Abstract: The friction clutch comprises a reaction plate designed to be blocked on a driving shaft, a friction disk, bearing at its external periphery friction linings, a pressure plate, a cover (52) fixed on the reaction plate, an axially operating clutching device (53) controlled by a disengaging device and which operate between the cover (52) and the pressure plate through a support device, the pressure plate being integral in rotation with the cover (52) and being subjected to the action of an elastic return device (9) axially returning the pressure plate towards the cover (52). The clutch also comprises a wear take-up device comprising a toothed gear (59) with which a worm screw (63) co-operates and a device (90) for resetting in the position corresponding to linings in new condition, the device (90) being placed at the worm screw (63) tip to drive the latter in rotation.

Abstract: The friction clutch comprises a cover (8) with a base (80), a pressure plate (3) with a front friction face (30) for co-operating with a clutch friction and, set between the pressure plate (3) and the base (80) of the cover (8), a diaphragm (2) with a peripheral part extended inward by fingers (23) to oppose at will, by means of a nose (11) of a clutch bearing (10), the action of said peripheral part (21), a booster elastic washer (7) acting on the fingers (23) of the diaphragm (2) in the declutching direction resting on the cover (8): the booster washer (7) is arranged between the cover (8) and the leading-edge piece or nose (11) such that it is adapted to operate on the fingers (23) of the diaphragm (2) via said leading-edge piece or nose (11).

Abstract: Gradient pulses are applied during the common periods and with homothetic shapes on each of three imaging axes of an NMR machine in order to form oblique images. This results in a simplification of programming of the supplies of the gradient pulse application device.

Abstract: By synchronizing the radio-frequency excitations of a nuclear magnetic resonance experiment with the heart beat of a patient, notable improvement is obtained in the measurement of the molecular diffusion parameters of the tissues studied. In particular, good images of the brain are obtained in this way: the parameter represented is the molecular diffusion constant.

Abstract: The invention proposes an imaging process by nuclear magnetic resonance in which a calculated image is given corresponding to the molecular diffusion value at each point of an investigated medium. The diffusion image is obtained by comparing images relative to same sections of the medium and acquired during two excitation sequences, whereof one is not very sensitive to the diffusion and the other is particularly sensitive thereto. These two images undergo comparison in order to produce a diffusion image.

Abstract: In order to generate a radiofrequency excitation signal in an installation for NMR imaging, the envelope of the radiofrequency pulse is deduced from the shape of the selected cross-section which would result from application of a radiofrequency pulse having an envelope representing the desired selected cross-section shape.

Abstract: The invention proposes an imaging process by nuclear magnetic resonance in which a calculated image is given corresponding to the molecular diffusion value at each point of an investigated medium. The diffusion image is obtained by comparing images relative to same sections of the medium and acquired during two excitation sequences, whereof one is not very sensitive to the diffusion and the other is particularly sensitive thereto. These two images undergo comparison in order to produce a diffusion image.