1. ; Department of Natural Resource Ecology and Management; Iowa State University; Ames 50011-1021 Iowa
2. ; Program in Environmental Materials Science, Department of Forest Products; Seoul National University; San 56-1 Sillim-Dong, Kwanak-gu 151-742 Seoul South Korea
3. ; Department of Food Science & Human Nutrition; Iowa State University; Ames 50011-1021 Iowa