Properties of polyurethane-poly(2,2,3,3-tetrafluoropropyl acrylate) triblock copolymer aqueous dispersion and its film cast from the dispersion

Polyurethane-poly(2,2,3,3-tetrafluoropropyl acrylate) (PU-PTFPA) triblock copolymer aqueous dispersions were synthesized by three-step polymerization. Infra-red (IR) data verify the copolymerization between PU and TFPA. The properties of copolymer aqueous dispersion and its film cast from the dispersion have been investigated by transmission electron microscopy (TEM), dynamic light scattering (DLS), and some other physical testing methods. TEM observations indicate that the morphologies of copolymer particles formed in water are almost irregular spherical shape with core-shell structure. DLS results verify that the introduction of TFPA monomer changes the average particle size of copolymer particles. The experimental data demonstrate that the factors influencing the properties of PU-PTFPA triblock copolymer aqueous dispersion and its film cast from the dispersion mainly involve PU content, DMPA content and PTFPA content.     

Growth and mortality of common octopus Octopus vulgaris reared at different stocking densities in Mediterranean offshore cages

Four ongrowing cycles of common octopus ( Octopus vulgaris ), each with two stocking densities, were carried out in an offshore area in order to evaluate the effect of the following variables on growth ( G , % body weight day⁻¹) and mortality ( M , % day⁻¹): weight ( W , 0.5–3.0 kg), temperature ( T , 14–26 °C), stocking density (SD, 6–46 kg m⁻³), size dispersion, expressed as coefficient of variation (CV, 13–42%) and significant wave height (SWH: 0.4–1.2 m). The assays were performed in an 8 m³ stainless-steel floating cage divided into two compartments of 4 m³ each. For the range of temperatures considered (14–26 °C), G depended significantly on T and SWH, with maximum G values being obtained at 18.5 °C and with an important negative effect of SWH. M depended significantly on T, W and CV, mortality being minimal at 18 °C. The two other variables had an antagonistic effect, mortality increasing with greater size dispersion – suggesting that animals should be graded throughout the process – although the effect diminished as the sizes increased. The results point towards two alternatives for the commercial ongrowing of octopus under the particular conditions of the present study: (A) two ongrowing cycles of 3.5 months to reach a final weight of 2.5 kg or (B) one 5-month cycle to reach a final weight of 3.5 kg.     

聚羧酸盐和聚氧乙烯醚磷酸酯分散剂复配体系对戊唑醇水悬浮剂分散稳定性的影响

聚羧酸盐和聚氧乙烯醚磷酸酯分散剂复配体系有利于提高农药水悬浮剂的物理稳定性。本研究选用430 g/L戊唑醇水悬浮剂 (SC) 作为研究对象,研究了聚羧酸盐分散剂850和聚氧乙烯醚磷酸酯分散剂601p复配体系的胶束流体动力学直径以及对戊唑醇SC黏度、Zeta电势、比吸光度和流变性质的影响。结果显示:单独用601p制备的戊唑醇SC的分散稳定性要高于单独用850制备的,而用两者复配体系制备的戊唑醇SC的稳定性明显高于用单一分散剂制备的。进一步研究发现,分散剂的复配比例对戊唑醇SC的物理稳定性也有不同影响,其中当m(850) : m(601p) = 1 : 1时,复配分散剂的胶束动力学直径不再变化,制得的戊唑醇SC分散稳定性最好,表现为黏度相对较小,Zeta电势为 –40.8 mV。     

南美斑潜蝇在我国发生趋势和地理差异分析

本文记述了重要的检疫性害虫南美斑潜蝇目前在我国从南到北的扩散、危害和分布形势。通过对其不同地理种群发生程度、季节动态和寄主选择性变异的分析,揭示了南美斑潜蝇在我国发生和危害的一般规律。     

石河子垦区灌耕灰漠土饱和-非饱和土壤水动力弥散试验研究

根据室内水平土柱吸渗法和易混合置换试验,对石河子垦区灌耕灰漠土饱和-非饱和土壤水动力弥散进行试验,通过理论分析和计算,得到了非饱和土壤水分扩散率和水动力弥散系数及饱和条件下的溶质弥散度,结果表明,规律性较好,且有较好的重现性,说明方法是可行的,测定数据有较好的应用参考价值。     

池养条件下1龄异育银鲫“中科3号”的生长特性

为了解池塘养殖条件下1龄异育银鲫“中科3号”的生长特性,在池塘自然水温(18.5~30.6℃)条件下,对体长(4.53±0.18)cm、体质量(2.73±0.17)g的1龄异育银鲫“中科3号”的生长性能进行了研究。试验结果:经过125 d培育,异育银鲫“中科3号”体长增长237.53%,体质量增长3312.45%;体长与体质量呈幂函数关系,关系式为W=0.0356L2.8885(R2=0.985),属等速生长型;体质量日增长量从试验开始到100 d始终呈增高态势,75~100 d的平均体质量日增长量为最高值(1.346 g/d),之后随着水温下降而降低;体质量相对增长率在0~25 d为最高(269.60%),而后逐渐降低,至125 d试验结束时为30.37%;生长指数(0.1054~0.4647)和生长常数(1.318~5.809)随着试验的进行逐渐降低;肥满度为2.6062~2.9480 g/cm^3,呈先降低、后升高、再降低的小幅波动;生长离散逐渐小幅增加。     

