<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="6.x">Drupal-Biblio</source-app><ref-type>13</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Gheorghe Paun</style></author><author><style face="normal" font="default" size="100%">Juan Pazos-Sierra</style></author><author><style face="normal" font="default" size="100%">Mario J. Pérez-Jiménez</style></author><author><style face="normal" font="default" size="100%">Alfonso Rodríguez-Patón</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Symport/Antiport P systems with three objects are universal</style></title><secondary-title><style face="normal" font="default" size="100%">Fundamenta Informaticae</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Membrane computing</style></keyword><keyword><style  face="normal" font="default" size="100%">register machine</style></keyword><keyword><style  face="normal" font="default" size="100%">symport/antiport</style></keyword><keyword><style  face="normal" font="default" size="100%">Turing computability</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2005</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://portal.acm.org/citation.cfm?id=1227085.1227115&coll=GUIDE&dl=GUIDE&CFID=2475207&CFTOKEN=63580860</style></url></web-urls></urls><publisher><style face="normal" font="default" size="100%">IOS Press</style></publisher><pub-location><style face="normal" font="default" size="100%">Warsaw, Poland</style></pub-location><volume><style face="normal" font="default" size="100%">64</style></volume><pages><style face="normal" font="default" size="100%">353-367</style></pages><abstract><style face="normal" font="default" size="100%">The operations of symport and antiport, directly inspired from biology, are already known to be rather powerful when used in the framework of P systems. In this paper we confirm this observation with a quite surprising result: P systems with symport/antiport rules using only three objects can simulate any counter machine, while systems with only two objects can simulate any blind counter machine. In the first case, the universality (of generating sets of numbers) is obtained also for a small number of membranes, four. 

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