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Abstract Background Additional ablation strategies after pulmonary vein isolation (PVI) for patients with nonparoxysmal atrial fibrillation (non‐PAF) lasting ≥2 years have not been fully effective. This is presumably because of insufficient identification of non‐PAF maintenance mechanisms. In this study, we employed a novel online and real‐time phase mapping system, ExTRa Mapping, to identify and modulate rotors as one of the non‐PAF maintenance mechanisms in patients with non‐PAF sustained after PVI. We investigated the relationship between outcomes of ExTRa Mapping‐guided rotor ablation (ExTRa‐ABL) and non‐PAF duration prior to this procedure. Methods This study consisted of 73 non‐PAF patients (63 ± 8 years, non‐PAF duration 31 ± 37 months) who underwent the first ExTRa‐ABL in patients with non‐PAF sustained after completion of PVI. Results Freedom from non‐PAF/atrial tachycardia (AT) recurrence at 12 months after ExTRa‐ABL was achieved in 50 (69%) of patients. The non‐PAF duration prior to ExTRa‐ABL was significantly longer in patients with non‐PAF/AT recurrence after ExTRa‐ABL compared with those without (56 ± 50 vs. 19 ± 22 months, p = .001). In patients with non‐PAF duration of ≤60 months prior to ExTRa‐ABL, compared with >60 months, non‐PAF/AT‐free rate was significantly higher (68.9% vs. 23.1%, p 60 months of non‐PAF duration.

Background: Additional ablation strategies after pulmonary vein isolation (PVI) for patients with nonparoxysmal atrial fibrillation (non‐PAF) lasting ≥2 years have not been fully effective. This is presumably because of insufficient identification of non‐PAF maintenance mechanisms. In this study, we employed a novel online and real‐time phase mapping system, ExTRa Mapping, to identify and modulate rotors as one of the non‐PAF maintenance mechanisms in patients with non‐PAF sustained after PVI. We investigated the relationship between outcomes of ExTRa Mapping‐guided rotor ablation (ExTRa‐ABL) and non‐PAF duration prior to this procedure. Methods: This study consisted of 73 non‐PAF patients (63 ± 8 years, non‐PAF duration 31 ± 37 months) who underwent the first ExTRa‐ABL in patients with non‐PAF sustained after completion of PVI. Results: Freedom from non‐PAF/atrial tachycardia (AT) recurrence at 12 months after ExTRa‐ABL was achieved in 50 (69%) of patients. The non‐PAF duration prior to ExTRa‐ABL was significantly longer in patients with non‐PAF/AT recurrence after ExTRa‐ABL compared with those without (56 ± 50 vs. 19 ± 22 months, p =.001). In patients with non‐PAF duration of ≤60 months prior to ExTRa‐ABL, compared with >60 months, non‐PAF/AT‐free rate was significantly higher (68.9% vs. 23.1%, p <.001), during the follow‐up of 36 ± 18 months. Conclusions: A non‐PAF duration of ≤60 months prior to ExTRa‐ABL was associated with a better outcome. The effect of ExTRa‐ABL was considered to be limited in patients with >60 months of non‐PAF duration. [ABSTRACT FROM AUTHOR]

This paper reports on effects of adding 2, 4 and 6 wt.% Ti to Co–Cr–Mo by micro-plasma based additive manufacturing (MPBAM) process on density, porosity, microstructure, phase formation, inter-diffusion zones, microhardness, and wear characteristics of the resultant alloy with an objective to develop better material for knee implant applications. Bulk and relative density found to decrease, and porosity increase with increase in Ti % to Co–Cr–Mo alloy. Co–Cr–Mo–4Ti alloy showed more pores and their uniform distribution. Microstructures of Co–Cr–Mo–2Ti and Co–Cr–Mo–4Ti alloys are porous and crack-free. Phase analysis of Co–Cr–Mo–4Ti revealed presence of α-Co, ε-Co, and β-titanium phases (having FCC, HCP, and BCC crystal structure respectively), inter-metallic CoTi2, and lamellar chromium carbides i.e. Cr7C3 and Cr23C6. It is confirmed by the phase mapping also. Inverse pole figure maps did not show any preferential orientation of grains and revealed presence of ε-Co phase matrix with traces of grains of chromium carbides and CoTi2 phases. Increasing Ti% in Co–Cr–Mo alloy increased formation of β-Ti and CoTi2 phases which have less hardness than the carbide phases therefore average microhardness of Co–Cr–Mo–2Ti alloy is found as the highest followed by Co–Cr–Mo–4Ti alloy. Coefficient of friction, specific wear rate, and wear volume increase with increase in Ti% in Co–Cr–Mo alloys due to decrease in microhardness and increase in porosity. It also increased ploughing and delamination in the worn track. This study found Co–Cr–Mo–4Ti as a better knee implant material due to its lesser density, uniform porous structure, absence of cracks, moderate microhardness, and wear characteristics.

