Three-dimensional Brownian diffusion of rod-like macromolecules in the presence of randomly distributed spherical obstacles: Molecular dynamics simulation

Brownian diffusion of rod-like polymers in the presence of randomly distributed spherical obstacles is studied using molecular dynamics (MD) simulations. It is observed that dependence of the reduced diffusion coefficient of these macromolecules on the available volume fraction can be described reasonably by a power law function. Despite the case of obstructed diffusion of flexible polymers in which reduced diffusion coefficient has a weak dependence on the polymer length, this dependence is noticeably strong in the case of rod-like polymers. Diffusion of these macromolecules in the presence of obstacles is observed that is anomalous at short time scales and normal at long times. Duration time of the anomalous diffusion regime is found that increases very rapidly with increasing both the polymer length and the obstructed volume fraction. Dynamics of diffusion of these polymers is observed that crosses over from Rouse to reptation type with increasing the density of obstacles.Comment: 7pages, 6 figures, accepted for publication in JCP, 201

Chemical composition and antifungal effects of three species of Satureja (S. hortensis, S. spicigera, and S. khuzistanica) essential oils on the main pathogens of strawberry fruit

Due to an increasing risk of chemical contamination upon the application of synthetic fungicides to preserve fresh fruits and vegetables, essential oils are gaining increasing attentions. In this research, besides chemical analysis of the essential oils of three Satureja species (S. hortensis, S. spicigera, and S. khuzistanica) by GC-MS, their fungicidal and/or fungistatic effects on postharvest pathogens of strawberry were investigated. Essential oils were extracted by means of hydro-distillation and afterwards GC/MS analysis was performed to identify their components. Carvacrol, γ-terpinene and p-cymene were detected as the repeating main constituents of the spices, while thymol and carvacrol methyl ether were found as major components only in S. spicigera oil. In vitro results showed that at the maximum concentration, the essential oils did not possess fungicidal effects on Aspergillus niger but they exhibited fungicidal activities against Penicillium digitatum, Botrytis cinerea and Rhizopus stolonifer. However, S. khuzistanica was the strongest oil in fungicidal activity. S. hortensis oil was more effective than S. spicigera against B. cinerea whereas S. spicigera oil showed stronger fungicidal activity against R. stolonifer. In conclusion, essential oils isolated from three savory species could be suitable for applications in the food industry to control molds and improve the safety of fruits and vegetables. © 2015 Elsevier B.V