Observations of photometric and spectroscopic data for open clusters and associations have been intensive during the last few years. Incentives are many:
- each cluster is an object for which the state of evolution and other
characteristics can be studied much better than for individual stars
- the systems of open clusters and associations in our own and other galaxies give information about the recent evolution of the galaxies themselves
- the clusters and associations are sensors of the conditions in interstellar space
Collections of observed data have been made by Alter, Ruprecht, Balazs, Vanysek and White in the comprehehsive Prague-Budapest card catalogues. My own efforts in this direction have resulted in computer readable catalogue of open cluster data, of which the 5th edition appeared recently. In collaboration with K. Janes and C.
Tilley of Boston University, I have now entered weight classes. The purpose of these is to monitor the reliability of conclusions based on cluster data. It seems that physical systems of 10-1000 stars can be divided into three categories;
- associations and unbound open clusters
- bound open clusters in the disk
- old open clusters
Properties such as age, linear diameter and abundances are discussed for these categories on the basis of the data contained in the Lund catalogue. The galactic distribution of young clusters and associations shows the existence of complexes inside the thin disk. The system of old open clusters seems to back up the concept of a thick disk.
Parameters of the fast chlorophyll (Chl) fluorescence induction (the O-J-I-P curve) of plants of winter wheat grown in the field canopy were statistically tested for Gaussian distribution. Five different statistical methods showed that the obtained values did not obey the Gaussian distribution law. The presentation of the parameters with the help of the mean and standard deviation masks the information about statistical properties of the values. Thus, we recommend to present the parameters by means of median, quartiles, and minimum and maximum values rather than by means of the mean and standard deviation. and D. Lazár, J. Nauš.
Type material of the proteocephalidean cestodes Manaosia bracodemoca Woodland, 1935 and Paramonticellia itaipuensis Pavanelli et Rego, 1991 (both monotypic genera) as well as recently collected material of the latter species are redescribed. A close similarity between both species was observed: the shape of scoleces is identical, both possess a globular scolex with hidden suckers, a well-developed circular, horseshoe-shaped musculature surrounding suckers; the measurements of both taxa are also similar (scolex, suckers, young proglottides). Both cestodes possess a medullary ovary crossing the dorsal muscle layer and ending in the dorsal cortex, the testes are in the dorsal cortex and the cortical vitellarium is laterally situated. Both species parasitize the same fish host. Therefore Paramonticellia is considered a junior synonym of Manaosia and Paramonticellia itaipuensis becomes a junior synonym of Manaosia bracodemoca. An emended diagnosis of Manaosia, which is a monotypic genus, is provided.
The paper deals with a special way of the construction of the boundary conditions for the compressible gas flow. The solution of the Riemann problem is used at the boundary. It can be shown, that the unknown one-side initial condition for this problem can be partially replaced by the suitable complementary condition. Authors work with such complementary conditions (by the preference of pressure, velocity, total quantities,...) in order to match the physically relevant data. Algorithms were coded and used within the own developed code for the solution of the Euler, NS, and the RANS equations, using the finite volume method. Numerical example shows superior behavior of these boundary conitions in comparison with some other boundary conditions. and Obsahuje seznam literatury
In Phaseolus and Robinia leaves, direct light reaction (de-epoxidatíon of violaxanthín) was inhibited during 7-9 h as an aftereffect of y-radiation (167 mGy s'*). Complete suppression of the light reaction by the de-epoxidation was reached after 12-14 h. The suppression of xanthophyll de-epoxidation reflects the inhibitíon of photosynthetic electron transport chain and may be ušed for testing deleterious efifects on plants.