The Kekule structure count K of fluoranthene congeners is studied. It is shown that for such polycyclic conjugated π-electron systems, either K = 0 or K ≥ 3. Moreover, for every t ≥ 3, there are infinitely many fluoranthene con- geners having exactly t Kekule structures. Three classes of Kekulean fluoran- thenes are distinguished: i) Φ0 - fluoranthene congeners in which neither the male nor the female benzenoid fragment has Kekule structures, ii) Φm - fluo- ranthene congeners in which the male benzenoid fragment has Kekule structures, but the female does not, and iii) Φfm - fluoranthene congeners in which both the male and female benzenoid fragments have Kekule structures. Necessary and sufficient conditions are established for each class, Φ = Φ0, Φm, Φfm, such that for a given positive integer t, there exist fluoranthene congeners in Φ with the property K = t.

The aim of this study was to evaluate microbiological changes of traditionally produced horse meat sausages depending on maturing phases and season, to determine lactic acid bacteria and to research their inhibitory potential towards L. monocytogenes. Production season influenced significantly on total viable count, lactic acid bacteria, coagulase-negative cocci, enterococci and yeasts in final product (p<0.05). Lactic acid bacteria represented the most numerous microbial population, and significant number of yeasts and coagulase-negative cocci was also determined. Lactobacillus plantarum was determined as a dominant species in lactic acid bacteria population (56 %), while Weisella confusa (26 %), Lactobacillus fermentum (6 %), Lactobacillus pentosus (6 %), Lactococcus lactis subsp. lactis (2 %), Lactobacillus delbrueckii subsp. delbrueckii (2 %) and Weisella viridescens (2 %) were also isolated. Lactobacillus strains showed in laboratory conditions the strongest inhibitory effect towards L. monocytogenes. The results of this research may contribute to better understanding of specific issues of horse meat fermented sausages production compared to sausages produced from other sorts of meat and they can be used for sausage production standardization.

This paper is concerned with numerical study of fluid flow through a pair of corrugated platest. The aim was to observe and understand the behavior of the flow and vortex formation through channels where the fluid is subjected to a periodic increase and decrease in cross-section area. The plates modeled for the study had sinusoidal profiles. A pair of plates with 180 o phase shift was simulated in two-dimensional spaces. The Reynolds number was a function of the average plate spacing (Havg) and the laminar flow velocity and it was in the range between 200 and 1000.