Comparison of prolonged antibacterial activity and release profile of propolis‐incorporated PVA nanofibrous mat,microfibrous mat,and film

Propolis as a natural antibacterial agent was incorporated into the poly(vinyl alcohol) (PVA) in different forms of nanofiber, microfiber, and film. The successful fabrication of uniform nanofibers with 85–314 nm diameters and microfibers with 2.02 μm diameter was proved by scanning electron microscopy. Structural analysis by Fourier transform infrared spectroscopy and X‐ray diffraction and swelling properties confirmed the formation PVA hydrogel and its H‐bonding to the propolis. Evaluation and comparison of antimicrobial properties of produced samples against Staphylococcus aureus strains revealed that nanofiber mat with 19 mm inhibition zone has 11.76 and 26.67% higher efficiency against bacteria than microfiber mat and film with 17 and 15 mm inhibition zone, respectively. Nanofibrous mat showed sustained release during 96 h by maintaining full antibacterial activity up to 51 h which is of great importance in burn wounds. These results confirm the advanced performance of natural propolis in the form of nanofiber substrate as wound dressing. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45794.     

Nonlinear size-dependent pull-in instability and stress analysis of thin plate actuator based on enhanced continuum theories including nonlinear effects and surface energy

Microsystem Technologies - In recent years, size dependent continuum theories have been commonly used to simulate material discontinuities in micro/nano-scales. In the present article, modified...     

Wave propagation in double-walled carbon nanotube conveying fluid considering slip boundary condition and shell model based on nonlocal strain gradient theory

In this paper, wave propagation in fluid-conveying double-walled carbon nanotube (DWCNT) was investigated by using the nonlocal strain gradient theory. In so doing, the shear deformable shell theory was used, taking into consideration nonlocal and material length scale parameters. The effect of van der Waals force between the two intended walls and the DWCNT surroundings was modeled as Winkler foundation. The classical governing equations were derived from Hamilton’s principle. Results were validated by comparing them to the results of the references obtained through molecular dynamic method, and a remarkable consistency was found between the results. According to the findings, the effects of nonlocal and material length scale parameters, wave number, fluid velocity and stiffness of elastic foundation are more considerable in the nonlocal strain gradient theory than in classical theory.     

The modified couple stress functionally graded cylindrical thin shell formulation

In this article, the functionally graded (FG) cylindrical thin shell formulation is developed by using modified couple stress theory. The equations of motion and classical and nonclassical boundary conditions are extracted based on Hamilton's principle. As a special case, the equations of motion in conjunction with the boundary conditions for simply supported FG cylindrical shell are obtained, and then Navier solution procedure is used for analysis free vibration of nano shell. Afterwards, the influences of different parameters like length scale parameter, distribution of FG properties, and length to radius ratio on dimensionless natural frequency are investigated and compared with classical theory.