动物源性食品中尼卡巴嗪残留量的测定

动物产品中的尼卡巴嗪药物残留已被我国及美国、日本、欧盟等国家和地区列为重点检测内容,其最大残留量为0．01mg／kg-0．2mg／kg不等。为探讨合适的检测方法,本文对国内外相关尼卡巴嗪的分析检测方法的优缺点做了分析和比较,并重点介绍了动物源性食品中尼卡巴嗪残留量检测的高效液相色谱法（HPLC）和高效液相色谱-质谱联用（HPLC-MS）法。运用这两种方法进行检测,其最低检测限可达到10μg／kg甚至0．5μg／kg,基本上符合现有相关标准的限量要求。     

驱动圆盘犁的研究与设计

驱动圆盘犁对土堡侧面和底部的土壤进行旋转滑切,将土垡底部的土壤由沟底撕裂开形成土垡,并利用圆盘的旋转将土垡抬升并翻转.为此,以研究驱动圆盘犁为目标,分析了驱动圆盘犁各几何参数和工作参数对其工作过程的影响,为驱动圆盘犁的研制提供了可靠的理论依据.通过理论分析,阐明了驱动圆盘犁的运动学特性,推导了残耕高度的计算公式.     

砷胁迫下磷用量对不同磷效率水稻苗生长、磷和砷吸收的影响

 通过盆栽试验研究了苗期砷胁迫下磷用量对磷高效水稻99011和磷低效水稻99056生长以及对P、As吸收的影响。试验设3个磷水平（0、30、150 mg/kg）和5个砷水平（0、25、50、100、200 mg/kg）。结果表明,苗期施砷显著增加了两个水稻品种地上部及地下部砷的含量,降低了两个水稻品种的株高、分蘖数、地上部及地下部干质量;施磷不但促进了两个水稻品种的生长,而且还增加了根系对砷的吸收量。当土壤砷浓度为25 mg/kg和50 mg/kg时,施用30 mg/kg磷抑制了两个水稻品种砷向地上部的转移,但施用150 mg/kg磷却促进了砷向地上部的转移。相同的处理,磷高效水稻99011地上部干质量和根干质量均显著高于磷低效水稻99056。施砷后,在30 mg/kg磷水平上磷低效水稻99056的砷转移系数最低。     

湄洲湾水域海水、沉积物中砷及重金属的含量分析

根据湄洲湾20个点位4批次水样,1次沉积物样,用原子荧光、原子吸收和多功能极谱仪测定海水和沉积物中砷及重金属的含量。采用单因子污染指数法和内梅罗综合污染指数法对湄洲湾水域海水和沉积物中的砷及重金属进行综合评价。结果表明,湄洲湾水域海水中的砷及重金属单因子污染指数Pi〈1,均符合第二类海水水质标准,内梅罗指数I〈1,总体...     

基于残差BP神经网络的6自由度机器人视觉标定

基于视觉伺服控制的机器人手眼标定和逆运动学求解一直是视觉伺服领域的核心问题。随着应用场景的逐渐复杂,传统手眼标定方法已无法满足需求;随着网络深度的增加,单一BP神经网络逆运动学求解算法的误差趋于饱和甚至变大,无法进一步提升网络性能。针对以上问题,本文将手眼标定和逆运动学求解融合为拟合目标图像坐标到机器人各关节角之间的映射关系问题,提出了一种残差BP神经网络算法。使用多个残差网络模块的方式加深BP神经网络的深度,残差模块的输入信息可以在网络内跨层传输,较好地解决了因深度增加网络模型容易产生梯度消失而无法提升网络性能的问题;通过6自由度机器人雅可比方程对逆运动学解的空间进行划分,确定了8个独立的区域,基于独立区域方法对训练数据进行处理,从而避免了多自由度机器人逆运动学多解对网络学习的影响,网络训练精度提升了2个数量级,训练速度提高了2倍。在REBot-V-6R型6自由度机器人输送线分拣系统中进行二维平面抓取和三维实物抓取实验,实验结果验证了该方法的准确性。结果表明,该方法比1层BP神经网络、3层BP神经网络、5层BP神经网络的训练精度分别提高了4个数量级、2个数量级、5个数量级,测试精度提高2个数量级;与传统标定方法相比,本文方法节约了逆运动学求解过程的计算成本,抓取位姿精度提高了1个数量级。     

