Biomedical subjects

Mircea V Diudea

Publications and source records attributed to Mircea V Diudea.

4 recordsLinked to original sources

PubMed2005

Corannulene and corazulene tiling of nanostructures.

Tiling modification in nanostructure modeling can be achieved by map operations, as well as the well-known Stone-Wales bond rotation. In this respect, sequences of classical operations, or single generalized operations, were used to obtain corannulenic flowers and corannulene-like azulenic patterns. The first "corazulenic" tessellation is reported. The aromaticity of some cages tessellated by the above supra-faces is discussed in terms of several different criteria. The covering was given as a pi-electron partition within some Kekulé valence structures.The well-known geometric index of aromaticity HOMA (harmonic oscillator model of aromaticity) enabled the evaluation of local aromaticity of the discussed supra-faces and brought evidence for several dominant Kekulé valence structures. The most intriguing is the "Kekulé-Dewar" valence structure of the cage C(192) having a disjoint corazulenic tessellation.

Chemical Phenomena↗

PubMedDate not supplied

Periodic cages.

Various cages are constructed by using three types of caps: f-cap (derived from spherical fullerenes by deleting zones of various size), kf-cap (obtainable by cutting off the polar ring, of size k), and t-cap ("tubercule"-cap). Building ways are presented, some of them being possible isomerization routes in the real chemistry of fullerenes. Periodic cages with ((5,7)3) covering are modeled, and their constitutive typing enumeration is given. Spectral data revealed some electronic periodicity in fullerene clusters. Semiempirical and strain energy calculations complete their characterization.

Journal Article↗

PubMedDate not supplied

Nanoporous carbon allotropes by septupling map operations.

Spongy carbon nanostructures, also called schwarzites, have been synthesized. They consist of highly connected covalent networks, periodic in the three dimensions of Euclidean space. The intimate structure of schwarzites has a topology of triply periodic minimal surfaces. They can be tessellated by some geometric operations on maps, including the newly proposed septupling operations. Formulas for calculating the lattice parameters of iteratively transformed maps are presented. Examples are given for both finite/closed cages and infinite/open all-sp2 carbon structures. Strain energy calculations for structures, consisting of thousands of atoms, show that such carbon allotropes are very relaxed and approach to the non-strained graphite sheet.

Journal Article↗

PubMedDate not supplied

Retro-leapfrog and related retro map operations.

Operations on maps are well-known theoretical tools for transforming a given polyhedral tessellation. Several theoretical investigations of fullerenes, such as their pi-electronic structure and stability, need information on the original map which was transformed into a larger molecular structure. In this respect, retro-operations, particularly those of the most used leapfrog, chamfering, and capra operations, appear particularly useful in searching the associate graphs of fullerenes. A series of analyzed cages proved to be leapfrog transforms of smaller cages. This information was useful in understanding their closed pi-electronic structure and related properties including the local aromaticity. An index based on the optimized geometries enabled the evaluation of aromaticity of their various substructures. Pictorial images of the pi-electron distribution as the main Kekulé valence structures have been performed by the aid of the JSCHEM software package.

Carbon↗