Synthesis and fungicidal activity of lipophylic N- and O-acyl derivatives of beta-hydroxy DL-alpha-amino acids

Synthesis of N- and O-acyl derivatives of DL-serine and threo-DL-phenylserine was accomplished by a regioselective acylation of the corresponding amino acid. The residues introduced into amino acid structure contain hydrophobic long chain or aromatic, namely lauroyl, myristoyl and phenylacetyl moieties. The fungicidal activity against six strains of fungi was studied. Several compounds were found to be effective against growth of fungi, and O-myristoyl-DL-serine 2 and N-phenylacetyl-threo-DL-phenylserine 8 completely inhibited the growth of the mycelium of the fungus Verticillium dahliae.     

Threshold policies control for predator-prey systems using a control Liapunov function approach

The stability of predator-prey models, in the context of exploitation of renewable resources, subject to threshold policies (TP) is studied in this paper using the idea of backstepping and control Liapunov functions (CLF) well known in control theory, as well as the concept of virtual equilibria. TPs are defined and analysed for different types of one and two species predator-prey models. The models studied are the single species Noy-Meir herbivore-vegetation model, in a grazing management context, as well as the Rosenzweig-MacArthur two species predator-prey model, in a fishery management context. TPs are shown to be versatile and useful in managing renewable resources, being simple to design and implement, and also yielding advantages in situations of overexploitation.