Since 1948, this series has filled the gap between the papers that report on and the textbooks that teach in the diverse areas of catalysis research. The editors of and contributors to Advances in Catalysis are dedicated to recording progress in this area. Each volume of Advances in Catalysis contains articles covering a subject of broad interest.Advances in Catalysis 44 reflects the expanding impact of experimental surface characterization on the understanding of catalysis. The catalysts emphasized here are representative of the complexity of today's technology; examples include catalysts for hydrocarbon re-forming, automobile exhaust conversion, and hydroprocessing to make clean-burning fossil fuels. This volume contains three obituaries recognizing the major contributions of Dr. Werner O. Hagg, Dr. Charles Kemball, and Dr. John Turkevich.