Abstract
The search for constructing high-performance catalysts is an unfailing topic in chemical fields. Recently, we have witnessed many breakthroughs in the synthesis of single-atom catalysts ...(SACs) and their applications in catalytic systems. They have shown excellent activity, selectivity, stability, efficient atom utilization and can serve as an efficient bridge between homogeneous and heterogenous catalysis. Currently, most SACs are synthesized via a bottom-up strategy; however, drawbacks such as the difficulty in accessing high mass activity and controlling homogeneous coordination environments are inevitably encountered, restricting their potential use in the industrial area. In this regard, a novel top-down strategy has been recently developed to fabricate SACs to address these practical issues. The metal loading can be increased to 5% and the coordination environments can also be precisely controlled. This review highlights approaches to the chemical synthesis of SACs towards diverse chemical reactions, especially the recent advances in improving the mass activity and well-defined local structures of SACs. Also, challenges and opportunities for the SACs will be discussed in the later part.
The three-dimensional equations of compressible magnetohydrodynamic isentropic flows are considered. An initial-boundary value problem is studied in a bounded domain with large data. The existence ...and large-time behavior of global weak solutions are established through a three-level approximation, energy estimates, and weak convergence for the adiabatic exponent
and constant viscosity coefficients.
•This study uses the new machine learning algorithms to predict the default risk.•Two different ways to clean too many variables and missing values data.•Comparisons are made between these two ...equally sophisticated algorithms.•Put forward relevant policy recommendations for global P2P platforms.
Big data and the Internet financial sector tremendously developed in the 21st century. The national emphasis on this field has also gradually improved. Peer-to-peer (P2P) is an innovative mode of borrowing that is a powerful complement to the traditional financial industry. The projected default rate on credit is an absolute prerequisite for guaranteeing the proper operation of related financial projects or platforms. In this paper, we use ‘multi-observation’ and ‘multi-dimensional’ data cleaning method and apply the modern machine learning algorithms LightGBM in Asia at the end of 2016 and XGboost, which are based on real P2P transaction data from Lending club. The default risk of loans in the platform is strongly and innovatively predicted. And the results of different methods are compared. Furthermore, we observe that the LightGBM algorithm based on multiple observational data set classification prediction results is the best. The average performance rate of the historical transaction data of the Lending Club platform rose by 1.28 percentage points, which reduced loan defaults by approximately $117 million. Finally, with respect to the influencing factors of the default rate, suggested developments for the Lending club and other P2P platforms are provided as is the suggested direction of other countries’ development in this field.
The equations of the three-dimensional viscous, compressible, and heat conducting magnetohydrodynamic flows are considered in a bounded domain. The viscosity coefficients and heat conductivity can ...depend on the temperature. A solution to the initial-boundary value problem is constructed through an approximation scheme and a weak convergence method. The existence of a global variational weak solution to the three-dimensional full magnetohydrodynamic equations with large data is established.
The global solutions in critical spaces to the multi-dimensional compressible viscoelastic flows are considered. The global existence of the Cauchy problem with initial data close to an equilibrium ...state is established in Besov spaces. Using uniform estimates for a hyperbolic–parabolic linear system with convection terms, we prove the global existence in the Besov space which is invariant with respect to the scaling of the associated equations. Several important estimates are achieved, including a smoothing effect on the velocity, and the
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-decay of the density and deformation gradient.
Abstract
Solid nanogenerators often have limited charge transfer due to their low contact area. Liquid–liquid nanogenerators can transfer a charge better than the solid–solid and solid–liquid ...counterparts. However, the precise manipulation of the liquid morphology remains a challenge because of the fluidity limits of the liquid. In this work, using the surface tension of a droplet to fix its shape, a liquid-liquid triboelectric nanogenerator in Contact-Separation mode is designed using an immiscible aqueous-aqueous interface, achieving a contact surface charge transfer of 129 nC for a single droplet. The configuration is proven to be applicable in humid environments, and the two-phase materials have good biocompatibility and can be used as an effective drug carrier. Therefore, this nanogenerator is useful for designing future implantable devices. Meanwhile, this design also establishes the foundation of aqueous electronics, and additional applications can be achieved using this route.
