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301.
用浓度为10mol/L HNO3对高温固相合成的H8Nb22O59进行酸洗脱Rb+,制得吸附剂H8Nb22O59·8H2O,并对心的交换性能进行研究,同时运用XRD和SEM进行表征.结果表明:H8Nb22O59·8H2O与H8Nb22O59具有相似的结构;H8Nb22O59·8H2O对于Na+和K+的饱和吸附量接近理论吸附量2.55mmol/g,表明吸附剂对Na+和K+具有较高的亲和性;在pH为2~8的范围内,H8Nb22O59·8H2O对K+具有较高的分配系数,而分离因数随pH的升高而显著降低;H8Nb22O59·8H2O重复使用后对0仍具有较高的吸附选择性.  相似文献   
302.
以三苯基氧化膦为原料,通过硝化反应、还原反应,合成B3型单体三(3一氨基苯基)氧化膦(TAPPO).以己二酸为A2单体,利用A2+B3溶液聚合的方法,制备具有超支化结构的聚酰胺.研究反应条件对聚合物特性黏度的影响;利用傅里叶变换红外光谱(FTIR)、核磁共振谱(NMR)对含磷超支化聚酰胺进行结构表征;利用差示扫描量热法(DSC)、热重分析(TGA)测定超支化聚酰胺的热性能.  相似文献   
303.
基于Moldflow软件设计了轿车前门三角块组合型腔浇注系统.首先,对三角块进行最佳浇口分析,得到浇口匹配云图;将浇口匹配云图与注塑工艺相结合,得到最佳浇口位置;然后用浇注系统经验公式,设计出浇注系统.其次,基于Moldflow进行冷却+充填+保压+翘曲分析,验证注塑系统的可行性.最终将此浇注系统应用于注塑模设计,并生产出前门三角块合格产品.  相似文献   
304.
"非常"是一个比较特殊的语言单位,它既不属于副词家族的典型成员,同时它的意义、性质和语法功能也都不单一。在词性和词义上,"非常"经过了一个由实而虚的语法化过程。本文将从历时的角度来探究这一演变过程;并在共时层面上探讨"非常+N"中的N的语法功能及"非常+N"的语用效果。  相似文献   
305.
The perennial Medicago sativa cv. Gabes is widely grown on saline soils in Tunisian oases. Morphological and physiological analyses of two populations (Mareth and Gannouch) were conducted in order to study the effect of salinity and gamma radiation (350 Gy) interaction on two populations of this species. It has been shown that the two irradiated populations of Medicago sativa are fairly tolerant to salt at growth phase compared to the non-irradiated. Exposure to gamma irradiation (350 Gy), alone or in combination with salt stress, increased significantly (p 〈 0.001) shoot number, stem height and chlorophyll b pigment especially for the Gannouch population, while no change occurred for the Mareth population. The presence of salt to 9 g/1 affected significantly the root biomass and induced a reduction of shoot development of both control and irradiated alfalfa populations. For all treatments, plants of two populations remained able to produce and to allocate dry matter to the different organs. The survey of Na^+/K^+ ratio showed that the growth of the aerial organs of two non-irradiated populations was at least determined by a selectivity in favour of the K^+ ions (r^2 = 0.97 and r^2 = 0.59 for Mareth and Gannouch non-irradiated populations, respectively). However, the rather weak correlation detected for the irradiated populations, particularly for the irradiated Gannouch, seems to be the consequence of the effect of irradiation that improved potassium availability, essential element for growth and development. Results also showed that the two irradiated populations, especially the Mareth, accumulated Na^+ ions in its photosynthetic organs. This accumulation was associated with an improvement of foliar water content at a level of salinity around 5 g/1. Such a mechanism reflects probably an inclusive behaviour of the plants and a good aptitude to use the dominant ions (Na^+) for the osmotic adjustment. However, the non-irradiated populations are unable to adjust their internal os  相似文献   
306.
pH值对水稻土Cu^2+静电吸附与专性吸附的影响   总被引:1,自引:1,他引:0  
采用平衡液吸附法和CaCl2与HCl溶液的连续解吸法研究了太湖地区水稻土(黄泥土)在pH值为2~6范围内pH值对Cu^2+的静电吸附和专性吸附的影响以及吸附过程土壤溶液pH值的变化.研究结果表明,吸附量随pH值升高而增加.低pH值条件下利于静电吸附,吸附过程H+减少使平衡液pH值上升;高pH值条件下主要是专性吸附所控制,释放H+使平衡液pH值下降.所以土壤酸化可以增加重金属的生物有效性,降低土壤对重金属的缓冲能力.  相似文献   
307.
以九水硝酸铝和硝酸铽为反应物,无水乙醇为溶剂,柠檬酸为辅助剂的溶剂法及热处理合成Al2O3:Tb^3+绿色荧光粉体.探讨反应体系初始溶液的p H值、反应温度、掺杂量等因素对产物的光致发光性能的影响。利用XRD、SEM及荧光分光光度计等对产物的物相、形貌、发光性能进行表征和分析.实验结果表明:Al2O3:Tb^3+为γ晶型结构的粉末,用波长为240 nm的光激发产物,在544 nm处有很强的发射峰.  相似文献   
308.
Eu3+ions embedded in silica thin films codoped with SnO2 nanocrystals were fabricated by sol–gel and spin-coating methods.SnO2 nanocrystals with controllable sizes were synthesized through precisely controlling the Sn concentrations.The influences of doping and annealing conditions on the photoluminescence intensity from SnO2 nanocrystals are systematically investigated.The effective energy transfer from the defect states of SnO2nanocrystals to nearby Eu3+ions has revealed by the selective photoluminescence excitation spectra.The efficiency of the Forster resonance energy transfer is evaluated by the time-resolved photoluminescence measurements,which is about 29.1%based on the lifetime tests of the SnO2emission.  相似文献   
309.
在“(V+O1)+O2”(动宾组合+宾语)结构中,动宾组合“V+O1”和宾语O2的组合有三种音组模式,其中的“2+2”音组模式已成为优势音节组配方式。“(V+O1)+O2”结构中的宾语O2大部分是体词性宾语,少数是谓词性宾语,体词性宾语是宾语O2的典型性宾语。  相似文献   
310.
Bcl-6是滤泡辅助性T细胞(Tfh)的亚群决定转录因子,在Tfh细胞分化和功能调节过程中发挥关键作用.Bcl-6调控Tfh细胞的分子机制及其受到的精密分子调控受到广泛研究,近年来已取得了一定的进展.该文回顾了Bcl-6被鉴定为Tfh细胞亚群转录决定因子的研究历程,总结Bcl-6在Tfh细胞中的功能,综述Tfh细胞调控Bcl-6表达机制的研究进展,并对Bcl-6研究中的潜在问题和未来研究方向进行了展望.  相似文献   
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