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991.
Xingchao Qi Yanli Liu Min Zhang Bin Gao Chengliang Li 《Journal of Soils and Sediments》2017,17(10):2438-2448
Purpose
With the increase of surfactant usages, more and more concerns were paid on their effects on the physicochemical characteristics of soils. Up to now, only few researches have examined the effects of ionic surfactants on the stability of soil structure and soil water repellency.Materials and methods
Cetyltrimethyl ammonium bromide (CTAB) as cationic surfactant and sodium dodecyl sulfate (SDS) as anionic surfactant were adopted to investigate their effects on the aggregate stability and water repellency of a silt loam soil which was sampled in Corn High-Tech Park, Huang-Huai-Hai region, China. (1) Aggregate stability: 50 g soil was mixture with 100 mL surfactant solution in a beaker. The concentrations of surfactant solutions were 0 (the blank), 200, 400, 600, 800, 1000, and 2000 mg L?1, respectively. After 30 min, the soil was sieved and divided into four fraction aggregates. (2) Soil water repellency: the concentrations of surfactant solutions were the same as experiment 1. Forty grams of soil was blended with 80 mL surfactant solution in an aluminum specimen. Drying the water by oven of 40 °C firstly and then by air, the whole period was about 1 week. After that, soil water infiltration and sorptivity were measured.Results and discussion
Compared to the blank, surfactants increased the amounts of 2–0.25 and <0.053 mm aggregates of the soil and decreased the amounts of 0.25–0.053 mm aggregates of the soil. Surfactants also increased the mean weight diameter (MWD) of the soil. Except the 200 mg L?1 treatment, CTAB promoted the soil water infiltration. All SDS treatments impeded the soil water infiltration. The soil repellency factor (R) value of the blank was 1.22, lower than the critical value of 1.95, which implied that the soil of blank treatment was free of soil water repellency. For CTAB, only 200 and 400 mg L?1 treatment’s R were higher than 1.95 while for SDS, all the treatment’s R were higher than 1.95.Conclusions
Surfactants improved the stability of soil aggregates. Soil treated with CTAB did not show the repellency, whereas SDS treatment resulted in intense water repellency compared with the wettable blank soil. Findings of this study can be used to explain the role of ionic surfactants on soil structure stability as well as on the development of water repellency in lower soil depths.992.
993.
Short-term storage and cryopreservation of Urechis unicinctus (Echiura: Urechidae) sperm 总被引:2,自引:0,他引:2
Kyoung Ho Kang Ming Yu Shao Kang Hee Kho & Zhi Feng Zhang 《Aquaculture Research》2004,35(13):1195-1201
In the present study, attempts were made to preserve Urechis unicinctus sperm at 4°C. Cryopreservation procedures were optimized for various cryoprotectants and freezing rates, equilibration times and dilution ratios. During short‐term storage, the motility of undiluted sperm was extended for 6 days of cold storage,and in 70% and 100% artificial seawater only persisted for 2 and 4 days respectively. The survival rate of undiluted sperm was maintained at a high level accordingly. After cryopreservation, the highest motility and survival rate (41.5±2.2%) were obtained in 15% dimethyl sulphoxide (Me2SO) using a freezing rate of 30°C min?1. After thawing the sperm cryopreserved in glycerol lost almost all motility. The motility and survival rate of post‐thawing sperm did not show significant differences after 8 and 15 min equilibration using 15% Me2SO as cryoprotectant; the values were significantly higher than those of 2 min equilibration. Comparisons of motility and survival rate between treatments pooled by dilution ratio showed that the effect of 1:1 ratio (sperm volume to cryoprotectant volume) was best. There was no difference between 1:3 and 1:5, and other ratioswere significantly worse. 相似文献
994.
995.
阐述了船上三相异步电动机定子绕组严重浸水后在修理时电动机的拆卸,不得通入电流进行干燥,一般只能采用灯泡(光热)干燥、烘房(烘箱)干燥和热风干燥这三种方法来进行烘干处理。 相似文献
996.
997.
闽南-台湾浅滩渔场狗母鱼类食性的研究 总被引:2,自引:2,他引:2
本文对闽南一台湾浅滩渔场狗母鱼类(多齿蛇鲻、花斑蛇鲻和大头狗母鱼)的食料生物组成、摄食强度的季节变化以及消化器官与食性等方面进行了探讨。结果表明,这三种狗母鱼类都属于游泳动物食性的底层鱼类,而且是同种残食的中级肉食性鱼类,其食料生物组成比较简单,主要摄食鱼类和头足类,还兼食长尾类、短尾类和口足类。被捕食对象的大小,随着捕食对象(多齿蛇鲻或花斑蛇鲻)叉长的增加而增大。狗母鱼类周年均有摄食,多齿蛇鲻和花斑蛇鲻在产卵盛期(3—4月)摄食强度较高。它们的消化器官的形态结构与其肉食性相适应,多齿蛇鲻和花斑蛇鲻的消化器官和食性相近似,比大头狗母鱼的食性较凶猛。 相似文献
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999.
1000.
Exploring the response differences of leaf physiology parameters to enhanced nitrogen deposition between saplings and trees is vital for predicting the variations of terrestrial ecosystem structure and function under future global climate change. In this study, the ecophysiological parameters of saplings and trees of Fraxinus mandshurica Rupr. were measured at different levels of nitrogen addition in a temperate forest. The results show that ecophysiological parameters maximum net photosynthetic rate(P_(max)), apparent quantum efficiency(a), dark respiration(R_d), light saturation point(L_(sp)), photosynthetic nitrogen use efficiency(PNUE),specific leaf area(SLA)and stomatal conductance under saturated light intensity(G_(smax)) were higher in saplings than in trees. These physiological parameters and not N_(leaf)(leaf nitrogen content)led to relatively lower P_(max) and R_d in trees. For both saplings and trees, low and median nitrogen addition(23 and 46 kg ha~(-1)a~(-1)) resulted in significant increases in Pmax, Rd, Lsp, Chl, PNUE, SLA and Gsmax. These parameters tended to decline under high additions of nitrogen(69 kg ha~(-1)a~(-1)),whereas Nleaf was always enhanced with increasing nitrogen. Variations in Pmax and Rd with increasing nitrogen were attributed to variations in the strongly related parameters of, Lsp, Chl, PNUE, SLA and Gsmax. Overall, the response sensitivity of physiological parameters to enhanced nitrogen levels was lower in trees compared with saplings. 相似文献