Positive cooperative binding, a phenomenon prevalent in biological processes, holds great appeal for the design of highly sensitive responsive molecules and materials. It has been demonstrated that ...metal–organic frameworks (MOFs) can show positive cooperative adsorption to the benefit of gas separation, but potential binding cooperativity is largely ignored in the study of sensory MOFs. Here, we report the first demonstration of positive cooperative protonation of a MOF and the relevant pH response in fluorescence and proton conduction. The MOF is built of Zr–O clusters and bipyridyl-based tetracarboxylate linkers and has excellent hydrolytic stability. It shows a unique pH response that features two synchronous abrupt turn-off and turn-on fluorescent transitions. The abrupt transitions, which afford high sensitivity to small pH fluctuations, are due to cooperative protonation of the pyridyl sites with a Hill coefficient of 1.6. The synchronous dual-emission response, which leads to visual color change, is ascribable to proton-triggered switching between (n, π*) and (π, π*) emissions. The latter emission can be quenched by electron donating anion-dependent through photoinduced electron transfer and ground-state charge transfer. Associated with cooperative protonation, the proton conductivity of the MOF is abruptly enhanced at low pH by two orders, but overhigh acid concentration is adverse because excessive anions can interrupt the conducting networks. Our work shows new perspectives of binding cooperativity in MOFs and should shed new light on the development of responsive fluorescent MOFs and proton conductive materials.
The COVID-19 medical diagnosis method based on individual’s chest X-ray (CXR) is achieved difficultly in the initial research, owing to difficulties in identifying CXR data of COVID-19 individuals. ...At the beginning of the study, infected individuals’ CXRs were scarce. The combination of artificial intelligence and medical diagnosis has been advanced and popular. To solve the difficulties, the interpretability analysis of AI model was used to explore the pathological characteristics of CXR samples infected with COVID-19 and assist medical diagnosis. The dataset was expanded by data augmentation to avoid overfitting. Transfer learning was used to test different pre-trained models and the unique output layers were designed to complete the model training with few samples. In this study, the output results of four pre-trained models were compared in three different output layers, and the results after data augmentation were compared with the results of the original dataset. The control variable method was used to conduct independent tests of 24 groups. Finally, 99.23% accuracy and 98% recall rate were obtained, and the visual results of CXR interpretability analysis were displayed. The network of COVID-19 interpretable diagnosis algorithm has the characteristics of high generalization and lightweight. It can be quickly applied to other urgent tasks with insufficient experimental data. At the same time, interpretability analysis brings new possibilities for medical diagnosis.
Single site catalysts(SSCs) are a new type of heterogeneous catalysts formed by isolated metal atoms supported on kinds of substrates. SSCs have shown great potential for energy conversion and ...storage in recent years, especially for oxygen reduction reactions(ORR). Typically, SSCs are confined on the substrate by strong chemical interactions, such as coordination bonds. Therefore, the surface chemical environment and porous properties of the supports are crucial to the performance of SSCs. In recent years, COFs have become excellent candidates for preparing SSCs as they can precisely assemble monomers into highly ordered crystalline porous materials with a fine structure and definite components. In this review, we not only summarize the characteristics and advantages of COFs based SSCs, but also highlight the applications of COFs constructed from different single active sites for ORR in recent years. Finally, challenges in practical application, feasible strategies and perspectives are proposed for the of COFs based SSCs.
