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921.
主要研究了北京市密云水库沉积物中重金属的总量以及形态分布特征,采用风险评价准则法(RAC)和Tucker3模型探讨沉积物中重金属的潜在危害性.结果表明,各重金属元素的平均含量都超过北京市土壤背景值,重金属元素有一定的富集.Cu有机结合态约占总量的3%~68%;Mn可交换态、碳酸盐结合态约占总量的1%~18%、7%~31%;Pb、Zn的铁锰氧化物结合态分别占总量的12%~53%、4%~27%;其它重金属均以铁锰氧化物结合态和残渣态为主,平均含量占总量的80%以上.根据RAC法得出,Mn(除采样点18)处于中等风险甚至高风险等级;Pb、Zn、Cu属从低风险到中等风险级;Ni、V、Cr、Ti的潜在生态风险较低.该结论将为北京市密云水库保护、人体健康安全保护措施的制定提供科学依据.  相似文献   
922.
本文对268株结核分枝杆菌临床分离株(包括213株利福平耐药株、55株利福平敏感株)rpoB基因RRDR区进行测序并比较分析.结果表明,在213株利福平耐药株中有200株(93.90%)在rpoB基因RRDR区发生了突变,在55株利福平敏感株中RRDR均未发生突变.突变频率最高的类型依次为:531位点(55.87%),526位点(16.43%),516位点(10.33%)和511位点(8.92%),以上四个位点的突变菌株数占所有利福平耐药株的91.55%.四川地区利福平耐药株中511位点突变频率高于全国其他地区.  相似文献   
923.
2012年10月对湖北省保康县五道峡自然保护区进行综合科学考察.考察期间采集到两栖动物蛙类标本1只,经鉴定,为无指盘臭蛙(Odorrana grahami),是湖北省两栖动物新纪录.  相似文献   
924.
Endo-β-glucanases play vital roles in the regulation of pollen tube growth. Here, a previously identified endo-l,4-β-glucanase from Lilium Iongiflorum (lily), named LlpCell, was expressed in Escherichia coli, purified, and further investigated for its physiological function. The recombinant LlpCell protein hydrolyzed carboxy-methylcellulose (CMC) and exhibited activity towards laminarin from Eisenia. arborea and 1,3:l,4-β-glucan of barley. The pH for the optimum activity was 6.0 and the value of Km calculated from CMC was 5.0 mg/mL. Adding EDTA resulted in the total loss of the enzymatic activity, and this effect could be restored by the addition of Ca^2+. Western blotting analysis showed that LlpCell protein was present in pollen grains and rehydrated pollen grains, and the amount of the protein was increased during pollen germinating, but not in the pollen tube. Consistently, the immunofluorescence labeling study with the antibody against LIpCell also indicated the presence of LIpCell at the begin-ning of germination, but not in the elongating pollen tube. Furthermore, incubation of LlpCell with pollen at the beginning of pollen germination increased the germination percentage and the length of pollen tube. All of these results suggested that LlpCell could play an important role in the regulation of lily pollen germination and the initiation of pollen tube growth.  相似文献   
925.
Previously we successfully prepared poly(vinyldiaminotriazine)(PVDT)-based non-viral vectors which complexed piasmid DNA via hydrogen bonding with adenine-thymine base pairs, in this report, surface charges and complex sizes of this system were further examined. The results showed that PVDT-based polymer could cover surface charges of DNA resulting in slightly negative or neutral complexes. It was also found that the complex sizes were governed by two events: the aggregation induced by the instability of neutral particles, and more compact complexes produced by PVDT-based polymers. In the study of cellular uptake, chlorpromazine and filipin III were used to inhibit clathrin-and caveolae-mediated endocytosis, respectively. We found that PVDT-based systems were transported into cells via a non-clathrin, non-caveolae mediated endocytosis. This special process was studied by temperature inhibition and kinetics assays. It was revealed that such a pathway was characterized by (i) a more en- ergy dependent process and (ii) a much slow transfection-effective internalization.  相似文献   
926.
A very simple molten-salt method was used to synthesize WO3 nanotubes at moderate temperature (600 ). The outer and inner diameters of the WO3 nanotubes were about 100 nm and 30 nm,with a length of dozens of micrometers. TEM and XRD analyses showed that the WO3 nanotubes were single crystal, and had monoclinic structure with the axes preferentially aligned along the [011] direction. The photoluminescence and the gas sensitivity of the nanotubes had been tested, showing that the products very well responded to acetone at 340℃.  相似文献   
927.
新疆野生甘草与栽培甘草的质量特征比较   总被引:2,自引:0,他引:2  
为比较新疆野生甘草与栽培甘草的质量差异,本文采用粉末X射线衍射(XRD)全谱分析法和紫外分光光度法对二者进行对比分析。结果表明:野生甘草和栽培甘草在2θ值2°~30°低角度范围内指纹图谱无较大特征差异;野生甘草中主要化学成分和Fe、Mg、Ca三种微量元素的含量均高于栽培甘草,且成份比例也不同——野生甘草中三种微量元素的含量比例是1.00:6.67:107.84,而栽培甘草中为1.00:8.70:36.42。  相似文献   
928.
分析了通信网络在电力管理系统中应用的设计原则,通信网的管理要求,网络管理的特点和构建网络管理的主要原则。同时结合通信技术在其中的应用,介绍了部分管理系统设计方法和原则。  相似文献   
929.
Calmodulin (CaM) and calmodulin-like protein (CaLP) are two proteins involved in biomineralization. Their localizations in Pinctada fucata mantle epithelia were studied by Western blot (WB) analysis of the nuclear/cytosol fraction of primary cultured Pinctada fucata mantle cells and immunogold electron microscopy. The results showed a completely different distribution of these two proteins at the subcellular level. CaM was distributed throughout both the nucleus and cytoplasm of the mantle epithelium but CaLP was distributed only in the cytoplasm. The functions of these two proteins in biomineralization were investigated by shell regeneration. During this process, the expressions of CaM and CaLP were greatly enhanced in different organelles of the mantle epithelium. Overexpression of these two proteins and a mutant of calmodulin-like protein (M-CaLP) that lacks an extra C-terminal tail in MC3T3-E1 promoted the mRNA expression of osteopontin, a biomineralization marker for osteoblasts. All of the results indicated that CaM and CaLP have completely different distributions in the mantle epithelium and affect the biomineralization process at different levels. The extra C-terminal tail of CaLP is important for its functions in biomineralization in Pinctada fucata.  相似文献   
930.
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