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Drivers are increasingly studied ablation targets for atrial fibrillation (AF). However, results from ablation remain controversial. First, outcomes vary between centers and patients. Second, it is unclear how best to perform driver ablation. Third, there is a lack of practical guidance on how to identify critical from secondary sites using different AF mapping methods. This article addresses each of these issues. [ABSTRACT FROM AUTHOR]

• Residual stress and phase analysis at the microscale at interface and coping edge. • X-ray diffraction and Raman spectroscopy show comparable results. • Cross validation using ring-core focused ion beam and digital image correlation. • Monoclinic and highly stressed regions identified close to interface. • Phase transformation volumetric expansion is the origin of porcelain failure. Yttria Partially Stabilised Zirconia (YPSZ) is a high strength ceramic which has become widely used in porcelain veneered dental copings due to its exceptional toughness. Within these components the residual stress and crystallographic phase of YPSZ close to the interface are highly influential in the primary failure mode; near interface porcelain chipping. In order to improve present understanding of this behaviour, characterisation of these parameters is needed at an improved spatial resolution. In this study transmission micro-focus X-ray Diffraction, Raman spectroscopy, and focused ion beam milling residual stress analysis techniques have, for the first time, been used to quantify and cross-validate the microscale spatial variation of phase and residual stress of YPSZ in a prosthesis cross-section. The results of all techniques were found to be comparable and complementary. Monoclinic YPSZ was observed within the first 10 μm of the YPSZ-porcelain interface with a maximum volume fraction of 60 %. Tensile stresses were observed within the first 150 μ m of the interface with a maximum value of ≈ 300 M P a at 50 μ m from the interface. The remainder of the coping was in mild compression at ≈ − 30 MPa, with shear stresses of a similar magnitude also being induced by the YPSZ phase transformation. The analysis indicates that the interaction between phase transformation, residual stress and porcelain creep at YPSZ-porcelain interface results in a localised porcelain fracture toughness reduction. This explains the increased propensity of failure at this location, and can be used as a basis for improving prosthesis design. [ABSTRACT FROM AUTHOR]

Mapping the spatial distribution of crystal phases with nm-scale spatial resolution is an important characterisation task in studies of multi-phase materials. One popular approach is to use scanning precession electron diffraction which enables semi-automatic phase mapping at the nanoscale by collecting a single precession electron diffraction pattern at every probe position over regions spanning up to a few micrometers. For a successful phase mapping each diffraction pattern must be correctly identified. In this work four different approaches for phase mapping of embedded precipitates in an Al-Cu-Li alloy are compared on a sample containing three distinct crystal phases. These approaches are based on: non-negative matrix factorisation, vector matching, template matching and artificial neural networks. To evaluate the success of each approach a ground truth phase map was manually created from virtual images based on characteristic phase morphologies and compared with the deduced phase maps. The percentage accuracy of all methods when compared to the ground truth was satisfactory, with all approaches obtaining scores above 98%. The optimal method depends on the specific task at hand. Non-negative matrix factorisation is suitable with limited prior data knowledge but performs best with few unique diffraction patterns and requires substantial post-processing. It has the advantage of reducing the dimensionality of the dataset and handles weak diffracted intensities well given that they occur repeatedly. The current vector matching implementation is fast, simple, based only on the Bragg spot geometry and requires few parameters. It does however demand that each Bragg spot is accurately detected in each pattern and the current implementation is limited to zone axis patterns. Template matching handles a large range of orientations, including off-axis patterns. However, achieving successful and reliable results often require thorough data pre-processing and do require adequate diffraction simulations. For artificial neural networks a substantial setup effort is demanded but once trained it excels for routine tasks, offering fast predictions. The implemented codes and the data used are available open-source. These resources and the detailed assessment of the methods will allow others to make informed decisions when selecting a data analysis approach for 4D-STEM phase mapping tasks on other material systems. • Four different approaches for 4D-STEM phase mapping are implemented and compared. • NMF is easy to get started with but requires user-dependent post-processing. • Vector matching, implemented in the current work, is reliable and straight-forward. • Template matching requires user-dependent pre-processing and can be time consuming. • Neural networks are fast and reliable but training the network is tedious. [ABSTRACT FROM AUTHOR]

