An improved method of watermarking picture identification documents such as passports, driver’s licenses, identification cards and the like which combines biometric information with digital watermarking to provide an improved secure picture ID document and authentication of same. By rapidly precharging the first positive side node, the clock feedthrough effect is eliminated and the locking period of the VCO is shortened. A test method to determine the degree of stain resistance to common household products is also described. The remoting agent on the physical desktop mimics host operations that are necessary to direct graphics data to a remote site. Also described are diagnostic and screening applications stemming from the inventor’s discovery that Neprilysin is expressed at reduced levels in disease tissues.