~(60)Coγ射线辐照对苹果保鲜作用的研究

用~(60)Coγ射线辐照黄香蕉苹果,研究结果表明,0.3—0.5kGy的辐照剂量有利于苹果的贮藏,该剂量范围对苹果的主要营养成分糖、Vc和苹果酸的含量损失不大,但对贮藏期间苹果的吸呼强度和乙烯的产生有一定的抑制作用,0.5kGy的辐照剂量可以杀死97％以上的轮纹病原菌。     

Changes in some physical properties of a clay soil in Central Italy following the passage of rubber tracked and wheeled tractors of medium power

The aim of this study was to evaluate the compacting effect of rubber tracked tractors in comparison to that of the traditional wheeled tractors. Macroporosity, pore shape and size distribution, bulk density, penetration resistance and saturated hydraulic conductivity were analysed in a clay soil (Vertic Cambisol) near Rome (Italy) following one and four passes on the same track of rubber tracked and wheeled tractors of medium power. The soil structure attributes were evaluated by characterising porosity by means of image analysis of soil thin sections prepared from undisturbed samples. Macroporosity decreased in the 0–10 cm layer of compacted soil, particularly after four tractor passes, due to a large reduction in the proportion of elongated pores and in their vertical continuity. The rubber tracked tractor had a more pronounced compaction effect in the surface layer (0–10 cm) than the wheeled tractor both after one and four passes; the latter treatment producing the lowest soil porosity. The same trend was observed for hydraulic conductivity, which showed a highly significant correlation with elongated pores. In the 10–20 cm layer the porosity was significantly decreased following traffic, apart from in the soil under one pass of the rubber tracked tractor. Again in this layer, the lowest values of porosity were found in soil after four passes of the rubber tracked tractor. Single and multiple passes made by the two tractors induced different effects regarding soil penetration resistance and bulk density. Increment ratio of penetration resistance after tractor passes with respect to the control was: 12.5 and 49.9% with the wheeled and 34.4 and 39.8% with the tracked after one and four passes, respectively. Increment ratio of dry bulk density values after tractor passes with respect to the control was 7.9 and 11.7% with the wheeled and 7.5 and 8.3% with the tracked after one and four passes, respectively. The tractor passes transformed the initial subangular blocky structure into a massive structure with sometimes a platy structure in the upper few centimetres. The results indicated that soil compaction following traffic with the rubber tracked tractor was generally the more pronounced. However the compacting effect of this tractor after one pass seemed to be limited to the surface layer only.     

Near Crack Line Elastoplastic Solution for an Eccentric Cracks Loaded by the Pore Water Pressure

By using near crack line analysis method and Mohr-Coulomb strength criterion,the elastic-plastic solution for near crack line of an eccentric cracks loaded by the pore water pressure under large scale yielding condition is analyzed.The elastic stress fields,the plastic stress field,the unit normal vector of the elastic-plastic boundary near the crack line,the elastic-plastic stress fields near crack line are identified.The change pattern of the length of the plastic zone and the pore water pressure is presented.Besides,the elastic-plastic analytical solution for an eccentric cracks loaded by the pore water pressure is obtained.     

The fractal characterization of pore structure for some numerical rocks and prediction of permeabilities

This paper uses the fractal theory of pore structures for porous media to study the fractal characterization of pore structure for nine numerical rocks. The results show that the fractal dimension of solid phase is usually greater than the pore fractal dimension, and its fractal scaling regions is less than the one of pore phase. This indicates that the numerical rock is an approximate two-phase fractal porous media. The porosities, volume fractions and permeabilities of nine numerical rocks are predicted. The results show that the fractal theory about pore structures of numerical rocks is effective in describing the porosity and permeability. Moreover, it seems to be more effective for solid phase in approximate two-phase fractal porous media. When predicting permeability using the fractal theory, it is very important to accurately determine the maximum pore size and the range of statistical self-similarity. By comparing the two kinds of predicted permeabilities,it is found that the FT method used by this paper is more accurate, more general and less computational cost than the PNEM method which has been worldwide used.     

“浙农1号”意蜂的生产性哺乳率

１－３日龄“浙农１号”意蜂工蜂幼虫的个体呼吸商约为０．９３３,平均生长饲料比为１．５６９,蜂王幼虫在移虫后４０－８０ｈ的呼吸商约为０．９１,生长饲料比为１．４８．根据估测的年出蜂数,计算工蜂个体平均吐浆量,从而得出“浙农１号”生产性哺乳率为２．３５－３．３６．     

中蜂和意蜂工蜂蛹期呼吸代谢的比较

中华蜜蜂和意大利蜜蜂工蜂蛹期呼吸商 (RQ)分别为 (0 .798± 0 .0 5 2 )和 (0 .84 6± 0 .0 39) .意蜂工蜂蛹期单位体重耗氧量和 CO2 释放量明显高于中蜂 ,3日龄后两者都随蛹期日龄增长而明显上升     

Vaccination of Plasmid DNA Encoding Somatostatin Gene Fused with GP5 Gene of Porcine Reproductive and Respiratory Syndrome Virus Induces Anti-GP5 Antibodies and Promotes Growth Performance in Immunized Pigs

Somatostatin （SS） is a hormone that inhibits the secretion of growth hormone. Immunization against SS can promote the growth of animals. This paper described the effects of DNA immunization on the growth and antibody response in mice and pigs immunized with a plasmid DNA encoding SS fused with GP5 of porcine reproductive and respiratory syndrome virus （PRRSV）. A fragment of 180 bp encoding partial SS gene was amplified by PCR from the genomic DNA of peripheral blood mononuclear cells of pigs, and cloned as a fusion gene with PRRSV GP5 in plasmid pISGRTK3. Three times of immunization with the resulting plasmid pISG-SS/GP5 induced anti-GP5 antibodies in BALB/c mice and pigs, as demonstrated by GP5-specific ELISA and immunoblotting. Compared with pigs immunized with empty vector pISGRTK3, the growth performance of pigs immunized with pISG-SS/GP5 was increased by 11.1% on the 13th week after the last vaccination. The results indicated the plasmid DNA encoding SS and PRRSV GP5 fusion gene elicited anti-GP5 antibodies and improved the growth performance of immunized pigs.     

黄土区切沟治理水土保持效益的研究

为研究黄土区切沟治理效益，在山西吉县进行大量的调查研究.研究表明治理切沟的防洪减沙效益十分明显，降雨量为70.4mm，30min最大雨强0.92mm/min.未治理切沟土壤侵蚀量达2389t/km     

应力路径在大型油罐软土地基加固中的应用

上海某10×104m3油罐为国内同容积罐中首次建造在软土地基上的大型油罐,采用了碎石桩、塑料排水板及充水预压综合地基处理方案。实践表明,充水预压过程中使用应力路径法控制地基稳定是一种行之有效的监测手段。     

小城镇河流沉积物无机氮迁移循环研究

通过对河流柱状沉积物在通气下和厌气下进行避光短期静置模拟培养试验，研究了小城镇河流底泥-上覆水体系无机氮的迁移特征。结果表明，沉积物有机质降解对NH4的迁移有很大影响，通气和厌气下NH4的迁移均是向上覆水方向，NO3的迁移均是向沉积物方向，由于通气条件和静水环境引起的沉积物无机氮硝化作用和反硝化作用是影响沉积物一水界面体系氮迁移的最重要因素。