• Arc fault detection using voltage characteristics. • Fault with switching power supply loads has a dispersed energy distribution but with a high amplitude of total energy. • Fault with non-switching power supply loads has a small energy amplitude but with a concentrated phase distribution. • A new detection criterion using characteristic energy amplitude and phase mapping distribution. The existing series arc fault detection methods are mainly realized by characteristics of current, due to the diversity of load current waveforms, it is difficult to construct universal detection criteria for this type of methods. In case of arc fault, the existence of power supply and line inductance causes the fault information of characteristic frequency band of arc voltage source at the fault point to be reflected at the monitoring point, which provides a new idea for arc fault detection. Based on the analysis of the characteristic law of the arc voltage at the fault point and the fault voltage at the monitoring point, the selection of the characteristic frequency band of the fault information is demonstrated. Based on the distribution characteristics of high-frequency signals of arc voltage waveforms with different loads, a detection strategy for classifying loads into switching power supply and non-switching power supply is proposed. According to their respective fault characteristics, fault detection methods based on voltage characteristic energy amplitude and phase mapping distribution distance are proposed, which construct the comprehensive detection strategy using the amplitude and phase information of characteristic energy to meet the fault detection for different load types. Experimental results show that this method can realize fault detection with different line parameters and load types. [ABSTRACT FROM AUTHOR]

• Liquidus and solidus measured by thermomechanical analysis (TMA) and differential scanning calorimetry (DSC). • Comparison of isobaric heat capacities determined by DSC and high temperature drop calorimetry (HTDC). • Utilization of sealed crucibles to avoid contamination during measurements in molten salt calorimetry. • Systematic study of enthalpy and heat capacity across the NaCl-KCl system using HTDC. • Enthalpy of mixing measured by HTDC and calculation of Gibbs free energy. NaCl-KCl molten salt system has been proposed as a primary component of several promising heat transfer eutectics and fuel host for Generation IV molten salt reactors (MSR). In this work, several key thermodynamic parameters, including high temperature enthalpies, isobaric heat capacities (C p) and molar enthalpies of mixing (ΔH mix), of the NaCl-KCl system (NaCl, 75 mol% NaCl – 25 mol% KCl, 51 mol% NaCl – 49 mol% KCl, 25 mol% NaCl – 75 mol% KCl, and KCl) were measured by high temperature drop calorimetry (HTDC) utilizing laser sealed nickel and aluminum crucibles. Salts were checked for phase purity by X-ray diffraction (XRD), and water content by Karl Fischer coulometric titrimetry and thermogravimetric analysis (TGA). Thermo-mechanical analysis (TMA) utilizing custom-built boron nitride (BN) crucibles was employed to determine temperatures of phase transitions (solid → liquid) for the salts and plotted against the pseudobinary phase diagram for the NaCl-KCl system. Small deviations (3–10 %) were found among C p values obtained from HTDC, differential scanning calorimetry (DSC), and NIST, comparable to the average uncertainty based on two standard deviations of measured data that are ∼6% for DSC and ∼3% for HTDC. Additionally, the measured enthalpies and C p values of mixed NaCl-KCl salts (e.g., 51 mol% NaCl – 49 mol% KCl eutectic) were shown to behave as a nearly statistical mixtures of its pure endmembers, consistent with ΔH mix = −1.324 kJ/mol at 800 °C, and a regular interaction parameter of Ω = 4.77 ± 0.79 kJ/mol. This study represents a step towards improved accuracy and precision in determinations of thermodynamic parameters of molten salts by using DSC, TMA, and HTDC, in completion of the Molten Salt Thermal Properties Database (MSTDB). [ABSTRACT FROM AUTHOR]

