Risk based surveillance for early detection of low pathogenic avian influenza outbreaks in layer chickens

Current knowledge does not allow the prediction of when low pathogenic avian influenza virus (LPAIV) of the H5 and H7 subtypes infecting poultry will mutate to their highly pathogenic phenotype (HPAIV). This mutation may already take place in the first infected flock; hence early detection of LPAIV outbreaks will reduce the likelihood of pathogenicity mutations and large epidemics. The objective of this study was the development of a model for the design and evaluation of serological-surveillance programmes, with a particular focus on early detection of LPAIV infections in layer chicken flocks. Early detection is defined as the detection of an infected flock before it infects on average more than one other flock (between-flock reproduction ratio R_f < 1), hence a LPAI introduction will be detected when only one or a few other flocks are infected. We used a mathematical model that investigates the required sample size and sampling frequency for early detection by taking into account the LPAIV within- and between-flock infection dynamics as well as the diagnostic performance of the serological test used. Since layer flocks are the target of the surveillance, we also explored whether the use of eggs, is a good alternative to sera, as sample commodity. The model was used to refine the current Dutch serological-surveillance programme. LPAIV transmission-risk maps were constructed and used to target a risk-based surveillance strategy. In conclusion, we present a model that can be used to explore different sampling strategies, which combined with a cost-benefit analysis would enhance surveillance programmes for low pathogenic avian influenza.     

食品中重金属快速检测的前处理研究进展

综述了食品安全快速检测中重金属检测的常用前处理方法,对应用较多的微波消解法和酸浸提法进行总结。重点对适用于重金属快速检测的萃取技术进行评述,介绍目前应用于重金属快速检测前处理的萃取技术,并对前处理技术的发展方向进行展望。     

基于地面样方调查的小麦倒伏遥感监测研究

基于遥感技术及时获取小麦倒伏信息,对于农业部门指导小麦倒伏后的农业生产、灾害评估等具有重要意义。在鲁西、鲁西南地区小麦倒伏样方调查的基础上,选用小麦倒伏前后两期环境与灾害监测小卫星数据,探讨了利用遥感影像监测小麦倒伏的基本理论和方法。首先,根据小麦灌浆期不同组分的光谱特性,解释了倒伏小麦光谱变化的原因;其次,分析了倒伏小麦在可见光和近红外波段的光谱反射特点,寻找小麦倒伏遥感监测的敏感波段;最后,利用敏感波段建立植被指数,讨论了小麦倒伏发生程度的遥感监测问题。     

铺地黍染色体制片优化及核型分析

以铺地黍(Panicum repens)根尖为材料,比较不同的预处理、固定、前低渗、解离条件对染色体制片效果的影响,并进行核型分析。结果表明,铺地黍染色体制片的优化条件分别为：冰水混合物、4 ℃条件预处理22 h,卡诺氏固定液Ⅰ、4 ℃条件固定24 h,0.075 mol·L?1 KCl溶液在25 ℃条件前低渗15～20 min,1%果胶酶和2%纤维素酶混合酶液于25 ℃条件酶解3 h。铺地黍核型公式为2n = 2x = 40 = 34m + 6sm,未发现有随体;染色体绝对长度范围为10.87～19.21 μm,属于大型染色体;染色体相对长度组成为2n = 40 = 2L + 16M2 + 22M1;最长与最短染色体长度比值为1.77,臂比值范围为1.04～2.08;核型不对称系数为58.99%,核型类型属于2A型,其在进化类型上可能属于原始类型,为铺地黍的起源、演化及遗传育种提供了一定的理论依据和技术基础。     

黑龙江穆棱东北红豆杉自然保护区兽类多样性及东北虎猎物资源

为了深入了解黑龙江穆棱东北红豆杉国家级自然保护区兽类组成及东北虎(Panthera tigris altaica)猎物资源现状,于2016—2018年在保护区内布设40个红外相机监测点和7个大样方调查兽类多样性和分析东北虎主要猎物资源。相机监测累计照相日12250个,共获得有效独立照片1139张,从中鉴定出野生兽类4目8科17种,其中国家一级重点保护动物有东北虎和东北豹(Panthera pardus orientalis)。样方调查记录到兽类足迹261条,足迹识别出兽类4目7科10种,其中包括国家一级重点保护动物东北豹1种,东北虎主要猎物野猪(Sus scrofa)、马鹿(Cervus elaphus)、西伯利亚狍(Capreolus pygargus)和梅花鹿(Cervus nippon)4种。兽类物种相对丰富度分析表明,相对丰富度最高的是西伯利亚狍和狗獾(Meles leucurus),赤狐(Vulpes vulpes)和东北豹最低。猎物资源分析表明,保护区内分布有西伯利亚狍681只,野猪510只,马鹿35只,梅花鹿27只,4种动物的生物量分别为西伯利亚狍生物量为20210.94 kg,野猪生物量为64735.00 kg,马鹿生物量为6023.25 kg,梅花鹿生物量为1635.00 kg,保护区东北虎可捕食的主要猎物生物量为92604.19 kg。研究表明,保护区内兽类种类虽然较多,但东北虎、东北豹、梅花鹿和马鹿数据仍然较少,需要重点加强保护。     

Tree-ring δ15N of Qinghai spruce in the central Qilian Mountains of China: Is pre-treatment of wood samples necessary?

