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Background, Basis of Presentation and Liquidity (Details Narrative) - USD ($)					6 Months Ended
	Nov. 20, 2020	Sep. 18, 2020	Oct. 24, 2019	Jan. 07, 2019	Oct. 31, 2020	Dec. 07, 2020	Apr. 30, 2020
Accumulated deficit					$ (226,545,000)		$ (220,136,000)
Cash, cash equivalents and restricted cash, at carrying value					$ 15,850,000		$ 10,930,000
2019 ATM Facility [Member] | Subsequent Event [Member]
Cash, cash equivalents and restricted cash, at carrying value						$ 26,300,000
2019 ATM Facility [Member] | Alliance Global Partners [Member]
Aggregate offering price				$ 25,000,000
Number of common stock shares sold				10,942,100
Proceeds from issuance or sale of equity, net of issuance costs				$ 11,100,000
Combined purchase price per share				$ 1.01
Payment of sales commission				$ 360,095
2020 ATM Facility [Member] | Alliance Global Partners [Member] | Subsequent Event [Member]
Aggregate offering price	$ 50,000,000
Stock Purchase Agreement [Member] | Aspire Capital Fund, LLC [Member]
Number of common stock shares sold		6,424,205			500,000
Proceeds from issuance or sale of equity, net of issuance costs		$ 4,000,000			$ 600,000
Combined purchase price per share		$ 0.63			$ 1.23
Aggregate purchase of common stock		$ 12,500,000
Percentage of outstanding common stock limit for shareholder approval		19.99%
Number of shares can be issued based upon outstanding percentage		3,722,251
Stock Purchase Agreement [Member] | Aspire Capital Fund, LLC [Member] | Maximum [Member]
Aggregate purchase of common stock			$ 10,000,000

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