Background: Current phase mapping systems for atrial fibrillation create 2-dimensional (2D) maps. This process may affect the accurate detection of rotors. We developed a 3-dimensional (3D) phase mapping technique that uses the 3D locations of basket electrodes to project phase onto patient-specific left atrial 3D surface anatomy.Objective: We sought to determine whether rotors detected in 2D phase maps were present at the corresponding time segments and anatomical locations in 3D phase maps.Methods: One-minute left atrial atrial fibrillation recordings were obtained in 14 patients using the basket catheter and analyzed off-line. Using the same phase values, 2D and 3D phase maps were created. Analysis involved determining the dominant propagation patterns in 2D phase maps and evaluating the presence of rotors detected in 2D phase maps in the corresponding 3D phase maps.Results: Using 2D phase mapping, the dominant propagation pattern was single wavefront (36.6%) followed by focal activation (34.0%), disorganized activity (23.7%), rotors (3.3%), and multiple wavefronts (2.4%). Ten transient rotors were observed in 9 of 14 patients (64%). The mean rotor duration was 1.1 ± 0.7 seconds. None of the 10 rotors observed in 2D phase maps were seen at the corresponding time segments and anatomical locations in 3D phase maps; 4 of 10 corresponded with single wavefronts in 3D phase maps, 2 of 10 with 2 simultaneous wavefronts, 1 of 10 with disorganized activity, and in 3 of 10 there was no coverage by the basket catheter at the corresponding 3D anatomical location.Conclusion: Rotors detected in 2D phase maps were not observed in the corresponding 3D phase maps. These findings may have implications for current systems that use 2D phase mapping. [ABSTRACT FROM AUTHOR]

Introduction Atrial fibrillation (AF) often converts to and from atrial tachycardia (AT), but it is undefined if these rhythms are mechanistically related in such patients. We tested the hypothesis that critical sites for AT may be related to regional AF sources in patients with both rhythms, by mapping their locations and response to ablation on transitions to and from AF. Methods From 219 patients undergoing spatial mapping of AF prior to ablation at 3 centers, we enrolled 26 patients in whom AF converted to AT by ablation (n = 19) or spontaneously (n = 7; left atrial size 42 ± 6 cm, 38% persistent AF). Both atria were mapped in both rhythms by 64-electrode baskets, traditional activation maps and entrainment. Results Each patient had a single mapped AT (17 reentrant, 9 focal) and 3.7 ± 1.7 AF sources. The mapped AT spatially overlapped one AF source in 88% (23/26) of patients, in left (15/23) or right (8/23) atria. AF transitioned to AT by 3 mechanisms: (a) ablation anchoring AF rotor to AT (n = 13); (b) residual, unablated AF source producing AT (n = 6); (c) spontaneous slowing of AF rotor leaving reentrant AT at this site without any ablation (n = 7). Electrogram analysis revealed a lower peak-to-peak voltage at overlapping sites (0.36 ± 0.2 mV vs 0.49 ± 0.2 mV p = 0.03). Conclusions Mechanisms responsible for AT and AF may arise in overlapping atrial regions. This mechanistic inter-relationship may reflect structural and/or functional properties in either atrium. Future work should delineate how acceleration of an organized AT may produce AF, and whether such regions can be targeted a priori to prevent AT recurrence post AF ablation. [ABSTRACT FROM AUTHOR]

Background and Objective Optimal targets for persistent atrial fibrillation (persAF) ablation are still debated. Atrial regions hosting high dominant frequency (HDF) are believed to participate in the initiation and maintenance of persAF and hence are potential targets for ablation, while rotor ablation has shown promising initial results. Currently, no commercially available system offers the capability to automatically identify both these phenomena. This paper describes an integrated 3D software platform combining the mapping of both frequency spectrum and phase from atrial electrograms (AEGs) to help guide persAF ablation in clinical cardiac electrophysiological studies. Methods 30 s of 2048 non-contact AEGs (EnSite Array, St. Jude Medical) were collected and analyzed per patient. After QRST removal, the AEGs were divided into 4 s windows with a 50% overlap. Fast Fourier transform was used for DF identification. HDF areas were identified as the maximum DF to 0.25 Hz below that, and their centers of gravity (CGs) were used to track their spatiotemporal movement. Spectral organization measurements were estimated. Hilbert transform was used to calculate instantaneous phase. Results The system was successfully used to guide catheter ablation for 10 persAF patients. The mean processing time was 10.4 ± 1.5 min, which is adequate comparing to the normal electrophysiological (EP) procedure time (120∼180 min). Conclusions A customized software platform capable of measuring different forms of spatiotemporal AEG analysis was implemented and used in clinical environment to guide persAF ablation. The modular nature of the platform will help electrophysiological studies in understanding of the underlying AF mechanisms. [ABSTRACT FROM AUTHOR]

