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利用常规天气图、NCEP全球分析资料(FNL)、自动站观测资料、新一代多普勒雷达资料,对2013年7月18日05:00 ~09:00濮阳市出现的一次短历时强降水天气过程进行了诊断分析.结果表明,这次强降水过程是由高空三层的暖切变、584 dagpm线边缘的暖湿气流、地面西南倒槽北上及华北冷空气向南扩散共同影响造成的.高空三层东西向暖切变在濮阳市上空的重合,既提供了动力抬升,又有利于暖湿气流的辐合及上升;高空三层西南暖湿气流的叠加,提供了深厚的水汽通道;西南倒槽顶部冷暖空气交汇处具有较大的斜压性,有利于强降水的产生.强降水发生时高空有充足的水汽输送及其在濮阳上空的辐合,该地又有近于饱和的湿层配合,为强降水的产生提供了充足的水汽条件.在湿度层结深厚且具有热力不稳定、对流不稳定的气层中,有垂直风切变的触发,很容易产生短时强天气.濮阳位于等θse线密集带南部边缘大值区内,斜压性大,有利于气旋性涡度发展,致使上升运动增强,可使降水强度增大. 相似文献
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[目的]为了提高植原体膜蛋白Imp基因在E.coliBL21(DE3)中的表达量,优化Imp基因的原核表达条件。[方法]通过设计正交试验,考察不同的培养条件对工程菌E.coliBL21(DE3)-pET-28a(+)-Imp的影响。在获得最佳培养条件的基础上考察不同诱导条件对Imp蛋白表达量的影响。利用SDS-PAGE和GeneTools凝胶分析软件分析融合蛋白Imp的表达量。[结果]表达条件优化结果表明,最佳培养条件为:温度37℃,pH7.0,装液量20%,振荡速度200r/min。最佳诱导条件为:温度37℃,起始OD600≈1.5,IPTG终浓度0.1mmol/L,诱导培养时间6h。[结论]在最佳条件下Imp表达量达到70.98mg/L,确定了Imp融合蛋白在大肠杆菌的优化表达条件。 相似文献
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Vegetable soils with high nitrogen input are major sources of nitrous oxide (N2O) and nitric oxide (NO), and incorporation of the nitrification inhibitor 3, 4-dimethylpyrazole phosphate (DMPP) into soils has been documented to effectively reduce emissions. However, the efficiency of DMPP in terms of soil N2O and NO mitigations varies greatly depending on soil temperature and moisture levels. Thus, further evaluations of DMPP efficiency in diverse environments are required to encourage widespread application. A laboratory incubation study (28 d) was established to investigate the interactive effects of DMPP, temperature (15, 25, and 35 ℃), and soil moisture (55% and 80% of water-holding capacity (WHC)) on net nitrification rate, N2O and NO productions, and gene abundances of nitrifiers and denitrifiers in an intensive vegetable soil. Results showed that incubating soil with 1% DMPP led to partial inhibition of the net nitrification rate and N2O and NO productions, and the reduction percentage of N2O production was higher than that of NO production (69.3% vs. 38.2%) regardless of temperature and soil moisture conditions. The increased temperatures promoted the net nitrification rate but decreased soil N2O and NO productions. Soil moisture influenced NO production more than N2O production, decreasing with the increased moisture level (80%). The inhibitory effect of DMPP on cumulative N2O and NO productions decreased with increased temperatures at 55% WHC. Conversely, the inhibitory effect of DMPP on cumulative N2O production increased with increased temperatures at 80% WHC. Based on the correlation analyses and automatic linear modeling, the mitigation of both N2O and NO productions from the soil induced by DMPP was attributed to the decreases in ammonia-oxidizing bacteria (AOB) amoA gene abundance and NO-2-N concentration. Overall, our study indicated that DMPP reduced both N2O and NO productions by regulating the associated AOB amoA gene abundance and NO-2-N concentration. These findings improve our insights regarding the implications of DMPP for N2O and NO mitigations in vegetable soils under various climate scenarios. 相似文献
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本研究选用72只6周龄京白鸡,随机分为A、B、C、D、E和F六组,分别饲喂钙、锌水平不同的日粮(各组锌、钙分别为:21.5ppm,0.95%;21.5ppm,1.95%;21.5ppm,2.95%;49ppm,0.95%;49ppm,1.95%;49ppm,2.95%),进行为期30天的饲养试验。试验中观察增重和临床变化;饲养结束时,取全血、羽毛、胫骨、肝和肾等组织的样本,测定其锌、钙、铁、铜、锰等元素的含量。试验结果是,D组增重和发育良好;A组稍次于D组;其他各组出现程度不同的临床症状,并且这些组所测组织锌含量明显低于D、A组,且其羽毛铁、骨铜、羽毛锰含量明显升高,而羽毛铜、肾铜及肾锰则显著降低。 相似文献
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Nelmarie Saayman Craig Morris Hannes Botha 《African Journal of Range and Forage Science》2016,33(4):225-233
The Succulent Karoo, one of two arid biodiversity hotspots in the world, is known for its high plant species richness, but little is known about the influence of topography and how it mediates the potentially deleterious effects of grazing. Changes in vegetation species composition, cover and species diversity were examined along piosphere gradients on northerly slopes, bottomlands and low-lying plains on 45 farms. Landscapes differed in the plant speciesand life-form composition, species richness and cover, with the more species-rich, heterogeneous grassy northerly slopes distinct from the plains and bottomlands, which were dominated by Pteronia pallens, Psilocaulon junceum and Drosanthenum spp. with more annual and ephemeral species. Overall, species richness declined linearly with decreasing rangeland condition. A weak grazing effect was detected only on the north-facing slopes, where shrubs and grass decreased with intense grazing. Years of overgrazing have resulted in the widespread dominance of P. pallens, especially on the plains and bottomlands, rendering them insensitive to grazing. The current condition of the northern slopes should be maintained and managed such that palatable species can spread to more degraded areas of the landscape. 相似文献