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Share-Based Payments (Details 1)
3 Months Ended
Jul. 31, 2015
Jul. 31, 2014
Risk-free interest rates Minimum   0.95%
Risk-free interest rates Maximum 1.774% 2.24%
Volatility Minimum 87.80% 94.08%
Volatility Maximum 92.08% 102.50%
Dividend yield 0.00% 0.00%
Minimum [Member]    
Expected term in years 5 years 2 years 6 months
Risk-free interest rates Minimum 1.57%  
Maximum [Member]    
Expected term in years 6 years 6 years