Mathematical models of innovation diffusion with stage structure

Mathematical models with stage structures are proposed to describe the process of awareness, evaluation and decision-making. First, a system of ordinary differential equations is presented that incorporates the awareness stage and the decision-making stage. If the adoption rate is bilinear and imitations are dominant, we find a threshold above which innovation diffusion is successful. Further, if the adoption rate has a higher nonlinearity, it is shown that there exist bistable equilibria and a region such that an innovation diffusion is successful inside and is unsuccessful outside. Secondly, a model with a time delay is proposed that includes an evaluation stage of a product. It is proved that the system exhibits stability switches. The bifurcation direction of equilibria is also discussed.     

高纯金属镨中痕量稀土杂质的电感耦合等离子体原子发射光谱分析及光谱干扰的校正

本文提出了PGS-2型平面光栅光谱仪(色散率0.18纳米,二级光谱)与PlasmaTherm ICP-5000D射频发生器联用,乙醇预去溶方式进样,同时直接测定高纯金属镨中5个痕量稀土杂质元素的方法。并讨论了基体浓度对检出限的影响以及光谱干扰及其校正方法。当样品溶液中镨的浓度为5毫克/毫升时,测定下限分别为镧、钕和钐0.002%,铈0.003%和钇0.0005%。获得了良好的实验结果,其相对标准偏差为1.2-6.2%。     

Dynamical analysis of age-structured pertussis model with covert infection

An age-structured pertussis model with covert infection is proposed to understand the effect of covert infection on the recurrence of pertussis. It is found that vaccination only for young children does not have a decisive effect on whooping cough control. It is shown that although the vaccine coverage rate is relatively high, the model has a backward bifurcation for a larger covert infection rate. In addition, sufficient conditions for the disease-free steady state to be globally asymptotically stable are obtained.     

Defect Engineering on Boron Nitride for O2 Activation and Subsequent Oxidative Desulfurization

The rational design of highly active hexagonal boron nitride (h-BN) catalysts at the atomic level is urgent for aerobic reactions. Herein, a doping impurity atom strategy is adopted to increase its catalytic activities. A series of doping systems involving O, C impurities and B, N antisites are constructed and their catalytic activities for molecular O₂ have been studied by density functional theory (DFT) calculations. It is demonstrated that O₂ is highly activated on O_N and B_N defects, and moderately activated on C_B and C_N defects, however, it is not stable on N_B and O_B defects. The subsequent application in oxidative desulfurization (ODS) reactions proves the O_N and C-doped (C_B, C_N) systems to be good choice for sulfocompounds oxidization, especially for dibenzothiophene (DBT). While the B_N antisite is not suitable for such aerobic reaction due to the extremely stable B−O^*−B species formed during the oxidation process.     

Self-assembling Dimeric and Trimeric Aggregates Based on Solvophobic and Charge-pairing Interactions

Self-assembly processes based on shape complementarity and noncovalent binding interactions are widely recognized as a fundamental principle in nature. Besides charge pairing and hydrogen bonding, hydrophobic interactions play a crucial role in water. Here we report the self-assembly of structurally simple monomers to yield defined dimeric and trimeric aggregates in highly polar media, based on ionic and solvophobic interactions. NMR, mass spectrometry and curve fitting were used to characterize these supramolecular assemblies in water–methanol solutions.     

电感耦合等离子体原子发射光谱法及离子选择电极法测定荧光级氧化钇中痕量铈的研究

文章描述了荧光级氧化钇中痕量稀土铈的测定方法,在溴酸钾存在下,5摩尔/升HNO_3介质中,以P507萃取微量铈,然后有机相用硝酸、过氧化氢反萃取、再将水相浓缩定容,然后以电感耦合等离子体原子发射光谱法分析。同时用铈的离子选择电极以二次标准加入法作第二种手段分析。样品溶液以乙醇预去溶方式引入等离子体,测定下限为2微克/克,方法简单、快速、准确。离子选择电极法测定铈离子下限1×10～(-5)摩尔/升,回收率为94-101%,方法简单,结果满意、价格便宜。     

Neurotrophin and Trk expression by cells of the human lamina cribrosa following oxygen-glucose deprivation

Background  

Ischemia within the optic nerve head (ONH) may contribute to retinal ganglion cell (RGC) loss in primary open angle glaucoma (POAG). Ischemia has been reported to increase neurotrophin and high affinity Trk receptor expression by CNS neurons and glial cells. We have previously demonstrated neurotrophin and Trk expression within the lamina cribrosa (LC) region of the ONH. To determine if ischemia alters neurotrophin and Trk protein expression in cells from the human LC, cultured LC cells and ONH astrocytes were exposed to 48 hours of oxygen-glucose deprivation (OGD). Also cells were exposed to 48 hours of OGD followed by 24 hours of recovery in normal growth conditions. Cell number, neurotrophin and Trk receptor protein expression, neurotrophin secretion, and Trk receptor activation were examined.     

The asymptotic behavior of a class of nonlinear delay difference equations

The asymptotic behavior of difference equations of type 0, \end{equation*}">is studied, where and each are continuous real functions with decreasing and increasing. Results include sufficient conditions for permanence, oscillations and global attractivity.

     

Performances of Lactobacillus brevis for Producing Lactic Acid from Hydrolysate of Lignocellulosics

Utilizing all forms of sugars derived from lignocellulosic biomass via various pretreatment and hydrolysis process is a primary criterion for selecting a microorganism to produce biofuels and biochemicals. A broad carbon spectra and potential inhibitors such as furan, phenol compounds and weak acids are two major obstacles that limited the application of dilute-acid hydrolysate of lignocellulosics in lactic acid fermentation. Two strains of bacteria isolated from sour cabbage, S3F4 (Lactobacillus brevis) and XS1T3-4 (Lactobacillus plantrum), exhibited the ability to utilize various sugars present in dilute-acid hydrolysate of biomass. The S3F4 strain also showed strong resistance to potential fermentation inhibitors such as ferulic acid and furfural. Fermentation in flasks by this strain resulted in 39.1 g/l of lactic acid from dilute acid hydrolysates of corncobs that had initial total sugar concentration of 56.9 g/l (xylose, 46.4 g/l; glucose, 4.0 g/l; arabinose, 6.5 g/l). The hydrolysate of corncobs was readily utilized by S3F4 without detoxification, and the lactic acid concentration obtained in this study was higher compared to other reports.     

Global bifurcation of solutions for a predator–prey model with prey‐taxis

We study pattern formations in a predator–prey model with prey‐taxis. It is proved that a branch of nonconstant solutions can bifurcate from the positive equilibrium only when the chemotactic is repulsive. Furthermore, we find the stable bifurcating solutions near the bifurcation point under suitable conditions. Copyright © 2014 John Wiley & Sons, Ltd.