The utilization of municipal solid waste (MSW) incineration bottom ash (IBA) in the infrastructure construction is a double-win solution to feed the fueling demand for building stones and binding materials. However, MSWIBA is a so highly heterogeneous and variable material that the macro-scale researched results cannot guarantee its behavior at any moment and under any conditions. Therefore, we should figure out why the heterogeneity will happen and how the heterogeneity affects the mechanical behavior of the mixtures. In this paper, the heterogeneity of mixtures contained IBA was investigated at nano-scale from the point of view of chemistry, microstructure, and micromechanics. Nanoindentation (NI) testing together with the image processing technique and statistical method was performed to evaluate the elastic modulus and creep parameters’ variation in the measured regions. The test sample was then studied by FESEM observation to illustrate its disordered microstructure. Finally, elemental and phase investigation of the NI sample was carried out by Energy-dispersive X-ray (EDX), which further gave the fundamental arguments why the MSW IBA mixtures present apparent heterogeneous behavior. It can be concluded that nanoindentation elastic/creep testing, FESEM observation, and EDX chemical analysis give mutual verification to illustrate the heterogeneous phenomenon in IBA cement mixtures. [ABSTRACT FROM AUTHOR]

Background: The majority of life-threatening ventricular tachycardias (VTs) are sustained by heterogeneous scar substrates with narrow strands of surviving tissue. An effective treatment for scar-related VT is to modify the underlying scar substrate by catheter ablation. If activation sequence and entrainment mapping can be performed during sustained VT, the exit and isthmus of the circuit can often be identified. However, with invasive catheter mapping, only monomorphic VT that is hemodynamically stable can be mapped in this manner. For the majority of patients with poorly tolerated VTs or multiple VTs, a close inspection of the re-entry circuit is not possible. A noninvasive approach to fast mapping of unstable VTs can potentially allow an improved identification of critical ablation sites.Methods: For patients who underwent catheter ablation of scar-related VT, CT scan was obtained prior to the ablation procedure and 120-lead body-surface electrocardiograms (ECGs) were acquired during induced VTs. These data were used for noninvasive ECG imaging to computationally reconstruct electrical potentials on the epicardium and on the endocardium of both ventricles. Activation time and phase maps of the VT circuit were extracted from the reconstructed electrograms. They were analyzed with respect to scar substrate obtained from catheter mapping, as well as VT exits confirmed through ablation sites that successfully terminated the VT.Results: The reconstructed re-entry circuits correctly revealed both epicardial and endocardial origins of activation, consistent with locations of exit sites confirmed from the ablation procedure. The temporal dynamics of the re-entry circuits, particularly the slowing of conduction as indicated by the crowding and zig-zag conducting of the activation isochrones, collocated well with scar substrate obtained by catheter voltage maps. Furthermore, the results indicated that some re-entry circuits involve both the epicardial and endocardial layers, and can only be properly interpreted by mapping both layers simultaneously.Conclusions: This study investigated the potential of ECG-imaging for beat-to-beat mapping of unstable reentrant circuits. It shows that simultaneous epicardial and endocardial mapping may improve the delineation of the 3D spatial construct of a re-entry circuit and its exit. It also shows that the use of phase mapping can reveal regions of slow conduction that collocate well with suspected heterogeneous regions within and around the scar. [ABSTRACT FROM AUTHOR]

The paper describes an automated crystal orientation and phase mapping technique that allows nanoscale characterization of crystalline materials with a transmission electron microscope. The template matching strategy used to identify the diffraction patterns is detailed and the resulting outputs of the technique are illustrated. Some examples of applications are used to demonstrate the capability of the tool and potential developments are discussed. [ABSTRACT FROM AUTHOR]

Vibration analysis is an extremely important issue in many fields of production systems like quality control as well as maintenance procedures. In this work it is theoretically studied the behavior of structured light in the form of straight sinusoidal fringes projected on vibrating objects. It was shown that by time averaging the moving fringes on the vibrating surface the resulting light pattern can be described with the help of the zero-order Bessel function of the vibration amplitude and constant factors related to the optical setup geometry. A simple formula was derived allowing to determine the Bessel function by combining the projected light patterns in different object configurations. The amplitude distribution in turn was retrieved from the Bessel function with the help of the explicit Euler method. It was also demonstrated that the phase mapping can be carried out by illuminating the object with a properly oscillating light pattern. The vibration analyses of a rectangular bar and of a square plate was simulated and its possible applications were pointed out. • A method for 3D vibration amplitude mapping by structured light projection is proposed. • The amplitude map is retrieved from the visibility of the projected fringes. • A study of the phase mapping is also carried out. • It is shown that the fringe visibility causes also fringe pattern phase shifts. • Procedures for removing fringe visibility ambiguities are proposed. [ABSTRACT FROM AUTHOR]

