Goodwill and intangible assets (Tables)

6 Months Ended

Jun. 30, 2016

Goodwill and intangible assets

Schedule of changes in carrying amount of goodwill

Goodwill, gross, as of December 31, 2015	$	286,852
Impact of change in Euro exchange rate		5,189
Accumulated impairment losses as of June 30, 2016		—
Goodwill, net, as of June 30, 2016	$	292,041

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

	As of June 30, 2016						As of December 31, 2015						Amortization
	Gross book		Accumulated		Net book		Gross book		Accumulated		Net book		period
	value		amortization		value		value		amortization		value		(in years)
Trademarks and patents	$	1,198,419	$	(516,602)	$	681,817	$	1,184,612	$	(472,914)	$	711,698	15	-	21
Technology		2,432,061		(1,996,643)		435,418		2,388,852		(1,722,286)		666,566	5
Intangible assets, net	$	3,630,480	$	(2,513,245)	$	1,117,235	$	3,573,464	$	(2,195,200)	$	1,378,264

Schedule of amortization expense related to intangible assets

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2016		2015		2016		2015
Amortization expense	$	145,880	$	142,789	$	288,018	$	287,789