Satellite observations of atmospheric CO2 are able to truly capture the variation of global and regional CO2 concentration. The model simulations based on atmospheric transport models can also assess ...variations of atmospheric CO2 concentrations in a continuous space and time, which is one of approaches for qualitatively and quantitatively studying the atmospheric transport mechanism and spatio-temporal variation of atmospheric CO2 in a global scale. Satellite observations and model simulations of CO2 offer us two different approaches to understand the atmospheric CO2. However, the difference between them has not been comprehensively compared and assessed for revealing the global and regional features of atmospheric CO2. In this study, we compared and assessed the spatio-temporal variation of atmospheric CO2 using two datasets of the column-averaged dry air mole fractions of atmospheric CO2（XCO2） in a year from June 2009 to May 2010, respectively from GOSAT retrievals（V02.xx） and from Goddard Earth Observing System-Chemistry（GEOS-Chem）, which is a global 3-D chemistry transport model. In addition to the global comparison, we further compared and analyzed the difference of CO2 between the China land region and the United States（US） land region from two datasets, and demonstrated the reasonability and uncertainty of satellite observations and model simulations. The results show that the XCO2 retrieved from GOSAT is globally lower than GEOS-Chem model simulation by 2 ppm on average, which is close to the validation conclusion for GOSAT by ground measures. This difference of XCO2 between the two datasets, however, changes with the different regions. In China land region, the difference is large, from 0.6 to 5.6 ppm, whereas it is 1.6 to 3.7 ppm in the global land region and 1.4 to 2.7 ppm in the US land region. The goodness of fit test between the two datasets is 0.81 in the US land region, which is higher than that in the global land region（0.67） and China land region（0.68）. The analysis results further indicate that the inconsistency of CO2 concentration between satellite observations and model simulations in China is larger than that in the US and the globe. This inconsistency is related to the GOSAT retrieval error of CO2 caused by the interference among input parameters of satellite retrieval algorithm, and the uncertainty of driving parameters in GEOS-Chem model.
Abstract Background and objectives Combination of transcatheter arterial chemoembolization (TACE) and radiofrequency ablation (RFA) has become an effective alternative therapy for hepatocellular ...carcinoma (HCC). In clinical practice, the choice of time interval between TACE and RFA is a key point for curative effect, but optimal time interval is uncertain in guidelines. We aim to explore the optimal time interval for HCC patients of Child-Pugh classification A or B. Methods Two hundred and thirty-three HCC patients of Child A or B who had undergone TACE and RFA were enrolled and divided into seven groups according to different time intervals (1–7weeks). Tumor damage, liver function, complications and survival time of patients after treatment were analyzed. Results Complete remission rate and total effective rate decreased in groups with the prolonged time interval (p < 0.05). Average Child-Pugh score of patients in first three groups significantly increased one month after combination treatment (p < 0.01). While that not happened in other groups. Complications occurred in 16.7% patients, similarly occurred in groups (p > 0.1). Median survival time in groups four and five were 42 months, longer than other groups (p < 0.01). Conclusion A period of 3–5 weeks is the optimal time interval between TACE and RFA for HCC patients of Child-Pugh classification A or B.
Electrocatalytic conversion of carbon dioxide to high value-added chemicals is a promising method for solving the energy crisis and global warming. Electrochemical active metal-containing conjugated ...polymers have been widely studied for heterogeneous carbon dioxide reduction. In the present contribution, we designed and synthesized a stable cobalt phthalocyanine-based conjugated polymer, named CoPPc-TFPPy-CP, and also explored its electrocatalytic application in carbon dioxide reduction to liquid products in an aqueous solution. In the catalyst, cobalt phthalocyanine acts as building blocks connected with 1,3,6,8-tetrakis(4-formyl phenyl)pyrenes via imine-linkages, leading to mesoporous formation polymers with the pore size centered at 4.1 nm. And the central cobalt atoms shifted to a higher oxidation state after condensation. With these chemical and structural natures, the catalyst displayed a remarkable electrocatalytic CO2 reduction performance with an ethanol Faradaic efficiency of 43.25% at −1.0 V vs RHE. While at the same time, the electrochemical reduction process catalyzed by cobalt phthalocyanine produced only carbon monoxide and hydrogen. To the best of our knowledge, CoPPc-TFPPy-CP is the first example among organic polymers and metal-organic frameworks that produces ethanol from CO2 with a remarkable selectivity.
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In this paper, a high-precision and large-range wind speed and direction measuring method is proposed, which can solve the problem that traditional Time of Flight (ToF) method and phase detection ...method cannot simultaneously take into account measuring accuracy and measurement range. Firstly, based on the binary amplitude modulation and cross-correlation algorithms, the coded pulses combination is designed to measure time difference that the ultrasonic wave arrives different ultrasonic receivers. Because the coded pulses combination can obtain sharper correlation peaks, a more accurate time-difference measurement result can be gained, comparing with the traditional ToF method. Then, for further improving measuring accuracy and resolution of wind speed, a high-precision ±180° digital phase detection method based on double D flip-flops is proposed. Next, by combining time-difference and phase-difference measurement results, the measuring range of wind speed is extended and measuring accuracy is improved. Finally, a wind speed and direction measuring system is set up based on the proposed method. The experimental results show that the wind speed measuring accuracy is ±2%, the resolution is 0.05 m/s and the measurement range can theoretically reach several hundred meters per second; the wind direction measuring accuracy is ±5° and the resolution is 0.5°. At the same time, the standard deviations of the experimental results which are less than 10% demonstrate the stability of the system.
