BACKGROUND Multiple risk factors have been identified for traumatic dental injuries, including crown fractures, in various age groups and various populations. The objective of this study was to determine the prevalence, risk factors and family related factors for crown trauma among 8 to 16 year-old children in a suburban population, Nigeria. METHODS This is a secondary analysis of a data of 2...

The title compound, (NH4)2[Zn(NCS)4]·2C12H24O6·H2O, the result of the reaction of ammonium thio-cyanate, 18-crown-6 and zinc(II) chloride in aqueous solution, exhibits an unusual supra-molecular structure. The Zn atom, two of the thio-cyanate chains and a water mol-ecule, disordered over two positions, lie on a mirror plane. The macrocycle adopts a conformation with approximate D 3d symmetry. T...

It is well known that a splash occurs when an object impacts at high velocity on a liquid’s surface. If the impact is fast enough, surface tension and air pressure gradients pull the crown-shape splash all the way towards the axis of symmetry, making it to collapse and seal the surface. In this paper we show that splash and surface sealing are also observed in impacts on soft, dry sand. We obse...

2,4-dithiouracil (DTU) forms in the crystals the H-bonded monohydrates of a 1:1:1 ratio with 18-crown-6 (18C6) 1, cis,syn,cis-isomer of dicyclohexano-18-crown-6 (DCH6A) 2, and benzo-18-crown-6 (B18C6) 3, while the anhydrous adduct with cis,anti,cis-isomer of dicyclohexano-18-crown-6 (DCH6B) 4 is of a 2:1 ratio. In 1-3 the components reproducibly alternate in the chains, while in 4 the chains ar...

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...

Crown profile models were developed for north, east, south, and west crown directions of dominant trees, intermediate trees, and suppressed trees in planted stands of Larix olgensis Henry in Northeast China. A total of 139 sample trees were randomly selected, and all branches of each tree were measured. A segmented power equation, segmented polynomial equation, modified Weibull equation, and Ko...

Supramolecular cations formed by monoprotonated pyridazinium cations and cis-anti-cis-dicyclohexano[18]-crown-6 (DCH[18]-crown-6) or dibenzo[18]-crown-6 (DB[18]-crown-6) were introduced into [Ni(dmit)2]− salts (where dmit2− = 2-thione-1,3-dithiole-4,5-dithiolate). X-ray crystal structure analysis of (pyridazinium+)(DCH[18]-crown-6)[Ni(dmit)2]− (1) revealed a chair-type conformation of the DCH[1...

In the title compound, [BaCl(C(12)H(24)O(6))(H(2)O)(3)]Cl, the Ba(II) atom, the coordinating and free Cl(-) anions, one coordinating water mol-ecule and two O atoms of an 18-crown-6 mol-ecule lie on a mirror plane. The environment of the ten-coordinate Ba(2+) ion is defined by one Cl atom, three water mol-ecules and six O atoms from the macrocyclic ether. The macrocycle adopts a conformation wi...

The synthesis and cation-binding properties of a series of Calixarene derivatives possessing alkyl chain groups, ester groups and crown ether rings have been investigated. The syntheses of Calix[4]arene crown ethers and Calix[6]arene derivatives possessing alkyl chain, ester group and crown ether ring have been described. In order to evaluate their monovalent cation binding abilities, solvent e...

Abrasion of dental crown and the shape of denture occlusal surface are significant indicators in age determination of domestic mammals. The factors that significantly influence age determination of Eneolithic deer game in conditions of an open wildlife habitat are climatic changes that influenced their survival, as well as specific features of teeth morphological structure. In this paper the ag...