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The phenomenon of nuclear quadrupole resonance is akin to nuclear magnetic resonance, which is the basis of magnetic-resonance imaging. But unlike MRI scanners, instruments based on nuclear quadrupole resonance are not required to generate strong magnetic fields. This technique is thus suitable for detecting land mines, an application for which it would be difficult to project a uniform magnetic field into the ground. Although many different technical measures are available to search for land mines and other kinds of hidden explosives (including trained dogs, electronic metal detectors and ground-penetrating radar), instruments based on nuclear quadrupole resonance offer some special advantages. In particular, they are highly discriminating, being able to sense the presence of various nitrogen-rich compounds used in explosives. Nuclear quadrupole resonance offers the possibility of being applied to other tasks as well, including the nondestructive evaluation of materials.