舞三毛金藻的分类和生物学

采用光镜和电镜对引起我国养殖鱼类中毒并造成大批死亡的三毛金藻进行了详细观察,系统地研究了其特殊运动方式,形态结构,繁殖方法,孢囊,鳞片形式及纹饰,两种鞭毛的结构和功能,并对其生物学等也进行了调查研究,证明在天津地区引起鱼类中毒的是舞三毛金藻(Prymnesium saltans Massart et Conrad,1926)。同时认为鳞片结构可作为属的特征之一,但不能作为种的唯一特征。本文对舞三毛金藻亚显微结构及孢囊形态描述,进一步补充和完善了种的鉴定特征。     

The geometry of neuronal representations during rule learning reveals complementary roles of cingulate cortex and putamen

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The S-Distribution A Tool for Approximation and Classification of Univariate,Unimodal Probability Distributions

In many statistical applications a data set needs to be evaluated but there is no solid information about which probability distribution might be most appropriate. Typical solutions to this problems are: to make assumptions that facilitate mathematical treatment; to use a family of distribution functions that contains all relevant distributions as special cases; or, to employ nonparametric methods. All three solutions have disadvantages since assumptions are usually difficult to justify, families of distributions contain too many parameters to be of practical use, and nonparametric methods make it difficult to characterize data in a succinct quantitative form. The S-distribution introduced here is a compromise between the conflicting goals of simplicity in analysis and generality in scope. It is characterized by four parameters, one of which reflects its location, the second one its spread, and the remaining two its shape; transformation to a standard form reduces the number of free parameters to two. Cumulatives and densities are computed numerically in fractions of seconds, key features like quantiles and moments are easily obtained, and results can be presented in terms of parameter values. The S-distribution rather accurately models different distribution functions, including central and noncentral distributions, and thus competes in flexibility with some distribution families. As an approximation, the S-distribution provides a graphical method for demonstrating relationships between distributions, such as the relationships between central F, χ² and χ^?2 or central and noncentral t, χ^-1, and normal.     

A taxonomic investigation of theHordeum murinum Complex (Poaceae)

The purpose of this paper is to produce a classification of theHordeum murinum complex. Using an experimental design to account for the environmental component of the phenotypic variation, material from sources throughout the old-world range ofH. murinum was grown in a common environment. Eight morphological characters were measured on the resulting triplets (i.e., the central and lateral florets, glumes and rachis internode). Clustering, variance and discriminants analyses of these data suggest that there are three distinct groups. This classification is then examined for consistency with hypotheses obtained from the work of other researchers and discussed in light of the known biology of the plants. An identification key to members of the complex using the triplet characters is provided.     

The vegetation survey of Western Australia

Summary The aims and methods of the Survey in providing vegetation map coverage for the State of Western Australia on scales of 1 : 1 000 000 and 1 : 250 000 are described. The theoretical basis of the classification of vegetation units is described and a mapping notation which was evolved to characterise precisely the units mapped. It is shown that the mapping serves to define precise boundaries for phytogeographical units (botanical districts and provinces) and has contributed to a study of palaeodrainage patterns in the arid interior.

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Zusammenfassung Ziel und Methoden der Vegetationskartierung des Staates Western Australia in den Ma?st?ben 1 : 1.000.000 und 1 : 250.000 werden beschrieben, sowie die theoretische Grundlage der Klassifikation der Vegetationseinheiten und die zur genauen Charakterisierung der kartierten Einheiten entwickelten Kartierungsbezeichung. Es wird gezeigt da? die Kartierung dazu dienen kann die genauen Grenzen von pflanzengeographischen Einheiten (botanische Distrikte und Provinzen) festzustellen. Weiterhin hat die Kartierung zu einer Untersuchung der ‘Pal?o-Entw?sserung’-Systeme beigetragen.

     

Naturalness and predictivity of classifications

It is shown for binary (1, 0) data that there is a direct relationship between a new measure of predictivity in classification and the Simple Matching Coefficient. This predictivity measure is related to the variance of a cluster in phenetic space and to the mean variance of the proportion of 1 states in the members of the cluster. It can be considered a form of 'squared predictivity'. Maximizing the measure leads to Variance Clustering, and if weighted by the number of cluster members, to Sums of Squares Clustering. The relations to the Unweighted Average Pair Group and Unweighted Centroid Pair Group methods are also elucidated.     

Using long-term monitoring of fen hydrology and vegetation to underpin wetland restoration strategies

Question: How can long-term monitoring of hydrological and ecological parameters support management strategies aimed towards wetland restoration and re-creation in a complex hydrological system? Location: Newham Bog National Nature Reserve, Northumberland, UK, a site with a long history of active management, and recorded as drought-sensitive over the last 100 years. Methods: Water level readings are correlated with longer-term hydrological databases, and these data related to vegetation data collected intermittently over a 12 year period. Two analyses are undertaken: (1) a composite DCA analysis of 1993 and 2002 survey data to assess plant community transitions within the wetland and over time, and (2) analysis of recent vegetation data to explore wider vegetation gradients. This allows (3) communities to be classified using NVC classes and (4) integrated with revised Ellenberg F-values. Results: Drought impact and subsequent hydrological recovery over a 22-year period are quantified. Vegetation data display strong moisture and successional gradients. Analysis shows a shift from grassland communities toward mire communities across much of the site. Conclusion: The site is regionally unique in that it has a detailed long-term monitoring record. Hydrological data and vegetation survey have allowed the impact of the most recent ‘groundwater’drought (1989–1997) to be quantified. This information on system resilience, combined with eco-hydrological analyses of plant community-water regime/quality relationships, provide a basis for recommendations concerning conservation and restoration.     

Time‐dependent classification accuracy curve under marker‐dependent sampling

Evaluating the classification accuracy of a candidate biomarker signaling the onset of disease or disease status is essential for medical decision making. A good biomarker would accurately identify the patients who are likely to progress or die at a particular time in the future or who are in urgent need for active treatments. To assess the performance of a candidate biomarker, the receiver operating characteristic (ROC) curve and the area under the ROC curve (AUC) are commonly used. In many cases, the standard simple random sampling (SRS) design used for biomarker validation studies is costly and inefficient. In order to improve the efficiency and reduce the cost of biomarker validation, marker‐dependent sampling (MDS) may be used. In a MDS design, the selection of patients to assess true survival time is dependent on the result of a biomarker assay. In this article, we introduce a nonparametric estimator for time‐dependent AUC under a MDS design. The consistency and the asymptotic normality of the proposed estimator is established. Simulation shows the unbiasedness of the proposed estimator and a significant efficiency gain of the MDS design over the SRS design.