探析用项目管理器操作时常出现的问题

介绍了初学者利用关系数据库系统VFP的项目管理器操作时常遇到的问题,探讨了问题的解决方法。     

使用索佳SET5F-Ⅱ型电子全站仪加密图根点的精度分析

随着高、新技术的发展，使测绘仪器逐渐趋于自动化。传统的测绘方法手段逐步改进，甚至被淘汰。本文分析了使用索佳 Ｓ Ｅ Ｔ５ Ｆ－ Ⅱ型电子全站仪，采用极坐标法加密图根点的精度，供有兴趣的读者参考。     

文本信息自动分类系统ITC98(Ⅱ)--基于BP网络的文本分类子系统

设计并实现了文本信息自动分类系统ITC98的核心模块──基于BP网络的文本分类子系统。介绍系统的分类策略及根据分类问题需求确定BP网络结构和参数的方法。实例测试表明，系统分类精度和效率均达到要求。     

基于Access的烟草病虫害信息管理系统

为实现烟农对烟草病虫害信息的管理,在Windows环境下,使用Access开发了烟草病虫害信息管理系统.该系统具有烟草病虫害信息的输入、删除、修改、查询等功能,系统不仅界面友好、易学易用,且系统稳定,具有功能全面等优点.     

日粮添加不同饲料脂肪源对断奶仔猪生产性能及生产效益的影响

通过对5个独立试验的总结分析,比较添加不同脂肪源对断奶仔猪生产性能和生产效益的影响。试验结果与经济分析表明:与大豆油、膨化大豆油脂、普通脂肪粉A相比,仔猪专用功能性脂肪B是最为高效和经济的断奶仔猪用饲料脂肪。     

A new disease of greenhouse tomatoes in Israel caused by a distinct strain ofTomato apical stunt viroid (TASVd)

Using the sequential PAGE method for detection of small circular RNA molecules we isolated a viroid from greenhouse-grown tomato plants exhibiting severe stunting in Israel. The viroid was transmitted to tomato and to several other solanaceous plants by graft and mechanical inoculation, but only tomato plants showed symptoms of disease. Cloning and sequencing revealed that the viroid RNA is composed of 363 nucleotides, has 92% identity with the type strain (Ivory Coast strain) ofTomato apical stunt viroid (TASVd) and 99% identity with the Indonesian strain of this viroid. The experimental host range of TASVd-Is differs significantly from that of the type strain of TASVd. The possible epidemiological consequences leading to TASVd spread in geographically distant areas are discussed. http://www.phytoparasitica.org posting Sept. 18, 2002. Corresponding author     

黄土高原土地资源调查中几个问题的讨论

土地资源的基本特征是土地面积的有限性和土地生产能力的时空差异性。土地资源的数量、质量及其利用方式的短周期快速清查及其数据库的建立和定期更新是土地资源合理利用和科学管理的重要前提之一。本文综合运用科学实用的土地资源分类和分区、系统遥感影象和数据分析,多重系列的土地制图和数据库管理等先进技术方法,探索出一套实用化的土地资源快速清查方法。     

基于文献计量学的重大入侵害虫草地贪夜蛾的研究动态分析

为了深入了解草地贪夜蛾在全球范围的研究动态和趋势,本文利用文献计量学方法,以知网、万方、维普、Web of Science和CAB文摘数据库为数据源,对1910-2019年在国内外发表的5 030篇草地贪夜蛾文献进行了统计分析。结果表明:国内外关于草地贪夜蛾的文献数量随着时间的推移呈现整体上升趋势,20世纪90年代以来出现井喷式增长。学术期刊论文占总发文量的89.2%,Journal of Economic Entomology和《植物保护》分别是发文量最多的外文和中文期刊。在外文发文量方面,美国、巴西和墨西哥等国家的研究机构和学者名列前茅;在中文发文量方面,中国农业科学院植物保护研究所、全国农业技术推广服务中心和北京农学院位列前三。草地贪夜蛾的研究热点与其可持续防控高度相关,尤其侧重生物防治和IPM方面的研究。     

Quantitation Overcoming Matrix Effects of Lipophilic Toxins in Mytilus galloprovincialis by Liquid Chromatography-Full Scan High Resolution Mass Spectrometry Analysis (LC-HR-MS)

The analysis of marine lipophilic toxins in shellfish products still represents a challenging task due to the complexity and diversity of the sample matrix. Liquid chromatography coupled with mass spectrometry (LC-MS) is the technique of choice for accurate quantitative measurements in complex samples. By combining unambiguous identification with the high selectivity of tandem MS, it provides the required high sensitivity and specificity. However, LC-MS is prone to matrix effects (ME) that need to be evaluated during the development and validation of methods. Furthermore, the large sample-to-sample variability, even between samples of the same species and geographic origin, needs a procedure to evaluate and control ME continuously. Here, we analyzed the toxins okadaic acid (OA), dinophysistoxins (DTX-1 and DTX-2), pectenotoxin (PTX-2), yessotoxin (YTX) and azaspiracid-1 (AZA-1). Samples were mussels (Mytilus galloprovincialis), both fresh and processed, and a toxin-free mussel reference material. We developed an accurate mass-extracted ion chromatogram (AM-XIC) based quantitation method using an Orbitrap instrument, evaluated the ME for different types and extracts of mussel samples, characterized the main compounds co-eluting with the targeted molecules and quantified toxins in samples by following a standard addition method (SAM). An AM-XIC based quantitation of lipophilic toxins in mussel samples using high resolution and accuracy full scan profiles (LC-HR-MS) is a good alternative to multi reaction monitoring (MRM) for instruments with HR capabilities. ME depend on the starting sample matrix and the sample preparation. ME are particularly strong for OA and related toxins, showing values below 50% for fresh mussel samples. Results for other toxins (AZA-1, YTX and PTX-2) are between 75% and 110%. ME in unknown matrices can be evaluated by comparing their full scan LC-HR-MS profiles with those of known samples with known ME. ME can be corrected by following SAM with AM-XIC quantitation if necessary.     

Transpiration,photosynthetic responses,tissue water relations and dry mass partitioning in Callistemon plants during drought conditions

Callistemon is an Australian species used as ornamental plant in Mediterranean regions. The objective of this research was to analyse the ability of Callistemon to overcome water deficit in terms of adjusting its physiology and morphology. Potted Callistemon laevis Anon plants were grown in controlled environment and subjected to drought stress by reducing irrigation water by 40% compared to the control (irrigated to container capacity). The drought stress produced the smallest plants throughout the experiment. After three months of drought, the leaf area, number of leaves and root volume decreased, while root/shoot ratio and root density increased. The higher root hydraulic resistance in stressed plants caused decreases in leaf and stem water potentials resulting in lower stomatal conductance and indicating that water flow through the roots is a factor that strongly influences shoot water relations. The water stress affected transpiration (63% reduction compared with the control). The consistent decrease in g_s suggested an adaptative efficient stomatal control of transpiration by this species, resulting in a higher intrinsic water use efficiency (P_n/g_s) in drought conditions, increasing as the experimental time progressed. This was accompanied by an improvement in water use efficiency of production to maintain the leaf water status. In addition, water stress induced an active osmotic adjustment and led to decreases in leaf tissue elasticity in order to maintain turgor. Therefore, the water deficit produced changes in plant water relations, gas exchange and growth in an adaptation process which could promote the faster establishment of this species in gardens or landscaping projects in Mediterranean conditions.