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191.
192.
The feasibility of using two fertilizers (urea plus superphosphate) in tap water as a medium for the mass culture of green algae (Scenedesmus and Ankistrodesmus) in outdoor plastic-enclosed minipond systems was investigated. Experiments in which the basic fertilizer-tap water medium was enriched with micro- and/or macronutrients revealed no nutrient deficiency symptoms in the algal biomass produced. Biomass production was found to be quantitatively related to the concentration of fertilizer added and maximal production (> 15 g/m(2) day) was achieved following the addition of 30 mg N/L (1.89 g N/m(2) day) and 4.5 mg P/L (0.28 g P/m(2)/day). 相似文献
193.
The objectives and rationale of the First International Symposium on Southern Hemisphere Limnology are outlined. The geography and climate of the Northern and Southern Hemispheres are compared. Greater areas of the land masses in the Southern Hemisphere fall under oceanic influence than in the Northern Hemisphere at equivalent latitude. Although many Southern Hemisphere land masses are arid it is concluded that limnological differences between the Hemispheres are of degree rather than of kind and that limnological principles developed in the Northern Hemisphere are, in general, globally applicable. However, Southern Hemisphere water resources management problems have centred upon arid-land water supply problems, probably to the detriment of pure limnological research. 相似文献
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195.
van Hoek AH; van Alen TA; Sprakel VS; Hackstein JH; Vogels GD 《Molecular biology and evolution》1998,15(9):1195-1206
The 18S and 5.8S rDNA genes and the internal transcribed spacers ITS-1 and
ITS-2 of ciliates living in the hindgut of frogs, millipedes, and
cockroaches were analyzed in order to study the evolution of intestinal
protists. All ciliates studied here belong to the genus Nycrotherus.
Phylogenetic analysis revealed that these ciliates from a monophyletic
group that includes the distantly related anaerobic free-living
heterotrichous ciliates Metopus palaeformis and Metopus contortus. The
intestinal ciliates from the different vertebrate and invertebrate hosts
are clearly divergent at the level of their rDNA repeats. This argues for
the antiquity of the associations and a predominantly vertical
transmission. This mode of transmission seems to be controlled primarily by
the behavior of the host. The different degrees of divergence between
ciliates living in different strains of one and the same cockroach species
most likely reflect the different geographical origins of the hosts. In
addition, host switches must have occurred during the evolution of
cockroaches, since identical ciliates were found only in distantly related
hosts. These phenomena prevent the reconstruction of potential cospeciation
events.
相似文献
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198.
白踝按蚊种团是由很多形态近似的蚊种组成,其中巴拉巴按蚊和白踝按蚊均为东南亚一带的重要传疟媒介。我国过去资料均记载为白踝按蚊,但未从形态上详细鉴定。为了确定该种的分类地位,1963年作者等在海南岛万宁县兴隆附近山林区采集“白踝按蚊”全套标本10批共150多套,1971年后从云南省采集少数标本进行形态鉴定,发现其与Colless(1956,1957)所描述的白踝按蚊Anopheles leucosphyrus leucosphyrus Donitz(1901)有很明显的差别,而与巴拉巴按蚊A.balabacensis balabacensis Balsas(1936)除某些特征略有差异外,余均完全一致。按Colless的分类法,过去我国记载的“白踝按蚊”,应鉴定为巴拉巴按蚊A.balabacensis balabacensis Baisas。 相似文献
199.
R. H. Walmsley 《Biophysical journal》1969,9(3):421-431
The general theory of mapping functions for random genetic recombination is derived without reference to physical models. The results are of particular relevance to asymmetric recombination (preferential recombination of the alleles of either parent) and include the effects of lethal lesions. It is noted that the assumption of randomness determines the mapping functions uniquely so that they are independent of the specifications of any stochastic physical model of recombination. In particular, the functions derived from physical models by Haldane, Wu, Wood and Verhoef and de Haan are special cases of those derived here. A general principle for the testing of genetic linkage is formulated which is valid for both symmetric and asymmetric recombination. 相似文献
200.