Full Signal Research Articles

AxTract: Microstructure-Driven Tractography Based on the Ensemble Average Propagator.

We propose a novel method to simultaneously trace brain white matter (WM) fascicles and estimate WM microstructure characteristics. Recent advancements in diffusion-weighted imaging (DWI) allow multi-shell acquisitions with b-values of up to 10,000 s/mm2 in human subjects, enabling the measurement of the ensemble average propagator (EAP) at distances as short as 10 μm. Coupled with continuous models of the full 3D DWI signal and the EAP such as Mean Apparent Propagator (MAP) MRI, these acquisition schemes provide unparalleled means to probe the WM tissue in vivo. Presently, there are two complementary limitations in tractography and microstructure measurement techniques. Tractography techniques are based on models of the DWI signal geometry without taking specific hypotheses of the WM structure. This hinders the tracing of fascicles through certain WM areas with complex organization such as branching, crossing, merging, and bottlenecks that are indistinguishable using the orientation-only part of the DWI signal. Microstructure measuring techniques, such as AxCaliber, require the direction of the axons within the probed tissue before the acquisition as well as the tissue to be highly organized. Our contributions are twofold. First, we extend the theoretical DWI models proposed by Callaghan et al. to characterize the distribution of axonal calibers within the probed tissue taking advantage of the MAP-MRI model. Second, we develop a simultaneous tractography and axonal caliber distribution algorithm based on the hypothesis that axonal caliber distribution varies smoothly along a WM fascicle. To validate our model we test it on insilico phantoms and on the HCP dataset.

Simultaneous qualitative and quantitative determination of seven anticoagulant rodenticides in whole blood and urine samples using on-line solid phase extraction with liquid chromatography-linear ion trap mass spectrometry

A new and sensitive analytical method has been developed for the simultaneous determination of seven anticoagulant rodenticides in whole blood and urine samples by liquid chromatography-linear ion trap mass spectrometry (LC-LIT/MS) with on-line solid phase extraction (on-line SPE). The samples were treated with acetonitrile, followed by dilution, centrifugation, and filtration. The resulting solution was injected into the LC system directly and processed by on-line SPE column for enrichment and purification. Separation was performed on a C18 column with mixed mobile phases of methanol and 0.02 mol/L ammonium acetate aqueous solution for gradient elution. The analytes were detected by the mass spectrometer with electrospray ionization (ESI) in negative mode. MS2 full scan signals of the target parent ions within the locked retention time window were recorded. Self-built database searching was performed for qualitative confirmation, and MS2 fragment ions with high sensitivity and specificity were selected for quantification. Simultaneous qualitative and quantitative analyses of the seven rodenticides were achieved in this way. Good linearities were obtained within the investigated mass concentration ranges of the seven rodenticides, with r2 ≥ 0.9958 in blood and r2 ≥ 0.9946 in urine. The LODs varied from 0.02 ng/mL to 1.00 ng/mL, and the LOQs varied from 0.10 ng/mL to 4.00 ng/mL. The recoveries at three spiked levels in blood and urine samples ranged from 81.0% to 113.9%, with RSDs of 0.1%-6.2% (n = 6). The developed method is simple, sensitive, and can be used for the rapid detection and accurate quantification of the seven anticoagulant rodenticides in whole blood and urine samples.

Mobile Ultrasound Plane Wave Beamforming on iPhone or iPad using Metal- based GPU Processing

Mobile and cost effective ultrasound devices are being used in point of care scenarios or the drama room. To reduce the costs of such devices we already presented the possibilities of consumer devices like the Apple iPad for full signal processing of raw data for ultrasound image generation. Using technologies like plane wave imaging to generate a full image with only one excitation/reception event the acquisition times and power consumption of ultrasound imaging can be reduced for low power mobile devices based on consumer electronics realizing the transition from FPGA or ASIC based beamforming into more flexible software beamforming. The massive parallel beamforming processing can be done with the Apple framework “Metal” for advanced graphics and general purpose GPU processing for the iOS platform. We were able to integrate the beamforming reconstruction into our mobile ultrasound processing application with imaging rates up to 70Hz on iPad Air 2 hardware.

