Abstract: Mass spectrometers for trace gas leak detection and methods for operating mass spectrometers are provided. The mass spectrometer includes an ion source to ionize trace gases, such as helium, a magnet to deflect the ions and a detector to detect the deflected ions. The ion source includes an electron source, such a filament. The method includes operating the electron source at an electron accelerating potential relative to an ionization chamber sufficient to ionize the trace gas but insufficient to form undesired ions, such as triply charged carbon.

Abstract: A mass spectrometer includes a main magnet having spaced-apart polepieces which define a gap, the main magnet producing a magnetic field in the gap, an ion source to generate ions and to accelerate the ions into the magnetic field in the gap, the ion source located outside the gap, and an ion detector to detect a selected species of the ions generated by the ion source and deflected by the magnetic field. The ion detector is located in the gap at a natural focus point of the selected species of ions. The mass spectrometer may be used in a trace gas leak detector.

Abstract: The invention provides a series of novel heterocyclic ketones of formula I ##STR1## and pharmaceutically acceptable base-addition salts thereof, in which the values of R.sup.4, L, A, X and Q have the meanings defined in the following specification. The compounds of formula I are inhibitors of human leukocytic elastase. The invention also provides pharmaceutical compositions containing a compound of formula I, or a pharmaceutically acceptable base-addition salt thereof, and processes and intermediates for the manufacture of compounds of formula I.

Abstract: The embodiments of the disclosed controlled flexible membrane reflector show a system wherein the optical surface of a reflector is electrostatically controlled. By controlling the electric field acting on selected portions of the flexible membrane which bears the optical surface, the shape of the optical surface can by dynamically controlled. A figure sensor or image quality detector detects deviations of the reflecting surface of the membrane from the desired figure and a feedback control system adjusts selected portions of the electric field to return the reflective surface to its proper figure. The differential control of the electric field is accomplished by segmenting a back electrode and controlling the voltage on each segment individually. The control voltage varies around a nominal value applied to all segments which is required to deflect the surface into its desired shape.