Small microbialites from the basal Triassic mudstone (Tieshikou, Jiangxi, South China): Geobiologic features, biogenicity, and paleoenvironmental implications

NSFC, one Hubei Provincial Natural Science Foundation and China University of Geoscience

Subthreshold Periodic Signal Detection by Bounded Noise-Induced Resonance in the FitzHugh–Nagumo Neuron

Neurons can detect weak target signals from complex background signals through stochastic resonance (SR) and vibrational resonance (VR) mechanisms. However, random phase variation of rapidly fluctuating background signals is generally ignored in classical VR or SR studies. Here, the rapidly fluctuating background signals are modeled by bounded noise with random rapidly fluctuating phase derived from Wiener process. Then, the influences of bounded noise on the weak signal detection are discussed in the FitzHugh–Nagumo (FHN) neuron. Numerical results reveal the occurrence of bounded noise-induced single- and biresonance as well as a transition between them. Randomness in phase can enhance the adaptability of neurons, but at the cost of signal detection performance so that neurons can work in more complex environments with a wider frequency range. More interestingly, bounded noise with appropriate parameters can not only optimize information transmission but also simultaneously reduce energy consumption. Finally, the potential mechanism of bounded noise is explained

A Rapid and Efficient Strategy for Quality Control of Clinopodii herba Encompassing Optimized Ultrasound-Assisted Extraction Coupled with Sensitive Variable Wavelength Detection

Clinopodii herba is a folk herbal medicine for treatments of hemorrhagic disorders. However, there is not even a quantitative standard for clinopodii herba deposited in the Chinese Pharmacopoeia. The development of a strategy for rapid and efficient extraction and simultaneous detection of multiple components in clinopodii herba is therefore of great value for its quality evaluation. Here, a variable wavelength strategy was firstly applied to quantity multiple components by segmental monitoring by UHPLC with diode array detector following ultrasound-assisted extraction. The parameters of ultrasound-assisted extraction were optimized using single factor optimization experiments and response surface methodology by a Box–Behnken design combined with overall desirability. Subsequently, a rapid, efficient, and sensitive method was applied for simultaneous determination of eleven compounds, which represented the major and main types of components in clinopodii herba. Moreover, the performance of the validated method was successfully applied for the quality control of various batches of clinopodii herba and provided sufficient supporting data for the optimum harvest time. The Box-Behnken-optimized ultrasound-assisted extraction coupled with variable wavelength detection strategy established in this work not only improves the quality control of clinopodii herba, but also serves as a powerful approach that can be extended to quality evaluation of other traditional Chinese medicines

Boron Modified Bifunctional Cu/SiO2 Catalysts with Enhanced Metal Dispersion and Surface Acid Sites for Selective Hydrogenation of Dimethyl Oxalate to Ethylene Glycol and Ethanol

Boron (B) promoter modified Cu/SiO2 bifunctional catalysts were synthesized by sol-gel method and used to produce ethylene glycol (EG) and ethanol (EtOH) through efficient hydrogenation of dimethyl oxalate (DMO). Experimental results showed that boron promoter could significantly improve the catalytic performance by improving the structural characteristics of the Cu/SiO2 catalysts. The optimized 2B-Cu/SiO2 catalyst exhibited excellent low temperature catalytic activity and long-term stability, maintaining the average EG selectivity (Sel.EG) of 95% at 190 °C, and maintaining the average EtOH selectivity (Sel.EtOH) of 88% at 260 °C, with no decrease even after reaction of 150 h, respectively. Characterization results revealed that doping with boron promoter could significantly increase the copper dispersion, enhance the metal-support interaction, maintain suitable Cu+/(Cu+ + Cu0) ratio, and diminish metallic copper particles during the hydrogenation of DMO. Thus, this work introduced a bifunctional boron promoter, which could not only improve the copper dispersion, reduce the formation of bulk copper oxide, but also properly enhance the acidity of the sample surface, so that the Cu/SiO2 sample could exhibit superior EG selectivity at low temperature, as well as improving the EtOH selectivity at high temperature

Insights into a New Formation Mechanism of Robust Cu/SiO₂ Catalysts for Low-Temperature Dimethyl Oxalate Hydrogenation Induced by a Chelating Ligand of EDTA

The Cu/SiO2 catalyst has been widely used in dimethyl oxalate (DMO) hydrogenation due to its low cost and high efficiency. However, the reaction temperature of DMO hydrogenation is higher than the Hüttig temperature of Cu, and the smaller Cu particles are easier to agglomerate. Therefore, there is much interest in constructing a catalyst with a small particle size and strong stability. In the present work, the effect of introducing EDTA on Cu/SiO2 catalysts is systematically investigated. It not only was beneficial to form smaller copper nanoparticles (CuNPs) but also to enhance the stability of Cu species by introducing a suitable amount of EDTA. Furthermore, the surface Cu species were more evenly dispersed, and the number of active sites was increased with the introduction of EDTA; subsequently, the synergistic effect between Cu+ and Cu0 was enhanced. The best performance of 0.08E-Cu/SiO2 had been achieved in the DMO hydrogenation to ethylene glycol (EG), and the DMO conversion and EG selectivity reached 99.9% and 97.7%, respectively. Above all, the 0.08E-Cu/SiO2 catalyst exhibited a high level of stability during the 1200 h life test at 180 °C