Gamma Gaussian Inverse Wishart Probability Hypothesis Density for Extended Target Tracking Using X-Band Marine Radar Data

X-band marine radar systems represent a flexible and low-cost tool for the tracking of multiple targets in a given region of interest. Although suffering several sources of interference, e.g., the sea clutter, these systems can provide high-resolution measurements, both in space and time. Such features offer the opportunity to get accurate information not only about the target position/motion but also about the targets size. Accordingly, in this paper, we exploit emergent extended target tracking (ETT) methodologies in which the target state, typically position/velocity/acceleration, is augmented with the target length and width. In this paper, we propose an ETT procedure based on the popular probability hypothesis density filter, and in particular, we describe the extended target state through the gamma Gaussian inverse Wishart model. The comparative simplicity of the used models allows us to meet the real-time processing constraint required for the practical surveillance purposes. Real-world data from an experimental and operational campaign, collected during the recovery operations of the Costa Concordia wreckage in October 2013, are used to assess the performance of the proposed target tracking methodology. The full signal processing chain is implemented, and considerations of the experimental results are provided. Important nonideal effects, common to every marine radar, are observed and discussed in relation to the assumptions made for the tracking procedure.

Developing an Evolutionary Algorithm to Search for an Optimal Multi-Mother Wavelet Packets Combination

The wavelet transform is a popular analysis tool for non-stationary data, but in many cases, the choice of the mother wavelet and basis set remains uncertain, particularly when dealing with physiological data. Furthermore, the possibility exists for combining information from numerous mother wavelets so as to exploit different features from the data. However, the combinatorics become daunting given the large number of basis sets that can be utilized. Recent work in evolutionary computation has produced a subset selection genetic algorithm specifically aimed at the discovery of small, high-performance, subsets from among a large pool of candidates. Our aim was to apply this algorithm to the task of locating subsets of packets from multiple mother wavelet decompositions to estimate cardiac output from chest wall motions while avoiding the computational cost of full signal reconstruction. We present experiments which show how a continuous assessment metric can be extracted from the wavelets coefficients, but the dual-objective nature of the algorithm (high accuracy with small feature sets) imposes a need to restrict the sensitivity of the continuous accuracy metric in order to achieve the small subset size desired. A possibly subtle tradeoff seems to be needed to meet the dual objectives.

Cytotoxic (9βH)-pimarane and (9βH)-17-norpimarane diterpenes from the tuber of Icacina trichantha.

Three (9βH)-pimaranes, 1, 2, and 3, and two (9βH)-17-norpimaranes, 4 and 5, belonging to a rare compound class in nature, were obtained from the tubers of Icacina trichantha for the first time. Compound 1 is a new natural product, and 2-5 have been previously reported. The structures were elucidated based on NMR and MS data, and optical rotation values. The absolute configurations of (9βH)-pimaranes were unambiguously established based on X-ray crystallographic analysis. Full NMR signal assignments for the known compounds 2, 4, and 5, which were not available in previous publications, are also reported. All five isolates displayed cytotoxic activities on MDA-MB-435 cells (IC50 0.66-6.44 μM), while 2, 3, and 4 also exhibited cytotoxicities on HT-29 cells (IC50 3.00-4.94 μM).

Accelerated Bayesian model-selection and parameter-estimation in continuous gravitational-wave searches with pulsar-timing arrays

We describe several new techniques which accelerate Bayesian searches for continuous gravitational-wave emission from supermassive black-hole binaries using pulsar timing arrays. These techniques mitigate the problematic increase of search-dimensionality with the size of the pulsar array which arises from having to include an extra parameter per pulsar as the array is expanded. This extra parameter corresponds to searching over the phase of the gravitational-wave as it propagates past each pulsar so that we can coherently include the pulsar-term in our search strategies. Our techniques make the analysis tractable with powerful evidence-evaluation packages like MultiNest. We find good agreement of our techniques with the parameter-estimation and Bayes factor evaluation performed with full signal templates, and conclude that these techniques make excellent first-cut tools for detection and characterisation of continuous gravitational-wave signals with pulsar timing arrays. Crucially, at low to moderate signal-to-noise ratios the factor by which the analysis is sped up can be > 100, permitting rigorous programs of systematic injection and recovery of signals to establish robust detection criteria within a Bayesian formalism.

