A system and method of wireless communication determines received signal timing deviation which is used to generate a timing advance for adjusting wireless transmit receive unit transmissions. A slug of material fusible at a selected critical temperature is positioned on a heat conductive surface. An economic process for making the fertilizer is also provided. , R4 is hydrogen or lower alkyl, R5 is hydrogen, lower alkyl, cycloalkyl lower alkyl or lower alkenyl,or a pharmaceutically acceptably salt, or a solvate thereof is provided.