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•A highly efficient CTL sensor for acetone vapor coupled with UIO-66 as the preconcentrator was established.•A simple and low-cost home-made adsorption apparatus with UIO-66 was ...fabricated.•The proposed CTL sensing platform demonstrated advantages of high sensitivity, selectivity, and speediness.
Metal-organic frameworks (MOFs) showed a significant sorption potential in the gas capture and preconcentration during recent years because of its super porosity. Herein, we fabricated a simple and inexpensive home-made adsorption apparatus based on UIO-66 as the preconcentrator, which was firstly coupled with a rapid cataluminescence (CTL) sensor to determine acetone vapor. The CTL emission was enhanced by 25 times after the preconcentration of UIO-66, indicating the UIO-66 preconcentrator could efficiently ameliorate sensitivity. As for the adsorption mechanism of UIO-66 for acetone molecules, we deduced that acetone molecules were preferentially located on the Zr clusters with high hydrophilicity. The proposed CTL sensor in combine with UIO-66 adsorption granted a detection limit of acetone down to 2.79 ppm, and demonstrated good selectivity, simplicity, rapidity, and recyclability. This study provides appealing perspectives of UIO-66 as the preconcentrator for the improvement of analytical performance, and the prospect of a miniaturized portable acetone sensor.
Poly(N-vinyl-2-pyrrolidone)(PVP)-protected Au/Ni bimetallic nanoparticles (BNPs) were prepared in one-vessel via chemical reduction of the corresponding ions with dropwise addition of NaBH4, and ...their catalytic activity in the hydrogen generation from hydrolysis of a basic NaBH4 solution was examined. The structure, particle size, and chemical composition of the resultant BNPs were characterized by Ultraviolet–visible spectrophotometry (UV–Vis), X-ray photoelectron spectroscopy (XPS), Transmission electron microscopy (TEM) and High-resolution transmission electron microscopy (HR-TEM). The effects of processing parameters such as metal composition, metal ion concentration, and mole ratio of PVP to metal ion on the hydrolysis of a basic NaBH4 solution were studied in detail. The results indicated that as-prepared Au/Ni BNPs showed a higher catalytic activity than corresponding monometallic NPs (MNPs) in the hydrogen generation from the hydrolysis reaction of a basic NaBH4 solution. Among all the MNPs and BNPs, Au/Ni BNPs with the atomic ratio of 50/50 exhibited the highest catalytic activity, showing a hydrogen generation rate as high as 2597 mL-H2 min−1 g-catalyst−1 at 30 °C, which can be ascribed to the presence of negatively charged Au atoms and positively charged Ni atoms. Based on the kinetic study of the hydrogen generation from the hydrolysis reaction of a basic NaBH4 solution over the PVP-protected Au/Ni BNPs, the corresponding apparent activation energy was determined as 30.3 kJ/mol for the BNPs with the atomic ratio of 50/50.
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•PVP-protected Au/Ni BNPs with size of 2.0 ± 0.7 nm in diameter were synthesized.•Catalytic activity of Au/Ni BNPs for hydrogen generation from NaBH4 was studied.•Catalytic activity of Au50Ni50 BNPs is 9 times higher than that of Au MNPs.•DFT and XPS proved the negatively charged Au atoms and positively charged Ni atoms.•The corresponding apparent activation energy was 30.3 kJ/mol for the Au50Ni50 BNPs.
Communicating health knowledge effectively at the community level is essential for shaping resilient urban governance in a pandemic period. This paper examines how three styles of community health ...communication, namely traditional authoritative communication (TAC), authoritative communication via social media (ACSM), and interactive communication via social media (ICSM), were associated with public trust in different types of “institutions”, namely the community administration and scientists, in a context where the respondents were in strict lockdown. This research was conducted with an online survey in February 2020 of 4595 respondents in urban China not long after the strict lockdown was introduced. Embedded in the theory of public trust in institutions during pandemic, the regressions established that traditional authoritative communication played a significant role in maintaining the public's trust in both community administrators and scientists. Interactive communication via social media damaged trust in scientists and increased trust in administrators when used effectively. It is suggested that policymakers, government officials, and healthcare professionals should not abandon traditional authoritative health communication, and greater efforts can be devoted to quality improvement. Moreover, the study highlighted the need to gain a better understanding of what the targeted audience perceive to be “good communication” before communication.
Short duration text-independent speaker verification remains a hot research topic in recent years, and deep neural network based embeddings have shown impressive results in such conditions. Good ...speaker embeddings require the property of both small intra-class variation and large inter-class difference, which is critical for the ability of discrimination and generalization. Current embedding learning strategies can be grouped into two frameworks: "Cascade embedding learning" with multiple stages and "direct embedding learning" from spectral feature directly. We propose new approaches to achieve more discriminant speaker embeddings. Within the cascade framework, a neural network based deep discriminant analysis (DDA) is proposed to project i-vector to more discriminative embeddings. Within the direct embedding framework, a deep model with more advanced center loss and A-softmax loss is used, the focal loss is also investigated in this framework. Moreover, the traditional i-vector and neural embeddings are finally combined with neural network based DDA to achieve further gain. Main experiments are carried out on a short-duration text-independent speaker verification dataset generated from the SRE corpus. The results show that the newly proposed method is promising for short-duration text-independent speaker verification, and it is consistently better than traditional i-vector and neural embedding baselines. The best embeddings achieve roughly 30% relative EER reduction compared to the i-vector baseline, which could be further enhanced when combined with the i-vector system.
