Intense radiofrequency power in the form of pulses is applied to an ensemble of spins in a liquid placed in a large static magnetic Geld H&. The frequency of the pulsed r-f power satisGes the condition for nuclear magnetic resonance, and the pulses last for times which are short compared with the time in which the nutating macroscopic magnetic moment of the entire spin ensemble can decay. After...

This study investigates how multiple echoes reflected from adjacent buildings influence the speech intelligibility of outdoor public address systems when aircraft noise is added. To accomplish this, the sound of an aircraft flying over industrial areas was recorded from the vicinity of an airport in Tokyo and then added to speech sounds at a signal-to-noise ratio (SNR) of -5 dB. Then, the speec...

The acoustic environment for an echolocating bat can contain multiple objects that reflect echoes so closely separated in time that they are almost completely overlapping. This results in a single echo with a spectrum characterized by deep notches due to interference. The object of this study was to document the possible selectivity, or lack thereof, of auditory neurons to the temporal separati...

Stimulated echoes are formed from three or more radio frequency pulses. Pulse sequences that use stimulated echoes are extremely versatile because of the availability of three pulses for timing variations and for encoding spatial or chemical shift information. This paper concentrates on the uses of stimulated echoes and on techniques for obtaining them reliably and reproducibly. (Through this u...

Background-During ventricular echoes, reentrant excitation is supposed to involve 2 functionally distinct pathways in the atrioventricular (AV) nodal area. The exact pathway of reentrant excitation is unknown. The objectives of this study were to analyze electrical activity in the AV nodal area after ventricular stimulation and during ventricular echoes and to assess the role of perinodal atria...