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排序方式: 共有975条查询结果,搜索用时 187 毫秒
71.
A thermodynamic perspective on food webs: quantifying entropy production within detrital-based ecosystems 总被引:1,自引:0,他引:1
Because ecosystems fit so nicely the framework of a "dissipative system", a better integration of thermodynamic and ecological perspectives could benefit the quantitative analysis of ecosystems. One obstacle is that traditional food web models are solely based upon the principles of mass and energy conservation, while the theory of non-equilibrium thermodynamics principally focuses on the concept of entropy. To properly cast classical food web models within a thermodynamic framework, one requires a proper quantification of the entropy production that accompanies resource processing of the food web. Here we present such a procedure, which emphasizes a rigorous definition of thermodynamic concepts (e.g. thermodynamic gradient, disequilibrium distance, entropy production, physical environment) and their correct translation into ecological terms. Our analysis provides a generic way to assess the thermodynamic operation of a food web: all information on resource processing is condensed into a single resource processing constant. By varying this constant, one can investigate the range of possible food web behavior within a given fixed physical environment. To illustrate the concepts and methods, we apply our analysis to a very simple example ecosystem: the detrital-based food web of marine sediments. We examine whether entropy production maximization has any ecological relevance in terms of food web functioning. 相似文献
72.
BACKGROUND AND AIMS: The European Chaerophyllum temulum and two North American Chaerophyllum species have a trans-Atlantic disjunct distribution. This work aimed to resolve requirements for dormancy break and germination of C. temulum seeds and to compare dormancy traits with those of the two North American congeners. METHODS: Phenology of germination and embryo growth was studied by regularly exhuming seeds sown in natural conditions. Temperature requirements for embryo growth, breaking of dormancy and germination were determined by incubating seeds under controlled laboratory conditions. Additionally the effect of GA(3) on germination was tested to determine the specific dormancy type. KEY RESULTS: In natural conditions, embryo growth starts in early winter. Seedlings emerge in late winter shortly after the embryos reached the critical ratio for embryo length to seed length (E : S) of approx. 0.95. Growth of the embryo only occurs during a prolonged incubation period at 5 degrees C. After stratification at 5 degrees C, which breaks physiological and morphological dormancy, seeds can germinate at a wide range of temperatures. GA(3) did not substitute for cold stratification in seeds placed at 23 degrees C. CONCLUSIONS: Chaerophyllum temulum has deep complex morphophysiological dormancy. This dormancy type differs considerably from that of the two North American congeners. 相似文献
73.
The aim of this article is to clarify the meaning of a naturalistic position within philosophy of biology, against the background of an alternative view, founded on the basic insights of transcendental philosophy. It is argued that the apparently minimal and neutral constraints naturalism imposes on philosophy of science turn out to involve a quite heavily constraining metaphysics, due to the naturalism's fundamental neglect of its own perspective. Because of its intrinsic sensitivity to perspectivity and historicity, transcendental philosophy can avoid this type of hidden metaphysics. 相似文献
74.
Filip Vandenbussche Dominique Van Der Straeten 《Journal of Plant Growth Regulation》2007,26(2):178-187
The plant hormone ethylene plays a pivotal role in steering various processes by regulating the biosynthesis, distribution,
or signal transduction of other hormones. Ethylene also mediates the effects of other hormones. Similarly, hormones control
the ethylene synthesis and signalling pathway. Eventually, integration of this network of signals leads to an appropriate
morphological or biochemical response. Consequently, this cross-talk results in the characteristic plasticity associated with
plant development. Here, the interplay of ethylene with other hormones is described for germination and seedling growth, stomatal
control, and tissue elongation. The mechanisms by which this occurs are discussed in more detail. 相似文献
75.
76.
Filip Vandenbussche Ana C Fierro Gertrud Wiedemann Ralf Reski Dominique Van Der Straeten 《BMC plant biology》2007,7(1):65
Background:
Gibberellins (GA) are plant hormones that can regulate germination, elongation growth, and sex determination. They ubiquitously occur in seed plants. The discovery of gibberellin receptors, together with advances in understanding the function of key components of GA signalling in Arabidopsis and rice, reveal a fairly short GA signal transduction route. The pathway essentially consists of GID1 gibberellin receptors that interact with F-box proteins, which in turn regulate degradation of downstream DELLA proteins, suppressors of GA-controlled responses. 相似文献77.
Le Cong Huyen Bao Phan Tran Crepin Nathalie Rolland Filip Van Dijck Patrick 《Plant molecular biology》2022,108(6):531-547
Plant Molecular Biology - Alternative translation initiation of the unique Arabidopsis trehalase gene allows for the production of two isoforms with different subcellular localization, providing... 相似文献
78.
N‐terminal guanidinylation of the cyclic 1,4‐ureido‐deltorphin analogues: the synthesis,receptor binding studies,and resistance to proteolytic digestion
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Krzysztof Bańkowski Olga M. Michalak Anna Leśniak Katarzyna E. Filip Piotr Cmoch Zbigniew Szewczuk Piotr Stefanowicz Jan Izdebski 《Journal of peptide science》2015,21(6):467-475
The synthesis of a series of N‐guanidinylated cyclic ureidopeptides, analogues of 1,4‐ureido‐deltorphin/dermorphine tetrapeptide is described. The δ‐ and μ‐opioid receptor affinity of new guanidinylated analogues and their non‐guanidinylated precursors was determined by the displacement radioligand binding experiments. Our results indicate that the guanidinylation of cyclic 1,4‐ureidodeltorphin peptide analogues does not exhibit a uniform influence on the opioid receptor binding properties, similarly as reported earlier for some linear peptides. All analogues were also tested for their in vitro resistance to proteolysis during incubation with large excess of chymotrypsin, pepsin, and papain by means of mass spectroscopy. Guanidinylated ureidopeptides 1G–4G showed mixed μ agonist/δ agonist properties and high enzymatic stability indicating their potential as therapeutic agents for treatment of pain. Copyright © 2015 European Peptide Society and John Wiley & Sons, Ltd. 相似文献
79.
Korabecny J Musilek K Zemek F Horova A Holas O Nepovimova E Opletalova V Hroudova J Fisar Z Jung YS Kuca K 《Bioorganic & medicinal chemistry letters》2011,21(21):6563-6566
Cholinesterase inhibitors are, so far, the only successful strategy for the symptomatic treatment of Alzheimer's disease. Tacrine (THA) is a potent acetylcholinesterase inhibitor that was used in the treatment of Alzheimer's disease for a long time. However, the clinical use of THA was hampered by its low therapeutic index, short half-life and liver toxicity. 7-Methoxytacrine (7-MEOTA) is equally pharmacological active compound with lower toxicity compared to THA. In this Letter, the synthesis, biological activity and molecular modelling of elimination by-product isolated during synthesis of 7-MEOTA based bis-alkylene linked compound is described. 相似文献
80.
Van Praet JT Smith V Haspeslagh M Degryse N Elewaut D De Keyser F 《Arthritis research & therapy》2011,13(1):R35