电解质对土壤水土迁移特征的影响

以不同浓度的Ca(NO3)2电解质溶液为水源,在大雨强高坡度下进行降雨模拟,研究紫色土水土迁移特征,试图探索在较强的物理破坏下电解质作用对土壤侵蚀的影响.结果表明:自来水降雨对土壤中的电解质产生很强的稀释效应,改变土壤表面电场而产生强大的化学分散力(水合斥力和静电排斥力),因而产生土壤强烈的分散.降雨中加入的Ca(NO3)2电解质屏蔽了土壤电场而减弱了这种化学分散力,因而减弱了土壤分散,增加了渗透,减缓了水土流失的进程,这种作用随着降雨中Ca(NO3)2浓度的增高而增强.因此土壤侵蚀的根本原因是土壤电解质及其浓度控制下的化学分散力.     

Review on the multi-scale interactions of urban forests and atmospheric particles: Affecting factors are scale-dependent among tree,stand and region

Increasing studies worldwide have examined the impacts of urban forests on mitigating atmospheric particulate matter (PM) over the past decades. These scattered studies revealed the aerodynamics of atmospheric PM deposited on urban forests, as well as the various factors influencing the PM capture and removal by urban forests. However, these evidences are varying and even contradictory, and the affecting factors do not follow a universal pattern. In addition, these studies generally have been conducted in a specific scale such as leaf, stand and city without considering the multi-scale associations and incorporations. This literature review tried to address the associations of urban forest and PM removal across single tree, stand and regional scales, and summarized the confounding factors for PM capture and removal within each scale. Particle size and local meteorology have significant impacts across scales. For an individual tree, PM capture and removal capacity are largely determined by the leaf morphology and epidermal structures, but at the stand scale, the biophysical characteristics and configurational designs of urban forests are the essential factors. At the city and regional scale, the determinants are the fraction of forest coverage, as well as background pollution levels. The literature collation emphasizes the necessity of concerning the appropriate factors responding to the specific scale when quantifying and evaluating PM capture and removal by urban forests, and warrants a multi-scale research paradigm and inclusive modeling evaluation incorporating the confounding factors from multiple scales for PM capture and removal by urban forests.     

蜡蚧轮枝菌可分散油悬浮剂对枸杞棉蚜取食行为的影响

为探究枸杞棉蚜经2种蜡蚧轮枝菌可分散油悬浮剂处理后的取食行为差异，本试验利用浸渍法对棉蚜进行室内毒力测定，并利用刺吸电位图谱技术对棉蚜在枸杞植株上的取食行为进行测定。结果表明，棉蚜的死亡率随着制剂浓度和处理时间的增加而增加，处理后棉蚜的死亡率逐渐增加，第2天2种制剂最高浓度的校正死亡率达到40%以上。5 d后2种制剂的致死作用达到最强，其最高浓度处理下的校正死亡率分别达到96.97%和95.97%。2种蜡蚧轮枝菌可分散油悬浮剂3个浓度处理的棉蚜在总记录时间为8 h内均产生7种波形，分别是非刺探波np波、路径波C波、电位下降波pd波、韧皮部分泌唾液波E1波、韧皮部被动取食波E2波、机械阻碍波F波、木质部主动取食波G波。1#制剂np波和C波随浓度的增加而增加，其余波随浓度的增加而降低，2#制剂np波和C波随浓度的增加先增加后降低，其余波随浓度的增加先降低后增加。棉蚜成虫拒食时间由长至短依次为2#制剂1×10⁶ cfu/mL浓度、1#制剂4×10⁶ cfu/mL、2#制剂4×10⁶ cfu/mL、1#制剂1×10^6<...     

Structural stability of an Alfisol under various fallow management practices in southwestern Nigeria

The effects of legume‐based soil management on soil dispersion were studied on an Alfisol between 1994 and 1995 in an experiment which was established in 1989 in southwestern Nigeria. The fallow systems, which constituted the main plots in the split‐plot experiment, included natural fallow, Pueraria phaseoloides (Roxb.) Benth, and Leucaena leucocephala Lam de Wit. The subplots were 25, 33, 50 and 100 per cent cropping intensities. Apart from indices of soil dispersion such as water‐dispersible clay and dispersion ratio, the fractal theory was applied to describe the fragmentation of soil aggregates less than 4 mm under the systems and cropping intensities. Although water dispersible clay was less than 60 g kg⁻¹ in the 0–15 cm soil depth because it was inherently low in clay content, the soil dispersion ratio was generally above 50 per cent. Also, the fractal dimensions, which ranged between 2.75 and 2.89, were similar among the fallow systems with cropping intensities for the surface soil. However, the interaction of slope position with season caused significant differences in fractal parameters, suggesting that the processes of soil degradation were different for the upper and lower slopes even with similar microaggregate distribution. The soil was inherently vulnerable to soil dispersion, although, the fallow management systems with less than 100 per cent cropping intensity would maintain soil structure at similar level as the forest. Copyright © 2001 John Wiley & Sons, Ltd.