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BackgroundThe thickness and motion of the Interatrial Septum (IAS) possibly serves as indicators of both structural and functional remodeling of left atrium. This study aims to use transesophageal echocardiography (TEE) to assess IAS motion in non-valvular atrial fibrillation (NVAF) and investigate its correlation with the risk of spontaneous echo contrast (SEC) and thrombus (TH).MethodsWe conducted a cross-sectional study on 318 patients with NVAF who underwent transthoracic echocardiography and TEE. IAS motion was defined as the maximum displacement of IAS observed throughout the cardiac cycles using M-mode TEE.ResultsThe prevalence of SEC/TH was 39.9% (127/318) in the overall group. In paroxysmal atrial fibrillation (PAF), the prevalence rate of SEC/TH was 25.3% (47/186), compared to 60.6% (80/132) in persistent atrial fibrillation (PeAF). Multivariable analyses showed that LA volume index (LAVI), mean E/e’, S/D ratio, IAS motion and CHA2DS2-VASc scores were significantly associated with SEC/TH. Patients with lower IAS motion showed a higher prevalence of SEC/TH compared to those with higher IAS motion (71.3% vs. 11.6%; P

Purpose: Left atrial low-voltage areas (LA-LVAs) identified by 3D-electroanatomical mapping are crucial for determining treatment strategies and prognosis in patients with atrial fibrillation (AF). However, convenient and accurate prediction of LA-LVAs remains challenging. This study aimed to assess the viability of utilizing automatically obtained echocardiographic parameters to predict the presence of LA-LVAs in patients with non-valvular atrial fibrillation (NVAF). Patients and Methods: This retrospective study included 190 NVAF patients who underwent initial catheter ablation. Before ablation, echocardiographic data were obtained, left atrial volume and strain were automatically calculated using advanced software (Dynamic-HeartModel and AutoStrain). Electroanatomic mapping (EAM) was also performed. Results were compared between patients with LA-LVAs ≥ 5% (LVAs group) and < 5% (non-LVAs group). Results: LA-LVAs were observed in 81 patients (42.6%), with a significantly higher incidence in those with persistent AF than paroxysmal AF (55.6% vs 19.3%, P < 0.001). Compared with the non-LVAs group, the LVAs group included significantly older patients, lower left ventricular ejection fraction, higher heart rate, and higher E/e' ratio (P < 0.05). The LVAs group exhibited higher left atrial volumemax index (LAVimax) and lower left atrial reservoir strain (LASr) (P < 0.001). In multivariate analysis, both LAVimax and LASr emerged as independent indicators of LVAs (OR 0.85; 95% CI 0.80– 0.90, P< 0.001) and (OR 1.15, 95% CI 1.02– 1.29, P =0.021). ROC analysis demonstrated good predictive capacity for LA-LVAs, with an AUC of 0.733 (95% CI 0.650– 0.794, P < 0.001) for LAVimax and 0.839 (95% CI 0.779– 0.898, P < 0.001) for LASr. Conclusion: Automatic assessment of LAVimax and LASr presents a promising non-invasive modality for predicting the presence of LA-LVAs and evaluating significant atrial remodeling in NVAF patients. This approach holds potential for aiding in risk stratification and treatment decision-making, ultimately improving clinical outcomes in patients. [ABSTRACT FROM AUTHOR]

The energy of ring current protons is believed to influence the pitch angle scattering due to electromagnetic ion cyclotron (EMIC) waves and is typically analyzed using quasi‐linear theory. However, nonlinear behavior becomes significant as the wave amplitude intensifies. In this study, we aim to explore how the nonlinear behavior depends on the initial proton energy under various background plasma density conditions. The frequency of EMIC waves is 0.96ΩHe (where ΩHe is the gyrofrequency of He+ at the equator). It is found that the higher energy protons with nonlinear phase trapping experience more resonances, causing these trapped protons to move away from the loss cone more quickly compared to lower energy protons. However, the proportion of phase‐trapped protons significantly decreases as the initial proton energy increases. This declining trend is more pronounced for a background plasma condition in the plasmapause than within the plasmasphere. The number of phase‐trapped protons goes to zero as initial proton energy increases to above approximately 60 keV. Additionally, nonlinear phase bunching is more pronounced for lower energy protons (e.g., below 60 keV) compared to higher energy protons. As a result, both nonlinear phase trapping and phase bunching contribute to larger standard deviations in the net changes of equatorial pitch angle (Δαeq), suggesting a larger pitch agnel diffusion coefficient compared to the prediction of quasi‐linear theory. Key Points: The proportion of phase‐trapped protons is sensitive to changes in initial proton energy, and decreases as the initial proton energy increasesHigher energy protons with phase trapping experience more resonances, which will move quickly away from the loss coneTest‐particle pitch angle diffusion is more pronounced in lower energy protons (e.g., below 60 keV) compared to higher energy protons [ABSTRACT FROM AUTHOR]

