Share-Based Compensation

Share-based Compensation

We utilize share-based compensation in the form of stock options and restricted stock. The following table summarizes the components of share-based compensation expense for the years ended December 31, 2018 and 2017 ($ in thousands):



	Year Ended December 31,
	2018		2017
Research and development	$	446	$	269
General and administrative	2,007		1,694
Discontinued operations	—		889
Total share-based compensation expense	$	2,453	$	2,852

The approval of the 2017 Hitachi Transaction (see Note 3) by our stockholders resulted in a change in control under our equity compensation plans (as defined in the 2009 Plan and the 2015 Equity Plan, and, together with the 2009 Plan, the “Equity Compensation Plans”). Accordingly, all outstanding unvested equity awards were accelerated upon the Closing Date, resulting in an acceleration of $1.9 million of equity compensation for the years ended December 31, 2017. In addition, in connection with the 2017 Hitachi Transaction, the Company agreed to extend the post-termination option exercise period for all PCT employees transitioning to Hitachi from 90 days to the earlier of (i) two years (May 18, 2019) or (ii) the date of the employees' termination from PCT. The post-termination option exercise period modification resulted in an additional expense of $0.3 million in 2017 and recorded in discontinued operations, since there were no future service requirements to receive the extended benefit.

Total compensation cost related to unvested awards not yet recognized and the weighted-average periods over which the awards are expected to be recognized at December 31, 2018 were as follows ($ in thousands):



	Stock Options		Restricted Stock
Unrecognized compensation cost	$	540	$	—
Expected weighted-average period in years of compensation cost to be recognized	1.95		0.00

Total fair value of shares vested and the weighted average estimated fair values of shares granted for the years ended December 31, 2018 and 2017 were as follows ($ in thousands):



	Stock Options
	Year Ended December 31,
	2018		2017
Total fair value of shares vested	$	218	$	5,002
Weighted average estimated fair value of shares granted	2.61		1.72

Valuation Assumptions

The fair value of stock options at the date of grant was estimated using the Black-Scholes option pricing model. The expected volatility is based upon historical volatility of the Company’s stock. The expected term for the options is based upon observation of actual time elapsed between date of grant and exercise of options for all employees.

The range of assumptions made in calculating the fair values of stock options was as follow:



	Stock Options
	Year Ended December 31,
	2018	2017
Expected term - minimum (in years)	5.5	6
Expected term - maximum (in years)	6	6
Expected volatility - minimum	68%	71%
Expected volatility - maximum	73%	74%
Weighted Average volatility	72%	35%
Expected dividend yield	—	—
Risk-free interest rate - minimum	2.35%	1.99%
Risk-free interest rate - maximum	2.96%	2.28%