Passive acoustic observation of whales is an increasingly important tool for whale research. Accurately detecting whale sounds and correctly classifying them into corresponding whale species are ...essential tasks, especially in the case when two species of whales vocalize in the same observed area. Whistles are vital vocalizations of toothed whales, such as killer whales and long-finned pilot whales. In this paper, based on deep convolutional neural networks (CNNs), a novel method is proposed to detect and classify whistles of both killer whales and long-finned pilot whales. Compared with traditional methods, the proposed one can automatically learn the sound characteristics from the training data, without specifying the sound features for classification and detection, and thus shows better adaptability to complex sound signals. First, the denoised sound to be analyzed is sent to the trained detection model to estimate the number and positions of the target whistles. The detected whistles are then sent to the trained classification model, which determines the corresponding whale species. A GUI interface is developed to assist with the detection and classification process. Experimental results show that the proposed method can achieve 97% correct detection rate and 95% correct classification rate on the testing set. In the future, the presented method can be further applied to passive acoustic observation applications for some other whale or dolphin species.
The development of selective sensing materials for amine detection has received considerable attentions because amines have high toxicity and exist widely. In this article, we demonstrate for the ...first time that a degree of discriminative detection of alkylamines can be achieved by a metal–organic coordination material. The material is derived from CdII and 4,4′-bipyridinium-1,1′-bis(phenylene-3-carboxylate), shows 1D channels lined with electron-deficient viologen chromophores, and exhibits different colors upon contact with amine vapors of different molecular sizes and types (primary, secondary, and tertiary). The vapochromism is attributable to electron transfer from the amine group to viologen. The discrimination between amines is because the analyte–receptor interactions, which either directly mediate or indirectly affect electron transfer, are influenced by the number of the N–H bonds in the amine molecule, the size of the amine molecule relative to the receptor channel and the steric hindrance for the electron donor–acceptor contacts. The material also shows reversible photo- and hydrochromism owing to stimuli-induced reversible electron transfer. The compound can be deposited in paper simply by spraying the mixture solution of the starting metal salt and the ligand. The paper can be used as portable test strips for visual and differentiable detection of amines and as erasable inkless printing medium.
•The intercalation of the anion of ILs into the interlayer of LDHs was confirmed.•The maximum adsorption capability of ILs/LDHs reached up to 300.9mg/g.•The adsorption kinetics, isotherm, ...thermodynamic and mechanisms were discussed.•The ILs/LDHs might be used as an efficient adsorbent for dye waste water.
A series of hydroxyl ammonium ionic liquids/layered double hydroxides intercalation composites (ILs/LDHs) were synthesized and adopted to study the adsorption process of anionic dye reactive orange 5 from aqueous solutions. The ILs/LDHs and LDHs were characterized by infrared spectroscopy (IR), X-ray diffractometry (XRD), thermogravimetric analysis (TG), total organic carbon (TOC) analyzer and BET surface area measurement. The successful intercalation of the anion of ILs (2-hydroxyethylammonium acetate) into the interlayer space of LDHs was confirmed. The effects of contact time, temperature, adsorbent dosage and solution pH on the adsorption experiments were investigated. The experimental results showed that the maximum adsorption capability of ILs/LDHs reached up to 300.9mg/g, which was obviously higher than that of LDHs. The adsorption isotherms were well described by Freundlich model in the presence of the LDHs and ILs/LDHs. The adsorption kinetics followed the pseudo-second order kinetic model. The negative value of ΔG0 and the positive value of ΔH0 indicated spontaneous and endothermic nature of reactive orange 5 adsorption. For ILs/LDHs(b), desorption percentages were 57.91%, 46.67%, and 37.34% in each cycle, respectively. This innovative approach, using ILs/LDHs, was more efficient and could be envisaged as a promising process for reducing the pollution of the textiles manufacturing.
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