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481.
To determine the precursors and the fate of 26-hydroxyecdysone in eggs, the fate of labeled putative ecdysteroid precursors
was examined in the tobacco hornworm,Manduca sexta. Following injection of [14C]cholesterol, 22,25[14C]dideoxyecdysome or [3H]ecdysone into female pupae (day 16), only [14C]cholesterol was incorporated and metabolized. It was converted to labeled nonecdysteroid and ecdysteroid conjugates, of
which the latter in ovaries and 48- to 64-hr-old eggs is mainly 26-hydroxyecdysone 26-phosphate (>85% in ovaries). Quantitation
of the ecdysteroid conjugate by reversed-phase high performance liquid chromatography (RP-HPLC) showed that the levels of
26-hydroxyecdysone 26-phosphate were 31 μg/g of ovaries from 4-day-old females and 25 μg/g and 17 μg/g of 48- to 64-hr-old
and 72- to 88-hr-old eggs, respectively. The RP-HPLC of the conjugate fraction of 48- to 64-hr-old eggs showed an additional
peak of radioactive material eluting about three min before the 26-hydroxyecdysone 26-phosphate. The quantity of this material
increased in the 72-to 88-hr-old eggs, though it was not detected in the analyses of the conjugate fraction from ovaries.
Additional peaks of radioactive material eluting before the 26-hydroxyecdysone 26-phosphate peak were observed in the chromatogram
of the conjugates of 72- to 88-hr-old eggs. These radioactive materials need to be identified to determine the ultimate fate
of ecdysteroids in the developing embryos of the tobacco hornworm. No radioactive free ecdysteroids were detected in either
egg age group. 相似文献
482.
Sustainable development of cities requires robust water supply systems, yet many cities need to resort to ad hoc measures when faced with a drought. This article aims to explore how cities can do better in reducing the risk of water shortage due to drought. To that end, a classification of drought measures in urban water supply systems is proposed, and then applied to 10 cities that recently faced a drought. We find that these cities used a relatively limited number and variety of measures. The classification can help cities evaluate different types of measures for reducing long-term water stress and limit the impact of extreme droughts. 相似文献
483.
Procedural modelling deals with (semi‐)automatic content generation by means of a program or procedure. Among other advantages, its data compression and the potential to generate a large variety of detailed content with reduced human intervention, have made procedural modelling attractive for creating virtual environments increasingly used in movies, games and simulations. We survey procedural methods that are useful to generate features of virtual worlds, including terrains, vegetation, rivers, roads, buildings and entire cities. In this survey, we focus particularly on the degree of intuitive control and of interactivity offered by each procedural method, because these properties are instrumental for their typical users: designers and artists. We identify the most promising research results that have been recently achieved, but we also realize that there is far from widespread acceptance of procedural methods among non‐technical, creative professionals. We conclude by discussing some of the most important challenges of procedural modelling. 相似文献
484.
Alicyclic photoresists for CO2-based next-generation microlithography: A tribute to James E. McGrath
Addition polymerization of norbornene-based monomers has been pursued toward the fabrication of photoresists for next-generation microlithography, using condensed carbon dioxide as the developing solvent. Addition polymers containing a norbornyl backbone, for dry plasma etch resistance and high thermal stability, were synthesized to include fluorinated moieties and chemical amplification switching groups. These materials have been characterized and their lithographic properties evaluated. Solubility differences between exposed and non-exposed resist have been observed in these novel systems, which should provide the necessary contrast for high-resolution imaging. Lithographic imaging produced dense lines as small as 3 μm. 相似文献
485.
486.
In this article, we concentrate in conceptual relations as a source of information for Word Sense Disambiguation (WSD) systems. We start with a review the most relevant research in the field, then we implement our own algorithm. As a starting point we have chosen the conceptual density algorithm of Agirre and Rigau. We generalize the original algorithm, parameterizing many aspects. This new algorithm obtains a relative improvement of 24% in terms of precision and recall. We also offer comparative evaluation of our system with respect to the participants in the SENSEVAL-2 disambiguation competition.We conclude that conceptual relations provide a source of information that is insufficient by itself to achieve good disambiguation results, but can, however, be a very accurate heuristic in a combined system. 相似文献
487.