Persistent atrial fibrillation (PeAF) may develop arrhythmogenic substrates of rotors/multiple wavelets. However, the ways in which pulmonary vein isolation (PVI) affects the dynamics of rotor/multiple wavelets in PeAF patients remain elusive. Real-time phase-mapping (ExTRa mapping, EXT) in the whole left atrium (LA) was performed during PeAF before and after PVI (n = 111). The percentage of time in which rotor/multiple wavelets (phase singularities) was observed during each 5-s phase-mapping recording (non-passive activation ratio, %NP) was measured as an index of its burden. The mapping areas showing %NP ≥ 50% were defined as rotor/multiple-wavelet substrates (RSs). Before PVI, RSs were globally distributed in the LA. After PVI, %NP decreased (< 50%) in many RSs (PVI-modifiable RSs) but remained high (≥ 50%) in some RSs, especially localized in the anterior/septum/inferior regions (PVI-unmodifiable RSs, 2.3 ± 1.0 areas/patient). Before PVI, vagal response (VR) to high-frequency stimulation was observed in 23% of RSs, especially localized in the inferior region. VR disappearance after PVI was more frequently observed in PVI-modifiable RSs (79%) than in PVI-unmodifiable RSs (55%, p < 0.05), suggesting that PVI affects autonomic nerve activities and rotor/multiple wavelet dynamics. PVI-unmodifiable RSs were adjunctively ablated in 104 patients. The 1-year AT/AF-free survival rate was 70% in those with PVI alone (n = 115), and 86% in patients with the adjunctive ablation (log-rank test = 7.65, p < 0.01). PVI suppresses not only ectopic firing but also rotor/multiple wavelets partly via modification of autonomic nerve activities. The adjunctive ablation of PVI-unmodifiable RSs improved the outcome in PeAF patients and might be a novel ablation strategy beyond PVI. [ABSTRACT FROM AUTHOR]

Aiming at the problem of the low accuracy of projector calibration in a structured light system, an improved projector calibration method is proposed in this paper. One of the key ideas is to estimate the sub-pixel coordinates in the projector image plane using local random sample consensus (RANSAC). A bundle adjustment (BA) algorithm is adopted to optimize the calibration parameters to further improve the accuracy and robustness of the projector calibration. After system calibration and epipolar rectification, the mapping relationship between the pixel coordinates and the absolute phase in the projector image plane is established by using cubic polynomial fitting, and the disparity is rapidly solved by using the mapping relationship, which not only ensures the measurement accuracy, but also improves the measurement efficiency. The experimental results demonstrated that the average re-projection error after optimization is reduced to 0.03 pixels, and the proposed method is suitable for high-speed 3D reconstruction without the time-consuming homogenous point searching. [ABSTRACT FROM AUTHOR]

INTRODUCTION: The mechanisms for atrial fibrillation (AF) are unclear in part because diverse mapping techniques yield diverse maps, ranging from stable organized sources to highly disordered waves. We hypothesized that AF mechanisms may be clarified if mapping techniques were compared in the same patients, and referenced to a clinical endpoint. We compared two independent AF mapping techniques in patients in whom ablation terminated persistent AF before pulmonary vein isolation (PVI). METHODS AND RESULTS: We identified 12 patients with persistent AF (61.2 ± 10.8 years, four female) in whom mapping with 64 pole baskets and technique 1 (activation/phase mapping, FIRM) identified rotational activation patterns during at least 50% of the 4-second mapping interval and targeted ablation at these rotational sites terminated AF to sinus rhythm (n = 10) or atrial tachycardia. We analyzed the unipolar electrograms of these patients to determine phase maps of activation by an independent technique 2 (Kuklik, Schotten et al., IEEE Trans Biomed Eng 2015). Compared to technique 1, technique 2 revealed a source in 12 of 12 (100%) cases with spatial concordance in all cases (P

