An improved double-toroidal spectrometer for gas phase (e,2e) studies

A new spectrometer is described for measuring the momentum distributions of scattered electrons arising from electron-atom and electron-molecule ionization experiments. It incorporates and builds on elements from a number of previous designs, namely, a source of polarized electrons and two high-efficiency electrostatic electron energy analyzers. The analyzers each comprise a seven-element retarding-electrostatic lens system, four toroidal-sector electrodes, and a fast position-and-time-sensitive two-dimensional delay-line detector. Results are presented for the electron-impact-induced ionization of helium and the elastic scattering of electrons from argon and helium which demonstrate that high levels of momentum resolution and data-collection efficiency are achieved. Problematic aspects regarding variations in collection efficiency over the accepted momentum phase space are addressed and a methodology for their correction presented. Principles behind the present design and previous designs for electrostatic analyzers based around electrodes of toroidal-sector geometry are discussed and a framework is provided for optimizing future devices.The assistance of the AustralianGerman Research Cooperation Scheme and the Australian Research Council through Grant No. DP0452553 and a 1998 ARC RIEF grant is gratefully acknowledged

Results of Aortocoronary Bypass Surgery for Angina Pectoris

To determine the relative risks and benefits of coronary bypass surgery for angina pectoris, we examined the results in our first consecutive 360 patients operated upon between May 1970 and December 1975. The age range was 27 to 75 years; there were 309 males and 51 females. The patients were classified clinically as having stable angina in 119 cases (33%), unstable angina in 205 cases (57%) and preinfarction angina in 36 cases (10%). Unstable angina was defined as a definite recent increase in severity or frequency of chest pain, angina at rest or nocturnal angina. Preinfarction angina was defined as a syndrome of prolonged angina, poorly controlled by nitrites, occurring at rest with typical ECG changes of ischemia. Such patients underwent observation in the Coronary Intensive Care Unit followed by emergency arteriography and surgery, usually within 24 hours