毛豆中丙溴磷残留量的测定及降解动态分析

在反复试验的基础上,建立了毛豆中丙溴磷残留量定量检测的气相色谱法。对分析方法的适合性测定结果表明,方法的回收率为86.5%～95.1%,其RSD为2.68%～6.79%,最小检测量0.00425ng,最小检出浓度为0.002mg/kg,该分析方法简便、准确、能满足实际样品分析。2004年、2005年对丙溴磷在毛豆的残留动态分析结果表明,丙溴磷在毛豆上有较高的原始沉积量,在毛豆上降解规律符合一级动力学方程,根据该方程测算,丙溴磷在毛豆中的半衰期(DT50)为3.2～3.5d,降解99%所需要的时间(T0.99)为21.3～23.5d。     

酶联免疫法测定水产品中氯霉素的残留量

[目的]探索水产品中氯霉素残留量的快速检测方法。[方法]采用酶联免疫法(ELISA)测定鱼、虾类水产品中氯霉素的残留量。[结果]检测的20个水产品中有1个阳性样品,其他样品均为阴性。ELISA方法的检出限为0.01μg/kg,平均回收率为76.1%~90.7%,相对标准偏差(RSD)≤3.21%,在0.025~1.600 ng/ml范围内有良好的线性关系,相关系数为0.997 5。[结论]该检测方法灵敏度、准确度和精密度均符合残留分析质量控制的要求,适用于大批量水产品中氯霉素残留的快速检测。     

螺虫乙酯及其代谢物在石榴上的残留检测和膳食风险评估

摘　要：[目的]建立螺虫乙酯及其4种代谢物在石榴上的残留检测方法。评估螺虫乙酯在石榴中的残留量,进行一般消费人群的长期和短期膳食暴露评估。[方法]采用QuEChERS前处理方法,样品经乙腈提取氯化钠盐析后,N-丙基乙二胺和石墨碳化黑净化,多重反应监测模式下,高效液相色谱-质谱联用仪检测,外标法定量。运用长期膳食摄入评估模型和短期膳食摄入评估模型对石榴上的螺虫乙酯进行膳食摄入风险评估。[结果]螺虫乙酯及其代谢物的标准溶液在0.005~0.5 mg/L范围内,其进样质量浓度与其对应峰面积呈良好的线性关系,相关系数r2大于0.99。当添加水平为0.01、0.1、1 mg/kg时,石榴中螺虫乙酯及其代谢物的平均回收率为74~100%,相对标准偏差（RSD）为0.92~5.3%,最低检测浓度为0.01 mg/kg。长期膳食暴露风险占每日允许摄入量（ADI）的比值为23.36%,短期膳食暴露风险占急性参考剂量（ARfD）值为0.1464%。[结论]按本研究采用的试验方案下,螺虫乙酯及其4种代谢物在石榴上的长期和短期膳食风险均小于100%,对一般人群的身体健康不会产生不可接受的影响。     

基于Mask R-CNN的玉米苗与株芯检测方法

【目的】研究基于改进Mask R-CNN的玉米苗冠层分割算法,满足精准作业中对靶施肥的识别要求,提高化肥的使用效率,减少环境污染。【方法】采集田间玉米苗图片并增强数据,生成田间数据集;使用ResNeXt50/101-FPN作为特征提取网络对分割算法进行训练,并与原始ResNet50/101-FPN的训练精度结果作对比;采用不同光照强度及有伴生杂草的玉米苗图片对比验证冠层识别算法效果。【结果】在不同光照强度下,无伴生杂草的目标平均识别精度高于95.5%,分割精度达98.1%;在有伴生杂草与玉米苗有交叉重合情况下,目标平均识别精度高于94.7%,分割精度达97.9%。检测一帧图像的平均时间为0.11 s。【结论】Mask R-CNN的玉米苗及株芯检测算法有更高的准确率和分割精度,更能适应不同光照强度及有伴生杂草的苗草交叉重合情况的目标检测。     

Attributes affecting residual benefits of N<Subscript>2</Subscript>-fixing mungbean and groundnut cultivars

Legumes grown for grain may or may not contribute net N benefits to soil and succeeding crops. An experiment was conducted to assess N₂ fixation attributes of six mungbean cultivars and two groundnut cultivars (Tainan 9 and Non-nod), which determine their residual benefit to the subsequent maize. Nodule number and dry weight of mungbeans peaked early (at 45 days) and declined thereafter strongly. In groundnut nodulation peaked later and declined only by 50% towards the final harvest. The N₂-fixing groundnut produced higher total dry matter yield than mungbeans; however, mungbeans produced higher seed yields. Dry matter harvest index and nitrogen harvest index (NHI) were higher in mungbeans (average 0.44 and 0.69) than groundnut (0.23 and 0.47, respectively, in Tainan 9). The percentage of nitrogen derived from air (%Ndfa, ¹⁵N isotope dilution) ranged from 54% to 62% in mungbeans, similar to that of groundnut (64%). However, Tainan 9 fixed more N₂ (82 kg N ha^–1) than mungbeans (35–50 kg N ha^–1) and resulted in a positive soil net N balance (+22 kg N ha^–1) while negative values were found for Non-nod groundnut and mungbeans (–3 to –12 kg N ha^–1). Maize grown after groundnut Tainan 9 had the highest total dry weight and total N uptake. This was equivalent to maize grown in fallow plots, which received 60–90 kg N ha^–1, while the respective benefits after mungbeans were 30–60 kg N ha^–1. Maize yield was directly related to the amount of residue N returned. Thus, the combination of high N yield, residue quality, %Ndfa and low NHI proved most beneficial to soil fertility and the succeeding crop.     