The concentration of
l
-cysteine (
l
-Cys) provides important information about specific physiological functions and disease diagnosis. In this work, we provided a facile colorimetric approach for
l
...-Cys detection with high sensitivity and specificity. Ficin acted as a peroxidase mimic and catalyzed the chromogenic reaction of TMB and H
2
O
2
. However, after the introduction of
l
-Cys,
l
-Cys competed with TMB for H
2
O
2
. The competition is generally won by the more-reactive
l
-Cys resulting in fading of the chromogenic reaction. The detection limit of
l
-Cys can be as low as 20 nM (3
σ
). In addition, the assay can also be successfully applied to detect
l
-Cys in biological fluids, indicating its potential in biological sample analysis. Our work could promote the application of the enzyme mimicking activity of ficin in medical diagnostics and biochemistry.
H
2
O
2
could oxidize TMB to blue-colored oxTMB with catalysis by ficin.
l
-Cys competed with TMB for H
2
O
2
leading to fading of the chromogenic reaction.
As an aftermath of the Fukushima nuclear accident and its implications for public acceptance of nuclear energy, the nuclear industry has begun to seriously rethink and improve the safety strategies ...of nuclear power plants. The beyond-design-basis external events, such as the earthquake and tsunami in Fukushima nuclear accident, may lead to an extreme accident which may lead to the failure of the traditional strategies. In the recent decade, the concept of FLEX strategies has been accepted in the nuclear engineering community and attracted a large number of researchers to investigate it for nuclear accident mitigation. The development of FLEX strategies is divided into two steps. One is an uncertainty study of system response, especially the safety injection system. The other is training and testing of machine learning (ML)-based FLEX strategies and to verify the effectiveness of ML algorithms in the development of FLEX strategies for nuclear power plants. This paper focuses on first step uncertainty study of the nuclear accidents by using statistical algorithm to generate a database of incidents and system responses. The conclusion of this paper is useful for analyzing the characteristic of typical nuclear accidents and benefits to the FLEX strategy development, which will be focused on in the near future.
A novel approach for quickly separating a metal copper phase and iron-rich phase from copper slag at low temperature is proposed based on a super-gravity method. The morphology and mineral evolution ...of the copper slag with increasing temperature were studied using
in situ
high-temperature confocal laser scanning microscopy and
ex situ
scanning electron microscopy and X-ray diffraction methods. Fe
3
O
4
particles dispersed among the copper slag were transformed into FeO by adding an appropriate amount of carbon as a reducing agent, forming the slag melt with SiO
2
at low temperature and assisting separation of the copper phase from the slag. Consequently, in a super-gravity field, the metallic copper and copper matte were concentrated as the copper phase along the super-gravity direction, whereas the iron-rich slag migrated in the opposite direction and was quickly separated from the copper phase. Increasing the gravity coefficient (G) significantly enhanced the separation efficiency. After super-gravity separation at G = 1000 and 1473 K (1200 °C) for 3 minutes, the mass fraction of Cu in the separated copper phase reached 86.11 wt pct, while that in the separated iron-rich phase was reduced to 0.105 wt pct. The recovery ratio of Cu in the copper phase was as high as up to 97.47 pct.
The stock market is a complex system with unpredictable stock price fluctuations. When the positive feedback in the market amplifies, the systemic risk will increase rapidly. During the last 30 years ...of development, the mechanism and governance system of China’s stock market have been constantly improving, but irrational shocks have still appeared suddenly in the last decade, making investment decisions risky. Therefore, based on the daily return of all a-shares in China, this paper constructs a dynamic complex network of individual stocks, and represents the systemic risk of the market using the average weighting degree, as well as the adjusted structural entropy, of the network. In order to eliminate the influence of disturbance factors, empirical mode decomposition (EMD) and grey relational analysis (GRA) are used to decompose and reconstruct the sequences to obtain the evolution trend and periodic fluctuation of systemic risk. The results show that the systemic risk of China’s stock market as a whole shows a downward trend, and the periodic fluctuation of systemic risk has a long-term equilibrium relationship with the abnormal fluctuation of the stock market. Further, each rise of systemic risk corresponds to external factor shocks and internal structural problems.
In this work, umbelliferone, a kind of coumarin derivative, was proved to exhibit peroxidase-like activity that could catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of ...hydrogen peroxide to generate a blue-colored oxide (oxTMB). The catalytic mechanism is similar to that of native enzymes (e.g. horseradish peroxidase, HRP) and nanozymes, which follow the Michaelis–Menten kinetics behavior. Meanwhile, the 7-hydroxyl group of umbelliferone plays a significant role in the peroxidase-like activity. Compared with enzymes and nanozymes, this small molecular mimic enzyme possesses the advantages of low cost, simple molecular structures, small molecular weight and high stability against harsh conditions. Based on the favorable peroxidase mimetic activity of umbelliferone, a convenient, practical and sensitive H2O2 and glucose detection method was successfully established. This work not only opens some new inspirations into seeking for novel molecular enzyme mimetics with excellent catalytic activities, but also provides promising assays for clinical diagnosis.
Abstract
In image transmission, with the consideration of system parameters, such as bandwidth, transmission delay and power consumption, the image compression coding is often used to reduce the ...amount of transmitted data. The formation mechanism of block effect in H.264 coding is analyzed. Taking H.264 coding as an example, the spatial domain image enhancement processing is adopted in the paper to obtain the two-dimensional information entropy covering the gray correlation and image edge feature information in adjacent spatial domain. By referring to the two-dimensional information entropy evaluation value of original and coded image, the image quality evaluation result is consistent with PSNR method used in common situations. Compared with the traditional PSNR evaluation method, the two-dimensional information entropy evaluation method only refers to the two-dimensional information entropy evaluation value of the original image, and the amount of data required is very low. Therefor, it is more suitable for the engineering implementation of real-time image quality evaluation in image transmission system. At the same time, with the edge feature information of the image used in the two-dimensional information entropy, the entropy method is closer to the actual feeling of human eyes than PSNR method.
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