4. Investment in Available-for-Sale Securities

The following is a summary of the Company’s investments in available-for-sale securities as of December 31, 2013:

	Cost		Unrealized Gains		Unrealized Losses		Fair Value
U.S. federal agency securities	$	90,549	$	93	$	(277)	$	90,365
Municipal securities		735,826		2,175		(6)		737,995
Certificates of deposit		1,539,377		12,281		(19,398)		1,532,260
Corporate debt securities		174,738		275		(9,091)		165,922
	$	2,540,490	$	14,824	$	(28,772)	$	2,526,542

The following is a summary of the Company’s investments in available-for-sale securities as of December 31, 2012:

	Cost		Unrealized Gains		Unrealized Losses		Fair Value
U.S. federal agency securities	$	19,592	$	196	$	-	$	19,788
Municipal securities		1,154,841		2,882		(2,090)		1,155,633
Certificates of deposit		1,193,494		8,734		(16,904)		1,185,324
Corporate debt securities		285,524		4,164		(9,633)		280,055
Equity securities – ClearSign common stock		7,905		9,485		-		17,390
	$	2,661,356	$	25,461	$	(28,627)	$	2,658,190

The Company’s investment portfolio had a net realized gain of $8,507and a realized loss of $30,378 for the years ended December 31, 2013 and 2012, respectively. The Company’s investment portfolio has thirty-seven positions with an unrealized loss as of December 31, 2013.

The cost and fair value of investments in fixed income available-for-sale debt securities, by contractual maturity, as of December 31, 2013, are as follows:

	Cost		Fair Value
Due within one year	$	805,714	$	797,042
Due after one year through three years		852,260		859,383
Due after three years		882,516		870,117
	$	2,540,490	$	2,526,542

Expected maturities will differ from contractual maturities because the issuers of certain debt securities have the right to call or prepay their obligations without any penalties. The Company has classified the entire fair value of its investment in available-for-sale debt securities as current assets in the accompanying balance sheets.