Background/Aim: Mitral regurgitation (MR) is frequently observed in non‐valvular atrial fibrillation (NVAF) patients and is a significant risk factor for its progression. This study aims to investigate the three‐dimensional anatomical characteristics of the mitral valve (MV) in patients with different types of NVAF to elucidate the underlying mechanisms of MR. Methods: A retrospective analysis was conducted on 82 paroxysmal atrial fibrillation patients (PAF group) and 66 persistent atrial fibrillation patients (PerAF group) who underwent real‐time three‐dimensional transesophageal echocardiography (RT 3D‐TEE) before initial ablation. Additionally, 30 patients undergoing RT 3D‐TEE for the assessment of patent foramen ovale were selected as the control group. Basic echocardiographic variables were measured, left atrioventricular volume and strain parameters were calculated using automated software (Dynamic‐HeartModel and AutoStrain). MV anatomic features were analyzed using the 4D‐MV Assessment software (TomTec Imaging Systems). Results: The maximum left atrial volume (LAVmax) was highest in the PerAF group, followed by the PAF and control groups, with statistically significant differences (p < 0.01). Left atrial reservoir strain (LASr) showed an opposite trend, being the lowest in the PerAF group (p < 0.01). The proportion of moderate to severe MR was significantly higher in the PerAF group (27.3%) compared to the PAF group (11.0%) (p < 0.01). Compared to controls, the AF groups exhibited mitral annular (MA) dilation, flattening of the MA plane, and increased leaflet area (all p < 0.05). Correlation analysis between effective regurgitant orifice area (EROA) and left atrioventricular structure and function parameters, as well as various annular parameters, showed that EROA was significantly correlated with left ventricular end‐diastolic volume (LVEDV), LAVmax, LASr, anterior and posterior diameter, annular area, ratio of annular height to commissural diameter (AH/CD ratio), posterior leaflet area, posterior leaflet length, and the C‐shaped annulus length (all p < 0.05). Conclusions: Significant remodeling of the MV apparatus occurs in NVAF patients, with more pronounced changes in PerAF patients, contributing to a higher incidence of moderate to severe MR. RT 3D‐TEE‐based MV automated assessment offers significant advantages in accurately diagnosing MV remodeling and supporting the evaluation of MR in NVAF patients. [ABSTRACT FROM AUTHOR]

Background: Despite the efficacy of catheter ablation (CA) as a treatment for non-valvular atrial fibrillation (NVAF), many patients still experience atrial fibrillation (AF) recurrence after CA. This study aimed to evaluate the predictive value of speckle tracking echocardiographic (STE) parameters for AF recurrence post-ablation. Methods: A total of 380 NVAF patients treated with CA at the First Affiliated Hospital of Guangxi Medical University from January 2020 to March 2023 were prospectively recruited. The mean age was 59.4 ± 10.8 years, and 72.1% were male, including 150 patients (39.5%) with persistent AF and 230 patients (60.5%) with paroxysmal AF. STE was used to evaluate baseline left atrial (LA) function before CA within 48h. Over a median follow-up of 9 (interquartile range, 4– 17) months, AF recurrence occurred in 132 patients (34.7%). Results: The recurrence group showed lower left ventricular ejection fraction, LA reservoir strain (LASr), and conduit strain (LAScd), but higher LA stiffness than non- recurrence group (all P < 0.05). Multivariable Cox regression identified LA stiffness and LASr as independent risk factors. Time-dependent ROC analysis showed that LA stiffness (AUC 0.768, 95% CI 0.705– 0.831) and LASr (AUC 0.755, 95% CI 0.691– 0.820) were better at predicting 1-year AF recurrence than other risk factors. For 2-year AF recurrence post-catheter ablation, LA stiffness (AUC 0.866, 95% CI 0.804– 0.928) and LASr (AUC 0.860, 95% CI 0.800– 0.920) also demonstrated superior predictive performance. Kaplan-Meier curves showed a significant difference in AF recurrence rate for patients with LA stiffness > 0.55 and LASr ≤ 24.3% (Log rank P < 0.01). Conclusion: Evaluation of LA function using STE assists in stratifying the risk of AF recurrence in NVAF patients and guiding follow-up management. LASr and LA stiffness are independent predictors of AF recurrence following CA in NVAF patients, and potentially outperforming other morphological parameters. [ABSTRACT FROM AUTHOR]

