Aerodynamic interaction between forewing and hindwing of a hovering dragonfly

The phase change between the forewing and hindwing is a distinct feature that sets dragonfly apart from other insects.In this paper,we investigated the aerodynamic effects of varying forewing-hindwing phase di ff erence with a60 inclined stroke plane during hovering flight.Force measurements on a pair of mechanical wing models showed that in-phase flight enhanced the forewing lift by 17%and the hindwing lift was reduced at most phase differences.The total lift of both wings was also reduced at most phase di ff erences and only increased at a phase range around in-phase.The results may explain the commonly observed behavior of the dragonfly where 0 is employed in acceleration.We further investigated the wing-wing interaction mechanism using the digital particle image velocimetry（PIV）system,and found that the forewing generated a downwash flow which is responsible for the lift reduction on the hindwing.On the other hand,an upwash flow resulted from the leading edge vortex of the hindwing helps to enhance lift on the forewing.The results suggest that the dragonflies alter the phase di ff erences to control timing of the occurrence of flow interactions to achieve certain aerodynamic effects.

Rescue of the albino phenotype by introducing a functional tyrosinase minigene into Kunming albino mice

AIM： To use the tyrosinase minigene as a visual marker to perform microinjection training and improve the techniques related with transgene to greatly elevate the effidency of gene transfer. METHODS： A mouse tyrosinase minigene, i.e., TyBS, in which the 2.25-kb authentic genomic 5＇ non-coding flanking sequence of mouse tyrosinase was fused to a mouse tyrosinase cDNA, was introduced into the fertilized eggs of outbred Kunming albino mice. RESULTS： Of the 11 animals that developed from the injected eggs, two mice （P1 and #8） exhibited pigmented hair （P1） and eyes （P1 and #8）, as confirmed by PCR analysis for the tyrosinase minigene integrated into the genome. When founder P1 was bred to Kunming male mouse, six progeny out of 11 offspring inherited the transgene and the pigmented-eye phenotype. CONCLUSION： Taken together, these results suggest that this minigene encodes the active tyrosinase protein and that its 5＇ flanking region contains the sequences regulating the expression of mouse tyrosinase gene as expected. We have rescued the albino phenotype by introduction and expression of a functional tyrosinase minigene in the Kunming albino mouse and the transgene can be passed to subsequent generation. These findings also indicate that TyBS can be a useful visual marker gene in the co-transgenic experiments.