Acknowledgement
In writing this paper, I have benefited from the presence of my teachers
and my colleagues. They generously helped me collect materials I needed
and made many invaluable suggestions. I hereby extend my grateful thanks
to them for their kind help. Particularly, I am deeply indebted to
Professor Qian Zhai, my supervisor, who guided me throughout my writing
of this thesis. She carefully read the whole draft and offered
painstaking and precious criticism. Her standards of academic excellence
have made my revision and exciting and gratifying experience. I also
wish to sincerely thank my director, whose brilliant ideas and
perceptive observations have proved immensely constructive. Furthermore,
none of this would have been possible without the help of those
individuals and organizations hereafter mentioned with gratitude: our
department and its staff, the department of cardiovascular surgery of
qilu hospital of shandong university and its staff.