Search

Research of thermally activated delayed fluorescence (TADF) and room‐temperature phosphorescence (RTP) materials is attractive owing to their extensive applications in various fields. However, achieving organic TADF and RTP materials, particularly those with stimulus‐responsiveness and tunability, is highly desirable but challenging and rarely reported. Herein, two easily synthesized organic molecules are reported with abnormal stimulus‐responsive switchable TADF and RTP effects, in which phenothiazine (PTZ) and benzo[b]phenothiazine (BPTZ) based donor−acceptor molecules PTZ‐DBQ and BPTZ‐DBQ show mechanical‐induced TADF in crystalline phase and photo‐responsive RTP in doping poly(methyl methacrylate) (PMMA) films. This is the first time tetracyclic BPTZ has been used as a donor in achieving TADF and RTP materials, and it is found that BPTZ‐DBQ exhibits remarkably better photophysical properties than PTZ‐DBQ. Systematic studies of experimental results and theoretical calculations indicate that the conformational heterogeneity plays an essential role in achieving mechanical‐induced TADF with mechanochromic luminescence (MCL) property. Embedding the organic phosphors into rigid polymer matrices effectively suppresses the molecular motion, thus turning on the RTP emission channel. The conversion of 3O2 to 1O2 under UV irradiation is mainly responsible for the photo‐induced process. These multifunctional luminescent materials have great potential applications in chemical sensors, information encryption, and anti‐counterfeiting. [ABSTRACT FROM AUTHOR]

Two-stream convolution network (2SCN) is a classical method of action recognition. It is capable of extracting action information from two dimensions: spatial and temporal streams. However, the method of extracting motion features from a spatial stream is single-frame recognition, and there is still room for improvement in the perception ability of appearance coherence features. The classical two-stream convolution network structure is modified in this paper by utilizing the strong mining capabilities of the bidirectional gated recurrent unit (BiGRU) to allow the neural network to extract the appearance coherence features of actions. In addition, this paper introduces an attention mechanism (SimAM) based on neuroscience theory, which improves the accuracy and stability of neural networks. Experiments show that the method proposed in this paper (BS-2SCN, BiGRU-SimAM Two-stream convolution network) has high accuracy. The accuracy is improved by 2.6% on the UCF101 data set and 11.7% on the HMDB51 data set. [ABSTRACT FROM AUTHOR]

Poly‐p‐phenyleneterephthalamide (PPTA) is widely used in national defense, military industry, and aerospace. However, with weak compression resistance and twist resistance, development of PPTA is greatly impeded. In this work, a novel rigid rod polymer was synthesized by polycondensation of 2,6‐dihydroxyterephthalic acid with 2,3,5,6‐tetraminopyridine which have a large quantity of hydrogen bonds between these polymer chains which provide excellent thermal properties named poly [N‐(2,5‐diamino‐6‐[imino]‐3‐pyridyl)‐4‐formyl‐2,6‐dihydroxybenzamide] (PPDA). The structure of the polymers was characterized by X‐ray diffraction and Fourier transform infrared spectroscopy. The resulting showed that PPDA has good thermal stability and crystallinity, the maximum thermal decomposition temperature close to 900°C under the nitrogen atmosphere. At the same time, PPDA was insoluble in most organic solvents and exhibited good chemical stability. This indicated a superior performance over that of the poly(2,6‐diimidazo(4,5‐b:4′5′‐e)pyridinylene‐1,4(2,5‐dihydroxy)phenylene). In addition, we can foresee that PPDA will play an important role in prospective surgery and aramid areas. [ABSTRACT FROM AUTHOR]

Research has been conducted on the fulleride anions. The preparation of these anions by means of deprotonation of fullerene C-H bonds and the alkylation of fullerene ions prepared electrochemically are described.

This article used four types rock powder, including granite, gneiss, basalt and limestone, to replace 20% cement to prepare concrete with a water -to -binder of 0.47 or 0.32, and tested their workability and 3 ~1080 d strength, such as cube compressive strength and splitting tensile strength, when the fly ash concrete was selected as the reference sample. The testing results show that the rock powder will affect the concrete workability in different level, and the development model of concrete strength exhibit two-stage feature which contained the rapid development period at 3~180 d and the slow development period at 180 d to 1080 d. Compound exponential function can be used to accurately predict the strength development model of rock powder concrete. The compressive strength ratio of rock powder concrete and fly ash concrete was 0.7~0.9 while the splitting tensile strength ratio was 0.8~1.0. The relationship of compressive strength and splitting tensile strength of rock powder strength can be described by powder function. The 28~90d strength of rock powder concrete was 0.7~0.9 of long-age (1080 d) strength. [ABSTRACT FROM AUTHOR]

