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31.
Laperdina T. G. Melnikova M. V. Koval A. T. Sidorov Y. F. Nagorny V. A. Ostapchuk V. I. 《环境科学学报(英文版)》2000,(Z1)
IntroductionSiberiaandtheFarEastaretheoldestandtherichestgold miningareasofRussia .Intensivegold miningherestartedinthebeginningofthe 19thcentury(Vyazelshchikov ,1963) .Forthemostpartgold bearingoresandsandswereprocessedwiththeuseofamalgamationmethodforgolde… 相似文献
32.
The honeybee compound eye is equipped with ultraviolet, blue, and green receptors, which form the physiological basis of a
trichromatic color vision system. We studied the distribution of the spectral receptors by localizing the three mRNAs encoding
the opsins of the ultraviolet-, blue- and green-absorbing visual pigments. The expression patterns of the three opsin mRNAs
demonstrated that three distinct types ommatidia exist, refuting the common assumption that the ommatidia composing the bee
compound eye contain identical sets of spectral receptors. We found that type I ommatidia contain one ultraviolet and one
blue receptor, type II ommatidia contain two ultraviolet receptors, and type III ommatidia have two blue receptors. All the
three ommatidial types contain six green receptors. The ommatidia appear to be distributed rather randomly over the retina.
The ratio of type I, II, and III ommatidia was about 44:46:10. Type III ommatidia appeared to be slightly more frequent (18%)
in the anterior part of the ventral region of the eye. Retinal heterogeneity and ommatidial randomness, first clearly demonstrated
in butterflies, seems to be a common design principle of the eyes of insects. 相似文献
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The Mormon cricket, Anabrus simplex, is one of just a few species of katydids (or bushcrickets, Orthoptera: Tettigoniidae) that, like migratory locusts, appear
to have solitary and migratory morphs. Using radio telemetry we studied movements of individuals of two morphs of this flightless
species. Individuals within each migratory band had similar rates of movements along similar directional headings whereas
solitary individuals moved little and showed little evidence of directionality in movement. Our results also add to other
recent radio-telemetry studies showing that flightless insects of 1–2 g in mass can be tracked successfully using these methods.
Received: 28 February 2000 / Accepted in revised form: 19 June 2000 相似文献
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In this paper we deal with the problem of identifying environmental principles for the design and operation of supply chains. The operations that are included in supply chains are briefly described along with the approaches that are applied in order to improve their environmental performance. A background of environmental principles for achieving eco-efficiency and building of environmentally friendly organizational systems is presented and emphasis is put on the application of such principles “from cradle to grave”. Then, environmental principles applicable to particular objects of logistics networks planning are identified and commented upon. In addition, selective case studies from the literature, which show the applicability of the formulated principles and their relevance to practice, are discussed. The paper concludes with some remarks regarding the benefits for companies and societies, in general, that occur as a result of the application of the formulated principles. 相似文献
40.
In Hydra vulgaris at the level of dissociated single cells endodermal cells adhere to each other more readily than to ectodermal cells at the
initial adhesion. The time required for adhesion to occur between two adjacent cells is shorter for both endodermal and ectodermal
homotypic cell adhesions once the initial adhesion of the first pair of cells has been established. It is confirmed that contact
of an aggregated pair with additional homotypic cells facilitates the occurrence of homotypic adhesions; heterotypic adhesions
are discouraged. This suggests that adhesion of homotypic cells contributes to an increased readiness for subsequent homotypic
cells to adhere.
Received: 25 August 1999 / Accepted in revised form: 11 January 2000 相似文献