The Tsinghua University–Ma Huateng Telescopes for Survey (TMTS) started to monitor the LAMOST plates in 2020, leading to the discovery of numerous short-period eclipsing binaries, peculiar pulsators, flare stars, and other variable objects. Here, we present the uninterrupted light curves for a sample of 64 cataclysmic variables (CVs) observed/discovered using the TMTS during its first three-year observations, and we introduce new CVs and new light-variation periods (from known CVs) revealed through the TMTS observations. Thanks to the high-cadence observations of TMTS, diverse light variations, including superhumps, quasi-periodic oscillations, large-amplitude orbital modulations, and rotational modulations, are able to be detected in our CV samples, providing key observational clues for understanding the fast-developing physical processes in various CVs. All of these short-timescale light-curve features help further classify the subtypes of CV systems. We highlight the light-curve features observed in our CV sample and discuss further implications of minute-cadence light curves for CV identifications and classifications. Moreover, we examine the Hα emission lines in the spectra from our nonmagnetic CV samples (i.e., dwarf novae and nova-like subclasses) and find that the distribution of Hα emission strength shows significant differences between the sources with orbital periods above and below the period gap, which agrees with the trend seen from the SDSS nonmagnetic CV sample. [ABSTRACT FROM AUTHOR]

Periodic variables are always of great scientific interest in astrophysics. Thanks to the rapid advancement of modern large-scale time-domain surveys, the number of reported variable stars has experienced substantial growth for several decades, which significantly deepened our comprehension of stellar structure and binary evolution. The Tsinghua University-Ma Huateng Telescopes for Survey (TMTS) has started to monitor the LAMOST sky areas since 2020, with a cadence of 1 min. During the period from 2020 to 2022, this survey has resulted in densely sampled light curves for ~30 000 variables of the maximum powers in the Lomb–Scargle periodogram above the 5σ threshold. In this paper, we classified 11 638 variable stars into six main types using xgboost and Random Forest classifiers with accuracies of 98.83 per cent and 98.73 per cent, respectively. Among them, 5301 (45.55 per cent) variables are newly discovered, primarily consisting of δ Scuti stars, demonstrating the capability of TMTS in searching for short-period variables. We cross-matched the catalogue with Gaia 's second Data Release and LAMOST's seventh Data Release to obtain important physical parameters of the variables. We identified 5504 δ Scuti stars (including 4876 typical δ Scuti stars and 628 high-amplitude δ Scuti stars), 5899 eclipsing binaries (including EA-, EB-, and EW-type), and 226 candidates of RS Canum Venaticorum. Leveraging the metal abundance data provided by LAMOST and the Galactic latitude, we discovered eight candidates of SX Phe stars within the class of 'δ Scuti stars'. Moreover, with the help of Gaia colour–magnitude diagram, we identified nine ZZ Ceti stars. [ABSTRACT FROM AUTHOR]