Photocatalysis with universality and feasibility has been widely applied to degrade pollutants that mainly exist in gas and liquid systems. However, the photocatalytic degradation of contaminants on solid surfaces is rarely reported. The investigation of the photocatalytic degradation mechanism of pesticide on a solid surface will provide a vital reference for removing pesticide residues on fruit surfaces. Here, we discovered that in situ photocatalytic degradation on solid surface (PDSS) is a moisture dependent process regulated by the interaction between TiO2 and H2O. The interaction mechanism between TiO2 and moisture was revealed by X-ray photoelectron spectroscopy and in situ FT-IR. Meanwhile, we investigated a water layer formed between TiO2 and water on the surface by density functional theory. The photocatalytic degradation process of imidacloprid on the solid surface is proposed. This work explores the H2O impact on photocatalysis in solid surfaces and provides a significant reference for removing pesticide residues in realistic environmental conditions. [ABSTRACT FROM AUTHOR]

An online monitoring technology of Pu-239 aerosol based on aerosol direct introduction device, membrane desolvation nebuliser and ICP-MS was established for workplaces of reprocessing plants. Briefly, 0.8 l min−1 Pu-239 aerosol from the workplace was introduced into the aerosol direct introduction device where the air was replaced by Argon, and then the aerosol was introduced into the ICP-MS for measurement. To determine the activity of Pu-239 aerosol, 1.10E−3 Bq ml−1 Pu-242 standard solution generated by a membrane desolvation nebuliser was used. The introduction efficiency of the nebuliser was determined by sampling the aerosol generated from the nebuliser with Lead Standard Solution by glass fiber filter, which was (26.82 ± 3.33) %. The mass bias between Pu-239 and Pu-242 for the ICP-MS measurement was determined by Pu-239 and Pu-242 standard solutions generated by the nebuliser, and mass discrimination correction factor for Pu-239/Pu-242 was 0.972 ± 0.010. The limit of detection (LOD) and limit of quantification (LOQ) of this system were calculated according to the ISO 20 899:2018, which were 2.24E−05 Bq m−3 and 7.45E−05 Bq m−3 with 1 min measurement. The main interference which was from U-238 was determined by U-238 standard solution generated by the nebuliser, and the interferences of U-238 to 239 was (8.50 ± 1.05) E−05. According to the counts of U-238 from several workplaces of reprocessing plant where this system was tested, 239 counts rate from the interferences of U-238 of those workplaces were at the same level of the system background counts, which meant that the LOD above was suitable for those places. [ABSTRACT FROM AUTHOR]

Sterculia lanceolata, an important tropical woody plant, has high ornamental and medicinal value. To our knowledge, only brown root disease in this plant has been reported. In Nanning, Guangxi, China, an outbreak of leaf blight disease was observed on S. lanceolata in June 2019, with the leaf infection rate ranging from 80% to 100%. The disease seriously affected the leaves of trees and caused economic loss. Eight isolates were recovered from the infected leaves of different trees, and the pathogenicity was then determined by the methods of mycelial disc and conidial suspension, fulfilling Koch's postulates. According to the morphological and molecular biological characteristics of isolates, the pathogen causing leaf blight on S. lanceolata was identified as Colletotrichum siamense. Accurate identification of the pathogen provides a reliable basis for the control of the disease. [ABSTRACT FROM AUTHOR]

Perchlorate is a low molecular weight highly soluble anion. It occurs naturally in the environment, primarily near potash deposits and in arid regions. The determination of perchlorate in human milk is of interest in vulnerable populations such as infants and pregnant women. In this study, a sensitive and selective isotope dilution ion chromatography/tandem mass spectrometry (ID IC-MS/MS) method was developed and validated for the determination of perchlorate in human milk samples collected from the Maternal-Infant Research on Environmental Chemicals (MIREC) Study. The limit of detection (LOD) was 0.27 µg·kg−1 for human milk. A total of 439 human milk samples were analysed with measurable levels of perchlorate in most of the milk samples, and the mean value was 7.62 ± 32.7 µg·kg−1. This project provided important information related to perchlorate levels in human milk collected across Canada and the extent to which pregnant women and their infants may be exposed to perchlorate. A dietary exposure assessment was also conducted in infants based on the measured values in human milk. The mean perchlorate probable daily intakes (PDIs) for infants consuming human milk were 0.31 ± 0.07 μg/kg bw/day for infants under 1 year and 0.17 ± 0.10 μg/kg bw/day for infants between 1 and 3 years old. None of the estimates exceeded the FAO/WHO provisional maximum tolerable daily intake (PMTDI) of 10 μg/kg bw/day. [ABSTRACT FROM AUTHOR]

Byline: Junpeng Shao, Guihua Han, Zhongwen Wang, Wang Dong In order to improve the rigidity performance of the hydrostatic thrust bearing, an electro-hydraulic pressure servo system is proposed to adjust oil film pressure in real-time. A rapid prototyping method is adopted to identify the model of the pressure servo system. A non-linear hybrid controller is applied, which is composed of a classical PID controller and a fuzzy controller based on self-adjusting modifying factor and a fuzzy switching mode is employed to reject undesirable disturbances caused by the switchover between the two control methods. The identification model of the practical system and the feasibility of the control scheme are validated by hardware-in-the-loop simulation experiments. The experiments results show that the hybrid PID controller exhibits high bearing rigidity (the maximum overshoot is 0.07, while PID is 0.2), improves stability and rapidity when load changes. Further, the control performance can be enhanced through matching the load rigidity and mass reasonably; and it is feasible to apply electro-hydraulic pressure servo system to hydrostatic thrust bearing.