A knowledge of the tree-ring stable nitrogen isotope ratio (δ¹⁵N) can deepen our understanding of forest ecosystem dynamics by indicating the long-term availability, cycling and sources of nitrogen (N). However, the radial mobility of N blurs the interannual variations in the long-term N records. Previous studies of the chemical extraction of tree rings before analysis had produced inconsistent results and it is still unclear whether it is necessary to pre-treat wood samples from specific tree species to remove soluble N compounds before determining the δ¹⁵N values. We compared the effects of pre-treatment with organic solvents and hot ultrapure water on the N concentration and δ¹⁵N of tree rings from endemic Qinghai spruce (Picea crassifolia) growing in the interior of the central Qilian Mountains, China, during the last 60 a. We assessed the effects of different preparation protocols on the removal of the labile N compounds and investigated the need to pre-treat wood samples before determining the δ¹⁵N values of tree rings. Increasing trends of the tree-ring N concentration were consistently observed in both the extracted and unextracted wood samples. The total N removed by extraction with organic solvents was about 17.60%, with a significantly higher amount in the sapwood section (P<0.01). The δ¹⁵N values of tree rings decreased consistently from 1960 to 2019 in both the extracted and unextracted wood samples. Extraction with organic solvents increased the δ¹⁵N values markedly by about 5.2‰ and reduced the variations in the δ¹⁵N series. However, extraction with hot ultrapure water had little effect, with only a slight decrease in the δ¹⁵N values of about 0.5‰. Our results showed that the radial pattern in the inter-ring movement of N in Qinghai spruce was not minimized by extraction with either organic solvents or hot ultrapure water. It is unnecessary to conduct hot ultrapure water extraction for the wood samples from Qinghai spruce because of its negligible effect on the removal of the labile N. The δ¹⁵N variation trend of tree rings in the unextracted wood samples was not influenced by the heartwood-sapwood transition zone. We suggest that the δ¹⁵N values of the unextracted wood samples of the climate-sensitive Qinghai spruce could be used to explore the ecophysiological dynamics while focusing on the long-term variations.     

超高效液相色谱-串联质谱检测猪胆粉中黄曲霉毒素的2种前处理方法比较研究

以中医药传统药物猪胆粉作为研究对象，采用UPLC-MS/MS（超高效液相色谱-串联质谱）作为测定方法，分别通过免疫亲和柱法及QuEChERS（Quick、Easy、Cheap、Effective、Rugged、Safe）法进行样品前处理，通过考察方法的稳定性、重复性、回收率、检测限，对两种前处理方法进行评价。结果表明两种前处理方法所制样品中杂质对四种黄曲霉毒素峰均无干扰，能专属的测定黄曲霉毒素，免疫亲和柱法处理效果更佳，杂质较少。两种方法对黄曲霉毒素G族回收率结果无显著性差异，对黄曲霉毒素B族则QuEChERS法回收率更高。重复性、检测限对比结果，免疫亲和柱法优于QuEChERS法。因此两种前处理方法各有优劣，但整体而言，从操作简便，节约成本的角度来讲，QuEChERS法更优。此研究可为快速高效测定中药中的黄曲霉毒素提供思路，准确快速检验国药，对于“三农”中家畜猪的养殖，充分利用家畜副产品具有重要意义。     

样点规模与采样方法对表层土壤pH空间预测精度的影响

土壤空间预测与数字化制图的精度受土壤样点规模、采样策略、预测模型选择、目标区域地貌与成土环境复杂程度、协变量数据质量等多种因素共同制约。选择河南省为研究区,基于9种土壤样点规模、5种采样方法,应用5种最具代表性的机器学习(Machinelearning,ML)算法对耕地表层土壤pH实施空间预测与数字化制图,用以对比分析不同样点规模与采样方法对ML模型的性能表现及土壤pH预测精度的影响。结果表明：(1)当研究区土壤样点规模从200个经由400个、800个、1 200个、1 600上升至2 000个时,无论使用何种采样方法,所有ML模型的性能表现与预测精度均呈快速上升的总体趋势;当样点规模达到并超过2 000个时,大多数ML性能表现及预测精度趋于稳定,表明2 000个土壤样点可能是这些ML模型预测研究区耕地表层土壤pH的样点规模阈值。(2)5种ML模型性能表现及其土壤pH预测精度存在明显差距,基于树结构的随机森林(Random forests,RF)和Cubist表现最好,无论使用哪种采样方法,这两种模型预测结果的决定系数(R²)均可稳定在0.75～0.80之间、RM...