Czechoslovak Academy of Sciences

About: Czechoslovak Academy of Sciences is a based out in . It is known for research contribution in the topics: Catalysis & Adsorption. The organization has 13227 authors who have published 17335 publications receiving 272882 citations.

Notes on the ultrastructure and sporoblast development in fish parasitizing myxosporidian of the genus Sphaeromyxa.

Abstract: The ultrastructure of trophic stage (plasmodium), spore and changes in fine structure during morphogenesis of the spore were studied by electron microscopy in two representatives of the genusSphaeromyxa Plasmodium has a highly differentiated structure; there is an outer layer of homogeneous plasm, the endoplasm consisting of a vacuolated mass in which “float” generative cells and sporoblasts in different degree of development Generative cells have well developed pseudopodia Sporoblasts arise from the union of two cells, out of which the inner one forms all cells of the spore, the outer one has only an enveloping function Polar capsule develops in a way identical with other myxosporidia; the wide filament, however, has a longitudinally folded structure and is located within the capsule in two loose loops The mitochondria of an early sporoblast are characterized by a high content of DNA The identity of polar capsule development with the nematocyst morphogenesis is too conspicuous to be taken for a mere convergence Studies on ultrastructure give no evidence for a protozoan character of myxosporidia; together with other findings, they are in favor of the nonprotozoan nature of this group of organisms

Possible food chain relationships between bacterioplankton, protozoans, and cladocerans in a reservoir

Abstract: Ingestion of fluorescent particles by natural protozoan assemblage was studied in the Řimov Reservoir (Southern Bohemia) from April to October, 1987. Attached and free-living bacterial abundance, proportion of active bacteria, density of suspended particles and biomass of cladocerans were also monitored. Heterotrophic nanoflagellates (HNF; 5–12.8 102ml−1) were the dominant bacterial micrograzers during the spring period and consumed 3 to 9% of the total bacteria per day. After the spring phytoplankton bloom maximum densities of suspended particles and attached bacteria (up to 28% of the total counts) were found. Development of cladocerans in May sharply decreased the proportion of attached bacteria and kept them below 5% of the total counts. All the studied components of plankton except Cladocera decreased during the clearwater phase. The most significant drop was observed in the numbers of protozoans, and they were negligible for bacterial elimination. Bacterial losses during that time apparently were due to cladoceran grazing. During the summer period, ciliates (15–142 ml−1) were mostly dominant micrograzers, and protozoan community grazing increased up to 21% of bacterial standing stock per day. The proportion of active bacteria was strongly correlated with protozoan grazing (r=0.83).

Dislocation theory of slip geometry and temperature dependence of flow stress in B.C.C. metals

Abstract: It is assumed that transformations of the splitting of a screw dislocation are continually repeated during its motion, and thus the screw dislocation crosses into different {110} and {112} planes [1]. On the basis of this mechanism a theory of the composite slip on {110} and {112} planes is established, and the dependence of the orientation of the slip plane on the orientation of the maximum resolved shear stress plane is calculated. The results are compared with the measurements of Taoka et al. [8] and Sestak and Zarubova [9]. Further it is shown that the same mechanism can account for the strong temperature dependence of the flow and yield stress. Mit der Annahme, das die Umwandlungen der Aufspaltung einer Schraubenversetzung sich kontinuierlich wahrend deren Bewegung wiederholen und auf diese Weise die Schraubenversetzung in verschiedene {110}- und {112}-Ebenen ubergeht [1], wird eine Theorie einer zusammengesetzten Gleitung auf den {110}- und {112}-Ebenen aufgestellt und die Abhangigkeit der Orientierung der Gleitebene von der Orientierung der Ebene mit maximaler Schubspannung berechnet. Die Ergebnisse werden mit den Messungen von Taoka et al. [8] und Sestak und Zarubova [9] verglichen. Weiter wird gezeigt, das der gleiche Mechanismus die starke Temperaturabhangigkeit der Fliesspannung bewirken kann.

Cooperative tapping: time control under different feedback conditions.

Abstract: The same isochronous tone sequence was presented simultaneously to two mutually isolated subjects. In half the trials, accentuation in this sequence was accomplished by doubling the duration of the first and then of every fourth tone; in the other half, by doubling the frequency of those tones. The subjects' task was to follow the rhythm of the resulting four-tone patterns by finger tapping to tone onsets. There were four auditory feedback (FB) conditions: (1) no FB; (2) FB from the subject's own motor responses; (3) "alien" FB from the motor responses of the other pair member who, in turn, was listening to FB from his/her own tapping; (4) mutually "crossed" FB, where each pair member listened to FB from the tapping of the other. Tap onsets regularly preceded stimulus onsets. The observed order of the amount of this anticipation (from least to greatest) was: (1) own FB, (2) no FB, (3) alien FB, and (4) crossed FB. No mutual dynamic influence between simultaneously performing subjects was detected. Anticipation was more pronounced for sequences that were accentuated by frequency rather than by duration changes. The type of accent also influenced timing of intertap intervals in the rhythmic patterns. For the frequency accent, regular timing was produced, whereas for the durational accent, shortening of the second and lengthening of the fourth (the last) intertap interval were observed. The presence and source of feedback as well as the character of accentuation are therefore relevant factors in the timing of auditorally controlled rhythmic motor behavior.