4. Intangible and Other Assets, Net

Intangible and other assets, net, were comprised of the following at December 31:

In thousands	2011			2010
Capitalized patent and license costs	$	6,799		$	6,465
Purchased technology		5,901			5,901
		12,700			12,366
Less accumulated amortization		(6,957	)		(5,332	)
		5,743			7,034
Other assets		42			38
	$	5,785		$	7,072

Amortization expense for intangible assets amounted to $1.7 million, $0.9 million and $1.0 million in 2011, 2010 and 2009, respectively. The weighted average amortization period for intangible assets was 14.9 years, 14.8 years and 15.2 years in 2011, 2010 and 2009, respectively. The estimated future amortization expense is $470,000 for 2012 and $435,000 per year for 2013, 2014, 2015, 2016 and $3.5 million thereafter.

For the years ended December 31, 2011, 2010 and 2009, the Company recorded charges in research and development expense of $312,000, $2.4 million and $47,000, respectively, to reflect impairment of the carrying value of certain capitalized patents and licenses. In 2010, the charges relate to the write-off of the carrying value of patents related to the Company’s NF-кB technology, upon unsuccessful conclusion of litigation related to this technology, and an impairment of the carrying value of the ARGENT patents and certain other patents based on an assessment of future cash flows anticipated from these technologies.