A novel mode of retinal regeneration:the merit of a new Xenopus model

Retinal regeneration： The retina is a part of the central nervous system （CNS） and has long attracted neurobiologists as an excellent model organ for the study of CNS regeneration. In classical studies using urodele amphibians like the salamander newt, it has been shown that the retina regenerates after the removal of the whole tissue even in the adulthood. This type of regeneration is considered as an example of ＂transdifferentiation＇, since the source of the regenerating retina is the retinal pigmented epithelial cells （RPE cells） （Okada, 1991;

Stable analysis on speed-adaptive observer in regenerating mode

Speed-adaptive full-order flux observer is the most promising flux estimator among all the sensorless control method.However,conventional speed-adaptive flux observer becomes unstable during regenerating operation at low speed since induction motor is an observable system except dc excitation.Thus,the instability problem is caused by inappropriate designing of observer.Based on the eigenvalues of extended observer,this paper interprets unstable situation,that the eigenvalues of extended ob-server have a positive real part.Therefore,the observer cannot converge.Against the two different solutions for unstable prob-lem-positive real maintaining and current error augment,the proposed method based on the eigenvalue could unify these two solutions,which gives the complete stability condition for speed-adaptive full-order observer.It does a lot help in observer de-signing.The observer configured by this proposed method was verified in the torque controlling of 20 kW induction motor.According to the experiment result,with appropriate designing of observer,the unstable situation during regeneration mode could be completely overcome.

Community Characteristics of Early Recovery Vegetation on Abandoned Lands of Shifting Cultivation in Bawangling of Hainan Island, South China

: Shifting cultivation is a major form of agricultural practice in most parts of tropical regions worldwide. In places where the bush fallow period is excessively shortened or the period of cultivation is extended for too long, the rate of vegetation recovery and biodiversity on abandoned lands of shifting cultivation would decline. The recovery of the secondary plant communities could even be inhibited for a prolonged period because of grass occupancy. Because of the vital significance of the early recovery communities to secondary succession, we studied the community characteristics of early recovery vegetation on abandoned lands of shifting cultivation in Bawangling of Hainan Island. Measurements were made of the community composition and structure of early recovery vegetation. The sprouting abilities of different functional groups and different species in the same functional group, and the effect of the grass functional group on the composition and quantitative characteristics of tree and shrub functional groups were analyzed. Results indicated that only a few families, genera, or species apparently dominated in the early recovery vegetation on the abandoned lands of shifting cultivation and that deciduous species occurred with a rather high percentage in this early recovery community compared with the natural secondary or old growth forests. Small-sized individuals dominated the woody community. The abundance and basal area of sprouting stems for species in the tree functional group were greater than those of seeder stems, whereas the abundance and basal area of resprouters and seeders for species in the shrub functional group did not differ. The total abundance of stems for the community, stem abundances for species in tree or shrub functional groups, and for seeder or resprouter stems were all negatively correlated with coverage of the grass functional group. The mean sprouting ability in the tree functional group was greater than in the shrub functional group. The sprouting ability for different species in the same functional group was also significantly different.