Synergistic Effect of Lithocholic Acid with Gentamicin against Gram-Positive Bacteria but Not against Gram-Negative Bacteria

Listeria monocytogenes (L. monocytogenes) is an important Gram-positive food-borne pathogen that severely threatens public health. A checkerboard microdilution method was performed to evaluate the synergistic effect of lithocholic acid (LCA) with Gentamicin (Genta) against L. monocytogenes. BacLight LIVE/DEAD staining, scanning electron microscopy and biofilm inhibition assays were further used to explore the bactericidal effect and antibiofilm effect of this combination on L. monocytogenes. Additionally, the synergistic effects of LCA derivatives with Genta were also evaluated against L. monocytogenes, S. aureus and S. suis. The results indicated that a synergistic bactericidal effect was observed for the combined therapy of LCA at the concentration without affecting bacteria viability, with Genta. Additionally, LCA in combination with Genta had a synergistic effect against Gram-positive bacteria (L. monocytogenes, S. aureus and S. suis) but not against Gram-negative bacteria (E. coli, A. baumannii and Salmonella). BacLight LIVE/DEAD staining and scanning electron microscopy analysis revealed that the combination of LCA with Genta caused L. monocytogenes membrane injury, leading to bacteria death. We found that 8 μg/mL LCA treatment effectively improved the ability of Genta to eradicate L. monocytogenes biofilms. In addition, we found that chenodeoxycholic acid, as a cholic acid derivative, also improved the bactericidal effect of Genta against Gram-positive bacteria. Our results indicate that LCA represents a broad-spectrum adjuvant with Genta for infection caused by L. monocytogenes and other Gram-positive pathogens.     

砷的代谢机制、毒性和生物监测

砷化合物是备受关注的一类污染物,特别是饮用水中的砷污染引发了全球性的健康问题.本文综述了近年来人们对砷的代谢机制、毒性和生物监测的研究进展.砷在生物体内的代谢过程十分复杂,在氧化还原酶和甲基转移酶的参与下,产生一系列的代谢产物和中间产物.其中,砷的原始摄入形态、代谢产物及中间产物由于不同的物理化学性质,体现了不同的毒性.人类和不同的动物由于不同的砷代谢机理和甲基化能力,也表现了对砷毒性抵抗能力的差异.在生物体内,一些砷化合物与生物蛋白相互作用,影响它们的存在形式、分布和传输,是砷的生物代谢和毒理研究中不可或缺的内容.生物监测是一种直接有效的污染物健康风险评估方法.在尿液、血液、唾液、头发和指甲中砷化合物直接反映了暴露主体的砷暴露程度,这5种生物介质作为砷暴露的生物标志物各有优缺点.在砷的研究中,代谢机制和毒性的研究可以帮助选择合适的生物监测方法,做出合理准确的健康风险评估.生物监测也可促进对砷的代谢机制和毒性的理解,推断可能的代谢途径,定量毒性剂量效应,两者相互依赖相互促进.     

Stock Index Prediction Based on Time Series Decomposition and Hybrid Model

The stock index is an important indicator to measure stock market fluctuation, with a guiding role for investors’ decision-making, thus being the object of much research. However, the stock market is affected by uncertainty and volatility, making accurate prediction a challenging task. We propose a new stock index forecasting model based on time series decomposition and a hybrid model. Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (CEEMDAN) decomposes the stock index into a series of Intrinsic Mode Functions (IMFs) with different feature scales and trend term. The Augmented Dickey Fuller (ADF) method judges the stability of each IMFs and trend term. The Autoregressive Moving Average (ARMA) model is used on stationary time series, and a Long Short-Term Memory (LSTM) model extracts abstract features of unstable time series. The predicted results of each time sequence are reconstructed to obtain the final predicted value. Experiments are conducted on four stock index time series, and the results show that the prediction of the proposed model is closer to the real value than that of seven reference models, and has a good quantitative investment reference value.     

