A bifunctional cationic porous organic polymer based on a Salen-(Al) metalloligand (Al-CPOP) containing imidazolium functionality exhibited enhanced activity and good recyclability in the ...cycloaddition of carbon dioxide to produce cyclic carbonates without the addition of co-catalysts at atmospheric pressure.
Oxide ceramics are widely used as thermal protection materials due to their excellent structural properties and earth abundance. However, in extremely high‐temperature environments (above 1500 °C), ...the explosive growth of grain size causes irreversible damage to the microstructure of oxide ceramics, thus exhibiting poor thermomechanical stability. This problem, which may lead to catastrophic accidents, remains a great challenge for oxide ceramic materials. Here, a novel strategy of phase transition modulation is proposed to control the grain growth at high temperatures in oxide ceramic nanofibers, realizing effective regulation of the crystalline forms as well as the size uniformity of primary grains, and thus suppressing the malignant growth of the grains. The resulting oxide ceramic nanofibers have excellent mechanical strength and flexibility, delivering an average tensile strength as high as 1.02 GPa after being exposed to 1700 °C for 30 min, and can withstand thousands of flexural cycles without obvious damage. This work may provide new insight into the development of advanced oxide ceramic materials that can serve in extremely high‐temperature environments with long‐term durability.
A phase transition modulation strategy is proposed to prepare oxide ceramic nanofibers, which are featured by inhibited grain growth at high temperatures. As a result, a strikingly high average tensile strength of 1.02 GPa is achieved at 1700 °C, laying a basis for developing advanced oxide ceramics for reliable thermal protection in extremely high‐temperature environments.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
We study a fifth order time-fractional KdV equation (FKdV) under meaning of the conformal fractional derivative. By trial equation method based on symmetry, we construct the abundant exact traveling ...wave solutions to the FKdV equation. These solutions show rich evolution patterns including solitons, rational singular solutions, periodic and double periodic solutions and so forth. In particular, under the concrete parameters, we give the representations of all these solutions.
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Abstract
Background
Since interferon regulatory factor (IRF) family functions in immune response to viral infection, its role in colorectal cancer (CRC) has not been inspected before. This study ...tries to investigate members of IRF family using bioinformatics approaches in aspect of differential expressions, biological function, tumor immune infiltration and clinical prognostic value for patients with CRC.
Methods
Transcriptome profiles data, somatic mutations and clinical information of CRC were obtained from COAD/READ dataset of The Cancer Genome Atlas (TCGA) as a training set. Gene expression data (GSE17536 and GSE39582) were downloaded from the Gene Expression Omnibus as a validating set. A random forest algorithm was used to score the risk for every case. Analyzing gene and function enrichment, constructing protein–protein interaction and noncoding RNA network, identifying hub-gene, characterizing tumor immune infiltration, evaluating differences in tumor mutational burden (TMB) and sensitivity to chemotherapeutics or immunotherapy were performed by a series of online tools and R packages. Immunohistochemical (IHC) examinations were carried out validation in tissue samples.
Results
Principal-component analysis (PCA) suggested that the transcript expression levels of nine members of IRF family differed between normal colorectum and CRC. The risk score constructed by IRF family not only acted as an independent factor for predicting survival in CRC patients with different biological processes, signaling pathways and TMB, but also indicated different immunotherapy response with diverse immune and stromal cells infiltration. IRF3 and IRF7 were upregulated in CRC and suggested a shorter survival time in patients with CRC. Differentially expressed members of IRF family exhibited varying degrees of immune cell infiltration. IHC analysis showed a positive association between IRF3 and IRF7 expression and tumor-infiltrating immune cells, including CD4
+
T cell and CD68
+
macrophages.
Conclusions
On account of differential expression, IRF family members can help to predict both response to immunotherapy and clinical prognosis of patients with CRC. Our bioinformatic investigation not only gives a preliminary picture of the genetic features as well as tumor microenvironment, but it may provide a clue for further experimental exploration and verification on IRF family members in CRC.