In addition to the energystoring white adipose tissue （WAT）, mammals possess brown adipose tissue （BAT） that burns fat to release heat for thermogenesis. BAT is abundant in mammals with high ...thermoregulatory demands, such as small mammals and the neonates of large mammals 1. BAT was previously believed to be present only in small mammals and human infants. How ever, active BAT was also demonstrated in adult humans in the early 1990s 23. Interestingly, in adult humans, BAT activity shows an inverse correlation with body mass index （BMI） and the percentage of body fat 45. These findings indicate that BAT may play an important role in wholebody energy metabolism, although direct evidence is still lacking. In the current study, we found that BAT transplantation improved wholebody energy metabolism and increased insulin sensitivity. In addition, BAT transplantation not only prevented highfat diet （HFD）induced weight gain but also reversed preexisting obesity. Furthermore, we showed that these effects were BATtransplantation specific, as transplantation of other tissues did not produce similar effects. To investigate the possible beneficial effects of BAT on HFDinduced obesity, we performed BAT transplan tations. BAT was dissected from strain, sex and age matched donor mice and was subcutaneously transplant ed into the dorsal interscapular region （Supplementary information, Figure S1M） of recipient mice （Figure 1A 11）. The recipient mice were then fed an HFD, which be gan immediately after the transplantation and continued for 20 weeks. BAT transplantation strikingly reduced HFDinduced weight gain in the transplanted mice com pared with shamoperated control mice that were also fed an HFD. This effect appeared as early as 4 weeks post BAT transplantation and reached a maximum at the end of the study （Figure 1A）. The weight change was accompanied by significant postBATtransplantation re ductions in the weights of large organs, such as the liver and subcutaneous adipose tissue （Supplementary infor mation, Figure S1D）. Moreover, the wholebody fat percentage was reduced （Figure 1B） despite the absence of significant changes in energy intake or energy absorption after BAT transplantation （Supplementary information, Figure S1AS1B）. BAT is a major organ that can generate large amounts of heat; it is responsible for at least 60% of nonshivering thermogenesis in coldacclimated animals 6. Therefore, we investigated whether BAT transplantation produced any effect on thermogenesis. We demonstrated that BAT transplantation not only significantly increased the core body temperature of animals under thermoneutral conditions （Figure 1C）, but also greatly increased the core body temperature of animals that were challenged by exposure to cold conditions （4 C, 6 h） （Figure IC 1D）. This elevation in body temperature was linked to an increase in energy metabolism, as evidenced by a large increase in oxygen consumption （Figure 1E） that was not accompanied by a significant change in the respiratory quotient （RQ） （Supplementary information, Figure S 1E）. Notably, the results of gene expression analyses also support the above observations： BAT transplanta Lion significantly increased the expression of fatty acid oxidationrelated genes, such as MCAD, PPARa, PGCla, CPTlfl, and UCP1, in endogenous BAT and muscle tis sue （Figure IF and Supplementary information, Figure SII）. However, similar changes were not observed in epididymal or subcutaneous fat （Supplementary in formation, Figure S 1FS 1G）. A previous research has suggested that a reduction in physical activity occurs in nouse models of obesity 7. Remarkably,
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•Sono/photodynamic treatment inhibited bacteria growth in shrimp surimi.•Sono/photodynamic treatment altered microbial community during storage.•Sono/photodynamic treatment preserved ...the quality of shrimp surimi.
Shrimp surimi is widely acknowledged as a value-added shrimp product due to its delicious taste, rich flavor, and nutrition. However, the refrigerated shrimp surimi is prone to deterioration due to rapid microbial growth during storage. The present study sought to assess the effects of curcumin-mediated sono/photodynamic treatment on bacterial spoilage and shrimp surimi quality stored at 4 °C. The total viable count (TVC), microbiota composition, and quality parameters, including the total volatile basic nitrogen (TVB-N), thiobarbituric acid reactive substance (TBARs), and pH were investigated. The results showed that the spoilage bacteria in shrimp surimi rapidly increased with a surge on day 2 during refrigeration storage. The Psychrobacter and Brochothrix were identified as the Specific Spoilage Organisms (SSOs), which were also positively correlated with TVB-N and TBARs. The results further elucidated that the sono/photodynamic treatment could significantly inhibit the growth of SSOs on the surface and interior of shrimp surimi and delay shrimp surimi quality deterioration. In conclusion, the sono/photodynamic treatment as a non-thermal sterilization method could be a reliable and potential method for inactivating spoilage microorganisms and preserving shrimp surimi quality.
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