Pure annihilation decay of strange beauty meson into two charm heavy mesons

In this study, the heavy to heavy decay of \begin{document}$ B^0_s\rightarrow D^{*+}D^- $\end{document} is evaluated through the factorization approach by using the final state interaction as an effective correction. Under the factorization approach, this decay mode occurs only through the annihilation process, so a small amount is produced. Feynman's rules state that six meson pairs can be assumed for the intermediate states before the final meson pairs are produced. By taking into account the effects of twelve final state interaction diagrams in the calculations, a significant correction is obtained. These effects correct the value of the branching ratio obtained by the pure factorization approach from \begin{document}$ (2.41\pm1.37)\times10^{-5} $\end{document} to \begin{document}$ (8.27\pm2.23)\times10^{-5} $\end{document}. The value obtained for the branching ratio of the \begin{document}$ B^0_s\rightarrow D^{*+}D^- $\end{document} decay is consistent with the experimental results.     

Molecular dynamics simulation of gas adsorption on defected graphene

Gas sensing is one of the most promising applications for graphene. Using molecular dynamics simulation method, adsorption isotherm of xenon (Xe) gas on defected and perfect graphene is studied in order to investigate sensing properties of graphene for Xe gas. In this method, first generation of Brenner many-body potential is used to simulate the interaction of carbon–carbon (C) atoms in graphene, and Lennard–Jones two-body potential is used to simulate interaction of Xe–Xe and Xe–C atoms. In the simulated systems, adsorption coverage, radial distribution function, heat of adsorption, binding energy and specific heat capacity at constant volume are calculated for several temperatures between 90 K and 130 K, and various pressures. It was found that both of the defected and perfect graphene could be introduced as very good candidates for adsorption of Xe gas.     

Evaluation of occupational noise pollution and attitudes of exposed workers in two metal industries

The purpose of the present study was to determined noise levels and to show the annoyance reaction, hearing loss, hearing impairment by the workers due to the occupational noise exposure according to Iran development of Environment （IDE） and also awareness about effects of noise and use of hearing protective devices （HPD） in the two manufacturing electronic equipment （metal） industries. The present study was carried out among industrial workers and included a sample of lao workers, site 1 （n = 52） and site 2 （n = 78） from two metal industries located in south eastern Iran province of Kerman. In order to attend the objectives of the current study, noise levels evaluation was determined throughout all different work stations in both industries. The results of the study revealed that noise levels in 75% of the stations are higher than limits used for assessment of noise for community response. The result of the study indicated that noise levels in the workplace are （66%） very high, （28%） high and only 6% low. Workers having higher education are much aware of the health impact due to occupational noise. Chi-square analysis indicated that the difference in educational background and not wearing HPD was significant and also a significant relationship was also observed between the impact of occupational noise on the health and education status. This research has clearly demonstrated that the workers in both the metal industries included in this study are at high risk of developing noise induced hearing loss and other associated ailments due to excessive occupational exposure to noise. There is a need to develop and apply a well-defined, comprehensive and enforceable training programs and noise regulation. The study revealed that the workers having higher education （9-12 grades） are much aware of the health impact due to occupational noise exposure. There is a need to establish a hearing conservation programs in both industries, the components of such program include noise assessment, use of hearing protection devices, audiometric and increasing awareness among the workers about the adverse effects of noise.     

Rectangular-radial drawings of cubic plane graphs

Rectangular drawings and rectangular duals can be naturally extended to other surfaces. In this paper, we extend rectangular drawings and rectangular duals to drawings on a cylinder. The extended drawings are called rectangular-radial drawings and rectangular-radial duals. Rectangular-radial drawings correspond to periodic rectangular tilings of a 1-dimensional strip. We establish a necessary and sufficient condition for plane graphs with maximum degree 3 to have rectangular-radial drawings and a necessary and sufficient condition for triangulated plane graphs to have rectangular-radial duals. Furthermore, we present three linear time algorithms under three different conditions for finding a rectangular-radial drawing for a given cubic plane graph, if one exists.     

FeNH4(SO4)2·12H2O (alum)-catalyzed preparation of 1,4-dihydropyridines: improved conditions for the Hantzsch reaction

Abstract  

FeNH₄(SO₄)₂·12H₂O (alum) efficiently catalyzes the one-pot three-component reaction of dimedone, aldehydes, and 3-aminocrotonate to afford 1,4-dihydropyridines. The work-up is easy, and the products are obtained in good to excellent yields and high purity.     

Monitoring the effects of homogeneity methanol/water/monomer on the mode of polymerization of styrene: dispersion polymerization versus emulsion polymerization

The polymerization of styrene (St) was carried out with varying amounts of methanol in aqueous medium. As methanol content decreased (to 50 %), the phase of polymerization mixture (methanol/water/monomer) changed to a heterogeneous state; the homogeneous state was obtained in samples that contain 75 and 100 % methanol. In order to verify the mechanism of polymerization in heterogeneous and homogeneous mixtures, the nucleus formation rate during polymerization, the stability equilibrium of the media and seeded particles, and the size of particles and their growth in polymerization were experimentally being monitored. With the homogeneous mixture in 75 wt% methanol, dumbbell, triangle, and peanut-like particles have been formed. On the other hand, the characteristics of the polymerization products were different from those typically obtained in the emulsion polymerization and in the sample with 100 wt% methanol dispersion polymerization. In the sample with 100 % methanol and in one with 50 % methanol, monodispersed spherical particles are formed in the final conversion. Thus, homogeneity in the aqueous methanol mixture can be a critical factor in determining the polymerization modes between dispersion and emulsion polymerization.