A process for the recovery of plasmids or other DNA from cells using a first filtration step to remove the cellular debris and other large cellular components and then an ultrafiltration step to capture the plasmids or other DNA on the surface of the ultrafiltration membrane where they may be recovered. The electrode structure includes an alternating current electrode having the semiconductor elements on each of opposite surfaces, and a plurality of direct current electrodes holding therebetween the alternating current electrode and the semiconductor elements respectively mounted on the opposite surfaces of the alternating current electrode. The sub-mount has a first surface and a second surface opposite the first surface. During the certificate-based authentication procedure, an executable module is downloaded to the client from the server through the SSL session, after which the server receives through the SSL session a digital signature that has been generated by the executable module using a digital certificate at the client. , urea, of a biological sample, e.