| shock wave | <radiobiology> Wave produced (for example, in a gas or plasma) as a result of a sudden violent disturbance. To produce a shock wave in a given region, the disturbance must take place in a shorter time than the time required for sound waves to traverse the region. (09 Oct 1997) |
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| shock wave lithotripsy | A method of fragmenting calculi. (05 Mar 2000) |
| short wave diathermy | Therapeutic elevation of temperature in the tissues by means of an oscillating electric current of extremely high frequency (10 to 100 million Hz) and short wavelength of 3 to 30 meters. (05 Mar 2000) |
| short-wave therapy | The use of focused short radio waves to produce local hyperthermia in an injured person or diseased body area. (12 Dec 1998) |
| spike and wave complex | A generalised, synchronous pattern seen on the electroencephalogram, consisting of a sharply contoured fast wave followed by a slow wave; particularly found in patients with generalised epilepsies. Spike and wave complexes are often characterised by their frequency, e.g., s low spike and wave, fast spike and wave. (05 Mar 2000) |
| square wave stimuli | Electrical stimulation in which the intensity of the current is brought suddenly to a given level and maintained at that level until it suddenly is cut off; this type of stimulus is particularly useful in obtaining a strength-duration curve. (05 Mar 2000) |
| delta wave | A premature upstroke of the QRS complex due to an atrial ventricular bypass tract as in WPW syndrome. Synonym: delta rhythm. (05 Mar 2000) |
| S wave | A negative (downward) deflection of the QRS complex following an R w; successive downward deflections within the same QRS complex are labelled S', S'', etc. (05 Mar 2000) |
| dicrotic wave | The second rise in the tracing of a dicrotic pulse. Synonym: recoil wave. (05 Mar 2000) |
| drift wave | <radiobiology> Oscillations in a magnetically-confined plasma arising in the presence of density gradients (such as at the plasma's surface). These resemble the waves that propagate at the interface of two fluids with different density in a gravitational field. (09 Oct 1997) |
| D wave | A positive or negative deflection in the electroretinogram occurring when a light stimulus is removed (off-response). (05 Mar 2000) |
| quarter-wave plate | <microscopy> A compensator giving a retardation of about 130 nm, and a phase shift of 1/4 ~, thus constituting a device used with a polarizer and analyser designed to produce circularly polarized light. (05 Aug 1998) |
| Q wave | The initial deflection of the QRS complex when such deflection is negative (downward). (05 Mar 2000) |
| overflow wave | The descending wave of the sphygmogram from the apex to the first anacrotic break. (05 Mar 2000) |
| theta wave | Brain waves in the electroencephalogram which have a frequency of 4 to 7 per second. They occur mainly in children but also in adults during periods of emotional stress. (12 Dec 1998) |