The relaxation phenomena are critical aspects of fruit rheological properties. Little detailed information is available on the non-homogeneous and anisotropic relaxation properties of fruits. The objective of this study was to determine the effects of specimen orientation and location with the pear on the equilibrium modulus, the decay modulus, time of relaxation, and specific viscosity in the relaxation model. The stress relaxation tests were performed on Dangshan pear using the Instron universal testing machine. The decay modulus, the equilibrium modulus, time of relaxation, and specific viscosity in the relaxation model are significantly influenced by specimen orientation, latitude, and depth. The longitude of the specimen and initial deformation are not significant.

The migratory locust is one of the most notorious agricultural pests that undergo a well known reversible, density-dependent phase transition from the solitary to the gregarious. To demonstrate the underlying molecular mechanisms of the phase change, we generated 76,012 ESTs from the whole body and dissected organs in the two phases. Comparing 12,161 unigene clusters, we identified 532 genes as phase-related (P<0.01). Comprehensive assessment of the phase-related expression revealed that, whereas most of the genes in various categories from hind legs and the midgut are down-regulated in the gregarious phase, several gene classes in the head are impressively up-regulated, including those with peptidase, receptor, and oxygen-binding activities and those related to development, cell growth, and responses to external stimuli. Among them, a superfamily of proteins, the JHPH superfamily, which includes juvenile hormone-binding protein, hexamerins, prophenoloxidase, and hemocyanins, were highly expressed in the heads of the gregarious hoppers and hind legs of the solitary hoppers. Quantitative PCR experiments confirmed in part the EST results. These differentially regulated genes have strong functional implications that numerous molecular activities are involved in phase plasticity. This study provides ample molecular markers and genomic information on hemimetabolous insects and insights into the genetic and molecular mechanisms of phase changes in locusts.

To find unknown protein-coding genes, annotation pipelines use a combination of ab initio gene prediction and similarity to experimentally confirmed genes or proteins. Here, we show that although the ab initio predictions have an intrinsically high false-positive rate, they also have a consistently low false-negative rate. The incorporation of similarity information is meant to reduce the false-positive rate, but in doing so it increases the false-negative rate. The crucial variable is gene size (including introns)-genes of the most extreme sizes, especially very large genes, are most likely to be incorrectly predicted.