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Additional Paid-In Capital | 12 Months Ended
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Dec. 31, 2013
Additional Paid-In Capital [Abstract] |
Additional Paid-In Capital | 10. Additional Paid-in Capital
|  | Warrants |  |  | Stock options and RSUs |  |  | Compensation options |  |  | Other paid-in capital |  |  | Total additional paid-in capital
As of December 31, 2011 | $ | 10,288 |  | $ | 5,065 |  | $ | 588 |  | $ | 8,729 |  | $ | 24,670
Warrants issued |  | 3,260 |  |  | - |  |  | - |  |  | - |  |  | 3,260
Warrants exercised |  | (601) |  |  | - |  |  | - |  |  | 601 |  |  | -
Warrants expired |  | (11) |  |  | - |  |  | - |  |  | 11 |  |  | -
Stock options exercised |  | - |  |  | (50) |  |  | - |  |  | 50 |  |  | -
Stock options expired |  | - |  |  | (1,585) |  |  | - |  |  | 1,585 |  |  | -
Stock options amortization |  | - |  |  | 1,081 |  |  | - |  |  | - |  |  | 1,081
Compensation options exercised |  | - |  |  | - |  |  | (294) |  |  | 294 |  |  | -
Restricted stock units expensed |  | - |  |  | 3,144 |  |  | - |  |  | - |  |  | 3,144
As of December 31, 2012 |  | 12,936 |  |  | 7,655 |  |  | 294 |  |  | 11,270 |  |  | 32,155
Stock options amortization |  | - |  |  | 370 |  |  | - |  |  | - |  |  | 370
Restricted stock units expensed |  | - |  |  | 372 |  |  | - |  |  | - |  |  | 372
Restricted stock units vested |  | - |  |  | (410) |  |  | - |  |  | - |  |  | (410)
Compensation options expired |  | - |  |  | - |  |  | (294) |  |  | 294 |  |  | -
As of December 31, 2013 | $ | 12,936 |  | $ | 7,987 |  | $ | - |  | $ | 11,564 |  | $ | 32,487
Warrants Warrant activity is summarized in the following table:
|  | Warrants outstanding |  | Valuation |  | Weighted average exercise price per share |  | Weighted average remaining life (yrs.) |  | Intrinsic value
As of December 31, 2011 |  | 15,850,238 |  | 10,288 | $ | 3.91 |  | 3.7 | $ | 485
Exercised |  | (619,565) |  | (601) |  |  |  |  |  |
Expired |  | (10,871) |  | (11) |  |  |  |  |  |
Issued (Note 9) |  | 4,757,941 |  | 3,260 |  |  |  |  |  |
As of December 31, 2012 |  | 19,977,743 |  | 12,936 | $ | 4.25 |  | 2.6 | $ | -
As of December 31, 2013 |  | 19,977,743 | $ | 12,936 | $ | 4.63 |  | 1.6 | $ | -
The 19,977,743 outstanding warrants expire in the following time frames: 2,666,666 expire July 2014, 2,091,275 expire December 2014, and 15,219,802 expire in October 2015. The exercise price for the 15,219,802 warrants increased to $5.00 per common share during October 2013. The fair value of warrants issued during 2012 was estimated at the issue date using the Black-Scholes Merton fair value model adjusted to relative fair value using the following assumptions:
Expected volatility |  | 63.70% | - | 67.50%
Risk-free interest rate |  | 0.24% | - | 0.26%
Expected life (years) |  | 2
Dividend yield |  | N/A
Compensation Options
|  | Compensation options outstanding |  |  | Valuation |  |  | Weighted average exercise price per share |  | Expiry date |  | Weighted average remaining life (yrs.)