Application of artificial intelligence (AI), and more specifically machine learning, to the physical sciences has expanded significantly over the past decades. In particular, science-informed AI, also known as scientific AI or inductive bias AI, has grown from a focus on data analysis to now controlling experiment design, simulation, execution and analysis in closed-loop autonomous systems. The CAMEO (closed-loop autonomous materials exploration and optimization) algorithm employs scientific AI to address two tasks: learning a material system’s composition-structure relationship and identifying materials compositions with optimal functional properties. By integrating these, accelerated materials screening across compositional phase diagrams was demonstrated, resulting in the discovery of a best-in-class phase change memory material. Key to this success is the ability to guide subsequent measurements to maximize knowledge of the composition-structure relationship, or phase map. In this work we investigate the benefits of incorporating varying levels of prior physical knowledge into CAMEO’s autonomous phase-mapping. This includes the use of ab-initio phase boundary data from the AFLOW repositories, which has been shown to optimize CAMEO’s search when used as a prior.

Aiming at the problem of the low accuracy of projector calibration in a structured light system, an improved projector calibration method is proposed in this paper. One of the key ideas is to estimate the sub-pixel coordinates in the projector image plane using local random sample consensus (RANSAC). A bundle adjustment (BA) algorithm is adopted to optimize the calibration parameters to further improve the accuracy and robustness of the projector calibration. After system calibration and epipolar rectification, the mapping relationship between the pixel coordinates and the absolute phase in the projector image plane is established by using cubic polynomial fitting, and the disparity is rapidly solved by using the mapping relationship, which not only ensures the measurement accuracy, but also improves the measurement efficiency. The experimental results demonstrated that the average re-projection error after optimization is reduced to 0.03 pixels, and the proposed method is suitable for high-speed 3D reconstruction without the time-consuming homogenous point searching.

Background: Although the substrate in persistent atrial fibrillation (PeAF) is not limited to the pulmonary veins (PVs), PV isolation (PVI) remains the cornerstone ablation strategy., Objectives: The aim of this study was to describe the mechanism of outgoing wavefronts (WFs) originating in the PV sleeves during PeAF., Methods: Eleven patients presenting for first-time PeAF ablation were recruited (mean age 63.1 ± 10.9 years, 91% men). A 64-electrode catheter (Constellation; 38 mm) was positioned within the PV under fluoroscopic guidance. An inverse mapping technique was used to reconstruct unipolar atrial electrograms on the PV surface, and the resulting phase maps were used to identify incoming and outgoing WFs at the PV junction and to classify focal and re-entrant activity within the PV sleeves., Results: During PeAF, the PVs gave rise to outgoing WFs with a frequency of 3.7 s -1 (Q1-Q3: 3.4-5.4 s -1 ) compared with 3.6 s -1 (Q1-Q3: 2.8-4.2 s -1 ) for incoming WFs. Circuitous macroscopic re-entry was the dominant mechanism driving outgoing WFs (frequency of re-entry 2.7 s -1 [Q1-Q3: 2.0-3.3 s -1 ] compared with focal activity 1.4 s -1 [Q1-Q3: 1.1-1.5 s -1 ]; P < 0.006). This was initiated by incoming WFs in 80% of cases. Consecutive focal activation from the same location was infrequent (10.0% ± 6.6%, n = 10). Rotors ≥360° were never observed. The median ratio (R) of outgoing to incoming WF frequency was 1.14 (Q1-Q3: 0.84-1.75), with R > 1 in 6 of 11 PVs., Conclusions: Electric activity generated by PV sleeves during PeAF is due mainly to circuitous re-entry initiated by incoming waves, frequently with R > 1. That is, the PVs act less as drivers of atrial fibrillation than as "echo chambers" that sustain and amplify fibrillatory activity., Competing Interests: Funding Support and Author Disclosures Basket catheters were provided by Boston Scientific. Drs Al-Kaisey and Parameswaran are supported by a National Health and Medical Research Council (NHMRC) research scholarship. Prof Kalman is supported by a practitioner fellowship from the NHMRC; and has received research support from Biosense Webster and Medtronic. Drs Meng and Sunderland were supported by Endeavour Fund Grant CONT-50916-ENDSI-UOA from the New Zealand Ministry of Business and Innovation. Assoc Prof Budgett and Prof Smaill have received funding from the New Zealand Ministry of Business and Innovation and from Return on Sciences, New Zealand. Dr Kistler is a recipient of a Clinical Investigator grant from the NHMRC of Australia; has received grants from the Baker Department of Metabolic Health University of Melbourne; has received speaker fees from Abbott Medical; and has served on an advisory board for Biosense Webster. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2024 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Abstract A 41‐year‐old man with persistent atrial fibrillation (AF) underwent radiofrequency (RF) catheter ablation using an online real‐time phase mapping system: ExTRa Mapping. Box isolation could not terminate AF. Subsequently, RF applications on nonpassively activated areas (NPAs), where rotational activations were frequently observed, at the posterior bottom of left atrium outside of box lesion could convert AF to common atrial flutter. Of interest, the NPA near the posterior bottom were located on the patchy fibrotic tissue area assessed by the late‐gadolinium enhancement magnetic resonance imaging. This indicated the possibility of the critical AF rotor meandering through the fibrotic tissue area.

