Frequency Membrane Systems

We define a model of membrane system where each membrane is clocked independently from the others, in the sense that every derivation step is applied without a global synchronization. The computation is obtained by the execution of a limited amount of rules in each membrane, and only when they are allowed to execute a derivation step. Indeed, each membrane operates with a certain work frequency that can change across the system. Simple results show that this model is at least as powerful as the usual one, and the goal is to present a few examples that show it giving rise to interesting dynamic behaviors

On the Computational Power of Spiking Neural P Systems

In this paper we study some computational properties of spiking neural P systems. In particular, we show that by using nondeterminism in a slightly extended version of spiking neural P systems it is possible to solve in constant time both the numerical NP-complete problem Subset Sum and the strongly NP-complete problem 3-SAT. Then, we show how to simulate a universal deterministic spiking neural P system with a deterministic Turing machine, in a time which is polynomial with respect to the execution time of the simulated system. Surprisingly, it turns out that the simulation can be performed in polynomial time with respect to the size of the description of the simulated system only if the regular expressions used in such a system are of a very restricted type

On three variants of rewriting P systems

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On the Computational Efficiency of Polarizationless Recognizer P Systems with Strong Division and Dissolution

Recognizer P systems with active membranes have proven to be very powerful computing devices, being able to solve NP-complete decision problems in a polynomial time. However such solutions usually exploit many powerful features, such as electrical charges (polarizations) associated to membranes, evolution rules, communication rules, and strong or weak forms of division rules. In this paper we contribute to the study of the computational power of polarizationless recognizer P systems with active membranes. Precisely, we show that such systems are able to solve in polynomial time the NP-complete decision problem 3-sat by using only dissolution rules and a form of strong division for non–elementary membranes, working in the maximal parallel way

Complexity aspects of polarizationless membrane systems

We investigate polarizationless P systems with active membranes working in maximally parallel manner, which do not make use of evolution or communication rules, in order to find which features are sufficient to efficiently solve computationally hard problems. We show that such systems are able to solve the PSPACE-complete problem QUANTIFIED 3-SAT, provided that non-elementary membrane division is controlled by the presence of a (possibly non-elementary) membrane.Ministerio de Educación y Ciencia TIN2006-13425Junta de Andalucía TIC-58

Severe bloodstream infection due to KPC-producer e coli in a renal transplant recipient treated with the double-carbapenem regimen and analysis of in vitro synergy testing a case report

Transplant recipients are at high risk of infections caused by multidrug resistant microorganisms. Due to the limited thera- peutic options, innovative antimicrobial combinations against carbape- nem-resistant Enterobacteriaceae causing severe infections are necessary. A 61-year-old woman with a history of congenital solitary kidney underwent renal transplantation. The postoperative course was compli- cated by nosocomial pneumonia due to Stenotrophomonas maltophilia and pan-sensitive Escherichia coli, successfully treated with antimicrobial therapy. On postoperative day 22, diagnosis of surgical site infection and nosocomial pneumonia with concomitant bacteremia due to a Kle- bisella pneumoniae carbapenemase-producer E coli was made. The patient was treated with the double-carbapenem regimen (high dose of merope- nem plus ertapenem) and a potent synergistic and bactericidal activity of this un-conventional therapeutic strategy was observed in vitro. Despite a microbiological response with prompt negativity of blood cultures, the patient faced a worse outcome because of severe hemorrhagic shock. The double-carbapenem regimen might be considered as a rescue therapy in those subjects, including transplant recipients, in whom previous antimicrobial combinations failed or when colistin use might be discouraged. Performing in vitro synergy testing should be strongly encouraged in cases of infections caused by pan-drug resistant strains, especially in high-risk patients

Online monitoring for proton therapy: A real-time procedure using a planar PET system

In this study a procedure for range verification in proton therapy by means of a planar in-beam PET system is presented. The procedure consists of two steps: the measurement of the β+-activity induced in the irradiated body by the proton beam and the comparison of these distributions with simulations. The experimental data taking was performed at the CNAO center in Pavia, Italy, irradiating plastic phantoms. For two different cases we demonstrate how a real-time feedback of the delivered treatment plan can be obtained with in-beam PET imaging