党参种子的离散元仿真参数标定与试验验证

为设计及优化党参机械化播种设备,提供基础仿真参数,本文对甘肃省种植的两种党参种子(渭党1号和甘党2号)通过试验法确定其基本物理参数(形状尺寸、质量密度、体积密度、千粒重、含水率)和接触力学参数(恢复系数、静摩擦系数);通过斜面滚动试验结合EDEM仿真,预测党参种子与ABS塑料板间的滚动摩擦系数;通过调整党参种子模型间的...     

气候变化条件下木瓜秀粉蚧在中国的潜在适生区预测

为明确木瓜秀粉蚧Paracoccus marginatus Williams et Granara de Willink 1922在中国的潜在适生区,基于中国820个气象站点的气象数据和未来气候变化数据,结合木瓜秀粉蚧的生物学特性,利用CLIMEX模型对该虫在中国当前气候以及未来气候条件下的潜在适生区进行预测。结果显示,木瓜秀粉蚧在中国的潜在适生区主要在南方,适生区面积占全国陆地总面积的9.07%。高适生区主要包括海南省、广东省南部、广西壮族自治区南部以及福建省和云南省小部分地区。在未来气候条件下,2050年木瓜秀粉蚧的潜在适生区将进一步扩大,适生区面积所占比例将增加至15.46%,且有向北移动的趋势。表明木瓜秀粉蚧对中国南方地区的农业潜在威胁巨大,建议将该虫增补为检疫对象,并加强检疫监管和种群动态监测。     

一种溶质运移数学模型的应用研究

土壤中溶质运移的过程、规律和机理是土壤溶质运移研究的主要内容。本文的目的是对模拟非饱和介质中水分和溶质迁移的二维数值模型SWMS－2D进行研究和验证。以硝酸盐形式存在的溶解氮是地下水中最常见的污染物，将硝态氮视为土壤溶质，考虑其根系吸收、生物固持、吸附、解吸、硝化和反硝化等作用，土壤表面即上边界条件用大气边界条件描述，下边界条件定为第一类边界条件，在田间条件下对模型作了检验。     

Host status and reaction of <Emphasis Type="Italic">Medicago truncatula</Emphasis> accessions to infection by three major pathogens of pea (<Emphasis Type="Italic">Pisum sativum</Emphasis>) and alfalfa (<Emphasis Type="Italic">Medicago sativa</Emphasis>)

Ditylenchus dipsaci, the stem nematode of alfalfa (Medicago sativa), Mycosphaerella pinodes, cause of Ascochyta blight in pea (Pisum sativum) and Aphanomyces euteiches, cause of pea root rot, result in major yield losses in French alfalfa and pea crops. These diseases are difficult to control and the partial resistances currently available are not effective enough. Medicago truncatula, the barrel medic, is the legume model for genetic studies, which should lead to the identification and characterization of new resistance genes for pathogens. We evaluated a collection of 34 accessions of M. truncatula and nine accessions from three other species (two from M. italica, six from M. littoralis and one from M. polymorpha) for resistance to these three major diseases. We developed screening tests, including standard host references, for each pathogen. Most of the accessions tested were resistant to D. dipsaci, with only three accessions classified as susceptible. A very high level of resistance to M. pinodes was observed among the accessions, none of which was susceptible to this pathogen. Conversely, a high level of variation, from resistant to susceptible accessions, was identified in response to infection by A. euteiches.     

小麦生长模型WCSODS在河南的应用研究（征文）

基于WCSODS的需求，分别设置了播期和氮肥试验，调试了小麦品种参数，检验了WCSODS在河南麦区的应用效果。结果表明： 1) WCSODS系统对河南麦区小麦生育期和产量的模拟精度较高，全生育期模拟值与实际观测值仅相差1～2d，拔节期和抽穗期模拟相差较大，分别为4～6d和2～5d，产量模拟相差4.5～20kg/667m2; 2)WCSODS以绿叶分配指数和地上部干重为基础，对小麦叶面积指数的变化动态进行模拟，它从方法上避免了因对叶面积定量计算而造成的误差，同时也考虑了叶面积指数的增大对茎蘖动态的限制，涵盖了不同茎蘖能力的小麦品种，具有较好的通用性。结果显示其对叶面积、茎蘖数及干物重的模拟值与实测值比较吻合，相关系数达到0.9877～0.9995；3)WCSODS需要改进的问题是没有考虑氮肥胁迫对小麦生长发育的影响。     