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Carbon aerogels (CAs) are desirable for thermal protection in aerospace because of their lightweight and high‐temperature insulation characteristic; however, their intrinsic brittleness and flaw ...sensitivity easily trigger catastrophic failure when resisting high‐frequency thermal shocks or complex mechanical stresses. Compression is the predominant load applied on aerogels by aerodynamic pressure and pre‐tightening force; therefore, the structural elasticity and exceptional capability to keep thermal performance under impact stress are crucial in deciding the actual availability of aerogels. This review presents the recent progress in newly resilient CAs for thermal protection, focusing on reliable structural stability, thermal stability, and thermal superinsulation property. The influence law of microstructures on heat transfer behaviors is first investigated, followed by construction strategies for adiabatic CAs, emphasizing the recoverable deformability resulting from increased continuity of building blocks from 0D nanoparticles to 1D nanofibers/nanotubes and then to 2D nanosheets. Moreover, the optimization of thermal stability in high‐temperature aerobic environments and thermal insulation performance are discussed. Finally, it raises current challenges and further opportunities for CAs toward better properties and brighter prospects.
Superelastic and superinsulation carbon aerogels are highly promising for thermal protection under extreme conditions. This review presents a comprehensive insight into recent advances in this emerging material, focusing on fundamental heat transfer mechanisms, nanostructured engineering strategies, optimization pathways for thermal stability and thermal insulation performance, as well as current challenges and future developments.
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Contamination of agricultural soil by heavy metals has become a global issue concerning food security and human health risk. In this study, a soil investigation was conducted to evaluate metals ...accumulation, potential ecological and health risks as well as to identify sources of metals in paddy soils in Hanzhong City, which is located in a sedimentary basin. Ninety-two (92) surface soil samples (bulk soil) and their corresponding rice samples, 21 irrigation water samples, and 18 fertilizer samples were collected from two typical counties and quantified for the heavy metals (i.e., As, Cd, Cu, Hg, Pb, and Zn) concentrations. The results showed that As, Cd, and Zn were the main contaminants in soils in the studied area. Additionally, elevated Hg content in soils might also pose risks to the local ecosystem. Cadmium and As demonstrated high mobility, and their average contents in rice grains were slightly higher than the permissible threshold (0.20 mg kg−1). Moreover, Pb, As, and Cd intake via rice consumption might result in potential risks to local residents. Metal distribution revealed that pollution in the studied area is non-homogeneous, and agricultural activities (As, Cu, and Cd), transportation emission (Cu and Pb), coal combustion (Hg and As), and smelting activities (Zn, Pb, and Cu) were ascertained as the potential sources based on the Positive matrix factorization (PMF) analysis results.
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•Metal contents in 92 soil and rice, 22 water, and 18 fertilizer samples were determined.•Cd and As were the main pollutants in soils, and soil Hg may pose risks to local ecosystem.•Average Cd and As contents in rice grains slightly exceeded the permissive limits.•Daily intake of Pb, As, and Cd might pose risks to local residents health.•Five sources were identified as main contributors to the elevated metals in paddy soils.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Being conductive and flexible, 2D transition metal nitrides and carbides (MXenes) can serve in Li–S batteries as sulfur hosts to increase the conductivity and alleviate the volume expansion. However, ...the surface functional groups, such as OH and F, weaken the ability of bare MXenes in the chemisorption of polysulfides. Besides, they create numerous hydrogen bonds which make MXenes liable to restack, resulting in substantial loss of active area and, thus, inaccessibility of ions and electrolyte. Herein, a facile, one‐step strategy is developed for the growth of TiO2 quantum dots (QDs) on ultrathin MXene (Ti3C2Tx) nanosheets by cetyltrimethylammonium bromide‐assisted solvothermal synthesis. These QDs act as spacers to isolate the MXene nanosheets from restacking, and preserve their 2D geometry which guarantees larger electrode–electrolyte contact area and higher sulfur loading. The stronger adsorption energy of polysulfides with TiO2 (than with Ti3C2Tx), as proven by density functional theory calculations, is essential for better on‐site polysulfide retention. The ultrathin nature and protected conductivity ensure rapid ion and electron diffusion, and the excellent flexibility maintains high mechanical integrity. In result, the TiO2 QDs@MXene/S cathode exhibits significantly improved long‐term cyclability and rate capability, disclosing a new opportunity toward fast and stable Li–S batteries.