Astronomical receiver modelling using scattering matrices

Proper modelling of astronomical receivers is vital: it describes the systematic errors in the raw data, guides the receiver design process, and assists data calibration. In this paper we describe a method of analytically modelling the full signal and noise behaviour of arbitrarily complex radio receivers. We use electrical scattering matrices to describe the signal behaviour of individual components in the receiver, and noise correlation matrices to describe their noise behaviour. These are combined to produce the full receiver model. We apply this approach to a specified receiver architecture: a hybrid of a continous comparison radiometer and correlation polarimeter designed for the C-Band All-Sky Survey. We produce analytic descriptions of the receiver Mueller matrix and noise temperature, and discuss how imperfections in crucial components affect the raw data. Many of the conclusions drawn are generally applicable to correlation polarimeters and continuous comparison radiometers.

Reduction of Aliasing Effects of RF PWM Modulated Signals by Cross Point Estimation

The trend in transmitter systems is to move the digital domain closer toward the antenna using digital modulators and drivers to reduce circuit complexity and to save power. One promising approach is the use of RF pulse width modulation (RF PWM). Unfortunately purely digital discrete time RF PWM suffers from aliasing problems which limit the achievable resolution. For a 40 MHz bandwidth signal at 2.6 GHz carrier frequency for example the achievable signal quality is limited to ~ 43 dBc. This paper describes the root cause of this effect, an error in the determination of the cross points, due to the sampled nature of the signal and proposes a method to compensate for it. It is shown that by interpolating the signal and estimating the cross points the signal quality can be significantly improved. The interpolation is simplified by interpolating the decomposed outphasing signals instead of the full signal. This has the advantage that a constant instead of a phase modulated reference function can be used. It is shown that by simple cross point estimation the signal quality can already be improved to 65 dBc. When either considering a second modulator or when using a delta sigma like noise shaping architecture the signal quality can be further enhanced to 75 dBc.

Stimulus-related neuroimaging in task-engaged subjects is best predicted by concurrent spiking.

The implicit goal of functional magnetic resonance imaging is to infer local neural activity. There is considerable debate, however, as to whether imaging correlates most linearly with local spiking or some local field potential (LFP) measurement. Through simultaneous neuroimaging (intrinsic-signal optical imaging) and electrode recordings from alert, task-engaged macaque monkeys, we showed previously that local electrophysiology correlates with only a specific stimulus-related imaging component. Here we show that this stimulus-related component--obtained by subtracting a substantial task-related component--is particularly linear with local spiking over a comprehensive range of response strengths. Matches to concurrent LFP measurements are, to varying degrees, poorer. As a control, we also tried matching the full imaging signal to local electrophysiology without subtracting task-related components. These control matches were consistently worse; they were, however, slightly better for gamma LFP than spiking, potentially resolving discrepancies between our findings and earlier reports favoring LFP.

Energy-efficient multi-mode compressed sensing system for implantable neural recordings.

Widely utilized in the field of Neuroscience, implantable neural recording devices could capture neuron activities with an acquisition rate on the order of megabytes per second. In order to efficiently transmit neural signals through wireless channels, these devices require compression methods that reduce power consumption. Although recent Compressed Sensing (CS) approaches have successfully demonstrated their power, their full potential is yet to be explored. Built upon our previous on-chip CS implementation, we propose an energy efficient multi-mode CS framework that focuses on improving the off-chip components, including (i) a two-stage sensing strategy, (ii) a sparsifying dictionary directly using data, (iii) enhanced compression performance from Full Signal CS mode and Spike Restoration mode to Spike CS + Restoration mode and; (iv) extension of our framework to the Tetrode CS recovery using joint sparsity. This new framework achieves energy efficiency, implementation simplicity and system flexibility simultaneously. Extensive experiments are performed on simulation and real datasets. For our Spike CS + Restoration mode, we achieve a compression ratio of 6% with a reconstruction SNDR > 10 dB and a classification accuracy > 95% for synthetic datasets. For real datasets, we get a 10% compression ratio with ∼ 10 dB for Spike CS + Restoration mode.

The Restricted Isometry Property for Banded Random Matrices

In this paper, we investigate the problem of determining the conditions under which the restricted isometry property (RIP) is satisfied for a particular type of matrix referred to in here as a banded random matrix (BRM). Such matrices have been recognized as suitable models for a number of compressive-sensing based sampling architectures, including the interleaved random demodulator, the random demodulator, the parallel non-interleaved random demodulator, the random sampler, and the periodic nonuniform sampler. It is thus important to establish the conditions under which the BRM satisfies the RIP; to our knowledge, this question has not been theoretically addressed in the literature. If the resulting conditions are satisfied, full signal recovery using a convex optimization algorithm is guaranteed. The specific objective of this research is to determine the conditions under which the RIP is satisfied for two possible sampling matricies: a BRM and a BRM multiplied by the discrete Fourier matrix.

