数学核心素养下的高考命题与复习建议

本文对高考命题如何呈现和考查数学核心素养进行了分析,并就此提出了高考复习中应注意的事项.

降低解析几何运算的方法探究

从几个方面对解析几何中的运算进行探索,给出了五种降低运算量的实用方法.

柯西不等式的应用初探

柯西不等式是一个非常重要的不等式,灵活的运用它可以使一些较为困难的问题迎刃而解.给出了柯西不等式及其变式在五个方面的应用.

含参数的线性规划问题再探究

通过对含参数的线性规划问题的再探究,给出了五类含参数线性规化问题的解法.

不等式易错备忘录

归类总结了六类不等式易错问题,进行了深入分析,并给出正解.

Influence of cadmium and copper mixtures to rhizosphere bacterial communities

To study the effects of combined Cd and Cu pollution on rhizosphere bacterial community.High-throughput sequencing was used to examine the response of rhizosphere bacterial communities to heavy-metal stress under single and mixed pollution of cadmium(Cd)and copper(Cu).With additions of Cd and Cu,the mean diversity index of rhizosphere bacterial community was in the order Cu alone>Cd-Cu mixtures>Cd alone.In all Cd and Cu treatments,the dominant phyla were Proteobacteria,Actinobacteria,Chloroflexi and Acidobacteria.In the additions with different concentrations of Cd-Cu mixtures,LEfSe indicated that there were differences in the predominant species of rhizosphere bacterial communities.Some genera such as Streptomyces and Microbacterium belonging to Actinobacteria as biomarkers were significantly enriched in both control and treatments,while some genera such as Pseudoxanthomonas and Rhodopseudomonas belonging to Proteobacteria as biomarkers were observed to be enriched in the additions with single and mixture of Cd and Cu.According to the Nonmetric multidimensional scaling(NMDS)analysis,the structure of rhizosphere bacterial community was different between treatments and the CK.Principal Component Analysis(PCA)and permutational multivariate analysis of variance(PERMANOVA)showed that there were significant differences among treatments(p<0.01),and that the addition of Cu might be the primary factor affecting the composition of rhizosphere bacterial communities.

Microbial community functional structure in response to micro-aerobic conditions in sulfate-reducing sulfur-producing bioreactor

Limited oxygen supply to anaerobic wastewater treatment systems had been demonstrated as an effective strategy to improve elemental sulfur （So） recovery, coupling sulfate reduction and sulfide oxidation. However, little is known about the impact of dissolved oxygen （DO） on the microbial functional structures in these systems. We used a high throughput tool （GeoChip） to evaluate the microbial community structures in a biological desulfurization reactor under micro-aerobic conditions （DO： 0.02-0.33 rag/L）. The results indicated that the microbial community functional compositions and structures were dramatically altered with elevated DO levels. The abundances of dsrA/B genes involved in sulfate reduction processes significantly decreased （p 〈 0.05, LSD test） at relatively high DO concentration （DO： 0.33 mg/L）. The abundances of sox and fccA/B genes involved in sulfur/sulfide oxidation processes significantly increased （p 〈 0.05, LSD test） in low DO concentration conditions （DO： 0.09 mg/L） and then gradually decreased with continuously elevated DO levels. Their abundances coincided with the change of sulfate removal efliciencies and elemental sulfur （S^0） conversion efficiencies in the bioreactor. In addition, the abundance of carbon degradation genes increased with the raising of DO levels, showing that the heterotrophic microorganisms （e.g., fermentative microorganisms） were thriving under micro-aerobic condition. This study provides new insights into the impacts of micro-aerobic conditions on the microbial functional structure of sulfate- reducing sulfur-producing bioreactors, and revealed the potential linkage between functional microbial communities and reactor performance.

GeoChip-based analysis of the microbial community functional structures in simultaneous desulfurization and denitrification process

The elemental sulfur （S^0） recover）, was evaluated in the presence of hi,ate in two development models of simultaneous desulfurization and denitrification （SDD） process. At the loading rates of 0.9 kg S/（m^3.day） for sulfide and 0.4 kg N/（m^3.day） for nitrate, SO conversion rate was 91.1% in denitrifying sulfide removal （DSR） model which was higher than in integrated simultaneous desulfurization and denitrification （ISDD） model （25.6%）. A comprehensive analysis of functional diversity, structure and metabolic potential of microbial communities was examined in two models by using functional gene array （GeoChip 2.0）. GeoChip data indicated that diversity indices, community structure, and abundance of functional genes were distinct between two models. Diversity indices （Simpson＇s diversity index （1/D） and Shannon-Weaver index （H′）） of all detected genes showed that with elevated infiuent loading rate, the functional diversity decreased in ISDD model but increased in DSR model. In contrast to ISDD model, the overall abundance of dsr genes was lower in DSR model, while some functional genes targeting from nitrate-reducing sulfide-oxidizingbacteria {NR-SOB）, such as Thiobacillus denitrficans, Sulfurimonas denitrificans, and Paracoccus pantotrophus were more abundant in DSR model which were highly associated with the change of SO conversion rate obtained in two models. The results obtained in this study provide additional insights into the microbial metabolic mechanisms involved in ISDD and DSR models, which in turn will improve the overall performance of SDD process.