Financial instruments (Tables)

6 Months Ended

Jun. 30, 2014

Investments All Other Investments [Abstract]

Fair Value of Financial Instruments Measured At Fair Value on a Recurring Basis

The following tables present the fair value of our financial instruments that are measured at fair value on a recurring basis:

	QUOTED PRICES IN ACTIVE MARKETS FOR IDENTICAL ASSETS (LEVEL 1)		OTHER OBSERVABLE INPUTS (LEVEL 2)		SIGNIFICANT UN- OBSERVABLE INPUTS (LEVEL 3)			TOTAL
BALANCES – June 30, 2014
Short-term investments – U.S. government agency securities	$	17,989,220	$	—	$	—		$	17,989,220
Investments – bank term deposits		—		46,835		—			46,835
Investments – U.S. treasury securities		16,440,338		—		—			16,440,338
Bank loan warrant derivative liabilities		—		—		(93,096	)		(93,096	)
	$	34,429,558	$	46,835	$	(93,096	)	$	34,383,297
BALANCES – December 31, 2013
Short-term investments – bank term deposits	$	—	$	2,820,600	$	—		$	2,820,600
Bank loan warrant derivative liabilities		—		—		(221,320	)		(221,320	)
Redemption option on preferred stock		—		—		(800,206	)		(800,206	)
		—	$	2,820,600	$	(1,021,526	)	$	1,799,074

Fair Value of Significant Unobservable Inputs

Fair value of significant unobservable inputs (Level 3):

	BANK LOAN WARRANT DERIVATIVE LIABILITIES			PREFERRED STOCK EMBEDDED DERIVATIVE LIABILITIES		TOTAL
Three months ended June 30, 2014:
BALANCES - March 31, 2014	$	107,597		$	—	$	107,597
Change in fair value of derivative liabilities		(14,501	)		—		(14,501	)
BALANCES – June 30, 2014	$	93,096		$	—	$	93,096

	BANK LOAN WARRANT DERIVATIVE LIABILITIES			PREFERRED STOCK EMBEDDED DERIVATIVE LIABILITIES			TOTAL
Six months ended June 30, 2014:
BALANCES - January 1, 2014	$	221,320		$	800,206		$	1,021,526
Change in fair value of derivative liabilities		(128,224	)		—			(128,224	)
Derecognition of liabilities upon preferred stock conversion to common stock conversion		—			(800,206	)		(800,206	)
BALANCES – June 30, 2014	$	93,096		$	—		$	93,096