鄱阳湖湿地灰化苔草群落物种多度分布格局沿水分梯度的变化

为揭示鄱阳湖湿地苔草群落的构建机制,选择灰化苔草(Carex cinerascens)群落作为研究对象,通过设立3条样带调查不同水分梯度的群落物种多度,选用断棍模型(BSM)、生态位优先占领模型(NPM)、优势优先模型(DPM)、随机分配模型(RAM)和生态位重叠模型(ONM)5个生态位模型对群落种-多度关系进行拟合,结果表明,1)灰化苔草群落可按土壤水分划分为高湿度、中湿度和低湿度3组,分别对应从湖边、湿地中间和湿地边缘的梯度分布;2)从高到低的水分梯度上,灰化苔草群落的物种数先增加后降低,优势种多度逐渐增加,物种多度分布曲线由相对平缓变为陡峭;3)高湿度灰化苔草群落物种多度分布格局的最佳拟合模型为BSM,中、低湿度的理想模型转变为NPM。研究认为,水分条件的变化是灰化苔草群落物种多度分布格局改变的主因,随着水分梯度降低,群落构建的生态学过程由随机生态位变为生态位优先占领。研究为鄱阳湖湿地多样性保育和生态功能管理提供了理论参考。     

Prediction of irrigation return flows through a hierarchical modeling approach

The quantity of water available for irrigation is getting scarce in many countries and it assumes great importance for assured crop production, especially in view of the erratic behavior of the monsoon. Thus, there is a pressing need to improve the water efficiency of irrigation systems. One-way of improving the efficiency of the irrigation system is reusing the return flow from the irrigation system. This task requires quantification of return flow, which still remains as a grey area in irrigation water management. The estimation of return flow from the irrigation system is usually obtained using thumb rules depending upon the site-specific conditions like command area conditions and soil properties. In this paper, a hierarchical modeling technique, namely, regression tree is developed for return flow estimation. Regression tree is built through binary recursive partitioning. The effective rainfall, inflow, consumptive water demand, and percolation loss are taken as predictor variables and return flow is treated as the target variable. The applicability of the hierarchical model is demonstrated through a case study of Periyar-Vaigai Irrigation System in Tamil Nadu, India. The model performance shows a good match between the simulated and the field measured return flow values. Results of statistical analysis indicated that the correlation coefficients are high for both single as well as double crop seasons.     

新冠肺炎疫情与猪肉价格波动初探

基于2020年3月-2020年10月猪肉价格及新冠肺炎疫情指数,借助VAR模型,定量研究新冠肺炎疫情对于猪肉价格的影响。研究结果表明:新冠肺炎疫情对猪肉价格存在影响,促使猪肉价格上涨,在此基础上文章提出相应措施。     

干旱胁迫对3种冷季型草坪草光谱反射率及生理特征的影响

为探讨高光谱分析技术在草坪草水分监测上的应用,以草地早熟禾、高羊茅、多年生黑麦草为试验材料,测定了干旱胁迫下3种冷季型草坪草生理指标及光谱反射率。结果表明:随着干旱胁迫程度的加深,供试草坪草叶片相对含水量和叶绿素含量显著下降(P0.05),丙二醛含量、脯氨酸含量及敏感波段的(550和760 nm)的光谱反射率显著上升(P0.05),3种草坪草抗旱性能的强弱顺序为:高羊茅多年生黑麦草草地早熟禾。3种草坪草敏感波段光谱反射率(R_(550 nm),R_(760 nm))及高光谱参数(Rg,R0,GNDVI)与生理指标间呈显著或极显著相关,以R_(550 nm)与生理指标间的相关系数绝对值最大。同时R_(550 nm)构建了供试草坪草生理指标的估测模型,经检验,模型估测值与实测值相关性达显著或极显著水平。     

Characterization of tuberculous granulomas in different stages of progression and associated tertiary lymphoid tissue in goats experimentally infected with Mycobacterium avium subsp. hominissuis

Oral infection of goats with Mycobacterium avium subsp. hominissuis (MAH) resulted in a large variety of granulomas in organized gut-associated lymphatic tissues and intestinal lymph nodes. To characterize the cellular composition of granulomas, CD4⁺, CD8⁺, γδ, B lymphocytes and plasma, CD25⁺, CD68⁺, MHC-II⁺, Ki67⁺ and endothelial cells were labeled in consecutive frozen sections by immunohistochemistry and acid fast bacilli (AFB) by Kinyoun stain. Granulomas with extensive necrosis, little mineralization and variable numbers of AFB surrounded by many CD4⁺ T cells, but only few epitheloid macrophages were observed in severely sick goats at 2–3 mpi. They were interpreted as exuberant immune reaction. Organized granulomas with very few AFB were seen in clinically healthy goats at 13 mpi. The necrotic cores were surrounded by a zone of granulomatous infiltrate with many epitheloid macrophages and few lymphocytes. This zone was initially wide and highly vascularized and became progressively smaller. It was enclosed by an increasing layer of connective tissue. All organized granulomas were surrounded by compartimentalized tertiary lymphoid tissue. The granulomas in experimental infection of goats with MAH reflect the heterogeneity of lesions seen in mycobacterial infections of humans and ruminants and are therefore valuable for comparative research.