Development of a Synthetic Pathway Toward a Bowl-Shaped C 27H12 Polycyclic Aromatic Hydrocarbon

Bowl-shaped and basket-shaped polycyclic aromatic hydrocarbons (PAHs) have attracted considerable attention in recent years. They are challenging targets for total synthesis due to the presence of substantial strain energy in the curved structures. A solution-phase synthesis of a bowl-shaped polycyclic aromatic hydrocarbon C27H12 was explored. The use of the casecade radical cyclization reactions of a benzannulated enyne-allene is a key feature of this synthetic pathway. The mild reaction conditions provide efficient and flexible designs for bowl-shaped and basked-shaped PAHs and their precursors. Our proposed synthesis strategy for the bowl-shaped C27H12 involves an initial synthesis of a benzannulated enediynyl propargylic alcohols followed by the cascade cyclization reactions of the resulting enyne-allenes. The use of the palladium-catalyzed intramoleular arylation reactions is proposed as a key step leading to the final products. Specifically, transformation of 1-indanone to a key intermediate, 2-methoxy-2-(2- methoxyethyl)-1-indanone, was extensively investigated, and the conditions for forming 1-(2-ethynylphenyl)-2-(2,6-dichlorophenyl)ethyne via the Sonogashira reaction were established. Condensation between the 1-indanone and the ethyny1 derivatives produced the benzannulated enediynyl propargylic alcohol. Chlorinated P AHs as potential precursors leading to the bowlshpaed Cz1H12 hydrocarbon have been successfully synthesized

Throughput capacity of two-hop relay MANETs under finite buffers

Since the seminal work of Grossglauser and Tse [1], the two-hop relay algorithm and its variants have been attractive for mobile ad hoc networks (MANETs) due to their simplicity and efficiency. However, most literature assumed an infinite buffer size for each node, which is obviously not applicable to a realistic MANET. In this paper, we focus on the exact throughput capacity study of two-hop relay MANETs under the practical finite relay buffer scenario. The arrival process and departure process of the relay queue are fully characterized, and an ergodic Markov chain-based framework is also provided. With this framework, we obtain the limiting distribution of the relay queue and derive the throughput capacity under any relay buffer size. Extensive simulation results are provided to validate our theoretical framework and explore the relationship among the throughput capacity, the relay buffer size and the number of nodes

Reversible Transition Between Thermodynamically Stable Phases with Low Density of Oxygen Vacancies on SrTiO3_3(110) Surface

The surface reconstruction of SrTiO$_3$(110) is studied with scanning tunneling microscopy and density functional theory (DFT) calculations. The reversible phase transition between (4$\times$1) and (5$\times$1) is controlled by adjusting the surface metal concentration [Sr] or [Ti]. Resolving the atomic structures of the surface, DFT calculations verify that the phase stability changes upon the chemical potential of Sr or Ti. Particularly, the density of oxygen vacancies is low on the thermodynamically stabilized SrTiO$_3$(110) surface.Comment: Accepted by Physical Review Letter