Hybrid networks of evolutionary processors are computationally complete

A hybrid network of evolutionary processors (an HNEP) consists of several language processors which are located in the nodes of a virtual graph and able to perform only one type of point mutations (insertion, deletion, substitution) on the words found in that node, according to some predefined rules. Each node is associated with an input and an output filter, defined by some random-context conditions. After applying in parallel a point mutation to all the words existing in every node, the new words which are able to pass the output filter of the respective node navigate simultaneously through the network and enter those nodes whose input filter they are able to pass. We show that even the so-called elementary HNEPs are computationally complete. In this case every node is able to perform only one instance of the specified operation: either an insertion, or a deletion, or a substitution of a certain symbol. We also prove that in the case of non-elementary networks, any recursively enumerable language over a common alphabet can be obtained with an HNEP whose underlying structure is a fixed graph depending on the common alphabet only.Received: 19 July 2004, Published online: 19 January 2005Erzsébet Csuhaj-Varjú: Work supported in part by a grant from the NATO Scientific Committee in Spain and the Hungarian Scientific Research Fund OTKA Grant No. T 042529Victor Mitrana: Work supported by the Centre of Excellence in Information Technology, Computer Science and Control, ICA1-CT-2000-70025, HUN-TING project, WP5.     

Synthesis,characterization and thermal analysis of Fe-doped boehmite nanofibres and nanosheets

It is important that one should have knowledge of the thermal stability of synthesized nanomaterials. In this research, thermal analyses of both dynamic and controlled rate thermal analysis (CRTA) combined with infrared emission spectroscopy have been used to determine the thermal stability of iron-doped boehmite. Iron-doped boehmite nanofibres with varying iron contents have been prepared at low temperature using hydrothermal treatment in the presence of non-ionic poly (ethylene oxide) surfactant. The TEM images show that the resulting nanostructures are predominantly nanofibres when Fe doping is less than 5%; in contrast, nanosheets are the dominant for 10% Fe-doped boehmite. No nanofibre was observed in the case of 20% Fe-doped boehmite, instead, nanotubes, nanosheets and iron-rich nanoparticles were formed. Both dynamic thermal analysis and CRTA show that Fe-doped boehmite nanomaterials dehydroxylate at higher temperatures than pure boehmite nanofibres. In general, the higher the doped Fe %, the higher the dehydroxylation temperature. The dehydroxylation temperature indicated in the infrared emission spectroscopy of doped boehmite nanomaterials is in harmony with those in other thermal analysis studies.     

The Chemical Background of Advanced Oxidation Processes

In advanced oxidation processes, the hydroxyl radical is the main initiator of the degradation of pollutants. For aromatic molecules, the rate coefficients are between 2×10⁹ and 1×10¹⁰ mol⁻¹ dm³ s⁻¹ and show some variation according to the electron-withdrawing or donating nature of the substituents. The one-electron oxidant ^.OH induces 2–4 electron oxidations of many aromatic pollutants. These high rates are explained by ^.OH addition to an unsaturated bond, scavenging of the organic radical by dissolved O₂, and subsequent reactions. In amino-substituted molecules and in azo dyes the efficiency is lower, because O₂ cannot compete efficiently with the unimolecular transformation of carbon-centered radicals. Generally, the toxicity first increases and then decreases with treatment time. The increase is attributed to the high toxicity of some degradation products and to H₂O₂ formation. In surface waters, traces of transition metal ions degrade some of the H₂O₂ in Fenton-like processes.     

Mercury content of some wild edible mushrooms

 The mercury (Hg) content of 112 samples of common, wild edible mushrooms was analysed by atomic absorption spectrometry. The average Hg content of all the samples was 1.72 mg/kg dry mass (DM) but the Hg concentrations found in different taxonomic groups (genera and species varied) remarkably. Although different sampling locations obviously have an effect on the Hg concentration of sporocarps, we found evidence for a Hg-accumulating capacity of some taxonomic groups. In addition to Agaricus and Macrolepiota, where the phenomenon of mercury accumulation has already been described, our results indicate high Hg levels in samples of Lycoperdon perlatum (average 2.94 mg/kg DM) and in Lepista species (average 3.02 mg/kg DM). These data confirm the need for greater attention to be given to Hg levels in wild common mushrooms, especially to Hg-accumulating species. Received: 20 February 1997     

From Watson-Crick L systems to Darwinian P systems

Watson-Crick L systems are language generating devices making use ofWatson-Crick complementarity, a fundamental concept of DNA computing.These devices are Lindenmayer systems enriched with a trigger forcomplementarity transition: if a ``bad' string is obtained, then thederivation continues with its complement which is always a ``good'string. Membrane systems or P systems are distributed parallel computingmodels which were abstracted from the structure and the way offunctioning of living cells. In this paper, we first interpret theresults known about the computational completeness of Watson-Crick E0Lsystems in terms of membrane systems, then we introduce a related way ofcontrolling the evolution in P systems, by using the triggers not in theoperational manner (i.e., turning to the complement in a ``bad'configuration), but in a ``Darwinian' sense: if a ``bad' configurationis reached, then the system ``dies', that is, no result is obtained.The triggers (actually, the checkers) are given as finite state multisetautomata. We investigate the computational power of these P systems.Their computational completeness is proved, even for systems withnon-cooperative rules, working in the non-synchronized way, andcontrolled by only two finite state checkers; if the systems work in thesynchronized mode, then one checker for each system suffices to obtainthe computational completeness.     

Hyper-Spectral Satellite Images: Interval Methods May Be Helpful

Reliable Computing -     

Lewis acid initiated melt reactions of polystyrene and EPDM rubber

Summary In order to obtain high impact polystyrene (PS), experiments have been performed on coupling of EPDM rubber and PS in the mixing chamber of a HAAKE plastograph. Lewis acids were added to the melt and the torque increase observed by their addition proved that chemical reactions take place in the system. During the reaction, the rubber proved to be more active, it became crosslinked and/or it was coupled with the PS molecules. Only a small fraction of the PS present coupled to the rubber molecules. No significant degradation process could be detected. Mechanical properties (tensile modulus and strength) improved during the reaction. This can be interpreted by the increased solubility of the coupled rubber molecules in the continuous PS phase.