残膜量对膜孔灌土壤水氮运移特性的影响

为探究土壤残膜量对膜孔灌肥液入渗土壤水氮运移特性的影响,通过室内土箱模拟试验设置0,90,180,360,720 kg/hm~2的5个残膜量水平,分析不同残膜量下膜孔灌肥液入渗累积入渗量、湿润锋运移距离、湿润体特征和水氮分布规律。结果表明:残膜对膜孔灌肥液入渗具有阻渗作用,残膜土累积入渗量较无残膜土减少10.63%～30.77%,Kostiakov模型对残膜土单位膜孔面积累积入渗量与入渗时间有较好地拟合效果;入渗前30 min,不同残膜量的垂直湿润锋运移距离差异不显著,随着入渗时间推进,残膜量与湿润锋运移距离、湿润体体积呈负相关关系。入渗结束时,含残膜土湿润体体积减小18.09%～41.96%。垂直湿润锋距离、湿润体体积与入渗时间均呈显著的幂函数关系,R~2均0.98;除膜孔中心处,相同位置含残膜的土壤含水率低于无残膜,30%高含水率区域减小。湿润体内同一深度土壤NO_3~--N和NH_4~+-N含量随残膜量增加而减小,减小幅度为4.20%～16.27%。研究结果可为残膜土下膜孔灌技术提供理论参考。     

蚯蚓与黑麦草相互作用对土壤中荧蒽去除的影响

Earthworms can promote the bioremediation of contaminated soils through enhancing plant growth and microorganism development. The individual and combined effects of earthworms and ryegrass (Lolium multiflorum Lam.) on the removal of fluoranthene from a sandy-loam alluvial soil were investigated in a 70-d microcosm experiment. The experiment was set up in a complete factorial design with treatments in four replicates: without earthworms or ryegrass (control, CK), with earthworms only (E), with ryegrass only (P), and with both earthworms and ryegrass (EP). The residual fluoranthene, microbial biomass C, and polyphenol oxidase activity in the soil changed significantly (P<0.01) with time. In general, the residual concentration of fluoranthene in the soil decreased sharply from 71.8-88.7 to 31.7-37.4 mg kg 1 in 14 d, and then decreased gradually to 19.7-30.5 mg kg 1 on the 70th d. The fluoranthene concentration left in the soil was the least with both earthworms and ryegrass, compared to the other treatments at the end of the experiment. Half-life times of fluoranthene in the E, P, and EP treatments were 17.8%-36.3% smaller than that of CK. More fluoranthene was absorbed by earthworms than ryegrass. However, the total amounts of fluoranthene accumulated in both the ryegrass and earthworms were small, only accounting for 0.01%-1.20% of the lost fluoranthene. Therefore, we assumed that microbial degradation would play a dominant functional role in fluoranthene removal from soil. We found that earthworms significantly increased microbial biomass C and polyphenol oxidase activity (P<0.01) in the presence of ryegrass at the end of the experiment. Furthermore, microbial biomass C and polyphenol oxidase activity were significantly (P<0.05) and negatively related to the residual fluoranthene concentration. This implied that earthworms might promote the removal of fluoranthene from soil via stimulating microbial biomass C and polyphenol oxidase activity.     

