Summary:We describe a vector scanning system to reduce charging effects during scanning electron microscope (SEM) imaging. The vector scan technique exploits the intrinsic charge decay mechanism of the specimen to improve imaging conditions. We compare SEM images obtained by conventional raster scanning versus vector scanning to demonstrate that vector scanning successfully reduces specimen-charging artifacts.

Fourteen cases of lymphonla of the Burkitt type were found in a retrospective review of histopathological material in Singapore over a IS-year period (1950IS-year period ( -1964 This report is based on a review of histopathological material in Singapore over a 15-year period (1950)(1951)(1952)(1953)(1954)(1955)(1956)(1957)(1958)(1959)(1960)(1961)(1962)(1963)(1964). Previous reviews of the incidence of cancer in Singapore (Shanmugaratnam and Muir, 1967) and of cancer in Singapore children (Muir, 1961) have not included reports of the occurrence of lymphomas of the Burkitt type in Singapore.Singapore, a small island of 224.5 sq. miles, lies I " 17". and 103" 50'E. in South East Asia. Much of the island is low lying, the highest elevation being a hill 581 feet above sea level.The marine, equatorial climate is warm, moist and equable. The average temperature is 85"F, the average relative humidity is 83% and the mean annual rainfall is 95 inches. There are no seasons.The population has been well documented by censuses held in 1947 (del Tufo, 1949) and in 1957 (Chua, 1964. The total population in 1957 was 1,445,929, comprising Chinese (75.4 %), Malays (1 3.6 %), Indians and Pakistanis (8.6 %) and Other Races (2.4%). There were 754,783 persons in the 0-19 age group, comprising 52.2% of the total population.Singapore enjoys a good medical service and the doctor: population ratio has improved from 1:3,000 in 1952 to 1:2,000 in 1964. The diagnostic histopathological service, available to all hospitals and private practitioners, is centralized in the Institute of Pathology which houses the University and Government Departments of Pathology. Necropsies are performed on approximately 22% of all deaths and on more than 40% of deaths in the 0-24 year age group (Muir, 1964). There is no comprehensive cancer registration scheme, but the Institute of Pathology maintains a card index of all histologically confirmed cancer cases in Singapore.