浅谈植物分类学的“十字”学法

植物分类学的十种学习方法,包括课堂内所采用的学法和野外实习中的学法,将两者相结合,会对植物分类学的学习有所帮助。     

朱元璋的“植树令”初探

朱元璋一系列植树令是中华民族优秀文化传统的继承和发扬，历史上曾盛极一时，并在客观上有利于生态环境的改善。由于后世守成之君每况愈下，封建官僚敷衍搪塞，其成果终至荡然无存，历史的宝贵经验和沉痛教训都是今天生态文明建设的精神财富。     

水稻生长的化控技术

在我国农业现代化过程中,运用植物生长调节剂调控植物生长的化控技术已经越来越多地发挥它的作用。对不同作物及同一作物的不同生育期,所使用调节剂的种类、数量、方法均有不同变化。化控技术与良种、栽培融合形成的化控高产栽培技术体系,将推动我国农业生产再上一个新台阶。     

辣椒常规品种子叶诱导植株再生体系的建立

以辣椒常规品种保加利亚尖椒与赤研6号为材料,探讨了激素、苗龄、有机成分、AgNO3等因素对子叶再生的影响.观察到PD添加剂对常规品种辣椒离体子叶不定芽的诱导分化及伸长有明显的促进作用.保加利亚尖椒的子叶分化频率达到100%,赤研6号的分化频率达到83%.芽伸长率分别为75%与55%,生根率达到80%以上.建立了辣椒常规品种的子叶离体高效再生体系.     

Why does onlyAthalia Japonica enter summer diapause among three sympatricAthalia sawflies feeding on crucifers?

Summary This report assesses the primary factor for the evolution of summer diapause of the three species of sawfly,Athalia japonica, A. rosae andA. infumata that feed on cruciferous plants and coexist in the same area.A. japonica has two discrete spring and autumn generations, butA. rosae andA. infumata 5–6 generations. OnlyA. japonica enters summer diapause in response to the long daylengths in spring. Although these three sawflies usually feed on the same cultivated crucifers, they differ markedly in the utilization of wild crucifers. They oviposit only on young leaves.A. japonica mainly usesCardamine plants which sprout in spring and autumn.A. rosae andA. infumata primarily use hosts with new leaves all the year round, i.e. cultivated crucifers andRorippa indica, respectively. The thermal threshold for development is lower inA. japonica than in the other two species. The low heat tolerance ofA. japonica is adapted only to cool shady habitats whereCardamine grows. Presumably, summer diapause ofA. japonica is adaptation to the deterioration of the primary host plants rather than unfavorable climatic conditions. This interpretation is supported by the movement patterns of the threeAthalia sawflies, alternative means to escape from deteriorated habitat conditions.     

A Review of Plant Specific PRAs

A large number of PRA studies have been completed for specific plants at specific sites. From these studies, taken individually or collectively, many significant insights have evolved into items important to risk and safety. The content of this paper is primarily based on the material contained in the EPRI funded review of five PRA studies: Big Rock Point, Zion, Limerick, Grand Gulf, and Arkansas Nuclear One. The first three were the utility sponsored studies publicly available at the time of project initiation while the other two were deemed representative of the NRC's RSSMAP and IREP programs respectively. The results of PRA studies are usually expressed in terms of core melt frequencies, radionuclide release frequencies, and frequencies of occurrence of different reactor accident consequences (e.g., early and latent fatalities) depending on the level of PRA. These subjects are prominently addressed in this paper. One of the results of a PRA study is identification of a relatively small number of accident sequences that represent the dominant contributors to core melt. An analysis of the salient features of the dominant accident sequences from eleven PRA's yielded a characterization of accident sequence categories discussed at some length. Impact of external events is discussed very briefly. Next to an explicit quantification of public risk or core melt frequency, the identification of specific safety concerns and the evaluation of possible solutions to implement risk management are probably the best recognized and most widely used applications of PRA. Several illustrative examples are briefly discussed. Human interactions are extremely important contributors to safety and reliability of the plants. A review of PRA studies concluded that it was necessary to account for five types of human interactions; some of which may mitigate while others may exacerbate an accident sequence.     

An analysis of two probabilistic model induction techniques

Two probabilistic model induction techniques, cart and constructor, are compared, via a series of experiments, in terms of their ability to induce models that are both interpretable and predictive. The experiments show that, although both algorithms are able to deliver classifiers with predictive performance close to that of the optimal Bayes rule,constructor is able to generate a probabilistic model that is more easily interpretable than the cart model. On the other hand, cart is a more mature algorithm and is capable of handling many more situations (e.g., real-valued training sets) thanconstructor. A variety of characteristics of both algorithms are compared, and suggestions for future research are made.     

Public Distrust and Hazard Management Success at the Rocky Flats Nuclear Weapons Plant

Based on experience gained while serving a public oversight commission appointed by the governor of Colorado, hazard management at the Department of Energy's Rocky Flats nuclear weapons plant is reviewed. Specific reference is made to the plant's history of controversy, its defense-in-depth strategy of hazard control, occupational health issues, public exposure to plutonium, and the assessment of low-probability, high-consequence risks. This leads to the conclusion that Rocky Flats is, by any objective standard, a hazard management success. It follows that public distrust of Rocky Flats arises as much from fear and loathing of nuclear weapons themselves as from the manufacturing process by which they are made.     

Technical Uncertainty in Quantitative Policy Analysis — A Sulfur Air Pollution Example

Expert judgments expressed as subjective probability distributions provide an appropriate means of incorporating technical uncertainty in some quantitative policy studies. Judgments and distributions obtained from several experts allow one to explore the extent to which the conclusions reached in such a study depend on which expert one talks to. For the case of sulfur air pollution from coal-fired power plants, estimates of sulfur mass balance as a function of plume flight time are shown to vary little across the range of opinions of leading atmospheric scientists while estimates of possible health impacts are shown to vary widely across the range of opinions of leading scientists in air pollution health effects.     

Ordinal preference representations

Ordinal preferences have several advantages over the traditional cardinal expressions of preference. Three different representations of ordinal preferences useful in multi-participant modelling are presented, and their features compared. One approach is thepayoff representation that is based on an ordinal normal form game. A second representation of ordinal preferences is thepreference vector, based on the option form of the game. The option form consists of a list of players, with each player followed by the options under its control. The third representation of ordinal preferences is thepreference tree. A preference tree is an implied binary tree that captures the information of preference vector in a more compact manner by making use of its lexicographic structure. The preference tree offers considerable compactness and computational efficiency over the other two approaches.