Sana Baccar Mohsen Rouached Ruben Verborgh Mohamed Abid 《Service Oriented Computing and Applications》2018,12(3-4):371-389
Over the last decade, Web services composition has become a thriving area of research and development endeavors for application integration and interoperability. Although Web services composition has been heavily investigated, several issues still need to be addressed. In this paper, we mainly discuss two major bottlenecks in the current process of modeling compositions. The first bottleneck is related to the level of expertise required to achieve a composition process. Typical procedural style of modeling, inspired by workflow/business process paradigm, do not provide the required abstractions. Therefore, they fail to support dynamic and self-managed compositions able to adapt to unpredictable changes. The second bottleneck in current service compositions concerns their life cycle and their management, also called their governance. In this context, we propose a declarative proof-based approach to Web service composition. Based on the three stages of pre-composition, abstraction, and composition, our solution provides an easy way to specify functional and non-functional requirements of composite services in a precise and declarative manner. It guides the user through the composition process while allowing detection and recovery of violations at both design and run-time using proofs and planning. Experiment results clearly show the added value of the proof-based solution as a viable strategy to improve the composition process. 相似文献
488.
C. S. Brevett P. C. Cagle W. G. Klemperer D. M. Millar G. C. Ruben 《Journal of Inorganic and Organometallic Polymers and Materials》1991,1(3):335-342
Sol-gel polymerization of [Si8O12](OCH3)8 in an inert solvent under neutral conditions has been shown to yield very high-surface area silica xerogels [P. C. Cagleet al., Mater. Res. Soc. Symp. Proc. 180, 29 (1990)]. Two recent results relevant to this process are described here. First, a practical synthetic route to [Si8O12](OCH3)8 is described that allows multigram quantities to be conveniently prepared. Second, TEM studies are reported that confirm retention of the [Si8O12] cubic core structure in high-surface area, [Si8O12](OCH3)8 ? derived xerogels. 相似文献
489.
Grids offer a dramatic increase in the number of available processing and storing resources that can be delivered to applications. However, efficient job submission and management continue being far from accessible to ordinary scientists and engineers due to their dynamic and complex nature. This paper describes a new Globus based framework that allows an easier and more efficient execution of jobs in a ‘submit and forget’ fashion. The framework automatically performs the steps involved in job submission and also watches over its efficient execution. In order to obtain a reasonable degree of performance, job execution is adapted to dynamic resource conditions and application demands. Adaptation is achieved by supporting automatic application migration following performance degradation, ‘better’ resource discovery, requirement change, owner decision or remote resource failure. The framework is currently functional on any Grid testbed based on Globus because it does not require new system software to be installed in the resources. The paper also includes practical experiences of the behavior of our framework on the TRGP and UCM‐CAB testbeds. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
490.
Engineering On‐Surface Spin Crossover: Spin‐State Switching in a Self‐Assembled Film of Vacuum‐Sublimable Functional Molecule 下载免费PDF全文
Kuppusamy Senthil Kumar Michał Studniarek Benoît Heinrich Jacek Arabski Guy Schmerber Martin Bowen Samy Boukari Eric Beaurepaire Jan Dreiser Mario Ruben 《Advanced materials (Deerfield Beach, Fla.)》2018,30(11)
The realization of spin‐crossover (SCO)‐based applications requires study of the spin‐state switching characteristics of SCO complex molecules within nanostructured environments, especially on surfaces. Except for a very few cases, the SCO of a surface‐bound thin molecular film is either quenched or heavily altered due to: (i) molecule–surface interactions and (ii) differing intermolecular interactions in films relative to the bulk. By fabricating SCO complexes on a weakly interacting surface, the interfacial quenching problem is tackled. However, engineering intermolecular interactions in thin SCO active films is rather difficult. Here, a molecular self‐assembly strategy is proposed to fabricate thin spin‐switchable surface‐bound films with programmable intermolecular interactions. Molecular engineering of the parent complex system [Fe(H2B(pz)2)2(bpy)] (pz = pyrazole, bpy = 2,2′‐bipyridine) with a dodecyl (C12) alkyl chain yields a classical amphiphile‐like functional and vacuum‐sublimable charge‐neutral FeII complex, [Fe(H2B(pz)2)2(C12‐bpy)] (C12‐bpy = dodecyl[2,2′‐bipyridine]‐5‐carboxylate). Both the bulk powder and 10 nm thin films sublimed onto either quartz glass or SiOx surfaces of the complex show comparable spin‐state switching characteristics mediated by similar lamellar bilayer like self‐assembly/molecular interactions. This unprecedented observation augurs well for the development of SCO‐based applications, especially in molecular spintronics. 相似文献