Polyoxometalatocrown ether: A new type of metallacrown ether based on polyoxometalate

Using chain-like polyethers consisting of two terminal –NH2 groups and (TBA)4[α-Mo8O26] as starting materials, two polyoxometalatocrown ethers were prepared by a cyclization reaction through the formation of Mo≡N triple bonds: (TBA)2[Mo6O17N(o-C6H4OCH2(CH2OCH2)nCH2OC6H4-o)N] (compounds 1, n = 1; 2, n = 2). As confirmed by single-crystal X-ray diffraction and infrared (IR) studies, the polyoxometalatocrown ether 2 can capture primary ammonium cations in solid state

Application of Deep Learning Methods for Distinguishing Gamma-Ray Bursts from Fermi/GBM TTE Data

To investigate GRBs in depth, it is crucial to develop an effective method for identifying GRBs accurately. Current criteria, e.g., onboard blind search, ground blind search, and target search, are limited by manually set thresholds and perhaps miss GRBs, especially for sub-threshold events. We propose a novel approach that utilizes convolutional neural networks (CNNs) to distinguish GRBs and non-GRBs directly. We structured three CNN models, plain-CNN, ResNet, and ResNet-CBAM, and endeavored to exercise fusing strategy models. Count maps of NaI detectors onboard Fermi/GBM were employed as the input samples of datasets and models were implemented to evaluate their performance on different time scale data. The ResNet-CBAM model trained on 64 ms dataset achieves high accuracy overall, which includes residual and attention mechanism modules. The visualization methods of Grad-CAM and t-SNE explicitly displayed that the optimal model focuses on the key features of GRBs precisely. The model was applied to analyze one-year data, accurately identifying approximately 98% of GRBs listed in the Fermi burst catalog, 8 out of 9 sub-threshold GRBs, and 5 GRBs triggered by other satellites, which demonstrated the deep learning methods could effectively distinguish GRBs from observational data. Besides, thousands of unknown candidates were retrieved and compared with the bursts of SGR J1935+2154 for instance, which exemplified the potential scientific value of these candidates indeed. Detailed studies on integrating our model into real-time analysis pipelines thus may improve their accuracy of inspection, and provide valuable guidance for rapid follow-up observations of multi-band telescopes.Comment: accepted for publication in ApJSS. 45 pages,17 figure

Prompt-to-afterglow transition of optical emission in a long gamma-ray burst consistent with a fireball

Long gamma-ray bursts (GRBs), which signify the end-life collapsing of very massive stars, are produced by extremely relativistic jets colliding into circumstellar medium. Huge energy is released both in the first few seconds, namely the internal dissipation phase that powers prompt emissions, and in the subsequent self-similar jet-deceleration phase that produces afterglows observed in broad-band electromagnetic spectrum. However, prompt optical emissions of GRBs have been rarely detected, seriously limiting our understanding of the transition between the two phases. Here we report detection of prompt optical emissions from a gamma-ray burst (i.e. GRB 201223A) using a dedicated telescope array with a high temporal resolution and a wide time coverage. The early phase coincident with prompt {\gamma}-ray emissions show a luminosity in great excess with respect to the extrapolation of {\gamma}-rays, while the later luminosity bump is consistent with onset of the afterglow. The clearly detected transition allows us to differentiate physical processes contributing to early optical emissions and to diagnose the composition of the jetComment: Authors' version of article published in Nature Astronomy, see their website for official versio

Dopant-Free Donor (D)–p–D–p–D Conjugated Hole- Transport Materials for Efficient and Stable Perovskite Solar Cells

