Low dimensional materials have been examined as electrocatalysts for the hydrogen evolution reaction (HER). Among them, two-dimensional Transition Metal Dichalcogenides (2D-TMDs) such as MoS 2 have been identified as potential candidates. However, the performance of TMDs towards HER in both acidic and basic media remains inferior to that of noble metals such as Pt and its alloys. This calls for investigating the influence of controlled defect engineering of 2D Hydrothermal synthesis 6.5ű0.04

Text-based question answering (TBQA) has been studied extensively in recent years. Most existing approaches focus on finding the answer to a question within a single paragraph. However, many difficult questions require multiple supporting evidence from scattered text across two or more documents. In this paper, we propose the Dynamically Fused Graph Network (DFGN), a novel method to answer those questions requiring multiple scattered evidence and reasoning over them. Inspired by human's step-by-step reasoning behavior, DFGN includes a dynamic fusion layer that starts from the entities mentioned in the given query, explores along the entity graph dynamically built from the text, and gradually finds relevant supporting entities from the given documents. We evaluate DFGN on HotpotQA, a public TBQA dataset requiring multi-hop reasoning. DFGN achieves competitive results on the public board. Furthermore, our analysis shows DFGN could produce interpretable reasoning chains.

Time-resolved fluorescence properties of quenched fluorescein sodium, including self-quenching and collisional quenching by iodide, have been studied by using a picosecond time-correlated single-photon counting (TCSPC) apparatus, together with an upconversion spectrophotofluorometer with a time resolution better than 300 fs. The steady-state fluorescence intensity of fluorescein sodium reached the maximum when its concentration was 510 μM with pH > 9. Both the fluorescence intensity and lifetime decreased with increasing concentrations of NaI quencher. When the NaI concentration was 12.2 M, a monoexponential decay with a lifetime as short as 17 ps was exactly determined for the first time using the femtosecond-resolved upconversion system. Picosecond time-resolved fluorescence measurements of circular permuted green and yellow fluorescent proteins (cpGFP and cpYFP) were reported, demonstrating that the fluorescence decay of quenched fluorescein sodium is a better approximation of the instrument response function (IRF) needed for the accurate deconvolution of fluorescence lifetime data, particularly for detectors used in the visible spectral region. We believe that this picosecond lifetime standard will find wide applications in fluorescence lifetime imaging microscopy (FLIM).

Using a total of 9.0 fb −1 of e + e − collision data with center-of-mass energies between 4.15 and 4.30 GeV collected by the BESIII detector, we search for the processes e + e − → γX(3872) with X(3872) → π 0 χcJ for J = 0, 1, 2. We report the first observation of X(3872) → π 0 χc1, a new decay mode of the X(3872), with a statistical significance of more than 5σ. Normalizing to the previously established process e + e − → γX(3872) with X(3872) → π + π − J/ψ, we find B(X(3872) → π 0 χc1)/B(X(3872) → π + π − J/ψ) = 0.88 +0.33 −0.27 ±0.10, where the first error is statistical and the second is systematic. We set 90% confidence level upper limits on the corresponding ratios for the decays to π 0 χc0 and π 0 χc2 of 19 and 1.1, respectively.

No abstract

No abstract

No abstract

A high-power 1064 nm single-frequency polarization-maintained fiber amplifier based on an all-fiber master oscillator power amplifier configuration is demonstrated. To mitigate the stimulated Brillouin scattering (SBS) and the mode instability (MI) effect, a polarization-maintained Yb-doped fiber with a high dopant concentration and a 25 μm core diameter is adopted in the main amplifier stage; in addition, step-distributed longitudinal strain is imposed on the active fiber to broaden its effective SBS gain spectrum and further increase the SBS threshold. As a result, a pump-limited 414 W single-frequency fiber laser is obtained without signs of SBS and MI. Experimental results show that the SBS threshold is increased by at least two times. The slope efficiency of the main amplifier is about 80%. The polarization degree is higher than 98% at all the power levels. The beam quality is measured with a M² of 1.34. To the best of our knowledge, this is the highest output power of single-frequency polarization-maintained fiber amplifier based on an all-fiber structure.