Highly regulated folding of plasmid DNA (pDNA) through polyion complexation with the synthetic block catiomer, poly(ethylene glycol)-block-poly(L-lysine) (PEG-PLys), was found to occur in such a way that rod structures are formed with a quantized length of 1/2(n + 1) of the original pDNA length folding by n times. The folding process of pDNA was elucidated with regard to rigidity of the double-stranded DNA structure and topological restriction of the supercoiled closed-circular form, and a mechanism based on Euler's buckling theory was proposed. Folded pDNA exhibited higher gene expression efficiency compared to naked pDNA in a cell-free transcription/translation assay system, indicating that the packaging of pDNA into a polyion complex core surrounded by a PEG palisade is a promising strategy for constructing nonviral gene carrier systems. Extension of this finding may provide a reasonable model to further understand the packaging mechanism of supercoiled DNA structures in nature.

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Waveforms of acoustic emission (AE) events come close and sometimes overlap each other when AE activity is very high. Conventional AE measurement systems which handle discrete AE events are not suitable for this situation because miss-detection of AE event occurs frequently. A new AE measurement system named as Continuous Wave Memory (CWM) was developed to solve this problem by recording the AE waveforms continuously to hard disks for several hours throughout the testing time. This new system enabled multiple analysis of one waveform with different filtering parameters. Short time Fourier transform (STFT) gave the time-frequency-magnitude characteristic of continuous AE waveforms and useful information for evaluation of degradation of materials. In this study, the degradation of ceramic fiber mat during cyclic compression test and the effect of binder-addition were evaluated by this new system. STFT results clearly showed the classification of degradation of the mat; breakage of fibers was the main source in the early compression cycles and sporadic friction between fibers became the main source of AE in the later compression cycles. The effect of organic binder to prevent the degradation of the mat was also estimated. It was observed that the friction signal disappeared and the breakage signal weakened in the binder-added specimens.

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