Share-Based Payments (Details 1)	3 Months Ended
	Jul. 31, 2013	Jul. 31, 2012
Expected term in years	6 years	6 years
Risk-free interest rates Minimum	1.38%	0.80%
Risk-free interest rates Maximum	1.91%	0.90%
Volatility Minimum	96.40%	98.50%
Volatility Maximum	100.60%	98.80%
Dividend yield	0.00%	0.00%