TiO2 quantum dots (QDs) are grown on ultrathin MXene nanosheets by a facile, one‐step strategy through cetyltrimethylammonium bromide‐assisted solvothermal synthesis, resulting in TiO2 QDs@MXene nanohybrids that serve as a high‐performance sulfur host toward fast and stable Li–S batteries.
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•The AdaBoost algorithm is adopted to predict the compressive strength of concrete.•1030 sets of data is collected to train the model and reaches an accuracy of 98%.•Different algorithms are compared ...to show the superior of the proposed model.•Key factors and in the AdaBoost and influence of input variables are investigated.
In this paper, an intelligent approach based on the machine learning technique is proposed for predicting the compressive strength of concrete. This approach employs the adaptive boosting algorithm to construct a strong learner by integrating several weak learners, which can find the mapping between the input data and output data. The weak learner whose predicting error is small will have a larger weight in the entire system, thus the overall accuracy of the strong learner will be enhanced. A total of 1030 sets of concrete compressive strength tests is collected to train and test the learners, in which the concrete mixture components (e.g., coarse/fine aggregates, cement, water, additive, etc.) and the curing time are set as the input data while the compressive strength value is set as the output data. The proposed approach is validated through a 10-fold cross validation method, and reaches an average accuracy of over 95% in sense of determination coefficient. In addition, a new dataset of 103 samples for concrete compressive strength is also adopted to demonstrate the generalization power of the proposed mode. The proposed approach is also compared to some other individual machine learning techniques that are already applied in this field, e.g., artificial neural network (ANN) and support vector machine (SVM), and shows superior advantages over these methods. Finally, the influence of some key factors in the adaptive boosting approach is also investigated, e.g., the amount of training data, the choice of weak learner, and the influence of the sensitivity and number of the input parameters. It is shown that using 80% of the total data for training can obtain acceptable prediction results and decision tree is the best choice for the weak learner in the boosting framework. Also, the importances of different input variables are obtained based on the sensitivity analysis results.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Abstract
Mega-urban agglomerations in developing countries have been main parts of economic development. But at the same time, they have become the most prominent and sensitive areas of resource and ...environment problems. It is important to clarify the mechanism and driving factors of green growth in mega-urban agglomerations. Based on the panel data of 28 major cities in China's Pan-Pearl River Delta urban agglomeration from 2006 to 2015, this paper evaluates the level of green development of urban agglomeration by green total factor productivity index (GTFP) based on Global Malmquist DEA model, and decomposes GTFP into technological progress, pure technical efficiency change, scale efficiency change and technological scale change. On this basis, this paper constructs a panel econometric model to analyze the influencing factors of GTFP and its decomposition factors. The results show that GTFP of Pan-Pearl River Delta urban agglomeration is growing, and the scale effect caused by technological progress is the main driving factor. Green development in the Pearl River Delta urban agglomeration takes into account efficiency and regional fairness, which causes differences in GTFP growth patterns of sub-urban agglomerations within mega-urban agglomerations. The technological progress and technical efficiency improvement are becoming the main driving force of GTFP growth in relatively backward areas. Furthermore, according to the influencing factors of GTFP and its decomposition factors, mega-urban agglomeration should eliminate internal administrative barriers to build an integrated market. It should also increase the proportion of technology industries in core cities, and give full play to the role of technology spillover effect on surrounding cities. In addition, improving the efficiency of resource and energy utilization is also helpful to promote the transformation of urban agglomeration development from factor-driven to efficiency-driven and innovation-driven. Our research results have implications for the coordinated development of economy and environment in developing countries.
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