Curcumin exhibits superior anti-inflammatory, antiseptic and analgesic activities without significant side effects. However, clinical dissemination of this natural medicine is limited by its low solubility and poor bio-availability. To overcome this limitation, we propose to encapsulate curcumin in poly(lactic-co-glycolic acid) (PLGA) microparticles (MPs) by an improved coaxial electrospray (CES) process. This process is able to generate a stable cone-jet mode in a wide range of operation parameters in order to produce curcumin-loaded PLGA MPs with a clear core-shell structure and a designated size of several micrometers. In order to optimize the process outcome, the effects of primary operation parameters such as the applied electric voltages and the liquid flow rates are studied systemically. In vitro drug release experiments are also carried out for the CES-produced MPs in comparison with those by a single axial electrospray process. Our experimental results show that the CES process can be effectively controlled to encapsulate drugs of low aqueous solubility for high encapsulation efficiency and optimal drug release profiles.

Ritchmyer–Meshkov instability on an air/SF$_{6}$ interface is experimentally studied in a coaxial converging shock tube by a high-speed laser sheet imaging technique. An unperturbed case is first examined to obtain the characteristics of the converging shock and the shocked interface. For sinusoidal interfaces, the wave pattern and the interface morphology of the whole process are clearly observed. It is quantitatively found that the perturbation amplitude first decreases due to the shock compression, then experiences a rapid growth to a maximum value and finally drops quickly before the reshock. The reduction of growth rate is ascribed to the Rayleigh–Taylor stabilization caused by the interface deceleration motion that is present in the converging circumstance. It is noted that the influence of the wavenumber on the amplitude growth is very little before the reshock, but becomes significant after the reshock.

The β-nucleated polypropylene (β-PP) and polypropylene (PP) were coextruded to form the alternating layered structure with different layer number. During the isothermal crystallization of layered samples at 130°C, the high-density β-nuclei at the two-dimensional layered interfaces between β-PP and PP layers grew asymmetrically. In the β-PP layer, the growth of β-lamellae was quickly terminated by other β-spherulites. In the PP layer, because the formation of α-crystals delayed, all β-lamellae could freely grow perpendicular to the interface and finally form the β-transcrystallinity (β-TC) layer with about 25 μm thickness. If the thickness of PP layer was lower than 50 μm, PP layer would be almost occupied by β-TC. The ordered arrangement of β-TC led to an orientation of molecular chains of β-TC layer parallel to the interface. With the increase of layer number, the content of β-TC and orientation degree of layered samples increased. This paper provided a simple and effective method to prepare continuous, highly ordered and content-controlled β-TC. As a result, the sample with high content of β-TC exhibited good mechanical properties.

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