highly significantP < 0.01
* Significant difference ( P < 0.05); ** Highly significant difference ( P < 0.01).
* Significant difference ( P < 0.05); ** Highly significant difference ( P < 0.01).
The independent sample t -test of SPSS version 18.0 was used to test the differences between groups, and P < 0.05 and P < 0.01 were considered significant difference and extremely significant difference, respectively.