Numerical study of a macroscopic finite pulse model of the diffusion MRI signal

Diffusion magnetic resonance imaging (dMRI) is an imaging modality that probes the diffusion characteristics of a sample via the application of magnetic field gradient pulses. The dMRI signal from a heterogeneous sample includes the contribution of the water proton magnetization from all spatial positions in a voxel. If the voxel can be spatially divided into different Gaussian diffusion compartments with inter-compartment exchange governed by linear kinetics, then the dMRI signal can be approximated using the macroscopic Karger model, which is a system of coupled ordinary differential equations (ODEs), under the assumption that the duration of the diffusion-encoding gradient pulses is short compared to the diffusion time (the narrow pulse assumption). Recently, a new macroscopic model of the dMRI signal, without the narrow pulse restriction, was derived from the Bloch–Torrey partial differential equation (PDE) using periodic homogenization techniques. When restricted to narrow pulses, this new homogenized model has the same form as the Karger model.We conduct a numerical study of the new homogenized model for voxels that are made up of periodic copies of a representative volume that contains spherical and cylindrical cells of various sizes and orientations and show that the signal predicted by the new model approaches the reference signal obtained by solving the full Bloch–Torrey PDE in O(ε2), where ε is the ratio between the size of the representative volume and a measure of the diffusion length. When the narrow gradient pulse assumption is not satisfied, the new homogenized model offers a much better approximation of the full PDE signal than the Karger model. Finally, preliminary results of applying the new model to a voxel that is not made up of periodic copies of a representative volume are shown and discussed.

New Gyro While Drilling Technology Delivers Accurate Azimuth and Real-Time Quality Control for All Well Trajectories

Summary In response to the increasing demand for a reduction in the uncertainty of wellbore placement to minimize drilling risks and potential liabilities, a new gyroscopic survey tool capable of operating at any attitude during the drilling process has been developed: an all-attitude gyro while drilling (GWD) tool. Gyro survey systems determine the direction of the survey tool in the wellbore, the tool azimuth, by use of measurements of the horizontal components of Earth's rotation in a process known as gyrocompassing or north finding. Current GWD systems are based on angular rate measurements taken about two axes only. These measurement axes are perpendicular to the direction of the wellbore and perpendicular to each other. Although two-axis systems provide accurate estimates of azimuth near vertical, this accuracy degrades as inclination increases, with the azimuth becoming indeterminate because of a mathematical singularity at 90° inclination. To overcome this, an additional rate measurement about the along-hole axis of the tool needs to be performed. Only gyroscopic instruments with three orthogonal sensitive axes, as adopted in the new tool, are capable of measuring the full horizontal Earth rate signal in all wellbore geometries. This paper describes a number of innovative technological developments that have allowed all-attitude GWD to become a reality, including a new gyroscope designed specifically for the downhole drilling environment, a new system mechanization to control gyroscope biases, a signal-processing technique known as continuous adaptive processing that estimates the g-sensitive bias errors at each gyrocompass station, and a more robust quality control scheme. The new high angle GWD system is well-suited to handle any wellbore-placement needs. These include high inclination kickoffs, infill drilling, relief wells, and the provision of improved accuracy in east/west wells. With the improved reliability of the data comes increased confidence that the resulting survey is representative of the true wellbore trajectory. The detection of gross errors can also be accomplished by comparing real-time GWD and measurement-while-drilling (MWD) data. Further, with the memory multishot capability that is available, reliable high accuracy surveys from section total depth (TD) to surface are generated, verifying both MWD and GWD performance on the trip out and eliminating the need for separate and rig-time-dependent gyroscopic surveys. Finally, a number of case studies are presented to illustrate the performance capabilities of the new gyroscopic system over a range of well trajectories and latitudes. The all-attitude GWD system not only allows the survey-reliability goals to become a reality in a cost-effective manner—as set out in the earlier quality control papers published in conjunction with the SPE Well Positioning Technical Section—but also does this in real time while drilling.