铁改性生物炭促进土壤砷形态转化抑制植物砷吸收

通过盆栽试验研究了不同砷污染水平(10、20、40和80 mg/kg)下,添加不同量(10、20和40 g/kg)改性前后的生物炭对土壤砷形态及植物吸收砷规律的影响。该文以棉花秸秆生物炭及改性生物炭(棉花秸秆生物炭与Fe Cl3?6H2O按质量比为20∶1)为试材,小白菜为供试植物。结果表明:生物炭(10~40 g/kg)和改性生物炭(10 g/kg)能促进小白菜的生长,在添加量分别为20和10 g/kg时生物量最大,其最大值分别为8.26和6.68 g/盆,改性生物炭在添加量为10 g/kg时高于对照组和等量未改性生物炭处理组。在砷质量分数为10和20 mg/kg的基础上,添加生物炭(10~40 g/kg)后,土壤中砷主要以残渣态形式存在;水溶态砷分别增加了0.22%~3.36%和0.96%~3.70%;改性生物炭添加对土壤砷质量分数为10 mg/kg时水溶态砷无明显影响,土壤砷质量分数为20 mg/kg时,添加改性生物炭(10~40 g/kg)后水溶态砷减少了0.12%~0.58%。在高浓度(40和80 mg/kg)砷土壤中,水溶态砷含量随着土壤中砷含量的增加而增大;添加生物炭(10~40 g/kg)后,土壤中水溶态砷分别增加了0.21%~1.56%和2.11%~8.94%,但砷主要以铝形砷形式存在,残渣态砷次之。各处理组小白菜可食部分和根部砷质量分数在添加10~40 g/kg生物炭后的变化规律不尽相同,等量的改性生物炭添加后,可食部分由18.28 mg/kg显著降低至2.66 mg/kg(P0.05),根部从133.99 mg/kg显著降低至20.21 mg/kg(P0.05)。改性生物炭与未改性生物炭相比,改性生物炭能降低土壤中水溶态砷的含量及对小白菜吸收砷有显著的抑制作用。因此,该研究可为改性生物炭在含砷土壤的修复应用中提供数据支撑与理论基础。     

Spatial variability of water retention parameters and saturated hydraulic conductivity in a calcareous Inceptisols (Khuzestan province of Iran) under sugarcane cropping

The objective of this study was to quantify inherent spatial variability and spatial cross-correlation of the van Genuchten retention parameters and saturated hydraulic conductivity (K_s) of surface and subsurface layers in a calcareous Inceptisols (Khuzestan province, Iran) under sugarcane cropping. Measurements were performed on 100-cm³ undisturbed soil cores collected at 94 locations along a 30-m-long transect with horizontal sampling distance intervals of 0.3 and 1 m at soil depths of 0–40 and 40–80 cm, respectively. Spatial variability was investigated using conventional statistics and geostatistical techniques. Coefficient of variation (CV) varied from 8.2% (for shape parameter, n at 40–80 cm depth) to 256.7% (for K_s at 0–40 cm depth). The n parameter and saturated water content, θ_s, showed a small-scale spatial heterogeneity with a maximum CV of 11.3% for the first depth and 9.2% for the second depth. Most of the hydraulic parameters at both depths showed a spatial structure and convex experimental semivariograms with dominant spherical models with the influence range of 3.2–41 m. In most cases, the extent of spatial correlation scales of cross-semivariograms for pairs of cross-correlated hydraulic variables was found to be different with reference to those relating to the direct semivariograms of correlated variables.     

铅锌尾矿中砷代谢功能基因的多样性

Microbial activities impact arsenic (As) transformation in mine tailings substantially,yet little is understood on the functional diversity of As metabolism genes.This study explored this issue using a metagenomic approach coupled by a local BLASTN procedure established in our recent studies.An assembled metagenome,recovered from hypersaline and sulfidic mine tailings,was screened for As metabolism genes aioA,arrA,arsC and arsM.This was done using a local BLASTN procedure against databases of the As metabolism genes built in this study.Putative As metabolism genes detected in the assembled metagenome included 11 arsM,20 arsC and 1 arrA full-length sequences.Together with the rRNA-based phylogenetic profiling results,a picture depicting microbial As cycling in the tailings to the genus level was obtained.It was found that most of the dominant genera in the tailings potentially harboured the genes for As reduction and/or methylation.In particular,a typical pyrite-eater present in the tailings,Thioalkalivibrio sp.,was found to harbour not only arsC and arsM,but also arrA.These results highlight the unexpected diversity of As metabolism genes in the tailings,especially considering the extremely low species diversity therein.The microbial As cycling picture established here has potential use for guiding the purposeful manipulation of As biogeochemistry in the tailings.