We present 206 unpublished optical spectra of 104 type II supernovae (SNe II) obtained by the Xinglong 2.16-m telescope and Lijiang 2.4-m telescope during the period from 2011 to 2018, spanning the phases from about 1 to 200 d after the SN explosion. The spectral line identifications, evolution of line velocities and pseudo-equivalent widths, as well as correlations between some important spectral parameters are presented. Our sample displays a large range in expansion velocities. For instance, the Fe  ii 5169 velocities measured from spectra at t ∼ 50 d after the explosion vary from 2000 to 5500 km s−1, with an average value of 3872 ± 949 km s−1. Power-law functions can be used to fit the velocity evolution, with the power-law exponent quantifying the velocity decline rate. We found an anticorrelation existing between H β velocity at mid-plateau phase and its velocity decay exponent, SNe II with higher velocities tending to have smaller velocity decay rate. Moreover, we noticed that the velocity decay rate inferred from the Balmer lines (i.e. H α and H β) have moderate correlations with the ratio of absorption to emission for H α (a/e). In our sample, two objects show possibly flash-ionized features at early phases. Besides, we noticed that multiple high-velocity components may exist on the blue side of hydrogen lines of SN 2013ab, possibly suggesting that these features arise from complex line-forming region. [ABSTRACT FROM AUTHOR]

We present extensive photometric and spectroscopic observations of the peculiar Type Ia supernova (SN Ia) 2022vqz. It shares many similarities with the SN 2002es-like SNe Ia, such as low luminosity (⁠|$M_{B,\rm max}=-18.11\pm 0.16$| mag) and moderate post-peak decline rate (Δ m 15, B  = 1.33 ± 0.11 mag). The nickel mass synthesized in the explosion is estimated as 0.20 ± 0.04 M⊙ from the bolometric light curve, which is obviously lower than that of normal SNe Ia. SN 2022vqz is also characterized by slowly expanding ejecta, with Si  ii velocities persisting around 7000 km s−1 since 16 d before peak brightness, unique among all known SNe Ia. While all of these properties imply a lower energy thermonuclear explosion that should leave a considerable amount of unburnt materials, the absent signature of unburnt carbon in spectra of SN 2022vqz is puzzling. A prominent early peak is clearly detected in the Asteroid Terrestrial-impact Last Alert System c - and o -band light curves and in the Zwicky Transient Facility gr -band data within days after the explosion. Possible mechanisms for the early peak are discussed, including the sub-Chandrasekhar-mass double-detonation model and interaction of SN ejecta with circumstellar material. We find that both models face some difficulties in replicating all aspects of the observed data. As an alternative, we propose a hybrid C–O–Ne white dwarf as the progenitor of SN 2022vqz; it can simultaneously reconcile the tension between low ejecta velocity and the absence of carbon. We further discuss the diversity of SN 2002es-like objects and their origin in the context of different scenarios. [ABSTRACT FROM AUTHOR]

SN 2019neq was a very fast evolving superluminous supernova. At a redshift z  = 0.1059, its peak absolute magnitude was −21.5 ± 0.2 mag in g band. In this work, we present data and analysis from an extensive spectrophotometric follow-up campaign using multiple observational facilities. Thanks to a nebular spectrum of SN 2019neq, we investigated some of the properties of the host galaxy at the location of SN 2019neq and found that its metallicity and specific star formation rate are in a good agreement with those usually measured for SLSNe-I hosts. We then discuss the plausibility of the magnetar and the circumstellar interaction scenarios to explain the observed light curves, and interpret a nebular spectrum of SN 2019neq using published sumo radiative-transfer models. The results of our analysis suggest that the spin-down radiation of a millisecond magnetar with a magnetic field |$B\simeq 6\times 10^{14}\, \mathrm{G}$| could boost the luminosity of SN 2019neq. [ABSTRACT FROM AUTHOR]

