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Importance of the presence of parents for the eggs development and fry mortality in fish of the genus \kur{Hemichromis}
MICHALIČKA, Petr
Through this experiment there was examined the effect of the presence of the parents in the development and mortality of fish spawn of the genus Hemichromis. Hemichromis guttatus was selected for this experiment as a model species. It was found that the parental care in the fish genus Hemichromis is most needed during the period when the offspring is in the stage of eggs. In this stage, the absence of parents showed higher level of mortality (greater number of attacked by mold eggs left without parental care). In other developmental stages of the offspring the parental care was not a great advantage, on the contrary, in some cases allowing parents to take care of the screed was a disadvantage due to cannibalism.
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A new construction of rotor of helium expansion turbine
Dupák, Jan ; Hanzelka, Pavel ; Michalička, Petr ; Tuček, L. ; Ustohal, V.
The aim of our work was to develop a rotor of the expansion turbine designed for a helium liquefier that would enable operation in different modes and achieving of the desired effectiveness at same time. For meeting theserequirements the rotor should enable precise operation of the turbine in the range of 140 000 to 350 000 rqm at minimum heat flow to the low-temperature part of the turbine. Considering the low thermal conductivity and a high strength, the low-temperature part was made of VT3-1 titanium alloy. This contribution is focused mainly on problems of creation of mechanically strong and thermally resistant joint of this part of the rotor with the part working at room temperature.
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On the redistribution of aluminium and carbon in the weld joints of steels in the temperature range 500-1100oC (1,15 wt.% Al)
Stránský, K. ; Million, Bořivoj ; Foret, R. ; Michalička, Petr ; Rek, A.
Measurements of Al, Cr, Fe, Ni, C redistribution in welded joints of unalloyed 12050+1,15Al steel and high alloyed Cr-Ni steel in temperature range 500-1100oC were realised by means of analytical complex JEOL JXA 8600/KEVEX. The C, Al, Cr, Fe, Ni diffusion coefficients were established and the relation among diffusion coefficients were discused.
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Simultaneous diffusion of aluminium, carbon, chromium, iron and nickel in steel weldments at temperature interval 500 to 1100°C
Stránský, K. ; Million, Bořivoj ; Foret, R. ; Rek, A. ; Michalička, Petr
In this paper results of measurements of simultaneous diffusion of aluminium, carbon, chromium, iron and nickel in welded joints of unalloyed 12050+Al steel and high alloy austenitic chromium-nickel steel are presented.
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