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In the process of the fermentation of steroid C11α-hydroxylgenation strain Aspergillus flavus AF-ANo208, a red pigment is derived, which will affect the isolation and purification of the target product. Low energy ion beam implantation is a new tool for breeding excellent mutant strains. In this study, the ion beam implantation experiments were performed by infusing two different ions: argon ion (Ar + ) and nitrogen ion (N + ). The results showed that the optimal ion implantation was N + with an optimum dose of 2.08×10 15 ions/cm 2 , with which the mutant strain AF-ANm16 that produced no red pigment was obtained. The strain had high genetic stability and kept the strong capacity of C11α-hydroxylgenation, which could be utilized in industrial fermentation. The differences between the original strain and the mutant strain at a molecular level were analyzed by randomly amplified polymorphic DNA (RAPD). The results indicated that the frequency of variation was 7.00%, which would establish the basis of application investigation into the breeding of pigment mutant strains by low energy ion implantation.

Fiber-reinforced composites, due to their microstructural heterogeneity, may exhibit response phenomena for some environments that are not observed for homogeneous materials. An example of these phenomena for dynamic environments is wave dispersion, i.e., the dependence of the phase velocity Oft the wavelength. The simulation of response phenomena associated witb the material mlc~ostructure requires a bigheTorder continuum description. The couple-stress theory is a continuum theory in which each point of bodies possesses six degrees of freedom like a rigid body. Up to now, however, the investigations on couplestress theories for engineering materials have been scarce.

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