fullerene chemistry is nowadays a well-established field of both theoretical and experimental investigations‎. this study considers the symmetry of small fullerenes cage c24 and c28‎. ‎using pm3 program for c24 and c28 fullerenes, oh and td symmetry were confirmed, respectively‎. ‎ the mentioned algorithm to compute the automorphism group of these fullerenes with connectivity and geometry of th...

The purpose of this research is to provide a deeper understanding of the planar high- symmetry configuration instability. In the ideal case, the distortion corresponds to the movements of nuclei along normal modes that belong to non-totally symmetric irreps of the high symmertry (HS) point group of molecule. The analysis of the structural distortion from the HS nuclear arrangements of the JT ac...

For both ecologists and physiologists, foliar physioecology as a function of spatially and temporally variable environmental factors such as sunlight exposure within a tree crown is important for understanding whole tree physiology and for predicting ecosystem carbon balance and productivity. Hence, we studied concentrations of nitrogen (N), non-structural carbohydrates (NSC = soluble sugars + ...

The 2002 Biscuit Fire burned through more than 200,000 ha of mixed-conifer/evergreen hardwood forests in southwestern Oregon and northwestern California. The size of the fire and the diversity of conditions through which it burned provided an opportunity to analyze relationships between crown damage and vegetation type, recent fire history, geology, topography, and regional weather conditions o...

PURPOSE This in vitro study aimed to analyze and compare the reproducibility of zirconia and lithium disilicate crowns manufactured by digital workflow. MATERIALS AND METHODS A typodont model with a prepped upper first molar was set in a phantom head, and a digital impression was obtained with a video intraoral scanner (CEREC Omnicam; Sirona GmbH), from which a single crown was designed and m...

New crown ether Schiff base derivatives were prepared by the condensation of 4'-formylbenzo-15-crown-5 or 4'-formyl-5'-hydroxybenzo-15-crown-5 with 1,2-bis(2-aminophenoxy)ethane. The structures of these new compounds were confirmed on the basis of elemental analysis, IR, (1)H- and (13)C-NMR, UV-Vis and mass spectroscopic data.

Magnetic nanoparticle (MNP)-supported crown ethers were successfully prepared and evaluated as catalysts for solid-liquid phase-transfer reactions; the catalytic activities of the MNP-supported crown ethers were not inferior to those of non-supported crown ethers; after the reactions, the catalysts could be readily separated using an external magnet and reused without significant loss of cataly...

The first hybrid crown ether with two adjacent disilane fragments was synthesized through reaction of O(Si2Me4Cl)2 (3) with O(C2H4OH)2. By means of DFT calculations, the complexation ability of 1,2,4,5-tetrasila[12]crown-4 (7) towards Li+ was determined to be considerably higher compared to [12]crown-4.

Background & Aims: Crown restoration of teeth after root canal treatment protects their remaining structure against breakage and infection of the root canal, and will replace the missing structure. This study was performed to identify the prevalence of different types of crown restorations after root canal treatment of posterior teeth in Kerman, Iran, in 2013. <stro...

this study demonstrates the spectral data for two triarylmethane dyes, malachite green (mg) and crystal violet (cv) at room temperature. effects of micellar environment, and crown ether addition on the spectral behaviour of the dyes were studied using absorption spectroscopic method. the dye-anionic surfactant interactions in micellar media were investigated. the chosen surfactants with differe...