WARM BREEZE FROM THE STARBOARD BOW: A NEW POPULATION OF NEUTRAL HELIUM IN THE HELIOSPHERE

We investigate the signals from neutral He atoms observed from Earth orbit in 2010 by IBEX. The full He signal observed during the 2010 observation season can be explained as a superposition of pristine neutral interstellar He gas and an additional population of neutral He that we call the Warm Breeze. The Warm Breeze is approximately two-fold slower and 2.5 times warmer than the primary interstellar He population, and its density in front of the heliosphere is ~7% that of the neutral interstellar helium. The inflow direction of the Warm Breeze differs by ~19deg from the inflow direction of interstellar gas. The Warm Breeze seems a long-term feature of the heliospheric environment. It has not been detected earlier because it is strongly ionized inside the heliosphere, which brings it below the threshold of detection via pickup ion and heliospheric backscatter glow observations, as well as by the direct sampling of GAS/Ulysses. Possible sources for the Warm Breeze include (1) the secondary population of interstellar helium, created via charge exchange and perhaps elastic scattering of neutral interstellar He atoms on interstellar He+ ions in the outer heliosheath, or (2) a gust of interstellar He originating from a hypothetic wave train in the Local Interstellar Cloud. A secondary population is expected from models, but the characteristics of the Warm Breeze do not fully conform to modeling results. If, nevertheless, this is the explanation, IBEX-Lo observations of the Warm Breeze provide key insights into the physical state of plasma in the outer heliosheath. If the second hypothesis is true, the source is likely to be located within a few thousand of AU from the Sun, which is the propagation range of possible gusts of interstellar neutral helium with the Warm Breeze characteristics against dissipation via elastic scattering in the Local Cloud.

Low-Temperature Enhancement in the Upper Critical Field of Underdoped LaO1−xFxBiS2 (x = 0.1–0.3)

Recently, a series of new superconductors containing BiS2 layers has been discovered.1–6) The BiS2-based superconductors have many similarities with cuprate7) and Fe-based superconductors.8,9) The superconductivity is introduced by carrier (electron) doping into their insulating parent compounds. They have layered crystal structure and the superconducting BiS2 planes could be sandwiched by various charge-reservoir spacer layers, e.g., Bi4O4(SO4)1 x and LnO1 xFx (Ln = rare earth elements). Because of these features, it is expected that there exist a variety of BiS2based superconductors, which will provide an opportunity to investigate exotic superconducting properties. For LaO1 xFxBiS2, the phase diagram of the superconducting transition temperature Tc vs x reported until now down to 2K is shown in Fig. 1 for samples prepared by both the conventional solid state reaction method (as-grown) and the high-pressure-annealing method10) (circles and squares). Tc seems to have a dome structure with a maximum at x 0:5. It has been found that Tc increases up to around 10K in applied pressure or after annealing at high pressure,10,11) although the origin of the Tc enhancement has not been clarified yet. In this article, we investigate the superconducting properties of the as-grown samples in the underdoped region (x < 0:4), which have not been studied yet because temperatures below 1K is needed. Polycrystalline samples of LaO1 xFxBiS2 were prepared by the conventional solid-state reaction method as described in Ref. 2. The obtained samples were characterized by X-ray diffraction with Cu Ki radiation using the 2 –a method. Samples with typical weight of 0.1–0.2 g have been used for ac susceptibility measurements. The real part 0 and imaginary part 00 of ac susceptibility were measured by a mutual inductance method down to 0.15K using a commercial dilution refrigerator. The amplitude of the ac field was 0.3Oe-rms. Figure 2 shows the temperature dependences of 0 and 00 measured in zero field for samples with different F concentrations. We have confirmed that superconducting phase continues down to x 1⁄4 0:1. The data indicate the superconducting volume fraction is larger than 40% for all samples, reflecting the bulk nature of the superconductivity. The value of Tc is defined as the temperature at which 0 reaches 0.1% of the expected full Meissner signal. The obtained data are also plotted (solid triangles) in Fig. 1. Combining with the present data, it becomes clearer that Tc of as-grown samples also has a dome structure with the maximum at x 1⁄4 0:5 and decreases with decreasing F concentration down to x 1⁄4 0:2. On the contrary, Tc at x 1⁄4 0:1 is higher than that at x 1⁄4 0:2. Although we have not clarified the reason for this anomaly, this may be associated with structural instability which probably exists in low x region. Our recent single-crystal structure analysis of LaOBiS2 indicates that the crystal structure is subtly distorted from the tetragonal P4=nmm.12) Note that the existence of anharmonic ferroelectric soft phonons and one-dimensional charge density wave instability have been pointed out by first-principles calculations.13,14) Through the electron–phonon counpling, the superconducting properties in the low x region may be affected by the lattice instability. We have performed the ac susceptibility measurements also in applied fields to determine the superconducting phase boundary. Figure 3 shows the temperature dependence of 0Hc2 for various x determined by temperature and field dependent measurements of 0. The most salient feature in Fig. 3 is that Hc2ðTÞ shows a extraordinary upward curvature with decreasing temperature, especially for x 1⁄4 0:3. This highly unusual behavior is completely different from that of the standard model by Werthamer–Helfand–Hohenberg (WHH);15,16) the dashed lines in Fig. 3 are fits to the data near TcðH 1⁄4 0TÞ. The slope jdð 0Hc2Þ=dTjT1⁄4Tc is 10.082, 14

