“
“The blends of pectin (PEC) and

poly(vinyl alcohol) (PVA) at different components ratios were prepared by mixing in water. Thin polymeric films of PEC/PVA blends and pure polymers were obtained by casting method. All samples were then artificially aged using Suntest apparatus (Atlas) up to 780 h. The changes in chemical structure during sample ageing have been monitored by infrared and ultraviolet-visible absorption spectroscopies. The first stage of weathering (up to similar to 300 h) was very slow and alteration of chemical structure was negligible in all samples. Prolonged ageing (>300 h) caused more significant degradation VX-680 processes. FTIR spectra exhibited the highest changes in hydroxyl and carbonyl band ranges indicating the efficient photooxidation of macromolecules. The mechanisms of the observed processes have been discussed. It was found that PVA undergoes faster photoxidative degradation than pectin aged at the same conditions. The

PEC/PVA blends exhibited the improved resistance to weathering comparing with both polymers aged individually. Mutual stabilization effect can be explained by intermolecular interactions between PEC and PVA confirmed by spectroscopic methods. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122: 1936-1945, 2011″
“One problem in imaging is due to coexistence of double stable responses which can reduce the precision of find protocol Go 6983 research buy the images. Our target is comparing coexistence of double responses in liquid with responses obtained in air. Contact forces have some differences in liquid in comparison to air in magnitude and in the formulation. Hydrodynamic forces are also applied on the cantilever. This may change the nonlinear dynamics of tapping-mode Atomic Force Microscopy (AFM) in liquid in comparison to air. In this paper, we have simulated a tapping-mode AFM (TMAFM)

cantilever in liquid environment and explored the existence of multi responses in amplitude and phase diagrams. For modeling we have used a continuous beam model with its first mode and forward-time simulation method for the solution of its hybrid dynamics. Frequency response results of the simulation show a good agreement with experiments. The results for studying the nonlinear dynamics of an AFM microcantilever show that while there are two stable responses in air, in liquid just one response exists. Amplitude diagrams show that there is not any shift from low amplitude to high amplitude and both diagrams of sweeping up and down of the driving frequency coincide on each other. Average force diagrams show that in liquid there is not any repulsive regime and the magnitude of attractive force is small too. Sensitivity analysis for studying the effect of the free amplitude shows that in common setpoints double responses do not occur in liquid.