Background. Cardiovascular disorders in children with type 1 diabetes mellitus (DM 1) are the main cause of mortality in adult patients and play a major role in the development of sudden cardiac death. The purpose of the research was to study additional markers of myocardial dysfunction in children with DM 1 by analyzing a single-channel electrocardiogram in the phase space. Materials and methods. The main group consisted of 83 patients aged 4–16 years with DM 1, control group — 95 healthy schoolchildren aged 12–16 years. The traditional and original electrocardiography (ECG) parameters of the first standard lead were studied and automatically calculated using the Fazagraf® system. ECG recording was carried out in a sitting position in a state of relative calm. Results. In children with DM 1, unlike their healthy peers, a typical pattern of traditional ECG is formed, with high and wide P wave, long QTc, flattened and narrow T wave. An increase in the para­meter of square deviation of T wave symmetry (SD βT) was found in 68.7 % of children with DM 1 and in only 30.5 % of healthy schoolchildren. SD βT significantly increases with the duration of DM 1 in children. The group at high risk for the development of cardiovascular complications consists of children with DM duration of 3–5 years. Suboptimal glycemic control and high-risk control greatly increase the instability of myocardial function. Conclusions. An increase in the SD βT parameter can be used as a marker of heart lesion in children with DM 1. Early and systematic examination with further analysis of ECG in the phase space and optimal glycemic control can reduce the level of chronic cardiac complications in children with DM 1.

Due to advances in EDS technology, electron microscopy techniques have become an important tool to determine the relative abundance of mineral phases. However, few studies have directly compared EDS X‐ray mineralogy with traditional techniques for assessing bulk mineralogy and elemental composition. We show that analysing a limited area (~ 0.5–3.2 mm2) of fine‐grained metal extraction samples using EDS X‐ray principal component analysis phase mapping yields results that agree within 10% with more traditional techniques for mineral phases present at greater than 5% m/m. Electron beam sensitive minerals, such as the carbonates, have poor correlations between EDS and X‐ray Diffraction (XRD) and/or WD‐XRF. Likewise, poor correlations between methods can be expected for particles that are smaller than the interaction volume of the electron beam (~ 1.5 µm); this strongly affected the phyllosilicates. One strength of EDS phase mapping is that it can identify phases present below the detection limit of powder XRD (< 1%). Our results demonstrate that EDS phase mapping is sufficient to estimate bulk sample mineralogy. If polished thin sections have been prepared, this approach may save time and/or money relative to the more traditional approaches of preparing separate subsamples for XRD and/or WD‐XRF. [ABSTRACT FROM AUTHOR]