As of December 31, 2011 |  | 450,000 |  | $ | 588 |  | $ | 3.30 |  | April 2013 |  | 1.3
Exercised |  | (225,000) |  |  | (294) |  |  |  |  |  |  |
As of December 31, 2012 |  | 225,000 |  |  | 294 |  |  | 3.30 |  | April 2013 |  | 0.3
Expired |  | (225,000) |  |  | (294) |  |  |  |  |  |  |
As of December 31, 2013 |  | - |  | $ | - |  |  |  |  |  |  |
Stock-Based Compensation Under our Stock Option Plan (the “Plan”) and our Long-Term Equity Incentive Plan (the “LTIP”), we may grant options and/or RSUs or restricted stock awards (“RSAs”) to our directors, officers, employees and consultants. The combined maximum number of our Common Shares that may be reserved for issuance under the Plan and the LTIP is a variable number equal to 10% of the issued and outstanding Common Shares on a non-diluted basis. Options under the Plan are granted from time to time at the discretion of the Board of Directors of the Company (“Board”), with vesting periods and other terms as determined by the Board. The LTIP is administered by the Board, which can delegate the administration to the Compensation Committee of the Board or to such other officers and employees of Vista as designated by the Board. Stock-based compensation expense for t he years ended December 31, 2013, 2012 and 2011 is as follows:
|  | Year ended December 31,
|  | 2013 |  | 2012 |  | 2011
Stock options | $ | 370 | $ | 1,081 | $ | 1,496
Restricted stock units |  | 372 |  | 3,144 |  | 524
| $ | 742 | $ | 4,225 | $ | 2,020
As of December 31, 201 3, stock options and RSUs had unrecogni zed compensation expense of $1,400 and $1,811, respectively, which is expected to be recognized over a weighted average period of 5.0 and 1.82 years, respectively. Stock Options A summary of option activity under the Plan as of December 31, 201 3 and 201 2 and changes during the period then ended is set forth in the following table:
|  | Number of options |  | Weighted average exercise price per option |  | Weighted average remaining contractual term |  | Aggregate intrinsic value
Outstanding - December 31, 2011 |  | 3,195,000 | $ | 3.27 |  | 2.73 | $ | 1,039
Granted |  | 600,000 |  | 2.97 |  |  |  |
Exercised |  | (32,500) |  | 2.90 |  |  |  |
Expired |  | (660,000) |  | 2.80 |  |  |  |
Outstanding - December 31, 2012 |  | 3,102,500 |  | 2.80 |  | 2.68 |  | 637
Granted |  | 985,000 |  | 0.36 |  |  |  |
Cancelled/Forfieted |  | (450,000) |  | 3.07 |  |  |  |
Expired |  | (755,000) |  | 3.32 |  |  |  |
Outstanding - December 31, 2013 |  | 2,882,500 | $ | 1.79 |  | 3.07 | $ | 54
Exercisable - December 31, 2013 |  | 2,143,750 | $ | 2.29 |  | 2.40 | $ | 13
A summary of our unvested stock options as of December 31, 2013 and 2012 and changes during the period then ended is set forth in the following table:
|  |  |  |  |  | Number of options |  | Weighted average grant-date fair value per option |
Unvested - December 31, 2011 |  |  |  |  |  | 597,000 | $ | 1.60 |
Granted |  |  |  |  |  | 600,000 |  | 1.47 |
Vested |  |  |  |  |  | (897,000) |  | 1.56 |
Unvested - December 31, 2012 |  |  |  |  |  | 300,000 |  | 1.47 |
Granted |  |  |  |  |  | 985,000 |  | 0.22 |
Vested |  |  |  |  |  | (546,250) |  | 0.90 |
Unvested - December 31, 2013 |  |  |  |  |  | 738,750 | $ | 0.22 |
The fair value of stock options granted to employees, directors and consultants was estimated at the grant date using the Black-Scholes option pricing model using the following assumptions:
|  |  |  |  | Years ended December 31,
|  |  | 2013 |  | 2012 |  | 2011
Expected volatility |  |  | 72.26% |  | 81.69% | - | 83.67% |  | 83.40% | - | 83.86%
Risk-free interest rate |  |  | 1.70% |  | 0.77% | - | 0.88% |  | 0.88% | - | 1.60%
Expected life (years) |  |  | 5 |  | 5 |  | 5
Dividend yield |  |  | N/A |  | N/A |  | N/A
Option pricing models require the input of highly subjective assumptions, including the expected price volatility. Expected price volatility is based on the historical volatility of our Common Shares. Changes in the subjective input assumptions can materially affect the fair value estimate. The expected term of the options granted is derived from the output of the option pricing model and represents the period of time that the options granted are expected to be outstanding. The risk-free rate for the periods within the contractual term of the option is based on the U.S. Treasury yield curve in effect at the date of grant. Restricted Stock Units The following table summarizes the RSU activity under the LTIP as of December 31, 2013 and 2012 and changes during the years then ended:
|  | Number of units |  | Weighted average grant-date fair value per RSU
Unvested - December 31, 2011 |  | 960,000 | $ | 3.84
Cancelled |  | (107,832) |  | 3.07
Granted |  | 1,142,339 |  | 3.20
Unvested - December 31, 2012 |  | 1,994,507 |  | 3.50
Cancelled |  | (1,133,592) |  | 2.58
Vested |  | (116,875) |  | 3.51
Granted |  | 1,850,424 |  | 0.82
Unvested - December 31 , 2013 |  | 2,594,464 | $ | 2.00
A portion of the RSU awards vest on a fixed future date provided the recipient continues to be affiliated with Vista on that date. Other RSU awards vest subject to certain performance criteria, including the accomplishment of certain corporate objectives and the Company’s share price performance. The vesting period for time based RSUs is at least one year.

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