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41.
Thirty-seven bulk tank milk (BTM) and individual milk samples of all contributing cows were tested for Coxiella burnetii detection by a real-time PCR assay and used to assess the relationship between the BTM PCR-response and (i) the within-herd prevalence of milk-shedder cows and (ii) the proportion of heavy milk-shedder cows. The within-herd prevalence of milk-shedder cows (i) was found to be significantly higher in herds with a positive BTM and (ii) increased significantly with the estimated titre in Coxiella burnetii obtained in positive BTM. The proportion of heavy milk-shedder cows among the milk-shedder cows increased significantly with an increased estimated titre in Coxiella burnetii in positive BTM. Therefore, a real-time PCR assay applied to BTM samples collected repeatedly over time appears to be a valuable tool to assess on a larger scale the status of herds towards Coxiella shedding, and to evaluate the efficiency of control actions aimed at controlling and/or preventing Coxiella shedding in dairy herds. 相似文献
42.
Yuanbo Li Peng Zhang Mingshu Li Noman Shakoor Muhammad Adeel Pingfan Zhou Manlin Guo Yaqi Jiang Weichen Zhao BenZhen Lou Yukui Rui 《Pest management science》2023,79(1):21-36
Nanotechnology is a young branch of the discipline generated by nanomaterials. Its development has greatly contributed to technological progress and product innovation in the field of agriculture. The antimicrobial properties of nanoparticles (NPs) can be used to develop nanopesticides for plant protection. Plant diseases caused by bacterial and fungal infestations are the main types of crop diseases. Once infected, they will seriously threaten crop growth, reduce yield and quality, and affect food safety, posing a health risk to humans. We reviewed the application of metal-based nanoparticles in inhibiting plant pathogenic bacteria and fungi, and discuss the antibacterial mechanisms of metal-based nanoparticles from two aspects: the direct interaction between nanoparticles and pathogens, and the indirect effects of inducing plant resilience to disease. © 2022 Society of Chemical Industry. 相似文献
43.
生物慢滤技术适用于农村小型分散式饮水处理技术。通过五峰、秭归等地的实践,阐述了生物慢滤工艺的技术特点及净水原理,指出慢滤是一种不用任何机械动力和化学药剂的水处理方法。通过生物慢滤技术,水质满足饮用水要求,与同等规模的水处理设施比较,投资节省达90%,施工方便。慢滤池结构简单,运行管理方便,自耗水量少,出水水质好,在农村饮水工程中具有广泛的应用前景。 相似文献
44.
电渣重熔能提高钢锭的质量,从而满足特种行业的需要,其过程伴随着复杂的物理现象,存在着磁流体流动、传热和传质以及电化学等多方面的影响。通过耦合电磁以及流动和温度方程对电渣重熔过程的三维瞬态进行了数学模拟,研究了熔化速率对重熔过程的影响。结果表明:电流密度、焦耳热和电磁力都随着熔化速率的增大而增大,当熔化速率由14.4 kg/h增加到27.0kg/h,电流密度、焦耳热和电磁力最大值的增大比例超过100%。随着熔化速率的增大,温度最大值有小幅的增加,而且速度最大值的增大幅度接近50%;金属熔池深度则由27 mm增大到38 mm,不利于保证铸坯的质量。 相似文献
45.
ZHOU Zheng 《保鲜与加工》2002,(6):139-142
The processes, microstructures, properties and mechanisms of DIMOX in synthesizing Al/Al 2O 3 by Al-Mg-Si alloy are reviewed and their problems are considered mainly as following:non_homogeneous oxidation growth of Al/Al 2O 3 at the surface of melts and the porosity of Al/Al 2O 3 limites structural application of Al/Al 2O 3 composite. The mechanisms and models of microchannel,magnesium action,silicon action,and induction are outlined. Several problems which need to be noticed are pointed out,which are diffusion and transfer of oxygen in aluminium melts;the role of MgO and MgAl 2O 4 at outer layer;the reaction feature of solid_gas in the oxidation microstructures of Al_Mg_Si alloy;SiO 2 induction mechanism of silicon and its correlation with the mechanism of magnesium action in Al_Mg_Si alloy. 相似文献
46.
In this paper,solidifinG ladle of hot metal has been studied from the point ofview of heat transfer.A mathematical model,which is applied to predict the shape and the thicknessof solidifing layer,has been developed. The theoretical calculated results agree with the appliedresults in preduction. The effects of various paramenters,such as the circulating times, the inner-surface temporature of ladle and the different refractories,on the shape and the thickness ofsolidifing layer have been discussed.These are contributed to reduce the solidifing ladle of hot metal. 相似文献
47.
Zhao Changfu Feng Xiangui Li Yulan 《保鲜与加工》1991,(6):115-118
Calculations and analyses are made with the CVDA, IIW, JWES standards for the strength and welding defects of two spherical tanks of natural gas in CHONG QING. The results of the analyses indecate that though there are some problems with the welding quality in these tanks, they may still be used with the desingned presure. Now the formal working of these two spherical thanks has verified of the validity the calculations and analyses. 相似文献
48.
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50.
Dai Dayu Xu Mingxi Peng Qingchu 《保鲜与加工》1993,(3):99-103
The status quo of heauy-metals pollution in water phase of course of Long-Tan hydropower statian was eualuated by water Quality Standand Level Method. With this special method,mone objectiue and definite results were obtained. 相似文献