6. Warrant Liabilities

Liabilities measured at market value on a recurring basis include warrant liabilities resulting from our past equity financings. In accordance with ASC 815-40, Derivatives and Hedging – Contracts in Entity's Own Equity ("ASC 815-40"), the warrant liabilities are being marked to market until they are completely settled. The warrants are valued using the Black-Scholes method, using assumptions consistent with our application of ASC 505-50, Equity-Based Payments to Non-Employees ("ASC 505-50"). The gain or loss resulting from the marked to market calculation is shown on the Condensed Statements of Operations as gain (loss) on warrant derivative liability. We recognized a loss of $32,000 and $0.2 million for the three-month periods ended March 31, 2017 and 2016, respectively. The following reflects the weighted-average assumptions for each of the three-month periods indicated:

	Three Months Ended March 31,
	2017			2016

Risk-free interest rate		1.05	%		0.21	%
Expected dividend yield		0	%		0	%
Expected lives		0.98			0.34
Expected volatility		95.1	%		86.8	%
Warrants classified as liabilities (in shares)		28,515,071			6,371,854
Loss on warrant liabilities	$	(32,119	)	$	(184,272	)

Our computation of expected volatility is based on the historical daily volatility of its publicly traded stock. The dividend yield assumption of zero is based upon the fact that we have never paid cash dividends and presently has no intention to do so. The risk-free interest rate used for each warrant classified as a derivative is equal to the U.S. Treasury rates in effect at March 31 of each year presented. The expected lives are based on the remaining contractual lives of the related warrants at the valuation date.