A new Sesleria juncifolia association from south-eastern Italy and its position in the amphi-Adriatic biogeographical context

The Sesleria juncifolia calcareous grasslands in the Apulia region (southern Italy) were studied on the basis of 24 phytosociological relevés. According to UPGMA cluster analysis division and NMDS ordination the relevés were classified into four major groups which gave rise to three sub-associations (Gargano) and a geographically impoverished variant (Alta Murgia). The new association Stipo austroitalicae-Seslerietum juncifoliae ass. nova was proposed. Due to the relict and scattered distribution of Sesleria juncifolia in Apulia region, the variances in species composition amongst the different subassociationsare mainly influenced by local factors. The community Stipo-Seslerietum should be included in the south-eastern Italian alliance Hippocrepido-Stipion austroitalicae while at the rank of order it exhibits intermediate coenological features between the Central- South Apennine endemic suborder Festuco-Seslerienalia nitidae and the North-West Balkan order Scorzonero-Chrysopogonetalia

CCA-2803 Essay Milan Randi} – Life and Work

Professor Milan Randi} is an important person in the history of Croatian chemistry. 1 It was he that first did research in quantum chemistry in Croatia and, thus, started theoretical chemistry research in our country. He founded the Theoretical Chemistry Group at the Rugjer Bo{kovi} Institute in Zagreb. Randi} was so persuasive a proselytizer that he attracted to the Theoretical Chemistry Group a number of bright and hard working graduate students who, along with their own students, are currently the most productive scientists in Croatia. Randi} is also widely recognized as one of the world leaders in the contemporary mathematical chemistry. Randi} recently summarized his research philosophy in the following words: 2 »There are no doubts that experiments are central to chemistry, as has been recently emphasized by Roald Hoffmann (Amer. Scientist 81 (1993) 15–17). One may continue then and argue that while central to chemistry are experiments, central to an experiment is theory, modeling. However, I hasten to add that while most experiments yield data that may eventually become of interest to theory, not every theory and every model necessarily stimulate experiments, or are of interest to an experimental chemist. This is true even when theory is sound and the model of a molecule is generally accepted. On the other hand, experiments without theory appear, as Lord Rutherford once reflected, like stamp collecting!«

QSPR Study of Polarographic Half-wave Reduction Potentials of Benzenoid Hydrocarbons*

Correlation between the polarographic half-wave reduction potentials and the set of molecular descriptors of lower benzenoid hydrocarbons was made by the CROMRsel modeling procedure. The following descriptors were used in the modeling procedure: electron affinities, Hückel p-electron energies, p-electron energies of the lowest unoccupied molecular orbitals, the number of Kekulé structures and the vertex-connectivity index. All models with one, two or three descriptors were considered. It was found that the p-electron energies of the lowest unoccupied molecular orbitals E(LUMO) were participating in all the best models. A single-descriptor model based on E(LUMO) was selected for testing. The statistical parameters obtained for the test set are comparable to those of the training set. The obtained results suggest that energies of the lowest unoccupied molecular orbitals are indeed very suitable descriptors for predicting the polarographic half-wave reduction potentials of benzenoid hydrocarbons