Summary: This research concerns the precipitation and subsequent dissolution of precipitate phases in an Al–0.86Mg–0.62Si–0.1Cu (at.%) alloy subjected to varying thermal exposure during an in situ heating transmission electron microscope (TEM) experiment. The distribution and crystal structure of precipitates were determined by a scanning diffraction approach at multiple stages, pinpointing the precipitates that underwent phase transformations during heating. Obtained results were compared with TEM studies of the material heated ex situ. This revealed differences in the transformation kinetics of precipitates in an electron transparent lamella (thickness ⪆90nm) to that of macroscopic bulk specimens. Lay Description: The precipitate phases that are formed in age‐hardenable Al alloys are conventionally studied using the TEM, with electron transparent specimens prepared from bulk materials heat treated for various times. We demonstrate here that the growth, phase transformation and subsequent dissolution of precipitate phases in the Al–Mg–Si–Cu system can be studied successfully by in situ heating TEM. Imaging and scanning diffraction combined with data postprocessing were used to study the distribution and structure of transforming precipitates. This enabled us to track the precipitates that underwent phase transformations during heating, hence offering a direct quantitative assessment of the precipitation occurring in these materials. The narrow thickness of the electron transparent specimen (≈90 nm) may potentially have affected the resulting precipitation. Therefore, thickness effects were assessed by comparing obtained results with TEM studies of ex situ heated bulk specimens. [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]

ACOM/TEM is an automated electron diffraction pattern indexing tool that enables the structure, phase and crystallographic orientation of materials to be routinely determined. The software package, which is part of ACOM/TEM, has substantially evolved over the last fifteen years and has pioneered numerous additional functions with the constant objective of improving its capabilities to make the tremendous amount of information contained in the diffraction patterns easily available to the user. Initially devoted to the analysis of local crystallographic texture, and as an alternative to both X-ray pole figure measurement and EBSD accessories for scanning electron microscopes, it has rapidly proven itself effective to distinguish multiple different phases contained within a given sample, including amorphous phases. Different strategies were developed to bypass the inherent limitations of transmission electron diffraction patterns, such as 180° ambiguities or the complexity of patterns produced from overlapping grains. Post processing algorithms have also been developed to improve the angular resolution and to increase the computing rate. The present paper aims to review some of these facilities. On-going works on 3D reconstruction are also introduced.

Networks provide a powerful methodology with applications in a variety of biological, technological and social systems such as analysis of brain data, social networks, internet search engine algorithms, etc. To date, directed networks have not yet been applied to characterize the excitation of the human heart. In clinical practice, cardiac excitation is recorded by multiple discrete electrodes. During (normal) sinus rhythm or during cardiac arrhythmias, successive excitation connects neighboring electrodes, resulting in their own unique directed network. This in theory makes it a perfect fit for directed network analysis. In this study, we applied directed networks to the heart in order to describe and characterize cardiac arrhythmias. Proof-of-principle was established using in-silico and clinical data. We demonstrated that tools used in network theory analysis allow determination of the mechanism and location of certain cardiac arrhythmias. We show that the robustness of this approach can potentially exceed the existing state-of-the art methodology used in clinics. Furthermore, implementation of these techniques in daily practice can improve the accuracy and speed of cardiac arrhythmia analysis. It may also provide novel insights in arrhythmias that are still incompletely understood.

Ventricular fibrillation (VF) is a lethal condition that affects millions worldwide. The mechanism underlying VF is unstable reentrant electrical waves rotating around lines called filaments. These complex spatio-temporal patterns can be studied using both experimental and numerical methods. Computer simulations provide unique insights including high resolution dynamics throughout the heart and systematic control of quantities such as fiber orientation and cellular kinetics that are not feasible experimentally. Here we study filament dynamics using two bi-ventricular 3-D high-resolution rabbit heart geometries, one with detailed fine structure and another without fine structure. We studied filament dynamics using anisotropic and isotropic conductivities, and with four cellular action potential models with different recovery kinetics. Spiral wave dynamics observed in isotropic two-dimensional sheets were not predictive of the behavior in the whole heart. In 2-D the four cell models exhibited stable reentry, meandering spiral waves, and spiral-wave breakup. In the whole heart with fine structure, all simulation results exhibited complex dynamics reminiscent of fibrillation observed experimentally. In the whole heart without fine structure, anisotropy acted to destabilize filament dynamics although the number of filaments was reduced compared to the heart with structure. In addition, in isotropic hearts without structure the two cell models that exhibited meandering spiral waves in 2-D, stabilized into figure-of-eight surface patterns. We also studied the sensitivity of filament dynamics to computer system configuration and initial conditions. After large simulation times, different macroscopic results sometimes occurred across different system configurations, likely due to a lack of bitwise reproducibility. The study conclusions were insensitive to initial condition perturbations, however, the exact number of filaments over time and their trends were altered by these changes. In summary, we present the following new results. First, we provide a new cell model that resembles the surface patterns of VF in the rabbit heart both qualitatively and quantitatively. Second, filament dynamics in the whole heart cannot be predicted from spiral wave dynamics in 2-D and we identified anisotropy as one destabilizing factor. Third, the exact dynamics of filaments are sensitive to a variety of factors, so we suggest caution in their interpretation and their quantitative analyses.

