ii Acknowledgements

I got great help from many people to complete my research. I would like to state my appreciation in this section. First, I thank my advisor, Dr. Sossina Haile for a lot of things. She gave me an opportunity to have very valuable experience in the U.S. She accepted me even though I had a language issue. I got strong support from her. The advice which she gave me was very valuable, not only for my research as a great scientist but also for my everyday life as a mother of young kids. I was very happy to join her group. I thank Dr. Tetsuya Uda, who instructed me when I started my research as a volunteer. I could not get the idea that I can construct any measurement equipment by myself until he suggested I make humidified TG. I learned how to survive in the lab at that time as my first step. I thank a machinist, Mike Vondrus for his great help and friendship. I could not build my measurement systems without his powerful help by his magical hands and deep knowledge. I thank his wife, Masako Vondrus for her kindness and friendship. I was very happy to meet them and spend time with them. I thank Dr. Mary Louie, who was my labmate, for her kindness, help, advice an