Background: Rheumatic mitral stenosis(RMS) may leads to left ventricular remodeling (LVR), which can persist even after valve surgery. Identifying markers for early structure and function in patients with rheumatic heart disease who are at risk for adverse LVR after surgery can help determine the optimal timing of intervention. This study aimed to investigate whether preoperative parameters of global left ventricular long-axis strain (LVGLS) and mechanical discretization (MD) could predict postoperative adverse LVR.Methods: A total of 109 adult patients with RMS and 50 healthy controls were enrolled in this study. Baseline clinical features, conventional echocardiography results, LVGLS, and MD were compared between the two groups. Pre- and post-surgery echocardiography measurements were collected, and adverse LVR was defined as a> 15% increase in left ventricular end-diastolic volume or > 10% decrease in left ventricular ejection fraction. Binary regression analysis was used to determine independent predictors of poor left ventricular remodeling.Results: The variables associated with adverse LVR in this study were LVGLS (P< 0.001, odds ratio: 1.996, 95% CI: 1.394– 2.856) and MD (P=0.011, odds ratio: 1.031, 95% CI: 1.007– 1.055). The poorly reconstructed group had lower absolute values of LVGLS and higher MD than the healthy control group and the non-poorly reconstructed group. A LVGLS cutoff of − 15.0% was the best predictor for patients with poorly reconstructed LVR (sensitivity: 75.7%; specificity: 100.0%; AUC: 0.93), and a MD cutoff of 63.8ms was the best predictor (sensitivity: 63.8%; specificity: 98.6%; AUC: 0.88).Conclusion: Speckle tracking echocardiography has potential value for predicting the progression of adverse LVR and for identifying non-responders among patients with RMS undergoing surgery. [ABSTRACT FROM AUTHOR]

Over the past few years, wide-field time-domain surveys such as Zwicky Transient Facility and Optical Gravitational Lensing Experiment have led to discoveries of various types of interesting short-period stellar variables, such as ultracompact eclipsing binary white dwarfs (WDs), rapidly rotating magnetized WDs, transitional cataclysmic variables between hydrogen-rich and helium accretion, and blue large-amplitude pulsators (BLAPs), which greatly enrich our understandings of stellar physics under some extreme conditions. In this paper, we report the first-2-yr discoveries of short-period variables (i.e. P < 2 h) by the Tsinghua University–Ma Huateng Telescopes for Survey (TMTS). TMTS is a multitube telescope system with a field of view up to 18 deg2, which started to monitor the Large Sky Area Multi-object Fiber Spectroscopic Telescope (LAMOST) sky areas since 2020 and generated uninterrupted minute-cadence light curves for about 10 million sources within 2 yr. Adopting the Lomb–Scargle periodogram with period-dependent thresholds for the maximum powers, we identify over 1100 sources that exhibit a variation period shorter than 2 h. Compiling the light curves with the Gaia magnitudes and colours, LAMOST spectral parameters, International Variable Star Index classifications, and archived observations from other prevailing time-domain survey missions, we identified 1076 as δ Scuti stars, which allows us to study their populations and physical properties in the short-period regime. The other 31 sources include BLAPs, subdwarf B variables, pulsating WDs, ultracompact/short-period eclipsing/ellipsoidal binaries, cataclysmic variables below the period gap, etc. which are highly interesting and worthy of follow-up investigations. [ABSTRACT FROM AUTHOR]

Tsinghua University-Ma Huateng Telescopes for Survey (TMTS) aims to detect fast-evolving transients in the Universe, which has led to the discovery of thousands of short-period variables and eclipsing binaries since 2020. In this paper, we present the observed properties of 125 flare stars identified by TMTS within the first two years, with an attempt to constrain their eruption physics. As expected, most of these flares were recorded in late-type red stars with G BP − G RP >2.0 mag; however, the flares associated with bluer stars tend to be on average more energetic and have broader profiles. The peak flux (F peak) of the flare is found to depend strongly on the equivalent duration (ED) of the energy release, i.e. F peak∝ED0.72 ± 0.04, which is consistent with results derived from the Kepler and Evryscope samples. This relation is likely to be related to the magnetic loop emission, while, for the more popular non-thermal electron heating model, a specific time evolution may be required to generate this relation. We notice that flares produced by hotter stars have a flatter F peak - ED relation compared to that from cooler stars. This is related to the statistical discrepancy in light-curve shape of flare events with different colours. In spectra from LAMOST, we find that flare stars have apparently stronger H α emission than inactive stars, especially at the low-temperature end, suggesting that chromospheric activity plays an important role in producing flares. On the other hand, the subclass with frequent flares is found to show H α emission of similar strength in its spectra to that recorded with only a single flare but similar effective temperature, implying that chromospheric activity may not be the only trigger for eruptions. [ABSTRACT FROM AUTHOR]

