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301.
Citrulline, one of the forms in which fixed nitrogen is assimilated in free-living blue-green algae and additionally in the blue-green algae/cycad symbiosis in Macrozamia, is similarly assimilated in the nitrogen fixing root nodules of Alnus glutinosa. By investigating the localisation of ornithine carbamoyl transferase in both cases it has been shown that in these symbiotic systems the ornithine carbamoyl transferase is only active in host tissue. This suggests that the host exerts an influence on the assimilation of fixed nitrogen in the microsymbiont resulting in the blocking of the enzyme trans-carbamylase with the subsequent excretion of the fixed nitrogen as ammonia to the host for further assimilation. This is discussed in the light of work on nitrogen metabolism in other symbiotic relationships involving nitrogen fixing organisms, where the effect of altering the habitat of the micro-organism has in fact resulted in a change in its metabolism. 相似文献
302.
A model has been developed which predicts the numbers of immature and adult workers, males and queens, in a Paravespula vulgaris colony throughout a season. This model colony is based on the rate of egg lay of the queen which is approximated by a skewed normal frequency curve. Larval and pupal numbers are predicted by applying mean developmental times to the eggs produced. For workers, adult numbers are produced by modifying pupal numbers by adult longevity, while adult males and queens are obtained directly from their respective pupal numbers. Data generated by the model compare favourably with published observations.Changes in the larva : worker ratio through the season affecting adult longevity and immature stage developmental times are discussed. The total number of adults produced per worker (Ro) varies throughout the season following a skewed normal frequency distribution. Adult queens and males accounted for only 15% of the total seasonal egg production.This model could easily be adapted to deal with population changes in colonies of other eusocial wasps. 相似文献
303.
The use of intrinsic diversity profiles is recommended for ranking biological populations according to their diversity. The profiles are estimated on the basis of independent replications of a suitable sampling design. Asymptotically conservative joint confidence bands are constructed by the Richmond method, while equivalence hypotheses of couples of profiles are assessed against dominance or crossing alternatives by a multiple comparison test. The proposed procedures are applied for obtaining a partial diversity ordering for the avian populations settled in some selected parks in the north of Italy. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
304.
A functional depth measures the “centrality” of a functional datum (a function observed over a continuum, for example, a curve, an image) with respect to a given functional dataset. This paper proposes a way to detect outliers in functional time series based on functional depth. Ideally, the depth of a functional outlier should be very low but, when is it low enough to correspond to an outlier? This paper aims to address this question. It uses bootstrap techniques, which take into account the dependence between functional data, to solve this discriminant problem. Several Monte Carlo experiments were designed to explore the performance of the proposed procedure and compare it with some existing methods in the statistical literature related to independent functional data. The proposed methodology was finally used to detect outliers in temperature data and NOx emission data. Results conclude that dependence of data must be taken into account to detect outliers in functional time series. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
305.
We introduce an empirical method of estimating the number of species in a community based on a random sample. The numbers of sampled individuals of different species are modeled as a multinomial random vector, with cell probabilities estimated by the relative abundances of species in the sample and, for hypothetical species missing from the sample, by linear extrapolation from the abundance of the rarest observed species. Inference is then based on likelihoods derived from the multinomial distribution, conditioning on a range of possible values of the true richness in the community. The method is shown to work well in simulations based on a variety of real data sets. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
306.
There is an increased interest in merging observations from local networks into larger national and international databases. However, the observations from different networks have typically been made using different equipment and applying different post‐processing of the values. These heterogeneities in recorded values between networks can lead to inconsistencies between different networks, and to discontinuities at the borders between regions if the observations are used as a source for interpolated maps of the process. Such discontinuities are undesirable, and could create difficulties in interpreting the maps by decision makers. In this paper, we present two variants of a method that can be used to identify and quantify differences between networks. The first variant deals with networks sharing the same region (usually multiple networks within a country) while the second variant deals with networks in neighbouring regions (usually networks in different countries). The estimated differences can be used to estimate individual biases for each network, which can be subtracted as a harmonization procedure. The method was applied to European gamma dose rate (GDR) measurements from May 2008 from the European Radiological Data Exchange Platform (EURDEP) database. Data from the Slovenian GDR network are used for an application of the first variant of the method whereas the complete dataset is used to illustrate the second variant. The results indicate that these two variants are able to identify and quantify biases reliably, and the interpolated maps after subtraction of the estimated biases appear more reliable than maps created on the basis of the recorded data. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
307.
308.
309.
Some recent research on the properties of the probability density function for the concentration of a scalar dispersing in turbulent flow is summarized. It is concluded that the beta distribution may be a simple model consistent with these properties. This proposal is verified theoretically, and some preliminary data comparisons are very promising. 相似文献
310.