Stockholders' equity (Tables)

9 Months Ended

Sep. 30, 2015

Stockholders' Equity Note [Abstract]

Warrant and option activity

Warrant activity (including warrants issued to investors and for consulting and advisory services) for the nine months ended September 30, 2015 and 2014 was as follows:

	For the nine months ended September 30,
	2015		2014
Beginning balance outstanding		23,933,922		7,977,990
Warrants issued during the year:
In connection with sales of common and preferred stock		-		17,918,675
In connection with issuance of convertible notes		1,983,340		-
Expired or cancelled during the year		(160,894)		(158,450)
Ending balance outstanding		25,756,368		25,738,215

Option activity for the nine months ended September 30, 2015 and 2014 was as follows:

	For The Nine Months Ended
	September 30,
	2015			2014
Beginning balance outstanding		8,807,667			1,566,667
Issued during the year:		600,000			5,918,000
Expired or cancelled during the year		(740,834	)		(110,000	)
Ending balance outstanding		8,666,833			7,374,667

Options and warrants outstanding

The numbers and exercise prices of all options and warrants outstanding at September 30, 2015 are as follows:

Shares Outstanding		Weighted Average Exercise Price		Expiration Fiscal Period
	478,312		7.53	4th Qtr, 2015
	300,000		6.50	1st Qtr, 2016
	1,465,833		6.75	2nd Qtr, 2016
	625		9.00	3rd Qtr, 2016
	666,811		7.55	4th Qtr, 2016
	34,749		7.99	1st Qtr, 2017
	1,709,810		7.05	2nd Qtr, 2017
	576,430		1.53	3rd Qtr, 2017
	1,542,338		6.71	4th Qtr, 2017
	10,000		6.60	1st Qtr, 2018
	22,275,623		1.09	1st Qtr, 2019
	893,336		0.92	2nd Qtr, 2019
	1,113,000		1.16	3rd Qtr, 2019
	2,623,000		1.15	4th Qtr, 2019
	525,000		0.92	1st Qtr, 2020
	75,000		0.65	2nd Qtr, 2020
	133,334		7.05	4th Qtr, 2022
	34,423,201

Stock based compensation assumptions used

The following weighted average assumptions were utilized for the calculations during the nine months ended September 30, 2015 and 2014:

	For The Nine Months Ended
	September 30,
	2015			2014
Expected life (in years)	2.89 years			4.23 years
Weighted average volatility		108.92	%		90.14	%
Forfeiture rate		14.21	%		11.43	%
Risk-free interest rate		.97	%		1.14	%
Expected dividend rate		0.00	%		0.00	%