Cardiac arrhythmias such as atrial fibrillation (AF) are recognised to be associated with re-entry or rotors. A rotor is a wave of excitation in the cardiac tissue that wraps around its refractory tail, causing faster-than-normal periodic excitation. The detection of rotor centres is of crucial importance in guiding ablation strategies for the treatment of arrhythmia. The most popular technique for detecting rotor centres is Phase Mapping (PM), which detects phase singularities derived from the phase of a signal. This method has been proven to be prone to errors, especially in regimes of fibrotic tissue and temporal noise. Recently, a novel technique called Directed Graph Mapping (DGM) was developed to detect rotational activity such as rotors by creating a network of excitation. This research aims to compare the performance of advanced PM techniques versus DGM for the detection of rotors using 64 simulated 2D meandering rotors in the presence of various levels of fibrotic tissue and temporal noise. Four strategies were employed to compare the performances of PM and DGM. These included a visual analysis, a comparison of F 2 -scores and distance distributions, and calculating p-values using the mid-p McNemar test. Results indicate that in the case of low meandering, fibrosis and noise, PM and DGM yield excellent results and are comparable. However, in the case of high meandering, fibrosis and noise, PM is undeniably prone to errors, mainly in the form of an excess of false positives, resulting in low precision. In contrast, DGM is more robust against these factors as F 2 -scores remain high, yielding F 2 ≥0.931 as opposed to the best PM F 2 ≥0.635 across all 64 simulations., Competing Interests: Declaration of competing interest None Declared., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

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]

A 41‐year‐old man with persistent atrial fibrillation (AF) underwent radiofrequency (RF) catheter ablation using an online real‐time phase mapping system: ExTRa Mapping. Box isolation could not terminate AF. Subsequently, RF applications on nonpassively activated areas (NPAs), where rotational activations were frequently observed, at the posterior bottom of left atrium outside of box lesion could convert AF to common atrial flutter. Of interest, the NPA near the posterior bottom were located on the patchy fibrotic tissue area assessed by the late‐gadolinium enhancement magnetic resonance imaging. This indicated the possibility of the critical AF rotor meandering through the fibrotic tissue area. [ABSTRACT FROM AUTHOR]

Networks provide a powerful methodology with applications in a variety of biological, technological and social systems such as analysis of brain data, social networks, internet search engine algorithms, etc. To date, directed networks have not yet been applied to characterize the excitation of the human heart. In clinical practice, cardiac excitation is recorded by multiple discrete electrodes. During (normal) sinus rhythm or during cardiac arrhythmias, successive excitation connects neighboring electrodes, resulting in their own unique directed network. This in theory makes it a perfect fit for directed network analysis. In this study, we applied directed networks to the heart in order to describe and characterize cardiac arrhythmias. Proof-of-principle was established using in-silico and clinical data. We demonstrated that tools used in network theory analysis allow determination of the mechanism and location of certain cardiac arrhythmias. We show that the robustness of this approach can potentially exceed the existing state-of-the art methodology used in clinics. Furthermore, implementation of these techniques in daily practice can improve the accuracy and speed of cardiac arrhythmia analysis. It may also provide novel insights in arrhythmias that are still incompletely understood. [ABSTRACT FROM AUTHOR]