Heterodyne-detected and ultrafast time-resolved second-harmonic generation for sensitive measurements of charge transfer.

In organic photovoltaics many key ultrafast processes occur at the interface between electron donor and acceptor molecules. Traditional ultrafast spectroscopies, such as pump-probe or time-resolved fluorescence, are not ideal for studying the interface because most of their signal is from the bulk material. Time-resolved second-harmonic generation (TRSHG) spectroscopy solves this problem by only generating signal from the interface. We demonstrate an optically heterodyned TRSHG to reduce the impact of stray light, enhance sensitivity, and detect the full complex signal field.

Evaluation of a Simple Pure Pursuit Path-Following Algorithm for an Autonomous, Articulated-Steer Vehicle

Abstract. A pure-pursuit navigational control algorithm in an autonomous articulated-steer vehicle was studied as a simple method for path-following. Paths were created using GPS coordinates and the articulated-steer vehicle programmed to follow those paths using a pure-pursuit (goal-seeking) path-following algorithm. A GUI was developed in LabVIEW to read RTK-GPS coordinates, hydraulic pressure and articulation angle, and control the articulated-steer vehicle. The vehicle was tested for its ability to follow five different paths with two speeds and three control pulse signals. Path following succeeded with lower vehicle speed and full pulse signal for the straight and sinusoidal paths. Averaged path-following errors ranged from 6 to 19 cm as the turn radius increased. For a 90 degree turn, the path-following error was almost 80 cm. Path-following improvements could be made with faster control signal updates and a variable look-ahead distance based on vehicle speed and required turning angle. It was concluded that the control architecture is a good basis for navigation of an articulated-steer autonomous vehicle.

Partial Discharge Characteristics Research Based on RVM

In this paper, four original full typical UHF partial discharge signals are measured by using log-periodic antenna in 3-meter anechoic chamber environment. The relevance vector machine is applied for the study of partial discharge characteristics and the two relevance vector machine classifier are applied for the classification and identification of four partial discharge models. The experimental results are satisfactory. Compared with support vector machines, relevance vector machine can obtain more sparse classification model with probabilistic output value. It has a shorter test time and is more suitable for online testing. This method has a good prospect in partial discharge pattern recognition and online monitoring.

Relationship of edge localized mode burst times with divertor flux loop signal phase in JET

A phase relationship is identified between sequential edge localized modes (ELMs) occurrence times in a set of H-mode tokamak plasmas to the voltage measured in full flux azimuthal loops in the divertor region. We focus on plasmas in the Joint European Torus where a steady H-mode is sustained over several seconds, during which ELMs are observed in the Be II emission at the divertor. The ELMs analysed arise from intrinsic ELMing, in that there is no deliberate intent to control the ELMing process by external means. We use ELM timings derived from the Be II signal to perform direct time domain analysis of the full flux loop VLD2 and VLD3 signals, which provide a high cadence global measurement proportional to the voltage induced by changes in poloidal magnetic flux. Specifically, we examine how the time interval between pairs of successive ELMs is linked to the time-evolving phase of the full flux loop signals. Each ELM produces a clear early pulse in the full flux loop signals, whose peak time is used to condition our analysis. The arrival time of the following ELM, relative to this pulse, is found to fall into one of two categories: (i) prompt ELMs, which are directly paced by the initial response seen in the flux loop signals; and (ii) all other ELMs, which occur after the initial response of the full flux loop signals has decayed in amplitude. The times at which ELMs in category (ii) occur, relative to the first ELM of the pair, are clustered at times when the instantaneous phase of the full flux loop signal is close to its value at the time of the first ELM.