Molecular dynamics study of epoxy/clay nanocomposites: rheology and molecular confinement

To investigate the effect of nanoparticles on molecular confinement, epoxy/clay nanocomposites in 6?% wt were prepared by low shear mixer and ultrasonication methods. According to the XRD results, high energy sonication can significantly increase the intergallery space compared to that of the low shear mixer and, therefore, provide more interfacial area for polymer-particle interaction. Rheological measurements, including dynamic mechanical moduli, continuous relaxation spectrum and zero-shear viscosity, were carried out in the linear region to reveal the solid-like characteristics induced in the pure epoxy. The longest Rouse relaxation time, which was determined from the value of zero-shear viscosity, was employed to study the segmental friction. It is clear that the chain relaxation process was slowed by the polymer-particle interactions, which created very high monomeric friction. We introduce the ratio of monomeric friction coefficients (??_nano/??_epoxy) as the strength of immobilization to correlate the increasing elasticity, longer relaxation time and molecular confinement quantitatively. Because more monomers can be immobilized on a clay surface due to their strong affinity, the friction ratio increased to 359.48 for the sonicated sample, whereas weak polymer-particle affinity resulted in much lower growth, with a friction ratio of 2.11 for the low shear mixing method.     

The effect of nisin and garlic (Allium sativum L.) essential oil separately and in combination on the growth of Listeria monocytogenes

In the present study, the anti-listerial activity of the nisin and garlic (Allium sativum L.) essential oils (GO) alone and in combination was investigated at different temperatures (20 and 30 °C), pH (6.8, 5.6 and 4.8) and NaCl concentrations (0, 0.5, 2.5 and 4.5 g/100 mL). Minimum inhibitory concentrations (MICs) against Listeria monocytogenes were assessed for the nisin and essential oil. Furthermore, for combinations of the antimicrobials, the Differences in Population (DP) method were used to determine their effect. Both essential oil and nisin possessed considerable antimicrobial effects on the microorganism. The MICs for nisin and GO were 12.5 IU/mL and 100 μg/mL, respectively. Regardless of NaCl concentration and temperature, the anti-listerial activity of both GO and nisin was strongly influenced by pH. Moreover, at the same temperature, and regardless of pH value, the growth of the organism was also affected by increasing NaCl concentration. In combination, the DP was related strongly to the agent’s concentration and media pH. Meanwhile, among all combined systems, the effect of the combination (EC) of nisin with GO at 30 °C, pH 5.6 and 0 g/100 mL NaCl, showed significant anti-listerial activity (P ≤ 0.05).     

A model for carbon nanotube FETs in the ballistic limit

As we know, a ballistic MOS-Like carbon nanotube FET can be simulated by using a self-consistent procedure between the charge and the Poisson equations. Because of the integral form of the charge equation, this model cannot be implemented in the commercially available circuit simulators, such as SPICE. In this paper, we propose an analytical solution for estimating the charge equation, so that the above mentioned procedure could be used in the aforementioned circuit simulators. We investigated the accuracy of the proposed model for various values of the physical parameters and biasing condition. Further investigations were performed in order to evaluate the model accuracy in the sub-threshold region and in presence of the short channel effects. The results of these investigations were compared with those obtained by some other models developed earlier in the literatures. All of these demonstrate superior accuracy of the proposed model with comparison to the other models.