The surface of superparamagnetic iron oxide nanoparticles (SPIO) with different molecular weight of poly(ethylene glycol) (PEG) and folic acid (FA) were synthesized. The SPIO-PEG-FA nanoparticles are well-dispersed and have good stability in various pH solutions. The lack of hysterestis and remanence at ambient temperatures is characteristic of superparamagnetic materials for SPIO-PEG-FA. The uptake by macrophage for SPIO-PEG-FA is lower than that of Feridex I.V. even at higher concentration. Internalization of SPIO-PEG-FA in targeted cells (KB cells) was observed by flow-cytometric analysis and in vitro MR imaging. The intensity change of positive KB cell tumor (-20 to 25%) is significantly lower than that of negative HT-1080 cell tumor from precontrast to postcontrast images of the tumor by in vivo MR imaging. These preliminary results demonstrated that SPIO-PEG-FA have the ability to target folate receptor.

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In this study a simple displacement field is proposed for finite element vibration analysis of circular plates. The displacement field is a combination of a conventional field, which is very popular for three-dimensional vibration analysis of circular plates or cylinders, and another field, which is most general for axisymmetric vibration. The investigation here is intended, through mathematical formulation and examples, to verify the existence of coupled axisymmetric vibration modes. These modes cannot be found by conventional displacement field, but can easily be revealed by the present model. Validity and accuracy of the proposed displacement field to show all the prominent vibration modes of circular plates or cylinder-like structures is also demonstrated by comparing results using the present method with those of a three-dimensional finite element analysis and experiments.

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