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951.
应用基于16S rDNA的PCR-DGGE对超声波-好氧/缺氧污泥消化过程中微生物种群的多样性进行研究.通过SDS细胞裂解法提取不同时期污泥中的基因组DNA,采用通用引物进行V3区域PCR扩增,长约190 bp的PCR产物经DGGE分离后,获得污泥微生物群落的DNA特征指纹图谱,对条带进行切胶测序,使用序列数据进行同源性分析并建立系统发育树.DGGE图谱表明,在反应器运行的不同时期,微生物群落结构发生动态演替.5、10、15、20、25 d微生物相似性与0 d相比分别为61.2%、48.2%、46.4%、42.6%、41.7%,总细菌Shannon指数经历了一个从逐渐减少到趋于稳定的过程,这表明超声波改变污泥内部性质,导致微生物多样性的降低.UPGMA聚类分析将DGGE图谱区分为三大族群并对应于不同运行时期.测序结果表明,超声波-好氧/缺氧污泥消化中微生物群落主要为Firmicute、Genuscitrobacter、Bacilli、α-Proteobacteria、β-Proteobacteria. 相似文献
952.
953.
企业管理之父彼德·德鲁克说过:"任何组织中最稀缺的资源是在文化的影响下把任务执行好的人",这句话一针见血地指出了企业文化在企业管理和可持续发展中所起的关键作用.而对于核电企业来说,建立有效、卓越的企业安全文化则是它的治企之本. 相似文献
954.
公共卫生问题一直是一项重大的社会问题,关系着人类整体健康水平和生活质量,但是,近年来不断发生各种类型大小不同的公共卫生事件,使人类的生活和生存受到威胁.本文从突发公共卫生事件的表现、定义、特点出发,分析了公共卫生事件产生的机理,介绍了世界发达国家的先进经验,并对构建一个完整的公共卫生保障体系提出了见解. 相似文献
955.
956.
A juvenile lizard specimen with well-preserved skin impressions from the Upper Jurassic/Lower Cretaceous of Daohugou, Inner Mongolia, China 总被引:1,自引:0,他引:1
Lizards are now relatively well known from the Yixian Formation of northeastern China. In this study, we describe a juvenile
lizard from a fossil horizon at Daohugou, Inner Mongolia. These beds predate the Yixian Formation, and are probably Late Jurassic
or earliest Cretaceous in age. The new specimen thus documents the first lizard material from the Daohugou locality and is
the earliest lizard skeleton from China. Comparisons with developmental stages of modern lizards suggest the Daohugou lizard
is a hatchling. Although tiny, the specimen is notable in preserving exquisite skin impressions showing the variation in scalation
across the body, the shape and position of the cloacal outlet, and details of the manus and pes. These are the earliest recorded
lepidosaurian skin traces. In its general proportions and the possession of paired frontals, the small Daohugou lizard resembles
both the Yixian taxon Yabeinosaurus tenuis and the questionable Jeholacerta formosa, but it differs from the latter in scalation and, based on other characters, may be distinct from both. 相似文献
957.
Effects of long-term amendment of organic manure and nitrogen fertilizer on nitrous oxide emission in a sandy loam soil 总被引:3,自引:0,他引:3
To understand the effects of long-term amendment of organic manure and N fertilizer on N2O emission in the North China Plain, a laboratory incubation at different temperatures and soil moistures were carried out using soils treated with organic manure (OM), half organic manure plus half fertilizer N (HOM), fertilizer NPK (NPK), fertilizer NP (NP), fertilizer NK (NK), fertilizer PK (NK) and control (CK) since 1989. Cumulative N2O emission in OM soil during the 17 d incubation period was slightly higher than in NPK soil under optimum nitrification conditions (25℃ and 60% water-filled pore space, WFPS), but more than twice under the optimum denitrification conditions (35℃ and 90% WFPS). N2O produced by denitrification was 2.1-2.3 times greater than that by nitrification in OM and HOM soils, but only 1.5 times greater in NPK and NP soils. These results implied that the long-term amendment of organic manure could significantly increase the N2O emission via denitrification in OM soil as compared to NPK soil. This is quite different from field measurement between OM soil and NPK soil. Substantial inhibition of the formation of anaerobic environment for denitrification in field might result in no marked difference in N2O emission between OM and NPK soils. This is due in part to more rapid oxygen diffusion in coarse textured soils than consumption by aerobic microbes until WFPS was 75% and to low easily decomposed organic C of organic manure. This finding suggested that addition of organic manure in the tested sandy loam might be a good management option since it seldom caused a burst of N2O emission but sequestered atmospheric C and maintained efficiently applied N in soil. 相似文献
958.
959.
A new phenol-degrading bacterium with high biodegradation activity and high tolerance of phenol, strain PD 12, was isolated from the activated sludge of Tianjin Jizhuangzi Wastewater Treatment Facility in China. This strain was capable of removing 500 mg phenol/L in liquid minimal medium by 99.6% within 9 h and metabolizing phenol at concentrations up to 1100 mg/L. DNA sequencing and homologous analysis of 16S rRNA gene identified PD12 to be an Acinetobacter sp. Polyvinyl alcohol (PVA) was used as a gel matrix to immobilize Acinetobacter sp. strain PDI2 by repeated freezing and thawing. The factors affecting phenol degradation of immobilized cells were investigated, and the results showed that the immobilized cells could tolerate a high phenol level and protected the bacteria against changes in temperature and pH. Storage stability and reusability tests revealed that the phenol degradation functions of immobilized cells were stable after reuse for 50 times or storing at 4℃ for 50 d. These results indicate that immobilized Acinetobacter sp. strain PD 12 possesses a good application potential in the treatment of phenol-containing wastewater. 相似文献
960.