Summary In this paper, an iterative cell image segmentation algorithm using short‐time Fourier transform magnitude vectors as class features is presented. The cluster centroids of the magnitude vectors are obtained by the K‐means clustering method and used as representative class features. The initial image segmentation classifies only those image pixels whose surrounding closely matches a class centroid. The subsequent procedure iteratively classifies the remaining image pixels by combining their spatial distance from the regions already segmented and the similarities between their corresponding magnitude vectors and the cluster centroids. Experimental results of the proposed algorithm for segmenting real cell images are provided.

Abstract. Pot experiments were conducted to assess the possibly adverse effect of transgenic Bt-and CpTI-cotton (Bacillus thuringiensis and cowpea trypsin inhibitor cotton) on soil ecosystem. Soil enzymes activities and microbial molecular community and diversity based on 16s-and 18s-PCR-DGGE (polymerase chain reaction-denaturing gradient gel electrophoresis) profiles were determined by adding root exudates of Bt-and CpTI-cotton into soil. Results showed that the root exudates of transgenic cotton seedlings increased the soil catalase activity by 21.8% to 32.7%. The soil urease activity was decreased by 11.0% while the activity in the treatment of 1ml/350g soil was increased by 18.1% compared to control. The invertase activity in the treatment of 1 ml/350g soil was increased by 54.2%, however, the activity in the treatments of 2 and 4 ml/350 g soil was decreased by from 25% to 29.2%. The total 16sPCR-DGGE lane bands of bacterial community and diversity were almost not different. However, the effect pattern of root exudates of transgenic cotton on soil fungal community and diversity was differed from bacteria. The fungal community number and composition were changed. Though some dominant community disappeared and other newly dominant community appeared, the fungal stability index was increased. Results suggested there was little significantly adverse effect of Bt-and CpTI-cotton on soil ecosystem.

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