In the last 20 years, modern wide-field surveys discovered a new class of peculiar transients, which lie in the luminosity gap between standard supernovae and classical novae. These transients are often called "intermediate luminosity optical transients" or "gap transients". They are usually distinguished in subgroups based on their phenomenology, such as supernova impostors, intermediate luminosity red transients, and luminous red novae. In this review, we present a brief overview of their observational features and possible physical scenarios to date, in the attempt to understand their nature. [ABSTRACT FROM AUTHOR]

Early-time radiative signals from Type Ia supernovae (SNe Ia) can provide important constraints on the explosion mechanism and the progenitor system. We present observations and analysis of SN 2019np, a nearby SN Ia discovered within 1–2 days after the explosion. Follow-up observations were conducted in optical, ultraviolet, and near-infrared bands, covering the phases from ∼−16.7 d to ∼+ 367.8 d relative to its B -band peak luminosity. The photometric and spectral evolutions of SN 2019np resemble the average behaviour of normal SNe Ia. The absolute B -band peak magnitude and the post-peak decline rate are M max(B) = −19.52 ± 0.47 mag and Δ m 15(B) = 1.04 ± 0.04 mag, respectively. No Hydrogen line has been detected in the nebular-phase spectra of SN 2019np. Assuming that the 56Ni powering the light curve is centrally located, we find that the bolometric light curve of SN 2019np shows a flux excess up to 5.0 per cent in the early phase compared to the radiative diffusion model. Such an extra radiation perhaps suggests the presence of an additional energy source beyond the radioactive decay of central nickel. Comparing the observed colour evolution with that predicted by different models, such as interactions of SN ejecta with circumstellar matter (CSM)/companion star, a double-detonation explosion from a sub-Chandrasekhar mass white dwarf (WD) and surface 56Ni mixing, we propose that the nickel mixing is more favoured for SN 2019np. [ABSTRACT FROM AUTHOR]

We present multiband photometric and spectroscopic observations of the type II supernova, (SN) 2019va, which shows an unusually flat plateau-phase evolution in its V -band light curve. Its pseudo-bolometric light curve even shows a weak brightening towards the end of the plateau phase. These uncommon features are related to the influence of 56Ni decay on the light curve during the plateau phase, when the SN emission is usually dominated by cooling of the envelope. The inferred 56Ni mass of SN 2019va is 0.088 ± 0.018 M⊙, which is significantly larger than most SNe II. To estimate the influence of 56Ni decay on the plateau-phase light curve, we calculate the ratio (dubbed as ηNi) between the integrated time-weighted energy from 56Ni decay and that from envelope cooling within the plateau phase, obtaining a value of 0.8 for SN 2019va, which is the second largest value among SNe II that has been measured. After removing the influence of 56Ni decay on the plateau-phase light curve, we found that the progenitor/explosion parameters derived for SN 2019va are more reasonable. In addition, SN 2019va is found to have weaker metal lines in its spectra compared to other SNe IIP at similar epochs, implying a low-metallicity progenitor, which is consistent with the metal-poor environment inferred from the host-galaxy spectrum. We further discuss the possible reasons that might lead to SN 2019va-like events. [ABSTRACT FROM AUTHOR]

A MEMS-based micro valve fitted with a piezoelectric actuator is presented in order to achieve a continuously adjustable flow rate control. The micro valve is realized using a cost-effective fabrication scheme with simple polyimide (PI) bonding, which has an average shear strength of up to 39.8 MPa, indicating a relatively high reliability. The simulation results based on the finite element method (FEM) show that the valve membrane is able to seal the inlet and cut off the flow successfully with a piezoelectric force of 3N when the differential pressure is 200 kPa. The measurement of the flow rate through the outlets shows that the micro valve can control the flow rate effectively in a large range under different actuation voltages and differential pressures. When the actuation voltage is 140 V, the measured leak flow of the closed micro valve is smaller than 0.5 sccm with a differential pressure of 200 kPa. [ABSTRACT FROM AUTHOR]

