Series of green laser diodes (LDs) with different (In)GaN barrier layers are investigated. It is found that the optical confinement factor of multi-quantum well (MQW) always increases with increasing indium content of InGaN barrier layer, which results in a decrease of threshold current when indium content of InGaN barrier layer increases from 0 to 5%. However, when a high In content InGaN barrier is used (> 5%), both threshold current and slop efficiency of LDs deteriorate. It may be attributed to the waste of carriers in the potential well at the interface between the last barrier (LB) and the upper waveguide (UWG) layers, which is induced by the piezoelectric polarization effect in high In content InGaN LB layer. Therefore, a new LD structure using a thin thickness of the LB layer to reduce the effect of polarization shows a low threshold current and a high output power even when the In content of barrier layers is as large as 7%.

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Flavobacterium columnare is the causative agent of columnaris disease. Different genetic groups of F. columnare show to some extent different degrees of virulence. To identify genetic differences between the high virulence strain G(4) and the low virulence strain G(18) of F. columnare, suppression subtractive hybridization was used. A total of 46 genes were identified from the virulent strain G(4), 35 of which showed some degree of homology with known proteins and can be classified into 11 categories: DNA replication or recombination proteins, inorganic ion transport proteins, outer membrane proteins, enterotoxin, binding proteins, YD repeat proteins, transposase, chaperon, signal transduction-related proteins, regulatory proteins, metabolism-related proteins. Several putative virulence factors identified in other bacteria could also be identified in the virulent strain G(4), such as ferrous iron transport protein, TonB-dependent receptor, transposases, as well as ABC transporter permease protein. The flanking region of a putative transposase ISFclI was analysed, and a putative Rhs element was located at the downstream of the putative transposase. The analysis of isfclI gene in 24 strains of F. columnare isolated in China revealed that 11 strains have isfclI, and all the strains from Zhaoqing, Anhui and Qingjiang have isfclI.