Goodwill and intangible assets (Tables)

6 Months Ended

Jun. 30, 2013

Goodwill and intangible assets

Schedule of changes in carrying amount of goodwill

Goodwill, gross, as of December 31, 2012	$	347,599
Impact of change in Euro exchange rate	(5,391		)
Accumulated impairment losses as of June 30, 2013	—
Goodwill, net, as of June 30, 2013	$	342,208

Schedule of the gross book value, accumulated amortization and amortization periods of intangible assets

	As of June 30, 2013							As of December 31, 2012							Amortization
	Gross book		Accumulated			Net book		Gross book		Accumulated			Net book		period
	value		amortization			value		value		amortization			value		(years)
Trademarks and patents	$	994,977	$	(290,035	)	$	704,942	$	917,456	$	(258,325	)	$	659,131	15
Technology	2,849,847		(629,724		)	2,220,123		2,894,742		(351,018		)	2,543,724		5
Customer contracts	867,354		(867,354		)	—		867,354		(780,619		)	86,735		5
Intangible assets, net	$	4,712,178	$	(1,787,113	)	$	2,925,065	$	4,679,552	$	(1,389,962	)	$	3,289,590

Schedule of amortization expense related to intangible assets

	Three months ended June 30,				Six months ended June 30,
	2013		2012		2013		2012
Amortization expense	$	199,882	$	117,044	$	404,175	$	174,021