Surface-dependent growth kinematics in euclidean 3-space

In this paper, we investigate the surface-dependent growth model in Euclidean 3-space. The surface-dependent model is developed for modeling the kinematics of surface growth for objects that can be generated by the curves on the surface, such as parasites and plants. This paper includes two main purposes for this model. The first is to parameterize this model using quaternions and homothetic motions, while expressing matrix representations of the surface-dependent growth model. The second one is to construct the surface-dependent growth model by using the growth velocity components related to the Darboux frame at each point of the generating curve. Moreover, to support the theory studied in the paper, various examples are illustrated.     

Adsorption of water and ammonia on TiO2-anatase cluster models

Density functional theory (DFT) calculations performed at B3LYP/6-31G^∗∗ level are employed to study water and ammonia adsorption and dissociation on (1 0 1) and (0 0 1) TiO₂ anatase surfaces both represented by totally fixed and partially relaxed Ti₂O₉H₁₀ cluster models. PM3 semiempirical calculations were also conducted both on Ti₂O₉H₁₀ and Ti₉O₃₃H₃₀ clusters in order to assess the effect of cluster size. Following dissociation, the adsorption of H₂O and NH₃ by H-bonding on previously H₂O and NH₃ dissociated systems, respectively are also considered. It is found that the adsorption energies and geometries of water and ammonia molecules on (1 0 1) and (0 0 1) anatase cluster models depend on surface relaxation. The vibration frequency values are also calculated for the optimized geometries. The adsorption energies and vibration frequency values computed are compared with the available theoretical and experimental literature.     

Cobalt-catalyzed arylation of azole heteroarenes via direct C-H bond functionalization

[reaction: see text] We herein report a new cobalt-catalyzed method for arylation of azole heteroarenes, including thiazole, oxazole, imidazole, benzothiazole, benzoxazole, and benzimidazole. The direct arylation of thiazole and oxazole was achieved both with iodo- and bromoarenes as the aryl donors in the presence of cobalt catalyst [Co(OAc)(2)/IMes] and cesium carbonate, while imidazole required the use of zinc oxide as the base. A complete reversal of arylation from C-5 to C-2 was accomplished using the bimetallic Co/Cu/IMes system. A direct comparison of the new cobalt method and the previously developed palladium protocol revealed significant differences, in terms of both chemical yield and selectivity.     

11B MAS NMR spectroscopic study of structural relaxation, aging, and memory effect at the atomic scale in a borosilicate glass

Relaxation kinetics of boron coordination environments in a borosilicate glass in response to temperature jumps has been monitored using (11)B magic-angle spinning (MAS) NMR spectroscopy. The relaxation time scale of the BO4/BO3 ratio is found to be closely comparable with those of the bulk properties, namely, refractive index and viscosity, showing a close connection with one another. Samples partially equilibrated at a low temperature, when subjected to a positive temperature jump, display an initial rapid decrease followed by an increase in the BO4/BO3 ratio. This reversal in the trend of the variation of the BO4/BO3 ratio has been interpreted to be the signature of a memory effect, and the implications are discussed within the framework of the potential energy landscape model of glassy dynamics.     

Thermal and electrical conductivities of silver–indium–tin alloys

The variations of thermal conductivity with temperature for the Ag–[x] wt% Sn–20 wt% In alloys (x=8, 15, 35, 55 and 70) were measured using a radial heat flow apparatus. From the graphs of thermal conductivity versus temperature, the thermal conductivities of solid phases at their melting temperature for the Ag–[x] wt% Sn–20 wt% In alloys (x=8, 15, 35, 55 and 70) were found to be 46.9±3.3, 53.8±3.8, 61.2±4.3, 65.1±4.6 and 68.1±4.8 W/Km, respectively. The variations of electrical conductivity of solid phases versus temperature for the same alloys were determined from the Wiedemann–Franz equation using the measured values of thermal conductivity. From the graphs of electrical conductivity versus temperature, the electrical conductivities of the solid phases at their melting temperatures for the Ag–[x] wt% Sn–20 wt% In alloys (x=8, 15, 35, 55 and 70) alloys were obtained to be 0.036, 0.043, 0.045, 0.046 and 0.053 (×10⁸/Ωm), respectively. Dependencies of the thermal and electrical conductivities on the composition of Sn in the Ag–Sn–In alloys were also investigated. According to present experimental results, the thermal and electrical conductivities for the Ag–[x] wt% Sn–20 wt% In alloys linearly decrease with increasing the temperature and increase with increasing the composition of Sn.     

Obtusallene I,a new halogenated allene from Laurencia Obtusa

Obtusallene, a new halogenated bicyclic ether with an allenic side chain, has been isolated from the red form of the alga Laurencia obtusa, and identified by spectroscopic methods and X-ray crystallography.