Potential Value of Wood Tar as a Natural Fungicide against Valsa mali

The Valsa canker caused by Valsa mali seriously harmed the production of East Asian apples and caused very significant economic losses. Considering the chemical residues and the improvement of people’s awareness of environmental protection, there is a need for screening new green pesticides for the control of Valsa canker. Therefore, we conducted systematic evaluations on the antifungal activity of wood tar. In this research, the effective concentration (EC₅₀) of six strains of V. mali to wood tar was determined, and the EC₅₀ ranged from 69.54 to 92.81 μg/mL. After treatment with wood tar, the hyphae of V. mali broke, swelled, and deformed; the permeability of the cell membrane increased; and the activity of pectinase reduced. Moreover, the expression levels of five genes related to pectinase also decreased significantly. In addition, the activities of phenylalanine ammonia lyase (PAL) and peroxidase (POD) of apple leaves treated with wood tar also increased. On detached apple branches, wood tar also showed therapeutic and protective activities. In the 2016–2019 field experiments, wood tar also showed good efficacy against Valsa canker and promoted the formation of callus. (In the experiments from 2016 to 2019, it can be seen that the control effect of 50% wood tar and 100% wood tar in the field is above 75% and promoted the formation of callus.) This study is the first to report the bidirectional efficacy of wood tar against Valsa mali and for trunk wound healing. The above results evidenced that wood tar has great potential to be developed as a natural alternative to commercial fungicides for the management of apple Valsa canker.     

An incremental bundle method for portfolio selection problem under second-order stochastic dominance

Numerical Algorithms - We propose a preconditioner to accelerate the convergence of the GMRES iterative method for solving the system of linear equations obtained from discretize-then-optimize...     

链式多智能体遗传算法在分布式电源全时序上优化配置

分布式电源的选址与定容是微电网研究所面临的重要问题,本文主要考虑规划地区的24-h负荷时序特性和气候特点的24-h负荷变换的情况下的DG优化配置。针对以上问题,通过链式多智能体遗传算法对其进行优化处理。首先通过算法对IEEE33节点系统进行测试,验证算法在分布式电源优化配置中的优越性,并对PG E69节点配电网进行24-h时序的全过程模拟仿真优化,结果验证了多智能体遗传算法能在分布式电源配置上的有效性,同时提高微电网接入的预测精度,加快收敛速度,改进陷入局部最优的可能性等问题,对微电网在规划选址与定容选择上提供工程参考的实用性。     

One‐pot synthesis of benzimidazole‐pyrazines and their anticancer activities

The skeleton of fused benzimidazole‐pyrazine was constructed via an Ugi/deprotection/cyclization (UDC) and hydroamination cascade reaction. This four‐step reaction was carried out in a one‐pot procedure with only one‐time column chromatography purification. The representative compound 7b exhibited 67% cell growth inhibitory activity against human breast cancer cell line MDA‐MB‐453 at the concentration of 10μM.     

Magnetic properties of a triangle double-layer graphene nanoisland: a Monte Carlo study

The European Physical Journal Plus - We analyze the solution of the Schrödinger equation with a quark–antiquark potential obtained in a paper published recently in this journal. The...     

Harvesting of a phytoplankton–zooplankton model

Considering that some phytoplankton and zooplankton are harvested for food, a phytoplankton–zooplankton model with harvesting is proposed and investigated. First, stability conditions of equilibria and existence conditions of a Hopf-bifurcation are established. Our results indicate that over exploitation would result in the extinction of the population and an appropriate harvesting strategy should ensure the sustainability of the population which is in line with reality. Furthermore, the existence of bionomic equilibria and the optimal harvesting policy are discussed. The present value of revenues is maximized by using Pontryagin’s maximum principle subject to the state equations and the control constraints. We discussed the case of optimal equilibrium solution. It is found that the shadow prices remain constant over time in optimal equilibrium when they satisfy the transversality condition. It is established that the zero discounting leads to the maximization of economic revenue and that an infinite discount rate leads to complete dissipation of economic rent. Finally, some numerical simulations are given to illustrate our results.     

Investigations on the g factors of the ground and excited states for Cu2+ ions in ZnO crystal

The g factors g _// and g _⊥ of the ground Γ₆(² T ₂) and excited Γ_4,5(² E), Γ₆(² E) states for trigonal Cu²⁺ centres in ZnO crystals are calculated from three theoretical methods, the complete diagonalization (of the energy matrix) method, the second-order perturbation method (PTM-I) and the simplified second-order perturbation method (PTM-II, this method was described in an earlier paper). These methods are based on the cluster approach in which the spin-orbit coupling parameters ζ, ζ′ and the orbital reduction factors k, k′ are calculated from a semi-empirical molecular orbital method. The crystal-field parameters used in the calculations are obtained from the superposition model and so the defect structure of Cu²⁺ centres in ZnO can be acquired. The calculated g factors from the three methods are in reasonable agreement with the experimental values and the defect structure of Cu²⁺ centres in ZnO is acquired. It appears that in some cases the approximate PTM can be applied in the studies of g factors of various states. The conditions that the PTM are ineffective are discussed.