge of the protons in the burst shot onto the tungsten target) permitted to assess for each device the dose underestimation due to the time structure of the radiation field. The personal neutron dosemeters were exposed on a standard PMMA slab phantom and the response linearity was evaluated.

Finite-size effects on the quasistatic displacement pulse in a solid specimen with quadratic nonlinearity

There is an unresolved debate in the scientific community about the shape of the quasistatic displacement pulse produced by nonlinear acoustic wave propagation in an elastic solid with quadratic nonlinearity. Early analytical and experimental studies suggested that the quasistatic pulse exhibits a right-triangular shape with the peak displacement of the leading edge being proportional to the length of the tone burst. In contrast, more recent theoretical, analytical, numerical, and experimental studies suggested that the quasistatic displacement pulse has a flat-top shape where the peak displacement is proportional to the propagation distance. This study presents rigorous mathematical analyses and numerical simulations of the quasistatic displacement pulse. In the case of semi-infinite solids, it is confirmed that the time-domain shape of the quasistatic pulse generated by a longitudinal plane wave is not a right-angle triangle. In the case of finite-size solids, the finite axial dimension of the specimen cannot simply be modeled with a linear reflection coefficient that neglects the nonlinear interaction between the combined incident and reflected fields. More profoundly, the quasistatic pulse generated by a transducer of finite aperture suffers more severe divergence than both the fundamental and second order harmonic pulses generated by the same transducer.

P.12.5 Subunit specific effects of the invariant AChR Cys-loop Aspartate residues on gating and AChR expression

The signature Cys-loop at the interface between binding and gating domains of AChR is crucial for coupling agonist binding to gating but the mechanism is not fully understood. An invariant Cys-loop Asp is present at equivalent positions in all subunits of Cys-loop superfamily receptors of all species, but its functional significance is not known. After discovering that a phenotype-determining Asp140Asn in the AChR δ subunit causes a severe congenital myasthenic syndrome (CMS), we introduced the same mutation into the AChR α, β, and e subunits and examined the expression, burst openings, and gating efficiency of each mutant in HEK cells. We employed mutation analysis, mutagenesis, single-channel recordings, and mutant cycle analysis using wild-type and mutant receptors expressed in HEK cells. Compared to wild-type, the respective protein expressions of the α, β, δ and e mutants were 54%, 79%, 21%, and 100%; the corresponding burst durations were 7%, 18%, 55%, and 62%; and the corresponding gating efficiencies were 1%, 23%, 75%, and 108%. To understand why α Asp138Asn has the greatest effects on gating, we examined its thermodynamic interactions with nearby residues by mutant cycle analysis. This revealed that corresponding αAsp138 is functionally linked to nearby αGln208 which is conserved in mammalian α-subunits and is adjacent to the invariant αArg209 which was previously shown to be essential for rapid and efficient gating. (1) The invariant Cys-loop Asp residues contribute to receptor expression, burst duration, and gating efficiency in a subunit-specific manner. (2) The α-subunit Asp has profound effects on burst length and gating efficiency whereas δ-Asp predominantly affects AChR expression. (3) Mutant cycle analysis indicates that αAsp138 is an essential link in the chain of conformational changes that couple agonist binding to gating. (4) The δAsp140Asn causes CMS mainly by reducing AChR expression.

Regulation of Electrical Bursting in a Spatiotemporal Model of a GnRH Neuron

Gonadotropin-releasing hormone (GnRH) neurons are hypothalamic neurons that control the pulsatile release of GnRH that governs fertility and reproduction in mammals. The mechanisms underlying the pulsatile release of GnRH are not well understood. Some mathematical models have been developed previously to explain different aspects of these activities, such as the properties of burst action potential firing and their associated Ca(2+) transients. These previous studies were based on experimental recordings taken from the soma of GnRH neurons. However, some research groups have shown that the dendrites of GnRH neurons play very important roles. In particular, it is now known that the site of action potential initiation in these neurons is often in the dendrite, over 100μm from the soma. This raises an important question. Since some of the mechanisms for controlling the burst length and interburst interval are located in the soma, how can electrical bursting be controlled when initiated at a site located some distance from these controlling mechanisms? In order to answer this question, we construct a spatio-temporal mathematical model that includes both the soma and the dendrite. Our model shows that the diffusion coefficient for the spread of electrical potentials in the dendrite is large enough to coordinate burst firing of action potentials when the initiation site is located at some distance from the soma.

Performance Limits and Practical Decoding of Interleaved Reed-Solomon Polar Concatenated Codes

A scheme for concatenating the recently invented polar codes with non-binary MDS codes, as Reed-Solomon codes, is considered. By concatenating binary polar codes with interleaved Reed-Solomon codes, we prove that the proposed concatenation scheme captures the capacity-achieving property of polar codes, while having a significantly better error-decay rate. We show that for any $\epsilon > 0$, and total frame length $N$, the parameters of the scheme can be set such that the frame error probability is less than $2^{-N^{1-\epsilon}}$, while the scheme is still capacity achieving. This improves upon $2^{-N^{0.5-\epsilon}}$, the frame error probability of Arikan's polar codes. The proposed concatenated polar codes and Arikan's polar codes are also compared for transmission over channels with erasure bursts. We provide a sufficient condition on the length of erasure burst which guarantees failure of the polar decoder. On the other hand, it is shown that the parameters of the concatenated polar code can be set in such a way that the capacity-achieving properties of polar codes are preserved. We also propose decoding algorithms for concatenated polar codes, which significantly improve the error-rate performance at finite block lengths while preserving the low decoding complexity.

DYNAMIC PULSE INTEGRATING CIRCUIT FOR INFRARED RECEIVERS

In this paper, a frequency-tunable dynamic pulse integrating circuit for infrared receivers is presented. The proposed circuits possess many advantages, such as high sensitivity, high immunity against disturbances, simple structure, and so on. This integrator not only defines a minimum time for the burst length and a minimum time between the bursts, but also achieves the same minimum number of pulses in different frequencies. The frequency-tunable dynamic pulse integrator is a combined structure of the center frequency modulation and a new type of pulse integrator. The center frequency modulation is implemented by using zener zap anti-fuse trim and a second-order band-pass filter (BPF) with bipolar operational transconductance amplifier (OTA) cell. The integrator also describes the characteristics of variable-error tolerance to prevent the output envelope error due to the lack of individual pulses. The results of simulation are shown that the center frequency is available from 33 to 40 kHz and 56 kHz in typical application by Cadence respectively. Moreover, the minimum burst length is 10 pulses and minimum bursts gap time is 14 pulses in typical application.

Dynamin phosphorylation controls optimization of endocytosis for brief action potential bursts

Modulation of synaptic vesicle retrieval is considered to be potentially important in steady-state synaptic performance. Here we show that at physiological temperature endocytosis kinetics at hippocampal and cortical nerve terminals show a bi-phasic dependence on electrical activity. Endocytosis accelerates for the first 15-25 APs during bursts of action potential firing, after which it slows with increasing burst length creating an optimum stimulus for this kinetic parameter. We show that activity-dependent acceleration is only prominent at physiological temperature and that the mechanism of this modulation is based on the dephosphorylation of dynamin 1. Nerve terminals in which dynamin 1 and 3 have been replaced with dynamin 1 harboring dephospho- or phospho-mimetic mutations in the proline-rich domain eliminate the acceleration phase by either setting endocytosis at an accelerated state or a decelerated state, respectively. DOI:http://dx.doi.org/10.7554/eLife.00845.001.