2016-02-022016-02-022013978-84-940691-9-2http://hdl.handle.net/11441/33819This paper continues an investigation into bridging two research areas con- cerned with natural computing: membrane computing and reaction systems. More specif- ically, the paper considers a transfer of two assumptions/axioms of reaction systems, non- permanency and the threshold assumption, into the framework of membrane computing. It is proved that: SN P systems with non-permanency of spikes assumption charac- terize the semilinear sets of numbers, and symport/antiport P systems with threshold assumption (translated as ! multiplicity of objects) can solve SAT in polynomial time. Also, several open research problems are stated.application/pdfengAttribution-NonCommercial-NoDerivatives 4.0 Internacionalhttp://creativecommons.org/licenses/by-nc-nd/4.0/info:eu-repo/semantics/conferenceObjectinfo:eu-repo/semantics/openAccesshttps://idus.us.es/xmlui/handle/11441/33819