The table below summarizes the issuances of such warrants currently outstanding, including the Black-Scholes valuation model assumptions used to determine the fair value of the warrants:
| Date of Issuance | ||||||||||||||||
| December 2012 |
December 2011 |
June 2010 |
November 2007 |
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|
Aggregate shares pursuant to warrants issued |
154,638 | 158,311 | 254,793 | 50,331 | ||||||||||||
|
Per share exercise price of warrants issued |
$ | 3.88 | $ | 3.79 | $ | 7.0645 | $ | 12.67 | ||||||||
|
Fair value of warrants issued |
$ | 416,000 | $ | 390,000 | $ | 1,237,000 | $ | 474,000 | ||||||||
|
Expiration date of warrants |
December 9, 2019 | December 22, 2018 | June 18, 2017 | November 30, 2014 | ||||||||||||
|
Black-Scholes valuation inputs: |
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|
Expected volatility |
70.17 | % | 72.40 | % | 76.50 | % | 70.00 | % | ||||||||
|
Risk-free interest rate |
1.02 | % | 1.40 | % | 2.70 | % | 3.64 | % | ||||||||
|
Dividend yield |
0.00 | % | 0.00 | % | 0.00 | % | 0.00 | % | ||||||||
|
Expected term |
7 years | 7 years | 7 years | 7 years | ||||||||||||