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Share-Based Payments (Details 1)
3 Months Ended 6 Months Ended
Oct. 31, 2015
Oct. 31, 2014
Oct. 31, 2015
Oct. 31, 2014
Expected term in years 6 years      
Risk-free interest rates Minimum 1.63% 1.53% 1.57% 0.79%
Risk-free interest rates Maximum 1.72% 1.94% 1.72% 1.94%
Volatility Minimum 87.46% 85.80% 87.46% 85.80%
Volatility Maximum 87.81% 102.10% 92.32% 102.10%
Dividend yield 0.00% 0.00% 0.00% 0.00%
Minimum [Member]        
Expected term in years   5 years 5 years 3 years
Maximum [Member]        
Expected term in years   6 years 6 years 6 years