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871.
Summary. The sugar alcohol dulcitol is a strong feeding stimulant for larvae of the small ermine moth Yponomeuta cagnagellus. In this paper we tested the hypothesis that dulcitol also acts as an oviposition stimulant for this species. We found that the sugar-alcohol dulcitol was present on the surface of the host Euonymus europaeus. We also showed that (as yet unidentified compounds) can be systemically transferred (i.e. by uptake and transport via the vascular system) from E. europaeus, to the non-host Crataegus monogyna and stimulate oviposition. However, no evidence was found that this stimulatory activity was due to dulcitol. Systemic enrichment of C. monogyna with dulcitol did not induce oviposition on this plant. Neither was the application of pure dulcitol on artificial twigs effective. In addition it was shown that when dulcitol was removed from host plant extracts, oviposition stimulatory activity was retained in the fraction without dulcitol. Synergism between dulcitol and other stimulants could not be demonstrated, however, high concentrations of dulcitol in combination with the main stimulant(s) showed a trend towards enhanced oviposition. It is concluded that the sugar alcohol dulcitol can only play a limited role in adult host acceptance behaviour. The hypothesis that a host shift in the genus Yponomeuta from Celastraceae to Rosaceae might have been facilitated by the presence of small amounts of dulcitol in Rosaceae therefore needs to be restricted to larval feeding behaviour. Received 20 August 1999; accepted 6 December 1999  相似文献   
872.
Engineering projects involving hydrogeology are faced with uncertainties because the earth is heterogeneous, and typical data sets are fragmented and disparate. In theory, predictions provided by computer simulations using calibrated models constrained by geological boundaries provide answers to support management decisions, and geostatistical methods quantify safety margins. In practice, current methods are limited by the data types and models that can be included, computational demands, or simplifying assumptions. Data Fusion Modeling (DFM) removes many of the limitations and is capable of providing data integration and model calibration with quantified uncertainty for a variety of hydrological, geological, and geophysical data types and models. The benefits of DFM for waste management, water supply, and geotechnical applications are savings in time and cost through the ability to produce visual models that fill in missing data and predictive numerical models to aid management optimization. DFM has the ability to update field-scale models in real time using PC or workstation systems and is ideally suited for parallel processing implementation. DFM is a spatial state estimation and system identification methodology that uses three sources of information: measured data, physical laws, and statistical models for uncertainty in spatial heterogeneities. What is new in DFM is the solution of the causality problem in the data assimilation Kalman filter methods to achieve computational practicality. The Kalman filter is generalized by introducing information filter methods due to Bierman coupled with a Markov random field representation for spatial variation. A Bayesian penalty function is implemented with Gauss–Newton methods. This leads to a computational problem similar to numerical simulation of the partial differential equations (PDEs) of groundwater. In fact, extensions of PDE solver ideas to break down computations over space form the computational heart of DFM. State estimates and uncertainties can be computed for heterogeneous hydraulic conductivity fields in multiple geological layers from the usually sparse hydraulic conductivity data and the often more plentiful head data. Further, a system identification theory has been derived based on statistical likelihood principles. A maximum likelihood theory is provided to estimate statistical parameters such as Markov model parameters that determine the geostatistical variogram. Field-scale application of DFM at the DOE Savannah River Site is presented and compared with manual calibration. DFM calibration runs converge in less than 1 h on a Pentium Pro PC for a 3D model with more than 15,000 nodes. Run time is approximately linear with the number of nodes. Furthermore, conditional simulation is used to quantify the statistical variability in model predictions such as contaminant breakthrough curves.  相似文献   
873.
874.
欧洲委员会已经编制了关于有效使用"环境协议"的指导准则.这些指导准则旨在提高此类协议的透明度和可信度--尤其通过公布这些协议、确定明确目标、和可靠监测.欧洲委员会与欧洲工业界之间的环境协议是有潜力的.当取得更多的经验时,欧共体各机构将需要商定各自在协议谈判与缔结方面的作用.欧共体也力求拓宽各成员国利用环境协议实施环境指令的选择.  相似文献   
875.
876.
877.
The aim of this study was to investigate reproductive strategies and their consequences in gray mouse lemurs (Microcebus murinus), small solitary nocturnal primates endemic to Madagascar. Previous reports of sexual dimorphism in favor of males and females, respectively, a high potential for sperm competition and pheromonal suppression of mating activity among captive males, led us to investigate mechanisms of intrasexual competition in a wild population. Based on 3 years of mark-recapture data, we demonstrate that sexual dimorphism in this species fluctuated annually as a result of independent changes in male and female body mass. Male body mass increased significantly prior to the short annual mating season. Because their testes increased by 100% in the same period and because their canines are not larger than those of females, we suggest that large male size may be advantageous in searching for estrous females and in enabling them to sustain periods of short-term torpor. In contrast to reports from captive colonies, we found no evidence for two morphologically distinct classes of males. Finally, we also show that most adult males are active throughout the cool dry season that precedes the mating season, whereas most adult females hibernate for several months. This is in contrast to other solitary hibernating mammals, where males typically emerge 1–2 weeks before females. Thus, this first extended field study of M.␣murinus clarified previous conflicting reports on sexual dimorphism and male reproductive strategies in this primitive primate by showing that their apparent deviation from predictions of sexual selection theory is brought about by specific environmental conditions which result in sex-specific life history tactics not previously described for mammals. A general conclusion is that sexual selection can operate more strongly on males without resulting in sexual dimorphism because of independent selection on the same traits in females. Received: 6 July 1997 / Accepted after revision: 28 March 1998  相似文献   
878.
879.
To assist transport modeling in assessments of the radiological impact of a geological repository for radioactive wastes, the mobility of various elements was studied in arable and wetland soils in the Forsmark region, Sweden. Pore water and total element contents were determined for five types of unconsolidated deposits (regolith), spanning a wide range of soil properties with respect to pH and organic matter content. Two soil depths were sampled to capture element mobility in regolith layers affected and unaffected by soil-forming processes. The solid/liquid partition coefficients (K d values) for most elements varied significantly among regolith types. For most elements, the observed variations in K d values could be explained by variations in soil properties. For many elements, mobility increased with decreasing soil pH. The results provide a significant addition of data on radionuclide retention in soils, taking account of soil properties and processes.  相似文献   
880.
There have been great transitions in the science of air pollution and science publishing since the journal began as the International Journal of Air Pollution in 1958. Atmospheric Environment witnessed the increased understanding of smog photochemistry in the late 1950s and the emerging fears of ozone depletion in the 1970s. The journal has grown, but not without the need to change and occasionally fragment only to reintegrate at a later date. At 9000 pages a year it represents an enormous editorial task that has had to be undertaken by more professional offices. This transition has been helped through the development of electronic tools, but the editorial offices strive to retain their personal relationship with authors and reviewers. An enhanced international perspective recognises the widening contributions made by scientists beyond Europe and North America.  相似文献   
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