From cells to computers: computing with membranes (P systems).

The aim of this paper is to introduce to the reader the main ideas of computing with membranes, a recent branch of (theoretical) molecular computing. In short, in a cell-like system, multisets of objects evolve according to given rules in the compartments defined by a membrane structure and compute natural numbers as the result of halting sequences of transitions. The model is parallel, nondeterministic. Many variants have already been considered and many problems about them were investigated. We present here some of these variants, focusing on two central classes of results: (1) characterizations of the recursively enumerable sets of numbers and (2) possibilities to solve NP-complete problems in polynomial--even linear--time (of course, by making use of an exponential space). The results are given without proofs. An almost complete bibliography of the domain, at the middle of October 2000, is also provided.

New computing paradigms suggested by DNA computing: computing by carving.

Inspired by the experiments in the emerging area of DNA computing, a somewhat unusual type of computation strategy was recently proposed by one of us: to generate a (large) set of candidate solutions of a problem, then remove the non-solutions such that what remains is the set of solutions. This has been called a computation by carving. This idea leads both to a speculation with possible important consequences--computing non-recursively enumerable languages--and to interesting theoretical computer science (formal language) questions.

Bidirectional sticker systems.

We introduce two-sided sticker systems, the two-sided variant of a computability model introduced as an abstraction of Adleman's style of DNA computing and of the matching of the so-called Watson-Crick complements. Several types of sticker systems are shown to have the same power as regular grammars, one variant is found to represent the linear languages, and another one is proved to be able to represent any recursively enumerable language. From this result we infer that any recursively enumerable language can be represented as the projection of the intersection of two minimal linear languages.

[The prevalence of respiratory symptoms, bronchial asthma and chronic bronchitis (simple and obstructive) in a representative sample of the adult rural population]. / Prevalenta unor simptome respiratorii, a astmului bronsic si a bronsitei cronice (simple si obstructive) într-un esantion reprezentativ pentru o populatie adulta rurala.

A representative sample of an adult population living in a rural area (1001 adult subjects aged 18 and above) was submitted to the ECHRS standardised questionnaire (administrated by interview) and performed lung function tests (ventilatory). The most frequent respiratory symptoms were chronic cough (especially in males and smokers) and intermittent dyspnoea (in females more prevalent than in males). All symptoms showed a higher frequency after 50 years. Obstructive ventilatory impairment was found in 12.29% of the subjects, more frequently in males, ex-smokers and above 50 years of age. The prevalence of asthma bronchiale was 4.09%; the subjects over 40 years of age, the non-smokers and the females showed higher figures. Chronic simple bronchitis was found in 5.69% of examined subjects, especially in males and smokers. The prevalence of chronic obstructive bronchitis was as high as 2.29%, more prevalent in males, smokers, over 40 years. The prevalence rates found in this study are higher than those observed in a rural population living in an unpolluted area: this fact may be ascribed to the noxious effect of the air pollution due to the chemical industrial plants situated in the vicinity of the studied population.

Eco-grammar systems: a grammatical framework for studying lifelike interactions.

A formal framework for studying systems made up of a community of agents and their environment is proposed. The suggested model, technically based on the theory of formal grammars and called an eco-grammar system, captures some common features of ecological, economic, social, and collective robotic systems. The article contains an informal presentation as well as the formal definition of the model, presents some properties of variants of eco-grammar systems, and discusses the emergence of important lifelike features such as birth and death. Emphasis is put on results with relevance for artificial life. Some recent developments are also briefly reported.

[The prevalence of bronchial asthma, chronic bronchitis and COBP in representative samples of the adult population]. / Prevalenta astmului bronsic, a bronsitei cronice si a BPOC pe esantioane reprezentative de populatie adulta.

In order to organize the management of asthma bronchiale and chronic bronchitis, in our country, it is compulsory to know the prevalence of these diseases in the autochthonous population. The ECRHS questionnaire (by interview) and lung function tests were applied in three random population samples aged by 18 years and over. The samples were selected from the electoral rolls and coming from three different economic and geographic regions of our country. The questionnaire were administered by trained pneumologists and lung function testing by well trained technicians. The results were stored and processed on computer using the EPI INFO program. The prevalence of asthma bronchiale was: 4.09%, 6.60%, 1.70%. The prevalence of chronic bronchitis was: 12.28%, 10.11%, 7.98%. The prevalence of chronic obstructive bronchitis was: 1.79%, 2.50%, 1.89%. Generally, the prevalence of asthma bronchiale was found close to the values obtained in other studies, of identical conditions. It was particularly close to the results of Italian researchers who studied a population aged by 20 years and over from the northern Italy. The prevalence of chronic bronchitis was near by the value mentioned by Scandinavian epidemiologists. Analytic epidemiology would specify the causes of the variations we founded in the three studied samples.

DNA computing based on splicing: universality results.

The paper extends some of the most recently obtained results on the computational universality of specific variants of H systems (e.g. with regular sets of rules) and proves that we can construct universal computers based on various types of H systems with a finite set of splicing rules as well as a finite set of axioms, i.e. we show the theoretical possibility to design programmable universal DNA computers based on the splicing operation. For H systems working in the multiset style (where the numbers of copies of all available strings are counted) we elaborate how a Turing machine computing a partial recursive function can be simulated by an equivalent H system computing the same function; in that way, from a universal Turning machine we obtain a universal H system. Considering H systems as language generating devices we have to add various simple control mechanisms (checking the presence/absence of certain symbols in the spliced strings) to systems with a finite set of splicing rules as well as with a finite set of axioms in order to obtain the full computational power, i.e. to get a characterization of the family of recursively enumerable languages. We also introduce test tube systems, where several H systems work in parallel in their tubes and from time to time the contents of each tube are redistributed to all tubes according to certain separation conditions. By the construction of universal test tube systems we show that also such systems could serve as the theoretical basis for the development of biological (DNA) computers.