On the interpretation of some planktonology equations

Summary The concept of the mean value of a function is used to interpret some population-dynamics equations. The well-known formula for the per capita growth rate r gives a precise mean value for any (not only exponentially growing) populations. This result is used to derive the birth and death rate equations of Paloheimo (1974) with minimal initial limitations.Abbreviations t time - N number of animals - E number of eggs - r specific (i.e. per capita) population growth rate - b specific birth rate - d specific death rate - D duration of embryonic development     

Testing of the method for water microleakage detection from OH hydroxyl spectral lines at the L-2M stellarator

Results are presented from L-2M stellarator experiments on testing a possible method for detection of water microleakages in the cooling system of the first wall and vacuum chamber of ITER. The method consists in the spectroscopic detection of spectral lines of the OH hydroxyl, which forms via the dissociation of water molecules in plasma. Emission in the spectral band of 305–310 nm can be detected even at water leakage rates less than 10^?4 Pa m³/s. Chemical reactions between water and boron compounds on the vacuum chamber wall delay the detection of leakages up to ～2000 s. A similar phenomenon can be expected when a leakage will occur in ITER, where the materials suggested for the first wall (Be, Li) can also chemically react with water.     

Plant virus infection development as affected by heavy metal stress

The work was focused on the investigation of possible dependencies between the development of viral infection in plants and the presence of high heavy metal concentrations in soil. Field experiments have been conducted in order to study the development of systemic tobacco mosaic virus (TMV) infection in Lycopersicon esculentum L. cv. Miliana plants under effect of separate salts of heavy metals Cu, Zn and Pb deposited in soil. As it is shown, simultaneous effect of viral infection and heavy metals in tenfold maximum permissible concentration leads to decrease of total chlorophyll content in experiment plants mainly due to the degradation of chlorophyll a. The reduction of chlorophyll concentration under the combined influence of both stress factors was more serious comparing to the separate effect of every single factor. Plants' treatment with toxic concentrations of lead and zinc leaded to slight delay in the development of systemic TMV infection together with more than twofold increase of virus content in plants that may be an evidence of synergism between these heavy metal's and virus' effects. Contrary, copper although decreased total chlorophyll content but showed protective properties and significantly reduced amount of virus in plants.     

Seasonal Variations in the Structure of an Anoxygenic Phototrophic Bacterial Community from the Meromictic Lake Trekhtsvetnoe (Kandalaksha Bay,White Sea)

Microbiology - The community of anoxygenic phototrophic bacteria (APB) from the water column of the meromictic Lake Trekhtsvetnoe (Kandalaksha Bay, White Sea, Russia) was studied in March 2012 and...     

Classification of the forebrain striatum neurons in birds

Polymorphism of neurons in the basic fields of the forebrain striatum of birds was described using specially developed classification of neurons in Nissl preparations. Birds with different degrees of development of elementary rational activity were studied: Corvus monedula, Columba livia, Coturnix coturnix, and Melopsittacus undulatus. According to the proposed method, the neurons were classified in 3 basic types and 2 additional, 6 subtypes and 26 classes. It was found that in the higher brain regions of Corvus monedula, birds with advanced rational activity, there are a greater variety and number of complex associative stellate cells than in birds with poorly developed rational activity (Columba livia and Coturnix coturnix).     

Comparative embryology of nematodes and the law of embryo similarity

Two types of embryonic development can be distinguished within nematodes, with a variable (Enoplia) or invariant (remaining species) cleavage. In the case of invariant cleavage two main variants of cell lineage are presented in nematodes, with the posterior (Rhabditea) or anterior (Dorylaimida) localization of endoderm material at the two-cell stage. This classification is in a good agreement with some modern nematode taxonomy and it is supported by molecular phylogeny studies. The variable cleavage is plesiomorphic. Traditional concept of "mosaic" cleavage is not applicable for nematodes as inductive interactions and a regulation of experimental interventions are usual attributes of any mode of nematode development. The representatives of order Rhabditida have almost identical cell lineage, but at the same time they have strong interspecific differences in mechanisms of ooplasmic segregation any early inductive interactions. The diversity of geometric patterns in the early cleavage, often at the level of individual random variations, is a usual characteristic of nematodes including species with the invariant cleavage. Thus, the early stages of nematode development are evolutionary very flexible, but at the course of embryonic development similarity of different species is progressively increased up to the uniform morphogenetic stages. The dynamics of variation in nematode development contradict to the von Baer's law but are in an agreement with the modern "hourglass model" (Doboul, 1994; Raff, 1986).