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Show 13. Be easy to transport by a single man on skis. 14. Offer no inconvenience for transport of any object carried by the victim. 15. Have no adverse effects on the victim. Possible detection schemes fall into two categories: A. Victim does not carry any object specifically related to detect ion. B. Victim carried a special signaling device. Obviously, a workable detection scheme based on the first category is more desirable. At present, all proposed schemes, regardless of category have certain shortcomings. Some are totally inadequate, including the repeatedly advanced suggestion that a radioactive tracer be carried by the victim. The following sections review the various technical possibilities. In Category A the following possibilities exist. 2.6.1 Sound Emission Conscious buried victims can often hear sounds of the rescuers above. Sound transmission in the opposite direction is much poorer, but from very shallow depths the victim can sometimes make his shouts heard. He can seldom be heard if deeply buried. Rescue groups can utilize the former possibility by calling out to the victim and listening carefully. Even if the rescuers listen with an audio amplifier this method has its limitations, for the victim cannot respond if unconcious and will quickly use up his limited oxygen by shouting if he does respond. A more reliable sound source is the victim's heartbeat. Theoretically this ought to be detectable at the surface with sufficiently sensitive apparatus. But the limitations of poor energy coupling between victim and surrounding snow and strong absoprtion in the snow itself, coupled with external noise sources, would make this a very uncertain detection method. 2.6.2 Heat Radiation A living body is at a higher temperature than the snow and emits infrared radiation to its surrounding. Unfortunately snow is such an efficient absorber of infrared that it is practically opaque at these wave lengths. This effect would not be detectable more than a few millimeters from the body. 2.6.3 Head Conduction Conduction of heat from the buried victim eventually will alter locally the surface temperature of snow if the snow is subfreezing. Wet snow at 49 |