Imaging the phase distribution of amorphous or partially crystalline organic materials at the nanoscale and analyzing the local atomic structure of individual phases has been a long-time challenge. We propose a new approach for imaging the phase distribution and for analyzing the local structure of organic materials based on scanning transmission electron diffraction (4D-STEM) pair distribution function analysis (PDF). We show that electron diffraction based PDF analysis can be used to characterize the short- and medium-range order in aperiodically packed organic molecules. Moreover, we show that 4D-STEM-PDF does not only provide local structural information with a resolution of a few nanometers, but can also be used to image the phase distribution of organic composites. The distinct and thickness independent contrast of the phase image is generated by utilizing the structural difference between the different types of molecules and taking advantage of the dose efficiency due to use of the full scattering signal. Therefore, this approach is particularly interesting for imaging unstained organic or polymer composites without distinct valence states for electron energy loss spectroscopy. We explore the possibilities of this new approach using [6,6]-phenyl-C61- butyric acid methyl ester (PC61BM) and poly(3-hexylthiophene-2,5-diyl) (P3HT) as the archetypical and best-investigated semiconductor blend used in organic solar cells, compare our phase distribution with virtual dark-field analysis and validate our approach by electron energy loss spectroscopy. [ABSTRACT FROM AUTHOR]

The diffraction patterns acquired with transmission electron microscopes gather reflections from all crystallites that overlap in the foil thickness. The superimposition renders automated orientation or phase mapping difficult, in particular when secondary phase particles are embedded in a dominant diffracting matrix. Several numerical approaches specifically developed to overcome this issue for 4D scanning precession electron diffraction data sets are described. They consist either in emphasizing the signature of the particles or in subtracting the matrix information out of the collected set of patterns. The different strategies are applied successively to a steel sample containing precipitates that are in Burgers orientation relationship with the matrix and to an aluminium alloy with randomly oriented Mn‐rich particles. [ABSTRACT FROM AUTHOR]

Introduction: Phase singularity (PS) mapping provides additional insight into the AF mechanism and is accurate in identifying rotors. The study aimed to evaluate the feasibility of PS mapping in identifying AF rotors using data obtained from an automatic ultra‐rapid high‐resolution mapping system with a high‐density mini‐basket catheter. Methods: Twenty‐three pigs underwent rapid right atrial (RA) pacing (RAP 480 bpm) for 5 weeks before the experiment. During AF, RA endocardial automatic continuous mappings with a mini‐basket catheter were generated using an automatic ultra‐rapid mapping system. Both fractionation mapping and waveform similarity measurements using a PS mapping algorithm were applied on the same recording signals to localize substrates maintaining AF. Results: Seventeen (74%) pigs developed sustained AF after RAP. Three were excluded because of periprocedural ventricular arrhythmia and corrupted digital data. RA fractionation maps were acquired with 6.17 ± 4.29 minutes mean acquisition time, 13768 ± 12698 acquisition points mapped during AF from 581 ± 387 beats. Fractionation mapping identified extensively distributed (66.7%) RA complex fractionated atrial electrogram (CFAE), whereas the nonlinear analysis identified high similarity index (SI > 0.7) parts in limited areas (23.7%). There was an average of 1.67 ± 0.87 SI sites with 0.43 ± 0.76 rotor/focal source/chamber. AF termination occurred in 11/16 (68.75%) AF events in 14 pigs during ablation targeting max CFAE. There was a higher incidence of rotor/focal source at AF termination sites compared with non‐AF termination sites (54.5% vs 0%, P = 0.011). Conclusions: The data obtained from ultra‐rapid high‐density automatic mapping is feasible and effective in identifying AF rotors/focal sources using PS technique, and those critical substrates were closely related to AF procedural termination. [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: Consistent detection of rotor(s) and/or focal impulse(s) of atrial fibrillation can using a 64-pole basket catheter remain unclear. Methods and results: Intracardiac left atrial electrograms were recorded, prior to ablation, in 20 patients with atrial fibrillation. Unipolar electrograms, filtered at 0.1–300 Hz, were recorded and exported for an offline phase analysis. From the cohort, 8 of the 20 patients had analyzable data. Localized rotors were identified in 3 of these patients, with focal impulses detected in 4 patients. Conclusion: Localized rotors and focal impulses can be identified on phase maps of atrial fibrillation in a small number of patients.