地膜在土壤中的残留量对茄子生育和产量的影响

经３年连续试验表明：盆栽试验６～４８ｋｇ／６６７ｍ~２的地膜残留量对茄子株高、茎粗和叶面积基本无影响。对根系增长量的影响大于地上部，随着残留量的增加＂根冠比＂值有上升趋势但未达显著水平。对氮、磷、钾吸收的影响仅在Ｐ_２Ｏ_５上有差别。田间试验表明：残留量在３～９６ｋｇ／６６７ｍ~２范围内不论早期产量、总产量还是采收果数仅差０．９％～１．５％。     

Prediction and measurement of residual stresses in injection molded parts

Residual stresses were predicted by a flow analysis in the mold cavity and residual stress distribution in the injection molded product was measured. Flow field was analyzed by the hybrid FEM/FDM method, using the Hele Shaw approximation. The Modified Cross model was used to determine the dependence of the viscosity on the temperature and the shear rate. The specific volume of the polymer melt which varies with the pressure and temperature fields was calculated by the Tait’s state equation. Flow analysis results such as pressure, temperature, and the location of the liquid-solid interface were used as the input of the stress analysis. In order to calculate more accurate gap-wise temperature field, a coordinate transformation technique was used. The residual stress distribution in the gap-wise direction was predicted in two cases, the free quenching and the constrained quenching, under the assumption that the shrinkage of the injection molded product occurs within the mold cavity and that the solid polymer is elastic. Effects of the initial flow rate, packing pressure, and mold temperature on the residual stress distribution was discussed. Experimental results were also obtained by the layer removal method for molded polypropylene.     

复杂景观区土壤有机质预测模型的尺度效应

为研究复杂景观区土壤有机质预测模型的尺度效应,探讨不同空间尺度数据综合利用的问题,本文运用回归Kriging方法对河南省登封市土壤有机质进行预测,分析了不同空间尺度数据在建模过程中的作用和影响.结果表明:土壤有机质关于高程因子的趋势属于宏观趋势,以大尺度数据拟合该趋势值效果最优;小尺度数据不适合用于拟合土壤有机质的趋势值,但揭示了小尺度残差值的空间变异细节,增强了大尺度残差值的空间结构性,能够有效提高土壤有机质预测精度.因此,景观复杂区土壤有机质预测中,应基于大尺度数据模拟趋势值,大尺度数据和小尺度数据相结合拟合残差值的空间变异函数以预测残差值,最后趋势值加上残差值得到土壤有机质预测值.     

Quantitative analysis of ruminal methanogenic microbial populations in beef cattle divergent in phenotypic residual feed intake（RFI）offered contrasting diets

Background：Methane（CH_4） emissions in cattle are an undesirable end product of rumen methanogenic fermentative activity as they are associated not only with negative environmental impacts but also with reduced host feed efficiency.The aim of this study was to quantify total and specific rumen microbial methanogenic populations in beef cattle divergently selected for residual feed intake（RFI） while offered（i） a low energy high forage（HF） diet followed by（ii） a high energy low forage（LF） diet.Ruminal fluid was collected from 14 high（H）and 14 low（L） RFI animals across both dietary periods.Quantitative real time PCR（qRT-PCR） analysis was conducted to quantify the abundance of total and specific rumen methanogenic microbes.Spearman correlation analysis was used to investigate the association between the relative abundance of methanogens and animal performance,rumen fermentation variables and diet digestibility.Results：Abundance of methanogens,did not differ between RFI phenotypes.However,relative abundance of total and specific methanogen species was affected（P〈 0.05） by diet type,with greater abundance observed while animals were offered the LF compared to the HF diet.Conclusions：These findings suggest that differences in abundance of specific rumen methanogen species may not contribute to variation in CH_4 emissions between efficient and inefficient animals,however dietary manipulation can influence the abundance of total and specific methanogen species.     

玉米芯稀酸水解残渣热解特性

在热天平分析仪上对比分析了玉米芯水解残渣、玉米芯及残渣木质素的热失重特性,借助TGA-FTIR解析了残渣木质素热解过程中主要产物的析出特性,在自制小型快速热解装置上对比考察了水解残渣和玉米芯的热解产物分布,并进一步对比分析了热解气的组分组成及热解焦的气化反应性。TGA结果表明,玉米芯热解主要集中在250～450℃,而水解残渣和残渣木质素的热解温度范围为180～800℃。TGA-FTIR分析显示,甲醇和酚类的主要析出温度区间为200～420℃,而CO和CH4主要在400℃以后析出。在热解温度550～850℃内,水解残渣的固体热解焦产率为30.35%～42.64%,远高于玉米芯热解的固体产率19.18%～26.40%,且残渣热解焦的气化反应性低于玉米芯热解焦;气体组分中CO和CO2产率较高,H2产率在温度高于650℃时明显提高。