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Voice activity detection (VAD) is essential for multiple microphone arrays processing, in which massive potential devices, such as microphone devices for far-field voice-based interaction in smart home environments, will be activated when sound sources appear. Therefore, the VAD can save a lot of computing resources in massive microphone arrays processing for the sparsity in sound source activity. However, it may not be feasible to obtain an accurate VAD in harsh environments, such as far-field, time-varying noise field. In this paper, the long-term speech information (LTSI) and the log-energy are modeled for deriving a more accurate VAD. First, the LTSI can be obtained by measuring the differential entropy of long-term smoothed noisy signal spectrum. Then, the LTSI is used to get labeled data for the initialization of a Gaussian mixture model (GMM), which is used to fit the log-energy distribution of noise and (noisy) speech. Finally, combining the LTSI and the GMM parameters of noise and speech distribution, this paper derives an adaptive threshold, which represents a reasonable boundary between noise and speech. Experimental results show that our VAD method has a remarkable improvement for a massive microphone network.

Peroxynitrite (ONOO−) is a kind of reactive oxygen species (ROS) which is associated with pathogenesis of many diseases. A new near-infrared fluorescence probe (DCM-OH) which based on dicyanomethylene-4H-pyrans to detect endogenous ONOO− was designed and synthesized. The two-photon absorption cross sections and large Stokes shift make the probe deeper issue penetration and lower self-absorption. The obtained results demonstrated that probe DCM-OH could sensitively detect ONOO− with a low detection limit (53 nM). What's more, probe DCM-OH exhibited an ultrafast response rate (within 5 s) toward ONOO−, which would be in favor of tracking the highly reactive and short-lived ONOO− in the living systems. Moreover, DCM-OH was successfully employed for imaging endogenous ONOO− in HepG2/RAW 264.7 cells and further applied to visualize oxidative stress in mouse model of inflammation.

Knowledge of the adsorption reactions between serine and minerals is critical to understanding the geochemical processes of amino acids (i.e., mobility, bioavailability, and degradation) in the environment. Attenuated total reflectance Fourier-transform infrared (ATR-FTIR) flow-cell measurements were used to distinguish the inner- and outer-sphere complexation and reveal the dynamic adsorption and desorption processes of each surface complex at the molecular level. Density functional theory (DFT) calculations were applied to determine the structures of the surface complexes and to justify the peak assignments of the serine dissolved in solution and adsorbed on TiO2. The structures of interfacial serine were governed by pH conditions but were not affected by the changes in adsorption time and serine concentration. The ATR-FTIR spectra and the results of DFT calculations resolved two different bidentate inner-sphere coordination, involving the COO− group of the serine zwitterion at pH 4–8 and the serine anion at pH 10. The dynamic adsorption processes of these two surface complexes conformed to the pseudo-second-order kinetic model. The stable inner-sphere complexation could not be entirely removed from the TiO2 surface upon serine desorption. In addition to reducing the migration rate in the environment, the bidentate inner-sphere coordination contributes to the potential degradation of the serine NH3+ and NH2 groups. Our research provides new insights into serine adsorption and desorption, facilitating further understanding of the fate and transport of amino acids in the environment.

A BODIPY-based mitochondria-targeted fluorescent probe (BODIPY-DMTC) was synthesized for selective determination of hypochlorite (ClO−) over other reactive oxygen species (ROS) or reactive nitrogen species (RNS). The phenolic hydroxyl protecting group dimethylthiocarbamates (DMTC) was introduced to BODIPY framework, specifically recognizing exogenous and endogenous ClO− by the “deprotection” of hydroxyl group. The response process was monitored in real-time by titration assays of mass spectra and 1H NMR. The emission response of probe to ClO− presented a good linear relationship in 0–100 μM concentration range, and the detection limit of 95 nM was observed. Also, the current probe was used to successfully visualize endogenous ClO− in zebrafish embryos.

A series of xanthone derivatives were synthesized by rhodium-catalyzed cycloaddition and sequential oxidation. The derivatives synthesized for excellent yields, including electron-withdrawing and electron-donating substituents, demonstrated the wide applicability of the proposed approach. The xanthones synthesized with different substituent electron effects may go through the same intermediate via two cycloadditions. It is highlighted that the protocol was exemplified by its successful integration into a one-pot synthesis directly from 1-ethynyl-2-phenoxybenzene. We believe that the current method may be an attractive option for the synthesis of xanthone and its derivatives.

SiO2 has attracted considerable attention for the application of next-generation lithium-ion batteries (LIBs) because of its evident merits, such as large capacity, high natural abundance and low price. Nevertheless, the huge volume inflation and inferior electronic conductivity lead to material degradation and hamper its extensive use. To resolve these challenges, a series of SiO2-M-C (M = Fe, Ni, Cu, C = acetylene black) composites are prepared via a straightforward high energy mechanical milling (HEMM) method. Herein, the M nanoparticles can boost the electronic conductivity and ameliorate electrochemical activity of SiO2 through the catalytic effect of M in breaking Si-O and Li-O bonds, while C can offer a highly conducting assistance to effectively deter agglomeration and pulverization of SiO2 nanoparticles. Superiorly, SiO2-Fe-C reveals exceptional performances with a high initial Coulombic efficiency (CE) of 70.4% at 0.2 A g−1 and long cycle stability under different high current densities (335.6 mAh g−1 at 2 A g−1, 2000 cycles; 212 mAh g−1 at 5 A g−1, 5000 cycles, respectively), which surpasses the reported SiO2-based materials. Considering the convenient preparation and outstanding properties, SiO2-Fe-C can be of visible significance for practical application in next-generation LIBs.