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The availability of carbon (C), nitrogen (N), and other substrates in soil determines the growth and metabolism of microorganisms and affects the activity of extracellular enzymes. To study the activities of β -1,4-glucosidase (BG) and β -1,4- N -acetylglucosaminidase (NAG) in response to C and N availability, samples that underwent four treatments-non-fertilization (CK), chemical fertilizer (NPK), combination of organic manure and chemical fertilizer (OM), and mixture of straw and chemical fertilizer (ST)-were collected from long-term fertilization paddy soil and incubated for 0, 4, 8, and 12 months to obtain soil with different C and N availability gradients. The results showed that the dissolved organic carbon(DOC) content of OM and ST treatment samples was 2-3 times higher than that of CK and NPK treatment samples. With the increase of DOC and ammonium (NH 4 + -N) contents, the activities of BG and NAG and the contents of microbial biomass C (MBC) and N (MBN) showed no increase during incubation within each treatment. Fertilization treatments, incubation time, and their interaction are crucial factors varying the contents of DOC, NH 4 + -N, MBC, and MBN among different fertilization treatments ( P <0.01). There was a positive correlation between MBC/MBN and DOC/NH 4 + -N of OM treatment ( P <0.05) and a negative relationship between ln(BG)/ln(NAG) and DOC/NH 4 + -N of ST treatment ( P <0.01), indicating that the availability of substrates played a key role in the potential activity of extracellular enzymes in paddy soil, and the carbon-nitrogen ratio of microbial biomass was controlled by the C/N stoichiometry of substrates in soil. The results have a certain guiding significance for further study on the variation of extracellular enzyme activity in paddy soil, regulating the balance of carbon and nitrogen, and improving the fertility of paddy soil.

Objective To describe the trend of lung cancer mortality in Xuanwei City,Yunnan Province,from 1990 to 2016 and provide scientific evidence for the prevention and control of lung cancer in Xuanwei.Methods Mortality data from the 2nd(year 1990-1992)and 3rd(year 2004-2005)Retrospective Survey on Causes of Death,and the Routine Death Registration System(year 2011-2013 and 2014-2016)in Xuanwei were used in this study.We calibrated the missing report of the mortality data for the corresponding periods,calculated the crude mortality rates,standardized mortality rates and corresponding 95% CI of different types of lung cancers in the above four periods.Results The crude mortality rates of all lung cancers in Xuanwei for these four periods(1990-1992,2004-2005,2011-2013,and 2014-2016)were 34.0/100 000,89.8/100 000,102.3/100 000 and 87.2/100 000 respectively.The standardized morality rate of lung cancer remain high in Xuanwei although it has been decreasing since 2004.Morality rates of lung cancer for most age groups showed decreasing trends.The decrease has been statistically significant in the ≤ 40 year group since 2014.Except for Longchang,the standardized mortality rates have decreased in all other townships with high lung cancer prevalence.Conclusions Although the mortality rate of lung cancer remains high in Xuanwei,it has shown a decreasing trend since 2004.The decrease in lung cancer mortality in populations younger than 40 years is statistically significant.

The genetic diversity and differentiation of Lilium formolongi Hort. lines in self-inbred early generations were studied by allozyme electrophoresis. The results showed that mean allele number/locus, percentage of polymorphic loci, average observed heterozygosity and average expected heterozygosity were decreased with the increment of self-inbred generations. The purified loci, purified speed, fixed alleles and increment of genetic differentiation were different among lines because of selection and self-inbred. The mean genetic distances among F4 lines were larger than that of F3 lines, serving as another evidence to prove the differentiation among lines.