Background: A novel noninvasive epicardial and endocardial electrophysiology system (NEEES) to identify electrical rotors and focal activity in patients with atrial fibrillation (AF) was recently introduced. Comparison of NEEES data with results from invasive mapping is lacking.Methods: Six male patients (59 ± 11 years) with persistent AF underwent cardiac mapping with the NEEES, which included the creation of isopotential and phase maps. Then patients underwent catheter mapping using a PentaRay NAV catheter and the CARTO 3 system. Signals acquired by the catheter were analyzed by customized software that applied the same phase mapping algorithm as for the NEEES data.Results: In all patients, noninvasive phase mapping revealed short-lived electrical rotors occurring 1.8 ± 0.3 times per second and demonstrating 1-4 (mean 1.2 ± 0.6) rotation cycles. Most of these rotors (72.7%) aggregated in 2-3 anatomical clusters. In two patients, focal excitation from pulmonary veins was observed. Invasive catheter mapping in the dominant rotor aggregation sites and in the three control sites demonstrated the presence of electrical rotors with properties similar to noninvasively detected rotors. Spearman's correlation coefficient between rotor occurrence rate by noninvasive and invasive mapping was 0.97 (p < .0001). Mean rotors' cycle length at dominant aggregation sites, scores of their full rotations, and the proportion of rotors with clockwise rotation were not significantly different between the mapping modalities.Conclusion: In patients with persistent AF, phase processing of unipolar electrograms recorded by catheter mapping could reproduce electrical rotors as characterized by NEEES-based phase mapping. [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]

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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]

The diffraction patterns acquired with a transmission electron microscope (TEM) contain Bragg reflections related to all the crystals superimposed in the thin foil and crossed by the electron beam. Regarding TEM-based orientation and phase characterisation techniques, the nondissociation of these signals is usually considered as the main limitation for the indexation of diffraction patterns. A new method to identify the information related to the distinct but overlapped grains is presented. It consists in subtracting the signature of the dominant crystal before reindexing the diffraction pattern. The method is coupled to the template matching algorithm used in a standard automated crystal orientation mapping tool (ACOM-TEM). The capabilities of the approach are illustrated with the characterisation of a NiSi thin film stacked on a monocrystalline Si layer. Then, a subtracting-indexing cycle applied to a 70 nm thick thin foil containing polycrystalline tungsten electrical contacts shows the capability of the technique to recognise small nondominant grains. [ABSTRACT FROM AUTHOR]

Introduction Ventricular fibrillation is a common life-threatening arrhythmia. The ECG of VF appears chaotic but may allow identification of sustaining mechanisms to guide therapy. Hypothesis We hypothesized that rotors and focal sources manifest distinct features on the ECG, and computational modeling may identify mechanisms of such features. Methods VF induction was attempted in 31 patients referred for ventricular arrhythmia ablation. Simultaneous surface ECG and intracardiac electrograms were recorded using biventricular basket catheters. Endocardial phase maps were used to mechanistically classify each VF cycle as rotor or focally driven. ECGs were analyzed from patients demonstrating both mechanisms in the primary analysis and from all patients with induced VF in the secondary analysis. The ECG voltage variation during each mechanism was compared. Biventricular computer simulations of VF driven by focal sources or rotors were created and resulting ECGs of each VF mechanism were compared. Results Rotor-based VF exhibited greater voltage variation than focal source-based VF in both the primary analysis (n = 8, 110 ± 24% vs. 55 ± 32%, P = 0.02) and the secondary analysis (n = 18, 103 ± 30% vs. 67 ± 34%, P = 0.009). Computational VF simulations also revealed greater voltage variation in rotors compared to focal sources (110 ± 19% vs. 33 ± 16%, P = 0.001), and demonstrated that this variation was due to wavebreak, secondary rotor initiation, and rotor meander. Conclusion Clinical and computational studies reveal that quantitative criteria of ECG voltage variation differ significantly between VF-sustaining rotors and focal sources, and provide insight into the mechanisms of such variation. Future studies should prospectively evaluate if these criteria can separate clinical VF mechanisms and guide therapy. [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]