Regulation of Turing patterns in a spatially extended chlorine-iodine-malonic-acid system with a local concentration-dependent diffusivity.

A chlorine-iodine-malonic-acid Turing system involving a local concentration-dependent diffusivity (LCDD) has fundamental significance for physical, chemical, and biological systems with inhomogeneous medium. We investigated such a system by both numerical computation and mathematical analysis. Our research reveals that a variable local diffusivity has an evident effect on regulating the Turing patterns for different modes. An intrinsic square-root law is given by λ ∼ (c(1)+c(2)k)(1/2), which relates the pattern wavelength (λ) with the LCDD coefficient (k). This law indicates that the system pattern has the properties of an equivalent Turing pattern. The current study confirms that, for the Turing system with LCDD, the system pattern form retains the basic characteristics of a traditional Turing pattern in a wide range of LCDD coefficients.

[A study of the determination of H2O2 in solid food by enzyme-oxygen electrode].

OBJECTIVE: A oxygen-electrode method is developed for the determination of H2O2 residues in solid food. METHODS: The hydrogen peroxide can be decomposed specifically into water and oxygen by catalase. The oxygen-electrode has high selectivity with the dissolved oxygen (DO). After H2O2 in the samples is extracted by PBS and the system is deoxidized by nitrogen, the DO can be detected by oxygen meter and then the content of H2O2 in samples will be calculated according to the result. RESULTS: The linear range is from 0.5 microg/ml to 7.5 microg/ml r > 0.999. The detection limit is 0.13 microg/ml. The recoveries are between 90.59%-93.88%. BSD is below 10%. CONCLUSION: The method has been used for the detection of H2O2 in health-preservation products of calcium, dried small shrimps, bean curd et al, it proved to be a simple rapid method.