Three novel hole-transporting materials (HTMs) using the 4-methoxytriphenylamine (MeOTPA) core were designed and synthesized. The energy levels of the HTMs were tuned to match the perovskite energy levels by introducing symmetrical electron-donating groups linked with olefinic bonds as the bridge. The methylammonium lead triiodide (MAPbI(3)) perovskite solar cells based on the new HTM Z34 (see main text for structure) exhibited a remarkable overall power conversion efficiency (PCE) of 16.1% without any dopants or additives, which is comparable to 16.7% obtained by a p-doped 2,2,7,7-tetrakis-(N,N-di-4-methoxyphenylamino)-9,9-spirobifluorene (spiro-OMeTAD)-based device fabricated under the same conditions. Importantly, the devices based on the three new HTMs show relatively improved stability compared to devices based on spiro-OMeTAD when aged under ambient air containing 30% relative humidity in the dark

Over 20% PCE perovskite solar cells with superior stability achieved by novel and low-cost hole-transporting materials

The exploration of alternative low-cost molecular hole-transporting materials (HTMs) for both highly efficient and stable perovskite solar cells (PSCs) is a relatively new research area. Two novel HTMs using the thiophene core were designed and synthesized (Z25 and Z26). The perovskite solar cells based on Z26 exhibited a remarkable overall power conversion efficiency (PCE) of 20.1%, which is comparable to 20.6% obtained with spiroOMeTAD. Importantly, the devices based-on Z26 show better stability compared to devices based on Z25 and spiroOMeTAD when aged under ambient air of 30% or 85% relative humidity in the dark and under continuous full sun illumination at maximum power point tracking respectively. The presented results demonstrate a simple strategy by introducing double bonds to design hole-transporting materials for highly efficient and stable perovskite solar cells with low cost, which is important for commercial application

AMS measurement of 53Mn and its initial application at CIAE

The determination of cosmogenic 53Mn in terrestrial archives has important applications, such as burial ages, exposure age and erosion rates. Accelerator mass spectrometry (AMS) is the most sensitive technique to detect minute amounts of 53Mn. 53Mn measurements were developed at the China Institute of Atomic nergy (CIAE) using the DE-Q3D equipped AMS system. This approach was recently optimized with the goal to reach the sensitivity required for AMS measurements of 53Mn in deep-sea ferromanganese crust (DSFC) samples. Based on these improvements of sample preparation, current beam transmission and so on, 53Mn in two samples of DSFC was measured by AMS. The ratios of 53Mn/Mn corresponding to an age of 3.77 ± 0.42 and 13.73 ± 2.74 Ma by 129I dating method are (5.01 ± 2.15) 10 13 and (1.90 ± 0.96) 10 13. The ratios are close to the experimental reference values, deduced from the previous research. The experimental progress, performances and results are presented in this contribution.This work was mainly supported by the National Natural Science Foundations of China (NSFC), under Grant No. 11075221, and a partly supported by the National Natural Science Foundation of China under Grant Nos. 10705054, 41073044 and 11265005

Lick Observatory Supernova Search Follow-Up Program: Photometry Data Release of 93 Type Ia Supernovae

We present BVRI and unfiltered light curves of 93 Type Ia supernovae (SNe Ia) from the Lick Observatory Supernova Search (LOSS) follow-up program conducted between 2005 and 2018. Our sample consists of 78 spectroscopically normal SNe Ia, with the remainder divided between distinct subclasses (three SN 1991bg-like, three SN 1991T-like, four SNe Iax, two peculiar, and three super-Chandrasekhar events), and has a median redshift of 0.0192. The SNe in our sample have a median coverage of 16 photometric epochs at a cadence of 5.4 days, and the median first observed epoch is ~4.6 days before maximum B-band light. We describe how the SNe in our sample are discovered, observed, and processed, and we compare the results from our newly developed automated photometry pipeline to those from the previous processing pipeline used by LOSS. After investigating potential biases, we derive a final systematic uncertainty of 0.03 mag in BVRI for our dataset. We perform an analysis of our light curves with particular focus on using template fitting to measure the parameters that are useful in standardising SNe Ia as distance indicators. All of the data are available to the community, and we encourage future studies to incorporate our light curves in their analyses.Comment: 29 pages, 13 figures, accepted for publication in MNRA