The atom-bond connectivity (ABC) index is a degree-based molecular descriptor that found diverse chemical applications. Characterizing trees with minimum ABC-index remained an elusive open problem even after serious attempts and considered by some as one of the most intriguing problems in mathematical chemistry. In this paper, we describe exact structure extremal sufficiently many vertices show...

second language acquisition (sla) always happens when the learners live and have contact with the native speakers of a second language. although this study investigates learning english by ten native children of farsi, the authors try to simulate the second language acquisition environment. the research deals with the initial state and further development in the child second language learning o...

supported catalysts synthesized via the interaction of mg(oet)2 with ticl4 in the presence or absence of an internal stereoregulating donor (di-n-butyl phthalate), with different solvents (chlorobenzene, n-undecane, n-heptane) at different titanation temperatures have been studied by a set of physicochemical methods. data on the chemical composition, x-ray structure and pore structure of these ...

An important parameter in a secret sharing scheme is the number of minimal qualified sets. Given this number, the universal access structure is the richest possible structure, namely the one in which there are one or more participants in every possible Boolean combination of the minimal qualified sets. Every access structure is a substructure of the universal structure for the same number of mi...