Abstract: Decrease of the human brain temperature was induced by intranasal cooling. The main purpose of this study was to compare the two magnetic resonance methods for monitoring brain temperature changes during cooling: phase-difference and magnetic resonance spectroscopic imaging (MRSI) with high spatial resolution. Ten healthy volunteers were measured. Selective brain cooling was performed through nasal cavities using saline-cooled balloon catheters. MRSI was based on a radiofrequency spoiled gradient echo sequence. The spectral information was encoded by incrementing the echo time of the subsequent eight image records. Reconstructed voxel size was 1×1×5 mm3. Relative brain temperature was computed from the positions of water spectral lines. Phase maps were obtained from the first image record of the MRSI sequence. Mild hypothermia was achieved in 15–20 min. Mean brain temperature reduction varied in the interval <−3.0; −0.6>°C and <−2.7; −0.7>°C as measured by the MRSI and phase-difference methods, respectively. Very good correlation was found in all locations between the temperatures measured by both techniques except in the frontal lobe. Measurements in the transversal slices were more robust to the movement artifacts than those in the sagittal planes. Good agreement was found between the MRSI and phase-difference techniques. [Copyright &y& Elsevier]

Abstract: In this work, we aim to demonstrate the ability of Laplace-filtered three-dimensional (3D) phase maps to selectively depict the susceptibility transitions in an object. To realize this goal, it is first shown that both the Laplace derivative of the z component of the static magnetic field in an object and the Laplacian of the corresponding phase distribution may be expected to be zero in regions of constant or linearly varying susceptibility and to be nonzero when there is an abrupt change in susceptibility, for instance, at a single point, a ridge, an interface, an edge or a boundary. Next, a method is presented by which the Laplace derivative of a 3D phase map can be directly extracted from the complex data, without the need for phase unwrapping or subtraction of a reference image. The validity of this approach and of the theory behind it is subsequently demonstrated by simulations and phantom experiments with exactly known susceptibility distributions. Finally, the potential of the Laplace derivative analysis is illustrated by simulations with a Shepp–Logan digital brain phantom and experiments with a gel phantom containing positive and negative focal susceptibility deviations. [Copyright &y& Elsevier]

A new methodology has been developed to study the fine details of GP zones in age-hardenable aluminium alloys. It is complementary to atomic resolution high-angle annular dark-field scanning transmission electron microscopy imaging, and combines scanning precession electron diffraction with diffraction simulations. To evaluate the method, data was collected from an Al-Zn-Mg alloy in a condition with a dense distribution of GPI zones. Diffraction patterns were recorded in the 〈001〉Al orientation, capturing GPI zones in three projections: along the unique [001]GPI axis, and along the two other mutually orthogonal orientations. The GPI zones viewed along [001]GPI revealed how the truncated octahedron units of the GPI zones were connected in multi-unit GP zones, while the two orientations normal to [001]GPI highlight the internal structure. The stability of the atomic models developed based on the experimental results was verified by density functional theory calculations. • An electron diffraction based technique for studying nano-sized, ordered particles embedded in a host material is presented. • 4D-STEM combined with multi-slice electron diffraction simulations enables phase mapping of ordered clusters in Al alloys. • The methodology is applied to GPI zones in Al-Zn-Mg alloys. [ABSTRACT FROM AUTHOR]

Atomic force microscope phase lag imaging of protein–DNA oligonucleotide complexes has been performed to visualize the immobilized oligonucleotides on the protein surface. In normal sample conditions, neither the topographic nor phase lag images show any discriminate signals for the immobilized oligonucleotides. Use of a highly humid incubator, controls the surface humidity of the sample. Thereby, the phase lag image reveals the oligonucleotide location by the local difference of tip adhesion distribution. The resultant phase lag image shows extremely strong signals in the center of the protein surface, indicating the location of the oligonucleotides with resolution better than 20nm. The signal frequency was strongly influenced by the used oligonucleotide concentration in the range 5nM–50μM. [Copyright &y& Elsevier]