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Traces of vanadium, manganese, iron, cobalt, nickel, copper, and zinc were quantitatively extracted with diethyldithiocarbamate (DDTC) in benzene from a digested solution of biological materials and the metal-DDTC complexes were collected into a small amount of polystyrene foam produced by lyophilization of the benzene extract after addition of polystyrene. The polystyrene foam was dissolved in benzene and spread on Mylar film. After drying, a polystyrene film containing metal-DDTC complexes was produced on Mylar film, and then the polystyrene film was peeled from the Mylar film. This film was subjected to PIXE analysis. This method was applied to NBS SRM 1572 citrus leaves and a marine macroalgal sample, and 6 trace metals were simultaneously and accurately determined.

A thin support film is indispensable to make targets of biological material for trace analysis by PIXE. We developed a simple technique for the preparation of high quality support film. Polyvinylformal (PVF) was dissolved in tetrahydrofuran (THF) and the solution was spread on the surface of sucrose solution. The THF was evaporated and a PVF film formed on the surface. The thickness of the PVF film was 0.1µm with good homogeneity. The PVF film was stable to 3MeV proton bombardment and no impurity elements were observed. The continuous X-ray background was <1/20 that of 280µg/cm² Mylar. We used the PVF film as a support film for some biological materials. Because of the lower X-ray background from the PVF film, K, Ca, Fe, Ni, Cu, Zn, As and Br in 50–100µg of biological materials could be detected.

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Cellular adhesion is mediated by the formation and rupture of specific molecular bonds between ligands and receptors. As an idealized model, based on the Markov process assumption, we present a detailed theoretical analysis of the stochastic dynamics of a cluster of parallel bonds between two rigid bodies with curved interfaces under displacement- and force-controlled loadings, respectively. Regarding the equilibrium cluster size, strength, bond distribution and life time, exact solutions from the corresponding one-step master equations are obtained for the special cases of clusters with fixed separations or clusters with flat interfaces, while the general cases of those with curved interfaces are dealt with numerical techniques. Especially, Monte Carlo simulations are performed to verify the proposed analytical results and to demonstrate interesting differences between stochastic adhesion behaviors of the clusters under loading protocols of fixed separations and fixed forces, respectively.