Nitrogen dioxide (NO2) is very toxic and harmful to humans and the environment; therefore, it is essential to develop a sensor for the detection of NO2 gas. In this paper, a NO2 sensing device was fabricated based on a Au-decorated ZnO/rGO heterostructure, which achieved a remarkable sensing response of 67.38 to 1 ppm NO2 and a notably low theoretical detection limit of 138 parts per trillion (ppt) at a low working temperature of 60 °C. Here, we demonstrate a synthesis approach involving Au decoration on the surface of the ZnO/rGO heterojunction. The chemical, morphological, structural, and electrical properties of the Au@ZnO/rGO heterostructure were studied through various characterization techniques. The Au@ZnO/rGO nanocomposite-based sensor exhibited good linearity and time constants of 248 s and 170 s during the adsorption and desorption of NO2 gas. Moreover, the Au@ZnO/rGO nanocomposite sensor demonstrated outstanding selectivity towards 1 ppm NO2, which is significantly higher than that of other interfering gases, indicating its potential for use in NO2 gas detection. The exceptional sensing response is attributed to the higher catalytic activity or synergistic effect between Au and the ZnO/rGO heterostructure. This study delivers an effective method for improving the sensing performance of metal oxide-based nanomaterials. [ABSTRACT FROM AUTHOR]

We present optical and ultraviolet photometry, as well as optical spectra, for the type II supernova (SN) 2015bf. Our observations cover the phases from ∼2 to ∼200 d after explosion. The first spectrum is characterized by a blue continuum with a blackbody temperature of ∼24 000 K and flash-ionized emission lines. After about 1 week, the spectra of SN 2015bf evolve like those of a regular SN II. From the luminosity of the narrow emission component of H α, we deduce that the mass-loss rate is larger than |${\sim}3.7\times 10^{-3}\, {\rm M_\odot \, yr^{-1}}$|⁠. The disappearance of the flash features in the first week after explosion indicates that the circumstellar material is confined within ∼6 × 1014 cm. Thus, we suggest that the progenitor of SN 2015bf experienced violent mass loss shortly before the supernova explosion. The multiband light curves show that SN 2015bf has a high peak luminosity with an absolute visual magnitude MV  = −18.11 ± 0.08 mag and a fast post-peak decline with a V -band decay of 1.22 ± 0.09 mag within ∼50 d after maximum light. Moreover, the R -band tail luminosity of SN 2015bf is fainter than that of SNe II with similar peak by 1–2 mag, suggesting a small amount of 56Ni (⁠|${\sim}0.009\, {\rm M_\odot }$|⁠) synthesized during the explosion. Such a low nickel mass indicates that the progenitor of SN 2015bf could be a super-asymptotic-giant-branch star that collapsed owing to electron capture. [ABSTRACT FROM AUTHOR]

Overvoltages are the main causes of damages and accidents in electric power grids. The traditional approach is to install some static protection devices that are passive and cannot identify the overvoltage types or locate where the overvoltage event occurs. In recent years, with the development of smart grids, some online overvoltage monitoring systems have been developed. However, the approaches to data processing still need further development. A novel technique for identification and location of overvoltages in power distribution systems is proposed, which uses capacitor bank energization overvoltages (CBOVs) and ground fault temporary overvoltages (TOVs) as the study cases. The wavelet packet decomposition (WPD) theory is used for frequency band decomposition, and a general regression neural network (GRNN) is used in identification and location. Simulation results based on real-world power distribution systems show that the method is accurate and fast. [ABSTRACT FROM PUBLISHER]

The rapid development of Internet Plus Smart Energy requires further strengthening of three kinds of interconnections based on traditional power systems: physical interconnection, information interconnection, and commercial interconnection. Due to the integration of renewable energy, the reform of the electricity market, and the deployment of the Smart Grid, a large amount of data will be generated. Thus, it is necessary to establish a Ubiquitous Power Internet of Things (UPIoT) to realize connections among people and things, things and things, and people and people in power systems. This paper studies the concept and architecture of the UPIoT and indicates the deployment of the perception layer and network layer as the key to building UPIoT in the initial stage. As UPIoT tends to cover a wide area and produce massive and distributed data, signal processing and data analytics theories and techniques are needed to handle the data and observe the state of the large-scale system. Further studies on distributed sensing and cooperative estimation theories and techniques of UPIoT are also required. Finally, the application prospects of UPIoT and the directions for future research are discussed. [ABSTRACT FROM AUTHOR]